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Sample records for 2d growth mode

  1. New insights into the generalized Rutherford equation for nonlinear neoclassical tearing mode growth from 2D reduced MHD simulations

    NASA Astrophysics Data System (ADS)

    Westerhof, E.; de Blank, H. J.; Pratt, J.

    2016-03-01

    Two dimensional reduced MHD simulations of neoclassical tearing mode growth and suppression by ECCD are performed. The perturbation of the bootstrap current density and the EC drive current density perturbation are assumed to be functions of the perturbed flux surfaces. In the case of ECCD, this implies that the applied power is flux surface averaged to obtain the EC driven current density distribution. The results are consistent with predictions from the generalized Rutherford equation using common expressions for Δ \\text{bs}\\prime and Δ \\text{ECCD}\\prime . These expressions are commonly perceived to describe only the effect on the tearing mode growth of the helical component of the respective current perturbation acting through the modification of Ohm’s law. Our results show that they describe in addition the effect of the poloidally averaged current density perturbation which acts through modification of the tearing mode stability index. Except for modulated ECCD, the largest contribution to the mode growth comes from this poloidally averaged current density perturbation.

  2. 2D constant-loss taper for mode conversion

    NASA Astrophysics Data System (ADS)

    Horth, Alexandre; Kashyap, Raman; Quitoriano, Nathaniel J.

    2015-03-01

    Proposed in this manuscript is a novel taper geometry, the constant-loss taper (CLT). This geometry is derived with 1D slabs of silicon embedded in silicon dioxide using coupled-mode theory (CMT). The efficiency of the CLT is compared to both linear and parabolic tapers using CMT and 2D finite-difference time-domain simulations. It is shown that over a short 2D, 4.45 μm long taper the CLT's mode conversion efficiency is ~90% which is 10% and 18% more efficient than a 2D parabolic or linear taper, respectively.

  3. Growth and Characterization of Silicon at the 2D Limit

    NASA Astrophysics Data System (ADS)

    Mannix, Andrew; Kiraly, Brian; Hersam, Mark; Guisinger, Nathan

    2015-03-01

    Because bulk silicon has dominated the development of microelectronics over the past 50 years, the recent interest in two-dimensional (2D) materials (e.g., graphene, MoS2, phosphorene, etc.) naturally raises questions regarding the growth and properties of silicon at the 2D limit. Utilizing atomic-scale, ultra-high vacuum (UHV) scanning tunneling microscopy (STM), we have investigated the 2D limits of silicon growth on Ag(111). In agreement with previous reports of sp2-bonded silicene phases, we observe the temperature-dependent evolution of ordered 2D phases. However, we attribute these to apparent Ag-Si surface alloys. At sufficiently high silicon coverage, we observe the precipitation of crystalline, sp3-bonded Si(111) domains. These domains are capped with a √3 honeycomb phase that is indistinguishable from the silver-induced √3 honeycomb-chained-trimer reconstruction on bulk Si(111). Further ex-situcharacterization with Raman spectroscopy, atomic force microscopy, cross-sectional transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy reveals that these sheets are ultrathin sheets of bulk-like, (111) oriented, sp3 silicon. Even at the 2D limit, scanning tunneling spectroscopy shows that these silicon nanosheets exhibit semiconducting electronic characteristics.

  4. Simulation of the flow and mass transfer for KDP crystals undergoing 2D translation during growth

    NASA Astrophysics Data System (ADS)

    Zhou, Chuan; Li, Mingwei; Hu, Zhitao; Yin, Huawei; Wang, Bangguo; Cui, Qidong

    2016-09-01

    In this study, a novel motion mode for crystals during growth, i.e., 2D translation, is proposed. Numerical simulations of flow and mass transfer are conducted for the growth of large-scale potassium dihydrogen phosphate (KDP) crystals subjected to the new motion mode. Surface supersaturation and shear stress are obtained as functions of the translational velocity, distance, size, orientation of crystals. The dependence of these two parameters on the flow fields around the crystals is also discussed. The thicknesses of the solute boundary layer varied with translational velocity are described. The characteristics of solution flow and surface supersaturation distribution are summarized, where it suggests that the morphological stability of a crystal surface can be enhanced if the proposed 2D translation is applied to crystal growth.

  5. A scanning-mode 2D shear wave imaging (s2D-SWI) system for ultrasound elastography.

    PubMed

    Qiu, Weibao; Wang, Congzhi; Li, Yongchuan; Zhou, Juan; Yang, Ge; Xiao, Yang; Feng, Ge; Jin, Qiaofeng; Mu, Peitian; Qian, Ming; Zheng, Hairong

    2015-09-01

    Ultrasound elastography is widely used for the non-invasive measurement of tissue elasticity properties. Shear wave imaging (SWI) is a quantitative method for assessing tissue stiffness. SWI has been demonstrated to be less operator dependent than quasi-static elastography, and has the ability to acquire quantitative elasticity information in contrast with acoustic radiation force impulse (ARFI) imaging. However, traditional SWI implementations cannot acquire two dimensional (2D) quantitative images of the tissue elasticity distribution. This study proposes and evaluates a scanning-mode 2D SWI (s2D-SWI) system. The hardware and image processing algorithms are presented in detail. Programmable devices are used to support flexible control of the system and the image processing algorithms. An analytic signal based cross-correlation method and a Radon transformation based shear wave speed determination method are proposed, which can be implemented using parallel computation. Imaging of tissue mimicking phantoms, and in vitro, and in vivo imaging test are conducted to demonstrate the performance of the proposed system. The s2D-SWI system represents a new choice for the quantitative mapping of tissue elasticity, and has great potential for implementation in commercial ultrasound scanners. PMID:26025508

  6. THz quantum cascade lasers operating on the radiative modes of a 2D photonic crystal.

    PubMed

    Halioua, Y; Xu, G; Moumdji, S; Li, L H; Davies, A G; Linfield, E H; Colombelli, R

    2014-07-01

    Photonic-crystal lasers operating on Γ-point band-edge states of a photonic structure naturally exploit the so-called "nonradiative" modes. As the surface output coupling efficiency of these modes is low, they have relatively high Q factors, which favor lasing. We propose a new 2D photonic-crystal design that is capable of reversing this mode competition and achieving lasing on the radiative modes instead. Previously, this has only been shown in 1D structures, where the central idea is to introduce anisotropy into the system, both at unit-cell and resonator scales. By applying this concept to 2D photonic-crystal patterned terahertz frequency quantum cascade lasers, surface-emitting devices with diffraction-limited beams are demonstrated, with 17 mW peak output power. PMID:24978782

  7. Dual-mode operation of 2D material-base hot electron transistors

    PubMed Central

    Lan, Yann-Wen; Torres, Jr., Carlos M.; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  8. Dual-mode operation of 2D material-base hot electron transistors.

    PubMed

    Lan, Yann-Wen; Torres, Carlos M; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R; Lerner, Mitchell B; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  9. Fracture mode analysis and related surface deformation during dyke intrusion: Results from 2D experimental modelling

    NASA Astrophysics Data System (ADS)

    Abdelmalak, M.; Mourgues, R.; Bureau, D.

    2012-04-01

    The analysis of surface deformation in response to approaching intrusion is important for assessing volcanic hazards. In this paper, we present results from 2D scaled models of magma intrusion, in which we discuss the propagation mode and related surface deformation during dyke growth. Our experiments consist in the injection of analogue magma (Golden syrup) into cohesive fine-grained silica powder, simulating the brittle upper crust. Using an optical image correlation technique (Particle Imaging Velocimetry), we were able to follow the surface deformation, the displacements within the country rock and to calculate strains induced by the magma emplacement. We identified two kinds of intrusion morphologies resulting from different interactions between the dyke and plastic deformations occurring in the country rock near the surface. In both morphologies, the dyke is vertical at depth. Our analysis demonstrates that both hydraulic tensile opening and shear-related propagation operate during this first stage of vertical growth. At the same time, the surface lifted up and formed a smooth symmetrical dome. Both types of morphologies differ in the upper part. During a second stage of evolution, the first type of intrusion inclined at a dip between 45 to 65°. This inclination is not caused by shear deformations and is attributed to stress rotation near the tip. Closer to the surface, the growth of the inclined sheet creates shear bands which conduct the fluid toward the surface. The surface uplift becomes asymmetric. The second type of intrusion does not rotate at depth and continues its vertical propagation by catching vertical tensile cracks. The intrusion of magma in these cracks creates horizontal stresses which are responsible for the closure of fractures and the formation of reverse faults. At the surface the dome remains symmetrical. For both intrusions, the surface uplift accelerates during the second stage and it is strongly influenced by the presence or the

  10. XAFS data acquisition with 2D-detectors: Transmission mode XAFS and grazing incidence EXAFS spectroscopy

    NASA Astrophysics Data System (ADS)

    Lützenkirchen-Hecht, D.; Gasse, J.-C.; Bögel, R.; Wagner, R.; Frahm, R.

    2016-05-01

    XAFS-experiments in transmission and reflection modes have been performed using a Pilatus 100K pixel detector. Transmission mode XAFS spectra from a Co metal foil and Co3O4 were recorded to evaluate the data quality offered by this 2D-detector. Furthermore, the pixel detector was also used to measure reflection mode grazing incidence EXAFS data. Using different regions of interest in the collected scattering patterns, we will show that the diffuse scattering can be separated for the different contributing surfaces and interfaces, allowing simultaneous investigations of surfaces and buried interfaces within multi-layered samples.

  11. Growth rates and water stability of 2D boronate ester covalent organic frameworks.

    PubMed

    Smith, Brian J; Hwang, Nicky; Chavez, Anton D; Novotney, Jennifer L; Dichtel, William R

    2015-05-01

    We examine the growth rates, activation energies, and hydrolytic stability of multiple 2D boronate ester covalent organic frameworks by turbidity measurements, observing a 200-fold range in stability. The rate-determining step in boronate ester 2D COF growth is not in-solution condensation, but rather interlayer polymer stacking through a nucleation-elongation process. PMID:25848654

  12. Imaging collective magnonic modes in 2D arrays of magnetic nanoelements.

    PubMed

    Kruglyak, V V; Keatley, P S; Neudert, A; Hicken, R J; Childress, J R; Katine, J A

    2010-01-15

    We have used time resolved scanning Kerr microscopy to image collective spin wave modes within a 2D array of magnetic nanoelements. Long wavelength spin waves are confined within the array as if it was a continuous element of the same size but with effective material properties determined by the structure of the array and its constituent nanoelements. The array is an example of a magnonic metamaterial, the demonstration of which provides new opportunities within the emerging field of magnonics. PMID:20366622

  13. Imaging Collective Magnonic Modes in 2D Arrays of Magnetic Nanoelements

    NASA Astrophysics Data System (ADS)

    Kruglyak, V. V.; Keatley, P. S.; Neudert, A.; Hicken, R. J.; Childress, J. R.; Katine, J. A.

    2010-01-01

    We have used time resolved scanning Kerr microscopy to image collective spin wave modes within a 2D array of magnetic nanoelements. Long wavelength spin waves are confined within the array as if it was a continuous element of the same size but with effective material properties determined by the structure of the array and its constituent nanoelements. The array is an example of a magnonic metamaterial, the demonstration of which provides new opportunities within the emerging field of magnonics.

  14. Well-posedness and generalized plane waves simulations of a 2D mode conversion model

    NASA Astrophysics Data System (ADS)

    Imbert-Gérard, Lise-Marie

    2015-12-01

    Certain types of electro-magnetic waves propagating in a plasma can undergo a mode conversion process. In magnetic confinement fusion, this phenomenon is very useful to heat the plasma, since it permits to transfer the heat at or near the plasma center. This work focuses on a mathematical model of wave propagation around the mode conversion region, from both theoretical and numerical points of view. It aims at developing, for a well-posed equation, specific basis functions to study a wave mode conversion process. These basis functions, called generalized plane waves, are intrinsically based on variable coefficients. As such, they are particularly adapted to the mode conversion problem. The design of generalized plane waves for the proposed model is described in detail. Their implementation within a discontinuous Galerkin method then provides numerical simulations of the process. These first 2D simulations for this model agree with qualitative aspects studied in previous works.

  15. Automatic computation of 2D cardiac measurements from B-mode echocardiography

    NASA Astrophysics Data System (ADS)

    Park, JinHyeong; Feng, Shaolei; Zhou, S. Kevin

    2012-03-01

    We propose a robust and fully automatic algorithm which computes the 2D echocardiography measurements recommended by America Society of Echocardiography. The algorithm employs knowledge-based imaging technologies which can learn the expert's knowledge from the training images and expert's annotation. Based on the models constructed from the learning stage, the algorithm searches initial location of the landmark points for the measurements by utilizing heart structure of left ventricle including mitral valve aortic valve. It employs the pseudo anatomic M-mode image generated by accumulating the line images in 2D parasternal long axis view along the time to refine the measurement landmark points. The experiment results with large volume of data show that the algorithm runs fast and is robust comparable to expert.

  16. Growth of 2D black phosphorus film from chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Smith, Joshua B.; Hagaman, Daniel; Ji, Hai-Feng

    2016-05-01

    Phosphorene, a novel 2D material isolated from bulk black phosphorus (BP), is an intrinsic p-type material with a variable bandgap for a variety of applications. However, these applications are limited by the inability to isolate large films of phosphorene. Here we present an in situ chemical vapor deposition type approach that demonstrates progress towards growth of large area 2D BP with average areas >3 μm2 and thicknesses representing samples around four layers and thicker samples with average areas >100 μm2. Transmission electron microscopy and Raman spectroscopy have confirmed successful growth of 2D BP from red phosphorus.

  17. Growth of 2D black phosphorus film from chemical vapor deposition.

    PubMed

    Smith, Joshua B; Hagaman, Daniel; Ji, Hai-Feng

    2016-05-27

    Phosphorene, a novel 2D material isolated from bulk black phosphorus (BP), is an intrinsic p-type material with a variable bandgap for a variety of applications. However, these applications are limited by the inability to isolate large films of phosphorene. Here we present an in situ chemical vapor deposition type approach that demonstrates progress towards growth of large area 2D BP with average areas >3 μm2 and thicknesses representing samples around four layers and thicker samples with average areas >100 μm2. Transmission electron microscopy and Raman spectroscopy have confirmed successful growth of 2D BP from red phosphorus. PMID:27087456

  18. List-Mode Likelihood: EM Algorithm and Image Quality Estimation Demonstrated on 2-D PET

    PubMed Central

    Barrett, Harrison H.

    2010-01-01

    Using a theory of list-mode maximum-likelihood (ML) source reconstruction presented recently by Barrett et al. [1], this paper formulates a corresponding expectation-maximization (EM) algorithm, as well as a method for estimating noise properties at the ML estimate. List-mode ML is of interest in cases where the dimensionality of the measurement space impedes a binning of the measurement data. It can be advantageous in cases where a better forward model can be obtained by including more measurement coordinates provided by a given detector. Different figures of merit for the detector performance can be computed from the Fisher information matrix (FIM). This paper uses the observed FIM, which requires a single data set, thus, avoiding costly ensemble statistics. The proposed techniques are demonstrated for an idealized two-dimensional (2-D) positron emission tomography (PET) [2-D PET] detector. We compute from simulation data the improved image quality obtained by including the time of flight of the coincident quanta. PMID:9688154

  19. Modeling the Effect of Multiple Matrix Cracking Modes on Cyclic Hysteresis Loops of 2D Woven Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-08-01

    In this paper, the effect of multiple matrix cracking modes on cyclic loading/unloading hysteresis loops of 2D woven ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in longitudinal yarns, are considered as the major reason for hysteresis loops of 2D woven CMCs. The effects of fiber volume content, peak stress, matrix crack spacing, interface properties, matrix cracking mode proportion and interface wear on interface slip and hysteresis loops have been analyzed. The cyclic loading/unloading hysteresis loops of 2D woven SiC/SiC composite corresponding to different peak stresses have been predicted using the present analysis. It was found that the damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire cracking modes of the composite, increases with increasing peak stress.

  20. Modeling the Effect of Multiple Matrix Cracking Modes on Cyclic Hysteresis Loops of 2D Woven Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-02-01

    In this paper, the effect of multiple matrix cracking modes on cyclic loading/unloading hysteresis loops of 2D woven ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in longitudinal yarns, are considered as the major reason for hysteresis loops of 2D woven CMCs. The effects of fiber volume content, peak stress, matrix crack spacing, interface properties, matrix cracking mode proportion and interface wear on interface slip and hysteresis loops have been analyzed. The cyclic loading/unloading hysteresis loops of 2D woven SiC/SiC composite corresponding to different peak stresses have been predicted using the present analysis. It was found that the damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire cracking modes of the composite, increases with increasing peak stress.

  1. Multi-level single mode 2D polymer waveguide optical interconnects using nano-imprint lithography.

    PubMed

    Khan, Muhammad Umar; Justice, John; Petäjä, Jarno; Korhonen, Tia; Boersma, Arjen; Wiegersma, Sjoukje; Karppinen, Mikko; Corbett, Brian

    2015-06-01

    Single and multi-layer passive optical interconnects using single mode polymer waveguides are demonstrated using UV nano-imprint lithography. The fabrication tolerances associated with imprint lithography are investigated and we show a way to experimentally quantify a small variation in index contrast between core and cladding of fabricated devices. 1x2 splitting devices based on directional couplers and multimode interference interferometers are demonstrated to have less than 0.45 dB insertion loss with 0.02 ± 0.01 dB power imbalance between the outputs. We demonstrate an 'optical via' with an insertion loss less than 0.45 dB to transfer light from one optical signal plane to another. A 1x4 two-dimensional optical port is experimentally demonstrated to spatially split the input power with an insertion loss of 1.2 dB. PMID:26072823

  2. Comparison of Failure Modes in 2-D and 3-D Woven Carbon Phenolic Systems

    NASA Technical Reports Server (NTRS)

    Rossman, Grant A.; Stackpoole, Mairead; Feldman, Jay; Venkatapathy, Ethiraj; Braun, Robert D.

    2013-01-01

    NASA Ames Research Center is developing Woven Thermal Protection System (WTPS) materials as a new class of heatshields for entry vehicles (Stackpoole). Currently, there are few options for ablative entry heatshield materials, none of which is ideally suited to the planetary probe missions currently of interest to NASA. While carbon phenolic was successfully used for the missions Pioneer Venus and Galileo (to Jupiter), the heritage constituents are no longer available. An alternate carbon phenolic would need to be qualified for probe missions, which is most efficient at heat fluxes greater than those currently of interest. Additional TPS materials such as Avcoat and PICA are not sufficiently robust for the heat fluxes required. As a result, there is a large TPS gap between the materials efficient at very high conditions (carbon phenolic) and those that are effective at low-moderate conditions (all others). Development of 3D Woven TPS is intended to fill this gap, targeting mid-density weaves that could with withstand mid-range heat fluxes between 1100 W/sq cm and 8000 W/sq cm (Venkatapathy (2012). Preliminary experimental studies have been performed to show the feasibility of WTPS as a future mid-range TPS material. One study performed in the mARC Jet Facility at NASA Ames Research Center characterized the performance of a 3D Woven TPS sample and compared it to 2D carbon phenolic samples at ply angles of 0deg, 23.5deg, and 90deg. Each sample contained similar compositions of phenolic and carbon fiber volume fractions for experimental consistency. The goal of this study was to compare the performance of the TPS materials by evaluating resulting recession and failure modes. After exposing both samples to similar heat flux and pressure conditions, the 2D carbon phenolic laminate was shown to experience significant delamination between layers and further pocketing underneath separated layers. The 3D Woven TPS sample did not experience the delamination or pocketing

  3. Filamentation as primitive growth mode?

    PubMed

    Bigan, Erwan; Steyaert, Jean-Marc; Douady, Stéphane

    2015-12-01

    Osmotic pressure influences cellular shape. In a growing cell, chemical reactions and dilution induce changes in osmolarity, which in turn influence the cellular shape. Using a protocell model relying upon random conservative chemical reaction networks with arbitrary stoichiometry, we find that when the membrane is so flexible that its shape adjusts itself quasi-instantaneously to balance the osmotic pressure, the protocell either grows filamentous or fails to grow. This behavior is consistent with a mathematical proof. This suggests that filamentation may be a primitive growth mode resulting from the simple physical property of balanced osmotic pressure. We also find that growth is favored if some chemical species are only present inside the protocell, but not in the outside growth medium. Such an insulation requires specific chemical schemes. Modern evolved cells such as E. coli meet these requirements through active transport mechanisms such as the phosphotransferase system. PMID:26718101

  4. Filamentation as primitive growth mode?

    NASA Astrophysics Data System (ADS)

    Bigan, Erwan; Steyaert, Jean-Marc; Douady, Stéphane

    2015-12-01

    Osmotic pressure influences cellular shape. In a growing cell, chemical reactions and dilution induce changes in osmolarity, which in turn influence the cellular shape. Using a protocell model relying upon random conservative chemical reaction networks with arbitrary stoichiometry, we find that when the membrane is so flexible that its shape adjusts itself quasi-instantaneously to balance the osmotic pressure, the protocell either grows filamentous or fails to grow. This behavior is consistent with a mathematical proof. This suggests that filamentation may be a primitive growth mode resulting from the simple physical property of balanced osmotic pressure. We also find that growth is favored if some chemical species are only present inside the protocell, but not in the outside growth medium. Such an insulation requires specific chemical schemes. Modern evolved cells such as E. coli meet these requirements through active transport mechanisms such as the phosphotransferase system.

  5. Focal plane readout for 2-D LWIR application implemented with current mode background suppression per pixel

    NASA Astrophysics Data System (ADS)

    Woo, Doo Hyung; Kang, Sang Gu; Lee, Hee Chul

    2004-02-01

    In this paper, a readout technique involving current mode background suppression is studied for 2-dimensional infrared focal plane arrays (IR FPA"s). This technique has a current memory per pixel, and the suppression current can be optimized per pixel element. Capacitive transimpedende amplifier (CTIA) and feedback amplifier structure are adopted for input circuit and background suppression circuit, respectively. Feedback amplifier structure can minimize skimming error due to channel length modulation. The area size of the pixel circuit is generally limited in the case of 2-D application. So, the amplifier used in the CTIA input circuit adopts timesharing for background suppression. To further improve the area limitation, a half circuit of the CTIA is shared in row circuit out of the pixel array. Because of the leakage of the current memory, the skimming data of the current memory in the pixel array is stored in SRAM array through ADC, and is refreshed periodically with SRAM data through DAC. The readout circuit was fabricated using 0.6um 2-poly 3-metal CMOS process for 64 x 64 LWIR HgCdTe IR array with the pixel size of 50um x 50um. The measurement performance of the skimming circuit exhibits about only 3% error for 100nA background current. The simulation results exhibit that skimming error can be reduced further to 0.3% when the ratioed current mirror scheme and/or multi step refresh scheme is adopted.

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

    SciTech Connect

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

    2014-10-19

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

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

    SciTech Connect

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

    2008-01-01

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

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

    DOE PAGESBeta

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

    2014-10-19

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

  9. Stacking sequence determines Raman intensities of observed interlayer shear modes in 2D layered materials - A general bond polarizability model

    NASA Astrophysics Data System (ADS)

    Luo, Xin; Lu, Xin; Cong, Chunxiao; Yu, Ting; Xiong, Qihua; Ying Quek, Su

    2015-10-01

    2D layered materials have recently attracted tremendous interest due to their fascinating properties and potential applications. The interlayer interactions are much weaker than the intralayer bonds, allowing the as-synthesized materials to exhibit different stacking sequences, leading to different physical properties. Here, we show that regardless of the space group of the 2D materials, the Raman frequencies of the interlayer shear modes observed under the typical configuration blue shift for AB stacked materials, and red shift for ABC stacked materials, as the number of layers increases. Our predictions are made using an intuitive bond polarizability model which shows that stacking sequence plays a key role in determining which interlayer shear modes lead to the largest change in polarizability (Raman intensity); the modes with the largest Raman intensity determining the frequency trends. We present direct evidence for these conclusions by studying the Raman modes in few layer graphene, MoS2, MoSe2, WSe2 and Bi2Se3, using both first principles calculations and Raman spectroscopy. This study sheds light on the influence of stacking sequence on the Raman intensities of intrinsic interlayer modes in 2D layered materials in general, and leads to a practical way of identifying the stacking sequence in these materials.

  10. Parameterising root system growth models using 2D neutron radiography images

    NASA Astrophysics Data System (ADS)

    Schnepf, Andrea; Felderer, Bernd; Vontobel, Peter; Leitner, Daniel

    2013-04-01

    Root architecture is a key factor for plant acquisition of water and nutrients from soil. In particular in view of a second green revolution where the below ground parts of agricultural crops are important, it is essential to characterise and quantify root architecture and its effect on plant resource acquisition. Mathematical models can help to understand the processes occurring in the soil-plant system, they can be used to quantify the effect of root and rhizosphere traits on resource acquisition and the response to environmental conditions. In order to do so, root architectural models are coupled with a model of water and solute transport in soil. However, dynamic root architectural models are difficult to parameterise. Novel imaging techniques such as x-ray computed tomography, neutron radiography and magnetic resonance imaging enable the in situ visualisation of plant root systems. Therefore, these images facilitate the parameterisation of dynamic root architecture models. These imaging techniques are capable of producing 3D or 2D images. Moreover, 2D images are also available in the form of hand drawings or from images of standard cameras. While full 3D imaging tools are still limited in resolutions, 2D techniques are a more accurate and less expensive option for observing roots in their environment. However, analysis of 2D images has additional difficulties compared to the 3D case, because of overlapping roots. We present a novel algorithm for the parameterisation of root system growth models based on 2D images of root system. The algorithm analyses dynamic image data. These are a series of 2D images of the root system at different points in time. Image data has already been adjusted for missing links and artefacts and segmentation was performed by applying a matched filter response. From this time series of binary 2D images, we parameterise the dynamic root architecture model in the following way: First, a morphological skeleton is derived from the binary

  11. REVIEW ARTICLE: Slow light modes for optical delay lines: 2D photonic crystal-based design structures, performances and challenges

    NASA Astrophysics Data System (ADS)

    Talneau, A.

    2010-10-01

    This paper presents an overview of 2D photonic crystal-based structures designed to display low group velocity as well as reduced group velocity dispersions. Their main envisioned applications are optical delay lines for telecom transmissions at 1.55 µm. Optical mechanisms responsible for slowing down the optical modes and encountered in the slow light regime serve as a guideline for this paper.

  12. J-integral evaluation for 2D mixed-mode crack problems employing a meshfree stabilized conforming nodal integration method

    NASA Astrophysics Data System (ADS)

    Tanaka, Satoyuki; Suzuki, Hirotaka; Sadamoto, Shota; Sannomaru, Shogo; Yu, Tiantang; Bui, Tinh Quoc

    2016-08-01

    Two-dimensional (2D) in-plane mixed-mode fracture mechanics problems are analyzed employing an efficient meshfree Galerkin method based on stabilized conforming nodal integration (SCNI). In this setting, the reproducing kernel function as meshfree interpolant is taken, while employing the SCNI for numerical integration of stiffness matrix in the Galerkin formulation. The strain components are smoothed and stabilized employing Gauss divergence theorem. The path-independent integral ( J-integral) is solved based on the nodal integration by summing the smoothed physical quantities and the segments of the contour integrals. In addition, mixed-mode stress intensity factors (SIFs) are extracted from the J-integral by decomposing the displacement and stress fields into symmetric and antisymmetric parts. The advantages and features of the present formulation and discretization in evaluation of the J-integral of in-plane 2D fracture problems are demonstrated through several representative numerical examples. The mixed-mode SIFs are evaluated and compared with reference solutions. The obtained results reveal high accuracy and good performance of the proposed meshfree method in the analysis of 2D fracture problems.

  13. Dispersion relations of externally and thermally excited dust lattice modes in 2D complex plasma crystals

    SciTech Connect

    Yang Xuefeng; Cui Jian; Zhang Yuan; Liu Yue

    2012-07-15

    The dispersion relations of the externally and thermally (naturally) excited dust lattice modes (both longitudinal and transverse) in two-dimensional Debye-Yukawa complex plasma crystals are investigated. The dispersion relations are calculated numerically by taking the neutral gas damping effects into account and the numerical results are in agreement with the experimental data given by Nunomura et al.[Phys. Rev. E 65, 066402 (2002)]. It is found that for the mode excited by an external disturbance with a real frequency, the dispersion properties are changed at a critical frequency near where the group velocity of the mode goes to zero. Therefore, the high frequency branch with negative dispersion cannot be reached. In contrast, for the thermally excited mode, the dispersion curve can extend all the way to the negative dispersion region, while a 'cut-off' wave number exists at the long wavelength end of the dispersion in the transverse mode.

  14. Neurite outgrowth at the interface of 2D and 3D growth environments

    NASA Astrophysics Data System (ADS)

    Kofron, Celinda M.; Fong, Vivian J.; Hoffman-Kim, Diane

    2009-02-01

    Growing neurons navigate complex environments, but in vitro systems for studying neuronal growth typically limit the cues to flat surfaces or a single type of cue, thereby limiting the resulting growth. Here we examined the growth of neurons presented with two-dimensional (2D) substrate-bound cues when these cues were presented in conjunction with a more complex three-dimensional (3D) architecture. Dorsal root ganglia (DRG) explants were cultured at the interface between a collagen I matrix and a glass coverslip. Laminin (LN) or chondroitin sulfate proteoglycans (CSPG) were uniformly coated on the surface of the glass coverslip or patterned in 50 µm tracks by microcontact printing. Quantitative analysis of neurite outgrowth with a novel grid system at multiple depths in the gel revealed several interesting trends. Most of the neurites extended at the surface of the gel when LN was presented whereas more neurites extended into the gel when CSPG was presented. Patterning of cues did not affect neurite density or depth of growth. However, neurite outgrowth near the surface of the gel aligned with LN patterns, and these extensions were significantly longer than neurites extended in other cultures. In interface cultures, DRG growth patterns varied with the type of cue where neurite density was higher in cultures presenting LN than in cultures presenting CSPG. These results represent an important step toward understanding how neurons integrate local structural and chemical cues to make net growth decisions.

  15. Super-radiant plasmon mode is more efficient for SERS than the sub-radiant mode in highly packed 2D gold nanocube arrays

    SciTech Connect

    Mahmoud, Mahmoud A.

    2015-08-21

    The field coupling in highly packed plasmonic nanoparticle arrays is not localized due to the energy transport via the sub-radiant plasmon modes, which is formed in addition to the regular super-radiant plasmon mode. Unlike the sub-radiant mode, the plasmon field of the super-radiant mode cannot extend over long distances since it decays radiatively with a shorter lifetime. The coupling of the plasmon fields of gold nanocubes (AuNCs) when organized into highly packed 2D arrays was examined experimentally. Multiple plasmon resonance optical peaks are observed for the AuNC arrays and are compared to those calculated using the discrete dipole approximation. The calculated electromagnetic plasmon fields of the arrays displayed high field intensity for the nanocubes located in the center of the arrays for the lower energy super-radiant mode, while the higher energy sub-radiant plasmon mode displayed high field intensity at the edges of the arrays. The Raman signal enhancement by the super-radiant plasmon mode was found to be one hundred fold greater than that by sub-radiant plasmon mode because the super-radiant mode has higher scattering and stronger plasmon field intensity relative to the sub-radiant mode.

  16. Quasinormal modes for single horizon black holes in generic 2D dilaton gravity

    NASA Astrophysics Data System (ADS)

    Kettner, Joanne; Kunstatter, Gabor; Medved, A. J. M.

    2004-12-01

    There has been some recent speculation that a connection may exist between the quasinormal-mode spectra of highly damped black holes and the fundamental theory of quantum gravity. This notion follows from a conjecture by Hod that the real part of the highly damped mode frequencies can be used to calibrate the semi-classical level spacing in the black-hole quantum area spectrum. However, even if the level spacing can be fixed in this manner, it still remains unclear whether this implies a physically significant 'duality' or merely a numerical coincidence. This tapestry of ideas serves as the motivation for the current paper. We utilize the 'monodromy approach' to calculate the quasinormal-mode spectra for a generic class of black holes in two-dimensional dilatonic gravity. Our results agree with the prior literature whenever a direct comparison is possible and provide the analysis of a much more diverse class of black-hole models than previously considered.

  17. Nonlinear regime of the mode-coupling instability in 2D plasma crystals

    NASA Astrophysics Data System (ADS)

    Röcker, T. B.; Couëdel, L.; Zhdanov, S. K.; Nosenko, V.; Ivlev, A. V.; Thomas, H. M.; Morfill, G. E.

    2014-05-01

    The transition between linear and nonlinear regimes of the mode-coupling instability (MCI) operating in a monolayer plasma crystal is studied. The mode coupling is triggered at the centre of the crystal and a melting front is formed, which travels through the crystal. At the nonlinear stage, the mode coupling results in synchronisation of the particle motion and the kinetic temperature of the particles grows exponentially. After melting of the crystalline structure, the mean kinetic energy of the particles continued to grow further, preventing recrystallisation of the melted phase. The anomalous kinetic temperature obtained in the experiments could not be reproduced in simulations employing a simple point-like wake model. This shows that at the nonlinear stage of the MCI a more careful analysis is necessary.

  18. Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene

    NASA Astrophysics Data System (ADS)

    Sun, Yi-Yang; Zhang, Shengbai

    2016-07-01

    Bulk black phosphorus has two optical phonon modes labeled as Ag2 and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag2 modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B2u-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.

  19. Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene.

    PubMed

    Sun, Yi-Yang; Zhang, Shengbai

    2016-07-14

    Bulk black phosphorus has two optical phonon modes labeled as Ag (2) and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag (2) modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B2u-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy. PMID:27421389

  20. In vivo application of 2-D lateral scanning mode optical coherence tomography for glucose sensing

    NASA Astrophysics Data System (ADS)

    Kuranov, Roman; Prough, Donald; Sapozhnikova, Veronika; Cicenaite, Inga; Esenaliev, Rinat

    2005-11-01

    Optical Coherence Tomography (OCT) was recently proposed by our group for noninvasive, continuous monitoring of blood glucose concentration in diabetics as well as in critically ill patients (both diabetic and nondiabetic). In our previous studies we tested OCT-based glucose sensing using one-dimensional (1-D) lateral scanning of the OCT probing beam over the tissue surface. The measured OCT signal was prone to motion artifacts and had high level of speckle noise. In this study we used two-dimensional (2-D) lateral scanning of the OCT probing beam and achieved 3.6-fold reduction of the speckle noise level. We also applied a post-processing Fourier filtration technique that resulted in an additional 2-2.5-fold suppression of noise. Our data indicate that the combination of acquisition time of 30-40s and the Fourier filtration technique may provide OCT monitoring of blood glucose concentration with a sensitivity of 1mM (18 mg/dL).

  1. Electromagnetic induction by finite wavenumber source fields in 2-D lateral heterogeneities - The transverse electric mode

    NASA Technical Reports Server (NTRS)

    Hermance, J. F.

    1984-01-01

    Electromagnetic induction in a laterally homogeneous earth is analyzed in terms of a source field with finite dimensions. Attention is focused on a time-varying two-dimensional current source directed parallel to the strike of a two-dimensional anomalous structure within the earth, i.e., the E-parallel mode. The spatially harmonic source field is expressed as discontinuities in the magnetic (or electric) field of the current in the source. The model is applied to describing the magnetic gradients across megatectonic features, and may be used to predict the magnetic fields encountered by a satellite orbiting above the ionosphere.

  2. Assessment of the spatial homogeneity of artery dimension parameters with high frame rate 2-D B-mode.

    PubMed

    Meinders, J M; Brands, P J; Willigers, J M; Kornet, L; Hoeks, A P

    2001-06-01

    To elicit vessel wall inhomogeneities in diameter and distension along an arterial segment, a 2-D vessel wall-tracking system based on fast B-mode has been developed. The frame rate of a 7.5-MHz linear-array transducer (length 36 mm) is enhanced by increasing the pulse-repetition frequency to 10 kHz, decreasing the number of echo lines per frame from 128 to 64, or increasing the interspacing between echo lines with a factor of two or four. Dedicated software has been developed to extract for each echo-line the end-diastolic diameter from the B-mode image and the 2-D distension waveform from the underlying radiofrequency (RF) information. The method is validated in tubes with various focal lesion sizes. Straight segments of presumably homogeneous common carotid arteries have also been tested. The temporal and spatial SD of diameter or distension reveals inhomogeneities in time or space (i.e., inhomogeneities in artery characteristics). The method can be implemented in echo systems supporting high frame rates and real-time processing of radiofrequency data. PMID:11516538

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

    PubMed Central

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

    2014-01-01

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

  4. 2D HYDRA Calculations of Magneto-Rayleigh-Taylor Growth and Feedthrough in Cylindrical Liners

    NASA Astrophysics Data System (ADS)

    Weis, Matthew; Zhang, Peng; Lau, Y. Y.; Gilgenbach, Ronald; Peterson, Kyle; Hess, Mark

    2014-10-01

    Cylindrical liner implosions are susceptible to the magneto-Rayleigh-Taylor instability (MRT), along with the azimuthal current-carrying modes (sausage, kink, etc). ``Feedthrough'' of these instabilities has a strong influence on the integrity of the liner/fuel interface in the magnetized liner inertial fusion concept (MagLIF). The linearized ideal MHD equations can be solved to quantify these effects, including the presence of an effective gravity and an axial magnetic field. We investigate the potential of this field to mitigate feedthrough, due to MRT growth from various initial surface finishes (seeded, rough), throughout the implosion using our analytic results and the LLNL code, HYDRA. We will present both low and high convergence cases. Lastly, we illustrate the effect shock compression can have on feedthrough in seeded liners for various fill gases (cold and pre-heated) and magnetic field configurations. M. R. Weis was supported by the Sandia National Laboratories.

  5. A hybrid wave-mode formulation for the vibro-acoustic analysis of 2D periodic structures

    NASA Astrophysics Data System (ADS)

    Droz, C.; Zhou, C.; Ichchou, M. N.; Lainé, J.-P.

    2016-02-01

    In the framework of vibrational analysis of 2D periodic waveguides, Floquet-Bloch theorem is widely applied for the determination of wave dispersion characteristics. In this context, the Wave Finite Element Method (WFEM) combines Periodic Structure Theory (PST) with standard FE packages, enabling wave dispersion analysis of waveguides involving structurally realistic unit-cells. For such applications, the computational efficiency of the WFEM depends on the choice of the formulation and can lead to numerical issues, worsen by extensive computational cost. This paper presents a coupled wave-mode approach for the determination of wave dispersion characteristics in structurally advanced periodic structures. It combines two scales of model order reduction. At the unit-cell's scale, Component Mode Synthesis (CMS) provides the displacement field associated with local resonances of the periodic structure, while the free wave propagation is considered using a spectral problem projection on a reduced set of shape functions associated with propagating waves, thus providing considerable reduction of the computational cost. An application is provided for a bi-directionally stiffened panel and the influence of reduction parameters is discussed, as well as the robustness of the numerical results.

  6. Growth Modes and Energetics of 101 Face Lysozyme Crystal Growth

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, L.

    2004-01-01

    From analyses of lysozyme 101 face growth rate data using a 2D nucleation model for layer-by-layer growth, we find the effective barrier for crystal growth to be gamma = 1.0 +/- 0.2 x 10(exp -13) erg/molecule. The magnitude of the effective barrier is 2.4 +/- 0.5 k(sub beta)T, at 22 C. We also find that beyond a critical solution supersaturation, sigma(sub c), crystal growth rates are more accurately described by a kinetic roughening hypothesis. Beyond sigma(sub c), crystals grow by the continuous addition of molecules anywhere on the crystal surface rather than layer-by-layer. The magnitude of the critical supersaturation (sigma(sub c), = 1.7 +/- 0.2) for a crossover from a layer-by-layer to continuous growth is found to be statistically independent of the solution conditions that vary with buffer pH, temperature or precipitant concentration. Using the experimentally determined values for gamma and sigma(sub c), we find the crystal growth unit to be comprised of 7 +/- 3 molecules. The energy barrier, E(sub c), for the continuous addition of the growth Units is 6.2 +/- 0.3 x 10(exp -13) erg/molecule or 15 +/1 1 k(sub beta)T at 22C.

  7. Transverse Strains in Muscle Fascicles during Voluntary Contraction: A 2D Frequency Decomposition of B-Mode Ultrasound Images

    PubMed Central

    Wakeling, James M.

    2014-01-01

    When skeletal muscle fibres shorten, they must increase in their transverse dimensions in order to maintain a constant volume. In pennate muscle, this transverse expansion results in the fibres rotating to greater pennation angle, with a consequent reduction in their contractile velocity in a process known as gearing. Understanding the nature and extent of this transverse expansion is necessary to understand the mechanisms driving the changes in internal geometry of whole muscles during contraction. Current methodologies allow the fascicle lengths, orientations, and curvatures to be quantified, but not the transverse expansion. The purpose of this study was to develop and validate techniques for quantifying transverse strain in skeletal muscle fascicles during contraction from B-mode ultrasound images. Images were acquired from the medial and lateral gastrocnemii during cyclic contractions, enhanced using multiscale vessel enhancement filtering and the spatial frequencies resolved using 2D discrete Fourier transforms. The frequency information was resolved into the fascicle orientations that were validated against manually digitized values. The transverse fascicle strains were calculated from their wavelengths within the images. These methods showed that the transverse strain increases while the longitudinal fascicle length decreases; however, the extent of these strains was smaller than expected. PMID:25328509

  8. Growth Kinematics of Opening-Mode Fractures

    NASA Astrophysics Data System (ADS)

    Eichhubl, P.; Alzayer, Y.; Laubach, S.; Fall, A.

    2014-12-01

    Fracture aperture is a primary control on flow in fractured reservoirs of low matrix permeability including unconventional oil and gas reservoirs and most geothermal systems. Guided by principles of linear elastic fracture mechanics, fracture aperture is generally assumed to be a linear function of fracture length and elastic material properties. Natural opening-mode fractures with significant preserved aperture are observed in core and outcrop indicative of fracture opening strain accommodated by permanent solution-precipitation creep. Fracture opening may thus be decoupled from length growth if the material effectively weakens after initial elastic fracture growth by either non-elastic deformation processes or changes in elastic properties. To investigate the kinematics of fracture length and aperture growth, we reconstructed the opening history of three opening-mode fractures that are bridged by crack-seal quartz cement in Travis Peak Sandstone of the SFOT-1 well, East Texas. Similar crack-seal cement bridges had been interpreted to form by repeated incremental fracture opening and subsequent precipitation of quartz cement. We imaged crack-seal cement textures for bridges sampled at varying distance from the tips using scanning electron microscope cathodoluminescence, and determined the number and thickness of crack-seal cement increments as a function of position along the fracture length and height. Observed trends in increment number and thickness are consistent with an initial stage of fast fracture propagation relative to aperture growth, followed by a stage of slow propagation and pronounced aperture growth. Consistent with fluid inclusion observations indicative of fracture opening and propagation occurring over 30-40 m.y., we interpret the second phase of pronounced aperture growth to result from fracture opening strain accommodated by solution-precipitation creep and concurrent slow, possibly subcritical, fracture propagation. Similar deformation

  9. The 2-D growth of gold on single-layer graphene/Ru(0001): Enhancement of CO adsorption

    SciTech Connect

    Liu, Li; Zhou, Zihao; Guo, Qinlin; Yan, Zhen; Yao, Yunxi; Goodman, D. Wayne

    2011-09-01

    The growth and morphology of two-dimensional (2-D) gold islands on a single-layer graphene supported on Ru(0001) have been studied by scanning tunneling microscopy (STM). Our findings show that gold exhibits 2-D structures up to a gold dosage of 0.75 equivalent monolayers, and that these 2-D gold islands are thermally stable at room temperature. Parallel polarization modulation infrared reflection absorption spectroscopic (PM-IRAS) and high resolution electron energy loss spectroscopic (HREELS) studies indicate that carbon monoxide (CO) adsorbs on these 2-D gold islands at 85 K, showing a characteristic CO stretching feature at 2095 cm-1 for a saturation coverage of CO. The red shift of the CO stretching frequency compared to that on charge neutral gold is consistent with electron transfer from graphene to gold, i.e., an electron-rich gold overlayer. Preliminary data obtained by dosing molecular oxygen onto this CO pre-covered surface suggest that the 2-D gold islands catalyze the oxidation of CO.

  10. The 2-D growth of gold on single-layer graphene/Ru(0001): Enhancement of CO adsorption

    NASA Astrophysics Data System (ADS)

    Liu, Li; Zhou, Zihao; Guo, Qinlin; Yan, Zhen; Yao, Yunxi; Goodman, D. Wayne

    2011-09-01

    The growth and morphology of two-dimensional (2-D) gold islands on a single-layer graphene supported on Ru(0001) have been studied by scanning tunneling microscopy (STM). Our findings show that gold exhibits 2-D structures up to a gold dosage of 0.75 equivalent monolayers, and that these 2-D gold islands are thermally stable at room temperature. Parallel polarization modulation infrared reflection absorption spectroscopic (PM-IRAS) and high resolution electron energy loss spectroscopic (HREELS) studies indicate that carbon monoxide (CO) adsorbs on these 2-D gold islands at 85 K, showing a characteristic CO stretching feature at 2095 cm - 1 for a saturation coverage of CO. The red shift of the CO stretching frequency compared to that on charge neutral gold is consistent with electron transfer from graphene to gold, i.e., an electron-rich gold overlayer. Preliminary data obtained by dosing molecular oxygen onto this CO pre-covered surface suggest that the 2-D gold islands catalyze the oxidation of CO.

  11. 2D Crystal heterostructures properties and growth by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Xing, Grace Huili

    Two-dimensional (2D) crystals such as transition metal dichalcogenides (TMDs) along with other families of layered materials including graphene, SnSe2, GaSe, BN etc, has attracted intense attention from the scientific community. One monolayer of such materials represent the thinnest ``quantum wells''. These layered materials typically possess an in-plane hexagonal crystal structure, and can be stacked together by interlayer van der Waals interactions. Therefore, it is possible to create novel heterostructures by stacking materials with large lattice mismatches and different properties, for instance, superconductors (NbSe2) , metals, semi-metals (graphene), semiconductors (MoS2) and insulators (BN). Numerous novel material properties and device concepts have been discovered, proposed and demonstrated lately. However, the low internal photoluminescence efficiency (IPE, <1%) and low carrier mobility observed in the 2D semiconductors suggest strongly that the materials under investigation today most likely suffer from a high concentration of defects. In this talk, I will share our progress and the challenges we face in terms of preparing, characterizing these 2D crystals as well as pursuing their applications. This work has been supported in part by NSF, AFOSR and LEAST, one of the STARnet centers.

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

    SciTech Connect

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

    2013-01-01

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

  13. Controlling the Dynamics of the Five-Mode Truncation System of the 2-d Navier-Stokes Equations

    NASA Astrophysics Data System (ADS)

    Smaoui, Nejib; Zribi, Mohamed

    2015-11-01

    The dynamics and the control problem of the two dimensional (2-d) Navier-Stokes (N-S) equations with spatially periodic and temporally steady forcing is addressed. At first, the Fourier Galerkin method is applied to the 2-d N-S equations to obtain a fifth order system of nonlinear ordinary differential equations (ODE) that approximates the behavior of these equations. Simulation studies indicate that the obtained ODE system captures the behavior of the 2-d N-S equations. Then, a control law is proposed to drive the states of the ODE system to a desired fixed point. Next, a second control law is developed to synchronize two reduced order ODE models of the 2-d N-S equations having the same Reynolds number and starting from different initial conditions. Finally, simulation results are undertaken to validate the theoretical developments. This research was supported and funded by the Research Sector, Kuwait University under Grant No. SM 05/15.

  14. Combined global 2D-local 3D modeling of the industrial Czochralski silicon crystal growth process

    NASA Astrophysics Data System (ADS)

    Jung, T.; Seebeck, J.; Friedrich, J.

    2013-04-01

    A global, axisymmetric thermal model of a Czochralski furnace is coupled to an external, local, 3D, time-dependent flow model of the melt via the inclusion of turbulent heat fluxes, extracted from the 3D melt model, into the 2D furnace model. Boundary conditions of the 3D model are updated using results from the 2D model. In the 3D model the boundary layers are resolved by aggressive mesh refinement towards the walls, and the Large Eddy Simulation approach is used to model the turbulent flow in the melt volume on a relatively coarse mesh to minimize calculation times. It is shown that by using this approach it is possible to reproduce fairly good results from Direct Numerical Simulations obtained on much finer meshes, as well as experimental results for interface shape and oxygen concentration in the case of growth of silicon crystals with 210 mm diameter for photovoltaics by the Czochralski method.

  15. Stacking sequence determines Raman intensities of observed interlayer shear modes in 2D layered materials – A general bond polarizability model

    PubMed Central

    Luo, Xin; Lu, Xin; Cong, Chunxiao; Yu, Ting; Xiong, Qihua; Ying Quek, Su

    2015-01-01

    2D layered materials have recently attracted tremendous interest due to their fascinating properties and potential applications. The interlayer interactions are much weaker than the intralayer bonds, allowing the as-synthesized materials to exhibit different stacking sequences, leading to different physical properties. Here, we show that regardless of the space group of the 2D materials, the Raman frequencies of the interlayer shear modes observed under the typical configuration blue shift for AB stacked materials, and red shift for ABC stacked materials, as the number of layers increases. Our predictions are made using an intuitive bond polarizability model which shows that stacking sequence plays a key role in determining which interlayer shear modes lead to the largest change in polarizability (Raman intensity); the modes with the largest Raman intensity determining the frequency trends. We present direct evidence for these conclusions by studying the Raman modes in few layer graphene, MoS2, MoSe2, WSe2 and Bi2Se3, using both first principles calculations and Raman spectroscopy. This study sheds light on the influence of stacking sequence on the Raman intensities of intrinsic interlayer modes in 2D layered materials in general, and leads to a practical way of identifying the stacking sequence in these materials. PMID:26469313

  16. Stacking sequence determines Raman intensities of observed interlayer shear modes in 2D layered materials--A general bond polarizability model.

    PubMed

    Luo, Xin; Lu, Xin; Cong, Chunxiao; Yu, Ting; Xiong, Qihua; Quek, Su Ying

    2015-01-01

    2D layered materials have recently attracted tremendous interest due to their fascinating properties and potential applications. The interlayer interactions are much weaker than the intralayer bonds, allowing the as-synthesized materials to exhibit different stacking sequences, leading to different physical properties. Here, we show that regardless of the space group of the 2D materials, the Raman frequencies of the interlayer shear modes observed under the typical z(xx)z configuration blue shift for AB stacked materials, and red shift for ABC stacked materials, as the number of layers increases. Our predictions are made using an intuitive bond polarizability model which shows that stacking sequence plays a key role in determining which interlayer shear modes lead to the largest change in polarizability (Raman intensity); the modes with the largest Raman intensity determining the frequency trends. We present direct evidence for these conclusions by studying the Raman modes in few layer graphene, MoS2, MoSe2, WSe2 and Bi2Se3, using both first principles calculations and Raman spectroscopy. This study sheds light on the influence of stacking sequence on the Raman intensities of intrinsic interlayer modes in 2D layered materials in general, and leads to a practical way of identifying the stacking sequence in these materials. PMID:26469313

  17. Development of fracture facets from a crack loaded in mode I+III: Solution and application of a model 2D problem

    NASA Astrophysics Data System (ADS)

    Leblond, Jean-Baptiste; Frelat, Joël

    2014-03-01

    It is experimentally well-known that a crack loaded in mode I+III propagates through formation of discrete fracture facets inclined at a certain tilt angle on the original crack plane, depending on the ratio of the mode III to mode I initial stress intensity factors. Pollard et al. (1982) have proposed to calculate this angle by considering the tractions on all possible future infinitesimal facets and assuming shear tractions to be zero on that which will actually develop. In this paper we consider the opposite case of well-developed facets; the stress field near the lateral fronts of such facets becomes independent of the initial crack and essentially 2D in a plane perpendicular to the main direction of crack propagation. To determine this stress field, we solve the model 2D problem of an infinite plate containing an infinite periodic array of cracks inclined at some angle on a straight line, and loaded through uniform stresses at infinity. This is done first analytically, for small values of this angle, by combining Muskhelishvili's (1953) formalism and a first-order perturbation procedure. The formulae found for the 2D stress intensity factors are then extended in an approximate way to larger angles by using another reference solution, and finally assessed through comparison with some finite element results. To finally illustrate the possible future application of these formulae to the prediction of the stationary tilt angle, we introduce the tentative assumption that the 2D mode II stress intensity factor is zero on the lateral fronts of the facets. An approximate formula providing the tilt angle as a function of the ratio of the mode III to mode I stress intensity factors of the initial crack is deduced from there. This formula, which slightly depends on the type of loading imposed, predicts somewhat smaller angles than that of Pollard et al. (1982).

  18. Hydrodynamics of embedded planets' first atmospheres - I. A centrifugal growth barrier for 2D flows

    NASA Astrophysics Data System (ADS)

    Ormel, Chris W.; Kuiper, Rolf; Shi, Ji-Ming

    2015-01-01

    In the core accretion paradigm of planet formation, gas giants only form a massive atmosphere after their progenitors exceeded a threshold mass: the critical core mass. Most (exo)planets, being smaller and rock/ice-dominated, never crossed this line. Nevertheless, they were massive enough to attract substantial amounts of gas from the disc, while their atmospheres remained in pressure-equilibrium with the disc. Our goal is to characterize the hydrodynamical properties of the atmospheres of such embedded planets and the implications for their (long-term) evolution. In this paper - the first in series - we start to investigate the properties of an isothermal and inviscid flow past a small, embedded planet by conducting local, 2D hydrodynamical simulations. Using the PLUTO code, we confirm that the flow is steady and bound. This steady outcome is most apparent for the log-polar grid (with the grid spacing proportional to the distance from the planet). For low-mass planets, Cartesian grids are somewhat less efficient as they have difficulty to follow the circular, large speeds in the deep atmosphere. Relating the amount of rotation to the gas fraction of the atmosphere, we find that more massive atmospheres rotate faster - a finding consistent with Kelvin's circulation theorem. Rotation therefore limits the amount of gas that planets can acquire from the nebula. Dependent on the Toomre-Q parameter of the circumstellar disc, the planet's atmosphere will reach Keplerian rotation before self-gravity starts to become important.

  19. Quantitative analysis of molecular-level DNA crystal growth on a 2D surface

    PubMed Central

    Lee, Junwye; Hamada, Shogo; Hwang, Si Un; Amin, Rashid; Son, Junyoung; Dugasani, Sreekantha Reddy; Murata, Satoshi; Park, Sung Ha

    2013-01-01

    Crystallization is an essential process for understanding a molecule's aggregation behavior. It provides basic information on crystals, including their nucleation and growth processes. Deoxyribonucleic acid (DNA) has become an interesting building material because of its remarkable properties for constructing various shapes of submicron-scale DNA crystals by self-assembly. The recently developed substrate-assisted growth (SAG) method produces fully covered DNA crystals on various substrates using electrostatic interactions and provides an opportunity to observe the overall crystallization process. In this study, we investigated quantitative analysis of molecular-level DNA crystallization using the SAG method. Coverage and crystal size distribution were studied by controlling the external parameters such as monomer concentration, annealing temperature, and annealing time. Rearrangement during crystallization was also discussed. We expect that our study will provide overall picture of the fabrication process of DNA crystals on the charged substrate and promote practical applications of DNA crystals in science and technology. PMID:23817625

  20. Colloidal 2D-0D Lateral Nanoheterostructures: A Case Study of Site-Selective Growth of CdS Nanodots onto Bi₂Se₃ Nanosheets.

    PubMed

    Xu, Biao; Li, Haoyi; Yang, Hao; Xiang, Wentian; Zhou, Gang; Wu, Yue; Wang, Xun

    2015-06-10

    Two-dimensional (2D) nanoheterostructure (2D NHS) with nanoparticles grown on 2D nanomaterial substrates could potentially enable many novel functionalities. Controlled site-selective growth of nanoparticles on either the lateral or the basal directions of 2D nanomaterial substrates is desirable but extremely challenging. Herein, we demonstrate the rational control of lateral- and basal-selective attachment of CdS nanoparticles onto 2D Bi2Se3 nanosheets through solution phase reactions. The combination of experimental and theoretical efforts elucidate that site-relevant interfacial bonding and kinetic control of molecular precursors play vital roles for site selectivity. Furthermore, the electronic structures revealed from density functional theory calculations explain the superior performance of the lateral 2D NHSs compared to their basal counterpart in prototype photoelectrochemical cells. The present study will inspire the construction of other site-selective 2D NHSs with well-defined structure and unique properties. PMID:26024068

  1. Use of 2D and 3D Imaging Techniques to Understand Fracture Growth

    NASA Astrophysics Data System (ADS)

    Lockner, D. A.

    2004-05-01

    The monitoring of acoustic emissions (AE) is a valuable tool for studying the brittle fracture process in rock. With the improved characterization of transducer response, researchers are able to apply a broad spectrum of seismological techniques to AE catalogues collected in the laboratory; i.e., moment tensor analysis, Vp/Vs ratios, attenuation, event clustering statistics, Gutenberg-Richter b-value and aftershock analysis. Since AE occurs spontaneously as a result of unstable microcrack growth during rock deformation experiments, it provides a non-destructive method to observe damage accumulation. I will give examples of visualization techniques that have proven helpful in the analysis of fracture nucleation and growth based on 3D event locations in granite and sandstone samples. These techniques are useful in interpreting the development of complex fracture systems in lab samples. Complementary measurements of wave speed anisotropy and heterogeneity are used to infer both the development of damage zones and the rate of infiltration of water during fluid injection experiments. Finally, spatial clustering of AE events is evaluated in terms of the surface roughness of reactivated faults during triaxial deformation experiments.

  2. Facile synthesis of core-shell and Janus particles via 2-D dendritic growth of gold film.

    PubMed

    Jang, Se Gyu; Kim, Se-Heon; Lee, Su Yeon; Jeong, Woong Chan; Yang, Seung-Man

    2010-10-15

    We report a facile method for the electroless deposition (ELD) of gold film via two-dimensional (2-D) dendritic growth. Our scheme employs protonated amine groups, which electrostatically attract both the negatively charged reducing agent and gold-precursor. This electrostatic interaction increases the local concentrations of gold-precursor and reducing agent near the silica surface to levels high enough for gold films with a 2-D fractal morphology to form directly on the surfaces of the amine-functionalized silica nanospheres by diffusion-limited aggregation. Our one-pot reaction avoids the need for seed attachment, which is typically employed for the growth of metallic shells on nanospheres. Therefore, the proposed method significantly reduces the number of processing steps required for the production of core-shell nanospheres. The gold morphologies were systematically investigated in terms of various synthesis variables, including solution pH, reducing agent concentration, and gold precursor injection speed. In addition, we synthesized gold-capped silica nanospheres via ELD of gold on a patterned array of silica nanospheres embedded in polystyrene (PS) film followed by dissolution of the PS matrix, thus demonstrating the potential utility of the proposed method in emerging fields of materials science such as patterning of noble metals and studies of nanometer-scale optics. PMID:20678776

  3. Polymorphism, crystal nucleation and growth in the phase-field crystal model in 2D and 3D.

    PubMed

    Tóth, Gyula I; Tegze, György; Pusztai, Tamás; Tóth, Gergely; Gránásy, László

    2010-09-15

    We apply a simple dynamical density functional theory, the phase-field crystal (PFC) model of overdamped conservative dynamics, to address polymorphism, crystal nucleation, and crystal growth in the diffusion-controlled limit. We refine the phase diagram for 3D, and determine the line free energy in 2D and the height of the nucleation barrier in 2D and 3D for homogeneous and heterogeneous nucleation by solving the respective Euler-Lagrange (EL) equations. We demonstrate that, in the PFC model, the body-centered cubic (bcc), the face-centered cubic (fcc), and the hexagonal close-packed structures (hcp) compete, while the simple cubic structure is unstable, and that phase preference can be tuned by changing the model parameters: close to the critical point the bcc structure is stable, while far from the critical point the fcc prevails, with an hcp stability domain in between. We note that with increasing distance from the critical point the equilibrium shapes vary from the sphere to specific faceted shapes: rhombic dodecahedron (bcc), truncated octahedron (fcc), and hexagonal prism (hcp). Solving the equation of motion of the PFC model supplied with conserved noise, solidification starts with the nucleation of an amorphous precursor phase, into which the stable crystalline phase nucleates. The growth rate is found to be time dependent and anisotropic; this anisotropy depends on the driving force. We show that due to the diffusion-controlled growth mechanism, which is especially relevant for crystal aggregation in colloidal systems, dendritic growth structures evolve in large-scale isothermal single-component PFC simulations. An oscillatory effective pair potential resembling those for model glass formers has been evaluated from structural data of the amorphous phase obtained by instantaneous quenching. Finally, we present results for eutectic solidification in a binary PFC model. PMID:21386517

  4. Polymorphism, crystal nucleation and growth in the phase-field crystal model in 2D and 3D

    NASA Astrophysics Data System (ADS)

    Tóth, Gyula I.; Tegze, György; Pusztai, Tamás; Tóth, Gergely; Gránásy, László

    2010-09-01

    We apply a simple dynamical density functional theory, the phase-field crystal (PFC) model of overdamped conservative dynamics, to address polymorphism, crystal nucleation, and crystal growth in the diffusion-controlled limit. We refine the phase diagram for 3D, and determine the line free energy in 2D and the height of the nucleation barrier in 2D and 3D for homogeneous and heterogeneous nucleation by solving the respective Euler-Lagrange (EL) equations. We demonstrate that, in the PFC model, the body-centered cubic (bcc), the face-centered cubic (fcc), and the hexagonal close-packed structures (hcp) compete, while the simple cubic structure is unstable, and that phase preference can be tuned by changing the model parameters: close to the critical point the bcc structure is stable, while far from the critical point the fcc prevails, with an hcp stability domain in between. We note that with increasing distance from the critical point the equilibrium shapes vary from the sphere to specific faceted shapes: rhombic dodecahedron (bcc), truncated octahedron (fcc), and hexagonal prism (hcp). Solving the equation of motion of the PFC model supplied with conserved noise, solidification starts with the nucleation of an amorphous precursor phase, into which the stable crystalline phase nucleates. The growth rate is found to be time dependent and anisotropic; this anisotropy depends on the driving force. We show that due to the diffusion-controlled growth mechanism, which is especially relevant for crystal aggregation in colloidal systems, dendritic growth structures evolve in large-scale isothermal single-component PFC simulations. An oscillatory effective pair potential resembling those for model glass formers has been evaluated from structural data of the amorphous phase obtained by instantaneous quenching. Finally, we present results for eutectic solidification in a binary PFC model.

  5. Subcritical crack growth in soda-lime glass in combined mode I and mode II loading

    NASA Technical Reports Server (NTRS)

    Singh, Dileep; Shetty, Dinesh K.

    1990-01-01

    Subcritical crack growth under mixed-mode loading was studied in soda-lime glass. Pure mode I, combined mode I and mode II, and pure mode II loadings were achieved in precracked disk specimens by loading in diametral compression at selected angles with respect to the symmetric radial crack. Crack growth was monitored by measuring the resistance changes in a microcircuit grid consisting of parallel, electrically conducting grid lines deposited on the surface of the disk specimens by photolithography. Subcritical crack growth rates in pure mode I, pure mode II, and combined mode I and mode II loading could be described by an exponential relationship between crack growth rate and an effective crack driving force derived from a mode I-mode II fracture toughness envelope. The effective crack driving force was based on an empirical representation of the noncoplanar strain energy release rate. Stress intensities for kinked cracks were assessed using the method of caustics and an initial decrease and a subsequent increase in the subcritical crack growth rates of kinked cracks were shown to correlate with the variations of the mode I and the mode II stress intensities.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  8. Triangular step instability and 2D/3D transition during the growth of strained Ge films on Si(100)

    SciTech Connect

    Chen, K.M.; Jesson, D.E.; Pennycook, S.J.; Mostoller, M.; Kaplan, T.; Thundat, T.; Warmack, R.J.

    1995-04-01

    We show that an activation energy barrier exists to the formation of wavy step edges due to stress-driven 2D instability. The barrier height and the barrier width depend sensitively on the surface stress anisotropy and step free energy. The large misfit strain of Ge films significantly reduces the barrier by lowering the S{sub B} step energy, inducing S{sub A} steps to undergo a triangular instability even during low temperature growth of Ge on Si(100). The step instability results in a novel arrangement of stress domains, and the interaction between the domains causes a spatial variation of surface strain with a surprisingly large influence on the energy barrier for island nucleation. Calculations indicate a dramatic enhancement in the nucleation of 3D islands at the apex regions of triangular steps, in good agreement with our experimental measurements.

  9. Effects of standing wave states on low temperature growth of 2D Pb islands on Si(111) surfaces

    NASA Astrophysics Data System (ADS)

    Tsong, Tien T.

    2002-03-01

    Flat-top 2D Pb islands of nanometer size with critical and magic thickness have been observed in the Pb/Si(111)-7x7 system at low temperature using scanning tunneling microscopy. The growth behavior, formation of new electronic bound states, redistribution of surface charge density, and oscillatory relaxations in the island thickness arise from quantum size effects. All these properties are perfectly correlated to each other [1]. This and other more recent results will be presented. Work supported by the NSC of ROC and Academia Sinica. [1]. W. B. Su, S. H. Chang, W. B. Jian, C. S. Chang, L. J. Chen and T. T. Tsong, Phys. Rev. Lett. 86, 5116 (2001); W. B. Su, S. H. Chang, C. S. Chang, L. J. Chen and T. T. Tsong, Jpn J. Appl. Phys. 40, 4299 (2001).

  10. The Effect of Magnetic Field on 2-D Problem for a Mode-I Crack of a Fiber-Reinforced in Generalized Thermoelasticity

    NASA Astrophysics Data System (ADS)

    Lotfy, Kh.; Othman, Mohamed I. A.

    2014-01-01

    In the present paper, the coupled theory, Lord-Şhulman theory, and Green-Lindsay theory are introduced to study the influence of a magnetic field on the 2-D problem of a fiber-reinforced thermoelastic. These theories are also applied to study the influence of reinforcement on the total deformation of an infinite space weakened by a finite linear opening Mode-I crack. The material is homogeneous and an isotropic elastic half-space. The crack is subjected to a prescribed temperature and stress distribution. Normal mode analysis is used to solve the problem of a Mode-I crack. Numerical results for the temperature, the displacement, and thermal stress components are given and illustrated graphically in the absence and the presence of the magnetic field. A comparison between the three theories is also made for different depths.

  11. Mode 2 fatigue crack growth specimen development

    NASA Technical Reports Server (NTRS)

    Buzzard, R. J.; Gross, B.; Srawley, J. E.

    1983-01-01

    A Mode II test specimen was developed which has potential application in understanding phemonena associated with mixed mode fatigue failures in high performance aircraft engine bearing races. The attributes of the specimen are: it contains one single ended notch, which simplifiers data gathering and reduction; the fatigue crack grous in-line with the direction of load application; a single axis test machine is sufficient to perform testing; and the Mode I component is vanishingly small.

  12. Slow crack growth in glass in combined mode I and mode II loading

    NASA Technical Reports Server (NTRS)

    Shetty, D. K.; Rosenfield, A. R.

    1991-01-01

    Slow crack growth in soda-lime glass under combined mode I and mode II loading was investigated in precracked disk specimens in which pure mode I, pure mode II, and various combinations of mode I and mode II were achieved by loading in diametral compression at selected angles with respect to symmetric radial cracks. It is shown that slow crack growth under these conditions can be described by a simple exponential relationship with elastic strain energy release rate as the effective crack-driving force parameter. It is possible to interpret this equation in terms of theoretical models that treat subcritical crack growth as a thermally activated bond-rupture process with an activation energy dependent on the environment, and the elastic energy release rate as the crack-driving force parameter.

  13. New Insights to the Sawtooth Oscillation (m/n=1/1 mode) in Hot Plasmas based on High Resolution 2-D Images of Te Fluctuations

    SciTech Connect

    H.K. Park, N.C. Luhmann, Jr, A.J.H. Donné, C.W. Domier, T. Munsat, M.J. Van de Pol, and the TEXTOR Team

    2007-11-26

    Two dimensional (2-D) images of electron temperature fluctuations with high temporal and spatial resolution have been employed to study the sawtooth oscillation (m/n=1/1 mode) in Toroidal EXperiment for Technology Oriented Research (TEXTOR) tokamak plasmas. 2-D imaging data revealed new physics which were not available in previous studies based on the 1-D electron temperature measurement and X-ray tomography. Review of the physics of the sawtooth oscillation is given by comparative studies with prominent theoretical models suggest that a new physics paradigm is needed to describe the reconnection physics of the sawtooth oscillation. The new insights are: A pressure driven instability (not a ballooning mode) leads to the X-point reconnection process. The reconnection process is identified as a random 3-D local reconnection process with a helical structure. The reconnection time scale is similar for different types of sawtooth oscillation ("kink" and tearing type) and is significantly faster than the resistive time scale. Heat flow from the core to the outside of the inversion radius during the reconnection process is highly collective rather than stochastic.

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

    PubMed

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

    2016-09-20

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

  15. Shape regression machine and efficient segmentation of left ventricle endocardium from 2D B-mode echocardiogram.

    PubMed

    Zhou, Shaohua Kevin

    2010-08-01

    We present a machine learning approach called shape regression machine (SRM) for efficient segmentation of an anatomic structure that exhibits a deformable shape in a medical image, e.g., left ventricle endocardial wall in an echocardiogram. The SRM achieves efficient segmentation via statistical learning of the interrelations among shape, appearance, and anatomy, which are exemplified by an annotated database. The SRM is a two-stage approach. In the first stage that estimates a rigid shape to solve an automatic initialization problem, it derives a regression solution to object detection that needs just one scan in principle and a sparse set of scans in practice, avoiding the exhaustive scanning required by the state-of-the-art classification-based detection approach while yielding comparable detection accuracy. In the second stage that estimates the nonrigid shape, it again learns a nonlinear regressor to directly associate nonrigid shape with image appearance. The underpinning of both stages is a novel image-based boosting ridge regression (IBRR) method that enables multivariate, nonlinear modeling and accommodates fast evaluation. We demonstrate the efficiency and effectiveness of the SRM using experiments on segmenting the left ventricle endocardium from a B-mode echocardiogram of apical four chamber view. The proposed algorithm is able to automatically detect and accurately segment the LV endocardial border in about 120ms. PMID:20494610

  16. 1,25(OH)2D3 Alters Growth Plate Maturation and Bone Architecture in Young Rats with Normal Renal Function

    PubMed Central

    Idelevich, Anna; Kerschnitzki, Michael; Shahar, Ron; Monsonego-Ornan, Efrat

    2011-01-01

    Whereas detrimental effects of vitamin D deficiency are known over century, the effects of vitamin D receptor activation by 1,25(OH)2D3, the principal hormonal form of vitamin D, on the growing bone and its growth plate are less clear. Currently, 1,25(OH)2D3 is used in pediatric patients with chronic kidney disease and mineral and bone disorder (CKD-MBD) and is strongly associated with growth retardation. Here, we investigate the effect of 1,25(OH)2D3 treatment on bone development in normal young rats, unrelated to renal insufficiency. Young rats received daily i.p. injections of 1 µg/kg 1,25(OH)2D3 for one week, or intermittent 3 µg/kg 1,25(OH)2D3 for one month. Histological analysis revealed narrower tibial growth plates, predominantly in the hypertrophic zone of 1,25(OH)2D3-treated animals in both experimental protocols. This phenotype was supported by narrower distribution of aggrecan, collagens II and X mRNA, shown by in situ hybridization. Concomitant with altered chondrocyte maturation, 1,25(OH)2D3 increased chondrocyte proliferation and apoptosis in terminal hypertrophic cells. In vitro treatment of the chondrocytic cell line ATDC5 with 1,25(OH)2D3 lowered differentiation and increased proliferation dose and time-dependently. Micro-CT analysis of femurs from 1-week 1,25(OH)2D3-treated group revealed reduced cortical thickness, elevated cortical porosity, and higher trabecular number and thickness. 1-month administration resulted in a similar cortical phenotype but without effect on trabecular bone. Evaluation of fluorochrome binding with confocal microscopy revealed inhibiting effects of 1,25(OH)2D3 on intracortical bone formation. This study shows negative effects of 1,25(OH)2D3 on growth plate and bone which may contribute to the exacerbation of MBD in the CKD pediatric patients. PMID:21695192

  17. Transport modes during crystal growth in a centrifuge

    NASA Technical Reports Server (NTRS)

    Arnold, William A.; Wilcox, William R.; Carlson, Frederick; Chait, Arnon; Regel', Liia L.

    1992-01-01

    Flow modes arising under average acceleration in centrifugal crystal growth, the gradient of acceleration, and the Coriolis force are investigated using a fully nonlinear three-dimensional numerical model for a centrifugal crystal growth experiment. The analysis focuses on an examination of the quasi-steady state flow modes. The importance of the gradient acceleration is determined by the value of a new nondimensional number, Ad.

  18. AtHD2D Gene Plays a Role in Plant Growth, Development, and Response to Abiotic Stresses in Arabidopsis thaliana

    PubMed Central

    Han, Zhaofen; Yu, Huimin; Zhao, Zhong; Hunter, David; Luo, Xinjuan; Duan, Jun; Tian, Lining

    2016-01-01

    The histone deacetylases play important roles in the regulation of gene expression and the subsequent control of a number of important biological processes, including those involved in the response to environmental stress. A specific group of histone deacetylase genes, HD2, is present in plants. In Arabidopsis, HD2s include HD2A, HD2B, HD2C, and HD2D. Previous research showed that HD2A, HD2B, and HD2C are more related in terms of expression and function, but not HD2D. In this report, we studied different aspects of AtHD2D in Arabidopsis with respect to plant response to drought and other abiotic stresses. Bioinformatics analysis indicates that HD2D is distantly related to other HD2 genes. Transient expression in Nicotiana benthamiana and stable expression in Arabidopsis of AtHD2D fused with gfp showed that AtHD2D was expressed in the nucleus. Overexpression of AtHD2D resulted in developmental changes including fewer main roots, more lateral roots, and a higher root:shoot ratio. Seed germination and plant flowering time were delayed in transgenic plants expressing AtHD2D, but these plants exhibited higher degrees of tolerance to abiotic stresses, including drought, salt, and cold stresses. Physiological studies indicated that the malondialdehyde (MDA) content was high in wild-type plants but in plants overexpressing HD2D the MDA level increased slowly in response to stress conditions of drought, cold, and salt stress. Furthermore, electrolyte leakage in leaf cells of wild type plants increased but remained stable in transgenic plants. Our results indicate that AtHD2D is unique among HD2 genes and it plays a role in plant growth and development regulation and these changes can modulate plant stress responses. PMID:27066015

  19. AtHD2D Gene Plays a Role in Plant Growth, Development, and Response to Abiotic Stresses in Arabidopsis thaliana.

    PubMed

    Han, Zhaofen; Yu, Huimin; Zhao, Zhong; Hunter, David; Luo, Xinjuan; Duan, Jun; Tian, Lining

    2016-01-01

    The histone deacetylases play important roles in the regulation of gene expression and the subsequent control of a number of important biological processes, including those involved in the response to environmental stress. A specific group of histone deacetylase genes, HD2, is present in plants. In Arabidopsis, HD2s include HD2A, HD2B, HD2C, and HD2D. Previous research showed that HD2A, HD2B, and HD2C are more related in terms of expression and function, but not HD2D. In this report, we studied different aspects of AtHD2D in Arabidopsis with respect to plant response to drought and other abiotic stresses. Bioinformatics analysis indicates that HD2D is distantly related to other HD2 genes. Transient expression in Nicotiana benthamiana and stable expression in Arabidopsis of AtHD2D fused with gfp showed that AtHD2D was expressed in the nucleus. Overexpression of AtHD2D resulted in developmental changes including fewer main roots, more lateral roots, and a higher root:shoot ratio. Seed germination and plant flowering time were delayed in transgenic plants expressing AtHD2D, but these plants exhibited higher degrees of tolerance to abiotic stresses, including drought, salt, and cold stresses. Physiological studies indicated that the malondialdehyde (MDA) content was high in wild-type plants but in plants overexpressing HD2D the MDA level increased slowly in response to stress conditions of drought, cold, and salt stress. Furthermore, electrolyte leakage in leaf cells of wild type plants increased but remained stable in transgenic plants. Our results indicate that AtHD2D is unique among HD2 genes and it plays a role in plant growth and development regulation and these changes can modulate plant stress responses. PMID:27066015

  20. Step-Edge-Guided Nucleation and Growth of Aligned WSe2 on Sapphire via a Layer-over-Layer Growth Mode.

    PubMed

    Chen, Liang; Liu, Bilu; Ge, Mingyuan; Ma, Yuqiang; Abbas, Ahmad N; Zhou, Chongwu

    2015-08-25

    Two-dimensional (2D) materials beyond graphene have drawn a lot of attention recently. Among the large family of 2D materials, transitional metal dichalcogenides (TMDCs), for example, molybdenum disulfides (MoS2) and tungsten diselenides (WSe2), have been demonstrated to be good candidates for advanced electronics, optoelectronics, and other applications. Growth of large single-crystalline domains and continuous films of monolayer TMDCs has been achieved recently. Usually, these TMDC flakes nucleate randomly on substrates, and their orientation cannot be controlled. Nucleation control and orientation control are important steps in 2D material growth, because randomly nucleated and orientated flakes will form grain boundaries when adjacent flakes merge together, and the formation of grain boundaries may degrade mechanical and electrical properties of as-grown materials. The use of single crystalline substrates enables the alignment of as-grown TMDC flakes via a substrate-flake epitaxial interaction, as demonstrated recently. Here we report a step-edge-guided nucleation and growth approach for the aligned growth of 2D WSe2 by a chemical vapor deposition method using C-plane sapphire as substrates. We found that at temperatures above 950 °C the growth is strongly guided by the atomic steps on the sapphire surface, which leads to the aligned growth of WSe2 along the step edges on the sapphire substrate. In addition, such atomic steps facilitate a layer-over-layer overlapping process to form few-layer WSe2 structures, which is different from the classical layer-by-layer mode for thin-film growth. This work introduces an efficient way to achieve oriented growth of 2D WSe2 and adds fresh knowledge on the growth mechanism of WSe2 and potentially other 2D materials. PMID:26221865

  1. 3D rotating wall vessel and 2D cell culture of four veterinary virus pathogens: A comparison of virus yields, portions of infectious particles and virus growth curves.

    PubMed

    Malenovská, Hana

    2016-02-01

    Only very few comparative studies have been performed that evaluate general trends of virus growth under 3D in comparison with 2D cell culture conditions. The aim of this study was to investigate differences when four animal viruses are cultured in 2D and 3D. Suid herpesvirus 1 (SuHV-1), Vesicular stomatitis virus (VSIV), Bovine adenovirus (BAdV) and Bovine parainfluenza 3 virus (BPIV-3) were cultivated in 3D rotating wall vessels (RWVs) and conventional 2D cultures. The production of virus particles, the portion of infectious particles, and the infectious growth curves were compared. For all viruses, the production of virus particles (related to cell density), including the non-infectious ones, was lower in 3D than in 2D culture. The production of only infectious particles was significantly lower in BAdV and BPIV-3 in 3D cultures in relation to cell density. The two cultivation approaches resulted in significantly different virus particle-to-TCID50 ratios in three of the four viruses: lower in SuHV-1 and BPIV-3 and higher in BAdV in 3D culture. The infectious virus growth rates were not significantly different in all viruses. Although 3D RWV culture resulted in lower production of virus particles compared to 2D systems, the portion of infectious particles was higher for some viruses. PMID:26562056

  2. Mode of dendrite growth in undercooled alloy melts

    SciTech Connect

    Li, J.; Yang, G.; Zhou, Y.

    1998-01-01

    The mode of dendrite growth in the undercooled Ni-50 at% Cu alloy was investigated. At lower undercoolings, the dendrite growth is mainly controlled by solute diffusion, and the formed dendritic morphologies are similar to those of the conventional as-cast equiaxed crystals, except that here the branches are much denser. At higher undercoolings, however, the severe solutal trapping that results from high dendrite growth velocity weakens the effect of solute diffusion on the dendrite growth. In this case, the dendrites branch in the bunching form. The dendrite spacings were measured, and the results were interpreted with the current dendrite growth theories.

  3. Tuning the Growth Pattern in 2D Confinement Regime of Sm2O3 and the Emerging Room Temperature Unusual Superparamagnetism

    PubMed Central

    Guria, Amit K.; Dey, Koushik; Sarkar, Suresh; Patra, Biplab K.; Giri, Saurav; Pradhan, Narayan

    2014-01-01

    Programming the reaction chemistry for superseding the formation of Sm2O3 in a competitive process of formation and dissolution, the crystal growth patterns are varied and two different nanostructures of Sm2O3 in 2D confinement regime are designed. Among these, the regular and self-assembled square platelets nanostructures exhibit paramagnetic behavior analogous to the bulk Sm2O3. But, the other one, 2D flower like shaped nanostructure, formed by irregular crystal growth, shows superparamagnetism at room temperature which is unusual for bulk paramagnet. It has been noted that the variation in the crystal growth pattern is due to the difference in the binding ability of two organic ligands, oleylamine and oleic acid, used for the synthesis and the magnetic behavior of the nanostructures is related to the defects incorporated during the crystal growth. Herein, we inspect the formation chemistry and plausible origin of contrasting magnetism of these nanostructures of Sm2O3. PMID:25269458

  4. Vibrational mode and collision energy effects on reaction of H{sub 2}CO{sup +} with C{sub 2}D{sub 4}

    SciTech Connect

    Liu Jianbo; Devener, Brian van; Anderson, Scott L.

    2004-12-15

    We report the effects of collision energy (E{sub col}) and five different H{sub 2}CO{sup +} vibrational modes on the reaction of H{sub 2}CO{sup +} with C{sub 2}D{sub 4} over the center-of-mass E{sub col} range from 0.1 to 2.1 eV. Properties of various complexes and transition states were also examined computationally. Seven product channels are observed. Charge transfer (CT) has the largest cross section over the entire energy range, substantially exceeding the hard sphere cross section at high energies. Competing with CT are six channels involving transfer of one or more hydrogen atoms or protons and one involving formation of propanal, followed by hydrogen elimination. Despite the existence of multiple deep wells on the potential surface, all reactions go by direct mechanisms, except at the lowest collision energies, where short-lived complexes appear to be important. Statistical complex decay appears adequate to account for the product branching at low collision energies, however, even at the lowest energies, the vibrational effects are counter to statistical expectations. The pattern of E{sub col} and vibrational mode effects provide insight into factors that control reaction and interchannel competition.

  5. Growth of eccentric modes in disc-planet interactions

    NASA Astrophysics Data System (ADS)

    Teyssandier, Jean; Ogilvie, Gordon I.

    2016-05-01

    We formulate a set of linear equations that describe the behaviour of small eccentricities in a protoplanetary system consisting of a gaseous disc and a planet. Eccentricity propagates through the disc by means of pressure and self-gravity, and is exchanged with the planet via secular interactions. Excitation and damping of eccentricity can occur through Lindblad and corotation resonances, as well as viscosity. We compute normal modes of the coupled disc-planet system in the case of short-period giant planets orbiting inside an inner cavity, possibly carved by the stellar magnetosphere. Three-dimensional effects allow for a mode to be trapped in the inner parts of the disc. This mode can easily grow within the disc's lifetime. An eccentric mode dominated by the planet can also grow, although less rapidly. We compute the structure and growth rates of these modes and their dependence on the assumed properties of the disc.

  6. Critical Slowing of Density Fluctuations Approaching the Isotropic-Nematic Transition in Liquid Crystals: 2D IR Measurements and Mode Coupling Theory.

    PubMed

    Sokolowsky, Kathleen P; Bailey, Heather E; Hoffman, David J; Andersen, Hans C; Fayer, Michael D

    2016-07-21

    Two-dimensional infrared (2D IR) data are presented for a vibrational probe in three nematogens: 4-cyano-4'-pentylbiphenyl, 4-cyano-4'-octylbiphenyl, and 4-(trans-4-amylcyclohexyl)-benzonitrile. The spectral diffusion time constants in all three liquids in the isotropic phase are proportional to [T*/(T - T*)](1/2), where T* is 0.5-1 K below the isotropic-nematic phase transition temperature (TNI). Rescaling to a reduced temperature shows that the decays of the frequency-frequency correlation function (FFCF) for all three nematogens fall on the same curve, suggesting a universal dynamic behavior of nematogens above TNI. Spectral diffusion is complete before significant orientational relaxation in the liquid, as measured by optically heterodyne detected-optical Kerr effect (OHD-OKE) spectroscopy, and before any significant orientational randomization of the probe measured by polarization selective IR pump-probe experiments. To interpret the OHD-OKE and FFCF data, we constructed a mode coupling theory (MCT) schematic model for the relationships among three correlation functions: ϕ1, a correlator for large wave vector density fluctuations; ϕ2, the orientational correlation function whose time derivative is the observable in the OHD-OKE experiment; and ϕ3, the FFCF for the 2D IR experiment. The equations for ϕ1 and ϕ2 match those in the previous MCT schematic model for nematogens, and ϕ3 is coupled to the first two correlators in a straightforward manner. Resulting models fit the data very well. Across liquid crystals, the temperature dependences of the coupling constants show consistent, nonmonotonic behavior. A remarkable change in coupling occurs at ∼5 K above TNI, precisely where the rate of spectral diffusion in 5CB was observed to deviate from that of a similar nonmesogenic liquid. PMID:27363680

  7. Centimeter Scale Patterned Growth of Vertically Stacked Few Layer Only 2D MoS2/WS2 van der Waals Heterostructure

    PubMed Central

    Choudhary, Nitin; Park, Juhong; Hwang, Jun Yeon; Chung, Hee-Suk; Dumas, Kenneth H.; Khondaker, Saiful I.; Choi, Wonbong; Jung, Yeonwoong

    2016-01-01

    Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems. Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. Attempts to chemically synthesize these materials have been recently pursued, which are presently limited to randomly and scarcely grown 2D layers with uncontrolled layer numbers on very small areas. Here, we report the chemical vapor deposition (CVD) growth of large-area (>2 cm2) patterned 2D vdW heterostructures composed of few layer, vertically-stacked MoS2 and WS2. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) directly evidence the structural integrity of two distinct 2D TMD layers with atomically sharp vdW heterointerfaces. Electrical transport measurements of these materials reveal diode-like behavior with clear current rectification, further confirming the formation of high-quality heterointerfaces. The intrinsic scalability and controllability of the CVD method presented in this study opens up a wide range of opportunities for emerging applications based on the unconventional functionalities of these uniquely structured materials. PMID:27147503

  8. Centimeter Scale Patterned Growth of Vertically Stacked Few Layer Only 2D MoS2/WS2 van der Waals Heterostructure.

    PubMed

    Choudhary, Nitin; Park, Juhong; Hwang, Jun Yeon; Chung, Hee-Suk; Dumas, Kenneth H; Khondaker, Saiful I; Choi, Wonbong; Jung, Yeonwoong

    2016-01-01

    Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems. Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. Attempts to chemically synthesize these materials have been recently pursued, which are presently limited to randomly and scarcely grown 2D layers with uncontrolled layer numbers on very small areas. Here, we report the chemical vapor deposition (CVD) growth of large-area (>2 cm(2)) patterned 2D vdW heterostructures composed of few layer, vertically-stacked MoS2 and WS2. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) directly evidence the structural integrity of two distinct 2D TMD layers with atomically sharp vdW heterointerfaces. Electrical transport measurements of these materials reveal diode-like behavior with clear current rectification, further confirming the formation of high-quality heterointerfaces. The intrinsic scalability and controllability of the CVD method presented in this study opens up a wide range of opportunities for emerging applications based on the unconventional functionalities of these uniquely structured materials. PMID:27147503

  9. Centimeter Scale Patterned Growth of Vertically Stacked Few Layer Only 2D MoS2/WS2 van der Waals Heterostructure

    NASA Astrophysics Data System (ADS)

    Choudhary, Nitin; Park, Juhong; Hwang, Jun Yeon; Chung, Hee-Suk; Dumas, Kenneth H.; Khondaker, Saiful I.; Choi, Wonbong; Jung, Yeonwoong

    2016-05-01

    Two-dimensional (2D) van der Waal (vdW) heterostructures composed of vertically-stacked multiple transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are envisioned to present unprecedented materials properties unobtainable from any other material systems. Conventional fabrications of these hybrid materials have relied on the low-yield manual exfoliation and stacking of individual 2D TMD layers, which remain impractical for scaled-up applications. Attempts to chemically synthesize these materials have been recently pursued, which are presently limited to randomly and scarcely grown 2D layers with uncontrolled layer numbers on very small areas. Here, we report the chemical vapor deposition (CVD) growth of large-area (>2 cm2) patterned 2D vdW heterostructures composed of few layer, vertically-stacked MoS2 and WS2. Detailed structural characterizations by Raman spectroscopy and high-resolution/scanning transmission electron microscopy (HRTEM/STEM) directly evidence the structural integrity of two distinct 2D TMD layers with atomically sharp vdW heterointerfaces. Electrical transport measurements of these materials reveal diode-like behavior with clear current rectification, further confirming the formation of high-quality heterointerfaces. The intrinsic scalability and controllability of the CVD method presented in this study opens up a wide range of opportunities for emerging applications based on the unconventional functionalities of these uniquely structured materials.

  10. Time resolved x-ray studies on growth mode changes induced by quantum electronic effect

    NASA Astrophysics Data System (ADS)

    Hong, Hawoong; Basile, Leonardo; Peter, Czoschke; Tai-C., Chiang

    2004-03-01

    Growth of Pb thin films on Si(111)-(7x7) was studied by reflection surface x-ray diffraction in real time. During the deposition of Pb films at low temperatures, not only the reflectivity curves, but also all the rocking curves at every points on the reflectivity curves were continuously measured. In other words, two dimensional k-space mapping around specula reflectivity was obtained instead of conventional time-resolved reflectivity measurement at an anti-Bragg position. The abundance of information from real time 2-D k-space maps reveals very clear changes in the growth mode of ultra thin Pb films. In a temperature range where the quantum size effect is dominant, alternating layer and island growth was observed.[1] At the lower temperatures, layer-by-layer growth proceeds without a break. At the higher temperature, films grow rough. Kinetics leading to the growth mode changes will be discussed. [1] Hawoong Hong, C.-M.Wei, M.Y. Chou, Z.Wu, L. Basile, H. Chen, M. Holt, and T.-C. Chiang, Phys. Rev. Lett., 90, 076104 (2003)

  11. High-pressure melt growth and transport properties of SiP, SiAs, GeP, and GeAs 2D layered semiconductors

    NASA Astrophysics Data System (ADS)

    Barreteau, C.; Michon, B.; Besnard, C.; Giannini, E.

    2016-06-01

    Silicon and Germanium monopnictides SiP, SiAs, GeP and GeAs form a family of 2D layered semiconductors. We have succeeded in growing bulk single crystals of these compounds by melt-growth under high pressure (0.5-1 GPa) in a cubic anvil hot press. Large (mm-size), shiny, micaceous crystals of GeP, GeAs and SiAs were obtained, and could be exfoliated into 2D flakes. Small and brittle crystals of SiP were yielded by this method. High-pressure sintered polycrystalline SiP and GeAs have also been successfully used as a precursor in the Chemical Vapor Transport growth of these crystals in the presence of I2 as a transport agent. All compounds are found to crystallize in the expected layered structure and do not undergo any structural transition at low temperature, as shown by Raman spectroscopy down to T=5 K. All materials exhibit a semiconducting behavior. The electrical resistivity of GeP, GeAs and SiAs is found to depend on temperature following a 2D-Variable Range Hopping conduction mechanism. The availability of bulk crystals of these compounds opens new perspectives in the field of 2D semiconducting materials for device applications.

  12. HIGH-MODE RAYLEIGH-TAYLOR GROWTH IN NIF IGNITION CAPSULES

    SciTech Connect

    Hammel, B A; Haan, S W; Clark, D; Edwards, M J; Langer, S H; Marinak, M; Patel, M; Salmonson, J; Scott, H A

    2009-08-04

    An assessment of short wavelength hydrodynamic stability is an essential component in the optimization of NIF ignition target designs. Using highly-resolved massively-parallel 2-D Hydra simulations, we routinely evaluate target designs up to mode numbers of 2000 ({lambda} {approx} 2 {micro}m). On the outer ablator surface, mode numbers up to {approx}300 ({lambda} {approx} 20 {micro}m) can have significant growth in CH capsule designs. At the internal fuel:ablator interface mode numbers up to {approx}2000 are important for both CH and Be designs. In addition, 'isolated features' on the capsule, such as the 'fill-tube' ({approx} 5 {micro}m scale-length) and defects, can seed short wavelength growth at the ablation front and the fuel:ablator interface, leading to the injection of {approx} 10's ng of ablator material into the central hot-spot. We are developing methods to measure high-mode mix on NIF implosion experiments. X-ray spectroscopic methods are appealing since mix into the hot-spot will result in x-ray emission from the high-Z dopant (Cu or Ge) in the ablator material (Be or CH).

  13. Ullmann Reaction of Aryl Chlorides on Various Surfaces and the Application in Stepwise Growth of 2D Covalent Organic Frameworks.

    PubMed

    Shi, Ke Ji; Yuan, Ding Wang; Wang, Cheng Xin; Shu, Chen Hui; Li, Deng Yuan; Shi, Zi Liang; Wu, Xin Yan; Liu, Pei Nian

    2016-03-18

    On-surface Ullmann coupling reaction of aryl chlorides has been achieved on Cu(111), Ag(111), and Au(111), and the mechanism has been investigated on the single molecule level using scanning tunneling microscopy and density functional theory. The different reactivity of the aryl halides was utilized to design a stepwise on-surface synthesis, which affords a zigzag template and then converts to 2D porous networks. PMID:26938859

  14. Growth modes of ZnO nanostructures from laser ablation

    SciTech Connect

    Amarilio-Burshtein, I.; Tamir, S.; Lifshitz, Y.

    2010-03-08

    ZnO nanowires (NWs) and other nanostructures were grown by laser ablation of a ZnO containing target onto different substrates with and without the presence of an Au catalyst. The morphology and structure of the NWs were studied using high resolution scanning and transmission electron microscopes [including imaging, selected area electron diffraction (SAED), and energy dispersive x-ray spectroscopy (EDS)]. The different growth modes obtainable could be tuned by varying the Zn concentration in the vapor phase keeping other growth parameters intact. Possible growth mechanisms of these nanowires are suggested and discussed.

  15. Growth modes of ZnO nanostructures from laser ablation

    NASA Astrophysics Data System (ADS)

    Amarilio-Burshtein, I.; Tamir, S.; Lifshitz, Y.

    2010-03-01

    ZnO nanowires (NWs) and other nanostructures were grown by laser ablation of a ZnO containing target onto different substrates with and without the presence of an Au catalyst. The morphology and structure of the NWs were studied using high resolution scanning and transmission electron microscopes [including imaging, selected area electron diffraction (SAED), and energy dispersive x-ray spectroscopy (EDS)]. The different growth modes obtainable could be tuned by varying the Zn concentration in the vapor phase keeping other growth parameters intact. Possible growth mechanisms of these nanowires are suggested and discussed.

  16. Interpretation of radiative divertor studies with impurity seeding in type-I ELMy H-mode plasmas in JET-ILW using EDGE2D-EIRENE

    NASA Astrophysics Data System (ADS)

    Jaervinen, A. E.; Groth, M.; Airila, M.; Belo, P.; Beurskens, M.; Brezinsek, S.; Clever, M.; Corrigan, G.; Devaux, S.; Drewelow, P.; Eich, T.; Giroud, C.; Harting, D.; Huber, A.; Jachmich, S.; Lawson, K.; Lipschultz, B.; Maddison, G.; Maggi, C.; Makkonen, T.; Marchetto, C.; Marsen, S.; Matthews, G. F.; Meigs, A. G.; Moulton, D.; Stamp, M. F.; Wiesen, S.; Wischmeier, M.

    2015-08-01

    Nitrogen seeded JET-ILW H-mode plasmas have been investigated with EDGE2D-EIRENE. The simulations reproduce the experimentally observed factor of 10 reduction in the outer target power deposition when the normalized divertor radiation, Praddiv/PSOL, increases from the unseeded levels of 15% up to the 50% levels required for detachment. At these radiation levels, nitrogen is predicted dominate the total radiation with a contribution of 85%, consistent with previous measurements in JET-C. Due to the low radiative potential of nitrogen at the electron temperatures above 100 eV, more than 80% of the radiation is predicted to occur in the scrape-off layer, making nitrogen a suitable divertor radiator for typical JET divertor conditions with Te around 30 eV. The simulations reproduce the experimentally observed particle flux reduction at the low-field side target without the need for strong recombination. This is due to strong impurity radiation reducing the power levels entering the deuterium ionization front.

  17. 25(OH)D Is Effective to Repress Human Cholangiocarcinoma Cell Growth through the Conversion of 25(OH)D to 1α,25(OH)2D3

    PubMed Central

    Chiang, Kun-Chun; Yeh, Chun-Nan; Huang, Cheng-Cheng; Yeh, Ta-Sen; S. Pang, Jong-Hwei; Hsu, Jun-Te; Chen, Li-Wei; Kuo, Sheng-Fong; Kittaka, Atsushi; Chen, Tai C.; Juang, Horng-Heng

    2016-01-01

    Cholangiocarcinoma (CCA) is a devastating disease without effective treatments. 1α,25(OH)2D3, the active form of Vitamin D, has emerged as a new anti-cancer regimen. However, the side effect of hypercalcemia impedes its systemic administration. 25(OH)D is biologically inert and needs hydroxylation by CYP27B1 to form 1α,25(OH)2D3, which is originally believed to only take place in kidneys. Recently, the extra-renal expression of CYP27B1 has been identified and in vitro conversion of 25(OH)D to 1α,25(OH)2D3 has been found in some cancer cells with CYP27B1 expression. In this study, CYP27B1 expression was demonstrated in CCA cells and human CCA specimens. 25(OH)D effectively represses SNU308 cells growth, which was strengthened or attenuated as CYP27B1 overexpression or knockdown. Lipocalcin-2 (LCN2) was also found to be repressed by 25(OH)D. After treatment with 800 ng/mL 25(OH)D, the intracellular 1α,25(OH)2D3 concentration was higher in SNU308 cells with CYP27B1 overexpression than wild type SNU308 cells. In a xenograft animal experiment, 25(OH)D, at a dose of 6 μg/kg or 20 μg/kg, significantly inhibited SNU308 cells’ growth without inducing obvious side effects. Collectively, our results indicated that SNU308 cells were able to convert 25(OH)D to 1α,25(OH)2D3 and 25(OH)D CYP27B1 gene therapy could be deemed as a promising therapeutic direction for CCA. PMID:27529229

  18. Characterization of Mode 1 and Mode 2 delamination growth and thresholds in graphite/peek composites

    NASA Technical Reports Server (NTRS)

    Martin, Roderick H.; Murri, Gretchen B.

    1988-01-01

    Composite materials often fail by delamination. The onset and growth of delamination in AS4/PEEK, a tough thermoplastic matrix composite, was characterized for mode 1 and mode 2 loadings, using the Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) test specimens. Delamination growth per fatigue cycle, da/dN, was related to strain energy release rate, G, by means of a power law. However, the exponents of these power laws were too large for them to be adequately used as a life prediction tool. A small error in the estimated applied loads could lead to large errors in the delamination growth rates. Hence strain energy release rate thresholds, G sub th, below which no delamination would occur were also measured. Mode 1 and 2 threshold G values for no delamination growth were found by monitoring the number of cycles to delamination onset in the DCB and ENF specimens. The maximum applied G for which no delamination growth had occurred until at least 1,000,000 cycles was considered the threshold strain energy release rate. Comments are given on how testing effects, facial interference or delamination front damage, may invalidate the experimental determination of the constants in the expression.

  19. Growth mode evolution of hafnium oxide by atomic layer deposition

    SciTech Connect

    Nie, Xianglong; Ma, Fei; Ma, Dayan; Xu, Kewei

    2014-01-15

    HfO{sub 2} thin films were deposited using tetrakis-ethylmethylamido hafnium and H{sub 2}O as precursors on silicon by atomic layer deposition (ALD). The morphology and microstructures at different ALD cycles were characterized by atomic force microscopy and high-resolution transmission electron microscopy. Based on the height–height correlation function and power spectral density function, quantitative analysis of surface morphologies was performed. Three characteristic dimensions (ξ{sub 1}, ξ{sub 2}, and ξ{sub 3}) corresponding to three surface structures, islands, local and global fluctuations, were identified. The evolution of ALD growth mode at range of the three critical scales was investigated, respectively. It suggests the transformation of growth mode from quasi two-dimensional layer-by-layer to three-dimensional island for global fluctuations.

  20. 2D Confined-Space Assisted Growth of Molecular-Level-Thick Polypyrrole Sheets with High Conductivity and Transparency.

    PubMed

    Yang, Yang; Wang, Dong; Wu, Yongjin; Tian, Xiaorui; Qin, Haili; Hu, Liang; Zhang, Ting; Ni, Weihai; Jin, Jian

    2016-04-01

    Herein, the use of a 2D soft template system composed of hundred-nanometer-thick water/ethanol mixed layers sandwiched by lamellar bilayer membranes of a self-assembled amphiphilic molecule to produce ultrathin polyprrole (PPy) with a uniform thickness as thin as 3.8 nm and with large dimensions (>2 μm(2) ) is presented. The obtained PPy nanosheets exhibit regioregularity with ordered chain alignment where the polymer chains in the nanosheets produced are well aligned with a clear interchain spacing as confirmed by small-angle X-ray scattering measurement. The molecular-level-thick PPy nanosheets exhibit extremely high conductivity up to 1330 S m(-1) , thanks to the ordered alignment of polymer chains in the nanosheets, and a high transparency in both the visible region (transmittance >99%) and near-infrared region (transmittance >93%). PMID:26833631

  1. High-throughput 2D root system phenotyping platform facilitates genetic analysis of root growth and development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High-throughput phenotyping of root systems requires a combination of specialized techniques and adaptable plant growth, root imaging and software tools. A custom phenotyping platform was designed to capture images of whole root systems, and novel software tools were developed to process and analyz...

  2. DNT cell inhibits the growth of pancreatic carcinoma via abnormal expressions of NKG2D and MICA in vivo.

    PubMed

    Xu, Hong; Zhu, Xing-Xing; Chen, Jiong

    2016-01-01

    This research aimed to investigate the effects of natural killer group 2 member D (NKG2D) and its ligands major histocompatibility complex class I chain-related molecules A(MICA) in DNT cell killing pancreatic carcinoma. Antibodies adsorption was used to separate DNT cell from human peripheral blood. Human pancreatic tumor models were established via implanting BXPC-3 cells into nude mice. Then randomly divided mice into blank group, gemcitabine group and DNT group. Mice weights and mice tumor volumes were measured every 5 days. 50 days later mice were euthanized at cervical dislocation method. Tumor weights were measured. Relative tumor volume and tumor inhibition rate were calculated. Western blot and qPCR were used to detect the expressions of NKG2D and MICA in the transplanted tumors of the three groups. DNT cell significantly increased over time. The blank group tumor volume and weight were significantly larger than the other groups (p < 0.001, p < 0.001), but there were no significantly difference between DNT group and gemcitabine group (p > 0.05). Gemcitabine and DNT cell tumor inhibition rate were 40.4% and 35.5%. Western blot and qPCR showed that MICA mRNA and protein levels in blank group were significantly higher than DNT group (p = 0.001, p = 0.003). NKG2D mRNA and protein levels in blank group were significantly lower than DNT cells group (p < 0.001, p = 0.001). In conclusion DNT cell can significantly inhibit the growth of pancreatic carcinoma in vivo, and the mechanism may be involved in abnormal expressions of MICA and NKG2D. PMID:26616050

  3. Computer simulation of topological evolution in 2-d grain growth using a continuum diffuse-interface field model

    SciTech Connect

    Fan, D.; Geng, C.; Chen, L.Q.

    1997-03-01

    The local kinetics and topological phenomena during normal grain growth were studied in two dimensions by computer simulations employing a continuum diffuse-interface field model. The relationships between topological class and individual grain growth kinetics were examined, and compared with results obtained previously from analytical theories, experimental results and Monte Carlo simulations. It was shown that both the grain-size and grain-shape (side) distributions are time-invariant and the linear relationship between the mean radii of individual grains and topological class n was reproduced. The moments of the shape distribution were determined, and the differences among the data from soap froth. Potts model and the present simulation were discussed. In the limit when the grain size goes to zero, the average number of grain edges per grain is shown to be between 4 and 5, implying the direct vanishing of 4- and 5-sided grains, which seems to be consistent with recent experimental observations on thin films. Based on the simulation results, the conditions for the applicability of the familiar Mullins-Von Neumann law and the Hillert`s equation were discussed.

  4. New ways to synthesize lead sulfide nanosheets-substituted alkanes direct the growth of 2D nanostructures.

    PubMed

    Bielewicz, Thomas; Klein, Eugen; Klinke, Christian

    2016-09-01

    Two-dimensional colloidal nanosheets represent very attractive optoelectronic materials. They combine good lateral conductivity with solution-processability and geometry-tunable electronic properties. In the case of PbS nanosheets, so far synthesis has been driven by the addition of chloroalkanes as coligands. Here, we demonstrate how to synthesize two-dimensional lead sulfide nanostructures using other halogen alkanes and primary amines. Further, we show that at a reaction temperature of 170 °C a coligand is not even necessary and the only ligand, oleic acid, controls the anisotropic growth of the two-dimensional structures. Also, using thiourea as a sulfide source, nanosheets with lateral dimensions of over 10 μm are possible. PMID:27454196

  5. New ways to synthesize lead sulfide nanosheets—substituted alkanes direct the growth of 2D nanostructures

    NASA Astrophysics Data System (ADS)

    Bielewicz, Thomas; Klein, Eugen; Klinke, Christian

    2016-09-01

    Two-dimensional colloidal nanosheets represent very attractive optoelectronic materials. They combine good lateral conductivity with solution-processability and geometry-tunable electronic properties. In the case of PbS nanosheets, so far synthesis has been driven by the addition of chloroalkanes as coligands. Here, we demonstrate how to synthesize two-dimensional lead sulfide nanostructures using other halogen alkanes and primary amines. Further, we show that at a reaction temperature of 170 °C a coligand is not even necessary and the only ligand, oleic acid, controls the anisotropic growth of the two-dimensional structures. Also, using thiourea as a sulfide source, nanosheets with lateral dimensions of over 10 μm are possible.

  6. Markers of early endothelial dysfunction in intrauterine growth restriction-derived human umbilical vein endothelial cells revealed by 2D-DIGE and mass spectrometry analyses.

    PubMed

    Caniuguir, Andres; Krause, Bernardo J; Hernandez, Cherie; Uauy, Ricardo; Casanello, Paola

    2016-05-01

    Intrauterine growth restriction (IUGR) associates with fetal and placental vascular dysfunction, and increased cardiovascular risk later on life. We hypothesize that endothelial cells derived from IUGR umbilical veins present significant changes in the proteome which could be involved in the endothelial dysfunction associated to this conditions. To address this the proteome profile of human umbilical endothelial cells (HUVEC) isolated from control and IUGR pregnancies was compared by 2D-Differential In Gel Electrophoresis (DIGE) and further protein identification by MALDI-TOF MS. Using 2D-DIGE 124 spots were identified as differentially expressed between control and IUGR HUVEC, considering a cut-off of 2 fold change, which represented ∼10% of the total spots detected. Further identification by MALDI-TOF MS and in silico clustering of the proteins showed that those differentially expressed proteins between control and IUGR HUVEC were mainly related with cytoskeleton organization, proteasome degradation, oxidative stress response, mRNA processing, chaperones and vascular function. Finally Principal Component analysis of the identified proteins showed that differentially expressed proteins allow distinguishing between control and IUGR HUVEC based on their proteomic profile. This study demonstrates for the first time that IUGR-derived HUVEC maintained in primary culture conditions present an altered proteome profile, which could reflect an abnormal programming of endothelial function in this fetal condition. PMID:27208404

  7. Device convolution effects on the collective scattering signal of the E Multiplication-Sign B mode from Hall thruster experiments: 2D dispersion relation

    SciTech Connect

    Cavalier, J.; Lemoine, N.; Bonhomme, G.; Tsikata, S.; Honore, C.; Gresillon, D.

    2012-08-15

    The effect of the collective light scattering diagnostic transfer function is considered in the context of the dispersion relation of the unstable E Multiplication-Sign B mode previously reported. This transfer function is found to have a contribution to the measured frequencies and mode amplitudes which is more or less significant depending on the measurement wavenumbers and angles. After deconvolution, the experimental data are found to be possibly compatible with the idea that the mode frequency in the jet frame (after subtraction of the Doppler effect due to the plasma motion along the thruster axis) is independent of the orientation of the wave vector in the plane orthogonal to the local magnetic field.

  8. Growth of porous anodized alumina on the sputtered aluminum films with 2D-3D morphology for high specific surface area

    NASA Astrophysics Data System (ADS)

    Liao, M. W.; Chung, C. K.

    2014-08-01

    The porous anodic aluminum oxide (AAO) with high-aspect-ratio pore channels is widely used as a template for fabricating nanowires or other one-dimensional (1D) nanostructures. The high specific surface area of AAO can also be applied to the super capacitor and the supporting substrate for catalysis. The rough surface could be helpful to enhance specific surface area but it generally results in electrical field concentration even to ruin AAO. In this article, the aluminum (Al) films with the varied 2D-3D morphology on Si substrates were prepared using magnetron sputtering at a power of 50 W-185 W for 1 h at a working pressure of 2.5 × 10-1 Pa. Then, AAO was fabricated from the different Al films by means of one-step hybrid pulse anodizing (HPA) between the positive 40 V and the negative -2 V (1 s:1 s) for 3 min in 0.3 M oxalic acid at a room temperature. The microstructure and morphology of Al films were characterized by X-ray diffraction, scanning electron microscope and atomic force microscope, respectively. Some hillocks formed at the high target power could be attributed to the grain texture growth in the normal orientation of Al(1 1 1). The 3D porous AAO structure which is different from the conventional 2D planar one has been successfully demonstrated using HPA on the film with greatly rough hillock-surface formed at the highest power of 185 W. It offers a potential application of the new 3D AAO to high specific surface area devices.

  9. Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.; Betti, R.; Bradley, D. K.; Boehly, T. R.; Collins, T. J. B.; Goncharov, V. N.; McKenty, P. W.; Meyerhofer, D. D.; Smalyuk, V. A.; Verdon, C. P.; Glendinning, S. G.; Kalantar, D. H.; Watt, R. G.

    2000-01-01

    The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5×1014 W/cm2. Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 μm diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 μm wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile.

  10. Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

    SciTech Connect

    Knauer, J. P.; Betti, R.; Bradley, D. K.; Boehly, T. R.; Collins, T. J. B.; Goncharov, V. N.; McKenty, P. W.; Meyerhofer, D. D.; Smalyuk, V. A.; Verdon, C. P.

    2000-01-01

    The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5x10{sup 14} W/cm{sup 2}. Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 {mu}m diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 {mu}m wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile. (c) 2000 American Institute of Physics.

  11. InAs nanowire growth modes on Si (111) by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Robson, M. T.; LaPierre, R. R.

    2016-02-01

    InAs nanowires (NWs) were grown on silicon substrates by gas source molecular beam epitaxy using five different growth modes: (1) Au-assisted growth, (2) positioned (patterned) Au-assisted growth, (3) Au-free growth, (4) positioned Au-assisted growth using a patterned oxide mask, and (5) Au-free selective-area epitaxy (SAE) using a patterned oxide mask. Optimal growth conditions (temperature, V/III flux ratio) were identified for each growth mode for control of NW morphology and vertical NW yield. The highest yield (72%) was achieved with the SAE method at a growth temperature of 440 °C and a V/III flux ratio of 4. Growth mechanisms are discussed for each of the growth modes.

  12. Layer-by-Layer Polyelectrolyte Assisted Growth of 2D Ultrathin MoS2 Nanosheets on Various 1D Carbons for Superior Li-Storage.

    PubMed

    Qu, Qunting; Qian, Feng; Yang, Siming; Gao, Tian; Liu, Weijie; Shao, Jie; Zheng, Honghe

    2016-01-20

    Transitional metal sulfide/carbon hybrids with well-defined structures could not only maximize the functional properties of each constituent but engender some unique synergistic effects, holding great promise for applications in Li-ion batteries and supercapacitors and for catalysis. Herein, a facile and versatile approach is developed to controllably grow 2D ultrathin MoS2 nanosheets with a large quantity of exposed edges onto various 1D carbons, including carbon nanotubes (CNTs), electrospun carbon nanofibers, and Te-nanowire-templated carbon nanofibers. The typical approach involves the employment of layer-by-layer (LBL) self-assembled polyelectrolyte, which controls spatially the uniform growth and orientation of ultrathin MoS2 nanosheets on these 1D carbons irrespective of their surface properties. Such unique structures of the as-prepared CNTs@MoS2 hybrid are significantly favorable for the fast diffusions of both Li-ions and electrons, satisfying the kinetic requirements of high-power lithium ion batteries. As a result, CNTs@MoS2 hybrids exhibit excellent electrochemical performances for lithium storage, including a high reversible capacity (1027 mAh g(-1)), high-rate capability (610 mAh g(-1) at 5 C), and excellent cycling stability (negligible capacity loss after 200 continuous cycles). PMID:26709711

  13. Growth and Characterization of Mn Doped InAs/GaSb Quantum Wells: Toward a 2D Quantum Anomalous Hall Insulator

    NASA Astrophysics Data System (ADS)

    Xiao, Di; Kempinger, Susan; Samarth, Nitin

    The new discovery of a class of quantum spin Hall insulators (QSHIs), namely the type-II broken gap InAs/GaSb quantum wells (QWs), has drawn much attention in the condensed matter community. Counter-propagating helical states protected by time reversal symmetry exist at the edge, giving a quantized Hall conductance of 2e2/h, while the bulk remains insulating in this 2D topological insulator (TI). Compared to other TI systems, InAs/GaSb QW has a great advantage that the band structure, with a small hybridization gap, can be continuously tuned through electric fields, allowing the topological phase transition between trivial and topological phases. A recent theoretical proposal [PRL, 113.14(2014)] indicates that it is possible to keep only one chiral edge state without external magnetic field, i.e. the quantum anomalous Hall (QAH) state, by introducing long-range ferromagnetic order into this QW system. (In,Mn)As and (Ga,Mn)Sb have been well studied as diluted magnetic semiconductors, making Mn-doping a reasonable choice. Here, we present preliminary results on the MBE growth and characterization of electrically-gated Mn doped InAs /GaSb QWs. We will present a discussion of magnetization and magneto-transport measurements. Funded by ONR.

  14. Synthesis, structural characterization and microbial activity of 2D Ag(I)-5-aminoisophthalate coordination polymer with a new coordination mode

    NASA Astrophysics Data System (ADS)

    Günay, Handan; Çolak, Alper Tolga; Yeşilel, Okan Zafer; Tunç, Tuncay; Çolak, Ferdağ

    2015-11-01

    In this study, a novel polynuclear Ag(I)-5-aminoisophthalate complex [Ag(μ4-Haip)]n (1) (H2aip = 5-aminoisophthalic acid) has been synthesized. The molecular structure of this complex has been determined by the single crystal X-ray diffraction. The two-dimensional polynuclear complex is crystallized in the triclinic crystal system with space group P-1. The Ag(I) ion is four-coordinated by three carboxylate oxygen atoms of three different Haip ligands and one nitrogen atom in a distorted tetrahedral geometry. Furthermore, a novel coordination mode has shown by H2aip. This complex exhibits photoluminescence in the solid state at room temperature. Antimicrobial activity of complex was evaluated by the agar diffusion method. The complex showed antimicrobial activity against tested microorganism strains (Gram positive, gram negative bacteria, clinic isolate yeast and mold). Moreover this complex showed particularly high antifungal activity against yeast and mold.

  15. Elastic-Plastic Finite Element Analysis of Fatigue Crack Growth in Mode 1 and Mode 2 Conditions

    NASA Technical Reports Server (NTRS)

    Nakagaki, M.; Atluri, S. N.

    1978-01-01

    Presented is an alternate cost-efficient and accurate elastic-plastic finite element procedure to analyze fatigue crack closure and its effects under general spectrum loading. Both Modes 1 and 2 type cycling loadings are considered. Also presented are the results of an investigation, using the newly developed procedure, of various factors that cause crack growth acceleration or retardation and delay effects under high-to-low, low-to-high, single overload, and constant amplitude type cyclic loading in a Mode 1 situation. Further, the results of an investigation of a centercracked panel under external pure shear (Mode 2) cyclic loading, of constant amplitude, are reported.

  16. A Mixed-Mode I/II Fracture Criterion and Its Application in Crack Growth Predictions

    NASA Technical Reports Server (NTRS)

    Sutton, Michael A.; Deng, Xiaomin; Ma, Fashang; Newman, James S., Jr.

    1999-01-01

    A crack tip opening displacement (CTOD)-based, mixed mode fracture criterion is developed for predicting the onset and direction of crack growth. The criterion postulates that crack growth occurs in either the Mode I or Mode II direction, depending on whether the maximum in either the opening or the shear component of CTOD, measured at a specified distance behind the crack tip, attains a critical value. For crack growth direction prediction, the proposed CTOD criterion is shown to be equivalent to seven commonly used crack growth criteria under linearly elastic and asymptotic conditions. Under elastic-plastic conditions the CTOD criterion's prediction of the dependence of the crack growth direction on the crack-up mode mixity is in excellent agreement with the Arcan test results. Furthermore, the CTOD criterion correctly predicts the existence of a crack growth transition from mode I to mode II as the mode mixity approaches the mode II loading condition. The proposed CTOD criterion has been implemented in finite element crack growth simulation codes Z1P2DL and FRANC2DL to predict the crack growth paths in (a) a modified Arcan test specimen and fixture made of AL 2024-T34 and (b) a double cantilever beam (DCB) specimen made of AL 7050. A series of crack growth simulations have been carried out for the crack growth tests in the Arcan and DCB specimens and the results further demonstrate the applicability of the mixed mode CTOD fracture criterion crack growth predictions and residual strength analyses for airframe materials.

  17. Growth Rate of the Tidal p-Mode g-Mode Instability in Coalescing Binary Neutron Stars

    NASA Astrophysics Data System (ADS)

    Weinberg, Nevin N.

    2016-03-01

    We recently described an instability due to the nonlinear coupling of p-modes to g-modes and, as an application, we studied the stability of the tide in coalescing binary neutron stars. Although we found that the tide is p-g unstable early in the inspiral and rapidly drives modes to large energies, our analysis only accounted for three-mode interactions. Venumadhav et al. showed that four-mode interactions must also be accounted for as they enter into the analysis at the same order. They found a near-exact cancellation between three- and four-mode interactions and concluded that while the tide in binary neutron stars can be p-g unstable, the growth rates are not fast enough to impact the gravitational wave signal. Their analysis assumes that the linear tide is incompressible, which is true of the static linear tide (the m = 0 harmonic) but not the non-static linear tide (m=+/- 2). Here we account for the compressibility of the linear tide and find that three- and four-mode interactions no longer cancel. As a result, we find that the instability can rapidly drive modes to significant energies well before the binary merges. We also show that linear damping interferes with the cancellation and may further enhance the growth rates. The early onset of the instability (at gravitational wave frequencies ≈ 50 {Hz}) and the large number of rapidly growing modes suggest that the instability could impact the gravitational wave signal. Assessing its impact will require an understanding of how the instability saturates and is left to future work.

  18. Influence of Mixed Mode I-Mode II Loading on Fatigue Delamination Growth Characteristics of a Graphite Epoxy Tape Laminate

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; Johnston, William M., Jr.

    2014-01-01

    Mixed mode I-mode II interlaminar tests were conducted on IM7/8552 tape laminates using the mixed-mode bending test. Three mixed mode ratios, G(sub II)/G(sub T) = 0.2, 0.5, and 0.8, were considered. Tests were performed at all three mixed-mode ratios under quasi-static and cyclic loading conditions, where the former static tests were used to determine initial loading levels for the latter fatigue tests. Fatigue tests at each mixed-mode ratio were performed at four loading levels, Gmax, equal to 0.5G(sub c), 0.4G(sub c), 0.3G(sub c), and 0.2G(sub c), where G(sub c) is the interlaminar fracture toughness of the corresponding mixed-mode ratio at which a test was performed. All fatigue tests were performed using constant-amplitude load control and delamination growth was automatically documented using compliance solutions obtained from the corresponding quasi-static tests. Static fracture toughness data yielded a mixed-mode delamination criterion that exhibited monotonic increase in Gc with mixed-mode ratio, G(sub II)/G(sub T). Fatigue delamination onset parameters varied monotonically with G(sub II)/G(sub T), which was expected based on the fracture toughness data. Analysis of non-normalized data yielded a monotonic change in Paris law exponent with mode ratio. This was not the case when normalized data were analyzed. Fatigue data normalized by the static R-curve were most affected in specimens tested at G(sub II)/G(sub T)=0.2 (this process has little influence on the other data). In this case, the normalized data yielded a higher delamination growth rate compared to the raw data for a given loading level. Overall, fiber bridging appeared to be the dominant mechanism, affecting delamination growth rates in specimens tested at different load levels and differing mixed-mode ratios.

  19. Selective MBE growth of nonalloyed ohmic contacts to 2D electron gas in high-electron-mobility transistors based on GaN/AlGaN heterojunctions

    NASA Astrophysics Data System (ADS)

    Maiboroda, I. O.; Andreev, A. A.; Perminov, P. A.; Fedorov, Yu. V.; Zanaveskin, M. L.

    2014-06-01

    Specific features of how nonalloyed ohmic contacts to the 2D conducting channel of high-electron-mobility transistors based on AlGaN/(AlN)/GaN heterostructures are fabricated via deposition of heavily doped n +-GaN through a SiO2 mask by ammonia molecular-beam epitaxy have been studied. The technique developed makes it possible to obtain specific resistances of contacts to the 2D gas as low as 0.11 Ω mm on various types of Ga-face nitride heterostructures, which are several times lower than the resistance of conventional alloyed ohmic contacts.

  20. Ullmann coupling reaction of aryl chlorides on Au(111) using dosed Cu as a catalyst and the programmed growth of 2D covalent organic frameworks.

    PubMed

    Shi, Ke Ji; Zhang, Xin; Shu, Chen Hui; Li, Deng Yuan; Wu, Xin Yan; Liu, Pei Nian

    2016-07-01

    The efficiency of Ullmann reaction of aryl chlorides on an Au(111) surface has been substantially increased by using dosed Cu as a catalyst. The different reactivity of aryl bromides and aryl chlorides has been exploited to design a programmed, on-surface synthesis to form 2D covalent organic frameworks. PMID:27334002

  1. Growth Mode Transition in Complex Oxide Heteroepitaxy: Atomically Resolved Studies

    DOE PAGESBeta

    Tselev, Alexander; Vasudevan, Rama K.; Gianfrancesco, Anthony G.; Qiao, Liang; Meyer, Tricia L.; Lee, Ho Nyung; Biegalski, Michael D.; Baddorf, Arthur P.; Kalinin, Sergei V.

    2016-04-04

    Here we performed investigations of the atomic-scale surface structure of epitaxial La5/8Ca3/8MnO3 thin films as a model system dependent on growth conditions in pulsed laser deposition with emphasis on film growth kinetics. Postdeposition in situ scanning tunneling microscopy was combined with in operando reflective high-energy electron diffraction to monitor the film growth and ex situ X-ray diffraction for structural analysis. We find a correlation between the out-of-plane lattice parameter and both adspecies mobility and height of the Ehrlich–Schwoebel barrier, with mobility of adatoms greater over the cationically stoichiometric terminations. We find that the data suggest that the out-of-plane lattice parametermore » is dependent on the mechanism of epitaxial strain relaxation, which is controlled by the oxidative power of the deposition environment.« less

  2. Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode

    NASA Astrophysics Data System (ADS)

    Lo, An-Ya; Liu, Shang-Bin; Kuo, Cheng-Tzu

    2010-09-01

    To improve the understanding on CNT growth modes, the various processes, including thermal CVD, MP-CVD and ECR-CVD, have been used to deposit CNTs on nanoporous SBA-15 and Si wafer substrates with C2H2 and H2 as reaction gases. The experiments to vary process parameter of Δ T, defined as the vector quantities of temperature at catalyst top minus it at catalyst bottom, were carried out to demonstrate its effect on the CNT growth mode. The TEM and TGA analyses were used to characterize their growth modes and carbon yields of the processes. The results show that Δ T can be used to monitor the temperature gradient direction across the catalyst nanoparticle during the growth stage of CNTs. The results also indicate that the tip-growth CNTs, base-growth CNTs and onion-like carbon are generally fabricated under conditions of Δ T > 0, <0 and ~0, respectively. Our proposed growth mechanisms can be successfully adopted to explain why the base- and tip-growth CNTs are common in thermal CVD and plasma-enhanced CVD processes, respectively. Furthermore, our experiments have also successfully demonstrated the possibility to vary Δ T to obtain the desired growth mode of CNTs by thermal or plasma-enhanced CVD systems for different applications.

  3. Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode

    PubMed Central

    2010-01-01

    To improve the understanding on CNT growth modes, the various processes, including thermal CVD, MP-CVD and ECR-CVD, have been used to deposit CNTs on nanoporous SBA-15 and Si wafer substrates with C2H2 and H2 as reaction gases. The experiments to vary process parameter of ΔT, defined as the vector quantities of temperature at catalyst top minus it at catalyst bottom, were carried out to demonstrate its effect on the CNT growth mode. The TEM and TGA analyses were used to characterize their growth modes and carbon yields of the processes. The results show that ΔT can be used to monitor the temperature gradient direction across the catalyst nanoparticle during the growth stage of CNTs. The results also indicate that the tip-growth CNTs, base-growth CNTs and onion-like carbon are generally fabricated under conditions of ΔT > 0, <0 and ~0, respectively. Our proposed growth mechanisms can be successfully adopted to explain why the base- and tip-growth CNTs are common in thermal CVD and plasma-enhanced CVD processes, respectively. Furthermore, our experiments have also successfully demonstrated the possibility to vary ΔT to obtain the desired growth mode of CNTs by thermal or plasma-enhanced CVD systems for different applications. PMID:20730080

  4. The growth of the tearing mode - Boundary and scaling effects

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.; Van Hoven, G.

    1983-01-01

    A numerical model of resistive magnetic tearing is developed in order to verify and relate the results of the principal approximations used in analytic analyses and to investigate the solutions and their growth-rate scalings over a large range of primary parameters which include parametric values applicable to the solar atmosphere. The computations cover the linear behavior for a variety of boundary conditions, emphasizing effects which differentiate magnetic tearing in astrophysical situations from that in laboratory devices. Eigenfunction profiles for long and short wavelengths are computed and the applicability of the 'constant psi' approximation is investigated. The growth rate is computed for values of the magnetic Reynolds number up to a trillion and of the dimensionless wavelength parameter down to 0.001. The analysis predicts significant effects due to differing values of the magnetic Reynolds number.

  5. Transient growths of stable modes in riverbed dynamics

    NASA Astrophysics Data System (ADS)

    Vesipa, R.; Camporeale, C.; Ridolfi, L.

    2012-12-01

    Fluvial bars are regular widespread bedforms that are characterized by vertical and transversal scales which are comparable with the stream depth and width, respectively. Although well-established linear and weakly nonlinear stability analysis have already been performed, no nonmodal analysis has been proposed yet. We here demonstrate the remarkable nonnormality of the operator that governs bar dynamics in large regions of the parameter space in fair agreement with our tests in flume experiments. This entails the occurrence of dramatic transient growths in the evolution of bed perturbations. Such algebraic growths suggest a novel explanation, through a purely linear process, of the progressive increase in the dominant bar wavelength that is observed in flume experiments and real rivers during bar inception.

  6. Control of growth mode of multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Quang, Nguyen Hong; Kim, Do-Hyung

    2009-09-01

    We have conducted an experimental study to investigate the synthesis of multi-walled carbon nanotubes (CNTs) by a dc plasma-enhanced chemical vapour deposition (PECVD) technique. The synthesis of base and tip-type of CNTs was selectively controlled by changing the catalyst size, catalyst film thickness correlated with altering the NH3 pretreatment plasma current. These types of CNT showed distinctive properties in nanotube structure, growth rate and vertical alignment, which were confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and in situ optical interference measurement. The vertically aligned behaviour of CNT was systematically studied by using a fine-patterned catalyst layer with diverse critical dimensions. Freestanding single CNT was successfully realized by optimum tip-type CNT growth, conventional photolithography and wet-etch process.

  7. Instability of plasma waves during relaxation of 2D turbulent flows

    NASA Astrophysics Data System (ADS)

    Kabantsev, A. A.; Drsicoll, C. F.

    2015-11-01

    We observe strong excitation of novel low-frequency z-dependent plasma waves (mθ = 0 ,kz = 1) , occurring during the nominally 2D relaxation of turbulent initial conditions (10 -100 interacting vortices) in strongly magnetized electron columns. This initial relaxation often results in ``2D vortex crystal'' states. Here we describe experiments showing the concomitant growth of ill-understood low-frequency plasma waves, probably due to ``leakage'' of 2D turbulent potential energy into z-dependent fluctuations. With plasma injection, the lowest regular Trivelpiece- Gould mode (mθ = 0 ,kz = 1) is observed at fTG (t) ~ 2 . 8 MHz and exponential decay time τTG ~ 1 msec. Also, we observe rapid exponential growth of a novel low-frequency mode with fLF (t) ~ 0 . 3 MHz, nominally also with mθ = 0 ,kz = 1 . In a few milliseconds (several tens of rotation times at B = 10kG), the LF-mode becomes highly nonlinear, developing up to a dozen temporal harmonics. When a LF-harmonic resonates with the decaying TG-mode, LF-mode energy is transferred into the TG-mode, and both modes remain at moderate amplitudes until the 2D turbulent relaxation abates (hundreds of rotation times). The ill-understood fLF is independent of B, even though the growth and duration times follow scale as B1 from the 2D flows. Supported by National Science Foundation Grant PHY-1414570, Department of Energy Grants DE-SC0008693.

  8. Aniso2D

    2005-07-01

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

  9. Designing of a Testing Machine for Shear-Mode Fatigue Crack Growth

    NASA Astrophysics Data System (ADS)

    Kusaba, A.; Okazaki, S.; Endo, M.; Yanase, K.

    As recognized, flaking-type failure is one of the serious problems for railroad tracks and bearings. In essence, flaking-type failure is closely related to the growth of the shear-mode (Mode-II and Mode-III) fatigue crack. In our research group, it is demonstrated that a shear-mode fatigue crack can be reproduced for cylindrical specimens by applying the cyclic torsion in the presence of the static axial compressive stress. However, a biaxial servo-hydraulic fatigue testing machine is quite expensive to purchase and costly to maintain. The low testing speed (about 10Hz) of the testing machine further aggravates the situation. As a result, study on shear-mode fatigue crack growth is still in the nascent stage. To overcome the difficulties mentioned above, in this research activity, we developed a high-performance and cost-effective testing machine to reproduce the shear-mode fatigue crack growth by improving the available resonance-type torsion fatigue testing machine. The primary advantage of using the resonance-type torsion fatigue testing machine is cost-efficiency. In addition, the testing speed effectively can be improved, in comparison with that of a biaxial servo-hydraulic fatigue testing machine. By utilizing the newly-designed testing machine, we have demonstrated that we can successfully reproduce the shear-mode fatigue crack.

  10. Mesh2d

    SciTech Connect

    Greg Flach, Frank Smith

    2011-12-31

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

  11. Mesh2d

    2011-12-31

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

  12. Controlled growth of 1D and 2D ZnO nanostructures on 4H-SiC using Au catalyst

    PubMed Central

    2014-01-01

    A perfect control of nanostructure growth is a prerequisite for the development of electronic and optoelectronic device/systems. In this article, we demonstrate the growth of various ZnO-derived nanostructures, including well-ordered arrays of high aspect ratio single crystalline nanowires with preferred growth direction along the [0001] axis, nanowalls, and hybrid nanowire-nanowall structures. The growths of the various ZnO nanostructures have been carried out on SiC substrates in a horizontal furnace, using Au thin film as catalyst. From experimental observations, we have ascribed the growth mechanisms of the different ZnO nanostructures to be a combination of catalytic-assisted and non-catalytic-assisted vapor–liquid-solid (VLS) processes. We have also found that the different ZnO nanoarchitectures' material evolution is governed by a Zn cluster drift effects on the SiC surface mainly driven by growth temperature. Au thin film thickness, growth time, and temperature are the parameters to optimize in order to obtain the different ZnO nanoarchitectures. PMID:25136283

  13. Vertical 2D Heterostructures

    NASA Astrophysics Data System (ADS)

    Lotsch, Bettina V.

    2015-07-01

    Graphene's legacy has become an integral part of today's condensed matter science and has equipped a whole generation of scientists with an armory of concepts and techniques that open up new perspectives for the postgraphene area. In particular, the judicious combination of 2D building blocks into vertical heterostructures has recently been identified as a promising route to rationally engineer complex multilayer systems and artificial solids with intriguing properties. The present review highlights recent developments in the rapidly emerging field of 2D nanoarchitectonics from a materials chemistry perspective, with a focus on the types of heterostructures available, their assembly strategies, and their emerging properties. This overview is intended to bridge the gap between two major—yet largely disjunct—developments in 2D heterostructures, which are firmly rooted in solid-state chemistry or physics. Although the underlying types of heterostructures differ with respect to their dimensions, layer alignment, and interfacial quality, there is common ground, and future synergies between the various assembly strategies are to be expected.

  14. Integrated modelling of island growth, stabilization and mode locking: consequences for NTM control on ITER

    NASA Astrophysics Data System (ADS)

    van den Brand, H.; de Baar, M. R.; Lopes Cardozo, N. J.; Westerhof, E.

    2012-09-01

    Full suppression of neoclassical tearing modes (NTMs) using electron cyclotron current drive (ECCD) should be reached before mode locking (stop of rotation) makes suppression impossible. For an ITER scenario 2 plasma, the similar time scales for locking and island growth necessitate the combined modelling of the growth of the mode and its slow down due to wall induced drag. Using such a model, the maximum allowed latency between the seeding of the mode and the start of ECCD deposition and maximum deviation in the radial position are determined. The maximum allowed latency is determined for two limiting models for island growth; the polarization model with wmarg = 2 cm, representing the worst case, and the transport model with wmarg = 6 cm, representing the best case. NTMs with seed island widths up to 9.5 cm and 12 cm for the 2/1 and the 3/2 NTM, respectively, are suppressible. The maximum allowed latency is 1.05 s and 2.95 s for the 2/1 and 3/2 NTM, respectively, for the worst case model. Radial misalignment should not exceed 7-10 mm for the 2/1 NTM and 5-16 mm for the 3/2 NTM depending on the model for island growth. As long as the alignment suffices, it does not reduce the maximum allowed latency. Mode locking has serious implications for any real-time NTM control system on ITER that aims to suppress NTMs by ECCD.

  15. High-resistance GaN epilayers with low dislocation density via growth mode modification

    NASA Astrophysics Data System (ADS)

    Xu, Z. Y.; Xu, F. J.; Wang, J. M.; Lu, L.; Yang, Z. J.; Wang, X. Q.; Shen, B.

    2016-09-01

    High-resistance GaN with low dislocation density adopting growth mode modification has been investigated by metalorganic chemical vapor deposition. The sheet resistance of the order of 1016 Ω/sq has been achieved at room temperature by diminishing the oxygen impurity level close to the substrate with an AlN blocking layer. Attributed to this method which offers more freedom to tailor the growth mode, a three-dimensional (3D) growth process is introduced by adjusting the growth pressure and temperature at the initial stage of the GaN epitaxy to improve the crystalline quality. The large 3D GaN grains formed during this period roughen the surface, and the following coalescence of the GaN grains causes threading dislocations bending, which finally remarkably reduces the dislocation density.

  16. Delamination growth behavior of a fabric reinforced laminated composite under Mode I fatigue

    SciTech Connect

    Atodaria, D.R.; Putatunda, S.K.; Mallick, P.K.

    1999-07-01

    The purpose of this study is to investigate the delamination growth behavior of a glass fabric reinforced laminated composite under Mode I fatigue loading and to examine the applicability of a new fatigue crack growth rate model to this material. In this study, double cantilever beam specimens were subjected to tension-tension cyclic loads with three different load ratios and the delamination growth rate was measured using the compliance method. The delamination growth rate was related to the strain energy release rate during fatigue cycling by a power law equation that takes into account not only the effect of the strain energy release rate range, but also the effect of delamination growth at various stages of loading using a weight average strain energy release rate. It was observed that this new model can represent the delamination growth rate of the fabric reinforced laminated composite at three different load ratios in a single unifying curve.

  17. Subcritical crack growth under mode I, II, and III loading for Coconino sandstone

    NASA Astrophysics Data System (ADS)

    Ko, Tae Young

    In systems subjected to long-term loading, subcritical crack growth is the principal mechanism causing the time-dependent deformation and failure of rocks. Subcritical crack growth is environmentally-assisted crack growth, which can allow cracks to grow over a long period of time at stresses far smaller than their failure strength and at tectonic strain rates. The characteristics of subcritical crack growth can be described by a relationship between the stress intensity factor and the crack velocity. This study presents the results of studies conducted to validate the constant stress-rate test for determining subcritical crack growth parameters in Coconino sandstone, compared with the conventional testing method, the double torsion test. The results of the constant stress-rate test are in good agreement with the results of double torsion test. More importantly, the stress-rate tests can determine the parameter A with a much smaller standard deviation than the double torsion test. Thus the constant stress-rate test seems to be both a valid and preferred test method for determining the subcritical crack growth parameters in rocks. We investigated statistical aspects of the constant stress-rate test. The effects of the number of tests conducted on the subcritical crack growth parameters were examined and minimum specimen numbers were determined. The mean and standard deviation of the subcritical crack growth parameters were obtained by randomly selecting subsets from the original strength data. In addition, the distribution form of the subcritical crack growth parameters and the relation between the parameter n and A were determined. We extended the constant stress-rate test technique to modes II and III subcritical crack growth in rocks. The experimental results of the modes I, II and III tests show that the values of the subcritical crack growth parameters are similar to each other. The subcritical crack growth parameter n value for Coconino sandstone has the range

  18. Growth of Daphnia magna exposed to mixtures of chemicals with diverse modes of action

    SciTech Connect

    Deneer, J.W.; Seinen, W.; Hermens, J.L.

    1988-02-01

    Concentrations causing inhibition of growth of Daphnia magna after 16 days of exposure were determined for nine chemicals that presumably act through different modes of action. The joint toxic effect of a mixture of these chemicals is found to be nonadditive.

  19. Mode 1 delamination growth in adhesively bonded joints under static and fatigue loads

    NASA Technical Reports Server (NTRS)

    Biswas, S. C.; Jeelani, S.

    1986-01-01

    The objective of this investigation was to characterize the pure mode 1 delamination growth in metal to metal adhesively bonded joints under static and fatigue loading conditions, using FM 73 adhesive. Double cantilever beam specimens (DCB) were used for pure mode 1 tests. Aluminum 2024-T3 adherends were bonded with FM 73 adhesive. Delamination was introduced during fabrication by inserting a Teflon film between the two adherends. The mode 1 strain energy release rate G sub I sub c was obtained directly from static DCB tests conducted in accordance with the ASTM designation D1876-12. Constant amplitude fatigue tests on DCB specimens were conducted to determine the relationship between delamination growth rate da/dN and strain energy release rate G sub I sub c for a pure mode 1 delamination growth. It is found that the debond propagation rate in adhesive joints using FM 73 is more sensitive to errors in design load than is typical crack growth rate in metallic structures.

  20. Computational comparison of mediated current generation capacity of Chlamydomonas reinhardtii in photosynthetic and respiratory growth modes.

    PubMed

    Mao, Longfei; Verwoerd, Wynand S

    2014-11-01

    Chlamydomonas reinhardtii possesses many potential advantages to be exploited as a biocatalyst in microbial fuel cells (MFCs) for electricity generation. In the present study, we performed computational studies based on flux balance analysis (FBA) to probe the maximum potential of C. reinhardtii for current output and identify the metabolic mechanisms supporting a high current generation in three different cultivation conditions, i.e., heterotrophic, photoautotrophic and mixotrophic growth. The results showed that flux balance limitations allow the highest current output for C. reinhardtii in the mixotrophic growth mode (2.368 A/gDW), followed by heterotrophic growth (1.141 A/gDW) and photoautotrophic growth the lowest (0.7035 A/gDW). The significantly higher mediated electron transfer (MET) rate in the mixotrophic mode is in complete contrast to previous findings for a photosynthetic cyanobacterium, and was attributed to the fact that for C. reinhardtii the photophosphorylation improved the efficiency of converting the acetate into biomass and NADH production. Overall, the cytosolic NADH-dependent current production was mainly associated with five reactions in both mixotrophic and photoautotrophic nutritional modes, whereas four reactions participated in the heterotrophic mode. The mixotrophic and photoautotrophic metabolisms were alike and shared the same set of reactions for maximizing current production, whereas in the heterotrophic mode, the current production was additionally contributed by the metabolic activities in the two organelles: glyoxysome and chloroplast. In conclusion, C. reinhardtii has a potential to be exploited in MFCs of MET mode to produce a high current output. PMID:24875305

  1. Growth mode and properties of Mn-Co-Ni-O NTC thermistor thin films deposited on MgO (100) substrate by laser MBE

    NASA Astrophysics Data System (ADS)

    Xie, Yahong; Kong, Wenwen; Ji, Guang; Gao, Bo; Yao, Jincheng; Chang, Aimin

    2014-12-01

    Mn1.56Co0.96Ni0.48O4-δ thin films were deposited on MgO (100) substrate using laser molecular beam epitaxy (LMBE) technique at the temperature range of 300-600°C under oxygen partial pressure of 5 × 10-3 Pa. The effect of growth temperature on microstructure and electrical properties as well as the growth mode were studied using XRD, RHEED, AFM and resistance-temperature measurements. The results showed that all prepared thin films underwent epitaxial growth along the single-(100) orientation direction of the MgO substrate from 3D-island mode to 2D layer-by-layer mode, and exhibited good crystallinity and NTC thermistor behavior. Their resistance at room temperature can be in the range of 10-50 MΩ together with a B-value of about 3300 K, which are desirable for a wide range of practical applications of the NTC thermistors.

  2. Growth and stabilization of drift-tearing modes in weakly collisional plasmas

    NASA Astrophysics Data System (ADS)

    Grasso\\ad{a}, D.; Ottaviani, M.; Porcelli\\ad{a}, F.

    2002-09-01

    In the limit where the electron drift-wave frequency exceeds the electron-ion collision frequency, drift-tearing modes are found to grow with a linear growth rate independent of resistivity and proportional to the product of the electron inertial skin depth and the ion sound Larmor radius. The stabilization of these modes in collisionless and semi-collisional regimes is investigated. The stabilization mechanism is related to the coupling and propagation of drift-acoustic perturbations away from the reconnecting mode-rational surface. Analytic and numerical solutions of the four-field reduced fluid model in the slab geometry approximation with constant electron temperature and negligible ion temperature are presented. The actual stability threshold can occur at values of the normalized tearing mode stability parameter Δ' as high as 102.\\pacs{52.35.P}} \\fnm{1}{Permanent address: Istituto Nazionale Fisica della Materia, Department of Energetics, Politecnico di Torino, Italy

  3. Abbreviated epitaxial growth mode (AGM) method for reducing cost and improving quality of LEDs and lasers

    DOEpatents

    Tansu, Nelson; Chan, Helen M; Vinci, Richard P; Ee, Yik-Khoon; Biser, Jeffrey

    2013-09-24

    The use of an abbreviated GaN growth mode on nano-patterned AGOG sapphire substrates, which utilizes a process of using 15 nm low temperature GaN buffer and bypassing etch-back and recovery processes during epitaxy, enables the growth of high-quality GaN template on nano-patterned AGOG sapphire. The GaN template grown on nano-patterned AGOG sapphire by employing abbreviated growth mode has two orders of magnitude lower threading dislocation density than that of conventional GaN template grown on planar sapphire. The use of abbreviated growth mode also leads to significant reduction in cost of the epitaxy. The growths and characteristics of InGaN quantum wells (QWs) light emitting diodes (LEDs) on both templates were compared. The InGaN QWs LEDs grown on the nano-patterned AGOG sapphire demonstrated at least a 24% enhancement of output power enhancement over that of LEDs grown on conventional GaN templates.

  4. In situ studies of the effect of silicon on GaN growth modes.

    SciTech Connect

    Munkholm, A.; Stephenson, G. B.; Eastman, J. A.; Auciello, O.; Murty, M. V. R.; Thompson, C.; Fini, P.; Speck, J. S.; DenBaars, S. P.; Northern Illinois Univ.; Univ. of California at Santa Barbara

    2000-12-01

    We present real-time X-ray scattering studies of the influence of silicon on the homoepitaxial growth mode of GaN grown by metal-organic vapor-phase epitaxy. Both annealing of Si-doped GaN and surface dosing of GaN with disilane are shown to change the mode of subsequent growth from step-flow to layer-by-layer. By comparing the growth behavior induced by doped layers which have been annealed to that induced by surface dosing, we extract an approximate diffusion coefficient for Si in GaN of 3.5 x 10{sup -18} cm{sup 2}/s at 810{sup o}C.

  5. Regularity in budding mode and resultant growth morphology of the azooxanthellate colonial scleractinian Tubastraea coccinea

    NASA Astrophysics Data System (ADS)

    Sentoku, A.; Ezaki, Y.

    2012-03-01

    Scleractinia exhibit a variety of growth forms, whether zooxanthellate or azooxanthellate, according to factors that control asexual reproduction and ensuing coral growth. The azooxanthellate branching scleractinian Dendrophyllia arbuscula shows regular modes of budding in terms of the locations of budding sites, the orientations of directive septa, and the inclination angle of budding throughout colonial growth. This study reports that such regularities are also found in the apparently different growth form of the massive dendrophylliid Tubastraea coccinea, which shows the following growth features: (1) the offsets (lateral corallites) always occur near four primary septa, except the two directive primary septa, meaning that the lateral corallites do not appear in the sectors of the two directive septa; (2) the two directive septa in lateral corallites tend to be oriented subperpendicular to the growth direction of the parental corallites; (3) the lateral corallites grow approximately diagonally upwards; and (4) these regularities are seen in the axial and derived lateral corallites among all generations during colony growth. Large differences in growth form are found between the branching D. arbuscula and massive T. coccinea, irrespective of the presence of specific regularities. It is likely that subtle modifications of certain parameters (e.g., budding interval, branch length, corallite size, and inclination angle of lateral corallites) have a strong effect on the overall growth morphology. A precise understanding of such regularities, which occur regardless of generation or taxonomic position, would contribute to understanding the "shape-controlling mechanism" of corals, which are an archetypal modular organism.

  6. Growth of nucleation mode particles in the summertime Arctic: a case study

    NASA Astrophysics Data System (ADS)

    Willis, Megan D.; Burkart, Julia; Thomas, Jennie L.; Köllner, Franziska; Schneider, Johannes; Bozem, Heiko; Hoor, Peter M.; Aliabadi, Amir A.; Schulz, Hannes; Herber, Andreas B.; Leaitch, W. Richard; Abbatt, Jonathan P. D.

    2016-06-01

    The summertime Arctic lower troposphere is a relatively pristine background aerosol environment dominated by nucleation and Aitken mode particles. Understanding the mechanisms that control the formation and growth of aerosol is crucial for our ability to predict cloud properties and therefore radiative balance and climate. We present an analysis of an aerosol growth event observed in the Canadian Arctic Archipelago during summer as part of the NETCARE project. Under stable and clean atmospheric conditions, with low inversion heights, carbon monoxide less than 80 ppbv, and black carbon less than 5 ng m-3, we observe growth of small particles, < 20 nm in diameter, into sizes above 50 nm. Aerosol growth was correlated with the presence of organic species, trimethylamine, and methanesulfonic acid (MSA) in particles ˜ 80 nm and larger, where the organics are similar to those previously observed in marine settings. MSA-to-sulfate ratios as high as 0.15 were observed during aerosol growth, suggesting an important marine influence. The organic-rich aerosol contributes significantly to particles active as cloud condensation nuclei (CCN, supersaturation = 0.6 %), which are elevated in concentration during aerosol growth above background levels of ˜ 100 to ˜ 220 cm-3. Results from this case study highlight the potential importance of secondary organic aerosol formation and its role in growing nucleation mode aerosol into CCN-active sizes in this remote marine environment.

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  9. Late-time quadratic growth in single-mode Rayleigh-Taylor instability.

    PubMed

    Wei, Tie; Livescu, Daniel

    2012-10-01

    The growth of the two-dimensional single-mode Rayleigh-Taylor instability (RTI) at low Atwood number (A=0.04) is investigated using Direct Numerical Simulations. The main result of the paper is that, at long times and sufficiently high Reynolds numbers, the bubble acceleration becomes stationary, indicating mean quadratic growth. This is contrary to the general belief that single-mode Rayleigh-Taylor instability reaches a constant bubble velocity at long times. At unity Schmidt number, the development of the instability is strongly influenced by the perturbation Reynolds number, defined as Rep≡λsqrt[Agλ/(1+A)]/ν. Thus, the instability undergoes different growth stages at low and high Rep. A new stage, chaotic development, was found at sufficiently high Rep values, after the reacceleration stage. During the chaotic stage, the instability experiences seemingly random acceleration and deceleration phases, as a result of complex vortical motions, with strong dependence on the initial perturbation shape (i.e., wavelength, amplitude, and diffusion thickness). Nevertheless, our results show that the mean acceleration of the bubble front becomes constant at late times, with little influence from the initial shape of the interface. As Rep is lowered to small values, the later instability stages, chaotic development, reacceleration, potential flow growth, and even the exponential growth described by linear stability theory, are subsequently no longer reached. Therefore, the results suggest a minimum Reynolds number and a minimum development time necessary to achieve all stages of single-mode RTI development, requirements which were not satisfied in the previous studies of single-mode RTI. PMID:23214698

  10. Electron-cyclotron maser emission - Relative growth and damping rates for different modes and harmonics. [of auroral kilometric radiation

    NASA Technical Reports Server (NTRS)

    Melrose, D. B.; Dulk, G. A.; Hewitt, R. G.

    1984-01-01

    The temporal growth rate and the number of e-folding growths are calculated and compared for the following wave modes due to a loss-cone-driven cyclotron maser: fundamental x, o, and z modes and second harmonic x and o modes. The dominant mode of the maser should be the fastest growing mode for a saturated maser and should be the mode with the greatest number of e-folding growths for an unsaturated maser; this mode is the fundamental x mode) for a plasma frequency to cyclotron frequency ratio of less than about 0.3; it is the z mode (or perhaps the fundamental o mode) for ratios between 0.3 and 1.0, and the z mode (or perhaps the second harmonic x mode) for ratios between 1.0 and 1.3. Two main points are made: the dominance of the z mode over the range of ratios considered and the very weak effect of cyclotron damping. Electron-cyclotron maser emission is seen as responsible for auroral kilometric radiation, decametric radio emission from Jupiter and Saturn, solar microwave spike bursts, and microwave emission from some flare stars.

  11. Mode of physical activity and self-efficacy in older adults: a latent growth curve analysis.

    PubMed

    McAuley, E; Katula, J; Mihalko, S L; Blissmer, B; Duncan, T E; Pena, M; Dunn, E

    1999-09-01

    A randomized controlled trial examined the effect of two physical activity modes on changes in self-efficacy over the course of a 12-month period in older, formerly sedentary adults (N = 174, M age = 65.5 years). Participants were randomized into either an aerobic activity group or a stretching and toning group. Structural equation modeling was employed to conduct multiple sample latent growth curve analyses of individual growth in exercise and physical self-efficacy over time. Results revealed a curvilinear growth pattern for both types of efficacy with increases occurring over the first 6 months followed by declines at the 6-month follow-up. There was a significant treatment by mean level growth interaction for exercise efficacy with both groups increasing over time, but the aerobic group evidenced a twofold increase in growth over the stretching group. Structural analyses indicated that frequency of exercise participation was a significant predictor of overall growth in efficacy, and improvements in fitness were only related to exercise efficacy growth in the stretching group. Findings are discussed in terms of social cognitive theory and further application of latent growth curve modeling to studies of physical activity effects in older adults. PMID:10542821

  12. Shear mode coupling and tilted grain growth of A1N thin films in BAW resonators.

    PubMed

    Martin, Fabrice; Jan, Marc-Etienne; Rey-Mermet, Samuel; Belgacem, Brahim; Su, Dong; Cantoni, Marco; Muralt, Paul

    2006-07-01

    Polycrystalline A1N thin films were deposited by RF reactive magnetron sputtering on Pt(111)/Ti electrode films. The substrates were tilted by an angle ranging from 40 degrees to 70 degrees with respect to the target normal. A low deposition temperature and a high sputter gas pressure were found ideal for tilted growth. The resulting grain tilt angle amounts to about half the substrate tilt angle. For coupling evaluation, 5 GHz solidly mounted resonator structures have been realized. The tilted grain A1N films exhibited a permittivity in the 9.5-10.5 range and loss tangent of 0.3%. Two shear modes as well as the longitudinal mode could be clearly identified. The coupling coefficient k2(eff) of the fundamental thickness shear mode (TS0) was found to be about 0.5%, which is compatible with a c-axis tilt of about 6 degrees. PMID:16889341

  13. The propagation and growth of whistler mode waves generated by electron beams in earth's bow shock

    NASA Technical Reports Server (NTRS)

    Tokar, R. L.; Gurnett, D. A.

    1985-01-01

    In this study, the propagation and growth of whistler mode waves generated by electron beams within earth's bow shock is investigated using a planar model for the bow shock and a model electron distribution function. Within the shock, the model electron distribution function possesses a field-aligned T greater than T beam that is directed toward the magnetosheath. Waves with frequencies between about 1 and 100 Hz with a wide range of wave normal angles are generated by the beam via Landau and anomalous cyclotron resonances. However, because the growth rate is small and because the wave packets traverse the shock quickly, these waves do not attain large amplitudes. Waves with frequencies between about 30 and 150 Hz with a wide range of wave normal angles are generated by the beam via the normal cyclotron resonance. The ray paths for most of these waves are directed toward the solar wind although some wave packets, due to plasma convection travel transverse to the shock normal. These wave packets grow to large amplitudes because they spend a long time in the growth region. The results suggest that whistler mode noise within the shock should increase in amplitude with increasing upstream theta sub Bn. The study provides an explanation for the origin of much of the whistler mode turbulence observed at the bow shock.

  14. Effect of adherend thickness and mixed mode loading on debond growth in adhesively bonded composite joints

    NASA Technical Reports Server (NTRS)

    Mangalgiri, P. D.; Johnson, W. S.; Everett, R. A., Jr.

    1986-01-01

    Symmetric and unsymmetric double cantilever beam (DCB) specimens were tested and analyzed to assess the effect of: (1) adherend thickness, and (2) a predominantly mode I mixed mode loading on cyclic debond growth and static fracture toughness. The specimens were made of unidirectional composite (T300/5208) adherends bonded together with EC3445 structural adhesive. The thickness was 8, 16, or 24 plies. The experimental results indicated that the static fracture toughness increases and the cyclic debond growth rate decreases with increasing adherend thickness. This behavior was related to the length of the plastic zone ahead of the debond tip. For the symmetric DCB specimens, it was further found that displacement control tests resulted in higher debond growth rates than did load control tests. While the symmetric DCB tests always resulted in cohesive failures in the bondline, the unsymmetric DCB tests resulted in the debond growing into the thinner adherend and the damage progressing as delamination in that adherend. This behavior resulted in much lower fracture toughness and damage growth rates than found in the symmetric DCB tests.

  15. Growth modes of thin films of ligand-free metal clusters

    SciTech Connect

    Dollinger, A.; Strobel, C. H.; Bleuel, H.; Marsteller, A.; Gantefoer, G.; Fairbrother, D. H.; Tang, Xin; Bowen, K. H.; Kim, Young Dok

    2015-05-21

    Size-selected Mo{sub n}{sup −}, W{sub n}{sup −}, and Fe{sub n}{sup −} cluster anions are deposited on a weakly interacting substrate (highly oriented pyrolytic graphite) and studied ex-situ using atomic force microscopy. Depending on size, three growth modes can be distinguished. Very small clusters consisting of less than 10–30 atoms behave similar to atoms and coalesce into 3-dimensional bulk-like islands. Medium sized clusters consisting of hundreds of atoms do not coalesce and follow a Stanski-Krastanov growth pattern. At low coverage, an almost perfect monolayer is formed. This is a new finding different from all previous studies on deposited metal clusters. For clusters with several thousands of atoms, the growth pattern again changes. At low coverage, the substrate is dotted with individual clusters, while at high coverage, the surface becomes extremely rough.

  16. Continuous monitoring of bacterial biofilm growth using uncoated Thickness-Shear Mode resonators

    NASA Astrophysics Data System (ADS)

    Castro, P.; Resa, P.; Durán, C.; Maestre, J. R.; Mateo, M.; Elvira, L.

    2012-12-01

    Quartz Crystal Microbalances (QCM) were used to nondestructively monitor in real time the microbial growth of the bacteria Staphylococcus epidermidis (S. epidermidis) in a liquid broth. QCM, sometimes referred to as Thickness-Shear Mode (TSM) resonators, are highly sensitive sensors not only able to measure very small mass, but also non-gravimetric contributions of viscoelastic media. These devices can be used as biosensors for bacterial detection and are employed in many applications including their use in the food industry, water and environment monitoring, pharmaceutical sciences and clinical diagnosis. In this work, three strains of S. epidermidis (which differ in the ability to produce biofilm) have been continuously monitored using an array of piezoelectric TSM resonators, at 37 °C in a selective culturing media. Microbial growth was followed by measuring the changes in the crystal resonant frequency and bandwidth at several harmonics. It was shown that microbial growth can be monitored in real time using multichannel and multiparametric QCM sensors.

  17. Development and Application of Benchmark Examples for Mode II Static Delamination Propagation and Fatigue Growth Predictions

    NASA Technical Reports Server (NTRS)

    Krueger, Ronald

    2011-01-01

    The development of benchmark examples for static delamination propagation and cyclic delamination onset and growth prediction is presented and demonstrated for a commercial code. The example is based on a finite element model of an End-Notched Flexure (ENF) specimen. The example is independent of the analysis software used and allows the assessment of the automated delamination propagation, onset and growth prediction capabilities in commercial finite element codes based on the virtual crack closure technique (VCCT). First, static benchmark examples were created for the specimen. Second, based on the static results, benchmark examples for cyclic delamination growth were created. Third, the load-displacement relationship from a propagation analysis and the benchmark results were compared, and good agreement could be achieved by selecting the appropriate input parameters. Fourth, starting from an initially straight front, the delamination was allowed to grow under cyclic loading. The number of cycles to delamination onset and the number of cycles during delamination growth for each growth increment were obtained from the automated analysis and compared to the benchmark examples. Again, good agreement between the results obtained from the growth analysis and the benchmark results could be achieved by selecting the appropriate input parameters. The benchmarking procedure proved valuable by highlighting the issues associated with choosing the input parameters of the particular implementation. Selecting the appropriate input parameters, however, was not straightforward and often required an iterative procedure. Overall the results are encouraging, but further assessment for mixed-mode delamination is required.

  18. Recovery of an oscillatory mode of batch yeast growth in water for a pure culture.

    PubMed

    Vadasz, A S; Vadasz, P; Abashar, M E; Gupthar, A S

    2001-12-30

    New experiments that we conducted show an oscillatory mode of batch yeast growth in water, for a pure culture of the T206 strain of Saccharomyces cerevisiae. The oscillations are damped over time, allowing the cell concentration to stabilize at the stationary equilibrium. A new proposed model that includes the complete cell growth dynamics is introduced and showed to recover the experimental oscillatory results. In addition the proposed model recovers effects that are frequently encountered in experiments such as a "Lag Phase" as well as an inflection point in the "ln curve" of the cell concentration. The proposed model recovers also the Logistic Growth Curve as a special case. For purposes of providing some interesting contrast we present additional experimental as well as computational results for the growth of the VIN7 strain of S. cerevisiae in a 5% grape juice medium. The latter indicates even stronger oscillations during the growth process. In order to capture experimentally the oscillatory growth behavior, very frequent readings are required (every 15-30 min) and the measurement process needs to be extended to longer than usual periods (over 250 h). PMID:11789940

  19. High divergent 2D grating

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Ma, Jianyong; Zhou, Changhe

    2014-11-01

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

  20. Single-mode Rayleigh-Taylor growth-rate measurements with the OMEGA laser system

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.; Verdon, C. P.; Meyerhofer, D. D.; Boehly, T. R.; Bradley, D. K.; Smalyuk, V. A.; Ofer, D.; McKenty, P. W.; Glendinning, S. G.; Kalantar, D. H.; Watt, R. G.; Gobby, P. L.; Willi, O.; Taylor, R. J.

    1997-04-01

    The results from a series of single-mode Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five to six 351-nm laser beams overlapped with total intensities up to 2.5×1014W/cm2. Experiments were performed with both 3-ns ramp and 3-ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600-μm-diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using through-foil radiography and was detected with an x-ray framing camera for CH targets with and without a foam buffer. The growth of both 31-μm and 60-μm wavelength perturbations was found to be in good agreement with ORCHID simulations when the experimental details, including noise, were included. The addition of a 30-mg/cc, 100-μm-thick polystyrene foam buffer layer resulted in reduced growth of the 31-μm perturbation and essentially unchanged growth for the 60-μm case when compared to targets without foam.

  1. Single-mode Rayleigh-Taylor growth-rate measurements with the OMEGA laser system

    SciTech Connect

    Knauer, J. P.; Verdon, C. P.; Meyerhofer, D. D.; Boehly, T. R.; Bradley, D. K.; Smalyuk, V. A.; Ofer, D.; McKenty, P. W.; Glendinning, S. G.; Kalantar, D. H.; Watt, R. G.; Gobby, P. L.; Willi, O.; Taylor, R. J.

    1997-04-15

    The results from a series of single-mode Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five to six 351-nm laser beams overlapped with total intensities up to 2.5x10{sup 14} W/cm{sup 2}. Experiments were performed with both 3-ns ramp and 3-ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600-{mu}m-diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using through-foil radiography and was detected with an x-ray framing camera for CH targets with and without a foam buffer. The growth of both 31-{mu}m and 60-{mu}m wavelength perturbations was found to be in good agreement with ORCHID simulations when the experimental details, including noise, were included. The addition of a 30-mg/cc, 100-{mu}m-thick polystyrene foam buffer layer resulted in reduced growth of the 31-{mu}m perturbation and essentially unchanged growth for the 60-{mu}m case when compared to targets without foam.

  2. Single-mode Rayleigh-Taylor growth-rate measurements with the OMEGA laser system

    SciTech Connect

    Knauer, J.P.; Verdon, C.P.; Meyerhofer, D.D.; Boehly, T.R.; Bradley, D.K.; Smalyuk, V.A.; Ofer, D.; McKenty, P.W.; Glendinning, S.G.; Kalantar, D.H.; Watt, R.G.; Gobby, P.L.; Willi, O.; Taylor, R.J.

    1997-04-01

    The results from a series of single-mode Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five to six 351-nm laser beams overlapped with total intensities up to 2.5{times}10{sup 14}W/cm{sup 2}. Experiments were performed with both 3-ns ramp and 3-ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4{percent}{endash}7{percent} over a 600-{mu}m-diam region defined by the 90{percent} intensity contour. The temporal growth of the modulation in optical depth was measured using through-foil radiography and was detected with an x-ray framing camera for CH targets with and without a foam buffer. The growth of both 31-{mu}m and 60-{mu}m wavelength perturbations was found to be in good agreement with {ital ORCHID} simulations when the experimental details, including noise, were included. The addition of a 30-mg/cc, 100-{mu}m-thick polystyrene foam buffer layer resulted in reduced growth of the 31-{mu}m perturbation and essentially unchanged growth for the 60-{mu}m case when compared to targets without foam. {copyright} {ital 1997 American Institute of Physics.}

  3. In situ growth and activity and modes of penetration of Escherichia coli in unconsolidated porous materials.

    PubMed Central

    Sharma, P K; McInerney, M J; Knapp, R M

    1993-01-01

    Statistically reliable data on the in situ rates of growth, substrate consumption, and product formation are required to test the validity of the mathematical models developed for microbially enhanced oil recovery and in situ bioremediation processes. A simple, replicable porous-core system that could be aseptically divided into sections at various times was developed to follow the kinetics of microbial growth and metabolism in situ. This core system was used to study the kinetics of growth and the mode of penetration of strains of Escherichia coli through anaerobic, nutrient-saturated, fine Ottawa sand (permeability of 7.0 microns2 and porosity of 37%) under static conditions. The in situ rate of growth of a wild-type, motile, chemotactic strain, RW262, was two times slower inside cores than it was in liquid cultures. The mode of metabolism of galactose by strain RW262 was not altered inside cores, as acetate was the only product detected either inside the cores or in liquid cultures. Without applied advective force, strain RW262 grew exponentially and moved through cores at a rate of about 0.1 m/day. The cell population moved through cores in a band-like fashion, as the front of the moving cells consisted of high cell concentrations (greater than 10(5) cells per ml). Until the breakthrough of the cells occurred, galactose consumption and acetate production were observed only in the proximal sections of the core, showing that the cell propagation preceded the complete depletion of the substrate or the accumulation of large amounts of products.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8285677

  4. Critical thickness of 2D to 3D transition in GexSi1-x/Si(001) system

    NASA Astrophysics Data System (ADS)

    Lozovoy, K. A.; Kokhanenko, A. P.; Voitsekhovskii, A. V.

    2016-07-01

    In this paper, Stranski-Krastanov growth of GexSi1-x epitaxial layers on the Si(001) surface is considered. Experimental investigations show that the moment of transition from 2D to 3D growth and the critical thickness of 2D layer at which this transition occurs play a key role during the synthesis of such materials. Among the most important parameters determining the peculiarities of the growth process and characteristics of emerging island ensembles are growth temperature and surface conditions (for example, the presence of surfactants). But existing theoretical models are not able to predict the values of the critical thickness in the whole range of growth temperatures and compositions x of solution for these systems. For the calculations of the critical thickness of transition from 2D to 3D growth, in this paper, a theoretical model based on general nucleation theory is proposed. This model is specified by taking into account dependencies of elastic modulus, lattices mismatch, and surface energy of the side facet on the composition x. As a result, dependencies of the critical thickness of Stranski-Krastanov transition on composition x and temperature are obtained. This allows one to determine conditions of transition from 2D to 3D growth mode in these systems. The simulated results explain experimentally observed results on temperature dependencies of the critical thickness for different germanium contents.

  5. Ductile opening-mode fracture by pore growth and coalescence during combustion alteration of siliceous mudstone

    NASA Astrophysics Data System (ADS)

    Eichhubl, Peter; Aydin, Atilla

    2003-01-01

    Opening-mode fractures with blunt tips and large maximum apertures are characteristic of clinker that formed by combustion alteration of siliceous mudstone. These fractures are inferred to result from pore growth and coalescence, with initially circular pores inherited from the diatomaceous protolith. Circular pores grow preferentially in an en-échelon arrangement and coalesce to elongate pores and blunt-tipped fractures by thinning and rupture of bridges between pores. Coalescence of overlapping en-échelon pores causes fracture propagation in a zig-zag path that is considered indicative of significant inelastic deformation outside the immediate vicinity of the fracture tips. This process of fracture formation by void growth and coalescence is inferred to result from solution mass transfer and possible bulk melt movement during partial melting of clinker. Chemical mass transfer provides a mechanism for extensive inelastic deformation in the surrounding host rock concurrent with fracturing that is considered characteristic of ductile fracture. The preferred elongation of coalescing pores and local rupture of pore bridges is explained by a tensile sintering stress due to the thermodynamic tendency of the system for energy minimization of solid and liquid surfaces. It is suggested that ductile fracture processes that are accompanied by extensive inelastic deformation lead to opening-mode fractures with large apertures in a variety of crustal settings including metamorphic and magmatic systems as well as in reactive diagenetic environments, thus affecting fracture-controlled transfer of heat and mass and the rheology of the Earth's crust.

  6. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  7. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  8. Finite-time normal mode disturbances and error growth during Southern Hemisphere blocking

    NASA Astrophysics Data System (ADS)

    Wei, Mozheng; Frederiksen, Jorgen S.

    2005-01-01

    The structural organization of initially random errors evolving in a barotropic tangent linear model, with time-dependent basic states taken from analyses, is examined for cases of block development, maturation and decay in the Southern Hemisphere atmosphere during April, November, and December 1989. The statistics of 100 evolved errors are studied for six-day periods and compared with the growth and structures of fast growing normal modes and finite-time normal modes (FTNMs). The amplification factors of most initially random errors are slightly less than those of the fastest growing FTNM for the same time interval. During their evolution, the standard deviations of the error fields become concentrated in the regions of rapid dynamical development, particularly associated with developing and decaying blocks. We have calculated probability distributions and the mean and standard deviations of pattern correlations between each of the 100 evolved error fields and the five fastest growing FTNMs for the same time interval. The mean of the largest pattern correlation, taken over the five fastest growing FTNMs, increases with increasing time interval to a value close to 0.6 or larger after six days. FTNM 1 generally, but not always, gives the largest mean pattern correlation with error fields. Corresponding pattern correlations with the fast growing normal modes of the instantaneous basic state flow are significant but lower than with FTNMs. Mean pattern correlations with fast growing FTNMs increase further when the time interval is increased beyond six days.

  9. Controlling the Growth Modes of Femtoliter Sessile Droplets Nucleating on Chemically Patterned Surfaces.

    PubMed

    Bao, Lei; Werbiuk, Zenon; Lohse, Detlef; Zhang, Xuehua

    2016-03-17

    Femtoliter droplet arrays on immersed substrates are essential elements in a broad range of advanced droplet-based technologies, such as light manipulation, sensing, and high throughput diagnosis. Solvent exchange is a bottom-up approach for producing those droplets from a pulse of oil oversaturation when a good solvent of the droplet liquid is displaced by a poor solvent. The position and arrangement of the droplets are regulated by chemical micropatterns on the substrate. Here we show experimentally and theoretically that the growth modes of droplets confined in planar micropatterns on the surface can be manipulated through the laminar flow of the solvent exchange. The control parameters are the area size of the micropatterns and the flow rate, and the observables are the contact angle and the final droplet volume. For a given pattern size, the Peclet number of the flow determines whether the growing droplets switch from an initial constant contact angle mode to a subsequent constant contact radius mode. Good agreement is achieved between the experimental results and our theoretical model that describes the dependence of the final droplet size on Pe. PMID:26938312

  10. An experimental study of CTOD for Mode I/Mode II stable crack growth in thin 2024-T3 aluminum specimens

    SciTech Connect

    Amstutz, B.E.; Sutton, M.A.; Dawicke, D.S.; Newman, J.C.

    1995-12-31

    An experimental study of crack tip opening displacement (CTOD) for Mode I/Mode II stable crack growth in thin sheet 2024-T3 aluminum has been conducted. To perform the experiments, an Arcan specimen and fixture was modified so that (1) slippage in the grips was eliminated, (2) large rotations of the fixture components were achievable and (3) bending stresses were minimized. Defining {Theta} to be the angle between the Mode I loading direction (perpendicular to the crack line) and the direction of applied loading, experimental results indicate that (a) for large amounts of crack extension, a {ge} 10mm, the value of CTOD at 1 mm behind the crack tip appears to approach a constant value of 0.1 mm for all modes of loading, (b) the direction of crack extension varied with applied mixed mode loading, (c) Mode I crack extension is predominant for 0{degree} {le} {Theta} {le} 60{degree}, (d) Mode II crack extension is predominant for 75{degree} {le} {Theta} {le} 90{degree} and (e) a transition zone exists for angles {Theta} near 75{degree}.

  11. AnisWave 2D

    2004-08-01

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

  12. 2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches

    SciTech Connect

    Hammer, J.H.; Eddleman, J.L.; Springer, P.T.

    1995-11-06

    Z-pinch implosions driven by the SATURN device at Sandia National Laboratory are modeled with a 2D radiation magnetohydrodynamic (MHD) code, showing strong growth of magneto-Rayleigh Taylor (MRT) instability. Modeling of the linear and nonlinear development of MRT modes predicts growth of bubble-spike structures that increase the time span of stagnation and the resulting x-ray pulse width. Radiation is important in the pinch dynamics keeping the sheath relatively cool during the run-in and releasing most of the stagnation energy. The calculations give x-ray pulse widths and magnitudes in reasonable agreement with experiments, but predict a radiating region that is too dense and radially localized at stagnation. We also consider peaked initial density profiles with constant imploding sheath velocity that should reduce MRT instability and improve performance. 2D krypton simulations show an output x-ray power > 80 TW for the peaked profile.

  13. On the abrupt growth dynamics of nonlinear resistive tearing mode and the viscosity effects

    SciTech Connect

    Ali, A.; Li, Jiquan; Kishimoto, Y.

    2014-05-15

    The nonlinear evolution of the resistive tearing mode exhibits an abrupt growth after an X-point collapse once the magnetic island exceeds a certain critical width Δ′w{sub c} for large instability parameter Δ′, leading to a current sheet formation [N. F. Loureiro et al., Phys. Rev. Lett. 95, 235003 (2005)]. In this work, we investigate the underlying mechanism of the X-point collapse as well as the current sheet formation including the viscosity effects, based on a secondary instability analysis. The secondary instability is excited due to the quasilinear current modification by the zonal current. In particular, it is identified that the current peaking effect is plausibly responsible for the onset of the X-point collapse and the current sheet formation, leading to the explosive growth of reconnected flux. In the presence of finite viscosity, the Δ′w{sub c} scaling with the resistivity gets modified. A transition behavior is revealed at P{sub r}≈1 for the viscosity dependence of Δ′w{sub c} and the linear tearing instability. However, the explosive growth seems to be independent of the viscosity in the magnetic Prandtl number P{sub r}<1 regime, while large viscosity plays a strong dissipation role.

  14. Extending non-fatigue Mode I subcritical crack growth data to subcritical fatigue crack growth: Demonstration of the equivalence of the Charles' law and Paris law exponents

    NASA Astrophysics Data System (ADS)

    Keanini, Russell; Eppes, Martha-Cary

    2016-04-01

    Paris's law connects fatigue-induced subcritical crack growth and fatigue loading. Environmentally-driven subcritical crack growth, while a random process, can be decomposed into a spectrum of cyclic processes, where each spectral component is governed by Paris's law. Unfortunately, almost no data exists concerning the Paris law exponent, m; rather, the great majority of existing sub-critical crack growth measurements on rock have been carried out via Mode I tensile tests, where corresponding data are generally correlated using Charles' law, and where the latter, similar to Paris's law, exposes a power law relationship between crack growth rate and stress intensity. In this study, a statistical argument is used to derive a simple, rigorous relationship between the all-important Paris law and Charles law exponents, m and n. This result has a significant practical implication: subcritical fatigue crack growth in rock, driven by various random environmental weathering processes can now be predicted using available Mode I stress corrosion indices, n.

  15. Epitaxial growth of highly-crystalline spinel ferrite thin films on perovskite substrates for all-oxide devices.

    PubMed

    Moyer, Jarrett A; Gao, Ran; Schiffer, Peter; Martin, Lane W

    2015-01-01

    The potential growth modes for epitaxial growth of Fe3O4 on SrTiO3 (001) are investigated through control of the energetics of the pulsed-laser deposition growth process (via substrate temperature and laser fluence). We find that Fe3O4 grows epitaxially in three distinct growth modes: 2D-like, island, and 3D-to-2D, the last of which is characterized by films that begin growth in an island growth mode before progressing to a 2D growth mode. Films grown in the 2D-like and 3D-to-2D growth modes are atomically flat and partially strained, while films grown in the island growth mode are terminated in islands and fully relaxed. We find that the optimal structural, transport, and magnetic properties are obtained for films grown on the 2D-like/3D-to-2D growth regime boundary. The viability for including such thin films in perovskite-based all-oxide devices is demonstrated by growing a Fe3O4/La0.7Sr0.3MnO3 spin valve epitaxially on SrTiO3. PMID:26030835

  16. Epitaxial growth of highly-crystalline spinel ferrite thin films on perovskite substrates for all-oxide devices

    PubMed Central

    Moyer, Jarrett A.; Gao, Ran; Schiffer, Peter; Martin, Lane W.

    2015-01-01

    The potential growth modes for epitaxial growth of Fe3O4 on SrTiO3 (001) are investigated through control of the energetics of the pulsed-laser deposition growth process (via substrate temperature and laser fluence). We find that Fe3O4 grows epitaxially in three distinct growth modes: 2D-like, island, and 3D-to-2D, the last of which is characterized by films that begin growth in an island growth mode before progressing to a 2D growth mode. Films grown in the 2D-like and 3D-to-2D growth modes are atomically flat and partially strained, while films grown in the island growth mode are terminated in islands and fully relaxed. We find that the optimal structural, transport, and magnetic properties are obtained for films grown on the 2D-like/3D-to-2D growth regime boundary. The viability for including such thin films in perovskite-based all-oxide devices is demonstrated by growing a Fe3O4/La0.7Sr0.3MnO3 spin valve epitaxially on SrTiO3. PMID:26030835

  17. Mixed-mode fatigue-crack growth thresholds in Ti-6Al-4V at high frequency

    SciTech Connect

    Campbell, J.P.; Ritchie, R.O.

    1999-10-22

    Multiaxial loading conditions exist at fatigue-critical locations within turbine engine components, particularly in association with fretting fatigue in the blade dovetail/disk contact section. For fatigue-crack growth in such situations, the resultant crack-driving force is a combination of the influence of a mode I (tensile opening) stress-intensity range, {Delta}K{sub I}, as well as mode II (in-plane shear) and/or mode III (anti-plane shear) stress-intensity ranges, {Delta}K{sub II} and {Delta}K{sub III}, respectively. For the case of the high-cycle fatigue of turbine-engine alloys, it is critical to quantify such behavior, as the extremely high cyclic loading frequencies ({approximately}1--2 kHz) and correspondingly short times to failure may necessitate a design approached based on the fatigue-crack growth threshold. Moreover, knowledge of such thresholds is required for accurate prediction of fretting fatigue failures. Accordingly, this paper presents the mixed-mode fatigue crack growth thresholds for mode I + II loading (phase angles from 0{degree} to 82{degree}) in a Ti-6Al-4V blade alloy. These results indicate that when fatigue-crack growth in this alloy is characterized in terms of the crack-driving force {Delta}G, which incorporates both the applied tensile and shear loading, the mode 1 fatigue-crack growth threshold is a lower bound (worst case) with respect to mixed-mode (I + II) crack-growth behavior.

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

    NASA Astrophysics Data System (ADS)

    Biser, Jeffrey M.

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

  19. Molecular mechanisms for the evolution of bacterial morphologies and growth modes

    PubMed Central

    Randich, Amelia M.; Brun, Yves V.

    2015-01-01

    Bacteria exhibit a rich diversity of morphologies. Within this diversity, there is a uniformity of shape for each species that is replicated faithfully each generation, suggesting that bacterial shape is as selectable as any other biochemical adaptation. We describe the spatiotemporal mechanisms that target peptidoglycan synthesis to different subcellular zones to generate the rod-shape of model organisms Escherichia coli and Bacillus subtilis. We then demonstrate, using the related genera Caulobacter and Asticcacaulis as examples, how the modularity of the core components of the peptidoglycan synthesis machinery permits repositioning of the machinery to achieve different growth modes and morphologies. Finally, we highlight cases in which the mechanisms that underlie morphological evolution are beginning to be understood, and how they depend upon the expansion and diversification of the core components of the peptidoglycan synthesis machinery. PMID:26106381

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

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Giurgiutiu, Victor

    2014-03-01

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

  1. Influence of surface processes and initial topography on lateral fold growth and fold linkage mode

    NASA Astrophysics Data System (ADS)

    Collignon, M.; Fernandez, N.; Kaus, B. J. P.

    2015-08-01

    Elongation of randomly distributed fold segments and their potential linkage are important for hydrocarbon exploration because it can greatly influence the morphology of the reservoir and both migration and accumulation of hydrocarbons in antiformal traps. Here we study the effects of surface processes and the presence of a topographic slope on the different linkage modes that can occur, and how these parameters affect the required horizontal offset for perturbations to link. The proposed numerical model represents a sedimentary cover detached over a much weaker basal décollement layer. The upper surface is modified by mass redistribution, which is achieved by a combination of fluvial and hillslope processes. Several series of simulations were performed: (1) without surface processes or regional slope, (2) with regional slope only, (3) with fluvial incision and hillslope processes, and (4) with hillslope processes only. Model results show that the presence of a regional slope reduces the critical distance required for the transition between linkage and no linkage modes, whereas erosion and redeposition of sediments, on the contrary, increase this distance. The location of the saddle point, where fold segments link, and its vertical distance to the crests of the anticlines are different compared to the case without erosion or initial topographic slope, which potentially can affect the morphology of hydrocarbon traps. Moreover, both erosion and redeposition of sediments enhance the fold elongation (growth along the fold axis), once the erosion velocity exceeds the folding velocity. Model results have been compared to the Zagros Fold Belt.

  2. Experimental and Computational Investigation of Biofilm Formation by Rhodopseudomonas palustris Growth under Two Metabolic Modes.

    PubMed

    Kernan, Chase; Chow, Philicia P; Christianson, Rebecca J; Huang, Jean

    2015-01-01

    We examined biofilms formed by the metabolically versatile bacterium Rhodopseudomonas palustris grown via different metabolic modes. R. palustris was grown in flow cell chambers with identical medium conditions either in the presence or absence of light and oxygen. In the absence of oxygen and the presence of light, R. palustris grew and formed biofilms photoheterotrophically, and in the presence of oxygen and the absence of light, R. palustris grew and formed biofilms heterotrophically. We used confocal laser scanning microscopy and image analysis software to quantitatively analyze and compare R. palustris biofilm formation over time in these two metabolic modes. We describe quantifiable differences in structure between the biofilms formed by the bacterium grown heterotrophically and those grown photoheterotrophically. We developed a computational model to explore ways in which biotic and abiotic parameters could drive the observed biofilm architectures, as well as a random-forest machine-learning algorithm based on structural differences that was able to identify growth conditions from the confocal imaging of the biofilms with 87% accuracy. Insight into the structure of phototrophic biofilms and conditions that influence biofilm formation is relevant for understanding the generation of biofilm structures with different properties, and for optimizing applications with phototrophic bacteria growing in the biofilm state. PMID:26087200

  3. Experimental and Computational Investigation of Biofilm Formation by Rhodopseudomonas palustris Growth under Two Metabolic Modes

    PubMed Central

    Kernan, Chase; Chow, Philicia P.; Christianson, Rebecca J.; Huang, Jean

    2015-01-01

    We examined biofilms formed by the metabolically versatile bacterium Rhodopseudomonas palustris grown via different metabolic modes. R. palustris was grown in flow cell chambers with identical medium conditions either in the presence or absence of light and oxygen. In the absence of oxygen and the presence of light, R. palustris grew and formed biofilms photoheterotrophically, and in the presence of oxygen and the absence of light, R. palustris grew and formed biofilms heterotrophically. We used confocal laser scanning microscopy and image analysis software to quantitatively analyze and compare R. palustris biofilm formation over time in these two metabolic modes. We describe quantifiable differences in structure between the biofilms formed by the bacterium grown heterotrophically and those grown photoheterotrophically. We developed a computational model to explore ways in which biotic and abiotic parameters could drive the observed biofilm architectures, as well as a random-forest machine-learning algorithm based on structural differences that was able to identify growth conditions from the confocal imaging of the biofilms with 87% accuracy. Insight into the structure of phototrophic biofilms and conditions that influence biofilm formation is relevant for understanding the generation of biofilm structures with different properties, and for optimizing applications with phototrophic bacteria growing in the biofilm state. PMID:26087200

  4. GISAXS studies of initial growth mode and nanostructure of bulk heterojunction layers in planar type metal pthanlocyanine molecules

    NASA Astrophysics Data System (ADS)

    Kim, Hyo Jung; Kim, Ji Whan; Lee, Hyun Hwi; Lee, Byeondu; Kim, Jang-Joo

    2012-09-01

    ZnPc and CuPc molecules stacked similar way in the film, but showed different growth modes in thermal evaporation. The distribution of CuPc crystals did not change by the film thickness, whereas the distribution of ZnPc became random as the increase of the film thickness. The disc type nanograins of CuPc were quite regularly distributed at the initial growth regime and the regular distribution of nanograins was kept during the film growth. On the other hand, ZnPc consisted in ellipsoid shaped nanograins and the distribution of nanograins was not regular in the initial growth regime. The irregular distribution of nanograins changed to the regular mode at the later growth regime by showing structure factor in GISAXS measurement. The different initial nanograin distribution in ZnPc and CuPc was related to the different nanostructure in the mixed layer with C60 to form the bulk heterojunction.

  5. Explicit 2-D Hydrodynamic FEM Program

    1996-08-07

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

  6. [Methods for extraction of exopolymeric complex in plankton and biofilm growth mode of Stenotrophomonas maltophilia 22M].

    PubMed

    Boretskaia, M A; Suslova, O S

    2013-01-01

    The optimal methods for the extraction of exopolymeric complex (EPS) of Stenotrophomonas maltophilia 22M was determined. That EPS was synthesized in plankton and biofilm growth mode on the mild steel surface. It is desirable to use different physical and chemical methods for studying the EPS composition (carbohydrates and proteins) depending on the bacteria growth mode. In this way the interaction with ion exchange resin was the most effective for plankton growth mode to determine the maximum amount of carbohydrates (9.5 microg/ml), and the impact of heating to determine protein (3.9 microg/ml). For EPS biofilm in order to obtain maximum amount of carbohydrate it is desirable to use heating (30 microg/ml) and centrifugation (35 microg/ml). It is recommended to determine protein in the biofilm EPS after treatment with heating (3.75 microg/ml) and centrifugation (3.75 microg/ml). PMID:23720963

  7. Mode of growth of bacterial pathogens in chronic polymicrobial human osteomyelitis.

    PubMed Central

    Marrie, T J; Costerton, J W

    1985-01-01

    Direct examination of material from two cases of persistent (2 and 60 years) osteomyelitis by morphological and culture techniques showed that the pathogens comprised several bacterial species whose cells grew predominantly in discrete exopolysaccharide-enclosed microcolonies made up of a single bacterial morphotype. Bacterial microcolonies were seen between tissue elements in infected connective tissue, and the microcolonies adherent to bone surfaces coalesced to form extensive biofilms that occluded the surfaces of dead bone in sequestrae. Decalcification techniques were required to examine the interior of infected bone, but recognizable remnants were associated with very large amounts of fibrous, ruthenium red-stained material. All bacterial growth in these persistent infections occurred within an intercellular matrix, and some elements of this matrix, which was fibrous in transmission electron microscopy and amorphous in scanning electron microscopy, were associated with the surfaces of bacterial cells in a manner that suggested their production by these organisms. All of the implications of this microcolony mode of bacterial growth in osteomyelitis, and in other chronic bacterial diseases, have yet to be determined. Images PMID:4066923

  8. Magnetorotational Instability: Nonmodal Growth and the Relationship of Global Modes to the Shearing Box

    SciTech Connect

    J Squire, A Bhattacharjee

    2014-07-01

    We study the magnetorotational instability (MRI) (Balbus & Hawley 1998) using non-modal stability techniques.Despite the spectral instability of many forms of the MRI, this proves to be a natural method of analysis that is well-suited to deal with the non-self-adjoint nature of the linear MRI equations. We find that the fastest growing linear MRI structures on both local and global domains can look very diff erent to the eigenmodes, invariably resembling waves shearing with the background flow (shear waves). In addition, such structures can grow many times faster than the least stable eigenmode over long time periods, and be localized in a completely di fferent region of space. These ideas lead – for both axisymmetric and non-axisymmetric modes – to a natural connection between the global MRI and the local shearing box approximation. By illustrating that the fastest growing global structure is well described by the ordinary diff erential equations (ODEs) governing a single shear wave, we find that the shearing box is a very sensible approximation for the linear MRI, contrary to many previous claims. Since the shear wave ODEs are most naturally understood using non-modal analysis techniques, we conclude by analyzing local MRI growth over finite time-scales using these methods. The strong growth over a wide range of wave-numbers suggests that non-modal linear physics could be of fundamental importance in MRI turbulence (Squire & Bhattacharjee 2014).

  9. The dynamics of neutrino-driven supernova explosions after shock revival in 2D and 3D

    NASA Astrophysics Data System (ADS)

    Müller, B.

    2015-10-01

    We study the growth of the explosion energy after shock revival in neutrino-driven explosions in two and three dimensions (2D/3D) using multi-group neutrino hydrodynamics simulations of an 11.2 M⊙ star. The 3D model shows a faster and steadier growth of the explosion energy and already shows signs of subsiding accretion after one second. By contrast, the growth of the explosion energy in 2D is unsteady, and accretion lasts for several seconds as confirmed by additional long-time simulations of stars of similar masses. Appreciable explosion energies can still be reached, albeit at the expense of rather high neutron star masses. In 2D, the binding energy at the gain radius is larger because the strong excitation of downward-propagating g modes removes energy from the freshly accreted material in the downflows. Consequently, the mass outflow rate is considerably lower in 2D than in 3D. This is only partially compensated by additional heating by outward-propagating acoustic waves in 2D. Moreover, the mass outflow rate in 2D is reduced because much of the neutrino energy deposition occurs in downflows or bubbles confined by secondary shocks without driving outflows. Episodic constriction of outflows and vertical mixing of colder shocked material and hot, neutrino-heated ejecta due to Rayleigh-Taylor instability further hamper the growth of the explosion energy in 2D. Further simulations will be necessary to determine whether these effects are generic over a wider range of supernova progenitors.

  10. Island growth in the atomic layer deposition of zirconium oxide and aluminum oxide on hydrogen-terminated silicon: Growth mode modeling and transmission electron microscopy

    SciTech Connect

    Puurunen, Riikka L.; Vandervorst, Wilfried; Besling, Wim F. A.; Richard, Olivier; Bender, Hugo; Conard, Thierry; Zhao Chao; Delabie, Annelies; Caymax, Matty; Gendt, Stefan de; Heyns, Marc; Viitanen, Minna M.; Ridder, Marco de; Brongersma, Hidde H.; Tamminga, Yde; Dao, Thuy; Win, Toon de; Verheijen, Marcel; Kaiser, Monja; Tuominen, Marko

    2004-11-01

    Atomic layer deposition (ALD) is used in applications where inorganic material layers with uniform thickness down to the nanometer range are required. For such thicknesses, the growth mode, defining how the material is arranged on the surface during the growth, is of critical importance. In this work, the growth mode of the zirconium tetrachloride/water and the trimethyl aluminum/water ALD process on hydrogen-terminated silicon was investigated by combining information on the total amount of material deposited with information on the surface fraction of the material. The total amount of material deposited was measured by Rutherford backscattering, x-ray fluorescence, and inductively coupled plasma-optical emission spectroscopy, and the surface fractions by low-energy ion scattering. Growth mode modeling was made assuming two-dimensional growth or random deposition (RD), with a 'shower model' of RD recently developed for ALD. Experimental surface fractions of the ALD-grown zirconium oxide and aluminum oxide films were lower than the surface fractions calculated assuming RD, suggesting the occurrence of island growth. Island growth was confirmed with transmission electron microscopy (TEM) measurements, from which the island size and number of islands per unit surface area could also be estimated. The conclusion of island growth for the aluminum oxide deposition on hydrogen-terminated silicon contradicts earlier observations. In this work, physical aluminum oxide islands were observed in TEM after 15 ALD reaction cycles. Earlier, thicker aluminum oxide layers have been analyzed, where islands have not been observed because they have already coalesced to form a continuous film. The unreactivity of hydrogen-terminated silicon surface towards the ALD reactants, except for reactive defect areas, is proposed as the origin of island growth. Consequently, island growth can be regarded as 'undesired surface-selective ALD'.

  11. Stacking up 2D materials

    NASA Astrophysics Data System (ADS)

    Mayor, Louise

    2016-05-01

    Graphene might be the most famous example, but there are other 2D materials and compounds too. Louise Mayor explains how these atomically thin sheets can be layered together to create flexible “van der Waals heterostructures”, which could lead to a range of novel applications.

  12. A plane stress finite element model for elastic-plastic mode I/II crack growth

    NASA Astrophysics Data System (ADS)

    James, Mark Anthony

    A finite element program has been developed to perform quasi-static, elastic-plastic crack growth simulations. The model provides a general framework for mixed-mode I/II elastic-plastic fracture analysis using small strain assumptions and plane stress, plane strain, and axisymmetric finite elements. Cracks are modeled explicitly in the mesh. As the cracks propagate, automatic remeshing algorithms delete the mesh local to the crack tip, extend the crack, and build a new mesh around the new tip. State variable mapping algorithms transfer stresses and displacements from the old mesh to the new mesh. The von Mises material model is implemented in the context of a non-linear Newton solution scheme. The fracture criterion is the critical crack tip opening displacement, and crack direction is predicted by the maximum tensile stress criterion at the crack tip. The implementation can accommodate multiple curving and interacting cracks. An additional fracture algorithm based on nodal release can be used to simulate fracture along a horizontal plane of symmetry. A core of plane strain elements can be used with the nodal release algorithm to simulate the triaxial state of stress near the crack tip. Verification and validation studies compare analysis results with experimental data and published three-dimensional analysis results. Fracture predictions using nodal release for compact tension, middle-crack tension, and multi-site damage test specimens produced accurate results for residual strength and link-up loads. Curving crack predictions using remeshing/mapping were compared with experimental data for an Arcan mixed-mode specimen. Loading angles from 0 degrees to 90 degrees were analyzed. The maximum tensile stress criterion was able to predict the crack direction and path for all loading angles in which the material failed in tension. Residual strength was also accurately predicted for these cases.

  13. Influence of supersaturation and spontaneous catalyst formation on the growth of PbS wires: toward a unified understanding of growth modes.

    PubMed

    Nichols, Patricia L; Sun, Minghua; Ning, Cun-Zheng

    2011-11-22

    High quality stoichiometric lead sulfide (PbS) wires were synthesized by a simple chemical vapor deposition (CVD) process using pure PbS powder as the material source. Growth mechanisms were systematically investigated under various growth conditions, with three modes of growth identified: direct vapor-liquid-solid (VLS) wire growth nucleating from the substrate surface, bulk PbS crystallites by vapor-solid (VS) deposition, and subsequent VLS growth nucleating on top of the bulk deposition through spontaneously formed catalyst particles. Furthermore, we found that these growth modes can be organized in terms of different levels of supersaturation, with VS bulk deposition dominating at high supersaturation and VLS wire growth on the substrate dominating at low supersaturation. At intermediate supersaturation, the bulk VS deposition can form larger crystallites with domains of similarly oriented wires extending from the flat facets. Both predeposited catalysts and spontaneously formed Pb particles were observed as nucleation catalysts, and their interplay leads to various interesting growth scenarios such as reversely tapered growth with increasing diameter. The VLS growth mechanism was confirmed by the presence of Pb-rich caps revealed in an elaborate cross-sectional transmission electron microscopy (TEM) experiment after focused ion beam milling in a modified lift-out procedure. Temperature-dependent photoluminescence (PL) of PbS wires was performed in the mid-infrared wavelength range for the first time, demonstrating strong light emission from band edge, blue-shifted with increasing temperature. The high optical quality of PbS wires may lead to important applications in mid-infrared photonics. The substrate growth temperature as low as 400 °C allows for silicon-compatible processing for integrated optoelectronics applications. PMID:21981350

  14. MOSS2D V1

    2001-01-31

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

  15. Dissipation and diamagnetic effects on the interchange mode growth rate and rotation in reduced magnetohydrodynamics applied to stellarators

    NASA Astrophysics Data System (ADS)

    Nicolas, T.; Ichiguchi, K.

    2016-02-01

    The results of a reduced magnetohydrodynamic model for the interchange mode in a stellarator are reported. The model is based on Strauss equations, with the addition of resistivity, viscosity and perpendicular heat conductivity on the one hand, and ion and electron diamagnetic effects on the other hand. The ideally unstable and stable mode growth rate and frequency are studied. The main result is that the ideally unstable mode can rotate in the electron direction even in the absence of electron diamagnetic effects, due to a linear bifurcation caused by the heat conductivity. The presence of the bifurcation is explained analytically. The diamagnetic effects can be destabilizing. For the ideally stable (resistive) mode, we find that the presence of viscosity and heat conductivity causes rotation in the electron direction in the case where {{T}e}={{T}i} .

  16. Rate-dependent mode I interlaminar crack growth mechanisms in graphite/epoxy and graphite/PEEK

    NASA Technical Reports Server (NTRS)

    Gillespie, J. W., Jr.; Carlsson, L. A.; Smiley, A. J.

    1987-01-01

    In this paper the mode I fracture behavior of graphite/epoxy and graphite/PEEK composites is examined over four decades of crosshead rates (0.25-250 mm/min). Straight-sided double-cantilever-beam specimens consisting of unidirectional laminates were tested at room temperature. For graphite/epoxy the load-deflection response was linear to fracture, and stable slow crack growth initiating at the highest load level was observed for all rates tested. In contrast, mode I crack growth in the graphite/PEEK material was often unstable and showed stick-slip behavior. Subcritical crack growth occurring prior to the onset of fracture was observed at intermediate displacement rates. A mechanism for the fracture behavior of the graphite/PEEK material (based on viscoelastic, plastic, and microcrack coalescence in the process zone) is proposed and related to the observed rate-dependent phenomena.

  17. Mechanism of selective area growth of GaN nanorods by pulsed mode metalorganic chemical vapor deposition

    SciTech Connect

    Lin, Yen-Ting; Yeh, Ting-Wei; Dapkus, P. Daniel

    2012-10-23

    The growth mechanism for the formation of GaN nanorods using metalorganic chemical vapor deposition (MOCVD) selective area growth by pulsed source injection is proposed. The pulsed mode procedure and the kinetic model are discussed and experiments performed to support the model are described. The achievement of rod shape nanostructures grown by the pulsed mode can be attributed to two mechanisms: (1) the differences in the adsorption/desorption behavior of Ga adatoms on the c-plane (0001) and the boundary m-planes $\\{ 1\\bar {1}0 0\\} $, and (2) the growth behavior of the semi-polar planes (especially the semi-polar $\\{ 1\\bar {1}0 1\\} $ plane).

  18. A Novel Method for Characterizing Fatigue Delamination Growth Under Mode I Using the Double Cantilever Beam Specimen

    NASA Technical Reports Server (NTRS)

    Carvalho, Nelson; Murri, G.

    2014-01-01

    A novel method is proposed to obtain Mode I delamination growth rate from a Double Cantilever Beam (DCB) specimen. In the proposed method, Unidirectional (UD) DCB specimens are tested in fatigue at different initial maximum energy release rates levels. The growth rate data obtained in the first increments of crack growth at each maximum energy release rate level are used to generate a Paris Law equation, which characterizes delamination growth rate without fiber-bridging, and can also be used to determine a delamination onset curve. The remaining delamination growth rate data from each test are used to determine a modified Paris law, which characterizes the delamination growth rate in a DCB specimen, explicitly accounting for fiber-bridging. The proposed expression captures well the scatter in experimental data obtained using the DCB specimens, suggesting its adequacy. The Paris Law characterizing delamination growth rate without fiber-bridging predicts higher delamination growth rates for the same maximum energy release rate applied, leading to a conservative estimate for delamination growth. This is particularly relevant, since in generic ply interfaces, fiber-bridging is less predominant than in UD DCB specimens. Failing to account for fiber-bridging in UD DCB specimens may underestimate the delamination growth rate, yielding non-conservative predictions.

  19. Nanoimprint lithography: 2D or not 2D? A review

    NASA Astrophysics Data System (ADS)

    Schift, Helmut

    2015-11-01

    Nanoimprint lithography (NIL) is more than a planar high-end technology for the patterning of wafer-like substrates. It is essentially a 3D process, because it replicates various stamp topographies by 3D displacement of material and takes advantage of the bending of stamps while the mold cavities are filled. But at the same time, it keeps all assets of a 2D technique being able to pattern thin masking layers like in photon- and electron-based traditional lithography. This review reports about 20 years of development of replication techniques at Paul Scherrer Institut, with a focus on 3D aspects of molding, which enable NIL to stay 2D, but at the same time enable 3D applications which are "more than Moore." As an example, the manufacturing of a demonstrator for backlighting applications based on thermally activated selective topography equilibration will be presented. This technique allows generating almost arbitrary sloped, convex and concave profiles in the same polymer film with dimensions in micro- and nanometer scale.

  20. From weakly to strongly interacting 2D Fermi gases

    NASA Astrophysics Data System (ADS)

    Dyke, Paul; Fenech, Kristian; Lingham, Marcus; Peppler, Tyson; Hoinka, Sascha; Vale, Chris

    2014-05-01

    We study ultracold 2D Fermi gases of 6Li formed in a highly oblate trapping potential. The potential is generated by a cylindrically focused, blue detuned TEM01 mode laser beam. Weak magnetic field curvature provides highly harmonic confinement in the radial direction and we can readily produce single clouds with an aspect ratio of 230. Our experiments investigate the dimensional crossover from 3D to 2D for a two component Fermi gas in the Bose-Einstein Condensate to Bardeen Cooper Schrieffer crossover. Observation of an elbow in measurements of the cloud width vs. atom number is consistent with populating only the lowest transverse harmonic oscillator state for weak attractive interactions. This measurement is extended to the strongly interacting region using the broad Feshbach resonance at 832 G. We also report our progress towards measurement of the 2D equation of state for an interacting 2D Fermi gas via in-situ absorption imaging.

  1. Classical m/n = 2/1 Tearing Mode Stability Based on Initial Island Growth Rate of Neoclassical Tearing Modes in DIII-D ITER Baseline Scenario Discharges

    NASA Astrophysics Data System (ADS)

    La Haye, R. J.; Jackson, G. L.; Luce, T. C.; Meneghini, O.; Olofsson, K. E. J.; Turco, F.; Solomon, W. M.

    2014-10-01

    Deleterious m/n = 2/1 tearing modes appear in some slowly evolving ITER baseline scenario DIII-D discharges. The destabilization is here interpreted as due to an initially positive (destabilizing) classical tearing index. Examples of 2/1 tearing occurring after at least 3 seconds into discharges are analyzed. Island width evolution is evaluated by the Mirnov magnetic probe arrays using the motional Stark effect EFIT equilibrium reconstructions and is calibrated by the electron cyclotron emission (ECE) diagnostic. The magnetics analysis code EIGSPEC is used to sort out multiple modes and determine the precise point at which the m/n = 2/1 mode begins to grow. The classical stability index is determined from the modified Rutherford equation (MRE) by taking the helically perturbed bootstrap components (including both curvature and small island effects) and subtracting from the initial normalized island growth rate. The data is well described by the imbalance of the sum of the destabilizing classical tearing and the helically perturbed bootstrap current terms with the sum of the stabilizing curvature and ``ion polarization'' effects. Comparison of the empirically determined classical index will be made with that from the linear stability code PEST3 using kinetic EFITs from experiment. This work supported by the US DOE under DE-FC02-04ER54698, DE-AC05-06-OR23100, DE-FG02-04ER54761, DE-AC02-09CH11466.

  2. Microscale 2D separation systems for proteomic analysis

    PubMed Central

    Xu, Xin; Liu, Ke; Fan, Z. Hugh

    2012-01-01

    Microscale 2D separation systems have been implemented in capillaries and microfabricated channels. They offer advantages of faster analysis, higher separation efficiency and less sample consumption than the conventional methods, such as liquid chromatography (LC) in a column and slab gel electrophoresis. In this article, we review their recent advancement, focusing on three types of platforms, including 2D capillary electrophoresis (CE), CE coupling with capillary LC, and microfluidic devices. A variety of CE and LC modes have been employed to construct 2D separation systems via sophistically designed interfaces. Coupling of different separation modes has also been realized in a number of microfluidic devices. These separation systems have been applied for the proteomic analysis of various biological samples, ranging from a single cell to tumor tissues. PMID:22462786

  3. Influence of modes of metal transfer on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals

    SciTech Connect

    Mukherjee, Manidipto; Saha, Saptarshi; Pal, Tapan Kumar; Kanjilal, Prasanta

    2015-04-15

    The present study elaborately discussed the effect of different modes of metal transfer (i.e., short circuit mode, spray mode and pulse mode) on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals. Electron backscattered diffraction (EBSD) analysis was used to study the grain growth direction and grain structure in weld metals. The changes in grain structure and grain growth direction were found to be essentially varied with the weld pool shape and acting forces induced by modes of metal transfer at a constant welding speed. Short circuit mode of metal transfer owing to higher Marangoni force (M{sub a}) and low electromagnetic force (R{sub m}) promotes the lower weld pool volume (Γ) and higher weld pool maximum radius (r{sub m}). Short circuit mode also shows curved and tapered columnar grain structures and the grain growth preferentially occurred in <001> direction. In contrast, spray mode of metal transfer increases the Γ and reduces the r{sub m} values due to very high R{sub m} and typically reveals straight and broad columnar grain structures with preferential growth direction in <111>. In the pulse mode of metal transfer relatively high M{sub a} and R{sub m} simultaneously increase the weld pool width and the primary penetration which might encourage relatively complex grain growth directions in the weld pool and cause a shift of major intensity from <001> to <111> direction. It can also be concluded that the fusion zone grain structure and direction of grain growth are solely dependent on modes of metal transfer and remain constant for a particular mode of metal transfer irrespective of filler wire used. - Highlights: • Welded joints of LNiASS were prepared by varying modes of metal transfer. • Weld pool shape, grain structure and grain growth direction were studied. • Short circuit mode shows curved and tapered grain growth in <001> direction. • Spray mode shows straight and broad columnar grain growth

  4. Lack of synchronization between iron uptake and cell growth leads to iron overload in Saccharomyces cerevisiae during post-exponential growth modes

    PubMed Central

    Park, Jinkyu; McCormick, Sean P.; Chakrabarti, Mrinmoy; Lindahl, Paul A.

    2014-01-01

    Fermenting cells growing exponentially on rich (YPAD) medium transitioned to a slow-growing state as glucose levels declined and their metabolism shifted to respiration. During exponential growth, Fe import and cell growth rates were matched, affording an approximately invariant cellular Fe concentration. During the transitionary period, the high-affinity Fe import rate declined slower than the cell growth rate declined, causing Fe to accumulate, initially as FeIII oxyhydroxide nanoparticles but eventually as mitochondrial and vacuolar Fe. Once in slow-growth mode, Fe import and cell growth rates were again matched, and the cellular Fe concentration was again approximately invariant. Fermenting cells grown on minimal medium (MM) grew more slowly during exponential phase and transitioned to a true stationary state as glucose levels declined. The Fe concentration of MM cells that just entered stationary state was similar to that of YPAD cells, but MM cells continued to accumulate Fe in stationary state. Fe initially accumulated as nanoparticles and high-spin FeII species, but vacuolar FeIII also eventually accumulated. Surprisingly, Fe-packed 5-day-old MM cells suffered no more ROS damage than younger cells, suggesting that Fe concentration alone does not accurately predict the extent of ROS damage. The mode and rate of growth at the time of harvesting dramatically affected cellular Fe content. A mathematical model of Fe metabolism in a growing cell was developed. The model included Fe import via a regulated high-affinity pathway and an unregulated low-affinity pathway. Fe import from the cytosol into vacuoles and mitochondria, and nanoparticle formation were also included. The model captured essential trafficking behavior, demonstrating that cells regulate Fe import in accordance with their overall growth rate and that they misregulate Fe import when nanoparticles accumulate. The lack of regulation of Fe in yeast is perhaps unique compared to the tight regulation of

  5. Growth rates of the m=0 mode for Bennett equilibria with varying radial density and temperature profiles

    NASA Astrophysics Data System (ADS)

    Stoltz, P. H.; Oliver, B. V.

    2001-06-01

    The linear growth of axisymmetric (m=0) perturbations for various Bennett pinch equilibria are studied numerically with the ALEGRA-MHD code [A. C. Robinson, C. J. Garasi, T. A. Haill, R. L. Morse, and P. H. Stoltz, Proceedings of the 26th IEEE Conference on Plasma Science (IEEE, Piscataway, NJ, 1999), p. 306]. Growth rates are calculated for both skin and diffuse current profiles with varied density and temperature profiles. A destabilizing effect of radially increasing temperature profiles is presented. A factor of three increase in the growth rate over a constant-temperature equilibrium is noted for an equilibrium which is ten times hotter on the edge than at the core. A qualitative explanation is given in terms of the sound speed in the radial region where the mode resides.

  6. Fatigue delamination growth in woven glass/epoxy composite laminates under mixed-mode II/III loading conditions at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Takeda, Tomo; Miura, Masaya; Shindo, Yasuhide; Narita, Fumio

    2013-12-01

    We investigate the cryogenic delamination growth behavior in woven glass fiber reinforced polymer (GFRP) composite laminates under mixed-mode II/III fatigue loading. Fatigue delamination tests were conducted with six-point bending plate (6PBP) specimens at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K), and the delamination growth rate data for various mixed-mode ratios of Modes II and III were obtained. The energy release rate was evaluated using the three-dimensional finite element method. In addition, the fatigue delamination growth mechanisms were characterized by scanning electron microscopic observations of the specimen fracture surfaces.

  7. Interfacial wave theory of dendrite growth - Global mode solution and quantum condition

    NASA Technical Reports Server (NTRS)

    Xu, Jian-Jun

    1990-01-01

    The signal feedback process at the edge of the dendrite tip is investigated, and the global instability mechanism of the system is derived. A mechanism is developed to describe a discrete set of unstable global modes for the system. Called WEASR, the method considers the wave emission at the turning point and signal reflections between the turning point and the front edge of the tip. It is shown that the method can obtain the asymptotic solutions for the unstable global modes and the quantum condition for the corresponding eigenvalues. A turning point called the pattern formation condition is shown to be crucial in the formation of dendritic structure and the choice of the final tip velocity. The wave emission process is outlined, and the importance of a signal feedback process at the edge of the dendrite tip is demonstrated. Parameters such as stability and surface tension can be analyzed in terms of their effects on WEASR modes.

  8. Measurements of sideband mode-coupling effects and linear MHD growth rates associated with the ponderomotive force

    SciTech Connect

    Meassick, S.

    1988-01-01

    Measurements of the interactions of rf waves in the ion cyclotron range of frequencies (ICRF) with flute interchange modes are presented. Interactions between the applied l = +1 rf wave and an m = {minus}1 flute mode give rise to sidebands above and below the rf frequency with mode numbers of l = 0 and l = +2 respectively. The contribution of the sideband terms to perturbed energy are shown to cancel 40% of the direct ponderomotive contribution for w/w{sub ci} = 1.25. This is less then the 90% predicted by self-consistent theories of the ponderomotive force for an applied l = +1 rf wave above the ion cyclotron frequency with a large separation between the plasma and the vacuum vessel. Measurements of the linear growth and decay rate of the flute instability in the presence of rf are presented. These measurements allow a determination of the net stabilizing force on the plasma. The measured growth rate is in good agreement with that calculated by considering only the curvature driven instability and the ponderomotive force.

  9. [Effects of different water-saving irrigation modes on chestnut growth and fruiting in drought hilly land].

    PubMed

    Tian, Shou-Le; Shen, Guang-Ning; Xu, Lin; Sun, Xiao-Li

    2012-03-01

    Taking the chestnut trees in a semi-arid and semi-humid hilly orchard of Tai' an, Shandong Province of East China as test objects, a field experiment was conducted to study the effects of different water-saving irrigation modes (pottery jar storing water, small hole storing water, and border irrigation with covering) on the soil moisture characteristics and the growth, fruiting, and development of chestnut roots. Comparing with the control (border irrigation), all the three water-saving irrigation modes could prolong the period of soil keeping moist, and the best effect came from pottery, jar treatment, with the soil keeping moist for 32 days, 13 days longer than the control. Under water-saving irrigations, the bearing branches length and number, leaf area and mass, and shoot mixed buds all increased obviously. Both pottery jar storing water and small hole storing water could irrigate deeper roots and induce root growth in deeper soil layers, and thus, relieve the drought stress on superficial roots. The three water-saving irrigation modes could increase chestnut yield markedly, with an increment of 18.8%, 16.5%, and 14.2%, respectively, as compared with the control. PMID:22720605

  10. Effects of 1,25(OH)2D3, 25OHD3, and EB1089 on cell growth and Vitamin D receptor mRNA and 1alpha-hydroxylase mRNA expression in primary cultures of the canine prostate.

    PubMed

    Kunakornsawat, S; Rosol, T J; Capen, C C; Omdahl, J L; Leroy, B E; Inpanbutr, N

    2004-05-01

    The aim of this study was to investigate effects of 1,25(OH)(2)D(3) (calcitriol), 25OHD(3), and EB1089 on cell growth and on Vitamin D receptor (VDR) mRNA and 1alpha-hydroxylase (1alpha-OHase) mRNA expression in normal canine prostatic primary cultures. Canine prostatic epithelial cells were isolated, cultured, and treated with vehicle (ethanol), calcitriol, 25OHD(3), and EB1089 at 10(-9) and 10(-7)M. The VDR was present in epithelial and stromal cells of the canine prostate gland. 1,25(OH)(2)D(3), 25OHD(3), and EB1089 inhibited epithelial cell growth at 10(-7)M compared to vehicle-treated controls [calcitriol (P < 0.01), EB1089 (P < 0.01), and 25OHD(3) (P < 0.05)]. Epithelial cells treated with calcitriol and EB1089 at 10(-7)M had slightly increased VDR mRNA expression (0.2-0.3-fold) at 6 and 12h compared to controls. There was no difference in 1alpha-OHase mRNA expression in epithelial cells treated with these three compounds. 1,25(OH)(2)D(3) and its analogs may be effective antiproliferative agents of epithelial cells in certain types of prostate cancer. PMID:15225811

  11. Metrology for graphene and 2D materials

    NASA Astrophysics Data System (ADS)

    Pollard, Andrew J.

    2016-09-01

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

  12. Focusing surface wave imaging with flexible 2D array

    NASA Astrophysics Data System (ADS)

    Zhou, Shiyuan; Fu, Junqiang; Li, Zhe; Xu, Chunguang; Xiao, Dingguo; Wang, Shaohan

    2016-04-01

    Curved surface is widely exist in key parts of energy and power equipment, such as, turbine blade cylinder block and so on. Cycling loading and harsh working condition of enable fatigue cracks appear on the surface. The crack should be found in time to avoid catastrophic damage to the equipment. A flexible 2D array transducer was developed. 2D Phased Array focusing method (2DPA), Mode-Spatial Double Phased focusing method (MSDPF) and the imaging method using the flexible 2D array probe are studied. Experiments using these focusing and imaging method are carried out. Surface crack image is obtained with both 2DPA and MSDPF focusing method. It have been proved that MSDPF can be more adaptable for curved surface and more calculate efficient than 2DPA.

  13. NKG2D ligands as therapeutic targets

    PubMed Central

    Spear, Paul; Wu, Ming-Ru; Sentman, Marie-Louise; Sentman, Charles L.

    2013-01-01

    The Natural Killer Group 2D (NKG2D) receptor plays an important role in protecting the host from infections and cancer. By recognizing ligands induced on infected or tumor cells, NKG2D modulates lymphocyte activation and promotes immunity to eliminate ligand-expressing cells. Because these ligands are not widely expressed on healthy adult tissue, NKG2D ligands may present a useful target for immunotherapeutic approaches in cancer. Novel therapies targeting NKG2D ligands for the treatment of cancer have shown preclinical success and are poised to enter into clinical trials. In this review, the NKG2D receptor and its ligands are discussed in the context of cancer, infection, and autoimmunity. In addition, therapies targeting NKG2D ligands in cancer are also reviewed. PMID:23833565

  14. Construction and Validation of the Rhodobacter sphaeroides 2.4.1 DNA Microarray: Transcriptome Flexibility at Diverse Growth Modes

    SciTech Connect

    Pappas, Christopher T.; Sram, Jakub; Moskvin, Oleg V.; Ivanov, Pavel S.; Mackenzie, Christopher; Choudhary, Madhusudan; Land, Miriam L; Larimer, Frank W; Kaplan, Samuel; Gomelsky, Mark

    2004-07-01

    A high-density oligonucleotide DNA microarray, a genechip, representing the 4.6-Mb genome of the facultative phototrophic proteobacterium, Rhodobacter sphaeroides 2.4.1, was custom-designed and manufactured by Affymetrix, Santa Clara, Calif. The genechip contains probe sets for 4,292 open reading frames (ORFs), 47 rRNA and tRNA genes, and 394 intergenic regions. The probe set sequences were derived from the genome annotation generated by Oak Ridge National Laboratory after extensive revision, which was based primarily upon codon usage characteristic of this GC-rich bacterium. As a result of the revision, numerous missing ORFs were uncovered, nonexistent ORFs were deleted, and misidentified start codons were corrected. To evaluate R. sphaeroides transcriptome flexibility, expression profiles for three diverse growth modes-aerobic respiration, anaerobic respiration in the dark, and anaerobic photosynthesis-were generated. Expression levels of one-fifth to one-third of the R. sphaeroides ORFs were significantly different in cells under any two growth modes. Pathways involved in energy generation and redox balance maintenance under three growth modes were reconstructed. Expression patterns of genes involved in these pathways mirrored known functional changes, suggesting that massive changes in gene expression are the major means used by R. sphaeroides in adaptation to diverse conditions. Differential expression was observed for genes encoding putative new participants in these pathways (additional photosystem genes, duplicate NADH dehydrogenase, ATP synthases), whose functionality has yet to be investigated. The DNA microarray data correlated well with data derived from quantitative reverse transcription-PCR, as well as with data from the literature, thus validating the R. sphaeroides genechip as a powerful and reliable tool for studying unprecedented metabolic versatility of this bacterium.

  15. Tests and analyses for fully plastic fracture mechanics of plane strain mode I crack growth

    SciTech Connect

    McClintock, F.A.; Parks, D.M.; Kim, Y.J.

    1995-12-31

    Under monotonic loading, structures should ideally be ductile enough to provide continued resistance during crack growth. For fully plastic crack growth in low strength alloys, existing asymptotic solutions for elastic-plastic growing cracks are not applicable because they reach the fracture strain only in regions small compared to the inhomogeneities of the actual fracture process. For the limiting case of non-hardening fully-plastic plane strain crack growth, in a number of geometries and loadings the near-tip fields are characterized in terms of three parameters: an effective angle 2{theta}{sub s} between a pair of slip planes, and the normal stress {sigma}{sub s} and the increment of displacement {delta}u{sub s} across the planes. This three-parameter characterization is in contrast to the one- or two-parameter (K or J and T or Q) characterization in linear or non-linear elastic fracture mechanics. These {theta}{sub s}, {sigma}{sub s}, and {delta}u{sub s} parameters are found form the far-field geometries and loadings through slip line fields or least upper bound analyses based on circular arcs. The resulting crack growth, in terms of the crack tip opening angle (CTOA), is a function of {theta}{sub s}, {sigma}{sub s}, and the material. The geometry of the crack growing between two moving slip planes emanating from its tip reduces this function to the critical fracture shear strain left behind the slip planes, {gamma}f, as a function of {sigma}{sub s}. {gamma}f({sigma}{sub s}) is found theoretically from a hole initiation and growth model. It is also found from preliminary fully plastic crack growth experiments on unequally grooved specimens with fixed-grip extension or 4-point bending of a 1018 CF steel.

  16. Evaluation of Delamination Growth Characterization Methods Under Mode I Fatigue Loading

    NASA Technical Reports Server (NTRS)

    Murri, Gretchen B.

    2012-01-01

    Reliable delamination characterization data for laminated composites are needed for input to analytical models of structures to predict delamination. The double-cantilevered beam (DCB) specimen is used with laminated composites to measure fracture toughness, G(sub Ic), delamination onset strain energy release rate, and growth rate data under cyclic loading. In the current study, DCB specimens of IM7/8552 graphite/epoxy supplied by two different manufacturers were tested in static and fatigue to compare the measured characterization data from the two sources, and to evaluate a proposed ASTM standard for generating Paris Law equations. Static results were used to generate compliance calibration constants for the fatigue data, and a delamination resistance curve, G(sub IR), which was used to determine the effects of fiber-bridging on delamination growth. Specimens were tested in fatigue at a cyclic G(sub Imax) level equal to 50, 40 or 30% of G(sub Ic), to determine a delamination onset curve and delamination growth rate. The delamination onset curve equations had similar exponents and the same trends. Delamination growth rate was calculated by fitting a Paris Law to the da/dN versus G(sub Imax) data. Both a 2-point and a 7-point data reduction method were used and the Paris Law equations were compared. To determine the effects of fiber-bridging, growth rate results were normalized by the delamination resistance curve for each material and compared to the non-normalized results. Paris Law exponents were found to decrease by 31% to 37% due to normalizing the growth data. Normalizing the data also greatly reduced the amount of scatter between the different specimens. Visual data records from the fatigue testing were used to calculate individual compliance calibration constants from the fatigue data for some of the specimens. The resulting da/dN versus G(sub Imax) plots showed much improved repeatability between specimens. Gretchen

  17. Geometry and dynamics of a coupled 4 D-2 D quantum field theory

    NASA Astrophysics Data System (ADS)

    Bolognesi, Stefano; Chatterjee, Chandrasekhar; Evslin, Jarah; Konishi, Kenichi; Ohashi, Keisuke; Seveso, Luigi

    2016-01-01

    Geometric and dynamical aspects of a coupled 4 D-2 D interacting quantum field theory — the gauged nonAbelian vortex — are investigated. The fluctuations of the internal 2 D nonAbelian vortex zeromodes excite the massless 4 D Yang-Mills modes and in general give rise to divergent energies. This means that the well-known 2 D C{P}^{N-1} zeromodes associated with a nonAbelian vortex become nonnormalizable.

  18. Measurement of topological invariants in a 2D photonic system

    NASA Astrophysics Data System (ADS)

    Mittal, Sunil; Ganeshan, Sriram; Fan, Jingyun; Vaezi, Abolhassan; Hafezi, Mohammad

    2016-03-01

    A hallmark feature of topological physics is the presence of one-way propagating chiral modes at the system boundary. The chirality of edge modes is a consequence of the topological character of the bulk. For example, in a non-interacting quantum Hall model, edge modes manifest as mid-gap states between two topologically distinct bulk bands. The bulk-boundary correspondence dictates that the number of chiral edge modes, a topological invariant called the winding number, is completely determined by the bulk topological invariant, the Chern number. Here, for the first time, we measure the winding number in a 2D photonic system. By inserting a unit flux quantum at the edge, we show that the edge spectrum resonances shift by the winding number. This experiment provides a new approach for unambiguous measurement of topological invariants, independent of the microscopic details, and could possibly be extended to probe strongly correlated topological orders.

  19. Evaluation of Delamination Onset and Growth Characterization Methods under Mode I Fatigue Loading

    NASA Technical Reports Server (NTRS)

    Murri, Gretchen B.

    2013-01-01

    Double-cantilevered beam specimens of IM7/8552 graphite/epoxy from two different manufacturers were tested in static and fatigue to compare the material characterization data and to evaluate a proposed ASTM standard for generating Paris Law equations for delamination growth. Static results were used to generate compliance calibration constants for reducing the fatigue data, and a delamination resistance curve, GIR, for each material. Specimens were tested in fatigue at different initial cyclic GImax levels to determine a delamination onset curve and the delamination growth rate. The delamination onset curve equations were similar for the two sources. Delamination growth rate was calculated by plotting da/dN versus GImax on a log-log scale and fitting a Paris Law. Two different data reduction methods were used to calculate da/dN. To determine the effects of fiber-bridging, growth results were normalized by the delamination resistance curves. Paris Law exponents decreased by 31% to 37% after normalizing the data. Visual data records from the fatigue tests were used to calculate individual compliance constants from the fatigue data. The resulting da/dN versus GImax plots showed improved repeatability for each source, compared to using averaged static data. The Paris Law expressions for the two sources showed the closest agreement using the individually fit compliance data.

  20. Multi-stacked InAs/GaAs quantum dots grown with different growth modes for quantum dot solar cells

    SciTech Connect

    Kim, Yeongho; Ban, Keun-Yong Honsberg, Christiana B.

    2015-06-01

    We have studied the material properties and device performance of InAs/GaAs quantum dot solar cells (QDSCs) made using three different QD growth modes: Stranski-Krastanov (S-K), quasi-monolayer (QML), and sub-monolayer (SML) growth modes. All QDSCs show an extended external quantum efficiency (EQE) at near infrared wavelengths of 950–1070 nm from the QD absorption. Compared to the S-K and SML QDSCs, the QML QDSC with a higher strain exhibits a poor EQE response in the wavelength region of 300–880 nm due to increased non-radiative recombination. The conversion efficiency of the S-K and SML QDSCs exceeds that of the reference cell (13.4%) without QDs due to an enhanced photocurrent (>16% increase) produced by the silicon doped QD stacks. However, as expected from the EQE of the QML QDSC, the increase of strain-induced crystalline defects greatly degrades the photocurrent and open-circuit voltage, leading to the lowest conversion efficiency (8.9%)

  1. Perspectives for spintronics in 2D materials

    NASA Astrophysics Data System (ADS)

    Han, Wei

    2016-03-01

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

  2. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations. PMID:27099950

  3. Applications of 2D IR spectroscopy to peptides, proteins, and hydrogen-bond dynamics

    PubMed Central

    Kim, Yung Sam; Hochstrasser, Robin M.

    2010-01-01

    Following a survey of 2D IR principles this Feature Article describes recent experiments on the hydrogen-bond dynamics of small ions, amide-I modes, nitrile probes, peptides, reverse transcriptase inhibitors, and amyloid fibrils. PMID:19351162

  4. Effect of density gradients in confined supersonic shear layers. Part 2: 3-D modes

    NASA Technical Reports Server (NTRS)

    Peroomian, Oshin; Kelly, R. E.

    1994-01-01

    The effect of basic flow density gradients on the supersonic wall modes were investigated in Part 1 of this analysis. In that investigation only the 2-D modes were studied. Tam and Hu investigated the 3-D modes in a confined vortex sheet and reported that the first 2-D Class A mode (A01) had the highest growth rate compared to all other 2-D and 3-D modes present in the vortex sheet for that particular set of flow patterns. They also showed that this result also held true for finite thickness shear layers with delta(sub w) less than 0.125. For free shear layers, Sandham and Reynolds showed that the 3-D K-H mode became the dominant mode for M(sub c) greater than 0.6. Jackson and Grosch investigated the effect of crossflow and obliqueness on the slow and fast odes present in a M(sub c) greater than 1 environment and showed that for certain combination of crossflow and wave angles the growth rates could be increased by up to a factor of 2 with respect to the 2-D case. The case studied here is a confined shear layer shown in Part 1. All solution procedures and basic low profiles are the same as in Part 1. The effect of density gradients on the 3-D modes present in the density ratios considered in Part 1 are investigated.

  5. Binding mode of the breakthrough inhibitor AZD9291 to epidermal growth factor receptor revealed.

    PubMed

    Yosaatmadja, Yuliana; Silva, Shevan; Dickson, James M; Patterson, Adam V; Smaill, Jeff B; Flanagan, Jack U; McKeage, Mark J; Squire, Christopher J

    2015-12-01

    The discovery of genetic drivers of lung cancer in patient sub-groups has led to their use as predictive biomarkers and as targets for selective drug therapy. Some of the most important lung cancer drivers are mutations in the EGFR gene, for example, the exon 19 deletions and the L858R variant that confer sensitivity to the front line drugs erlotinib and gefitinib; the acquired T790M variants confer drug resistance and a poor prognosis. A challenge then in targeting EGFR is to produce drugs that inhibit both sensitising variants and resistance variants, leaving wild type protein in healthy cells unaffected. One such agent is AstraZeneca's "breakthrough" AZD9291 molecule that shows a 200-fold selectivity for T790M/L858R over wild type EGFR. Our X-ray crystal structure reveals the binding mode of AZD9291 to the kinase domain of wild type EGFR. PMID:26522274

  6. Ultrasonic 2D matrix PVDF transducer

    NASA Astrophysics Data System (ADS)

    Ptchelintsev, A.; Maev, R. Gr.

    2000-05-01

    During the past decade a substantial amount of work has been done in the area of ultrasonic imaging technology using 2D arrays. The main problems arising for the two-dimensional matrix transducers at megahertz frequencies are small size and huge count of the elements, high electrical impedance, low sensitivity, bad SNR and slower data acquisition rate. The major technological difficulty remains the high density of the interconnect. To solve these problems numerous approaches have been suggested. In the present work, a 24×24 elements (24 transmit+24 receive) matrix and a switching board were developed. The transducer consists of two 52 μm PVDF layers each representing a linear array of 24 elements placed one on the top of the other. Electrodes in these two layers are perpendicular and form the grid of 0.5×0.5 mm pitch. The layers are bonded together with the ground electrode being monolithic and located between the layers. The matrix is backed from the rear surface with an epoxy composition. During the emission, a linear element from the emitting layer generates a longitudinal wave pulse propagating inside the test object. Reflected pulses are picked-up by the receiving layer. During one transmit-receive cycle one transmit element and one receive element are selected by corresponding multiplexers. These crossed elements emulate a small element formed by their intersection. The present design presents the following advantages: minimizes number of active channels and density of the interconnect; reduces the electrical impedance of the element improving electrical matching; enables the transmit-receive mode; due to the efficient backing provides bandwidth and good time resolution; and, significantly reduces the electronics complexity. The matrix can not be used for the beam steering and focusing. Owing to this impossibility of focusing, the penetration depth is limited as well by the diffraction phenomena.

  7. Observations of vortex merger and growth reduction in a dual-mode, supersonic Kelvin-Helmholtz instability experiment

    NASA Astrophysics Data System (ADS)

    Wan, Willow; Malamud, Guy; Shimony, Assaf; Trantham, Matt; Klein, Sallee; Shvarts, Dov; Kuranz, Carolyn; Drake, R. Paul

    2015-11-01

    The Kelvin-Helmholtz instability (KHI) generates vortical structures and turbulence at an interface with shear flow. This instability is ubiquitous in natural and engineering systems including astrophysical environments and laboratory plasmas. Detailed measurements of modulation amplitude growth reduction and vortex merger evolving from well-defined initial conditions can benchmark hydrodynamic models and theories. This experiment provides the first measurements of the vortex merger rate of well-characterized seed perturbations evolving under the influence of the KHI in a supersonic flow. These data were obtained by utilizing a sustained laser pulse to drive a steady shockwave into low-density carbon foam, introducing shear along a precision-machined plastic interface. The evolution and merger of the modulations was measured with x-ray radiography and reproduced with 2D hydrodynamic simulations. This work is funded by the U.S. Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840, and the National Laser User Facility Program, grant number DE-NA0002032, and through the Laboratory for Laser Energetics, University of Rochester by the NNSA/OICF under Cooperative Agreement No. DE-FC52-08NA28302.

  8. The Mode of Cell Wall Growth in Selected Archaea Is Similar to the General Mode of Cell Wall Growth in Bacteria as Revealed by Fluorescent Dye Analysis ▿ †

    PubMed Central

    Wirth, Reinhard; Bellack, Annett; Bertl, Markus; Bilek, Yvonne; Heimerl, Thomas; Herzog, Bastian; Leisner, Madeleine; Probst, Alexander; Rachel, Reinhard; Sarbu, Christina; Schopf, Simone; Wanner, Gerhard

    2011-01-01

    The surfaces of 8 bacterial and 23 archaeal species, including many hyperthermophilic Archaea, could be stained using succinimidyl esters of fluorescent dyes. This allowed us for the first time to analyze the mode of cell wall growth in Archaea by subculturing stained cells. The data obtained show that incorporation of new cell wall material in Archaea follows the pattern observed for Bacteria: in the coccoid species Pyrococcus furiosus incorporation was in the region of septum formation while for the rod-shaped species Methanopyrus kandleri and Methanothermus sociabilis, a diffuse incorporation of cell wall material over the cell length was observed. Cell surface appendages like fimbriae/pili, fibers, or flagella were detectable by fluorescence staining only in a very few cases although their presence was proven by electron microscopy. Our data in addition prove that Alexa Fluor dyes can be used for in situ analyses at temperatures up to 100°C. PMID:21169435

  9. Nonlinear Spring Finite Elements for Predicting Mode I-Dominated Delamination Growth in Laminated Structure with Through-Thickness reinforcement

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; Krueger, Ronald

    2006-01-01

    One particular concern of polymer matrix composite laminates is the relatively low resistance to delamination cracking, in particular when the dominant type of failure is mode I opening. One method proposed for alleviating this problem involves the insertion pultruded carbon pins through the laminate thickness. The pins, known as z-pins, are inserted into the prepreg laminate using an ultrasonic hammer prior to the curing process, resulting in a field of pins embedded normal to the laminate plane as illustrated in Figure. 1. Pin diameters range between 0.28-mm to 0.5-mm and standard areal densities range from 0.5% to 4%. The z-pins are provided by the manufacturer, Aztex(Registered TradeMark) , in a low-density foam preform, which acts to stabilize orientation of the pins during the insertion process [1-3]. Typical pin materials include boron and carbon fibers embedded in a polymer matrix. A number of methods have been developed for predicting delamination growth in laminates reinforced with z-pins. During a study on the effect of z-pin reinforcement on mode I delamination resistance, finite element analyses of z-pin reinforced double cantilever beam (DCB) specimens were performed by Cartie and Partridge [4]. The z-pin bridging stresses were modeled by applying equivalent forces at the pin locations. Single z-pin pull-out tests were performed to characterize the traction law of the pins under mode I loading conditions. Analytical solutions for delamination growth in z-pin reinforced DCB specimens were independently derived by Robinson and Das [5] and Ratcliffe and O'Brien [6]. In the former case, pin bridging stresses were modeled using a distributed load and in the latter example the bridging stresses were discretely modeled by way of grounded springs. Additionally, Robinson and Das developed a data reduction strategy for calculating mode I fracture toughness, G(sub Ic), from a z-pin reinforced DCB specimen test [5]. In both cases a traction law similar to that

  10. Annotated Bibliography of EDGE2D Use

    SciTech Connect

    J.D. Strachan and G. Corrigan

    2005-06-24

    This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables.

  11. Staring 2-D hadamard transform spectral imager

    DOEpatents

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

    2006-02-07

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

  12. Accelerated fatigue crack growth behavior of PWA 1480 single crystal alloy and its dependence on the deformation mode

    NASA Technical Reports Server (NTRS)

    Telesman, Jack; Ghosn, Louis J.

    1988-01-01

    An investigation of the fatigue crack growth (FCG) behavior of PWA 1480 single crystal nickel base superalloy was conducted. Typical Paris region behavior was observed above a delta K of 8 MPa sq rt of m. However, below that stress intensity range, the alloy exhibited highly unusual behavior. This behavior consisted of a region where the crack growth rate became essentially independent of the applied stress intensity. The transition in the FCG behavior was related to a change in the observed crack growth mechanisms. In the Paris region, fatigue failure occurred along (111) facets; however, at the lower stress intensities, (001) fatigue failure was observed. A mechanism was proposed, based on barriers to dislocation motion, to explain the changes in the observed FCG behavior. The FCG data were also evaluated in terms of a recently proposed stress intensity parameter, K sub rss. This parameter, based on the resolved shear stresses on the slip planes, quantified the crack driving force as well as the mode I delta K, and at the same time was also able to predict the microscopic crack path under different stress states.

  13. Synchronized growth and neutral lipid accumulation in Chlorella sorokiniana FC6 IITG under continuous mode of operation.

    PubMed

    Kumar, Vikram; Muthuraj, Muthusivaramapandian; Palabhanvi, Basavaraj; Das, Debasish

    2016-01-01

    Synchronized growth and neutral lipid accumulation with high lipid productivity under mixotrophic growth of the strain Chlorella sorokiniana FC6 IITG was achieved via manipulation of substrates feeding mode and supplementation of lipid elicitors in the growth medium. Screening and optimization of lipid elicitors resulted in lipid productivity of 110.59mgL(-1)day(-1) under the combined effect of lipid inducers sodium acetate and sodium chloride. Fed-batch cultivation of the strain in bioreactor with intermittent feeding of limiting nutrients and lipid inducer resulted in maximum biomass and lipid productivity of 2.08 and 0.97gL(-1)day(-1) respectively. Further, continuous production of biomass with concomitant lipid accumulation was demonstrated via continuous feeding of BG11 media supplemented with lipid inducers sodium acetate and sodium chloride. The improved biomass and lipid productivity in chemostat was found to be 2.81 and 1.27gL(-1)day(-1) respectively operated at a dilution rate of 0.54day(-1). PMID:26575619

  14. TOPICAL REVIEW: The various modes of growth of metals on quasicrystals

    NASA Astrophysics Data System (ADS)

    Smerdon, J. A.

    2010-11-01

    Quasicrystals are fascinating intermetallic compounds composed of two or more elements. They differ from conventional crystals in that they possess long-range order, but no translational symmetry—that is, they are aperiodic. Much effort has been expended on identifying routes towards exploiting and exploring the properties of such systems due to their aperiodic nature. One such route is concerned with the deposition of thin films, particularly of metals, to investigate how their growth progresses in this inherently frustrated scenario. This topical review will examine the various epitaxial relationships observed in quasicrystal research with particular emphasis on single-element metallic films deposited under ultrahigh-vacuum conditions.

  15. Epitaxial growth of the topological insulator Bi{sub 2}Se{sub 3} on Si(111): Growth mode, lattice parameter, and strain state

    SciTech Connect

    Vyshnepolsky, M.; Klein, C.; Klasing, F.; Hanisch-Blicharski, A.; Horn-von Hoegen, M.

    2013-09-09

    Using spot profile analysis low energy electron diffraction, we studied the growth mode and strain state of ultra-thin epitaxial Bi{sub 2}Se{sub 3}(111) films grown by molecular beam epitaxy on Si(111). The first layer grows as complete quintuple layer and covers the Si substrate before the next layer nucleates. Its lateral lattice parameter is increased by 1% compared with the value of a{sub ‖} = 4.136 Å for a 6-nm-thick film. With increasing film thickness, a continuous change of the lattice parameter is observed to an asymptotic value, which is explained by a van der Waals-like bonding between the Bi{sub 2}Se{sub 3} film and the Si substrate.

  16. Real-time 2-D temperature imaging using ultrasound.

    PubMed

    Liu, Dalong; Ebbini, Emad S

    2010-01-01

    We have previously introduced methods for noninvasive estimation of temperature change using diagnostic ultrasound. The basic principle was validated both in vitro and in vivo by several groups worldwide. Some limitations remain, however, that have prevented these methods from being adopted in monitoring and guidance of minimally invasive thermal therapies, e.g., RF ablation and high-intensity-focused ultrasound (HIFU). In this letter, we present first results from a real-time system for 2-D imaging of temperature change using pulse-echo ultrasound. The front end of the system is a commercially available scanner equipped with a research interface, which allows the control of imaging sequence and access to the RF data in real time. A high-frame-rate 2-D RF acquisition mode, M2D, is used to capture the transients of tissue motion/deformations in response to pulsed HIFU. The M2D RF data is streamlined to the back end of the system, where a 2-D temperature imaging algorithm based on speckle tracking is implemented on a graphics processing unit. The real-time images of temperature change are computed on the same spatial and temporal grid of the M2D RF data, i.e., no decimation. Verification of the algorithm was performed by monitoring localized HIFU-induced heating of a tissue-mimicking elastography phantom. These results clearly demonstrate the repeatability and sensitivity of the algorithm. Furthermore, we present in vitro results demonstrating the possible use of this algorithm for imaging changes in tissue parameters due to HIFU-induced lesions. These results clearly demonstrate the value of the real-time data streaming and processing in monitoring, and guidance of minimally invasive thermotherapy. PMID:19884075

  17. Development of a numerical procedure for mixed mode K-solutions and fatigue crack growth in FCC single crystal superalloys

    NASA Astrophysics Data System (ADS)

    Ranjan, Srikant

    2005-11-01

    Fatigue-induced failures in aircraft gas turbine and rocket engine turbopump blades and vanes are a pervasive problem. Turbine blades and vanes represent perhaps the most demanding structural applications due to the combination of high operating temperature, corrosive environment, high monotonic and cyclic stresses, long expected component lifetimes and the enormous consequence of structural failure. Single crystal nickel-base superalloy turbine blades are being utilized in rocket engine turbopumps and jet engines because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. These materials have orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Computation of stress intensity factors (SIFs) and the ability to model fatigue crack growth rate at single crystal cracks subject to mixed-mode loading conditions are important parts of developing a mechanistically based life prediction for these complex alloys. A general numerical procedure has been developed to calculate SIFs for a crack in a general anisotropic linear elastic material subject to mixed-mode loading conditions, using three-dimensional finite element analysis (FEA). The procedure does not require an a priori assumption of plane stress or plane strain conditions. The SIFs KI, KII, and KIII are shown to be a complex function of the coupled 3D crack tip displacement field. A comprehensive study of variation of SIFs as a function of crystallographic orientation, crack length, and mode-mixity ratios is presented, based on the 3D elastic orthotropic finite element modeling of tensile and Brazilian Disc (BD) specimens in specific crystal orientations. Variation of SIF through the thickness of the specimens is also analyzed. The resolved shear stress intensity coefficient or effective SIF, Krss, can be computed as a function of crack tip SIFs and the

  18. Magnetorotational instability: nonmodal growth and the relationship of global modes to the shearing box

    SciTech Connect

    Squire, J.; Bhattacharjee, A.

    2014-12-10

    We study magnetorotational instability (MRI) using nonmodal stability techniques. Despite the spectral instability of many forms of MRI, this proves to be a natural method of analysis that is well-suited to deal with the non-self-adjoint nature of the linear MRI equations. We find that the fastest growing linear MRI structures on both local and global domains can look very different from the eigenmodes, invariably resembling waves shearing with the background flow (shear waves). In addition, such structures can grow many times faster than the least stable eigenmode over long time periods, and be localized in a completely different region of space. These ideas lead—for both axisymmetric and non-axisymmetric modes—to a natural connection between the global MRI and the local shearing box approximation. By illustrating that the fastest growing global structure is well described by the ordinary differential equations (ODEs) governing a single shear wave, we find that the shearing box is a very sensible approximation for the linear MRI, contrary to many previous claims. Since the shear wave ODEs are most naturally understood using nonmodal analysis techniques, we conclude by analyzing local MRI growth over finite timescales using these methods. The strong growth over a wide range of wave-numbers suggests that nonmodal linear physics could be of fundamental importance in MRI turbulence.

  19. Highly-resolved 2D HYDRA simulations of Double-Shell Ignition Designs

    SciTech Connect

    Milovich, J L; Amendt, P; Hamza, A; Marinak, M; Robey, H

    2006-06-30

    Double-shell (DS) targets (Amendt, P. A. et al., 2002) offer a complementary approach to the cryogenic baseline design (Lindl, J. et al., 2004) for achieving ignition on the National Ignition Facility (NIF). Among the expected benefits are the ease of room temperature preparation and fielding, the potential for lower laser backscatter and the reduced need for careful shock timing. These benefits are offset, however, by demanding fabrication tolerances, e.g., shell concentricity and shell surface smoothness. In particular, the latter is of paramount importance since DS targets are susceptible to the growth of interface perturbations from impulsive and time-dependent accelerations. Previous work (Milovich, J. L. et al., 2004) has indicated that the growth of perturbations on the outer surface of the inner shell is potentially disruptive. To control this instability new designs have been proposed requiring bimetallic inner shells and material-matching mid-Z nanoporous foam. The challenges in manufacturing such exotic foams have led to a further evaluation of the densities and pore sizes needed to reduce the seeding of perturbations on the outer surface of the inner shell, thereby guiding the ongoing material science research efforts. Highly-resolved 2D simulations of porous foams have been performed to establish an upper limit on the allowable pore sizes for instability growth. Simulations indicate that foams with higher densities than previously thought are now possible. Moreover, while at the present time we are only able to simulate foams with average pore sizes larger than 1 micron (due to computational limitations), we can conclude that these pore sizes are potentially problematic. Furthermore, the effect of low-order hohlraum radiation asymmetries on the growth of intrinsic surface perturbations is also addressed. Highly-resolved 2D simulations indicate that the transverse flows that are set up by these low-order mode features (which can excite Kelvin

  20. Use of anomolous thermal imaging effects for multi-mode systems control during crystal growth

    NASA Technical Reports Server (NTRS)

    Wargo, Michael J.

    1989-01-01

    Real time image processing techniques, combined with multitasking computational capabilities are used to establish thermal imaging as a multimode sensor for systems control during crystal growth. Whereas certain regions of the high temperature scene are presently unusable for quantitative determination of temperature, the anomalous information thus obtained is found to serve as a potentially low noise source of other important systems control output. Using this approach, the light emission/reflection characteristics of the crystal, meniscus and melt system are used to infer the crystal diameter and a linear regression algorithm is employed to determine the local diameter trend. This data is utilized as input for closed loop control of crystal shape. No performance penalty in thermal imaging speed is paid for this added functionality. Approach to secondary (diameter) sensor design and systems control structure is discussed. Preliminary experimental results are presented.

  1. Light field morphing using 2D features.

    PubMed

    Wang, Lifeng; Lin, Stephen; Lee, Seungyong; Guo, Baining; Shum, Heung-Yeung

    2005-01-01

    We present a 2D feature-based technique for morphing 3D objects represented by light fields. Existing light field morphing methods require the user to specify corresponding 3D feature elements to guide morph computation. Since slight errors in 3D specification can lead to significant morphing artifacts, we propose a scheme based on 2D feature elements that is less sensitive to imprecise marking of features. First, 2D features are specified by the user in a number of key views in the source and target light fields. Then the two light fields are warped view by view as guided by the corresponding 2D features. Finally, the two warped light fields are blended together to yield the desired light field morph. Two key issues in light field morphing are feature specification and warping of light field rays. For feature specification, we introduce a user interface for delineating 2D features in key views of a light field, which are automatically interpolated to other views. For ray warping, we describe a 2D technique that accounts for visibility changes and present a comparison to the ideal morphing of light fields. Light field morphing based on 2D features makes it simple to incorporate previous image morphing techniques such as nonuniform blending, as well as to morph between an image and a light field. PMID:15631126

  2. 2D materials for nanophotonic devices

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  3. Inertial solvation in femtosecond 2D spectra

    NASA Astrophysics Data System (ADS)

    Hybl, John; Albrecht Ferro, Allison; Farrow, Darcie; Jonas, David

    2001-03-01

    We have used 2D Fourier transform spectroscopy to investigate polar solvation. 2D spectroscopy can reveal molecular lineshapes beneath ensemble averaged spectra and freeze molecular motions to give an undistorted picture of the microscopic dynamics of polar solvation. The transition from "inhomogeneous" to "homogeneous" 2D spectra is governed by both vibrational relaxation and solvent motion. Therefore, the time dependence of the 2D spectrum directly reflects the total response of the solvent-solute system. IR144, a cyanine dye with a dipole moment change upon electronic excitation, was used to probe inertial solvation in methanol and propylene carbonate. Since the static Stokes' shift of IR144 in each of these solvents is similar, differences in the 2D spectra result from solvation dynamics. Initial results indicate that the larger propylene carbonate responds more slowly than methanol, but appear to be inconsistent with rotational estimates of the inertial response. To disentangle intra-molecular vibrations from solvent motion, the 2D spectra of IR144 will be compared to the time-dependent 2D spectra of the structurally related nonpolar cyanine dye HDITCP.

  4. Internal Photoemission Spectroscopy of 2-D Materials

    NASA Astrophysics Data System (ADS)

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

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

  5. Synthesis, growth and characterization of ZnO microtubes using a traveling-wave mode microwave system

    SciTech Connect

    Al-Naser, Qusay A.H.; Zhou, Jian; Wang, Han; Liu, Guizhen; Wang, Lin

    2015-06-15

    Highlights: • ZnO microtubes were successfully synthesized within 15 min. • Introducing a design of a traveling-wave mode microwave system. • Growth temperature of ZnO microtubes becomes predominant between 1350 °C and 1400 °C. • ZnO microtube showed a strong ultraviolet and a weak and broad green emission. • ZnO microtube is composed only of ZnO with high crystallinity. - Abstract: Field emission scanning electron microscopy (FESEM) investigation reveals that zinc oxide (ZnO) microtubes have been successfully synthesized via a traveling-wave mode microwave system. These products are hexagonal tubular crystals with an average diameter of 60 μm and 250 μm in length, having a well faceted end and side surfaces. The wall thickness of the ZnO tubes is about 3–5 μm. The influence of reaction temperature on the formation of crystalline ZnO hexagonal tubes is studied. Room temperature photoluminescence (PL) spectra have also been examined to explore the optical property which exhibits strong ultraviolet emission at 377.422 nm and a weak and broad green emission band at 587.548 nm. X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) show that the product is composed only of ZnO with high crystallinity. The presented synthesis method possesses several advantages, which would be significant to the deeper study and wide applications of ZnO tubes in the future.

  6. A series of experiments aimed at clarifying the mode of action of barley straw in cyanobacterial growth control.

    PubMed

    Iredale, Robert S; McDonald, Adrian T; Adams, David G

    2012-11-15

    For over 25 years it has been known that rotting barley straw can be used to prevent the development of blooms of cyanobacteria and algae in freshwater bodies, although its effectiveness can be variable. The mode of action is still not understood, although a number of hypotheses have been suggested, many of which are supported by little or no experimental evidence. Here, we provide the first experimental confirmation that microbial activity is responsible for the release of either the growth inhibitory fraction, or its precursor, from whole straw, after three or more weeks of decomposition. However, a much more rapid release of inhibitory components was achieved by fine chopping of fresh straw. In bioassays of straw activity the choice of both the cyanobacterial test strain and the assay temperature affected the outcome. The inhibitory activity of straw was greater when decomposition was carried out in the presence of UV-supplemented visible light and this activity was reduced in the presence of catalase, implying that straw activity may in part involve hydrogen peroxide. A better understanding of straw decomposition is required to clarify the mode of action of straw and allow the optimisation of its use in the field. PMID:22989994

  7. C-di-GMP regulates Pseudomonas aeruginosa stress response to tellurite during both planktonic and biofilm modes of growth

    PubMed Central

    Chua, Song Lin; Sivakumar, Krishnakumar; Rybtke, Morten; Yuan, Mingjun; Andersen, Jens Bo; Nielsen, Thomas E.; Givskov, Michael; Tolker-Nielsen, Tim; Cao, Bin; Kjelleberg, Staffan; Yang, Liang

    2015-01-01

    Stress response plays an important role on microbial adaptation under hostile environmental conditions. It is generally unclear how the signaling transduction pathway mediates a stress response in planktonic and biofilm modes of microbial communities simultaneously. Here, we showed that metalloid tellurite (TeO32–) exposure induced the intracellular content of the secondary messenger cyclic di-GMP (c-di-GMP) of Pseudomonas aeruginosa. Two diguanylate cyclases (DGCs), SadC and SiaD, were responsible for the increased intracellular content of c-di-GMP. Enhanced c-di-GMP levels by TeO32– further increased P. aeruginosa biofilm formation and resistance to TeO32–. P. aeruginosa ΔsadCΔsiaD and PAO1/plac-yhjH mutants with low intracellular c-di-GMP content were more sensitive to TeO32– exposure and had low relative fitness compared to the wild-type PAO1 planktonic and biofilm cultures exposed to TeO32–. Our study provided evidence that c-di-GMP level can play an important role in mediating stress response in microbial communities during both planktonic and biofilm modes of growth. PMID:25992876

  8. Distinct growth hormone receptor signaling modes regulate skeletal muscle development and insulin sensitivity in mice

    PubMed Central

    Mavalli, Mahendra D.; DiGirolamo, Douglas J.; Fan, Yong; Riddle, Ryan C.; Campbell, Kenneth S.; van Groen, Thomas; Frank, Stuart J.; Sperling, Mark A.; Esser, Karyn A.; Bamman, Marcas M.; Clemens, Thomas L.

    2010-01-01

    Skeletal muscle development, nutrient uptake, and nutrient utilization is largely coordinated by growth hormone (GH) and its downstream effectors, in particular, IGF-1. However, it is not clear which effects of GH on skeletal muscle are direct and which are secondary to GH-induced IGF-1 expression. Thus, we generated mice lacking either GH receptor (GHR) or IGF-1 receptor (IGF-1R) specifically in skeletal muscle. Both exhibited impaired skeletal muscle development characterized by reductions in myofiber number and area as well as accompanying deficiencies in functional performance. Defective skeletal muscle development, in both GHR and IGF-1R mutants, was attributable to diminished myoblast fusion and associated with compromised nuclear factor of activated T cells import and activity. Strikingly, mice lacking GHR developed metabolic features that were not observed in the IGF-1R mutants, including marked peripheral adiposity, insulin resistance, and glucose intolerance. Insulin resistance in GHR-deficient myotubes derived from reduced IR protein abundance and increased inhibitory phosphorylation of IRS-1 on Ser 1101. These results identify distinct signaling pathways through which GHR regulates skeletal muscle development and modulates nutrient metabolism. PMID:20921627

  9. Contrasting growth modes of Ru thin film nano-structures on Si and Pd

    NASA Astrophysics Data System (ADS)

    Yin, Xiangshi; Teng, Ao; Özer, Mustafa; Weitering, Hanno; Snijders, Paul

    2011-03-01

    We have studied Ruthenium thin film growth on both Si (111) and Pd (111) surfaces. The films were deposited at low (LN2) temperature and at room temperature, and subsequently annealed at elevated temperatures, up to 600C. The surface structure, morphology, and chemical composition were investigated by LEED, STM, AES and XPS. Upon deposition at low temperature, nanoclusters are formed on both Si and Pd. Remarkably, the nanoclusters are approximately 3 nm in diameter and exhibit narrow size distributions on both substrates. In the case of Ru on Si, XPS spectra indicate silicide formation at the interface above 300C, but the nanocluster surface morphology survives up to 600C. On the other hand, nanoclusters on Pd smoothen into atomically flat films above 200C. The striking difference in adatom mobilities on these substrates is surprising in light of the very high melting temperature of Ru (2400C). Research (PCS) sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

  10. Non-canonical signaling mode of the epidermal growth factor receptor family

    PubMed Central

    Lee, Heng-Huan; Wang, Ying-Nai; Hung, Mien-Chie

    2015-01-01

    Epidermal growth factor receptor (EGFR) and its family members are key players in both physiological and pathological settings for which they are well recognized as models for investigating the functions and regulations of other membrane receptor tyrosine kinases (RTKs) and serve as therapeutic targets critical to clinical need and fundamental research. The canonical view of the pivotal functions in the EGFR family has been well documented as being an initiator of signaling amplification cascades from the plasma membrane to different subcellular compartments via receptor endocytic trafficking, intermolecular interaction, and kinase-substrate reaction in a temporalspatial manner. However, several lines of evidence have identified non-canonical roles of the EGFR family, acting as a transcriptional factor and a chromatin regulator in the nucleus to regulate gene expression, DNA replication, and DNA damage repair. Moreover, the EGFR family can even exert its impact outside the host cell through exosomal vesicle secretion. The emerging concept of the non-canonical roles of the EGFR family reveals an astonishing and elaborate scheme on the molecular functions of membrane RTKs, offering new insights into the receptor biology as well as the development of comprehensive therapeutic strategies in the future. PMID:26693051

  11. 2D Colloidal Wigner crystals in confined geometries

    NASA Astrophysics Data System (ADS)

    Higler, Ruben; Sprakel, Joris

    2015-03-01

    Crystallization of bulk systems has been widely studied using colloids as a model system. However, study into colloidal crystallization in confined geometries has been sparse and little is known about the effects of strong confinement on the dynamics of colloidal crystal. In our research we prepare 2D crystals from charged colloids in an apolar solvent to study crystal dynamics, formation, and structure in circular confinements. These confining geometries are made using softlithography techniques from SU-8. In order to broaden the parameter space we can reach in experiments we employ brownian dynamics simulations to supplement our experimental results. Using single-particle tracking we have subpixel resolution positional information of every particle in the system. We study the vibrational modes of our confined crystals and find well defined modes unique to confined systems, such as a radially symmetric compression (or breathing) mode, a collective rotation mode, and distinct resonance modes. Furthermore, due to the circular nature of our constrictions, defectless crystals are impossible, we find, for sufficiently high area fractions, that the defects order at well defined points at the edge. The effect of this ``defect-localization'' has a clear influence on the vibrational modes.

  12. Influence of variable operating modes of a steam turbine on the growth of creep cracks in the metal of shell parts made of austenitic steel

    NASA Astrophysics Data System (ADS)

    Gladshtein, V. I.

    2011-09-01

    Results obtained from assessing the crack resistance of type EI-612 VDP steel by testing notched cylindrical samples under the temperature and stress conditions simulating the loading of metal in shell parts in variable operating modes of a steam turbine are presented. Recommendations for conducting variable operating modes and for the time of carrying out operational checks are given taking into account the influence of cyclic loading on the growth of cracks.

  13. Brittle damage models in DYNA2D

    SciTech Connect

    Faux, D.R.

    1997-09-01

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

  14. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-01-01

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

  15. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-12-31

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

  16. 2D electronic materials for army applications

    NASA Astrophysics Data System (ADS)

    O'Regan, Terrance; Perconti, Philip

    2015-05-01

    The record electronic properties achieved in monolayer graphene and related 2D materials such as molybdenum disulfide and hexagonal boron nitride show promise for revolutionary high-speed and low-power electronic devices. Heterogeneous 2D-stacked materials may create enabling technology for future communication and computation applications to meet soldier requirements. For instance, transparent, flexible and even wearable systems may become feasible. With soldier and squad level electronic power demands increasing, the Army is committed to developing and harnessing graphene-like 2D materials for compact low size-weight-and-power-cost (SWAP-C) systems. This paper will review developments in 2D electronic materials at the Army Research Laboratory over the last five years and discuss directions for future army applications.

  17. 2-d Finite Element Code Postprocessor

    1996-07-15

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

  18. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

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

  19. Beam-Plasma Instabilities in a 2D Yukawa Lattice

    SciTech Connect

    Kyrkos, S.; Kalman, G. J.; Rosenberg, M.

    2009-06-05

    We consider a 2D Yukawa lattice of grains, with a beam of other charged grains moving in the lattice plane. In contrast to Vlasov plasmas, where the electrostatic instability excited by the beam is only longitudinal, here both longitudinal and transverse instabilities of the lattice phonons can develop. We determine and compare the transverse and longitudinal growth rates. The growth rate spectrum in wave number space exhibits remarkable gaps where no instability can develop. Depending on the system parameters, the transverse instability can be selectively excited.

  20. Factors influencing the temporal growth rate of the high order TM{sub 0n} modes in the Ka-band overmoded Cherenkov oscillator

    SciTech Connect

    Wu, Dapeng Shu, Ting; Ju, Jinchuan

    2015-06-15

    When the wavelength of overmoded Cherenkov oscillator goes into Ka-band, power handling capacity becomes an essential issue. Using the TM{sub 02} mode or higher order TM{sub 0n} modes as the operating mode is a potential solution. This paper is aimed to find some proper parameters to make the temporal growth rate of the TM{sub 02} mode higher in our previously studied Gigawatt (GW)-class Ka band oscillator. An accurate and fast calculation method of the “hot” dispersion equation is derived for rectangular corrugated SWSs, which are widely used in the high frequency Cherenkov devices. Then, factors that affect the temporal growth rate of the high order TM{sub 0n} modes are analyzed, including the depth of corrugation, the radius of drift tube, and the diode voltage. Results show that, when parameters are chosen properly, the temporal growth rate of the TM{sub 02} mode can be as high as 0.3 ns{sup −1}.

  1. Correlated Electron Phenomena in 2D Materials

    NASA Astrophysics Data System (ADS)

    Lambert, Joseph G.

    In this thesis, I present experimental results on coherent electron phenomena in layered two-dimensional materials: single layer graphene and van der Waals coupled 2D TiSe2. Graphene is a two-dimensional single-atom thick sheet of carbon atoms first derived from bulk graphite by the mechanical exfoliation technique in 2004. Low-energy charge carriers in graphene behave like massless Dirac fermions, and their density can be easily tuned between electron-rich and hole-rich quasiparticles with electrostatic gating techniques. The sharp interfaces between regions of different carrier densities form barriers with selective transmission, making them behave as partially reflecting mirrors. When two of these interfaces are set at a separation distance within the phase coherence length of the carriers, they form an electronic version of a Fabry-Perot cavity. I present measurements and analysis of multiple Fabry-Perot modes in graphene with parallel electrodes spaced a few hundred nanometers apart. Transition metal dichalcogenide (TMD) TiSe2 is part of the family of materials that coined the term "materials beyond graphene". It contains van der Waals coupled trilayer stacks of Se-Ti-Se. Many TMD materials exhibit a host of interesting correlated electronic phases. In particular, TiSe2 exhibits chiral charge density waves (CDW) below TCDW ˜ 200 K. Upon doping with copper, the CDW state gets suppressed with Cu concentration, and CuxTiSe2 becomes superconducting with critical temperature of T c = 4.15 K. There is still much debate over the mechanisms governing the coexistence of the two correlated electronic phases---CDW and superconductivity. I will present some of the first conductance spectroscopy measurements of proximity coupled superconductor-CDW systems. Measurements reveal a proximity-induced critical current at the Nb-TiSe2 interfaces, suggesting pair correlations in the pure TiSe2. The results indicate that superconducting order is present concurrently with CDW in

  2. Extended 2D generalized dilaton gravity theories

    NASA Astrophysics Data System (ADS)

    de Mello, R. O.

    2008-09-01

    We show that an anomaly-free description of matter in (1+1) dimensions requires a deformation of the 2D relativity principle, which introduces a non-trivial centre in the 2D Poincaré algebra. Then we work out the reduced phase space of the anomaly-free 2D relativistic particle, in order to show that it lives in a noncommutative 2D Minkowski space. Moreover, we build a Gaussian wave packet to show that a Planck length is well defined in two dimensions. In order to provide a gravitational interpretation for this noncommutativity, we propose to extend the usual 2D generalized dilaton gravity models by a specific Maxwell component, which guages the extra symmetry associated with the centre of the 2D Poincaré algebra. In addition, we show that this extension is a high energy correction to the unextended dilaton theories that can affect the topology of spacetime. Further, we couple a test particle to the general extended dilaton models with the purpose of showing that they predict a noncommutativity in curved spacetime, which is locally described by a Moyal star product in the low energy limit. We also conjecture a probable generalization of this result, which provides strong evidence that the noncommutativity is described by a certain star product which is not of the Moyal type at high energies. Finally, we prove that the extended dilaton theories can be formulated as Poisson Sigma models based on a nonlinear deformation of the extended Poincaré algebra.

  3. The physics of 2D microfluidic droplet ensembles

    NASA Astrophysics Data System (ADS)

    Beatus, Tsevi; Bar-Ziv, Roy H.; Tlusty, Tsvi

    2012-07-01

    We review non-equilibrium many-body phenomena in ensembles of 2D microfluidic droplets. The system comprises of continuous two-phase flow with disc-shaped droplets driven in a channel, at low Reynolds number of 10-4-10-3. The basic physics is that of an effective potential flow, governed by the 2D Laplace equation, with multiple, static and dynamic, boundaries of the droplets and the walls. The motion of the droplets induces dipolar flow fields, which mediate 1/r2 hydrodynamic interaction between the droplets. Summation of these long-range 2D forces over droplet ensembles converges, in contrast to the divergence of the hydrodynamic forces in 3D. In analogy to electrostatics, the strong effect of boundaries on the equations of motion is calculated by means of image dipoles. We first consider the dynamics of droplets flowing in a 1D crystal, which exhibits unique phonon-like excitations, and a variety of nonlinear instabilities-all stemming from the hydrodynamic interactions. Narrowing the channel results in hydrodynamic screening of the dipolar interactions, which changes salient features of the phonon spectra. Shifting from a 1D ordered crystal to 2D disordered ensemble, the hydrodynamic interactions induce collective density waves and shocks, which are superposed on single-droplet randomized motion and dynamic clustering. These collective modes originate from density-velocity coupling, whose outcome is a 1D Burgers equation. The rich observational phenomenology and the tractable theory render 2D droplet ensembles a suitable table-top system for studying non-equilibrium many-body physics with long-range interactions.

  4. 2D-patterning of self-assembled silver nanoisland films.

    PubMed

    Chervinskii, Semen; Reduto, Igor; Kamenskii, Alexander; Mukhin, Ivan S; Lipovskii, Andrey A

    2016-01-01

    The paper is dedicated to the recently developed by the authors technique of silver nanoisland growth, allowing self-arrangement of 2D-patterns of nanoislands. The technique employs silver out-diffusion from ion-exchanged glass in the course of annealing in hydrogen. To modify the silver ion distribution in the exchanged soda-lime glass we included the thermal poling of the ion-exchanged glass with a profiled electrode as an intermediate stage of the process. The resulting consequence consists of three steps: (i) during the ion exchange of the glass in the AgxNa1-xNO3 (x = 0.01-0.15) melt we enrich the subsurface layer of the glass with silver ions; (ii) under the thermal poling, the electric field displaces these ions deeper into the glass under the 2D profiled anodic electrode, the displacement is smaller under the hollows in the electrode where the intensity of the field is minimal; (iii) annealing in a reducing atmosphere of hydrogen results in silver out-diffusion only in the regions corresponding to the electrode hollows, as a result silver forms nanoislands following the shape of the electrode. Varying the electrode and mode of processing allows governing the nanoisland size distribution and self-arrangement of the isolated single nanoislands, pairs, triples or groups of several nanoislands-so-called plasmonic molecules. PMID:26765367

  5. A 2D channel-clogging biofilm model.

    PubMed

    Winstanley, H F; Chapwanya, M; Fowler, A C; O'Brien, S B G

    2015-09-01

    We present a model of biofilm growth in a long channel where the biomass is assumed to have the rheology of a viscous polymer solution. We examine the competition between growth and erosion-like surface detachment due to the flow. A particular focus of our investigation is the effect of the biofilm growth on the fluid flow in the pores, and the issue of whether biomass can grow sufficiently to shut off fluid flow through the pores, thus clogging the pore space. Net biofilm growth is coupled along the pore length via flow rate and nutrient transport in the pore flow. Our 2D model extends existing results on stability of 1D steady state biofilm thicknesses to show that, in the case of flows driven by a fixed pressure drop, full clogging of the pore can indeed happen in certain cases dependent on the functional form of the detachment term. PMID:25240390

  6. Global 2-D intercomparison of sectional and modal aerosol modules

    SciTech Connect

    Weisenstein, D K; Penner, J E; Herzog, M; Liu, Xiaohong

    2007-05-08

    We present an intercomparison of two aerosol modules, one sectional, one modal, in a global 2-D model in order to differentiate their behavior for tropospheric and stratospheric applications. We model only binary sulfuric acid-water aerosols in this study. Two versions of the sec-tional model and three versions of the modal model are used to test the sensitivity of background aerosol mass and size distribution to the number of bins or modes and to the pre-scribed width of the largest mode. We find modest sensitivity to the number of bins (40 vs 150) used in the sectional model. Aerosol mass is found to be reduced in a modal model if care is not taken in selecting the width of the largest lognormal mode, reflecting differences in sedimentation in the middle stratosphere. The size distributions calculated by the sec-tional model can be better matched by a modal model with four modes rather than three modes in most but not all sit-uations. A simulation of aerosol decay following the 1991 eruption of Mt. Pinatubo shows that the representation of the size distribution can have a signflcant impact on model-calculated aerosol decay rates in the stratosphere. Between 1991 and 1995, aerosol mass and surface area density calcu-lated by two versions of the modal model adequately match results from the sectional model. Calculated effective radius for the same time period shows more intermodel variability.

  7. Analysis of the Numerical and Geometrical Parameters Influencing the Simulation of Mode I and Mode II Delamination Growth in Unidirectional and Textile Composites

    NASA Astrophysics Data System (ADS)

    Jacques, S.; De Baere, I.; Van Paepegem, W.

    2015-12-01

    The reliability of composite structures depends, among other damage mechanisms, on their ability to withstand delaminations. In order to have a better understanding of the cohesive zone method technique for delamination simulations, a complete analysis of the multiple parameters influencing the results is necessary. In this paper the work is concentrated on the cohesive zone method using cohesive elements. First a summary of the theory of the cohesive zone method is given. A numerical investigation on the multiple parameters influencing the numerical simulation of the mode I and mode II delamination tests has been performed. The parameters such as the stabilization method, the output frequency, the friction and the computational efficiency have been taken into account. The results will be compared to an analytical solution obtained by linear elastic fracture mechanics. Additionally the numerical simulation results will be compared to the experimental results of a glass-fibre reinforced composite material for the mode I Double Cantilever Beam (DCB) and to a carbon fibre 5-harness satin weave reinforced polyphenylene sulphide composite for the mode I DCB and mode II End Notched Flexure (ENF).

  8. Human tumor-derived exosomes down-modulate NKG2D expression.

    PubMed

    Clayton, Aled; Mitchell, J Paul; Court, Jacquelyn; Linnane, Seamus; Mason, Malcolm D; Tabi, Zsuzsanna

    2008-06-01

    NKG2D is an activating receptor for NK, NKT, CD8(+), and gammadelta(+) T cells, whose aberrant loss in cancer is a key mechanism of immune evasion. Soluble NKG2D ligands and growth factors, such as TGFbeta1 emanating from tumors, are mechanisms for down-regulating NKG2D expression. Cancers thereby impair the capacity of lymphocytes to recognize and destroy them. In this study, we show that exosomes derived from cancer cells express ligands for NKG2D and express TGFbeta1, and we investigate the impact of such exosomes on CD8(+) T and NK cell NKG2D expression and on NKG2D-dependent functions. Exosomes produced by various cancer cell lines in vitro, or isolated from pleural effusions of mesothelioma patients triggered down-regulation of surface NKG2D expression by NK cells and CD8(+) T cells. This decrease was rapid, sustained, and resulted from direct interactions between exosomes and NK cells or CD8(+) T cells. Other markers (CD4, CD8, CD56, CD16, CD94, or CD69) remained unchanged, indicating the selectivity and nonactivatory nature of the response. Exosomal NKG2D ligands were partially responsible for this effect, as down-modulation of NKG2D was slightly attenuated in the presence of MICA-specific Ab. In contrast, TGFbeta1-neutralizing Ab strongly abrogated NKG2D down-modulation, suggesting exosomally expressed TGFbeta as the principal mechanism. Lymphocyte effector function was impaired by pretreatment with tumor exosomes, as these cells exhibited poor NKG2D-dependent production of IFN-gamma and poor NKG2D-dependent killing function. This hyporesponsiveness was evident even in the presence of IL-15, a strong inducer of NKG2D. Our data show that NKG2D is a likely physiological target for exosome-mediated immune evasion in cancer. PMID:18490724

  9. Stilbene 5c, A Microtubule Poison with Vascular Disrupting Properties That Induces Multiple Modes of Growth Arrest and Cell Death

    PubMed Central

    Alotaibi, M.R.; Asnake, B.; Xu, Di; Beckman, M.J.; Durrant, D; Simoni, D; Baruchello, R; Lee, R. M.; Schwartz, E.L.; Gewirtz, D.A.

    2013-01-01

    The stilbene derivative, cis-3, 4’, 5-trimethoxy-3’-aminostilbene (stilbene 5c), is a potentially potent antitumor agent that acts via binding to the colchicine-binding site in tubulin. The current studies were designed to investigate the effectiveness of stilbene 5c against the HCT-116 human colon cancer cell line and B16/F10 melanoma cells as well as human endothelial cell formation and tumor perfusion. Stilbene 5c produced a time-dependent decrease in cell viability in both cell lines and the capacity of the cells to proliferate was not restored upon removal of the drug. Treatment with stilbene 5c also promoted both senescence and autophagy in both cell lines. TUNEL and annexin 5 staining indicated that apoptosis also occurs in stilbene 5c-treated HCT-116 cells, but not in B16/F10 melanoma cells. DAPI staining revealed morphological changes in the cell nuclei (binucleated and micronucleated cells) indicative of mitotic catastrophe in HCT-116 cells but not in the B16/F10 melanoma cells. p53-null HCT-116 cells demonstrated a similar growth arrest/cell death response to stilbene as p53-wild type HCT-116 cells. Stilbene 5c also completely inhibited human endothelial cell tube formation on Matrigel, consistent with potential anti-angiogenic actions. Using a new method developed for monitoring the pharmacodynamic effects of stilbene 5c in vivo, we found that a single injection of stilbene 5c reduced tumor perfusion by 65% at 4 hours, returning to baseline by 24 hours, while subsequent daily injections of stilbene 5c produced progressively larger reductions and smaller rebounds. This work indicates that stilbene 5c could potentially be effective against melanoma and colon cancer through the promotion of multiple modes of growth arrest and cell death coupled with anti-angiogenic and antivascular actions. PMID:24144631

  10. Stilbene 5c, a microtubule poison with vascular disrupting properties that induces multiple modes of growth arrest and cell death.

    PubMed

    Alotaibi, M R; Asnake, B; Di, Xu; Beckman, M J; Durrant, D; Simoni, D; Baruchello, R; Lee, R M; Schwartz, E L; Gewirtz, D A

    2013-12-15

    The stilbene derivative, cis-3,4',5-trimethoxy-3'-aminostilbene (stilbene 5c), is a potentially potent antitumor agent that acts via binding to the colchicine-binding site in tubulin. The current studies were designed to investigate the effectiveness of stilbene 5c against the HCT-116 human colon cancer cell line and B16/F10 melanoma cells as well as human endothelial cell tube formation and tumor perfusion. Stilbene 5c produced a time-dependent decrease in cell viability in both cell lines and the capacity of the cells to proliferate was not restored upon removal of the drug. Treatment with stilbene 5c also promoted both senescence and autophagy in both cell lines. TUNEL and annexin 5 staining indicated that apoptosis also occurs in stilbene 5c-treated HCT-116 cells, but not in B16/F10 melanoma cells. DAPI staining revealed morphological changes in the cell nuclei (binucleated and micronucleated cells) indicative of mitotic catastrophe in HCT-116 cells but not in the B16/F10 melanoma cells. p53-null HCT-116 cells demonstrated a similar growth arrest/cell death response to stilbene as p53-wild type HCT-116 cells. Stilbene 5c also completely inhibited human endothelial cell tube formation on Matrigel, consistent with potential anti-angiogenic actions. Using a new method developed for monitoring the pharmacodynamic effects of stilbene 5c in vivo, we found that a single injection of stilbene 5c reduced tumor perfusion by 65% at 4h, returning to baseline by 24h, while subsequent daily injections of stilbene 5c produced progressively larger reductions and smaller rebounds. This work indicates that stilbene 5c could potentially be effective against melanoma and colon cancer through the promotion of multiple modes of growth arrest and cell death coupled with anti-angiogenic and antivascular actions. PMID:24144631

  11. A Microplate Growth Inhibition Assay for Screening Bacteriocins against Listeria monocytogenes to Differentiate Their Mode-of-Action

    PubMed Central

    Vijayakumar, Paul Priyesh; Muriana, Peter M.

    2015-01-01

    Lactic acid bacteria (LAB) have historically been used in food fermentations to preserve foods and are generally-recognized-as-safe (GRAS) by the FDA for use as food ingredients. In addition to lactic acid; some strains also produce bacteriocins that have been proposed for use as food preservatives. In this study we examined the inhibition of Listeria monocytogenes 39-2 by neutralized and non-neutralized bacteriocin preparations (Bac+ preps) produced by Lactobacillus curvatus FS47; Lb. curvatus Beef3; Pediococcus acidilactici Bac3; Lactococcus lactis FLS1; Enterococcus faecium FS56-1; and Enterococcus thailandicus FS92. Activity differences between non-neutralized and neutralized Bac+ preps in agar spot assays could not readily be attributed to acid because a bacteriocin-negative control strain was not inhibitory to Listeria in these assays. When neutralized and non-neutralized Bac+ preps were used in microplate growth inhibition assays against L. monocytogenes 39-2 we observed some differences attributed to acid inhibition. A microplate growth inhibition assay was used to compare inhibitory reactions of wild-type and bacteriocin-resistant variants of L. monocytogenes to differentiate bacteriocins with different modes-of-action (MOA) whereby curvaticins FS47 and Beef3, and pediocin Bac3 were categorized to be in MOA1; enterocins FS92 and FS56-1 in MOA2; and lacticin FLS1 in MOA3. The microplate bacteriocin MOA assay establishes a platform to evaluate the best combination of bacteriocin preparations for use in food applications as biopreservatives against L. monocytogenes. PMID:26111195

  12. The Membrane-anchoring Domain of Epidermal Growth Factor Receptor Ligands Dictates Their Ability to Operate in Juxtacrine Mode

    SciTech Connect

    Dong, Jianying; Opresko, Lee; Chrisler, William B.; Orr, Galya; Quesenberry, Ryan D.; Lauffenburger, Douglas A.; Wiley, H S.

    2005-06-01

    All ligands of the epidermal growth factor receptor (EGFR) are synthesized as membrane-anchored precursors. Previous work has suggested that some ligands, such as EGF, must be proteolytically released to be active, whereas others, such as heparin binding EGF-like growth factor (HB-EGF) can function while still anchored to the membrane (i.e., juxtacrine signaling). To explore the structural basis for these differences in ligand activity, we engineered a series of membrane-anchored ligands in which the core, receptor-binding domain of EGF was combined with different domains of both EGF and HB-EGF. We found that ligands having the N-terminal extension of EGF could not bind to the EGFR, even when released from the membrane. Ligands lacking an N-terminal extension, but possessing the membrane-anchoring domain of EGF still required proteolytic release for activity, whereas ligands with the membrane anchoring domain of HB-EGF could elicit full biological activity while still membrane anchored. Ligands containing the HB-EGF membrane anchor, but lacking an N-terminal extension, activated EGFR during their transit through the Golgi apparatus . However, cell-mixing experiments and fluorescence resonance energy transfer (FRET) studies showed that juxtacrine signaling typically occurred in trans at the cell surface, at points of cell-cell contact. Our data suggest that the membrane-anchoring domain of ligands selectively controls their ability to participate in juxtacrine signaling and thus, only a subclass of EGFR ligands can act in a juxtacrine mode.

  13. Optical modulators with 2D layered materials

    NASA Astrophysics Data System (ADS)

    Sun, Zhipei; Martinez, Amos; Wang, Feng

    2016-04-01

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

  14. Large Area Synthesis of 2D Materials

    NASA Astrophysics Data System (ADS)

    Vogel, Eric

    Transition metal dichalcogenides (TMDs) have generated significant interest for numerous applications including sensors, flexible electronics, heterostructures and optoelectronics due to their interesting, thickness-dependent properties. Despite recent progress, the synthesis of high-quality and highly uniform TMDs on a large scale is still a challenge. In this talk, synthesis routes for WSe2 and MoS2 that achieve monolayer thickness uniformity across large area substrates with electrical properties equivalent to geological crystals will be described. Controlled doping of 2D semiconductors is also critically required. However, methods established for conventional semiconductors, such as ion implantation, are not easily applicable to 2D materials because of their atomically thin structure. Redox-active molecular dopants will be demonstrated which provide large changes in carrier density and workfunction through the choice of dopant, treatment time, and the solution concentration. Finally, several applications of these large-area, uniform 2D materials will be described including heterostructures, biosensors and strain sensors.

  15. 2D microwave imaging reflectometer electronics

    SciTech Connect

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

    2014-11-15

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

  16. 2D microwave imaging reflectometer electronics

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  17. 2D microwave imaging reflectometer electronics.

    PubMed

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

    2014-11-01

    A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program. PMID:25430247

  18. 2D-Crystal-Based Functional Inks.

    PubMed

    Bonaccorso, Francesco; Bartolotta, Antonino; Coleman, Jonathan N; Backes, Claudia

    2016-08-01

    The possibility to produce and process graphene, related 2D crystals, and heterostructures in the liquid phase makes them promising materials for an ever-growing class of applications as composite materials, sensors, in flexible optoelectronics, and energy storage and conversion. In particular, the ability to formulate functional inks with on-demand rheological and morphological properties, i.e., lateral size and thickness of the dispersed 2D crystals, is a step forward toward the development of industrial-scale, reliable, inexpensive printing/coating processes, a boost for the full exploitation of such nanomaterials. Here, the exfoliation strategies of graphite and other layered crystals are reviewed, along with the advances in the sorting of lateral size and thickness of the exfoliated sheets together with the formulation of functional inks and the current development of printing/coating processes of interest for the realization of 2D-crystal-based devices. PMID:27273554

  19. Mode of Occurrence and Cause of Cracking of Li2B4O7 Single Crystals during Growth by Czochralski Method

    NASA Astrophysics Data System (ADS)

    Komatsu, Ryuichi; Uda, Satoshi; Hikita, Kazuyasu

    1993-09-01

    The mode of occurrence and the origin of cracking of lithium tetraborate (Li2B4O7) single crystals during growth have been investigated. The melt temperature dependence and the origin of crystal cracking have been explained in terms of activation enthalpy change for viscous flow in Li2B4O7 melt associated with temperature distribution in the melt.

  20. 2D Regimes of Non-Fourier Convection

    NASA Astrophysics Data System (ADS)

    Papanicolaou, N. C.

    2010-11-01

    In this work, we investigate the 2D flow in a rectangular cavity subject to both vertical and horizontal temperature gradients. The linearized model is studied and the effect of thermal relaxation, as described by the Maxwell-Cattaneo law of heat conduction is examined. To this end, a spectral numerical model is created based on a Galerkin expansion. The basis is the Cartesian product of systems of beam functions and trigonometric functions. The natural modes of the system are derived for both the Fourier and non-Fourier models. The results are compared to earlier works for the plain Fourier law. Our computations show that for the same set of parameters, the Maxwell-Cattaneo law yields modes which are quantitatively different from the Fourier. It is found that the real parts of the eigenvalues increase with the Straughan number Sg, which quantifies the non-Fourier effects. This confirms the destabilizing effect of the MC-law on the convective flow.

  1. Symmetry detection of auxetic behaviour in 2D frameworks

    NASA Astrophysics Data System (ADS)

    Mitschke, H.; Schröder-Turk, G. E.; Mecke, K.; Fowler, P. W.; Guest, S. D.

    2013-06-01

    A symmetry-extended Maxwell treatment of the net mobility of periodic bar-and-joint frameworks is used to derive a sufficient condition for auxetic behaviour of a 2D material. The type of auxetic behaviour that can be detected by symmetry has Poisson's ratio -1, with equal expansion/contraction in all directions, and is here termed equiauxetic. A framework may have a symmetry-detectable equiauxetic mechanism if it belongs to a plane group that includes rotational axes of order n = 6, 4, or 3. If the reducible representation for the net mobility contains mechanisms that preserve full rotational symmetry (A modes), these are equiauxetic. In addition, for n = 6, mechanisms that halve rotational symmetry (B modes) are also equiauxetic.

  2. Resolving 2D Amorphous Materials with Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Burson, Kristen M.; Buechner, Christin; Lewandowski, Adrian; Heyde, Markus; Freund, Hans-Joachim

    Novel two-dimensional (2D) materials have garnered significant scientific interest due to their potential technological applications. Alongside the emphasis on crystalline materials, such as graphene and hexagonal BN, a new class of 2D amorphous materials must be pursued. For amorphous materials, a detailed understanding of the complex structure is necessary. Here we present a structural study of 2D bilayer silica on Ru(0001), an insulating material which is weakly coupled to the substrate. Atomic structure has been determined with a dual mode atomic force microscopy (AFM) and scanning tunneling microscopy (STM) sensor in ultra-high vacuum (UHV) at low temperatures, revealing a network of different ring sizes. Liquid AFM measurements with sub-nanometer resolution bridge the gap between clean UHV conditions and the environments that many material applications demand. Samples are grown and characterized in vacuum and subsequently transferred to the liquid AFM. Notably, the key structural features observed, namely nanoscale ring networks and larger holes to the substrate, show strong quantitative agreement between the liquid and UHV microscopy measurements. This provides direct evidence for the structural stability of these silica films for nanoelectronics and other applications. KMB acknowledges support from the Alexander von Humboldt Foundation.

  3. The 2D lingual appliance system.

    PubMed

    Cacciafesta, Vittorio

    2013-09-01

    The two-dimensional (2D) lingual bracket system represents a valuable treatment option for adult patients seeking a completely invisible orthodontic appliance. The ease of direct or simplified indirect bonding of 2D lingual brackets in combination with low friction mechanics makes it possible to achieve a good functional and aesthetic occlusion, even in the presence of a severe malocclusion. The use of a self-ligating bracket significantly reduces chair-side time for the orthodontist, and the low-profile bracket design greatly improves patient comfort. PMID:24005953

  4. Inkjet printing of 2D layered materials.

    PubMed

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

    2014-11-10

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

  5. Measurement of 2D birefringence distribution

    NASA Astrophysics Data System (ADS)

    Noguchi, Masato; Ishikawa, Tsuyoshi; Ohno, Masahiro; Tachihara, Satoru

    1992-10-01

    A new measuring method of 2-D birefringence distribution has been developed. It has not been an easy job to get a birefringence distribution in an optical element with conventional ellipsometry because of its lack of scanning means. Finding an analogy between the rotating analyzer method in ellipsometry and the phase-shifting method in recently developed digital interferometry, we have applied the phase-shifting algorithm to ellipsometry, and have developed a new method that makes the measurement of 2-D birefringence distribution easy and possible. The system contains few moving parts, assuring reliability, and measures a large area of a sample at one time, making the measuring time very short.

  6. Impact of Actinobacillus pleuropneumoniae biofilm mode of growth on the lipid A structures and stimulation of immune cells.

    PubMed

    Hathroubi, Skander; Beaudry, Francis; Provost, Chantale; Martelet, Léa; Segura, Mariela; Gagnon, Carl A; Jacques, Mario

    2016-07-01

    Actinobacillus pleuropneumoniae (APP), the etiologic agent of porcine pleuropneumonia, forms biofilms on biotic and abiotic surfaces. APP biofilms confers resistance to antibiotics. To our knowledge, no studies have examined the role of APP biofilm in immune evasion and infection persistence. This study was undertaken to (i) investigate biofilm-associated LPS modifications occurring during the switch to biofilm mode of growth; and (ii) characterize pro-inflammatory cytokines expression in porcine pulmonary alveolar macrophages (PAMs) and proliferation in porcine PBMCs challenged with planktonic or biofilm APP cells. Extracted lipid A samples from biofilm and planktonic cultures were analyzed by HPLC high-resolution, accurate mass spectrometry. Biofilm cells displayed significant changes in lipid A profiles when compared with their planktonic counterparts. Furthermore, in vitro experiments were conducted to examine the inflammatory response of PAMs exposed to UV-inactivated APP grown in biofilm or in suspension. Relative mRNA expression of pro-inflammatory genes IL1, IL6, IL8 and MCP1 decreased in PAMs when exposed to biofilm cells compared to planktonic cells. Additionally, the biofilm state reduced PBMCs proliferation. Taken together, APP biofilm cells show a weaker ability to stimulate innate immune cells, which could be due, in part, to lipid A structure modifications. PMID:27226465

  7. Growth Mode and Threading Dislocation Behavior of GaN Films Grown on Patterned Sapphire Substrate with Radial Stripe Pattern

    NASA Astrophysics Data System (ADS)

    Okuno, Koji; Oshio, Takahide; Shibata, Naoki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi

    2013-08-01

    A sapphire substrate with a grooved stripe pattern along different radial directions was prepared to investigate the effects of stripe direction on the growth mode and threading dislocation (TD) behavior of GaN films. When the stripe direction is oriented parallel to [10bar 10]sapphire, the GaN films have a triangular structure that is formed by the GaN{10bar 11} facets. As the stripe direction rotates from [10bar 10]sapphire, nanosteps with a step height of around 80 nm are formed on the GaN{10bar 11} facets and then the coalescence of GaN on the ridges and grooves advances. GaN films with a smooth surface and a TD density as low as 2.0×108 cm-2 were achieved when the stripe direction was rotated 3° from [10bar 10]sapphire. Our result indicates that the surface roughness and TD density of GaN films can be controlled by precisely adjusting the angle of the stripe direction from [10bar 10]sapphire.

  8. Parallel stitching of 2D materials

    DOE PAGESBeta

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

    2016-01-27

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

  9. Parallel Stitching of 2D Materials.

    PubMed

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

    2016-03-01

    Diverse parallel stitched 2D heterostructures, including metal-semiconductor, semiconductor-semiconductor, and insulator-semiconductor, are synthesized directly through selective "sowing" of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. The methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits. PMID:26813882

  10. Baby universes in 2d quantum gravity

    NASA Astrophysics Data System (ADS)

    Ambjørn, Jan; Jain, Sanjay; Thorleifsson, Gudmar

    1993-06-01

    We investigate the fractal structure of 2d quantum gravity, both for pure gravity and for gravity coupled to multiple gaussian fields and for gravity coupled to Ising spins. The roughness of the surfaces is described in terms of baby universes and using numerical simulations we measure their distribution which is related to the string susceptibility exponent γstring.

  11. Lorenz-Mie theory for 2D scattering and resonance calculations

    NASA Astrophysics Data System (ADS)

    Gagnon, Denis; Dubé, Louis J.

    2015-10-01

    This PhD tutorial is concerned with a description of the two-dimensional generalized Lorenz-Mie theory (2D-GLMT), a well-established numerical method used to compute the interaction of light with arrays of cylindrical scatterers. This theory is based on the method of separation of variables and the application of an addition theorem for cylindrical functions. The purpose of this tutorial is to assemble the practical tools necessary to implement the 2D-GLMT method for the computation of scattering by passive scatterers or of resonances in optically active media. The first part contains a derivation of the vector and scalar Helmholtz equations for 2D geometries, starting from Maxwell’s equations. Optically active media are included in 2D-GLMT using a recent stationary formulation of the Maxwell-Bloch equations called steady-state ab initio laser theory (SALT), which introduces new classes of solutions useful for resonance computations. Following these preliminaries, a detailed description of 2D-GLMT is presented. The emphasis is placed on the derivation of beam-shape coefficients for scattering computations, as well as the computation of resonant modes using a combination of 2D-GLMT and SALT. The final section contains several numerical examples illustrating the full potential of 2D-GLMT for scattering and resonance computations. These examples, drawn from the literature, include the design of integrated polarization filters and the computation of optical modes of photonic crystal cavities and random lasers.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  14. Pistillate flower development and pollen tube growth mode during the delayed fertilization stage in Corylus heterophylla Fisch.

    PubMed

    Liu, Jianfeng; Zhang, Huidi; Cheng, Yunqing; Kafkas, Salih; Güney, Murat

    2014-09-01

    Unlike most angiosperms, in which fertilization occurs within several days after pollination, fertilization in hazel (Corylus Spp.) is delayed by two to three and a half months. However, the female inflorescences or young fruits are too hard or lignified to be dissected according to regular paraffin sectioning technique. So, what the nature of development during the extended progamic phases of hazel remains unknown. The female inflorescence development and pollen tube growth mode during the delayed fertilization stage in hazel were investigated by improved paraffin sectioning and aniline blue staining of pollen tubes. The results showed ovaries and ovules of hazel were invisible at the time of blooming. Early ovary and ovule primordium began to form from 15 to 20 days after blooming, respectively. Integument and mature embryo sacs differentiated from the nucellus on 40th and 55th day after blooming, respectively. Pollen tubes were retarded in the bottom of the style or the pollen tube cavity (PTC, a specifical lignified cavity structure at the bottom of style for pollen tube to rest during progamic phase) for about 26 days. Then, the pollen tubes were observed to leave the PTC and began to enter the ovary. After that, a single pollen tube passed through the vicinity of the micropyle. Finally, pollen tubes turned a corner and penetrated the embryo sac through the tissue of the chalaza instead of micropyle on 52 and 55 days after blooming, respectively. The results of more in-depth information will be beneficial to better understanding of the delayed fertilization process in hazel. PMID:25073757

  15. One-step growth of Si{sub 3}N{sub 4} stem-branch featured nanostructures: Morphology control by VS and VLS mode

    SciTech Connect

    Wang Qiushi; Gao Wei; Shan Lianchen; Zhang Jian; Jin Yunxia; Cong Ridong; Cui Qiliang

    2011-09-15

    We report here one-step synthesis of Si{sub 3}N{sub 4} nanodendrites by selectively applying a vapor-solid (VS) and vapor-liquid-solid (VLS) strategy via direct current arc discharge method. The resultant nanodendrites were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy and X-ray powder diffraction. The spine-shaped nanodendrites were generated by a noncatalytic growth following a VS mode. The uniform secondary nanowire branches were epitaxial grown from two side surfaces of the nanowire stems. The pine-shaped nanodendrites were obtained through a catalytic growth in a VLS process. These branch nanowires were unsystematically grown from the nanocone-like stems. The photoluminescence spectra of the nanodendrites show a strong white light emission around 400-750 nm, suggesting their potential applications in light and electron emission devices. - Graphical abstract: Spine-shaped and pine-shaped Si{sub 3}N{sub 4} hierarchical nanostructures were synthesized by VS and VLS mode with plasma-assisted dc arc discharge method. Highlights: > Si{sub 3}N{sub 4} stem-branch featured nanostructures have been prepared. > Spine-shaped nanodendrites were generated by a noncatalytic growth following a VS mode. > Pine-shaped nanodendrites were obtained through a catalytic growth in a VLS process.

  16. Static & Dynamic Response of 2D Solids

    1996-07-15

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

  17. Stochastic Inversion of 2D Magnetotelluric Data

    2010-07-01

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

  18. Stochastic Inversion of 2D Magnetotelluric Data

    SciTech Connect

    Chen, Jinsong

    2010-07-01

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

  19. Schottky diodes from 2D germanane

    NASA Astrophysics Data System (ADS)

    Sahoo, Nanda Gopal; Esteves, Richard J.; Punetha, Vinay Deep; Pestov, Dmitry; Arachchige, Indika U.; McLeskey, James T.

    2016-07-01

    We report on the fabrication and characterization of a Schottky diode made using 2D germanane (hydrogenated germanene). When compared to germanium, the 2D structure has higher electron mobility, an optimal band-gap, and exceptional stability making germanane an outstanding candidate for a variety of opto-electronic devices. One-atom-thick sheets of hydrogenated puckered germanium atoms have been synthesized from a CaGe2 framework via intercalation and characterized by XRD, Raman, and FTIR techniques. The material was then used to fabricate Schottky diodes by suspending the germanane in benzonitrile and drop-casting it onto interdigitated metal electrodes. The devices demonstrate significant rectifying behavior and the outstanding potential of this material.

  20. Layer Engineering of 2D Semiconductor Junctions.

    PubMed

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

    2016-07-01

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

  1. 2dF mechanical engineering

    NASA Astrophysics Data System (ADS)

    Smith, Greg; Lankshear, Allan

    1998-07-01

    2dF is a multi-object instrument mounted at prime focus at the AAT capable of spectroscopic analysis of 400 objects in a single 2 degree field. It also prepares a second 2 degree 400 object field while the first field is being observed. At its heart is a high precision robotic positioner that places individual fiber end magnetic buttons on one of two field plates. The button gripper is carried on orthogonal gantries powered by linear synchronous motors and contains a TV camera which precisely locates backlit buttons to allow placement in user defined locations to 10 (mu) accuracy. Fiducial points on both plates can also be observed by the camera to allow repeated checks on positioning accuracy. Field plates rotate to follow apparent sky rotation. The spectrographs both analyze light from the 200 observing fibers each and back- illuminate the 400 fibers being re-positioned during the observing run. The 2dF fiber position and spectrograph system is a large and complex instrument located at the prime focus of the Anglo Australian Telescope. The mechanical design has departed somewhat from the earlier concepts of Gray et al, but still reflects the audacity of those first ideas. The positioner is capable of positioning 400 fibers on a field plate while another 400 fibers on another plate are observing at the focus of the telescope and feeding the twin spectrographs. When first proposed it must have seemed like ingenuity unfettered by caution. Yet now it works, and works wonderfully well. 2dF is a system which functions as the result of the combined and coordinated efforts of the astronomers, the mechanical designers and tradespeople, the electronic designers, the programmers, the support staff at the telescope, and the manufacturing subcontractors. The mechanical design of the 2dF positioner and spectrographs was carried out by the mechanical engineering staff of the AAO and the majority of the manufacture was carried out in the AAO workshops.

  2. Realistic and efficient 2D crack simulation

    NASA Astrophysics Data System (ADS)

    Yadegar, Jacob; Liu, Xiaoqing; Singh, Abhishek

    2010-04-01

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

  3. Compact 2-D graphical representation of DNA

    NASA Astrophysics Data System (ADS)

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

    2003-05-01

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

  4. 2D materials: Graphene and others

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  5. TACO (2D AND 3D). Taco

    SciTech Connect

    Mason, W.E.

    1983-03-01

    A set of finite element codes for the solution of nonlinear, two-dimensional (TACO2D) and three-dimensional (TACO3D) heat transfer problems. Performs linear and nonlinear analyses of both transient and steady state heat transfer problems. Has the capability to handle time or temperature dependent material properties. Materials may be either isotropic or orthotropic. A variety of time and temperature dependent boundary conditions and loadings are available including temperature, flux, convection, radiation, and internal heat generation.

  6. Effects of 2D and Finite Density Fluctuations on O-X Correlation Reflectometry

    SciTech Connect

    G.J. Kramer; R. Nazikian; E. Valeo

    2001-07-05

    The correlation between O-mode and X-mode reflectometer signals is studied with a 1D and 2D reflectometer model in order to explore its feasibilities as a q-profile diagnostic. It was found that 2D effects and finite fluctuation levels both decrease the O-X correlation. At very low fluctuation levels, which are usually present in the plasma core, there is good possibility to determine the local magnetic field strength and use that as a constraint for the equilibrium reconstruction.

  7. Tomosynthesis imaging with 2D scanning trajectories

    NASA Astrophysics Data System (ADS)

    Khare, Kedar; Claus, Bernhard E. H.; Eberhard, Jeffrey W.

    2011-03-01

    Tomosynthesis imaging in chest radiography provides volumetric information with the potential for improved diagnostic value when compared to the standard AP or LAT projections. In this paper we explore the image quality benefits of 2D scanning trajectories when coupled with advanced image reconstruction approaches. It is intuitively clear that 2D trajectories provide projection data that is more complete in terms of Radon space filling, when compared with conventional tomosynthesis using a linearly scanned source. Incorporating this additional information for obtaining improved image quality is, however, not a straightforward problem. The typical tomosynthesis reconstruction algorithms are based on direct inversion methods e.g. Filtered Backprojection (FBP) or iterative algorithms that are variants of the Algebraic Reconstruction Technique (ART). The FBP approach is fast and provides high frequency details in the image but at the same time introduces streaking artifacts degrading the image quality. The iterative methods can reduce the image artifacts by using image priors but suffer from a slow convergence rate, thereby producing images lacking high frequency details. In this paper we propose using a fast converging optimal gradient iterative scheme that has advantages of both the FBP and iterative methods in that it produces images with high frequency details while reducing the image artifacts. We show that using favorable 2D scanning trajectories along with the proposed reconstruction method has the advantage of providing improved depth information for structures such as the spine and potentially producing images with more isotropic resolution.

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

    SciTech Connect

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

    1985-01-01

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

  9. Engineering light outcoupling in 2D materials.

    PubMed

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

    2015-02-11

    When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here, we report a simple method to engineer the light outcoupling in semiconducting TMDCs by modulating their dielectric surroundings. We show that by modulating the thicknesses of underlying substrates and capping layers, the interference caused by substrate can significantly enhance the light absorption and emission of WSe2, resulting in a ∼11 times increase in Raman signal and a ∼30 times increase in the photoluminescence (PL) intensity of WSe2. On the basis of the interference model, we also propose a strategy to control the photonic and optoelectronic properties of thin-layer WSe2. This work demonstrates the utilization of outcoupling engineering in 2D materials and offers a new route toward the realization of novel optoelectronic devices, such as 2D LEDs and solar cells. PMID:25602462

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    PubMed

    Wang, Zenghui; Feng, Philip X-L

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

    Elraghy, Omaima; Baldwin, William S

    2015-01-01

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

  14. 2D superconductivity by ionic gating

    NASA Astrophysics Data System (ADS)

    Iwasa, Yoshi

    2D superconductivity is attracting a renewed interest due to the discoveries of new highly crystalline 2D superconductors in the past decade. Superconductivity at the oxide interfaces triggered by LaAlO3/SrTiO3 has become one of the promising routes for creation of new 2D superconductors. Also, the MBE grown metallic monolayers including FeSe are also offering a new platform of 2D superconductors. In the last two years, there appear a variety of monolayer/bilayer superconductors fabricated by CVD or mechanical exfoliation. Among these, electric field induced superconductivity by electric double layer transistor (EDLT) is a unique platform of 2D superconductivity, because of its ability of high density charge accumulation, and also because of the versatility in terms of materials, stemming from oxides to organics and layered chalcogenides. In this presentation, the following issues of electric filed induced superconductivity will be addressed; (1) Tunable carrier density, (2) Weak pinning, (3) Absence of inversion symmetry. (1) Since the sheet carrier density is quasi-continuously tunable from 0 to the order of 1014 cm-2, one is able to establish an electronic phase diagram of superconductivity, which will be compared with that of bulk superconductors. (2) The thickness of superconductivity can be estimated as 2 - 10 nm, dependent on materials, and is much smaller than the in-plane coherence length. Such a thin but low resistance at normal state results in extremely weak pinning beyond the dirty Boson model in the amorphous metallic films. (3) Due to the electric filed, the inversion symmetry is inherently broken in EDLT. This feature appears in the enhancement of Pauli limit of the upper critical field for the in-plane magnetic fields. In transition metal dichalcogenide with a substantial spin-orbit interactions, we were able to confirm the stabilization of Cooper pair due to its spin-valley locking. This work has been supported by Grant-in-Aid for Specially

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

    SciTech Connect

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

    2006-11-01

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

  16. 2D to 3D conversion implemented in different hardware

    NASA Astrophysics Data System (ADS)

    Ramos-Diaz, Eduardo; Gonzalez-Huitron, Victor; Ponomaryov, Volodymyr I.; Hernandez-Fragoso, Araceli

    2015-02-01

    Conversion of available 2D data for release in 3D content is a hot topic for providers and for success of the 3D applications, in general. It naturally completely relies on virtual view synthesis of a second view given by original 2D video. Disparity map (DM) estimation is a central task in 3D generation but still follows a very difficult problem for rendering novel images precisely. There exist different approaches in DM reconstruction, among them manually and semiautomatic methods that can produce high quality DMs but they demonstrate hard time consuming and are computationally expensive. In this paper, several hardware implementations of designed frameworks for an automatic 3D color video generation based on 2D real video sequence are proposed. The novel framework includes simultaneous processing of stereo pairs using the following blocks: CIE L*a*b* color space conversions, stereo matching via pyramidal scheme, color segmentation by k-means on an a*b* color plane, and adaptive post-filtering, DM estimation using stereo matching between left and right images (or neighboring frames in a video), adaptive post-filtering, and finally, the anaglyph 3D scene generation. Novel technique has been implemented on DSP TMS320DM648, Matlab's Simulink module over a PC with Windows 7, and using graphic card (NVIDIA Quadro K2000) demonstrating that the proposed approach can be applied in real-time processing mode. The time values needed, mean Similarity Structural Index Measure (SSIM) and Bad Matching Pixels (B) values for different hardware implementations (GPU, Single CPU, and DSP) are exposed in this paper.

  17. Mode II fatigue crack propagation.

    NASA Technical Reports Server (NTRS)

    Roberts, R.; Kibler, J. J.

    1971-01-01

    Fatigue crack propagation rates were obtained for 2024-T3 bare aluminum plates subjected to in-plane, mode I, extensional loads and transverse, mode II, bending loads. These results were compared to the results of Iida and Kobayashi for in-plane mode I-mode II extensional loads. The engineering significance of mode I-mode II fatigue crack growth is considered in view of the present results. A fatigue crack growth equation for handling mode I-mode II fatigue crack growth rates from existing mode I data is also discussed.

  18. The Herschel view of the dominant mode of galaxy growth from z = 4 to the present day

    NASA Astrophysics Data System (ADS)

    Schreiber, C.; Pannella, M.; Elbaz, D.; Béthermin, M.; Inami, H.; Dickinson, M.; Magnelli, B.; Wang, T.; Aussel, H.; Daddi, E.; Juneau, S.; Shu, X.; Sargent, M. T.; Buat, V.; Faber, S. M.; Ferguson, H. C.; Giavalisco, M.; Koekemoer, A. M.; Magdis, G.; Morrison, G. E.; Papovich, C.; Santini, P.; Scott, D.

    2015-03-01

    We present an analysis of the deepest Herschel images in four major extragalactic fields GOODS-North, GOODS-South, UDS, and COSMOS obtained within the GOODS-Herschel and CANDELS-Herschel key programs. The star formation picture provided by a total of 10 497 individual far-infrared detections is supplemented by the stacking analysis of a mass complete sample of 62 361 star-forming galaxies from the Hubble Space Telescope (HST) H band-selected catalogs of the CANDELS survey and from two deep ground-based Ks band-selected catalogs in the GOODS-North and the COSMOS-wide field to obtain one of the most accurate and unbiased understanding to date of the stellar mass growth over the cosmic history. We show, for the first time, that stacking also provides a powerful tool to determine the dispersion of a physical correlation and describe our method called "scatter stacking", which may be easily generalized to other experiments. The combination of direct UV and far-infrared UV-reprocessed light provides a complete census on the star formation rates (SFRs), allowing us to demonstrate that galaxies at z = 4 to 0 of all stellar masses (M∗) follow a universal scaling law, the so-called main sequence of star-forming galaxies. We find a universal close-to-linear slope of the log 10(SFR)-log 10(M∗) relation, with evidence for a flattening of the main sequence at high masses (log 10(M∗/M⊙) > 10.5) that becomesless prominent with increasing redshift and almost vanishes by z ≃ 2. This flattening may be due to the parallel stellar growth of quiescent bulges in star-forming galaxies, which mostly happens over the same redshift range. Within the main sequence, we measure a nonvarying SFR dispersion of 0.3 dex: at a fixed redshift and stellar mass, about 68% of star-forming galaxies form stars at a universal rate within a factor 2. The specific SFR (sSFR = SFR/M∗) of star-forming galaxies is found to continuously increase from z = 0 to 4. Finally we discuss the implications of

  19. Interparticle Attraction in 2D Complex Plasmas

    NASA Astrophysics Data System (ADS)

    Kompaneets, Roman; Morfill, Gregor E.; Ivlev, Alexei V.

    2016-03-01

    Complex (dusty) plasmas allow experimental studies of various physical processes occurring in classical liquids and solids by directly observing individual microparticles. A major problem is that the interaction between microparticles is generally not molecularlike. In this Letter, we propose how to achieve a molecularlike interaction potential in laboratory 2D complex plasmas. We argue that this principal aim can be achieved by using relatively small microparticles and properly adjusting discharge parameters. If experimentally confirmed, this will make it possible to employ complex plasmas as a model system with an interaction potential resembling that of conventional liquids.

  20. Periodically sheared 2D Yukawa systems

    SciTech Connect

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

    2015-10-15

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

  1. ENERGY LANDSCAPE OF 2D FLUID FORMS

    SciTech Connect

    Y. JIANG; ET AL

    2000-04-01

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

  2. A scalable 2-D parallel sparse solver

    SciTech Connect

    Kothari, S.C.; Mitra, S.

    1995-12-01

    Scalability beyond a small number of processors, typically 32 or less, is known to be a problem for existing parallel general sparse (PGS) direct solvers. This paper presents a parallel general sparse PGS direct solver for general sparse linear systems on distributed memory machines. The algorithm is based on the well-known sequential sparse algorithm Y12M. To achieve efficient parallelization, a 2-D scattered decomposition of the sparse matrix is used. The proposed algorithm is more scalable than existing parallel sparse direct solvers. Its scalability is evaluated on a 256 processor nCUBE2s machine using Boeing/Harwell benchmark matrices.

  3. 2D stepping drive for hyperspectral systems

    NASA Astrophysics Data System (ADS)

    Endrödy, Csaba; Mehner, Hannes; Grewe, Adrian; Sinzinger, Stefan; Hoffmann, Martin

    2015-07-01

    We present the design, fabrication and characterization of a compact 2D stepping microdrive for pinhole array positioning. The miniaturized solution enables a highly integrated compact hyperspectral imaging system. Based on the geometry of the pinhole array, an inch-worm drive with electrostatic actuators was designed resulting in a compact (1 cm2) positioning system featuring a step size of about 15 µm in a 170 µm displacement range. The high payload (20 mg) as required for the pinhole array and the compact system design exceed the known electrostatic inch-worm-based microdrives.

  4. Marginal fluctuations as instantons on M2/D2-branes

    NASA Astrophysics Data System (ADS)

    Naghdi, M.

    2014-03-01

    We introduce some (anti-) M/D-branes through turning on the corresponding field strengths of the 11- and 10-dimensional supergravity theories over spaces, where we use and for the internal spaces. Indeed, when we add M2/D2-branes on the same directions with the near horizon branes of the Aharony-Bergman-Jafferis-Maldacena model, all symmetries and supersymmetries are preserved trivially. In this case, we obtain a localized object just in the horizon. This normalizable bulk massless scalar mode is a singlet of and , and it agrees with a marginal boundary operator of the conformal dimension of . However, after performing a special conformal transformation, we see that the solution is localized in the Euclideanized space and is attributable to the included anti-M2/D2-branes, which are also necessary to ensure that there is no back-reaction. The resultant theory now breaks all supersymmetries to , while the other symmetries are so preserved. The dual boundary operator is then set up from the skew-whiffing of the representations and for the supercharges and scalars, respectively, while the fermions remain fixed in of the original theory. Besides, we also address another alternate bulk to boundary matching procedure through turning on one of the gauge fields of the full gauge group along the same lines with a similar situation to the one faced in the AdS/CFT correspondence. The latter approach covers the difficulty already faced with in the bulk-boundary matching procedure for as well.

  5. A full 2D IDCT with extreme low complexity

    NASA Astrophysics Data System (ADS)

    Navarro, Antonio; Silva, Antonio; Reznik, Yuriy

    2007-09-01

    In the context of a Call for Proposal for integer IDCTs issued by MPEG in July 2005, a full 2D integer IDCT based on a previous Feig and Winograd's work has been proposed. It achieves a high precision by meeting all IEEE1180 conditions and is suitable of implementation on hardware since it can be performed only with shifts and additions. Furthermore, it can be useful in high video resolution scenarios like in 720p/1080i/p due to its feedforward operation mode without any loop as usual in row-column implementations. The proposed transformation can be implemented without changing other functional blocks either at the encoder or at the decoder or alternatively as a scaled version incorporating the scaling factors into the dequantization stage. Our algorithm uses only 1328 operations for 8x8 blocks, including scaling factors.

  6. 2-D soft x-ray arrays in the EAST.

    PubMed

    Chen, Kaiyun; Xu, Liqing; Hu, Liqun; Duan, Yanmin; Li, Xueqin; Yuan, Yi; Mao, Songtao; Sheng, Xiuli; Zhao, Jinlong

    2016-06-01

    A high spatial and temporal resolution soft x-ray (SXR) imaging diagnostic has been installed in EAST for the study of magnetohydrodynamics activities and core high-Z impurity transport. Up to 122 lines of sight view the poloidal plasma from three directions (two up-down symmetrical horizontal arrays and one vertical array), which renders the diagnostic able to provide detailed tomographic reconstructions under various conditions. Fourier-Bessel method based on flux coordinates was employed for 2-D SXR tomographic reconstruction. Examples of several events measured by SXR diagnostic in EAST are shown, namely the crash patterns of sawtooth, periodical burst of edge localized modes, and the transport of high-Z intrinsic impurities. PMID:27370451

  7. 2-D soft x-ray arrays in the EAST

    NASA Astrophysics Data System (ADS)

    Chen, Kaiyun; Xu, Liqing; Hu, Liqun; Duan, Yanmin; Li, Xueqin; Yuan, Yi; Mao, Songtao; Sheng, Xiuli; Zhao, Jinlong

    2016-06-01

    A high spatial and temporal resolution soft x-ray (SXR) imaging diagnostic has been installed in EAST for the study of magnetohydrodynamics activities and core high-Z impurity transport. Up to 122 lines of sight view the poloidal plasma from three directions (two up-down symmetrical horizontal arrays and one vertical array), which renders the diagnostic able to provide detailed tomographic reconstructions under various conditions. Fourier-Bessel method based on flux coordinates was employed for 2-D SXR tomographic reconstruction. Examples of several events measured by SXR diagnostic in EAST are shown, namely the crash patterns of sawtooth, periodical burst of edge localized modes, and the transport of high-Z intrinsic impurities.

  8. Microwave Assisted 2D Materials Exfoliation

    NASA Astrophysics Data System (ADS)

    Wang, Yanbin

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

  9. Photocurrent spectroscopy of 2D materials

    NASA Astrophysics Data System (ADS)

    Cobden, David

    Confocal photocurrent measurements provide a powerful means of studying many aspects of the optoelectronic and electrical properties of a 2D device or material. At a diffraction-limited point they can provide a detailed absorption spectrum, and they can probe local symmetry, ultrafast relaxation rates and processes, electron-electron interaction strengths, and transport coefficients. We illustrate this with several examples, once being the photo-Nernst effect. In gapless 2D materials, such as graphene, in a perpendicular magnetic field a photocurrent antisymmetric in the field is generated near to the free edges, with opposite sign at opposite edges. Its origin is the transverse thermoelectric current associated with the laser-induced electron temperature gradient. This effect provides an unambiguous demonstration of the Shockley-Ramo nature of long-range photocurrent generation in gapless materials. It also provides a means of investigating quasiparticle properties. For example, in the case of graphene on hBN, it can be used to probe the Lifshitz transition that occurs due to the minibands formed by the Moire superlattice. We also observe and discuss photocurrent generated in other semimetallic (WTe2) and semiconducting (WSe2) monolayers. Work supported by DoE BES and NSF EFRI grants.

  10. Multienzyme Inkjet Printed 2D Arrays.

    PubMed

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

    2015-08-19

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

  11. Quantitative analysis of tissue deformation dynamics reveals three characteristic growth modes and globally aligned anisotropic tissue deformation during chick limb development

    PubMed Central

    Morishita, Yoshihiro; Kuroiwa, Atsushi; Suzuki, Takayuki

    2015-01-01

    Tissue-level characterization of deformation dynamics is crucial for understanding organ morphogenetic mechanisms, especially the interhierarchical links among molecular activities, cellular behaviors and tissue/organ morphogenetic processes. Limb development is a well-studied topic in vertebrate organogenesis. Nevertheless, there is still little understanding of tissue-level deformation relative to molecular and cellular dynamics. This is mainly because live recording of detailed cell behaviors in whole tissues is technically difficult. To overcome this limitation, by applying a recently developed Bayesian approach, we here constructed tissue deformation maps for chick limb development with high precision, based on snapshot lineage tracing using dye injection. The precision of the constructed maps was validated with a clear statistical criterion. From the geometrical analysis of the map, we identified three characteristic tissue growth modes in the limb and showed that they are consistent with local growth factor activity and cell cycle length. In particular, we report that SHH signaling activity changes dynamically with developmental stage and strongly correlates with the dynamic shift in the tissue growth mode. We also found anisotropic tissue deformation along the proximal-distal axis. Morphogenetic simulation and experimental studies suggested that this directional tissue elongation, and not local growth, has the greatest impact on limb shaping. This result was supported by the novel finding that anisotropic tissue elongation along the proximal-distal axis occurs independently of cell proliferation. Our study marks a pivotal point for multi-scale system understanding in vertebrate development. PMID:25858459

  12. Similarities between 2D and 3D convection for large Prandtl number

    NASA Astrophysics Data System (ADS)

    Pandey, Ambrish; Verma, Mahendra K.; Chatterjee, Anando G.; Dutta, Biplab

    2016-06-01

    Using direct numerical simulations of Rayleigh-B\\'{e}nard convection (RBC), we perform a comparative study of the spectra and fluxes of energy and entropy, and the scaling of large-scale quantities for large and infinite Prandtl numbers in two (2D) and three (3D) dimensions. We observe close similarities between the 2D and 3D RBC, in particular the kinetic energy spectrum $E_u(k) \\sim k^{-13/3}$, and the entropy spectrum exhibits a dual branch with a dominant $k^{-2}$ spectrum. We showed that the dominant Fourier modes in the 2D and 3D flows are very close. Consequently, the 3D RBC is quasi two-dimensional, which is the reason for the similarities between the 2D and 3D RBC for large- and infinite Prandtl numbers.

  13. Utilizing Lifetimes to Suppress Random Coil Features in 2D IR Spectra of Peptides

    PubMed Central

    Middleton, Chris T.; Buchanan, Lauren E.; Dunkelberger, Emily B.

    2011-01-01

    We report that the waiting time delay in 2D IR pulse sequences can be used to suppress signals from structurally disordered regions of amyloid fibrils. At a waiting time delay of 1.0 ps, the random coil vibrational modes of amylin fibrils are no longer detectable, leaving only the sharp excitonic vibrational features of the fibril β-sheets. Isotope labeling with 13C18O reveals that structurally disordered residues decay faster than residues protected from solvent. Since structural disorder is usually accompanied by hydration, we conclude that the shorter lifetimes of random-coil residues is due to solvent exposure. These results indicate that 2D IR pulse sequences can utilize the waiting time to better resolve solvent-protected regions of peptides and that local mode lifetimes should be included in simulations of 2D IR spectra. PMID:21966585

  14. 2-D or not 2-D, that is the question: A Northern California test

    SciTech Connect

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

    2005-06-06

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

  15. High-resolution simulations and modeling of reshocked single-mode Richtmyer-Meshkov instability. I. Comparison to experimental data and to amplitude growth model predictions

    SciTech Connect

    Latini, M; Schilling, O; Don, W

    2006-05-15

    The reshocked single-mode Richtmyer-Meshkov instability is simulated in two spatial dimensions using the fifth- and ninth-order weighted essentially non-oscillatory shock-capturing method with uniform spatial resolution of 256 points per initial perturbation wavelength. The initial conditions and computational domain are modeled after the single-mode, Mach 1.21 air(acetone)/SF{sub 6} shock tube experiment of Collins and Jacobs [J. Fluid Mech. 464, 113 (2002)]. The simulation densities are shown to be in very good agreement with the corrected experimental planar laser-induced fluorescence images at selected times before reshock of the evolving interface. Analytical, semianalytical and phenomenological linear and nonlinear, impulsive, perturbation and potential flow models for single-mode Richtmyer-Meshkov unstable perturbation growth are summarized. The simulation amplitudes are shown to be in very good agreement with the experimental data and with the predictions of linear amplitude growth models for small times and with those of nonlinear amplitude growth models at later times up to the time at which the driver-based expansion in the experiment (but not present in the simulations or models) expands the layer before reshock. The qualitative and quantitative differences between the fifth- and ninth-order simulation results are discussed. Using a local and global quantitative metric, the prediction of the Zhang and Sohn [Phys. Fluids 9, 1106 (1997)] nonlinear Pade model is shown to be in best overall agreement with the simulation amplitudes before reshock. The sensitivity of the amplitude growth model predictions to the initial growth rate from linear instability theory, the post-shock Atwood number and amplitude, and the velocity jump due to the passage of the shock through the interface is also investigated numerically. In Part II [Phys. Fluids (2006)], a comprehensive investigation of mixing induced by the reshocked single-mode Richtmyer-Meshkov instability is

  16. Rapid loss of the plasma sheet energetic electrons associated with the growth of whistler mode waves inside the bursty bulk flows

    NASA Astrophysics Data System (ADS)

    Li, L. Y.; Yu, J.; Cao, J. B.

    During the interval 07:45:36- 07:54:24 UT on 24 August 2005, Cluster satellites (C1 and C3) observed an obvious loss of energetic electrons (3.2- 95keV) associated with the growth of whistler mode waves inside some bursty bulk flows (BBFs) in the midtail plasma sheet (X _{GSM}= -17.25 R _{E}). However, the fluxes of the higher-energy electrons (>128keV) and energetic ions (10- 160 keV) were relatively stable in the BBF-impacted regions. The energy-dependent electron loss inside the BBFs is mainly due to the energy-selective pitch angle scatterings by whistler mode waves within the time scales from several seconds to several minutes, and the electron scatterings in different pitch angle distributions are different in the wave growth regions. The plasma sheet energetic electrons have mainly a quasi-perpendicular pitch angle distribution (30(°) growth regions inside the BBFs. Unlike the energetic electrons, the low-energy electrons (0.073- 2.1keV) have initially a field-aligned pitch angle distribution (0(°) mode waves, and their loss in field-aligned directions is accompanied by their increase in quasi-perpendicular directions in the wave growth regions, but the loss of the low-energy electrons inside the BBFs is not obvious in the presence of their large background fluxes. These observations indicate that the resonant electrons in an anisotropic pitch angle distribution mainly undergo the rapid pitch angle scattering loss during the wave-particle resonances.

  17. Overexpression of the Tomato Pollen Receptor Kinase LePRK1 Rewires Pollen Tube Growth to a Blebbing Mode[W][OPEN

    PubMed Central

    Gui, Cai-Ping; Dong, Xin; Liu, Hai-Kuan; Huang, Wei-Jie; Zhang, Dong; Wang, Shu-Jie; Barberini, María Laura; Gao, Xiao-Yan; Muschietti, Jorge; McCormick, Sheila

    2014-01-01

    The tubular growth of a pollen tube cell is crucial for the sexual reproduction of flowering plants. LePRK1 is a pollen-specific and plasma membrane–localized receptor-like kinase from tomato (Solanum lycopersicum). LePRK1 interacts with another receptor, LePRK2, and with KINASE PARTNER PROTEIN (KPP), a Rop guanine nucleotide exchange factor. Here, we show that pollen tubes overexpressing LePRK1 or a truncated LePRK1 lacking its extracellular domain (LePRK1ΔECD) have enlarged tips but also extend their leading edges by producing “blebs.” Coexpression of LePRK1 and tomato PLIM2a, an actin bundling protein that interacts with KPP in a Ca2+-responsive manner, suppressed these LePRK1 overexpression phenotypes, whereas pollen tubes coexpressing KPP, LePRK1, and PLIM2a resumed the blebbing growth mode. We conclude that overexpression of LePRK1 or LePRK1ΔECD rewires pollen tube growth to a blebbing mode, through KPP- and PLIM2a-mediated bundling of actin filaments from tip plasma membranes. Arabidopsis thaliana pollen tubes expressing LePRK1ΔECD also grew by blebbing. Our results exposed a hidden capability of the pollen tube cell: upon overexpression of a single membrane-localized molecule, LePRK1 or LePRK1ΔECD, it can switch to an alternative mechanism for extension of the leading edge that is analogous to the blebbing growth mode reported for Dictyostelium and for Drosophila melanogaster stem cells. PMID:25194029

  18. Squeezing in a 2-D generalized oscillator

    NASA Technical Reports Server (NTRS)

    Castanos, Octavio; Lopez-Pena, Ramon; Manko, Vladimir I.

    1994-01-01

    A two-dimensional generalized oscillator with time-dependent parameters is considered to study the two-mode squeezing phenomena. Specific choices of the parameters are used to determine the dispersion matrix and analytic expressions, in terms of standard hermite polynomials, of the wavefunctions and photon distributions.

  19. Numerical Evaluation of 2D Ground States

    NASA Astrophysics Data System (ADS)

    Kolkovska, Natalia

    2016-02-01

    A ground state is defined as the positive radial solution of the multidimensional nonlinear problem \\varepsilon propto k_ bot 1 - ξ with the function f being either f(u) =a|u|p-1u or f(u) =a|u|pu+b|u|2pu. The numerical evaluation of ground states is based on the shooting method applied to an equivalent dynamical system. A combination of fourth order Runge-Kutta method and Hermite extrapolation formula is applied to solving the resulting initial value problem. The efficiency of this procedure is demonstrated in the 1D case, where the maximal difference between the exact and numerical solution is ≈ 10-11 for a discretization step 0:00025. As a major application, we evaluate numerically the critical energy constant. This constant is defined as a functional of the ground state and is used in the study of the 2D Boussinesq equations.

  20. Canard configured aircraft with 2-D nozzle

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  1. Graphene suspensions for 2D printing

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  2. The mouse ruby-eye 2(d) (ru2(d) /Hps5(ru2-d) ) allele inhibits eumelanin but not pheomelanin synthesis.

    PubMed

    Hirobe, Tomohisa; Ito, Shosuke; Wakamatsu, Kazumasa

    2013-09-01

    The novel mutation named ru2(d) /Hps5(ru2-d) , characterized by light-colored coats and ruby-eyes, prohibits differentiation of melanocytes by inhibiting tyrosinase (Tyr) activity, expression of Tyr, Tyr-related protein 1 (Tyrp1), Tyrp2, and Kit. However, it is not known whether the ru2(d) allele affects pheomelanin synthesis in recessive yellow (e/Mc1r(e) ) or in pheomelanic stage in agouti (A) mice. In this study, effects of the ru2(d) allele on pheomelanin synthesis were investigated by chemical analysis of melanin present in dorsal hairs of 5-week-old mice from F2 generation between C57BL/10JHir (B10)-co-isogenic ruby-eye 2(d) and B10-congenic recessive yellow or agouti. Eumelanin content was decreased in ruby-eye 2(d) and ruby-eye 2(d) agouti mice, whereas pheomelanin content in ruby-eye 2(d) recessive yellow and ruby-eye 2(d) agouti mice did not differ from the corresponding Ru2(d) /- mice, suggesting that the ru2(d) allele inhibits eumelanin but not pheomelanin synthesis. PMID:23672590

  3. Immunological Visibility: Posttranscriptional Regulation of Human NKG2D Ligands by the EGF Receptor Pathway

    PubMed Central

    Vantourout, Pierre; Willcox, Carrie; Turner, Andrea; Swanson, Chad; Haque, Yasmin; Sobolev, Olga; Grigoriadis, Anita; Tutt, Andrew; Hayday, Adrian

    2014-01-01

    Human cytolytic T lymphocytes and NK cells can limit tumor growth and are being increasingly harnessed for tumor immunotherapy. One way cytolytic lymphocytes recognize tumor cells is by engagement of their activating receptor, NKG2D, by stress-antigens of the MICA/B and ULBP families. This study shows that surface upregulation of NKG2D ligands by human epithelial cells in response to ultraviolet irradiation, osmotic shock, oxidative stress, and growth factor provision, is attributable to activation of the EGF-receptor (EGFR). EGFR activation causes intracellular re-localisation of AUF1 proteins that ordinarily destabilise NKG2D ligand mRNAs by targeting an AU-rich element conserved within the 3′ ends of most human but not murine NKG2D ligand genes. Consistent with these findings, NKG2D ligand expression by primary human carcinomas positively correlated with EGFR expression that is commonly hyper-activated in such tumours, and was reduced by clinical EGFR inhibitors. Thus, stress-induced activation of EGFR not only regulates cell growth but concomitantly regulates the cells’ immunological visibility. Thus, therapeutics designed to limit cancer cell growth should also be considered in terms of their impact on immunosurveillance. PMID:24718859

  4. Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy

    PubMed Central

    Xiong, Wei; Laaser, Jennifer E.; Mehlenbacher, Randy D.; Zanni, Martin T.

    2011-01-01

    In the last ten years, two-dimensional infrared spectroscopy has become an important technique for studying molecular structures and dynamics. We report the implementation of heterodyne detected two-dimensional sum-frequency generation (HD 2D SFG) spectroscopy, which is the analog of 2D infrared (2D IR) spectroscopy, but is selective to noncentrosymmetric systems such as interfaces. We implement the technique using mid-IR pulse shaping, which enables rapid scanning, phase cycling, and automatic phasing. Absorptive spectra are obtained, that have the highest frequency resolution possible, from which we extract the rephasing and nonrephasing signals that are sometimes preferred. Using this technique, we measure the vibrational mode of CO adsorbed on a polycrystalline Pt surface. The 2D spectrum reveals a significant inhomogenous contribution to the spectral line shape, which is quantified by simulations. This observation indicates that the surface conformation and environment of CO molecules is more complicated than the simple “atop” configuration assumed in previous work. Our method can be straightforwardly incorporated into many existing SFG spectrometers. The technique enables one to quantify inhomogeneity, vibrational couplings, spectral diffusion, chemical exchange, and many other properties analogous to 2D IR spectroscopy, but specifically for interfaces. PMID:22143772

  5. 2D to 3D transition of polymeric carbon nitride nanosheets

    SciTech Connect

    Chamorro-Posada, Pedro; Vázquez-Cabo, José; Martín-Ramos, Pablo; Martín-Gil, Jesús; Navas-Gracia, Luis M.; Dante, Roberto C.

    2014-11-15

    The transition from a prevalent turbostratic arrangement with low planar interactions (2D) to an array of polymeric carbon nitride nanosheets with stronger interplanar interactions (3D), occurring for samples treated above 650 °C, was detected by terahertz-time domain spectroscopy (THz-TDS). The simulated 3D material made of stacks of shifted quasi planar sheets composed of zigzagged polymer ribbons, delivered a XRD simulated pattern in relatively good agreement with the experimental one. The 2D to 3D transition was also supported by the simulation of THz-TDS spectra obtained from quantum chemistry calculations, in which the same broad bands around 2 THz and 1.5 THz were found for 2D and 3D arrays, respectively. This transition was also in accordance with the tightening of the interplanar distance probably due to an interplanar π bond contribution, as evidenced also by a broad absorption around 2.6 eV in the UV–vis spectrum, which appeared in the sample treated at 650 °C, and increased in the sample treated at 700 °C. The band gap was calculated for 1D and 2D cases. The value of 3.374 eV for the 2D case is, within the model accuracy and precision, in a relative good agreement with the value of 3.055 eV obtained from the experimental results. - Graphical abstract: 2D lattice mode vibrations and structural changes correlated with the so called “2D to 3D transition”. - Highlights: • A 2D to 3D transition has been detected for polymeric carbon nitride. • THz-TDS allowed us to discover and detect the 2D to 3D transition of polymeric carbon nitride. • We propose a structure for polymeric carbon nitride confirming it with THz-TDS.

  6. Ratios between acute aquatic toxicity and effects on population growth rates in relation to toxicant mode of action

    SciTech Connect

    Roex, E.W.M.; Gestel, C.A.M. Van; Wezel, A.P. Van; Straalen, N.M. Van

    2000-03-01

    Environmental risk assessment of chemicals is mostly based on the results of standardized toxicity tests. To obtain environmental quality criteria, extrapolation factors are used that depend on the amount and quality of available data. These extrapolation factors do not, however, take into account the mode of action of the compound tested or the life history of the test organism. In this study, the authors analyzed the variability in acute-to-chronic ratios (ACRs) for various chemicals in relation to their mode of action. Chemicals were classified as nonpolar narcotics, polar narcotics, specifically acting compounds, and heavy metals. As an acute endpoint, the LC50 was used; as a chronic endpoint, the lowest test concentration at which the natural rate of population increase (r) is affected, or LOEC(r), was used. Data were derived from the on-line literature. Nonpolar narcotic chemicals demonstrate the smallest variation in ACRs, and acute tests can be used to derive chronic endpoints for this class. For the other classes, the variation in ACRs is larger. Fish species especially show a relatively large ACR. For heavy metals, differences in the mode of action may play an important role in explaining differences in ACRs. For the other three classes, however, it is less reliable to predict chronic toxicity using the results of acute tests. In general, differences in species sensitivity rather than in mode of action for the chemical seem to determine differences in ACRs.

  7. Multistep mineral fouling growth on a cation-exchange membrane ruled by gradual sieving effects of magnesium and carbonate ions and its delay by pulsed modes of electrodialysis.

    PubMed

    Cifuentes-Araya, Nicolás; Pourcelly, Gérald; Bazinet, Laurent

    2012-04-15

    The aim of this study was to reveal the mechanisms ruling a fouling growth on both sides of a CMX-SB cation-exchange membrane (CEM), run after run during three consecutive electrodialysis (ED) treatments. A model solution containing a high magnesium/calcium ratio (2/5) was demineralized under two different pulsed electric field (PEF) on-duty ratios and dc current. The results showed a series of mechanisms ruling a multilayer mineral fouling growth and its delay by PEFs. The nature of the fouling layer, during a first run, depended on the diluate pH-value evolutions and the ion migration rates through the membrane. A subsequent multilayer fouling growth during consecutive treatments was ruled by the already formed mineral layers, where gradual sieving effects inverted the migration rates and led to a multistep crystal growth. Calcium carbonate grew on the diluate side of CEM, starting from its amorphous phase to then crystallize in a coexisting presence of aragonite and calcite. Amorphous magnesium hydroxide appeared on CEM apparently through fouling dehydration ruled by the mineral layers themselves and by overlimiting current regimes. A delayed fouling growth was observed for PEF ratio 0.3. A long pause lapse during pulse modes was demonstrated as an important parameter for fouling mitigation. PMID:22326231

  8. A new inversion method for (T2, D) 2D NMR logging and fluid typing

    NASA Astrophysics Data System (ADS)

    Tan, Maojin; Zou, Youlong; Zhou, Cancan

    2013-02-01

    One-dimensional nuclear magnetic resonance (1D NMR) logging technology has some significant limitations in fluid typing. However, not only can two-dimensional nuclear magnetic resonance (2D NMR) provide some accurate porosity parameters, but it can also identify fluids more accurately than 1D NMR. In this paper, based on the relaxation mechanism of (T2, D) 2D NMR in a gradient magnetic field, a hybrid inversion method that combines least-squares-based QR decomposition (LSQR) and truncated singular value decomposition (TSVD) is examined in the 2D NMR inversion of various fluid models. The forward modeling and inversion tests are performed in detail with different acquisition parameters, such as magnetic field gradients (G) and echo spacing (TE) groups. The simulated results are discussed and described in detail, the influence of the above-mentioned observation parameters on the inversion accuracy is investigated and analyzed, and the observation parameters in multi-TE activation are optimized. Furthermore, the hybrid inversion can be applied to quantitatively determine the fluid saturation. To study the effects of noise level on the hybrid method and inversion results, the numerical simulation experiments are performed using different signal-to-noise-ratios (SNRs), and the effect of different SNRs on fluid typing using three fluid models are discussed and analyzed in detail.

  9. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires.

    PubMed

    Gamalski, A D; Tersoff, J; Stach, E A

    2016-04-13

    We study the growth of GaN nanowires from liquid Au-Ga catalysts using environmental transmission electron microscopy. GaN wires grow in either ⟨112̅0⟩ or ⟨11̅00⟩ directions, by the addition of {11̅00} double bilayers via step flow with multiple steps. Step-train growth is not typically seen with liquid catalysts, and we suggest that it results from low step mobility related to the unusual double-height step structure. The results here illustrate the surprising dynamics of catalytic GaN wire growth at the nanoscale and highlight striking differences between the growth of GaN and other III-V semiconductor nanowires. PMID:26990711

  10. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires

    DOE PAGESBeta

    Gamalski, A. D.; Tersoff, J.; Stach, E. A.

    2016-04-13

    We study the growth of GaN nanowires from liquid Au–Ga catalysts using environmental transmission electron microscopy. GaN wires grow in either (11¯20) or (11¯00) directions, by the addition of {11¯00} double bilayers via step flow with multiple steps. Step-train growth is not typically seen with liquid catalysts, and we suggest that it results from low step mobility related to the unusual double-height step structure. Finally, the results here illustrate the surprising dynamics of catalytic GaN wire growth at the nanoscale and highlight striking differences between the growth of GaN and other III–V semiconductor nanowires.

  11. Simulation of coupled bunch mode growth driven by a high-Q resonator: A transient response approach

    SciTech Connect

    Stahl, S.; Bogacz, S.A.

    1989-03-01

    In this article the use of a longitudinal phase-space tracking code, ESME, to simulate the growth of a coupled-bunch instability in the Fermilab Booster is examined. A description of the calculation of the resonant response is given, and results are presented for the growth of the coupled bunch instability in a ring in which all of the rf buckets are equally populated and in one in which several consecutive buckets are empty. 4 refs., 6 figs.

  12. Reconstructing skeletal fiber arrangement and growth mode in the coral Porites lutea (Cnidaria, Scleractinia): a confocal Raman microscopy study

    NASA Astrophysics Data System (ADS)

    Wall, M.; Nehrke, G.

    2012-11-01

    Confocal Raman microscopy (CRM) mapping was used to investigate the microstructural arrangement and organic matrix distribution within the skeleton of the coral Porites lutea. Relative changes in the crystallographic orientation of crystals within the fibrous fan-system could be mapped, without the need to prepare thin sections, as required if this information is obtained by polarized light microscopy. Simultaneously, incremental growth lines can be visualized without the necessity of etching and hence alteration of sample surface. Using these methods two types of growth lines could be identified: one corresponds to the well-known incremental growth layers, whereas the second type of growth lines resemble denticle finger-like structures (most likely traces of former spines or skeletal surfaces). We hypothesize that these lines represent the outer skeletal surface before another growth cycle of elongation, infilling and thickening of skeletal areas continues. We show that CRM mapping with high spatial resolution can significantly improve our understanding of the micro-structural arrangement and growth patterns in coral skeletons.

  13. α-amylase crystal growth investigated by in situ atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Astier, J. P.; Bokern, D.; Lapena, L.; Veesler, S.

    2001-06-01

    The growth behavior of porcine pancreatic α-amylase at defined supersaturation has been investigated by means of temperature controlled in situ atomic force microscopy (AFM). The step velocities measured by AFM were in overall agreement with the normal growth rates of an individual face measured by optical microscopy. In addition, highly local growth dynamics could be visualized. Imaging in tapping mode revealed crystalline amylase aggregates attached to the basal face and their subsequent incorporation into growing terraces producing a macrodefect. At high supersaturation ( β=1.6) 2-D nucleation was found to be the dominating growth mechanism, whereas at lower supersaturation ( β=1.3) the growth process appears to be defect controlled (spiral growth). The analysis of step heights on 2-D nucleation islands (monomolecular protein layers) and growth steps (two molecules in height) in combination with results from light scattering experiments suggest that a single protein molecule is the basic growth unit.

  14. Radiofrequency Spectroscopy and Thermodynamics of Fermi Gases in the 2D to Quasi-2D Dimensional Crossover

    NASA Astrophysics Data System (ADS)

    Cheng, Chingyun; Kangara, Jayampathi; Arakelyan, Ilya; Thomas, John

    2016-05-01

    We tune the dimensionality of a strongly interacting degenerate 6 Li Fermi gas from 2D to quasi-2D, by adjusting the radial confinement of pancake-shaped clouds to control the radial chemical potential. In the 2D regime with weak radial confinement, the measured pair binding energies are in agreement with 2D-BCS mean field theory, which predicts dimer pairing energies in the many-body regime. In the qausi-2D regime obtained with increased radial confinement, the measured pairing energy deviates significantly from 2D-BCS theory. In contrast to the pairing energy, the measured radii of the cloud profiles are not fit by 2D-BCS theory in either the 2D or quasi-2D regimes, but are fit in both regimes by a beyond mean field polaron-model of the free energy. Supported by DOE, ARO, NSF, and AFOSR.

  15. Destabilization of 2D magnetic current sheets by resonance with bouncing electron - a new theory

    NASA Astrophysics Data System (ADS)

    Fruit, Gabriel; Louarn, Philippe; Tur, Anatoly

    2016-07-01

    In the general context of understanding the possible destabilization of the magnetotail before a substorm, we propose a kinetic model for electromagnetic instabilities in resonant interaction with trapped bouncing electrons. The geometry is clearly 2D and uses Harris sheet profile. Fruit et al. 2013 already used this model to investigate the possibilities of electrostatic instabilities. Tur et al. 2014 generalizes the model for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period (a few seconds). The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasi neutrality condition and the Ampere's law for the current density. The present talk will focus on the main results of this theory. The electrostatic version of the model may be applied to the near-Earth environment (8-12 R_{E}) where beta is rather low. It is showed that inclusion of bouncing electron motion may enhance strongly the growth rate of the classical drift wave instability. This model could thus explain the generation of strong parallel electric fields in the ionosphere and the formation of aurora beads with wavelength of a few hundreds of km. In the electromagnetic version, it is found that for mildly stretched current sheet (B_{z} > 0.1 B _{lobes}) undamped modes oscillate at typical electron bounce frequency with wavelength of the order of the plasma sheet thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in B_{z}/B _{lobes}, the mode becomes explosive (pure imaginary frequency) with typical growing rate of a few

  16. Competing coexisting phases in 2D water

    PubMed Central

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-01-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules. PMID:27185018

  17. 2D Radiative Processes Near Cloud Edges

    NASA Technical Reports Server (NTRS)

    Varnai, T.

    2012-01-01

    Because of the importance and complexity of dynamical, microphysical, and radiative processes taking place near cloud edges, the transition zone between clouds and cloud free air has been the subject of intense research both in the ASR program and in the wider community. One challenge in this research is that the one-dimensional (1D) radiative models widely used in both remote sensing and dynamical simulations become less accurate near cloud edges: The large horizontal gradients in particle concentrations imply that accurate radiative calculations need to consider multi-dimensional radiative interactions among areas that have widely different optical properties. This study examines the way the importance of multidimensional shortwave radiative interactions changes as we approach cloud edges. For this, the study relies on radiative simulations performed for a multiyear dataset of clouds observed over the NSA, SGP, and TWP sites. This dataset is based on Microbase cloud profiles as well as wind measurements and ARM cloud classification products. The study analyzes the way the difference between 1D and 2D simulation results increases near cloud edges. It considers both monochromatic radiances and broadband radiative heating, and it also examines the influence of factors such as cloud type and height, and solar elevation. The results provide insights into the workings of radiative processes and may help better interpret radiance measurements and better estimate the radiative impacts of this critical region.

  18. Simulation of Yeast Cooperation in 2D.

    PubMed

    Wang, M; Huang, Y; Wu, Z

    2016-03-01

    Evolution of cooperation has been an active research area in evolutionary biology in decades. An important type of cooperation is developed from group selection, when individuals form spatial groups to prevent them from foreign invasions. In this paper, we study the evolution of cooperation in a mixed population of cooperating and cheating yeast strains in 2D with the interactions among the yeast cells restricted to their small neighborhoods. We conduct a computer simulation based on a game theoretic model and show that cooperation is increased when the interactions are spatially restricted, whether the game is of a prisoner's dilemma, snow drifting, or mutual benefit type. We study the evolution of homogeneous groups of cooperators or cheaters and describe the conditions for them to sustain or expand in an opponent population. We show that under certain spatial restrictions, cooperator groups are able to sustain and expand as group sizes become large, while cheater groups fail to expand and keep them from collapse. PMID:26988702

  19. Ion Transport in 2-D Graphene Nanochannels

    NASA Astrophysics Data System (ADS)

    Xie, Quan; Foo, Elbert; Duan, Chuanhua

    2015-11-01

    Graphene membranes have recently attracted wide attention due to its great potential in water desalination and selective molecular sieving. Further developments of these membranes, including enhancing their mass transport rate and/or molecular selectivity, rely on the understanding of fundamental transport mechanisms through graphene membranes, which has not been studied experimentally before due to fabrication and measurement difficulties. Herein we report the fabrication of the basic constituent of graphene membranes, i.e. 2-D single graphene nanochannels (GNCs) and the study of ion transport in these channels. A modified bonding technique was developed to form GNCs with well-defined geometry and uniform channel height. Ion transport in such GNCs was studied using DC conductance measurement. Our preliminary results showed that the ion transport in GNCs is still governed by surface charge at low concentrations (10-6M to 10-4M). However, GNCs exhibits much higher ionic conductances than silica nanochannels with the same geometries in the surface-charge-governed regime. This conductance enhancement can be attributed to the pre-accumulation of charges on graphene surfaces. The work is supported by the Faculty Startup Fund (Boston University, USA).

  20. Parallel map analysis on 2-D grids

    SciTech Connect

    Berry, M.; Comiskey, J.; Minser, K.

    1993-12-31

    In landscape ecology, computer modeling is used to assess habitat fragmentation and its ecological iMPLications. Specifically, maps (2-D grids) of habitat clusters must be analyzed to determine number, sizes and geometry of clusters. Models prior to this study relied upon sequential Fortran-77 programs which limited the sizes of maps and densities of clusters which could be analyzed. In this paper, we present more efficient computer models which can exploit recursion or parallelism. Significant improvements over the original Fortran-77 programs have been achieved using both recursive and nonrecursive C implementations on a variety of workstations such as the Sun Sparc 2, IBM RS/6000-350, and HP 9000-750. Parallel implementations on a 4096-processor MasPar MP-1 and a 32-processor CM-5 are also studied. Preliminary experiments suggest that speed improvements for the parallel model on the MasPar MP-1 (written in MPL) and on the CM-5 (written in C using CMMD) can be as much as 39 and 34 times faster, respectively, than the most efficient sequential C program on a Sun Sparc 2 for a 512 map. An important goal in this research effort is to produce a scalable map analysis algorithm for the identification and characterization of clusters for relatively large maps on massively-parallel computers.

  1. 2D Turbulence with Complicated Boundaries

    NASA Astrophysics Data System (ADS)

    Roullet, G.; McWilliams, J. C.

    2014-12-01

    We examine the consequences of lateral viscous boundary layers on the 2D turbulence that arises in domains with complicated boundaries (headlands, bays etc). The study is carried out numerically with LES. The numerics are carefully designed to ensure all global conservation laws, proper boundary conditions and a minimal range of dissipation scales. The turbulence dramatically differs from the classical bi-periodic case. Boundary layer separations lead to creation of many small vortices and act as a continuing energy source exciting the inverse cascade of energy throughout the domain. The detachments are very intermittent in time. In free decay, the final state depends on the effective numerical resolution: laminar with a single dominant vortex for low Re and turbulent with many vortices for large enough Re. After very long time, the turbulent end-state exhibits a striking tendency for the emergence of shielded vortices which then interact almost elastically. In the forced case, the boundary layers allow the turbulence to reach a statistical steady state without any artificial hypo-viscosity or other large-scale dissipation. Implications are discussed for the oceanic mesoscale and submesoscale turbulence.

  2. Competing coexisting phases in 2D water

    NASA Astrophysics Data System (ADS)

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-05-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules.

  3. Competing coexisting phases in 2D water.

    PubMed

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-01-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules. PMID:27185018

  4. 2-D wavelet with position controlled resolution

    NASA Astrophysics Data System (ADS)

    Walczak, Andrzej; Puzio, Leszek

    2005-09-01

    Wavelet transformation localizes all irregularities in the scene. It is most effective in the case when intensities in the scene have no sharp details. It is the case often present in a medical imaging. To identify the shape one has to extract it from the scene as typical irregularity. When the scene does not contain sharp changes then common differential filters are not efficient tool for a shape extraction. The new 2-D wavelet for such task has been proposed. Described wavelet transform is axially symmetric and has varied scale in dependence on the distance from the centre of the wavelet symmetry. The analytical form of the wavelet has been presented as well as its application for details extraction in the scene. Most important feature of the wavelet transform is that it gives a multi-scale transformation, and if zoom is on the wavelet selectivity varies proportionally to the zoom step. As a result, the extracted shape does not change during zoom operation. What is more the wavelet selectivity can be fit to the local intensity gradient properly to obtain best extraction of the irregularities.

  5. Latent heat induced rotation limited aggregation in 2D ice nanocrystals

    NASA Astrophysics Data System (ADS)

    Bampoulis, Pantelis; Siekman, Martin H.; Kooij, E. Stefan; Lohse, Detlef; Zandvliet, Harold J. W.; Poelsema, Bene

    2015-07-01

    The basic science responsible for the fascinating shapes of ice crystals and snowflakes is still not understood. Insufficient knowledge of the interaction potentials and the lack of relevant experimental access to the growth process are to blame for this failure. Here, we study the growth of fractal nanostructures in a two-dimensional (2D) system, intercalated between mica and graphene. Based on our scanning tunneling spectroscopy data, we provide compelling evidence that these fractals are 2D ice. They grow while they are in material contact with the atmosphere at 20 °C and without significant thermal contact to the ambient. The growth is studied in situ, in real time and space at the nanoscale. We find that the growing 2D ice nanocrystals assume a fractal shape, which is conventionally attributed to Diffusion Limited Aggregation (DLA). However, DLA requires a low mass density mother phase, in contrast to the actual currently present high mass density mother phase. Latent heat effects and consequent transport of heat and molecules are found to be key ingredients for understanding the evolution of the snow (ice) flakes. We conclude that not the local availability of water molecules (DLA), but rather them having the locally required orientation is the key factor for incorporation into the 2D ice nanocrystal. In combination with the transport of latent heat, we attribute the evolution of fractal 2D ice nanocrystals to local temperature dependent rotation limited aggregation. The ice growth occurs under extreme supersaturation, i.e., the conditions closely resemble the natural ones for the growth of complex 2D snow (ice) flakes and we consider our findings crucial for solving the "perennial" snow (ice) flake enigma.

  6. Latent heat induced rotation limited aggregation in 2D ice nanocrystals.

    PubMed

    Bampoulis, Pantelis; Siekman, Martin H; Kooij, E Stefan; Lohse, Detlef; Zandvliet, Harold J W; Poelsema, Bene

    2015-07-21

    The basic science responsible for the fascinating shapes of ice crystals and snowflakes is still not understood. Insufficient knowledge of the interaction potentials and the lack of relevant experimental access to the growth process are to blame for this failure. Here, we study the growth of fractal nanostructures in a two-dimensional (2D) system, intercalated between mica and graphene. Based on our scanning tunneling spectroscopy data, we provide compelling evidence that these fractals are 2D ice. They grow while they are in material contact with the atmosphere at 20 °C and without significant thermal contact to the ambient. The growth is studied in situ, in real time and space at the nanoscale. We find that the growing 2D ice nanocrystals assume a fractal shape, which is conventionally attributed to Diffusion Limited Aggregation (DLA). However, DLA requires a low mass density mother phase, in contrast to the actual currently present high mass density mother phase. Latent heat effects and consequent transport of heat and molecules are found to be key ingredients for understanding the evolution of the snow (ice) flakes. We conclude that not the local availability of water molecules (DLA), but rather them having the locally required orientation is the key factor for incorporation into the 2D ice nanocrystal. In combination with the transport of latent heat, we attribute the evolution of fractal 2D ice nanocrystals to local temperature dependent rotation limited aggregation. The ice growth occurs under extreme supersaturation, i.e., the conditions closely resemble the natural ones for the growth of complex 2D snow (ice) flakes and we consider our findings crucial for solving the "perennial" snow (ice) flake enigma. PMID:26203037

  7. E-2D Advanced Hawkeye: primary flight display

    NASA Astrophysics Data System (ADS)

    Paolillo, Paul W.; Saxena, Ragini; Garruba, Jonathan; Tripathi, Sanjay; Blanchard, Randy

    2006-05-01

    This paper is a response to the challenge of providing a large area avionics display for the E-2D AHE aircraft. The resulting display design provides a pilot with high-resolution visual information content covering an image area of almost three square feet (Active Area of Samsung display = 33.792cm x 27.0336 cm = 13.304" x 10.643" = 141.596 square inches = 0.983 sq. ft x 3 = 2.95 sq. ft). The avionics display application, design and performance being described is the Primary Flight Display for the E-2D Advanced Hawkeye aircraft. This cockpit display has a screen diagonal size of 17 inches. Three displays, with minimum bezel width, just fit within the available instrument panel area. The significant design constraints of supporting an upgrade installation have been addressed. These constraints include a display image size that is larger than the mounting opening in the instrument panel. This, therefore, requires that the Electromagnetic Interference (EMI) window, LCD panel and backlight all fit within the limited available bezel depth. High brightness and a wide dimming range are supported with a dual mode Cold Cathode Fluorescent Tube (CCFT) and LED backlight. Packaging constraints dictated the use of multiple U shaped fluorescent lamps in a direct view backlight design for a maximum display brightness of 300 foot-Lamberts. The low intensity backlight levels are provided by remote LEDs coupled through a fiber optic mesh. This architecture generates luminous uniformity within a minimum backlight depth. Cross-cockpit viewing is supported with ultra-wide field-of-view performance including contrast and the color stability of an advanced LCD cell design supports. Display system design tradeoffs directed a priority to high optical efficiency for minimum power and weight.

  8. [Effects of different fertilization modes on vegetable growth, fertilizer nitrogen utilization, and nitrogen loss from vegetable field].

    PubMed

    Huang, Dong-feng; Wang, Guo; Li, Wei-hua; Qiu, Xiao-xuan

    2009-03-01

    A field experiment with Chinese cabbage, water spinach, and three-colored amaranth cropped three times in one year was conducted to study the effects of seven fertilization modes, i.e., none fertilization, basal application of chemical fertilizers, 1/2 basal application and 1/2 top-dressing of chemical fertilizers, basal application of chemical fertilizers and dicyandiamide, 1/2 basal application and 1/2 top-dressing of chemical fertilizers and dicyandiamide, 1/2 basal application and 1/2 top-dressing of chemical fertilizers and organic manure, and basal application of organic manure, on the plant height, yield, nitrogen accumulation, and fertilizer nitrogen utilization of the vegetables, and the loss of NO3- -N and NH4+ -N from vegetable field under natural rainfall condition. The results showed that comparing with none fertilization, the fertilization modes '1/2 basal application and 1/2 top-dressing of chemical fertilizers and organic manure' and 'basal application of chemical fertilizers and dicyandiamide' improved the agronomic properties of test vegetables, increased their yields by 103%-219% and 93%-226%, and nitrogen accumulation by 153% -216% and 231%-320%, respectively, and enhanced fertilizer nitrogen utilization rate. They also decreased the surface runoff loss of NO3- -N and NH4+ -N by 48.1% and 46.5%, respectively, compared with the mode 'basal application of chemical fertilizers', and hence, reduced the risk of agricultural non-point pollution. Therefore, these two fertilization modes could be popularized in vegetable production. PMID:19637603

  9. Novel piezoelectric actuation mechanism for a gimbal-less mirror in 2D raster scanning applications

    NASA Astrophysics Data System (ADS)

    How Koh, Kah; Kobayashi, Takeshi; Xie, Jin; Yu, Aibin; Lee, Chengkuo

    2011-07-01

    In this paper, we present the design, fabrication and measurement results of a 2D scanning mirror actuated by 1 × 10 piezoelectric Pb(Zr,Ti)O3 (PZT) cantilever actuators integrated on a thin silicon beam. A combination of bulk silicon micromachining based on a silicon-on-insulator (SOI) substrate and thin-film surface micromachining on a 5 µm thick Si device layer is used to fabricate the device. Multi-layers of Pt/Ti/PZT/Pt/Ti are deposited as electrode materials. A large silicon mirror plate (5 mm × 5 mm) and a 1 × 10 PZT cantilever array arranged in parallel are formed after the backside release process. The ten PZT cantilever actuators are electrically isolated from one another. The device can operate in three modes: bending, torsional and mixed (or combinational) modes. In bending mode, the first resonant frequency was measured to be 30 Hz and an optical deflection angle of ±8° was obtained when all ten cantilevers were actuated at 9 Vpp. In torsional mode, the resonant frequency was measured to be 89 Hz and an optical deflection angle of ±4.6° was obtained by applying a gradually declining ac voltage started at 8 Vpp to two sets of actuators, where each set comprises five cantilever actuators of the said 1 × 10 array, i.e. 1-5 and 6-10. A 2D raster scanning pattern was achieved in the mixed mode when the bending mode was carried out by cantilever actuators of 4-7 and the torsional modes were exercised by two different sets of cantilever actuators, i.e. 1-3 and 8-10, under opposite biasing direction. This mixed mode operation mechanism demonstrates the first 2D raster scanning mirror-driven beam actuators.

  10. In situ doping of catalyst-free InAs nanowires with Si: Growth, polytypism, and local vibrational modes of Si

    SciTech Connect

    Dimakis, Emmanouil; Ramsteiner, Manfred; Huang, Chang-Ning; Trampert, Achim; Riechert, Henning; Geelhaar, Lutz; Davydok, Anton; Biermanns, Andreas; Pietsch, Ullrich

    2013-09-30

    Growth and structural aspects of the in situ doping of InAs nanowires with Si have been investigated. The nanowires were grown catalyst-free on Si(111) substrates by molecular beam epitaxy. The supply of Si influenced the growth kinetics, affecting the nanowire dimensions, but not the degree of structural polytypism, which was always pronounced. As determined by Raman spectroscopy, Si was incorporated as substitutional impurity exclusively on In sites, which makes it a donor. Previously unknown Si-related Raman peaks at 355 and 360 cm{sup −1} were identified, based on their symmetry properties in polarization-dependent measurements, as the two local vibrational modes of an isolated Si impurity on In site along and perpendicular, respectively, to the c-axis of the wurtzite InAs crystal.

  11. A comparison of the growth modes of (100)- and (110)-oriented CrO2 films through the calculation of surface and interface energies

    NASA Astrophysics Data System (ADS)

    Chetry, K. B.; Sims, H.; Butler, W. H.; Gupta, A.

    2011-12-01

    The mechanism leading to different growth modes of (100)- and (110)-oriented CrO2 films on a TiO2 substrate has been investigated by using first-principles calculations based on density functional theory (DFT). The surface energies of (100)- and (110)-oriented CrO2 and TiO2 structures were calculated within a three-dimensional slab model. The convergence of the surface energy was studied with respect to the interslab vacuum distance and the thickness of the slab. A sandwich geometry was used to study the interface energy between CrO2 and TiO2. These results shed light on published experimental results on the growth of epitaxially grown CrO2 on (100)- and (110)-oriented TiO2 substrates.

  12. Room temperature weak ferromagnetism in Sn1-xMnxSe2 2D films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Dong, Sining; Liu, Xinyu; Li, Xiang; Kanzyuba, Vasily; Yoo, Taehee; Rouvimov, Sergei; Vishwanath, Suresh; Xing, Huili G.; Jena, Debdeep; Dobrowolska, Margaret; Furdyna, Jacek K.

    2016-03-01

    We discuss growth and magnetic properties of high-quality two dimensional (2D) Sn1-xMnxSe2 films. Thin films of this 2D ternary alloy with a wide range of Mn concentrations were successfully grown by molecular beam epitaxy. Mn concentrations up to x ≈ 0.60 were achieved without destroying the crystal structure of the parent SnSe2 2D system. Most important, the specimens show clear weak ferromagnetic behavior above room temperature, which should be of interest for 2D spintronic applications.

  13. Infrared intensities and optical constants of crystalline C 2H 4 and C 2D 4

    NASA Astrophysics Data System (ADS)

    Zhao, G.; Ospina, M. J.; Khanna, R. K.

    Infrared absorption spectra of several thin films of C 2H 4 and C 2D 4 at ˜55 K were investigated at ˜0.6 cm -1 resolution. The integrated band intensities of the infrared active fundamental modes were obtained by a linear fit of the integrated absorbances vs film thickness. An iterative Kramers—Kronig analysis of the absorption data was carried out to obtain the complex refractive indices of crystalline C 2H 4 and C 2D 4 in the regions of absorption bands.

  14. 2-D Animation's Not Just for Mickey Mouse.

    ERIC Educational Resources Information Center

    Weinman, Lynda

    1995-01-01

    Discusses characteristics of two-dimensional (2-D) animation; highlights include character animation, painting issues, and motion graphics. Sidebars present Silicon Graphics animations tools and 2-D animation programs for the desktop computer. (DGM)

  15. Potentiostatic controlled nucleation and growth modes of electrodeposited cobalt thin films on n-Si(1 1 1)

    NASA Astrophysics Data System (ADS)

    Mechehoud, Fayçal; Khelil, Abdelbacet; Eddine Hakiki, Nour; Bubendorff, Jean-Luc

    2016-08-01

    The nucleation and growth of Co electrodeposits on n-Si(1 1 1) substrate have been investigated as a function of the applied potential in a large potential range using electrochemical techniques (voltammetry and chrono-amperometry) and surface imaging by atomic force microscopy (AFM). The surface preparation of the sample is crucial and we achieve a controlled n-Si(1 1 1) surface with mono-atomic steps and flat terraces. Using Scharifker-Hills models for fitting the current-time transients, we show that a transition from an instantaneous nucleation process to a progressive one occurs when the overpotential increases. A good agreement between the nucleation and growth parameters extracted from the models and the AFM data's is observed. The growth is of the Volmer-Weber type with a roughness and a spatial extension in the substrate plane of the deposited islands that increase with thickness.

  16. Haloxyfop mode of action in liquid cultures of proso millet: An analysis of haloxyfop sensitivity changes during growth

    SciTech Connect

    Irzyk, G.P.

    1989-01-01

    Haloxyfop is a grass-selective herbicide that inhibits acetyl-CoA carboxylase in species that are not tolerant to the herbicide. Liquid cultures of proso millet (Panicum miliaceum) cells treated with haloxyfop at different phases of growth exhibited different levels of sensitivity to the herbicide. Treatment of 1-d cultures with 1 {mu}M haloxyfop completely inhibited growth within 48 h. In contrast, 1 mM haloxyfop was required to elicit a similar response in 4-, 7-, or 10-d cultures. Calculated IC{sub 50} values indicated a 300-fold decrease in haloxyfop sensitivity during the period from 1 to 4 d. This period of growth coincided with the greatest increase in cell number during culture growth and suggested that dividing cells are most sensitive to haloxyfop. Uptake and metabolism of {sup 14}C-haloxyfop in 1-d and 4-d cultures were compared. In both cultures, amounts of radiolabel uptake were similar. Almost all radioactivity extracted from 1- and 4-d cells was present as the parent compound. These results suggested that the sensitivity change was related to other factors. Acetyl-CoA carboxylase activity of proso millet cells, measured in vitro by the acetyl-CoA-dependent incorporation of {sup 14} C-bicarbonate into an acid-stable product, was essentially constant during culture growth. Micromolar concentrations of haloxyfop significantly inhibited acetyl-CoA carboxylase activity from both sensitive and insensitive cultures. Thus, the change in the sensitivity of cultures to haloxyfop was not correlated with changes in acetyl-CoA carboxylase abundance, activity, or sensitivity to haloxyfop during culture growth. In vivo incorporation of {sup 14}C-acetate into lipids was decreased by 1 {mu}M haloxyfop in both 1-d and 4-d cultures at the earliest sampling times but the amount of inhibition was significantly greater in the sensitive cultures.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  20. Cooperative dynamics in ultrasoft 2D crystals

    NASA Astrophysics Data System (ADS)

    Sprakel, Joris; van der Meer, Berend; Dijkstra, Marjolein; van der Gucht, Jasper

    2015-03-01

    The creation, annihilation, and diffusion of defects in crystal lattices play an important role during crystal melting and deformation. Although it is well understood how defects form and react when crystals are subjected to external stresses, it remains unclear how crystals cope with internal stresses. We report a study in which we create a highly localized internal stress, by means of optical tweezing, in a crystal formed from micrometer-sized colloidal spheres and directly observe how the solid reacts using microscopy. We find that, even though the excitation is highly localized, a collective dance of colloidal particles results; these collective modes take the form of closed rings or open-ended strings, depending on the sequence of events which nucleate the rearrangements. Surprisingly, we find from Brownian Dynamics simulations that these cooperative dynamics are thermally-activated modes inherent to the crystal, and can even occur through a single, sufficiently large thermal fluctuation, resulting in the irreversible displacement of 100s of particles from their lattice sites.

  1. MAZE96. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Sanford, L.; Hallquist, J.O.

    1992-02-24

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  2. On 2D graphical representation of DNA sequence of nondegeneracy

    NASA Astrophysics Data System (ADS)

    Zhang, Yusen; Liao, Bo; Ding, Kequan

    2005-08-01

    Some two-dimensional (2D) graphical representations of DNA sequences have been given by Gates, Nandy, Leong and Mogenthaler, Randić, and Liao et al., which give visual characterizations of DNA sequences. In this Letter, we introduce a nondegeneracy 2D graphical representation of DNA sequence, which is different from Randić's novel 2D representation and Liao's 2D representation. We also present the nondegeneracy forms corresponding to the representations of Gates, Nandy, Leong and Mogenthaler.

  3. Generates 2D Input for DYNA NIKE & TOPAZ

    1996-07-15

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  4. 2d PDE Linear Symmetric Matrix Solver

    1983-10-01

    ICCG2 (Incomplete Cholesky factorized Conjugate Gradient algorithm for 2d symmetric problems) was developed to solve a linear symmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as resistive MHD, spatial diffusive transport, and phase space transport (Fokker-Planck equation) problems. These problems share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized withmore » finite-difference or finite-element methods,the resulting matrix system is frequently of block-tridiagonal form. To use ICCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. The incomplete Cholesky conjugate gradient algorithm is used to solve the linear symmetric matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For matrices lacking symmetry, ILUCG2 should be used. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  5. 2d PDE Linear Asymmetric Matrix Solver

    1983-10-01

    ILUCG2 (Incomplete LU factorized Conjugate Gradient algorithm for 2d problems) was developed to solve a linear asymmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as plasma diffusion, equilibria, and phase space transport (Fokker-Planck equation) problems. These equations share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized with finite-difference or finite-elementmore » methods, the resulting matrix system is frequently of block-tridiagonal form. To use ILUCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. A generalization of the incomplete Cholesky conjugate gradient algorithm is used to solve the matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For problems having a symmetric matrix ICCG2 should be used since it runs up to four times faster and uses approximately 30% less storage. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source, containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  6. Silicene, a promising new 2D material

    NASA Astrophysics Data System (ADS)

    Oughaddou, Hamid; Enriquez, Hanna; Tchalala, Mohammed Rachid; Yildirim, Handan; Mayne, Andrew J.; Bendounan, Azzedine; Dujardin, Gérald; Ait Ali, Mustapha; Kara, Abdelkader

    2015-02-01

    Silicene is emerging as a two-dimensional material with very attractive electronic properties for a wide range of applications; it is a particularly promising material for nano-electronics in silicon-based technology. Over the last decade, the existence and stability of silicene has been the subject of much debate. Theoretical studies were the first to predict a puckered honeycomb structure with electronic properties resembling those of graphene. Though these studies were for free-standing silicene, experimental fabrication of silicene has been achieved so far only through epitaxial growth on crystalline surfaces. Indeed, it was only in 2010 that researchers presented the first experimental evidence of the formation of silicene on Ag(1 1 0) and Ag(1 1 1), which has launched silicene in a similar way to graphene. This very active field has naturally led to the recent growth of silicene on Ir(1 1 1), ZrB2(0 0 0 1) and Au(1 1 0) substrates. However, the electronic properties of epitaxially grown silicene on metal surfaces are influenced by the strong silicene-metal interactions. This has prompted experimental studies of the growth of multi-layer silicene, though the nature of its "silicene" structure remains questionable. Of course, like graphene, synthesizing free-standing silicene represents the ultimate challenge. A first step towards this has been reported recently through chemical exfoliation from calcium disilicide (CaSi2). In this review, we discuss the experimental and theoretical studies of silicene performed to date. Special attention is given to different experimental studies of the electronic properties of silicene on metal substrates. New avenues for the growth of silicene on other substrates with different chemical characteristics are presented along with foreseeable applications such as nano-devices and novel batteries.

  7. Overexpression of the tomato pollen receptor kinase LePRK1 rewires pollen tube growth to a blebbling mode

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The tubular growth of a pollen tube cell is crucial for the sexual reproduction of flowering plants. LePRK1 is a pollen-specific and plasma membrane–localized receptor-like kinase from tomato (Solanum lycopersicum). LePRK1 interacts with another receptor, LePRK2, and with KINASE PARTNER PROTEIN (KPP...

  8. A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures

    SciTech Connect

    Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1998-12-14

    We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.

  9. Integrated mode converter for mode division multiplexing

    NASA Astrophysics Data System (ADS)

    Perez-Galacho, Diego; Alonso-Ramos, Carlos Alberto; Marris-Morini, Delphine; Vakarin, Vladyslav; Le Roux, Xavier; Ortega-Moñux, Alejandro; Wangüemert-Perez, Juan Gonzalo; Vivien, Laurent

    2016-05-01

    The ever growing demands of bandwidth in optical communication systems are making traditional Wavelength Division Multiplexing (WDM) based systems to reach its limit. In order to cope with future bandwidth demand is necessary to use new levels of orthogonality, such as the waveguide mode or the polarization state. Mode Division Multiplexing (MDM) has recently attracted attention as a possible solution to increase aggregate bandwidth. In this work we discuss the proposition a of mode converter that can cover the whole C-Band of optical communications. The Mode Converter is based on two Multimode Interference (MMI) couplers and a phase shifter. Insertion loss (IL) below 0.2 dB and Extinction ratio (ER) higher than 20 dB in a broad bandwidth range of 1.5 μm to 1.6 μm have been estimated. The total length of the device is less than 30 μm.

  10. Neoproterozoic to Paleozoic Geological Evolution of Mongolia: Constraints on Modes of "Crustal Growth" in the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Macdonald, F. A.; Bold, U.; Smith, E.; Olin, P. H.; Crowley, J. L.; Schmitz, M. D.

    2012-12-01

    The Central Asian Orogenic Belt (CAOB) is widely considered the largest area of Phanerozoic juvenile crustal growth on Earth. However, the timing and nature of the orogenic events in the core of the CAOB in Mongolia has remained poorly constrained due to a dearth of detailed geological and geochronological studies. To bridge this gap and test models of crustal growth, here we refine the sequencing of geological events by focusing on the formation and destruction of Neoproterozoic and Paleozoic tectonic basins. Mongolia's basins record a complete Neoproterozoic to Cambrian Wilson cycle with rifting of the Mongolian continent at ca. 700 Ma, the development of a Cryogenian to Ediacaran thermally subsiding passive margin, an arc-continent collision at ca. 520 Ma, and a continent-arc-continent collision at ca. 500 Ma. During this collisional orogeny, that is the Cambrian Altaids, crustal growth occurred largely through the obduction of ophiolites. Rifting of the southern margin occurred during the Ordovician Period, with the development of a Silurian passive margin. Oblique northwest-dipping subduction was initiated during the Devonian and resulted in a transpressional accretionary orogen. The CAOB culminated with a continent-arc-continent collision and the accretion of the North China and Tarim Blocks in the latest Permian. The Devonian to early Permian accretionary orogen is associated not only with voluminous plutonism, but also, major translational structures oblique to the margin resulting in the appearance of many accreted terranes. These data are consistent with existing coarse Hf and Nd isotopic data, but also provide a framework for future detailed studies. Although our geological constraints suggest distinct periods of apparent crustal growth through either collisional or accretionary orogenies, net crustal growth after accounting for recycling is equivocal.

  11. Insight into the crystallization of amorphous imine-linked polymer networks to 2D covalent organic frameworks.

    PubMed

    Smith, Brian J; Overholts, Anna C; Hwang, Nicky; Dichtel, William R

    2016-03-01

    We explore the crystallization of a high surface area imine-linked two-dimensional covalent organic framework (2D COF). The growth process reveals rapid initial formation of an amorphous network that subsequently crystallizes into the layered 2D network. The metastable amorphous polymer may be isolated and resubjected to growth conditions to form the COF. These experiments provide the first mechanistic insight into the mechanism of imine-linked 2D COF formation, which is distinct from that of boronate-ester linked COFs. PMID:26857035

  12. Step-flow growth mode instability of N-polar GaN under N-excess

    SciTech Connect

    Chèze, C.

    2013-08-12

    GaN layers were grown on N-polar GaN substrates by plasma-assisted molecular beam epitaxy under different III/V ratios. Ga-rich conditions assure step-flow growth with atomically flat surface covered by doubly-bunched steps, as for Ga-polar GaN. Growth under N-excess however leads to an unstable step-flow morphology. Particularly, for substrates slightly miscut towards <1010>, interlacing fingers are covered by atomic steps pinned on both sides by small hexagonal pits. In contrast, a three-dimensional island morphology is observed on the Ga-polar equivalent sample. We attribute this result to lower diffusion barriers on N-polar compared to Ga-polar GaN under N-rich conditions.

  13. Effects of proof loads and combined mode loadings on fracture and flaw growth characteristics of aerospace alloys

    NASA Technical Reports Server (NTRS)

    Shah, R. C.

    1974-01-01

    This experimental program was undertaken to determine the effects of (1) combined tensile and bending loadings, (2) combined tensile and shear loadings, and (3) proof overloads on fracture and flaw growth characteristics of aerospace alloys. Tests were performed on four alloys: 2219-T87 aluminum, 5Al-2.5Sn (ELl) titanium, 6Al-4V beta STA titanium and high strength 4340 steel. Tests were conducted in room air, gaseous nitrogen at -200F (144K), liquid nitrogen and liquid hydrogen. Flat center cracked and surface flawed specimens, cracked tube specimens, circumferentially notched round bar and surface flawed cylindrical specimens were tested. The three-dimensional photoelastic technique of stress freezing and slicing was used to determine stress intensity factors for surface flawed cylindrical specimens subjected to tension or torsion. Results showed that proof load/temperature histories used in the tests have a small beneficial effect or no effect on subsequent fracture strength and flaw growth rates.

  14. Studies on the dynamics of vacuum encapsulated 2D MEMS scanners by laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Janes, Joachim; Hofmann, Ulrich

    2014-03-01

    2D MEMS scanners are used for e.g. Laser projection purposes or Lidar applications. Electrostatically driven resonant torsional oscillations of both axes of the scanners lead to Lissajous trajectories for Laser beams reflected from the micro mirror. Wafer level vacuum encapsulation with tilt glass capping ensures high angular amplitudes at low driving voltages additionally preventing environmental impacts. Applying Laser Doppler Vibrometry, the effect of residual gas friction, squeezed film damping and internal friction on 2D MEMS scanners is analyzed by measuring the Q-values associated with the torsional oscillations. Vibrometry is also used to analyze the oscillatory motion of the micro mirror and the gimbal of the scanners. Excited modes of the scanner structures are identified giving rise to coupling effects influencing the scanning performance of the 2D MEMS mirrors.

  15. A salt-bridge structure in solution revealed by 2D-IR spectroscopy.

    PubMed

    Huerta-Viga, Adriana; Domingos, Sérgio R; Amirjalayer, Saeed; Woutersen, Sander

    2014-08-14

    Salt bridges are important interactions for the stability of protein conformations, but up to now it has been difficult to determine salt-bridge geometries in solution. Here we characterize the spatial structure of a salt bridge between guanidinium (Gdm(+)) and acetate (Ac(-)) using two-dimensional vibrational (2D-IR) spectroscopy. We find that as a result of salt bridge formation there is a significant change in the infrared response of Gdm(+) and Ac(-), and cross peaks between them appear in the 2D-IR spectrum. From the 2D-IR spectrum we determine the relative orientation of the transition-dipole moments of the vibrational modes of Gdm(+) and Ac(-), as well as the coupling between them. PMID:24676430

  16. Modes of Action and Functions of ERECTA-family Receptor-like Kinases in Plant Organ Growth and Development

    SciTech Connect

    TORII, Keiko U.

    2012-05-01

    Higher plants constitute the central resource for renewable lignocellulose biomass that can supplement for the world's depleting stores of fossil fuels. As such, understanding the molecular and genetic mechanisms of plant organ growth will provide key knowledge and genetic resources that enables manipulation of plant biomass feedstock for better growth and productivity. The goal of this proposal is to understand how cell proliferation and growth are coordinated during aboveground organ morphogenesis, and how cell-cell signaling mediated by a family of receptor kinases coordinates plant organogenesis. The well-established model plant Arabidopsis thaliana is used for our research to facilitate rapid progress. Specifically, we focus on how ERECTA-family leucine-rich repeat receptor kinases (LRR-RLKs) interact in a synergistic manner to promote organogenesis and pattern formation in Arabidopsis. This project was highly successful, resulted in fourteen publications including nine peer-reviewed original research articles. One provisional US patent has been filed through this DOE funding. We have addressed the critical roles for a family of receptor kinases in coordinating proliferation and differentiation of plants, and we successfully elucidated the downstream targets of this signaling pathway in specifying stomatal patterning.

  17. Characterization and optimization of 2-step MOVPE growth for single-mode DFB or DBR laser diodes

    NASA Astrophysics Data System (ADS)

    Bugge, F.; Mogilatenko, A.; Zeimer, U.; Brox, O.; Neumann, W.; Erbert, G.; Weyers, M.

    2011-01-01

    We have studied the MOVPE regrowth of AlGaAs over a grating for GaAs-based laser diodes with an internal wavelength stabilisation. Growth temperature and aluminium concentration in the regrown layers considerably affect the oxygen incorporation. Structural characterisation by transmission electron microscopy of the grating after regrowth shows the formation of quaternary InGaAsP regions due to the diffusion of indium atoms from the top InGaP layer and As-P exchange processes during the heating-up procedure. Additionally, the growth over such gratings with different facets leads to self-organisation of the aluminium content in the regrown AlGaAs layer, resulting in an additional AlGaAs grating, which has to be taken into account for the estimation of the coupling coefficient. With optimized growth conditions complete distributed feedback laser structures have been grown for different emission wavelengths. At 1062 nm a very high single-frequency output power of nearly 400 mW with a slope efficiency of 0.95 W/A for a 4 μm ridge-waveguide was obtained.

  18. Evolution of Modes in Magnetically Insulated Crossed Field Diodes

    NASA Astrophysics Data System (ADS)

    Takeall, S.; Greenwood, A.; Cartwright, K.; Fleming, T.; Mardahl, P.; Lau, Y. Y.; Roderick, N.

    2006-10-01

    The time-dependent behavior of electron sheaths in a magnetically insulated B>BHull anode-cathode gap with crossed electric and magnetic fields is studied. The crossed-field, space-charge limited diode is modeled for various magnetic fields by means of multidimensional (1d and 2d), self consistent, electromagnetic, particle-in-cell (PIC) simulations in both cylindrical and planar geometries. The transient behavior of the system is examined in detail and is divided into three separate stages: cycloidal flow, collapse of cycloidal flow and sheared (near-Brillouin) flow. Our 2d electromagnetic PIC simulations (both planar and cylindrical) show that cycloidal flow also collapses into a perturbed flow that is dominated by the E cross B drift, but is neither steady nor stable. This observed cycloidal flow instability is a kinetic mode, not a fluid mode such as the magnetron or diocotron instability. The growth of the kinetic mode is faster than that of either of the above mentioned fluid instabilities. After the kinetic mode saturates, the fastest growing fluid mode grows to dominate the system. The SWS is added by three different methods to separate the RF effects from the DC electric field effects created by the SWS. The first method is to add a circuit to the anode that does not effect the DC electric fields, the second is to add the SWS by placing a thin dielectric (with and unphysical large dielectric constant), and last is to add the geometric SWS.

  19. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6*15 and *35 Genotyping

    PubMed Central

    Riffel, Amanda K.; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C.; Leeder, J. Steven; Rosenblatt, Kevin P.; Gaedigk, Andrea

    2016-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6*15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6*15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6*35) which is also located in exon 1. Although alternative CYP2D6*15 and *35 assays resolved the issue, we discovered a novel CYP2D6*15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6*15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6*43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer and/or probe regions can impact

  20. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6 (*) 15 and (*) 35 Genotyping.

    PubMed

    Riffel, Amanda K; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C; Leeder, J Steven; Rosenblatt, Kevin P; Gaedigk, Andrea

    2015-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6 (*) 15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6 (*) 15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6 (*) 35) which is also located in exon 1. Although alternative CYP2D6 (*) 15 and (*) 35 assays resolved the issue, we discovered a novel CYP2D6 (*) 15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6 (*) 15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6 (*) 43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer

  1. Glutamate dependent NMDA receptor 2D is a novel angiogenic tumour endothelial marker in colorectal cancer

    PubMed Central

    Ward, Stephen; Heath, Victoria L.; Ismail, Tariq; Bicknell, Roy

    2016-01-01

    Current vascular-targeted therapies in colorectal cancer (CRC) have shown limited benefit. The lack of novel, specific treatment in CRC has been hampered by a dearth of specific endothelial markers. Microarray comparison of endothelial gene expression in patient-matched CRC and normal colon identified a panel of putative colorectal tumour endothelial markers. Of these the glutamate dependent NMDA receptor GRIN2D emerged as the most interesting target. GRIN2D expression was shown to be specific to colorectal cancer vessels by RTqPCR and IHC analysis. Its expression was additionally shown be predictive of improved survival in CRC. Targeted knockdown studies in vitro demonstrated a role for GRIN2D in endothelial function and angiogenesis. This effect was also shown in vivo as vaccination against the extracellular region of GRIN2D resulted in reduced vascularisation in the subcutaneous sponge angiogenesis assay. The utility of immunologically targeting GRIN2D in CRC was demonstrated by the vaccination approach inhibiting murine CRC tumour growth and vascularisation. GRIN2D represents a promising target for the future treatment of CRC. PMID:26943033

  2. 2D modeling of electromagnetic waves in cold plasmas

    SciTech Connect

    Crombé, K.; Van Eester, D.; Koch, R.; Kyrytsya, V.

    2014-02-12

    The consequences of sheath (rectified) electric fields, resulting from the different mobility of electrons and ions as a response to radio frequency (RF) fields, are a concern for RF antenna design as it can cause damage to antenna parts, limiters and other in-vessel components. As a first step to a more complete description, the usual cold plasma dielectric description has been adopted, and the density profile was assumed to be known as input. Ultimately, the relevant equations describing the wave-particle interaction both on the fast and slow timescale will need to be tackled but prior to doing so was felt as a necessity to get a feeling of the wave dynamics involved. Maxwell's equations are solved for a cold plasma in a 2D antenna box with strongly varying density profiles crossing also lower hybrid and ion-ion hybrid resonance layers. Numerical modelling quickly becomes demanding on computer power, since a fine grid spacing is required to capture the small wavelengths effects of strongly evanescent modes.

  3. Topological Toughening of graphene and other 2D materials

    NASA Astrophysics Data System (ADS)

    Gao, Huajian

    It has been claimed that graphene, with the elastic modulus of 1TPa and theoretical strength as high as 130 GPa, is the strongest material. However, from an engineering point of view, it is the fracture toughness that determines the actual strength of materials, as crack-like flaws (i.e., cracks, holes, notches, corners, etc.) are inevitable in the design, fabrication, and operation of practical devices and systems. Recently, it has been demonstrated that graphene has very low fracture toughness, in fact close to that of ideally brittle solids. These findings have raised sharp questions and are calling for efforts to explore effective methods to toughen graphene. Recently, we have been exploring the potential use of topological effects to enhance the fracture toughness of graphene. For example, it has been shown that a sinusoidal graphene containing periodically distributed disclination quadrupoles can achieve a mode I fracture toughness nearly twice that of pristine graphene. Here we report working progresses on further studies of topological toughening of graphene and other 2D materials. A phase field crystal method is adopted to generate the atomic coordinates of material with specific topological patterns. We then perform molecular dynamics simulations of fracture in the designed samples, and observe a variety of toughening mechanisms, including crack tip blunting, crack trapping, ligament bridging, crack deflection and daughter crack initiation and coalescence.

  4. Simultaneous 2D Doppler backscattering from edge turbulence

    NASA Astrophysics Data System (ADS)

    Thomas, David; Brunner, Kai; Freethy, Simon; Huang, Billy; Shevchenko, Vladimir; Vann, Roddy

    2015-11-01

    The Synthetic Aperture Microwave Imaging (SAMI) diagnostic (previously at MAST and now at NSTX-U) actively probes the plasma edge using a wide (80 degree beam width) and broadband (10-34.5 GHz) beam. It digitizes the phase and amplitude of the Doppler backscattered signal using a receiving array of eight antennas which can be focused in any direction post shot to an angular range of 6-24 degree FWHM. This allows Doppler BackScattering (DBS) experiments to be conducted in every direction within the field of view simultaneously. This capability is unique to SAMI and is a novel way of conducting DBS experiments. SAMI has measured the magnetic pitch angle in the edge for the first time using a backscattering diagnostic. This is possible with simultaneous 2D DBS because the maximum backscattered power is perpendicular to the turbulence and turbulence is elongated along the magnetic field. SAMI has also studied the effect of NBI and the L-H transition on turbulent velocity, and turbulence suppression in the edge during H-mode. Initial results from all of these studies will be presented. This work is supported by the Engineering and Physical Sciences Research Council Grants EP/K504178 and EP/H016732.

  5. Experimental observation of Rayleigh-Taylor modes in solids with strength

    SciTech Connect

    Reinovsky, R.E.; Anderson, W.E.; Atchison, W.L.

    1998-12-31

    Magnetically imploded cylindrical metal shells (z-pinch liners) can be used to drive a wide variety of hydrodynamics and materials properties experiments if they can be imploded at high velocity with good azimuthal symmetry and axial uniformity. As in all z-pinches, the outer surface of the liner is magneto-Rayleigh-Taylor (RT) unstable during acceleration and large-scale distortion of the liners from RT modes growing from initial imperfections could make liners unusable. According to first principles, material strength in the liner should reduce the growth rate of RT modes and material strength can render some modes analytically stable. To study the evolution of RT modes in liners, a series of experiments have been conducted in which high purity aluminum liners were accelerated with 6 MA, 7ms risetime driving currents. Initial sub-millimeter perturbations were machined into the outer surface of the liner and perturbation growth monitored with x-ray imaging optical, magnetic and impact probes, described in a companion paper. Results 2D MHD simulations were in excellent agreement with observed perturbation growth through the entire course of the implosions. Analytic theory of instability threshold in materials with strength adequately predicted the onset of instability growth and is also in good agreement with 2D calculations. When internal stress substantially exceeded the yield strength of the material, fluid like growth rates were observed as predicted by analytic theory. In general, for high conductivity and soft materials, theory and simulation adequately predicted the behavior of classic magneto-RT modes. This is the first direct verification of the growth of magneto RT in solids with strength known to the authors. Based on these results higher strength liner materials should further reduce the growth of RT modes. Two similar experiments have also been conducted with substantially higher strength, but also lower conductivity, alloys in which dramatically

  6. The nonantibiotic anti-inflammatory effect of antimicrobial growth promoters, the real mode of action? A hypothesis.

    PubMed

    Niewold, T A

    2007-04-01

    Societal concern and government regulations increasingly press for restricting the use of antibiotics as antimicrobial growth promoters (AGP). The search for alternatives is on, hampered by a lack of knowledge about the exact mechanism of AGP. Feed additives, such as AGP and alternatives, interact with the intestine. In the intestine, feed components, microbiota, and the mucosa interact in a very complex and dynamic way. Various mechanisms for AGP have been proposed, invariably based on the direct antibiotic influence on the microbial composition of the intestines. In the literature on antibiotics, however, the direct effects of antibiotics on host cells, in particular inflammatory cells, have been described. It is curious that this has never been considered in the literature on AGP. Presently, a case is being made that AGP most likely work as growth permitters by inhibiting the production and excretion of catabolic mediators by intestinal inflammatory cells. Concomitant or subsequent changes in microflora are most likely the consequence of an altered condition of the intestinal wall. This common, basic mechanism potentially offers an excellent explanation for the highly reproducible effects of AGP, as opposed to those obtained by alternatives aimed at microflora management. Therefore, the search for alternatives could be aimed at nonantibiotic compounds with an effect on the inflammatory system similar to that of AGP. PMID:17369528

  7. Growth modes of InN (000-1) on GaN buffer layers on sapphire

    SciTech Connect

    Liu Bing; Kitajima, Takeshi; Chen Dongxue; Leone, Stephen R.

    2005-03-01

    In this work, using atomic force microscopy and scanning tunneling microscopy, we study the surface morphologies of epitaxial InN films grown by plasma-assisted molecular beam epitaxy with intervening GaN buffer layers on sapphire substrates. On smooth GaN buffer layers, nucleation and evolution of three-dimensional InN islands at various coverages and growth temperatures are investigated. The shapes of the InN islands are observed to be predominantly mesalike with large flat (000-1) tops, which suggests a possible role of indium as a surfactant. Rough GaN buffer layers composed of dense small GaN islands are found to significantly improve uniform InN wetting of the substrates, on which atomically smooth InN films are obtained that show the characteristics of step-flow growth. Scanning tunneling microscopy imaging reveals the defect-mediated surface morphology of smooth InN films, including surface terminations of screw dislocations and a high density of shallow surface pits with depths less than 0.3 nm. The mechanisms of the three-dimensional island size and shape evolution and formation of defects on smooth surfaces are considered.

  8. Growth modes of InN(000-1) on GaN buffer layers on sapphire

    SciTech Connect

    Liu, Bing; Kitajima, Takeshi; Chen, Dongxue; Leone, Stephen R.

    2005-01-24

    In this work, using atomic force microscopy and scanning tunneling microscopy, we study the surface morphologies of epitaxial InN films grown by plasma-assisted molecular beam epitaxy with intervening GaN buffer layers on sapphire substrates. On smooth GaN buffer layers, nucleation and evolution of three-dimensional InN islands at various coverages and growth temperatures are investigated. The shapes of the InN islands are observed to be predominantly mesa-like with large flat (000-1) tops, which suggests a possible role of indium as a surfactant. Rough GaN buffer layers composed of dense small GaN islands are found to significantly improve uniform InN wetting of the substrates, on which atomically smooth InN films are obtained that show the characteristics of step-flow growth. Scanning tunneling microscopy imaging reveals the defect-mediated surface morphology of smooth InN films, including surface terminations of screw dislocations and a high density of shallow surface pits with depths less than 0.3 nm. The mechanisms of the three-dimensional island size and shape evolution and formation of defects on smooth surfaces are considered.

  9. Differential CYP 2D6 Metabolism Alters Primaquine Pharmacokinetics

    PubMed Central

    Potter, Brittney M. J.; Xie, Lisa H.; Vuong, Chau; Zhang, Jing; Zhang, Ping; Duan, Dehui; Luong, Thu-Lan T.; Bandara Herath, H. M. T.; Dhammika Nanayakkara, N. P.; Tekwani, Babu L.; Walker, Larry A.; Nolan, Christina K.; Sciotti, Richard J.; Zottig, Victor E.; Smith, Philip L.; Paris, Robert M.; Read, Lisa T.; Li, Qigui; Pybus, Brandon S.; Sousa, Jason C.; Reichard, Gregory A.

    2015-01-01

    Primaquine (PQ) metabolism by the cytochrome P450 (CYP) 2D family of enzymes is required for antimalarial activity in both humans (2D6) and mice (2D). Human CYP 2D6 is highly polymorphic, and decreased CYP 2D6 enzyme activity has been linked to decreased PQ antimalarial activity. Despite the importance of CYP 2D metabolism in PQ efficacy, the exact role that these enzymes play in PQ metabolism and pharmacokinetics has not been extensively studied in vivo. In this study, a series of PQ pharmacokinetic experiments were conducted in mice with differential CYP 2D metabolism characteristics, including wild-type (WT), CYP 2D knockout (KO), and humanized CYP 2D6 (KO/knock-in [KO/KI]) mice. Plasma and liver pharmacokinetic profiles from a single PQ dose (20 mg/kg of body weight) differed significantly among the strains for PQ and carboxy-PQ. Additionally, due to the suspected role of phenolic metabolites in PQ efficacy, these were probed using reference standards. Levels of phenolic metabolites were highest in mice capable of metabolizing CYP 2D6 substrates (WT and KO/KI 2D6 mice). PQ phenolic metabolites were present in different quantities in the two strains, illustrating species-specific differences in PQ metabolism between the human and mouse enzymes. Taking the data together, this report furthers understanding of PQ pharmacokinetics in the context of differential CYP 2D metabolism and has important implications for PQ administration in humans with different levels of CYP 2D6 enzyme activity. PMID:25645856

  10. Designing of sparse 2D arrays for Lamb wave imaging using coarray concept

    NASA Astrophysics Data System (ADS)

    Ambroziński, Łukasz; Stepinski, Tadeusz; Uhl, Tadeusz

    2015-03-01

    2D ultrasonic arrays have considerable application potential in Lamb wave based SHM systems, since they enable equivocal damage imaging and even in some cases wave-mode selection. Recently, it has been shown that the 2D arrays can be used in SHM applications in a synthetic focusing (SF) mode, which is much more effective than the classical phase array mode commonly used in NDT. The SF mode assumes a single element excitation of subsequent transmitters and off-line processing the acquired data. In the simplest implementation of the technique, only single multiplexed input and output channels are required, which results in significant hardware simplification. Application of the SF mode for 2D arrays creates additional degrees of freedom during the design of the array topology, which complicates the array design process, however, it enables sparse array designs with performance similar to that of the fully populated dense arrays. In this paper we present the coarray concept to facilitate synthesis process of an array's aperture used in the multistatic synthetic focusing approach in Lamb waves-based imaging systems. In the coherent imaging, performed in the transmit/receive mode, the sum coarray is a morphological convolution of the transmit/receive sub-arrays. It can be calculated as the set of sums of the individual sub-arrays' elements locations. The coarray framework will be presented here using a an example of a star-shaped array. The approach will be discussed in terms of beampatterns of the resulting imaging systems. Both simulated and experimental results will be included.

  11. Designing of sparse 2D arrays for Lamb wave imaging using coarray concept

    SciTech Connect

    Ambroziński, Łukasz Stepinski, Tadeusz Uhl, Tadeusz

    2015-03-31

    2D ultrasonic arrays have considerable application potential in Lamb wave based SHM systems, since they enable equivocal damage imaging and even in some cases wave-mode selection. Recently, it has been shown that the 2D arrays can be used in SHM applications in a synthetic focusing (SF) mode, which is much more effective than the classical phase array mode commonly used in NDT. The SF mode assumes a single element excitation of subsequent transmitters and off-line processing the acquired data. In the simplest implementation of the technique, only single multiplexed input and output channels are required, which results in significant hardware simplification. Application of the SF mode for 2D arrays creates additional degrees of freedom during the design of the array topology, which complicates the array design process, however, it enables sparse array designs with performance similar to that of the fully populated dense arrays. In this paper we present the coarray concept to facilitate synthesis process of an array’s aperture used in the multistatic synthetic focusing approach in Lamb waves-based imaging systems. In the coherent imaging, performed in the transmit/receive mode, the sum coarray is a morphological convolution of the transmit/receive sub-arrays. It can be calculated as the set of sums of the individual sub-arrays’ elements locations. The coarray framework will be presented here using a an example of a star-shaped array. The approach will be discussed in terms of beampatterns of the resulting imaging systems. Both simulated and experimental results will be included.

  12. The infrared spectrum of the Ne-C2D2 complex.

    PubMed

    Moazzen-Ahmadi, N; McKellar, A R W; Fernández, Berta; Farrelly, David

    2015-11-28

    Infrared spectra of Ne-C2D2 are observed in the region of the ν3 fundamental band (asymmetric C-D stretch, ≈2440 cm(-1)) using a tunable optical parametric oscillator to probe a pulsed supersonic slit jet expansion from a cooled nozzle. Like helium-acetylene, this system lies close to the free rotor limit, making analysis tricky because stronger transitions tend to pile up close to monomer (C2D2) rotation-vibration transitions. Assignments are aided by predicted rotational energies calculated from a published ab initio intermolecular potential energy surface. The analysis extends up to the j = 3←2 band, where j labels C2D2 rotation within the dimer, and is much more complete than the limited infrared assignments previously reported for Ne-C2H2 and Ne-C2HD. Two previous microwave transitions within the j = 1 state of Ne-C2D2 are reassigned. Coriolis model fits to the theoretical levels and to the spectrum are compared. Since the variations observed as a function of C2D2 vibrational excitation are comparable to those noted between theory and experiment, it is evident that more detailed testing of theory will require vibrational averaging over the acetylene intramolecular modes. PMID:26627959

  13. The infrared spectrum of the Ne-C2D2 complex

    NASA Astrophysics Data System (ADS)

    Moazzen-Ahmadi, N.; McKellar, A. R. W.; Fernández, Berta; Farrelly, David

    2015-11-01

    Infrared spectra of Ne-C2D2 are observed in the region of the ν3 fundamental band (asymmetric C-D stretch, ≈2440 cm-1) using a tunable optical parametric oscillator to probe a pulsed supersonic slit jet expansion from a cooled nozzle. Like helium-acetylene, this system lies close to the free rotor limit, making analysis tricky because stronger transitions tend to pile up close to monomer (C2D2) rotation-vibration transitions. Assignments are aided by predicted rotational energies calculated from a published ab initio intermolecular potential energy surface. The analysis extends up to the j = 3←2 band, where j labels C2D2 rotation within the dimer, and is much more complete than the limited infrared assignments previously reported for Ne-C2H2 and Ne-C2HD. Two previous microwave transitions within the j = 1 state of Ne-C2D2 are reassigned. Coriolis model fits to the theoretical levels and to the spectrum are compared. Since the variations observed as a function of C2D2 vibrational excitation are comparable to those noted between theory and experiment, it is evident that more detailed testing of theory will require vibrational averaging over the acetylene intramolecular modes.

  14. 2D to 3D to 2D Dimensionality Crossovers in Thin BSCCO Films

    NASA Astrophysics Data System (ADS)

    Williams, Gary A.

    2003-03-01

    With increasing temperature the superfluid fraction in very thin BSCCO films undergoes a series of dimensionality crossovers. At low temperatures the strong anisotropy causes the thermal excitations to be 2D pancake-antipancake pairs in uncoupled layers. At higher temperatures where the c-axis correlation length becomes larger than a layer there is a crossover to 3D vortex loops. These are initially elliptical, but as the 3D Tc is approached they become more circular as the anisotropy scales away, as modeled by Shenoy and Chattopadhyay [1]. Close to Tc when the correlation length becomes comparable to the film thickness there is a further crossover to a 2D Kosterlitz-Thouless transition, with a drop of the superfluid fraction to zero at T_KT which can be of the order of 1 K below T_c. Good agreement with this model is found for experiments on thin BSCCO 2212 films [2]. 1. S. R. Shenoy and B. Chattopadhyay, Phys. Rev. B 51, 9129 (1995). 2. K. Osborn et al., cond-mat/0204417.

  15. Mechanical characterization of 2D, 2D stitched, and 3D braided/RTM materials

    NASA Technical Reports Server (NTRS)

    Deaton, Jerry W.; Kullerd, Susan M.; Portanova, Marc A.

    1993-01-01

    Braided composite materials have potential for application in aircraft structures. Fuselage frames, floor beams, wing spars, and stiffeners are examples where braided composites could find application if cost effective processing and damage tolerance requirements are met. Another important consideration for braided composites relates to their mechanical properties and how they compare to the properties of composites produced by other textile composite processes being proposed for these applications. Unfortunately, mechanical property data for braided composites do not appear extensively in the literature. Data are presented in this paper on the mechanical characterization of 2D triaxial braid, 2D triaxial braid plus stitching, and 3D (through-the-thickness) braid composite materials. The braided preforms all had the same graphite tow size and the same nominal braid architectures, (+/- 30 deg/0 deg), and were resin transfer molded (RTM) using the same mold for each of two different resin systems. Static data are presented for notched and unnotched tension, notched and unnotched compression, and compression after impact strengths at room temperature. In addition, some static results, after environmental conditioning, are included. Baseline tension and compression fatigue results are also presented, but only for the 3D braided composite material with one of the resin systems.

  16. 2D-ELDOR using full Sc- fitting and absorption lineshapes

    NASA Astrophysics Data System (ADS)

    Chiang, Yun-Wei; Costa-Filho, Antonio; Freed, Jack H.

    2007-10-01

    Recent progress in developing 2D-ELDOR (2D electron-electron double resonance) techniques to better capture molecular dynamics in complex fluids, particularly in model and biological membranes, is reported. The new "full Sc- method", which corrects the spectral analysis for the phase distortion effects present in the experiments, is demonstrated to enhance the sensitivity of 2D-ELDOR in reporting on molecular dynamics in complex membrane environments. That is, instead of performing spectral fitting in the magnitude mode, our new method enables simultaneous fitting of both the real and imaginary components of the Sc- signal. The full Sc- fitting not only corrects the phase distortions in the experimental data but also more accurately determines instrumental dead times. The phase corrections applied to the Sc- spectrum enable the extraction of the pure absorption-mode spectrum, which is characterized by much better resolution than the magnitude-mode spectrum. In the absorption mode, the variation of homogeneous broadening, which reports on the dynamics of the spin probe, can even be observed by visual inspection. This new method is illustrated with results from model membranes of dipalmitoyl-sn-glycero-phosphatidylcholine (DPPC)-cholesterol binary mixtures, as well as with results from plasma membrane vesicles of mast cells. In addition to the dynamic parameters, which provide quantitative descriptions for membranes at the molecular level, the high-resolution absorption spectra themselves may be used as a "fingerprint" to characterize membrane phases and distinguish coexisting components in biomembranes. Thus we find that 2D-ELDOR is greatly improved with the new "full Sc- method" especially for exploring the complexity of model and biological membranes.

  17. Silicon waveguide based TE mode converter.

    PubMed

    Zhang, Jing; Liow, Tsung-Yang; Yu, Mingbin; Lo, Guo-Qiang; Kwong, Dim-Lee

    2010-11-22

    A silicon waveguide based TE mode converter was designed for the mode conversion between a horizontal waveguide and vertical waveguide in the two-layer structure waveguide based polarization diversity circuit. The TE mode converter's performance was studied. The polarization mode converter with minimum length of 5 μm was demonstrated to provide the TE mode conversion while maintaining the polarization status. The insertion loss at the transition region was less than 2 dB. PMID:21164874

  18. Positional Isomers of Aspirin Are Equally Potent in Inhibiting Colon Cancer Cell Growth: Differences in Mode of Cyclooxygenase Inhibition

    PubMed Central

    Kodela, Ravinder; Chattopadhyay, Mitali; Goswami, Satindra; Gan, Zong Yuan; Rao, Praveen P. N.; Nia, Kamran V.; Velázquez-Martínez, Carlos A.

    2013-01-01

    We compared the differential effects of positional isomers of acetylsalicylic acid (o-ASA, m-ASA, and p-ASA) on cyclooxygenase (COX) inhibition, gastric prostaglandin E2 (PGE2), malondialdehyde, tumor necrosis factor-alpha (TNF-α) levels, superoxide dismutase (SOD) activity, human adenocarcinoma colon cancer cell growth inhibition, cell proliferation, apoptosis, and cell-cycle progression. We also evaluated the gastric toxicity exerted by ASA isomers. All ASA isomers inhibit COX enzymes, but only the o-ASA exerted an irreversible inhibitory profile. We did not observe a significant difference between ASA isomers in their ability to decrease the in vivo synthesis of PGE2 and SOD activity. Furthermore, all isomers increased the levels of gastric and TNF-α when administered orally at equimolar doses. We observed a dose-dependent cell growth inhibitory effect; the order of potency was p-ASA > m-ASA ≈ o-ASA. There was a dose-dependent decrease in cell proliferation and an increase in apoptosis, with a concomitant Go/G1 arrest. The ulcerogenic profile of the three ASA isomers showed a significant difference between o-ASA (aspirin) and its two positional isomers when administered orally at equimolar doses (1 mmol/kg); the ulcer index (UI) for o-ASA indicated extensive mucosal injury (UI = 38), whereas m-ASA and p-ASA produced a significantly decreased toxic response (UI = 12 and 8, respectively) under the same experimental conditions. These results suggest that the three positional isomers of ASA exert practically the same biologic profile in vitro and in vivo but showed different safety profiles. The mechanism of gastric ulcer formation exerted by aspirin and its two isomers warrants a more detailed and thorough investigation. PMID:23349335

  19. Role of Detuning in the Final Stage of Subharmonic Mode Transition in Boundary Layers

    NASA Technical Reports Server (NTRS)

    Corke, Thomas C.

    2007-01-01

    This work involves mechanisms for transition to turbulence in a Blasius boundary layer through resonant interactions between a plane Tollmien-Schlichting Wave and pairs of oblique waves with equal-but-opposite wave angles. When the frequency of the TS wave is exactly twice that of the oblique waves, we have a "tuned" subharmonic resonance. This leads to the enhanced growth of the oblique modes. Following this, other nonlinear interactions lead to the growth of other 3-D modes which are harmonically based, along with a 3-D mean flow distortion. In the final stage of this process, a gradual spectral filling occurs which we have traced to the growth of fundamental and subharmonic side-band modes. To simulate this with controlled inputs, we introduced the oblique wave pairs at the same conditions, but shifted the frequency of the plane TS mode (by as much as 12 percent) so that it was not exactly twice that of the 3-D modes. These "detuned" conditions also lead to the enhanced growth of the oblique modes, as well as discrete side-band modes which come about through sum and difference interactions. Other interactions quickly lead to a broad band of discrete modes. Of particular importance is the lowest difference frequency which produces a low frequency modulation similar to what has been seen in past experiments with natural 3-D mode input. Cross-bispectral analysis of time series allows us to trace the origin and development of the different modes. Following these leads to a scenario which we believe is more relevant to conditions of "natural" transitions, where low amplitude background disturbances either lead to the gradual detuning of exact fundamental/subharmonic resonance, or in which 3-D mode resonance is detuned from the onset. The results contrast the two conditions, and document the propensity of the 2-D/3-D mode interactions to become detuned.

  20. Differential Cytochrome P450 2D Metabolism Alters Tafenoquine Pharmacokinetics

    PubMed Central

    Vuong, Chau; Xie, Lisa H.; Potter, Brittney M. J.; Zhang, Jing; Zhang, Ping; Duan, Dehui; Nolan, Christina K.; Sciotti, Richard J.; Zottig, Victor E.; Nanayakkara, N. P. Dhammika; Tekwani, Babu L.; Walker, Larry A.; Smith, Philip L.; Paris, Robert M.; Read, Lisa T.; Li, Qigui; Pybus, Brandon S.; Sousa, Jason C.; Reichard, Gregory A.; Smith, Bryan

    2015-01-01

    Cytochrome P450 (CYP) 2D metabolism is required for the liver-stage antimalarial efficacy of the 8-aminoquinoline molecule tafenoquine in mice. This could be problematic for Plasmodium vivax radical cure, as the human CYP 2D ortholog (2D6) is highly polymorphic. Diminished CYP 2D6 enzyme activity, as in the poor-metabolizer phenotype, could compromise radical curative efficacy in humans. Despite the importance of CYP 2D metabolism for tafenoquine liver-stage efficacy, the exact role that CYP 2D metabolism plays in the metabolism and pharmacokinetics of tafenoquine and other 8-aminoquinoline molecules has not been extensively studied. In this study, a series of tafenoquine pharmacokinetic experiments were conducted in mice with different CYP 2D metabolism statuses, including wild-type (WT) (reflecting extensive metabolizers for CYP 2D6 substrates) and CYPmouse 2D knockout (KO) (reflecting poor metabolizers for CYP 2D6 substrates) mice. Plasma and liver pharmacokinetic profiles from a single 20-mg/kg of body weight dose of tafenoquine differed between the strains; however, the differences were less striking than previous results obtained for primaquine in the same model. Additionally, the presence of a 5,6-ortho-quinone tafenoquine metabolite was examined in both mouse strains. The 5,6-ortho-quinone species of tafenoquine was observed, and concentrations of the metabolite were highest in the WT extensive-metabolizer phenotype. Altogether, this study indicates that CYP 2D metabolism in mice affects tafenoquine pharmacokinetics and could have implications for human tafenoquine pharmacokinetics in polymorphic CYP 2D6 human populations. PMID:25870069

  1. Azo dye load-shock on relative behavior of biofilm and suspended growth configured periodic discontinuous batch mode operations: critical evaluation with enzymatic and bio-electrocatalytic analysis.

    PubMed

    Naresh Kumar, A; Nagendranatha Reddy, C; Hari Prasad, R; Venkata Mohan, S

    2014-09-01

    Effect of dye (C.I.Acid Black 10B) load-shock was comparatively evaluated in biofilm (self-immobilized) and suspended growth systems operated in periodic discontinuous batch mode (PDBR, anoxic-aerobic-anoxic) was investigated. At higher dye load (1250 mg dye/l), biofilm system showed relatively higher dye (74.5%) and COD (46%) removal efficiencies than the corresponding suspended mode operation (dye/COD removal efficiency, 42%/65%). Increment in dye load showed increment in azo reductase and dehydrogenase enzyme activities. Voltammograms (cyclic) showed higher reduction currents (RC) with increment in dye load specifically in biofilm system. Derivative cyclic voltammograms analysis depicted the involvement of mediators (NAD (+), FAD(+), etc.) which presumably played a major role in electron transport chain and dye degradation. Disappearance of peak (1612 cm(-1)) specific to azo group in FTIR spectrum, at higher loading rate in both the systems indicates the non-inhibitory and robust nature of PDBR operation. PMID:24859232

  2. Discovery, Characterization, and Functional Study of a Novel MEF2D CAG Repeat in Duck (Anas platyrhynchos).

    PubMed

    Wang, Yushi; Wang, Jiwen; Liu, Hehe; Zhang, Rongping; Zhang, Tao; Gan, Xiang; Huang, Huilan; Chen, Da; Li, Liang

    2016-08-01

    Myocyte enhancer transcription factor 2D (MEF2D) is an important transcription factor for promoting the growth and development of muscle. CAG repeats have been found in the coding sequence (CDS) of avian MEF2D; however, their functions remain unknown and require further investigation. Here, we examined the characteristics and functional role of MEF2D CAG repeat in duck. The full-length CDS of duck MEF2D was cloned for the first time, and a novel CAG repeat was identified and located in exon 9. Sequence analysis indicated that the protein domains of duck MEF2D are highly conserved relative to other vertebrates, whereas MEF2D CAG repeats with variable repeat numbers are specific to avian species. Furthermore, sequencing has revealed polymorphisms in MEF2D CAG repeat at both DNA and mRNA levels. Four MEF2D CAG repeat genotypes and 10 MEF2D cDNA variants with different CAG repeat numbers were detected in two duck populations. A t-test showed that the expanded CAG repeat generated significantly longer transcription products (p < 0.05). Association analysis demonstrated positive correlations between the expansion of the CAG repeat and five muscle-related traits. By using protein structure prediction, we suggested that the polymorphisms of the CAG repeat affect protein structures within protein domains. Taken together, these findings reveal that duck MEF2D CAG repeat is a potential functional element with polymorphisms and may cause differences in MEF2D function between duck and other vertebrate species. PMID:27064738

  3. A Geometric Boolean Library for 2D Objects

    2006-01-05

    The 2D Boolean Library is a collection of C++ classes -- which primarily represent 2D geometric data and relationships, and routines -- which contain algorithms for 2D geometric Boolean operations and utility functions. Classes are provided for 2D points, lines, arcs, edgeuses, loops, surfaces and mask sets. Routines are provided that incorporate the Boolean operations Union(OR), XOR, Intersection and Difference. Various analytical geometry routines and routines for importing and exporting the data in various filemore » formats, are also provided in the library.« less

  4. A Geometric Boolean Library for 2D Objects

    SciTech Connect

    McBride, Corey L.; Yarberry, Victor; Jorgensen, Craig

    2006-01-05

    The 2D Boolean Library is a collection of C++ classes -- which primarily represent 2D geometric data and relationships, and routines -- which contain algorithms for 2D geometric Boolean operations and utility functions. Classes are provided for 2D points, lines, arcs, edgeuses, loops, surfaces and mask sets. Routines are provided that incorporate the Boolean operations Union(OR), XOR, Intersection and Difference. Various analytical geometry routines and routines for importing and exporting the data in various file formats, are also provided in the library.

  5. Evaluation of Comprehensive 2-D Gas Chromatography-Time-Of-Flight Mass Spectrometry for 209 Chlorinated Biphenyl Congeners in Two Chromatographic Runs

    EPA Science Inventory

    This research evaluates a recently developed comprehensive 2-D GC coupled with a time-of-flight (TOF) mass spectrometer for the potential separation of 209 PCB congeners, using a sequence of 1-D and 2-D chromatographic modes. In two consecutive chromatographic runs, using a 40 m,...

  6. Consistent 2-D phase unwrapping guided by a qualtiy map

    SciTech Connect

    Flynn, T.J.

    1995-12-31

    The problem of 2-D phase unwrapping arises when a spatially varying quantity is measured modulo some period. One needs to reconstruct a smooth unwrapped phase, consistent with the original data, by adding a multiple of the period to each sample. Smoothness typically cannot be enforced over all of the scene, due to noise and localized jumps. An unwrapping algorithm may form a mask within which phase discontinuities are allowed. In interferometry a quality map is available, indicating the reliability of the measurements. In this case, the mask should be contained as much as possible in areas of low quality. This paper presents an algorithm for phase unwrapping in which the mask design is guided by the quality map. The mask is grown from the residues (as defined by Goldstein et al.) into areas where the quality is below a threshold. A connected component of the mask stops growing when its residue charge becomes balanced. The threshold is raised as necessary to allow growth. This stage terminates when all components are balanced. The mask is then thinned by removing points that are not needed to cover the residues correctly. The unwrapped phase is found by simple I-D unwrapping along paths that avoid the mask. We present an example solution found by the algorithm and discuss possible modifications.

  7. Vorticity Generation by Rough Walls in 2D Decaying Turbulence

    NASA Astrophysics Data System (ADS)

    Tóth, Gábor; Jánosi, Imre M.

    2015-12-01

    In this work we present Lattice Boltzmann simulations of a decaying vortex array in a 2D rectangular domain, which is bounded by a random rough wall from one side. In order to separate the effects of the collisions with the rough wall, the opposite (smooth) rigid wall is placed at a larger distance from the center of the vortex array. Periodic boundary condition is imposed in the perpendicular direction. Well defined random roughness is generated by the widely studied Wolf-Villain surface growth algorithm. The main finding is that collisions with a rough wall generate excess vorticity compared with a smooth boundary, while the kinetic energy decreases monotonously. A proper measure is the integrated excess enstrophy, which exhibits an apparent maximum at an "optimal" roughness range. Numerical values of the excess enstrophy are very sensitive to a particular configuration (wall shape and vortex lattice randomization), however the "optimal" roughness exhibits surface features of similar characteristic sizes than that of the decaying vortices.

  8. AnisWave2D: User's Guide to the 2d Anisotropic Finite-DifferenceCode

    SciTech Connect

    Toomey, Aoife

    2005-01-06

    This document describes a parallel finite-difference code for modeling wave propagation in 2D, fully anisotropic materials. The code utilizes a mesh refinement scheme to improve computational efficiency. Mesh refinement allows the grid spacing to be tailored to the velocity model, so that fine grid spacing can be used in low velocity zones where the seismic wavelength is short, and coarse grid spacing can be used in zones with higher material velocities. Over-sampling of the seismic wavefield in high velocity zones is therefore avoided. The code has been implemented to run in parallel over multiple processors and allows large-scale models and models with large velocity contrasts to be simulated with ease.

  9. Klassifikation von Standardebenen in der 2D-Echokardiographie mittels 2D-3D-Bildregistrierung

    NASA Astrophysics Data System (ADS)

    Bergmeir, Christoph; Subramanian, Navneeth

    Zum Zweck der Entwicklung eines Systems, das einen unerfahrenen Anwender von Ultraschall (US) zur Aufnahme relevanter anatomischer Strukturen leitet, untersuchen wir die Machbarkeit von 2D-US zu 3D-CT Registrierung. Wir verwenden US-Aufnahmen von Standardebenen des Herzens, welche zu einem 3D-CT-Modell registriert werden. Unser Algorithmus unterzieht sowohl die US-Bilder als auch den CT-Datensatz Vorverarbeitungsschritten, welche die Daten durch Segmentierung auf wesentliche Informationen in Form von Labein für Muskel und Blut reduzieren. Anschließend werden diese Label zur Registrierung mittels der Match-Cardinality-Metrik genutzt. Durch mehrmaliges Registrieren mit verschiedenen Initialisierungen ermitteln wir die im US-Bild sichtbare Standardebene. Wir evaluierten die Methode auf sieben US-Bildern von Standardebenen. Fünf davon wurden korrekt zugeordnet.

  10. Evolution of Modes in Magnetically Insulated Crossed-Field Diodes

    NASA Astrophysics Data System (ADS)

    Cartwright, Keith

    2005-10-01

    The time-dependent behavior of electron sheaths in a magnetically insulated B>BHull anode-cathode gap with crossed electric and magnetic fields is studied. The crossed-field, diode is modeled for various magnetic fields by means of multidimensional (1d and 2d), self-consistent, electromagnetic, particle-in-cell (PIC) simulations. The transient behavior of the system is examined in detail and is divided into three separate stages: cycloidal flow, collapse of cycloidal flow and sheared (near-Brillouin) flow. It has been shown in 1d planar geometry that the cycloidal flows collapse into a steady, near-Brillouin flow. Our 2d electromagnetic PIC simulations (both planar and cylindrical) show that cycloidal flows also collapses into a flow that is dominated by the E cross B drift, but is neither steady nor stable. The growth of the kinetic mode is faster than that of either magnetron or diocotron fluid instability. After the kinetic mode saturates, the fastest growing fluid mode grows to dominate the system. A slow wave structure (SWS) is added to the anode that matches the wavelength and frequency of the fastest growing fluid instability. The SWS is then perturbed so that wavelength and/or frequency does not match the smooth bore diode growth rate and the region of `lock-in' to the SWS is found. This work is supported by a grant from AFOSR.

  11. Alternative binding modes identified for growth and differentiation factor-associated serum protein (GASP) family antagonism of myostatin.

    PubMed

    Walker, Ryan G; Angerman, Elizabeth B; Kattamuri, Chandramohan; Lee, Yun-Sil; Lee, Se-Jin; Thompson, Thomas B

    2015-03-20

    Myostatin, a member of the TGF-β family of ligands, is a strong negative regulator of muscle growth. As such, it is a prime therapeutic target for muscle wasting disorders. Similar to other TGF-β family ligands, myostatin is neutralized by binding one of a number of structurally diverse antagonists. Included are the antagonists GASP-1 and GASP-2, which are unique in that they specifically antagonize myostatin. However, little is known from a structural standpoint describing the interactions of GASP antagonists with myostatin. Here, we present the First low resolution solution structure of myostatin-free and myostatin-bound states of GASP-1 and GASP-2. Our studies have revealed GASP-1, which is 100 times more potent than GASP-2, preferentially binds myostatin in an asymmetrical 1:1 complex, whereas GASP-2 binds in a symmetrical 2:1 complex. Additionally, C-terminal truncations of GASP-1 result in less potent myostatin inhibitors that form a 2:1 complex, suggesting that the C-terminal domains of GASP-1 are the primary mediators for asymmetric complex formation. Overall, this study provides a new perspective on TGF-β antagonism, where closely related antagonists can utilize different ligand-binding strategies. PMID:25657005

  12. Molecular Insights into the Klotho-Dependent, Endocrine Mode of Action of Fibroblast Growth Factor 19 Subfamily Members

    SciTech Connect

    Goetz,R.; Beenken, A.; Ibrahimi, O.; Kalinina, J.; Olsen, S.; Eliseenkova, A.; Xu, C.; Neubert, T.; Zhang, F.; et al.

    2007-01-01

    Unique among fibroblast growth factors (FGFs), FGF19, -21, and -23 act in an endocrine fashion to regulate energy, bile acid, glucose, lipid, phosphate, and vitamin D homeostasis. These FGFs require the presence of Klotho/{beta}Klotho in their target tissues. Here, we present the crystal structures of FGF19 alone and FGF23 in complex with sucrose octasulfate, a disaccharide chemically related to heparin. The conformation of the heparin-binding region between {beta} strands 10 and 12 in FGF19 and FGF23 diverges completely from the common conformation adopted by paracrine-acting FGFs. A cleft between this region and the {beta}1-{beta}2 loop, the other heparin-binding region, precludes direct interaction between heparin/heparan sulfate and backbone atoms of FGF19/23. This reduces the heparin-binding affinity of these ligands and confers endocrine function. Klotho/{beta}Klotho have evolved as a compensatory mechanism for the poor ability of heparin/heparan sulfate to promote binding of FGF19, -21, and -23 to their cognate receptors.

  13. Alternative Binding Modes Identified for Growth and Differentiation Factor-associated Serum Protein (GASP) Family Antagonism of Myostatin*

    PubMed Central

    Walker, Ryan G.; Angerman, Elizabeth B.; Kattamuri, Chandramohan; Lee, Yun-Sil; Lee, Se-Jin; Thompson, Thomas B.

    2015-01-01

    Myostatin, a member of the TGF-β family of ligands, is a strong negative regulator of muscle growth. As such, it is a prime therapeutic target for muscle wasting disorders. Similar to other TGF-β family ligands, myostatin is neutralized by binding one of a number of structurally diverse antagonists. Included are the antagonists GASP-1 and GASP-2, which are unique in that they specifically antagonize myostatin. However, little is known from a structural standpoint describing the interactions of GASP antagonists with myostatin. Here, we present the First low resolution solution structure of myostatin-free and myostatin-bound states of GASP-1 and GASP-2. Our studies have revealed GASP-1, which is 100 times more potent than GASP-2, preferentially binds myostatin in an asymmetrical 1:1 complex, whereas GASP-2 binds in a symmetrical 2:1 complex. Additionally, C-terminal truncations of GASP-1 result in less potent myostatin inhibitors that form a 2:1 complex, suggesting that the C-terminal domains of GASP-1 are the primary mediators for asymmetric complex formation. Overall, this study provides a new perspective on TGF-β antagonism, where closely related antagonists can utilize different ligand-binding strategies. PMID:25657005

  14. Temporal Evolution of the Upper Continental Crust: Implications for the Mode of Crustal Growth and the Evolution of the Hydrosphere

    NASA Astrophysics Data System (ADS)

    Rudnick, R. L.; Gaschnig, R. M.; Li, S.; Tang, M.; Qiu, L.; Valley, J. W.; Zurkowski, C.; McDonough, W. F.

    2014-12-01

    The upper continental crust (UCC), the interface between the atmosphere and solid Earth, is the site of weathering that produces sedimentary rocks, influences ocean chemistry through runoff of soluble elements, and affects climate through CO2 draw-down. The UCC also contains more than 50% of the crust's highly incompatible element budget (including K, Th, and U). Therefore, understanding its composition and evolution provides insight into how continents have formed, evolved, and interacted with the hydrosphere. New major and trace element compositions of >100 glacial diamictites and >100 Archean shales, plus δ7Li and δ18O for a subset of these samples, combined with data from the literature, show that the average composition of the UCC has changed through time, reflecting both the rise of atmospheric oxygen and its attendant effects on weathering, as well as the mode of crust formation and differentiation. Some changes that occur as a step function near the Archean/Proterozoic boundary (increased Th/U, decreased Mo/Pr, V/Lu) reflect the rise of oxygen at the great oxidation event (GOE) and its influence on chemical weathering signatures in the UCC. Other changes are more gradual with time (e.g., higher Th/Sc and δ18O, lower Ni/Co, La/Nb, Eu/Eu* and transition metal abundances) and reflect an UCC that has transitioned from a more mafic to a more felsic bulk composition, and which experienced increased interaction with the hydrosphere with time. The gradual nature of these compositional changes likely reflects the waning heat production of the Earth, rather than an abrupt change in tectonics or style of crust formation. These more gradual changes in crust composition, which contrast with the abrupt changes associated with the GOE, suggest that a fundamental change in the nature of crust differentiation is unlikely to be responsible for the rise of atmospheric oxygen (cf. Keller and Schoene, 2012). Indeed, it appears that the opposite may be true: that the rise of

  15. Growth modes and epitaxy of FeAl thin films on a-cut sapphire prepared by pulsed laser and ion beam assisted deposition

    SciTech Connect

    Yao, Xiang; Trautvetter, Moritz; Ziemann, Paul; Wiedwald, Ulf

    2014-01-14

    FeAl films around equiatomic composition are grown on a-cut (112{sup ¯}0) sapphire substrates by ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD) at ambient temperature. Subsequent successive annealing is used to establish chemical order and crystallographic orientation of the films with respect to the substrate. We find a strongly [110]-textured growth for both deposition techniques. Pole figures prove the successful preparation of high quality epitaxial films by PLD with a single in-plane orientation. IBAD-grown films, however, exhibit three in-plane orientations, all of them with broad angular distributions. The difference of the two growth modes is attributed to the existence of a metastable intermediate crystalline orientation as concluded from nonassisted sputter depositions at different substrate temperatures. The formation of the chemically ordered crystalline B2 phase is accompanied by the expected transition from ferromagnetic to paramagnetic behavior of the films. In accordance with the different thermally induced structural recovery, we find a step-like magnetic transition to paramagnetic behavior after annealing for 1 h at T{sub A} = 300 °C for IBAD deposition, while PLD-grown films show a gradual decrease of ferromagnetic signals with rising annealing temperatures.

  16. Functional characterization of CYP2D6 enhancer polymorphisms

    PubMed Central

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

    2015-01-01

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

  17. Influence of exercise contraction mode and protein supplementation on human skeletal muscle satellite cell content and muscle fiber growth

    PubMed Central

    Farup, Jean; Rahbek, Stine Klejs; Riis, Simon; Vendelbo, Mikkel Holm; de Paoli, Frank

    2014-01-01

    Skeletal muscle satellite cells (SCs) are involved in remodeling and hypertrophy processes of skeletal muscle. However, little knowledge exists on extrinsic factors that influence the content of SCs in skeletal muscle. In a comparative human study, we investigated the muscle fiber type-specific association between emergence of satellite cells (SCs), muscle growth, and remodeling in response to 12 wk unilateral resistance training performed as eccentric (Ecc) or concentric (Conc) resistance training ± whey protein (Whey, 19.5 g protein + 19.5 g glucose) or placebo (Placebo, 39 g glucose) supplementation. Muscle biopsies (vastus lateralis) were analyzed for fiber type-specific SCs, myonuclei, and fiber cross-sectional area (CSA). Following training, SCs increased with Conc in both type I and type II fibers (P < 0.01) and exhibited a group difference from Ecc (P < 0.05), which did not increase. Myonuclei content in type I fibers increased in all groups (P < 0.01), while a specific accretion of myonuclei in type II fibers was observed in the Whey-Conc (P < 0.01) and Placebo-Ecc (P < 0.01) groups. Similarly, whereas type I fiber CSA increased independently of intervention (P < 0.001), type II fiber CSA increased exclusively with Whey-Conc (P < 0.01) and type II fiber hypertrophy correlated with whole muscle hypertrophy exclusively following Conc training (P < 0.01). In conclusion, isolated concentric knee extensor resistance training appears to constitute a stronger driver of SC content than eccentric resistance training while type II fiber hypertrophy was accentuated when combining concentric resistance training with whey protein supplementation. PMID:25103976

  18. Empowering a mesophilic inoculum for thermophilic nitrification: Growth mode and temperature pattern as critical proliferation factors for archaeal ammonia oxidizers.

    PubMed

    Courtens, Emilie N P; Vandekerckhove, Tom; Prat, Delphine; Vilchez-Vargas, Ramiro; Vital, Marius; Pieper, Dietmar H; Meerbergen, Ken; Lievens, Bart; Boon, Nico; Vlaeminck, Siegfried E

    2016-04-01

    Cost-efficient biological treatment of warm nitrogenous wastewaters requires the development of thermophilic nitrogen removal processes. Only one thermophilic nitrifying bioreactor was described so far, achieving 200 mg N L(-1) d(-1) after more than 300 days of enrichment from compost samples. From the practical point of view in which existing plants would be upgraded, however, a more time-efficient development strategy based on mesophilic nitrifying sludge is preferred. This study evaluated the adaptive capacities of mesophilic nitrifying sludge for two linear temperature increase patterns (non-oscillating vs. oscillating), two different slopes (0.25 vs. 0.08 °C d(-1)) and two different reactor types (floc vs. biofilm growth). The oscillating temperature pattern (0.25 °C d(-1)) and the moving bed biofilm reactor (0.08 °C d(-1)) could not reach nitrification at temperatures higher than 46 °C. However, nitrification rates up to 800 mg N L(-1) d(-1) and 150 mg N g(-1) volatile suspended solids d(-1) were achieved at a temperature as high as 49 °C by imposing the slowest linear temperature increase to floccular sludge. Microbial community analysis revealed that this successful transition was related with a shift in ammonium oxidizing archaea dominating ammonia oxidizing bacteria, while for nitrite oxidation Nitrospira spp. was constantly more abundant than Nitrobacter spp.. This observation was accompanied with an increase in observed sludge yield and a shift in maximal optimum temperature, determined with ex-situ temperature sensitivity measurements, predicting an upcoming reactor failure at higher temperature. Overall, this study achieved nitrification at 49 °C within 150 days by gradual adaptation of mesophilic sludge, and showed that ex-situ temperature sensitivity screening can be used to monitor and steer the transition process. PMID:26841233

  19. Probing electric properties at the boundary of planar 2D heterostructure

    NASA Astrophysics Data System (ADS)

    Park, Jewook

    The quest for novel two-dimensional (2D) materials has led to the discovery of hybridized 2D atomic crystals. Especially, planar 2D heterostructure provides opportunities to explore fascinating electric properties at abrupt one-dimensional (1D) boundaries reminiscent to those seen in the 2D interfaces of complex oxides. By implementing the concept of epitaxy to 2D space, we developed a new growth technique to epitaxially grow hexagonal boron nitride (hBN) from the edges of graphene, forming a coherent planar heterostructure. At the interface of hBN and graphene, a polar-on-nonpolar 1D boundary can be formed which is expected to possess peculiar electronic states associated with the polarity of hBN and edge states of graphene Scanning tunneling microscopy and spectroscopy (STM/S) measurements revealed an abrupt 1D zigzag oriented boundary, with boundary states about 0.6 eV below or above the Fermi level depending on the termination of the hBN at the boundary. The boundary states are extended along the boundary and exponentially decay into the bulk of graphene and hBN. Combined STM/S and first-principles theory study not only disclose spatial and energetic distribution of interfacial state but also reveal the origin of boundary states and the effect of the polarity discontinuity at the interface By probing electric properties at the boundary in the atomic scale, planar 2D heterostructure is demonstrated as a promising platform for discovering emergent phenomena at the 1D interface in 2D materials. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

  20. Calculating tissue shear modulus and pressure by 2D Log-Elastographic methods

    PubMed Central

    McLaughlin, Joyce R; Zhang, Ning; Manduca, Armando

    2010-01-01

    Shear modulus imaging, often called elastography, enables detection and characterization of tissue abnormalities. In this paper the data is two displacement components obtained from successive MR or ultrasound data sets acquired while the tissue is excited mechanically. A 2D plane strain elastic model is assumed to govern the 2D displacement, u. The shear modulus, μ, is unknown and whether or not the first Lamé parameter, λ, is known the pressure p = λ∇ · u which is present in the plane strain model cannot be measured and is unreliably computed from measured data and can be shown to be an order one quantity in the units kPa. So here we present a 2D Log-Elastographic inverse algorithm that: (1) simultaneously reconstructs the shear modulus, μ, and p, which together satisfy a first order partial differential equation system, with the goal of imaging μ; (2) controls potential exponential growth in the numerical error; and (3) reliably reconstructs the quantity p in the inverse algorithm as compared to the same quantity computed with a forward algorithm. This work generalizes the Log-Elastographic algorithm in [20] which uses one displacement component, is derived assuming the component satisfies the wave equation, and is tested on synthetic data computed with the wave equation model. The 2D Log-Elastographic algorithm is tested on 2D synthetic data and 2D in-vivo data from Mayo Clinic. We also exhibit examples to show that the 2D Log-Elastographic algorithm improves the quality of the recovered images as compared to the Log-Elastographic and Direct Inversion algorithms. PMID:21822349

  1. An Incompressible 2D Didactic Model with Singularity and Explicit Solutions of the 2D Boussinesq Equations

    NASA Astrophysics Data System (ADS)

    Chae, Dongho; Constantin, Peter; Wu, Jiahong

    2014-09-01

    We give an example of a well posed, finite energy, 2D incompressible active scalar equation with the same scaling as the surface quasi-geostrophic equation and prove that it can produce finite time singularities. In spite of its simplicity, this seems to be the first such example. Further, we construct explicit solutions of the 2D Boussinesq equations whose gradients grow exponentially in time for all time. In addition, we introduce a variant of the 2D Boussinesq equations which is perhaps a more faithful companion of the 3D axisymmetric Euler equations than the usual 2D Boussinesq equations.

  2. Growth

    NASA Astrophysics Data System (ADS)

    Waag, Andreas

    This chapter is devoted to the growth of ZnO. It starts with various techniques to grow bulk samples and presents in some detail the growth of epitaxial layers by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and pulsed laser deposition (PLD). The last section is devoted to the growth of nanorods. Some properties of the resulting samples are also presented. If a comparison between GaN and ZnO is made, very often the huge variety of different growth techniques available to fabricate ZnO is said to be an advantage of this material system. Indeed, growth techniques range from low cost wet chemical growth at almost room temperature to high quality MOCVD growth at temperatures above 1, 000∘C. In most cases, there is a very strong tendency of c-axis oriented growth, with a much higher growth rate in c-direction as compared to other crystal directions. This often leads to columnar structures, even at relatively low temperatures. However, it is, in general, not straight forward to fabricate smooth ZnO thin films with flat surfaces. Another advantage of a potential ZnO technology is said to be the possibility to grow thin films homoepitaxially on ZnO substrates. ZnO substrates are mostly fabricated by vapor phase transport (VPT) or hydrothermal growth. These techniques are enabling high volume manufacturing at reasonable cost, at least in principle. The availability of homoepitaxial substrates should be beneficial to the development of ZnO technology and devices and is in contrast to the situation of GaN. However, even though a number of companies are developing ZnO substrates, only recently good quality substrates have been demonstrated. However, these substrates are not yet widely available. Still, the situation concerning ZnO substrates seems to be far from low-cost, high-volume production. The fabrication of dense, single crystal thin films is, in general, surprisingly difficult, even when ZnO is grown on a ZnO substrate. However

  3. Implicit adaptive mesh refinement for 2D reduced resistive magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Philip, Bobby; Chacón, Luis; Pernice, Michael

    2008-10-01

    An implicit structured adaptive mesh refinement (SAMR) solver for 2D reduced magnetohydrodynamics (MHD) is described. The time-implicit discretization is able to step over fast normal modes, while the spatial adaptivity resolves thin, dynamically evolving features. A Jacobian-free Newton-Krylov method is used for the nonlinear solver engine. For preconditioning, we have extended the optimal "physics-based" approach developed in [L. Chacón, D.A. Knoll, J.M. Finn, An implicit, nonlinear reduced resistive MHD solver, J. Comput. Phys. 178 (2002) 15-36] (which employed multigrid solver technology in the preconditioner for scalability) to SAMR grids using the well-known Fast Adaptive Composite grid (FAC) method [S. McCormick, Multilevel Adaptive Methods for Partial Differential Equations, SIAM, Philadelphia, PA, 1989]. A grid convergence study demonstrates that the solver performance is independent of the number of grid levels and only depends on the finest resolution considered, and that it scales well with grid refinement. The study of error generation and propagation in our SAMR implementation demonstrates that high-order (cubic) interpolation during regridding, combined with a robustly damping second-order temporal scheme such as BDF2, is required to minimize impact of grid errors at coarse-fine interfaces on the overall error of the computation for this MHD application. We also demonstrate that our implementation features the desired property that the overall numerical error is dependent only on the finest resolution level considered, and not on the base-grid resolution or on the number of refinement levels present during the simulation. We demonstrate the effectiveness of the tool on several challenging problems.

  4. Investigations on Substrate Temperature-Induced Growth Modes of Organic Semiconductors at Dielectric/semiconductor Interface and Their Correlation with Threshold Voltage Stability in Organic Field-Effect Transistors.

    PubMed

    Padma, Narayanan; Maheshwari, Priya; Bhattacharya, Debarati; Tokas, Raj B; Sen, Shashwati; Honda, Yoshihide; Basu, Saibal; Pujari, Pradeep Kumar; Rao, T V Chandrasekhar

    2016-02-10

    Influence of substrate temperature on growth modes of copper phthalocyanine (CuPc) thin films at the dielectric/semiconductor interface in organic field effect transistors (OFETs) is investigated. Atomic force microscopy (AFM) imaging at the interface reveals a change from 'layer+island' to "island" growth mode with increasing substrate temperatures, further confirmed by probing the buried interfaces using X-ray reflectivity (XRR) and positron annihilation spectroscopic (PAS) techniques. PAS depth profiling provides insight into the details of molecular ordering while positron lifetime measurements reveal the difference in packing modes of CuPc molecules at the interface. XRR measurements show systematic increase in interface width and electron density correlating well with the change from layer + island to coalesced huge 3D islands at higher substrate temperatures. Study demonstrates the usefulness of XRR and PAS techniques to study growth modes at buried interfaces and reveals the influence of growth modes of semiconductor at the interface on hole and electron trap concentrations individually, thereby affecting hysteresis and threshold voltage stability. Minimum hole trapping is correlated to near layer by layer formation close to the interface at 100 °C and maximum to the island formation with large voids between the grains at 225 °C. PMID:26761590

  5. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density. PMID:27334788

  6. Integrating Mobile Multimedia into Textbooks: 2D Barcodes

    ERIC Educational Resources Information Center

    Uluyol, Celebi; Agca, R. Kagan

    2012-01-01

    The major goal of this study was to empirically compare text-plus-mobile phone learning using an integrated 2D barcode tag in a printed text with three other conditions described in multimedia learning theory. The method examined in the study involved modifications of the instructional material such that: a 2D barcode was used near the text, the…

  7. The unified ballooning theory with weak up-down asymmetric mode structure and the numerical studies

    NASA Astrophysics Data System (ADS)

    Xie, T.; Qin, H.; Zhang, Y. Z.; Mahajan, S. M.

    2016-04-01

    A unified ballooning theory, constructed on the basis of two special theories [Zhang et al., Phys. Fluids B 4, 2729 (1992); Y. Z. Zhang and T. Xie, Nucl. Fusion Plasma Phys. 33, 193 (2013)], shows that a weak up-down asymmetric mode structure is normally formed in an up-down symmetric equilibrium; the weak up-down asymmetry in mode structure is the manifestation of non-trivial higher order effects beyond the standard ballooning equation. It is shown that the asymmetric mode may have even higher growth rate than symmetric modes. The salient features of the theory are illustrated by investigating a fluid model for the ion temperature gradient (ITG) mode. The two dimensional (2D) analytical form of the ITG mode, solved in ballooning representation, is then converted into the radial-poloidal space to provide the natural boundary condition for solving the 2D mathematical local eigenmode problem. We find that the analytical expression of the mode structure is in a good agreement with finite difference solution. This sets a reliable framework for quasi-linear computation.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  9. Unitary quantum lattice gas representation of 2D quantum turbulence

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Vahala, George; Vahala, Linda; Soe, Min

    2011-05-01

    Quantum vortex structures and energy cascades are examined for two dimensional quantum turbulence (2D QT) using a special unitary evolution algorithm. The qubit lattice gas (QLG) algorithm, is employed to simulate the weakly-coupled Bose-Einstein condensate (BEC) governed by the Gross-Pitaevskii (GP) equation. A parameter regime is uncovered in which, as in 3D QT, there is a very short Poincare recurrence time. This short recurrence time is destroyed as the nonlinear interaction energy is increased. Energy cascades for 2D QT are considered to examine whether 2D QT exhibits the inverse cascades of 2D classical turbulence. In the parameter regime considered, the spectra analysis reveals no such dual cascades---dual cascades being a hallmark of 2D classical turbulence.

  10. CYP2D6 polymorphism in patients with eating disorders.

    PubMed

    Peñas-Lledó, E M; Dorado, P; Agüera, Z; Gratacós, M; Estivill, X; Fernández-Aranda, F; Llerena, A

    2012-04-01

    CYP2D6 polymorphism is associated with variability in drug response, endogenous metabolism (that is, serotonin), personality, neurocognition and psychopathology. The relationship between CYP2D6 genetic polymorphism and the risk of eating disorders (ED) was analyzed in 267 patients with ED and in 285 controls. A difference in the CYP2D6 active allele distribution was found between these groups. Women carrying more than two active genes (ultrarapid metabolizers) (7.5 vs 4.6%) or two (67 vs 58.9%) active genes were more frequent among patients with ED, whereas those with one (20.6 vs 30.2%) or zero active genes (4.9 vs 6.3%) were more frequent among controls (P<0.05). Although further research is needed, present findings suggest an association between CYP2D6 and ED. CYP2D6 allele distribution in patients with ED seems related to increased enzyme activity. PMID:20877302

  11. 2D materials and van der Waals heterostructures.

    PubMed

    Novoselov, K S; Mishchenko, A; Carvalho, A; Castro Neto, A H

    2016-07-29

    The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With these new materials, truly 2D physics has begun to appear (for instance, the absence of long-range order, 2D excitons, commensurate-incommensurate transition, etc.). Novel heterostructure devices--such as tunneling transistors, resonant tunneling diodes, and light-emitting diodes--are also starting to emerge. Composed from individual 2D crystals, such devices use the properties of those materials to create functionalities that are not accessible in other heterostructures. Here we review the properties of novel 2D crystals and examine how their properties are used in new heterostructure devices. PMID:27471306

  12. Narrow growth window for stoichiometric, layer-by-layer growth of LaAlO3 thin films using pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Golalikhani, M.; Lei, Q. Y.; Wolak, M. A.; Davidson, B. A.; Xi, X. X.

    2016-06-01

    We study the structure and surface morphology of the 100 nm homoepitaxial LaAlO3 films grown by pulsed laser deposition in a broad range of growth parameters. We show that there is a narrow window of growth conditions in which the stoichiometric, bulk-like structure is obtained while maintaining a 2-dimensional (2D) layer-by-layer growth mode. In our system, these optimum growth conditions are 100 mTorr background pressure with laser energy density 1.5-2 J/cm2. The sensitivity to growth conditions of the stoichiometry and structure of LaAlO3 films can have a crucial role in the 2-D electron gas formed at the LaAlO3/SrTiO3 interface.

  13. Critical role of the NKG2D receptor for NK cell-mediated control and immune escape of B-cell lymphoma.

    PubMed

    Belting, Lena; Hömberg, Nadine; Przewoznik, Margarethe; Brenner, Christoph; Riedel, Tanja; Flatley, Andrew; Polić, Bojan; Busch, Dirk H; Röcken, Martin; Mocikat, Ralph

    2015-09-01

    Little is known on the control of lymphomas by NK cells. Here, we study the role of the NK group 2D (NKG2D) receptor for the immunosurveillance of lymphoma. By using transplantable tumors as well as a λ-myc-transgenic model of endogenously arising lymphoma and NKG2D-deficient mice, we show that NK cells eliminate tumor cells in vivo after receiving two signals. One step involved the activation of NK cells giving rise to IFN-γ expression, which was effected by MHCI(low) tumor cells or DCs. However, this was necessary but not sufficient to mediate cytotoxicity. Triggering cytotoxicity additionally required a second step, which could be mediated by engagement of the NKG2D receptor. Thus, NKG2D-deficient NK cells could become activated in vivo, but they were not able to reject transplanted lymphomas or to degranulate in animals bearing autochthonous lymphomas. Tumor growth in NKG2D-deficient λ-myc-transgenic mice was significantly accelerated compared to NKG2D-competent animals. Whereas the latter developed tumors that lost expression of NKG2D ligands (NKG2D-L) in late disease stages, this did not occur in NKG2D-deficient mice. This indicates that NK cells and the NKG2D receptor play a role for control of lymphomas and that selection for NKG2D-L loss mutants provides a mechanism of tumor escape. PMID:26151313

  14. Targeted fluorescence imaging enhanced by 2D materials: a comparison between 2D MoS2 and graphene oxide.

    PubMed

    Xie, Donghao; Ji, Ding-Kun; Zhang, Yue; Cao, Jun; Zheng, Hu; Liu, Lin; Zang, Yi; Li, Jia; Chen, Guo-Rong; James, Tony D; He, Xiao-Peng

    2016-08-01

    Here we demonstrate that 2D MoS2 can enhance the receptor-targeting and imaging ability of a fluorophore-labelled ligand. The 2D MoS2 has an enhanced working concentration range when compared with graphene oxide, resulting in the improved imaging of both cell and tissue samples. PMID:27378648

  15. Quantum (in)stability of 2D charged dilaton black holes and 3D rotating black holes

    NASA Astrophysics Data System (ADS)

    Nojiri, Shin'ichi; Odintsov, Sergei D.

    1999-02-01

    The quantum properties of charged black holes (BHs) in two-dimensional (2D) dilaton-Maxwell gravity (spontaneously compactified from heterotic string) with N dilaton coupled scalars are studied. We first investigate 2D BHs found by McGuigan, Nappi, and Yost. Kaluza-Klein reduction of 3D gravity with minimal scalars leads also to 2D dilaton-Maxwell gravity with dilaton coupled scalars and the rotating BH solution found by Bañados, Teitelboim, and Zanelli, which can be also described by 2D charged dilatonic BHs. Evaluating the one-loop effective action for dilaton coupled scalars in large N (and the s-wave approximation for the Bañados-Teitelboim-Zanelli case), we show that quantum-corrected BHs may evaporate or else antievaporate similarly to 4D Nariai BHs as is observed by Bousso and Hawking. Higher modes may cause the disintegration of BHs in accordance with recent observation by Bousso.

  16. 2D Doppler backscattering using synthetic aperture microwave imaging of MAST edge plasmas

    NASA Astrophysics Data System (ADS)

    Thomas, D. A.; Brunner, K. J.; Freethy, S. J.; Huang, B. K.; Shevchenko, V. F.; Vann, R. G. L.

    2016-02-01

    Doppler backscattering (DBS) is already established as a powerful diagnostic; its extension to 2D enables imaging of turbulence characteristics from an extended region of the cut-off surface. The Synthetic Aperture Microwave Imaging (SAMI) diagnostic has conducted proof-of-principle 2D DBS experiments of MAST edge plasma. SAMI actively probes the plasma edge using a wide (±40° vertical and horizontal) and tuneable (10-34.5 GHz) beam. The Doppler backscattered signal is digitised in vector form using an array of eight Vivaldi PCB antennas. This allows the receiving array to be focused in any direction within the field of view simultaneously to an angular range of 6-24° FWHM at 10-34.5 GHz. This capability is unique to SAMI and is a novel way of conducting DBS experiments. In this paper the feasibility of conducting 2D DBS experiments is explored. Initial observations of phenomena previously measured by conventional DBS experiments are presented; such as momentum injection from neutral beams and an abrupt change in power and turbulence velocity coinciding with the onset of H-mode. In addition, being able to carry out 2D DBS imaging allows a measurement of magnetic pitch angle to be made; preliminary results are presented. Capabilities gained through steering a beam using a phased array and the limitations of this technique are discussed.

  17. Inspection design using 2D phased array, TFM and cueMAP software

    SciTech Connect

    McGilp, Ailidh; Dziewierz, Jerzy; Lardner, Tim; Mackersie, John; Gachagan, Anthony

    2014-02-18

    A simulation suite, cueMAP, has been developed to facilitate the design of inspection processes and sparse 2D array configurations. At the core of cueMAP is a Total Focusing Method (TFM) imaging algorithm that enables computer assisted design of ultrasonic inspection scenarios, including the design of bespoke array configurations to match the inspection criteria. This in-house developed TFM code allows for interactive evaluation of image quality indicators of ultrasonic imaging performance when utilizing a 2D phased array working in FMC/TFM mode. The cueMAP software uses a series of TFM images to build a map of resolution, contrast and sensitivity of imaging performance of a simulated reflector, swept across the inspection volume. The software takes into account probe properties, wedge or water standoff, and effects of specimen curvature. In the validation process of this new software package, two 2D arrays have been evaluated on 304n stainless steel samples, typical of the primary circuit in nuclear plants. Thick section samples have been inspected using a 1MHz 2D matrix array. Due to the processing efficiency of the software, the data collected from these array configurations has been used to investigate the influence sub-aperture operation on inspection performance.

  18. Decorating the Edges of a 2D Polymer with a Fluorescence Label.

    PubMed

    Zhao, Yingjie; Bernitzky, Richard H M; Kory, Max J; Hofer, Gregor; Hofkens, Johan; Schlüter, A Dieter

    2016-07-20

    This work proves the existence and chemical addressability of defined edge groups of a 2D polymer. Pseudohexagonally prismatic single crystals consisting of layered stacks of a 2D polymer are used. They should expose anthracene-based edge groups at the six (100) but not at the two pseudohexagonal (001) and (001̅) faces. The crystals are reacted with the isotopically enriched dienophiles maleic anhydride and a C18-alkyl chain-modified maleimide. In both cases the corresponding Diels-Alder adducts between these reagents and the edge groups are formed as confirmed by solid state NMR spectroscopy. The same applies to a maleimide derivative carrying a BODIPY dye which was chosen for its fluorescence to be out of the range of the self-fluorescence of the 2D polymer crystals stemming from contained template molecules. If the crystals are excited at λ = 633 nm, their (100) faces and thus their rims fluoresce brightly, while the pseudohexagonal faces remain silent. This is visible when the crystals lie on a pseudohexagonal face. Lambda-mode laser scanning microscopy confirms this fluorescence to originate from the BODIPY dye. Micromechanical exfoliation of the dye-modified crystals results in thinner sheet packages which still exhibit BODIPY fluorescence right at the rim of these packages. This work establishes the chemical nature of the edge groups of a 2D polymer and is also the first implementation of an edge group modification similar to end group modifications of linear polymers. PMID:27347597

  19. Inspection design using 2D phased array, TFM and cueMAP software

    NASA Astrophysics Data System (ADS)

    McGilp, Ailidh; Dziewierz, Jerzy; Lardner, Tim; Mackersie, John; Gachagan, Anthony

    2014-02-01

    A simulation suite, cueMAP, has been developed to facilitate the design of inspection processes and sparse 2D array configurations. At the core of cueMAP is a Total Focusing Method (TFM) imaging algorithm that enables computer assisted design of ultrasonic inspection scenarios, including the design of bespoke array configurations to match the inspection criteria. This in-house developed TFM code allows for interactive evaluation of image quality indicators of ultrasonic imaging performance when utilizing a 2D phased array working in FMC/TFM mode. The cueMAP software uses a series of TFM images to build a map of resolution, contrast and sensitivity of imaging performance of a simulated reflector, swept across the inspection volume. The software takes into account probe properties, wedge or water standoff, and effects of specimen curvature. In the validation process of this new software package, two 2D arrays have been evaluated on 304n stainless steel samples, typical of the primary circuit in nuclear plants. Thick section samples have been inspected using a 1MHz 2D matrix array. Due to the processing efficiency of the software, the data collected from these array configurations has been used to investigate the influence sub-aperture operation on inspection performance.

  20. A self-running ultrasonically levitated 2D stage using flexural vibrating plates

    NASA Astrophysics Data System (ADS)

    Koyama, Daisuke; Nakamura, Kentaro

    2010-01-01

    A non-contact self-running ultrasonically levitated 2D stage is discussed. In our previous work, the ultrasonically levitated linear slider for a self-running sliding stage was investigated. When the flexural vibration mode is excited along the slider, the slider on the flat substrate can be levitated due to the acoustic radiation force from the own vibrating plate. The slider can move the same direction as the acoustic streaming induced along the air gap. The proposed 2D stage was fabricated from a rectangular aluminum plate and the four vibrating plates were integrated. The vibrating plates are cantilever-type and the PZT elements are attached on the fixed-end of the vibrating plates. The 2D stage has four our previous linear sliders, two pairs both in x and y directions. To isolate the performances of each vibrating plate, the four vibrating plates with different lengths were designed. The 2D stage could be levitated at the several frequencies from 60 to 70 kHz. By changing the driving frequency, the moving direction of the stage could be controlled. The maximum thrust of 5.3 mN could be obtained at 71 kHz with 70 Vpp.

  1. Roton Excitations and the Fluid-Solid Phase Transition in Superfluid 2D Yukawa Bosons

    NASA Astrophysics Data System (ADS)

    Molinelli, S.; Galli, D. E.; Reatto, L.; Motta, M.

    2016-05-01

    We compute several ground-state properties and the dynamical structure factor of a zero-temperature system of Bosons interacting with the 2D screened Coulomb (2D-SC) potential. We resort to the exact shadow path integral ground state (SPIGS) quantum Monte Carlo method to compute the imaginary-time correlation function of the model, and to the genetic algorithm via falsification of theories (GIFT) to retrieve the dynamical structure factor. We provide a detailed comparison of ground-state properties and collective excitations of 2D-SC and ^4 He atoms. The roton energy of the 2D-SC system is an increasing function of density, and not a decreasing one as in ^4 He. This result is in contrast with the view that the roton is the soft mode of the fluid-solid transition. We uncover a remarkable quasi-universality of backflow and of other properties when expressed in terms of the amount of short-range order as quantified by the height of the first peak of the static structure factor.

  2. Transient 2D IR spectroscopy of charge injection in dye-sensitized nanocrystalline thin films.

    PubMed

    Xiong, Wei; Laaser, Jennifer E; Paoprasert, Peerasak; Franking, Ryan A; Hamers, Robert J; Gopalan, Padma; Zanni, Martin T

    2009-12-23

    We use nonlinear 2D IR spectroscopy to study TiO(2) nanocrystalline thin films sensitized with a Re dye. We find that the free electron signal, which often obscures the vibrational features in the transient absorption spectrum, is not observed in the 2D IR spectra. Its absence allows the vibrational features of the dye to be much better resolved than with the typical IR absorption probe. We observe multiple absorption bands but no cross peaks in the 2D IR spectra, which indicates that the dyes have at least three conformations. Furthermore, by using a pulse sequence in which we initiate electron transfer in the middle of the infrared pulse train, we are able to assign the excited state features by correlating them to the ground state vibrational modes and determine that the three conformations have different time scales and cross sections for electron injection. 2D IR spectroscopy is proving to be very useful in disentangling overlapping structural distributions in biological and chemical physics processes. These experiments demonstrate that nonlinear infrared probes are also a powerful new tool for studying charge transfer at interfaces. PMID:19947603

  3. Turbulent boundary layer over 2D and 3D large-scale wavy walls

    NASA Astrophysics Data System (ADS)

    Chamorro, Leonardo P.; Hamed, Ali M.; Castillo, Luciano

    2015-11-01

    In this work, an experimental investigation of the developing and developed flow over two- and three-dimensional large-scale wavy walls was performed using high-resolution planar particle image velocimetry in a refractive-index-matching flume. The 2D wall is described by a sinusoidal wave in the streamwise direction with amplitude to wavelength ratio a/ λx = 0.05. The 3D wall is defined with an additional wave superimposed on the 2D wall in the spanwise direction with a/ λy = 0.1. The flow was characterized at Reynolds numbers of 4000 and 40000, based on the bulk velocity and the flume half height. Instantaneous velocity fields and time-averaged turbulence quantities reveal strong coupling between large-scale topography and the turbulence dynamics near the wall. Turbulence statistics show the presence of a well-structured shear layer that enhances the turbulence for the 2D wavy wall, whereas the 3D wall exhibits different flow dynamics and significantly lower turbulence levels, particularly for which shows about 30% reduction. The likelihood of recirculation bubbles, levels and spatial distribution of turbulence, and the rate of the turbulent kinetic energy production are shown to be severely affected when a single spanwise mode is superimposed on the 2D wall. POD analysis was also performed to further understand distinctive features of the flow structures due to surface topography.

  4. Effective Temperature of 2D Dusty Plasma Liquids at the Discrete Level

    SciTech Connect

    Io, C.-W.; Chan, C.-L.; I Lin

    2007-07-13

    Fluctuation-dissipation theory has been used to measure the effective temperature of non-equilibrium system. In this work, using a 2D dusty plasma liquid formed by the negatively charged fine particles suspending in weakly ionized discharges and sheared by two CW counter parallel laser beams, we measure the micro-transport at the kinetic level. The effective temperatures Teff at different time scales are obtained through the Stokes-Einstein relation which relates the diffusion coefficient (D) and the viscosity ({eta}). The external energy is cascaded from the slow hopping modes to the fast caging modes through mutual coupling, which leads to the higher effective temperature of the slow hopping modes.

  5. 2D vs. 3D mammography observer study

    NASA Astrophysics Data System (ADS)

    Fernandez, James Reza F.; Hovanessian-Larsen, Linda; Liu, Brent

    2011-03-01

    Breast cancer is the most common type of non-skin cancer in women. 2D mammography is a screening tool to aid in the early detection of breast cancer, but has diagnostic limitations of overlapping tissues, especially in dense breasts. 3D mammography has the potential to improve detection outcomes by increasing specificity, and a new 3D screening tool with a 3D display for mammography aims to improve performance and efficiency as compared to 2D mammography. An observer study using a mammography phantom was performed to compare traditional 2D mammography with this ne 3D mammography technique. In comparing 3D and 2D mammography there was no difference in calcification detection, and mass detection was better in 2D as compared to 3D. There was a significant decrease in reading time for masses, calcifications, and normals in 3D compared to 2D, however, as well as more favorable confidence levels in reading normal cases. Given the limitations of the mammography phantom used, however, a clearer picture in comparing 3D and 2D mammography may be better acquired with the incorporation of human studies in the future.

  6. Efficient 2D MRI relaxometry using compressed sensing

    NASA Astrophysics Data System (ADS)

    Bai, Ruiliang; Cloninger, Alexander; Czaja, Wojciech; Basser, Peter J.

    2015-06-01

    Potential applications of 2D relaxation spectrum NMR and MRI to characterize complex water dynamics (e.g., compartmental exchange) in biology and other disciplines have increased in recent years. However, the large amount of data and long MR acquisition times required for conventional 2D MR relaxometry limits its applicability for in vivo preclinical and clinical MRI. We present a new MR pipeline for 2D relaxometry that incorporates compressed sensing (CS) as a means to vastly reduce the amount of 2D relaxation data needed for material and tissue characterization without compromising data quality. Unlike the conventional CS reconstruction in the Fourier space (k-space), the proposed CS algorithm is directly applied onto the Laplace space (the joint 2D relaxation data) without compressing k-space to reduce the amount of data required for 2D relaxation spectra. This framework is validated using synthetic data, with NMR data acquired in a well-characterized urea/water phantom, and on fixed porcine spinal cord tissue. The quality of the CS-reconstructed spectra was comparable to that of the conventional 2D relaxation spectra, as assessed using global correlation, local contrast between peaks, peak amplitude and relaxation parameters, etc. This result brings this important type of contrast closer to being realized in preclinical, clinical, and other applications.

  7. NKG2D receptor and its ligands in host defense

    PubMed Central

    Lanier, Lewis L.

    2015-01-01

    NKG2D is an activating receptor expressed on the surface of natural killer (NK) cells, CD8+ T cells, and subsets of CD4+ T cells, iNKT cells, and γδ T cells. In humans NKG2D transmits signals by its association with the DAP10 adapter subunit and in mice alternatively spliced isoforms transmit signals either using DAP10 or DAP12 adapter subunits. Although NKG2D is encoded by a highly conserved gene (KLRK1) with limited polymorphism, the receptor recognizes an extensive repertoire of ligands, encoded by at least 8 genes in humans (MICA, MICB, RAET1E, RAET1G, RAET1H, RAET1I, RAET1L, and RAET1N), some with extensive allelic polymorphism. Expression of the NKG2D ligands is tightly regulated at the level of transcription, translation, and post-translation. In general healthy adult tissues do not express NKG2D glycoproteins on the cell surface, but these ligands can be induced by hyper-proliferation and transformation, as well as when cells are infected by pathogens. Thus, the NKG2D pathway serves a mechanism for the immune system to detect and eliminate cells that have undergone “stress”. Viruses and tumor cells have devised numerous strategies to evade detection by the NKG2D surveillance system and diversification of the NKG2D ligand genes likely has been driven by selective pressures imposed by pathogens. NKG2D provides an attractive target for therapeutics in the treatment of infectious diseases, cancer, and autoimmune diseases. PMID:26041808

  8. Recent advances in 2D materials for photocatalysis

    NASA Astrophysics Data System (ADS)

    Luo, Bin; Liu, Gang; Wang, Lianzhou

    2016-03-01

    Two-dimensional (2D) materials have attracted increasing attention for photocatalytic applications because of their unique thickness dependent physical and chemical properties. This review gives a brief overview of the recent developments concerning the chemical synthesis and structural design of 2D materials at the nanoscale and their applications in photocatalytic areas. In particular, recent progress on the emerging strategies for tailoring 2D material-based photocatalysts to improve their photo-activity including elemental doping, heterostructure design and functional architecture assembly is discussed.

  9. Comparison of 2D and 3D gamma analyses

    SciTech Connect

    Pulliam, Kiley B.; Huang, Jessie Y.; Howell, Rebecca M.; Followill, David; Kry, Stephen F.; Bosca, Ryan; O’Daniel, Jennifer

    2014-02-15

    Purpose: As clinics begin to use 3D metrics for intensity-modulated radiation therapy (IMRT) quality assurance, it must be noted that these metrics will often produce results different from those produced by their 2D counterparts. 3D and 2D gamma analyses would be expected to produce different values, in part because of the different search space available. In the present investigation, the authors compared the results of 2D and 3D gamma analysis (where both datasets were generated in the same manner) for clinical treatment plans. Methods: Fifty IMRT plans were selected from the authors’ clinical database, and recalculated using Monte Carlo. Treatment planning system-calculated (“evaluated dose distributions”) and Monte Carlo-recalculated (“reference dose distributions”) dose distributions were compared using 2D and 3D gamma analysis. This analysis was performed using a variety of dose-difference (5%, 3%, 2%, and 1%) and distance-to-agreement (5, 3, 2, and 1 mm) acceptance criteria, low-dose thresholds (5%, 10%, and 15% of the prescription dose), and data grid sizes (1.0, 1.5, and 3.0 mm). Each comparison was evaluated to determine the average 2D and 3D gamma, lower 95th percentile gamma value, and percentage of pixels passing gamma. Results: The average gamma, lower 95th percentile gamma value, and percentage of passing pixels for each acceptance criterion demonstrated better agreement for 3D than for 2D analysis for every plan comparison. The average difference in the percentage of passing pixels between the 2D and 3D analyses with no low-dose threshold ranged from 0.9% to 2.1%. Similarly, using a low-dose threshold resulted in a difference between the mean 2D and 3D results, ranging from 0.8% to 1.5%. The authors observed no appreciable differences in gamma with changes in the data density (constant difference: 0.8% for 2D vs 3D). Conclusions: The authors found that 3D gamma analysis resulted in up to 2.9% more pixels passing than 2D analysis. It must

  10. Materials for Flexible, Stretchable Electronics: Graphene and 2D Materials

    NASA Astrophysics Data System (ADS)

    Kim, Sang Jin; Choi, Kyoungjun; Lee, Bora; Kim, Yuna; Hong, Byung Hee

    2015-07-01

    Recently, 2D materials have been intensively studied as emerging materials for future electronics, including flexible electronics, photonics, and electrochemical energy storage devices. Among representative 2D materials (such as graphene, boron nitride, and transition metal dichalcogenides) that exhibit extraordinary properties, graphene stands out in the flexible electronics field due to its combination of high electron mobility, high thermal conductivity, high specific surface area, high optical transparency, excellent mechanical flexibility, and environmental stability. This review covers the synthesis, transfer, and characterization methods of graphene and 2D materials and graphene's application to flexible devices as well as comparison with other competing materials.

  11. The TRPC channel blocker SKF 96365 inhibits glioblastoma cell growth by enhancing reverse mode of the Na+/Ca2+ exchanger and increasing intracellular Ca2+

    PubMed Central

    Song, M; Chen, D; Yu, S P

    2014-01-01

    BACKGROUND AND PURPOSE SKF 96365 is well known for its suppressing effect on human glioblastoma growth by inhibiting pre-activated transient receptor potential canonical (TRPC) channels and Ca2+ influx. The effect of SKF 96363 on glioblastoma cells, however, may be multifaceted and this possibility has been largely ignored. EXPERIMENTAL APPROACH The effects of SKF 96365 on cell cycle and cell viability of cultured human glioblastoma cells were characterized. Western blot, Ca2+ imaging and patch clamp recordings were used to delineate cell death mechanisms. siRNA gene knockdown provided additional evidence. KEY RESULTS SKF 96365 repressed glioblastoma cell growth via increasing intracellular Ca2+ ([Ca2+]i) irrespective of whether TRPC channels were blocked or not. The effect of SKF 96365 primarily resulted from enhanced reverse operation of the Na+/Ca2+ exchanger (NCX) with an EC50 of 9.79 μM. SKF 96365 arrested the glioblastoma cells in the S and G2 phases and activated p38-MAPK and JNK, which were all prevented by the Ca2+ chelator BAPTA-AM or EGTA. The expression of NCX in glioblastoma cells was significantly higher than in normal human astrocytes. Knockdown of the NCX1 isoforms diminished the effect of SKF 96365 on glioblastoma cells. CONCLUSIONS AND IMPLICATIONS At the same concentration, SKF 96365 blocks TRPC channels and enhances the reverse mode of the NCX causing [Ca2+]i accumulation and cytotoxicity. This finding suggests an alternative pharmacological mechanism of SKF 96365. It also indicates that modulation of the NCX is an effective method to disrupt Ca2+ homeostasis and suppress human glioblastoma cells. PMID:24641279

  12. Global gyrokinetic stability of collisionless microtearing modes in large aspect ratio tokamaks

    SciTech Connect

    Swamy, Aditya K.; Ganesh, R.; Chowdhury, J.; Brunner, S.; Vaclavik, J.; Villard, L.

    2014-08-15

    Linear full radius gyrokinetic calculations show the existence of unstable microtearing modes (MTMs) in purely collisionless, high temperature, large aspect ratio tokamak plasmas. The present study takes into account fully gyrokinetic highly passing ions and electrons. The global 2-D structures of the collisionless mode with full radius coupling of the poloidal modes is obtained and compared with another electromagnetic mode, namely, the Alfvén Ion Temperature Gradient (AITG) mode (or Kinetic Ballooning Mode, KBM) for the same equilibrium profile. Several important characteristics of the modes are brought out and compared, such as a clear signature in the symmetry properties of the two modes, the plasma–β dependence, and radial and poloidal length scales of the electrostatic and magnetic vector potential fluctuations. Extensive parameter scans for this collisionless microtearing mode reveal the scaling of the growth rate with β and the electron temperature gradient η{sub e}. Scans at different β values show an inverse relationship between the η{sub e} threshold and β, leading to a stability diagram, and implying that the mode might exist at moderate to strong temperature gradients for finite β plasmas in large aspect ratio tokamaks. In contrast to small aspect ratio tokamaks where the trapped electron magnetic drift resonance is found to be important, in large aspect ratio tokamaks, a strong destabilization due to the magnetic drift resonance of passing electrons is observed and is identified as a possible collisionless drive mechanism for the collisionless MTM.

  13. Calculating tissue shear modulus and pressure by 2D Log-Elastographic methods.

    PubMed

    McLaughlin, Joyce R; Zhang, Ning; Manduca, Armando

    2010-01-01

    Shear modulus imaging, often called elastography, enables detection and characterization of tissue abnormalities. In this paper the data is two displacement components obtained from successive MR or ultrasound data sets acquired while the tissue is excited mechanically. A 2D plane strain elastic model is assumed to govern the 2D displacement, u. The shear modulus, μ, is unknown and whether or not the first Lamé parameter, λ, is known the pressure p = λ∇ · u which is present in the plane strain model cannot be measured and is unreliably computed from measured data and can be shown to be an order one quantity in the units kPa. So here we present a 2D Log-Elastographic inverse algorithm that: (1) simultaneously reconstructs the shear modulus, μ, and p, which together satisfy a first order partial differential equation system, with the goal of imaging μ; (2) controls potential exponential growth in the numerical error; and (3) reliably reconstructs the quantity p in the inverse algorithm as compared to the same quantity computed with a forward algorithm. This work generalizes the Log-Elastographic algorithm in [20] which uses one displacement component, is derived assuming the component satisfies the wave equation, and is tested on synthetic data computed with the wave equation model. The 2D Log-Elastographic algorithm is tested on 2D synthetic data and 2Din-vivo data from Mayo Clinic. We also exhibit examples to show that the 2D Log-Elastographic algorithm improves the quality of the recovered images as compared to the Log-Elastographic and Direct Inversion algorithms. PMID:21822349

  14. Pokemon and MEF2D co-operationally promote invasion of hepatocellular carcinoma.

    PubMed

    Hong, Xin; Hong, Xing-Yu; Li, Tao; He, Cheng-Yan

    2015-12-01

    Hepatocellular carcinoma (HCC) is one of the most deadly human malignancy, and frequent invasion and metastasis is closely associated with its poor prognosis. However, the molecular mechanism underlying HCC invasion is still not completely elucidated. Pokemon is a well-established oncogene for HCC growth, but its contribution to HCC invasion has not been studied yet. In this paper, Pokemon was found to be overexpressed in MHCC-97H HCC cell line, which possesses higher invasiveness. Downregulation of Pokemon abolished the invasion of MHCC-97H HCC cell lines. Pokemon overexpression was able to enhance the invasion of MHCC-97L cells with lower invasiveness. MEF2D, an oncogene promoting the invasion of HCC cells, was further detected to be upregulated and downregulated when Pokemon was overexpressed and silenced, respectively. Online database analysis indicated that one Pokemon recognition site was located within the promoter of MEF2D. Chromatin co-precipitation, luciferase, and qPCR assays all proved that Pokemon can promote the expression of MEF2D in HCC cells. Restoration of MEF2D expression can prevent the impaired invasion of HCC cells with Pokemon silencing, while suppression of MEF2D abolished the effect of Pokemon overexpression on HCC invasion. More interestingly, MEF2D was also found to increase the transcription of Pokemon by binding myocyte enhancer factor 2 (MEF2) sites within its promoter region, implying an auto-regulatory circuit consisting of these two oncogenes that can promote HCC invasion. Our findings can contribute to the understanding of molecular mechanism underlying HCC invasion, and provided evidence that targeting this molecular loop may be a promising strategy for anti-invasion therapy. PMID:26164003

  15. Wall surface temperature calculation in the SolEdge2D-EIRENE transport code

    NASA Astrophysics Data System (ADS)

    Denis, J.; Pégourié, B.; Bucalossi, J.; Bufferand, H.; Ciraolo, G.; Gardarein, J.-L.; Gaspar, J.; Grisolia, C.; Hodille, E.; Missirlian, M.; Serre, E.; Tamain, P.

    2016-02-01

    A thermal wall model is developed for the SolEdge2D-EIRENE edge transport code for calculating the surface temperature of the actively-cooled vessel components in interaction with the plasma. This is a first step towards a self-consistent evaluation of the recycling of particles, which depends on the wall surface temperature. The proposed thermal model is built to match both steady-state temperature and time constant of actively-cooled plasma facing components. A benchmark between this model and the Finite Element Modelling code CAST3M is performed in the case of an ITER-like monoblock. An example of application is presented for a SolEdge2D-EIRENE simulation of a medium-power discharge in the WEST tokamak, showing the steady-state wall temperature distribution and the temperature cycling due to an imposed Edge Localised Mode-like event.

  16. LBQ2D, Extending the Line Broadened Quasilinear Model to TAE-EP Interaction

    NASA Astrophysics Data System (ADS)

    Ghantous, Katy; Gorelenkov, Nikolai; Berk, Herbert

    2012-10-01

    The line broadened quasilinear model was proposed and tested on the one dimensional electrostatic case of the bump on tailfootnotetextH.L Berk, B. Breizman and J. Fitzpatrick, Nucl. Fusion, 35:1661, 1995 to study the wave particle interaction. In conventional quasilinear theory, the sea of overlapping modes evolve with time as the particle distribution function self consistently undergo diffusion in phase space. The line broadened quasilinear model is an extension to the conventional theory in a way that allows treatment of isolated modes as well as overlapping modes by broadening the resonant line in phase space. This makes it possible to treat the evolution of modes self consistently from onset to saturation in either case. We describe here the model denoted by LBQ2D which is an extension of the proposed one dimensional line broadened quasilinear model to the case of TAEs interacting with energetic particles in two dimensional phase space, energy as well as canonical angular momentum. We study the saturation of isolated modes in various regimes and present the analytical derivation and numerical results. Finally, we present, using ITER parameters, the case where multiple modes overlap and describe the techniques used for the numerical treatment.

  17. Recent developments in 2D layered inorganic nanomaterials for sensing

    NASA Astrophysics Data System (ADS)

    Kannan, Padmanathan Karthick; Late, Dattatray J.; Morgan, Hywel; Rout, Chandra Sekhar

    2015-08-01

    Two dimensional layered inorganic nanomaterials (2D-LINs) have recently attracted huge interest because of their unique thickness dependent physical and chemical properties and potential technological applications. The properties of these layered materials can be tuned via both physical and chemical processes. Some 2D layered inorganic nanomaterials like MoS2, WS2 and SnS2 have been recently developed and employed in various applications, including new sensors because of their layer-dependent electrical properties. This article presents a comprehensive overview of recent developments in the application of 2D layered inorganic nanomaterials as sensors. Some of the salient features of 2D materials for different sensing applications are discussed, including gas sensing, electrochemical sensing, SERS and biosensing, SERS sensing and photodetection. The working principles of the sensors are also discussed together with examples.

  18. 2. D Street facade and rear (east) blank wall of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. D Street facade and rear (east) blank wall of parking garage. Farther east is 408 8th Street (National Art And Frame Company). - PMI Parking Garage, 403-407 Ninth Street, Northwest, Washington, District of Columbia, DC

  19. Collective excitations in 2D hard-disc fluid.

    PubMed

    Huerta, Adrian; Bryk, Taras; Trokhymchuk, Andrij

    2015-07-01

    Collective dynamics of a two-dimensional (2D) hard-disc fluid was studied by molecular dynamics simulations in the range of packing fractions that covers states up to the freezing. Some striking features concerning collective excitations in this system were observed. In particular, the short-wavelength shear waves while being absent at low packing fractions were observed in the range of high packing fractions, just before the freezing transition in a 2D hard-disc fluid. In contrast, the so-called "positive sound dispersion" typically observed in dense Lennard-Jones-like fluids, was not detected for the 2D hard-disc fluid. The ratio of specific heats in the 2D hard-disc fluid shows a monotonic increase with density approaching the freezing, resembling in this way the similar behavior in the vicinity of the Widom line in the case of supercritical fluids. PMID:25595625

  20. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices. PMID:26839956

  1. Technical Review of the UNET2D Hydraulic Model

    SciTech Connect

    Perkins, William A.; Richmond, Marshall C.

    2009-05-18

    The Kansas City District of the US Army Corps of Engineers is engaged in a broad range of river management projects that require knowledge of spatially-varied hydraulic conditions such as velocities and water surface elevations. This information is needed to design new structures, improve existing operations, and assess aquatic habitat. Two-dimensional (2D) depth-averaged numerical hydraulic models are a common tool that can be used to provide velocity and depth information. Kansas City District is currently using a specific 2D model, UNET2D, that has been developed to meet the needs of their river engineering applications. This report documents a tech- nical review of UNET2D.

  2. Chemical vapour deposition: Transition metal carbides go 2D

    NASA Astrophysics Data System (ADS)

    Gogotsi, Yury

    2015-11-01

    The unique properties of 2D materials, such as graphene or transition metal dichalcogenides, have been attracting much attention in the past decade. Now, metallically conductive and even superconducting transition metal carbides are entering the game.

  3. Dominant 2D magnetic turbulence in the solar wind

    NASA Technical Reports Server (NTRS)

    Bieber, John W.; Wanner, Wolfgang; Matthaeus, William H.

    1995-01-01

    There have been recent suggestions that solar wind magnetic turbulence may be a composite of slab geometry (wavevector aligned with the mean magnetic field) and 2D geometry (wavevectors perpendicular to the mean field). We report results of two new tests of this hypothesis using Helios measurements of inertial ranged magnetic spectra in the solar wind. The first test is based upon a characteristic difference between perpendicular and parallel reduced power spectra which is expected for the 2D component but not for the slab component. The second test examines the dependence of power spectrum density upon the magnetic field angle (i.e., the angle between the mean magnetic field and the radial direction), a relationship which is expected to be in opposite directions for the slab and 2D components. Both tests support the presence of a dominant (approximately 85 percent by energy) 2D component in solar wind magnetic turbulence.

  4. Dominant 2D magnetic turbulence in the solar wind

    SciTech Connect

    Bieber, John W.; Wanner, Wolfgang; Matthaeus, William H.

    1996-07-20

    There have been recent suggestions that solar wind magnetic turbulence may be a composite of slab geometry (wavevectors aligned with the mean magnetic field) and 2D geometry (wavevectors perpendicular to the mean field). We report results of two new tests of this hypothesis using Helios measurements of mid-inertial range magnetic spectra in the solar wind. The first test is based upon a characteristic difference between reduced magnetic power spectra in the two different directions perpendicular to the mean field. Such a difference is expected for 2D geometry but not for slab geometry. The second test examines the dependence of power spectrum density upon the magnetic field angle (i.e., the angle between the mean magnetic field and the radial direction), a relationship which is expected to be in opposite directions for the slab and 2D components. Both tests support the presence of a dominant ({approx}85% by energy) 2D component in solar wind magnetic turbulence.

  5. Efficient framework for deformable 2D-3D registration

    NASA Astrophysics Data System (ADS)

    Fluck, Oliver; Aharon, Shmuel; Khamene, Ali

    2008-03-01

    Using 2D-3D registration it is possible to extract the body transformation between the coordinate systems of X-ray and volumetric CT images. Our initial motivation is the improvement of accuracy of external beam radiation therapy, an effective method for treating cancer, where CT data play a central role in radiation treatment planning. Rigid body transformation is used to compute the correct patient setup. The drawback of such approaches is that the rigidity assumption on the imaged object is not valid for most of the patient cases, mainly due to respiratory motion. In the present work, we address this limitation by proposing a flexible framework for deformable 2D-3D registration consisting of a learning phase incorporating 4D CT data sets and hardware accelerated free form DRR generation, 2D motion computation, and 2D-3D back projection.

  6. Computational Design of 2D materials for Energy Applications

    NASA Astrophysics Data System (ADS)

    Sun, Qiang

    2015-03-01

    Since the successful synthesis of graphene, tremendous efforts have been devoted to two-dimensional monolayers such as boron nitride (BN), silicene and MoS2. These 2D materials exhibit a large variety of physical and chemical properties with unprecedented applications. Here we report our recent studies of computational design of 2D materials for fuel cell applications which include hydrogen storage, CO2 capture, CO conversion and O2 reduction.

  7. Generating a 2D Representation of a Complex Data Structure

    NASA Technical Reports Server (NTRS)

    James, Mark

    2006-01-01

    A computer program, designed to assist in the development and debugging of other software, generates a two-dimensional (2D) representation of a possibly complex n-dimensional (where n is an integer >2) data structure or abstract rank-n object in that other software. The nature of the 2D representation is such that it can be displayed on a non-graphical output device and distributed by non-graphical means.

  8. Phylogenetic tree construction based on 2D graphical representation

    NASA Astrophysics Data System (ADS)

    Liao, Bo; Shan, Xinzhou; Zhu, Wen; Li, Renfa

    2006-04-01

    A new approach based on the two-dimensional (2D) graphical representation of the whole genome sequence [Bo Liao, Chem. Phys. Lett., 401(2005) 196.] is proposed to analyze the phylogenetic relationships of genomes. The evolutionary distances are obtained through measuring the differences among the 2D curves. The fuzzy theory is used to construct phylogenetic tree. The phylogenetic relationships of H5N1 avian influenza virus illustrate the utility of our approach.

  9. Miga Aero Actuator and 2D Machined Mechanical Binary Latch

    NASA Technical Reports Server (NTRS)

    Gummin, Mark A.

    2013-01-01

    Shape memory alloy (SMA) actuators provide the highest force-to-weight ratio of any known actuator. They can be designed for a wide variety of form factors from flat, thin packages, to form-matching packages for existing actuators. SMA actuators can be operated many thousands of times, so that ground testing is possible. Actuation speed can be accurately controlled from milliseconds to position and hold, and even electronic velocity-profile control is possible. SMA actuators provide a high degree of operational flexibility, and are truly smart actuators capable of being accurately controlled by onboard microprocessors across a wide range of voltages. The Miga Aero actuator is a SMA actuator designed specifically for spaceflight applications. Providing 13 mm of stroke with either 20- or 40-N output force in two different models, the Aero actuator is made from low-outgassing PEEK (polyether ether ketone) plastic, stainless steel, and nickel-titanium SMA wires. The modular actuator weighs less than 28 grams. The dorsal output attachment allows the Aero to be used in either PUSH or PULL modes by inverting the mounting orientation. The SPA1 actuator utilizes commercially available SMA actuator wire to provide 3/8-in. (approx. =.1 cm) of stroke at a force of over 28 lb (approx. = .125 N). The force is provided by a unique packaging of the single SMA wire that provides the output force of four SMA wires mechanically in parallel. The output load is shared by allowing the SMA wire to slip around the output attachment end to adjust or balance the load, preventing any individual wire segment from experiencing high loads during actuation. A built-in end limit switch prevents overheating of the SMA element following actuation when used in conjunction with the Miga Analog Driver [a simple MOSFET (metal oxide semiconductor field-effect transistor) switching circuit]. A simple 2D machined mechanical binary latch has been developed to complement the capabilities of SMA wire

  10. Simulating MEMS Chevron Actuator for Strain Engineering 2D Materials

    NASA Astrophysics Data System (ADS)

    Vutukuru, Mounika; Christopher, Jason; Bishop, David; Swan, Anna

    2D materials pose an exciting paradigm shift in the world of electronics. These crystalline materials have demonstrated high electric and thermal conductivities and tensile strength, showing great potential as the new building blocks of basic electronic circuits. However, strain engineering 2D materials for novel devices remains a difficult experimental feat. We propose the integration of 2D materials with MEMS devices to investigate the strain dependence on material properties such as electrical and thermal conductivity, refractive index, mechanical elasticity, and band gap. MEMS Chevron actuators, provides the most accessible framework to study strain in 2D materials due to their high output force displacements for low input power. Here, we simulate Chevron actuators on COMSOL to optimize actuator design parameters and accurately capture the behavior of the devices while under the external force of a 2D material. Through stationary state analysis, we analyze the response of the device through IV characteristics, displacement and temperature curves. We conclude that the simulation precisely models the real-world device through experimental confirmation, proving that the integration of 2D materials with MEMS is a viable option for constructing novel strain engineered devices. The authors acknowledge support from NSF DMR1411008.

  11. Suramin blocks interaction between human FGF1 and FGFR2 D2 domain and reduces downstream signaling activity.

    PubMed

    Wu, Zong-Sian; Liu, Che Fu; Fu, Brian; Chou, Ruey-Hwang; Yu, Chin

    2016-09-01

    The extracellular portion of the human fibroblast growth factor receptor2 D2 domain (FGFR2 D2) interacts with human fibroblast growth factor 1 (hFGF1) to activate a downstream signaling cascade that ultimately affects mitosis and differentiation. Suramin is an antiparasiticdrug and a potent inhibitor of FGF-induced angiogenesis. Suramin has been shown to bind to hFGF1, and might block the interaction between hFGF1 and FGFR2 D2. Here, we titrated hFGF1 with FGFR2 D2 and suramin to elucidate their interactions using the detection of NMR. The docking results of both hFGF1-FGFR2 D2 domain and hFGF1-suramin complex were superimposed. The results indicate that suramin blocks the interaction between hFGF1 and FGFR2 D2. We used the PyMOL software to show the hydrophobic interaction of hFGF1-suramin. In addition, we used a Water-soluble Tetrazolium salts assay (WST1) to assess hFGF1 bioactivity. The results will be useful for the development of new antimitogenic activity drugs. PMID:27387234

  12. 2 D patterns of soil gas diffusivity , soil respiration, and methane oxidation in a soil profile

    NASA Astrophysics Data System (ADS)

    Maier, Martin; Schack-Kirchner, Helmer; Lang, Friederike

    2015-04-01

    The apparent gas diffusion coefficient in soil (DS) is an important parameter describing soil aeration, which makes it a key parameter for root growth and gas production and consumption. Horizontal homogeneity in soil profiles is assumed in most studies for soil properties - including DS. This assumption, however, is not valid, even in apparently homogeneous soils, as we know from studies using destructive sampling methods. Using destructive methods may allow catching a glimpse, but a large uncertainty remains, since locations between the sampling positions cannot be analyzed, and measurements cannot be repeated. We developed a new method to determine in situ the apparent soil gas diffusion coefficient in order to examine 2 D pattern of DS and methane oxidation in a soil profile. Different tracer gases (SF6, CF4, C2H6) were injected continuously into the subsoil and measured at several locations in the soil profile. These data allow for modelling inversely the 2 D patterns of DS using Finite Element Modeling. The 2D DS patterns were then combined with naturally occurring CH4 and CO2 concentrations sampled at the same locations to derive the 2D pattern of soil respiration and methane oxidation in the soil profile. We show that methane oxidation and soil respiration zones shift within the soil profile while the gas fluxes at the surface remain rather stable during a the 3 week campaign.

  13. Radiometer uncertainty equation research of 2D planar scanning PMMW imaging system

    NASA Astrophysics Data System (ADS)

    Hu, Taiyang; Xu, Jianzhong; Xiao, Zelong

    2009-07-01

    With advances in millimeter-wave technology, passive millimeter-wave (PMMW) imaging technology has received considerable concerns, and it has established itself in a wide range of military and civil practical applications, such as in the areas of remote sensing, blind landing, precision guidance and security inspection. Both the high transparency of clothing at millimeter wavelengths and the spatial resolution required to generate adequate images combine to make imaging at millimeter wavelengths a natural approach of screening people for concealed contraband detection. And at the same time, the passive operation mode does not present a safety hazard to the person who is under inspection. Based on the description to the design and engineering implementation of a W-band two-dimensional (2D) planar scanning imaging system, a series of scanning methods utilized in PMMW imaging are generally compared and analyzed, followed by a discussion on the operational principle of the mode of 2D planar scanning particularly. Furthermore, it is found that the traditional radiometer uncertainty equation, which is derived from a moving platform, does not hold under this 2D planar scanning mode due to the fact that there is no absolute connection between the scanning rates in horizontal direction and vertical direction. Consequently, an improved radiometer uncertainty equation is carried out in this paper, by means of taking the total time spent on scanning and imaging into consideration, with the purpose of solving the problem mentioned above. In addition, the related factors which affect the quality of radiometric images are further investigated under the improved radiometer uncertainty equation, and ultimately some original results are presented and analyzed to demonstrate the significance and validity of this new methodology.

  14. A droplet-to-digital (D2D) microfluidic device for single cell assays.

    PubMed

    Shih, Steve C C; Gach, Philip C; Sustarich, Jess; Simmons, Blake A; Adams, Paul D; Singh, Seema; Singh, Anup K

    2015-01-01

    We have developed a new hybrid droplet-to-digital microfluidic platform (D2D) that integrates droplet-in-channel microfluidics with digital microfluidics (DMF) for performing multi-step assays. This D2D platform combines the strengths of the two formats-droplets-in-channel for facile generation of droplets containing single cells, and DMF for on-demand manipulation of droplets including control of different droplet volumes (pL-μL), creation of a dilution series of ionic liquid (IL), and parallel single cell culturing and analysis for IL toxicity screening. This D2D device also allows for automated analysis that includes a feedback-controlled system for merging and splitting of droplets to add reagents, an integrated Peltier element for parallel cell culture at optimum temperature, and an impedance sensing mechanism to control the flow rate for droplet generation and preventing droplet evaporation. Droplet-in-channel is well-suited for encapsulation of single cells as it allows the careful manipulation of flow rates of aqueous phase containing cells and oil to optimize encapsulation. Once single cell containing droplets are generated, they are transferred to a DMF chip via a capillary where they are merged with droplets containing IL and cultured at 30 °C. The DMF chip, in addition to permitting cell culture and reagent (ionic liquid/salt) addition, also allows recovery of individual droplets for off-chip analysis such as further culturing and measurement of ethanol production. The D2D chip was used to evaluate the effect of IL/salt type (four types: NaOAc, NaCl, [C2mim] [OAc], [C2mim] [Cl]) and concentration (four concentrations: 0, 37.5, 75, 150 mM) on the growth kinetics and ethanol production of yeast and as expected, increasing IL concentration led to lower biomass and ethanol production. Specifically, [C2mim] [OAc] had inhibitory effects on yeast growth at concentrations 75 and 150 mM and significantly reduced their ethanol production compared to cells grown

  15. Novel and simple route to fabricate 2D ordered gold nanobowl arrays based on 3D colloidal crystals.

    PubMed

    Rao, Yanying; Tao, Qin; An, Ming; Rong, Chunhui; Dong, Jian; Dai, Yurong; Qian, Weiping

    2011-11-01

    In this study, we present a new method to fabricate large-area two-dimensionally (2D) ordered gold nanobowl arrays based on 3D colloidal crystals by wet chemosynthesis, which combines the advantages of a very simple preparation and an applicability to "real" nanomaterials. By combination of in situ growth of gold nanoshell (GNSs) arrays based on three-dimensional (3D) colloidal silica crystals, a monolayer ordered reversed GNS array (2D ordered GNS array) was conveniently manufactured by an acrylic ester modified biaxial oriented polypropylene (BOPP). 2D ordered gold nanobowl array with adjustable periodic holes, good stability, reproducibility, and repeatability could be obtained when the silica core was etched by HF solution. The surface-enhanced Raman scattering (SERS) enhancement factor (EF) of this 2D ordered gold nanobowl array could reach 1.27 × 10(7), which shows high SERS enhancing activity and can be used as a universal SERS substrate. PMID:21932785

  16. In vitro effects of 1α,25(OH)2D3-glycosides from Solbone A (Solanum glaucophyllum leaves extract; Herbonis AG) compared to synthetic 1α,25(OH)2D3 on myogenesis.

    PubMed

    Gili, Valeria; Pardo, Verónica Gonzalez; Ronda, Ana C; De Genaro, Pablo; Bachmann, Heini; Boland, Ricardo; de Boland, Ana Russo

    2016-05-01

    The presence of glycoside derivatives of 1α,25(OH)2D3 endows plants to gradual release of the free bioactive form of 1α,25(OH)2D3 from its glycoconjugates by endogenous animal tissue glycosidases. This results in increased half-life of the hormone in blood when purified plant fractions are administered for therapeutic purposes. In this work, we evaluated the role 1α,25(OH)2D3-glycosides enriched natural product (Solbone A) from Solanum glaucophyllum leaf extract compared with synthetic 1α,25(OH)2D3 on myogenic differentiation in C2C12 myoblasts. For these, differentiation markers and myogenic parameters were studied in C2C12 myoblasts. Results showed that Solbone A, likewise the synthetic hormone, increased creatine kinase activity at day 2 after differentiation induction (60%, p<0.05). Solbone A and synthetic 1α,25(OH)2D3 increased vitamin D3 receptor protein expression at 10nM (50% and 30%, respectively) and the transcription factor myogenin (80%, p<0.05). However, tropomyosin expression was not affected by both compounds. In addition, myosin heavy chain (MHC) protein expression was increased 30% at day 2 of differentiation. Solbone A or synthetic 1α,25(OH)2D3 had no effects on myogenin nor MHC cell localization. Cellular mass increased with myogenesis progression, being Solbone A more effective than synthetic 1α,25(OH)2D3. Finally, Solbone A, as well as synthetic 1α,25(OH)2D3, augmented the index fusion of cultured muscle fibers. In conclusion, these results demonstrated that Solbone A exhibit at least equal or greater effects on early myoblast differentiation as synthetic hormone, suggesting that plant glycosides could be an effective, accessible and cheaper substitute for synthetic 1α,25(OH)2D3 to promote muscle growth. PMID:26968127

  17. CC2D2A mutations in Meckel and Joubert syndromes indicate a genotype-phenotype correlation

    PubMed Central

    Mougou-Zerelli, Soumaya; Thomas, Sophie; Szenker, Emmanuelle; Audollent, Sophie; Elkhartoufi, Nadia; Babarit, Candice; Romano, Stéphane; Salomon, Rémi; Amiel, Jeanne; Esculpavit, Chantal; Gonzales, Marie; Escudier, Estelle; Leheup, Bruno; Loget, Philippe; Odent, Sylvie; Roume, Joëlle; Gérard, Marion; Delezoide, Anne-Lise; Khung, Suonavy; Patrier, Sophie; Cordier, Marie-Pierre; Bouvier, Raymonde; Martinovic, Jéléna; Gubler, Marie-Claire; Boddaert, Nathalie; Munnich, Arnold; Encha-Razavi, Férechté; Valente, Enza Maria; Saad, Ali; Saunier, Sophie; Vekemans, Michel; Attié-Bitach, Tania

    2009-01-01

    The Meckel syndrome (MKS) is a lethal fetal disorder characterized by diffuse renal cystic dysplasia, polydactyly, a brain malformation that is usually occipital encephalocele and/or vermian agenesis, with intrahepatic biliary duct proliferation. Joubert syndrome (JBS) is a viable neurological disorder with a characteristic “molar tooth sign” (MTS) on axial images reflecting cerebellar vermian hypoplasia/dysplasia. Both conditions are classified as ciliopathies with an autosomal recessive mode of inheritance. Allelism of MS and JBS has been reported for TMEM67/MKS3, CEP290/MKS4, and RPGRIP1L/MKS5. Recently, one homozygous splice mutation with a founder effect was reported in the CC2D2A gene in Finnish fetuses with MKS, defining the 6th locus for MKS. Shortly thereafter, CC2D2A mutations were reported in JBS also. The analysis of the CC2D2A gene in our series of MKS fetuses, identified 14 novel truncating mutations in 11 cases. These results confirm the involvement of CC2D2A in MKS and reveal a major contribution of CC2D2A to the disease. We also identified three missense CC2D2A mutations in two JBS cases. Therefore and in accordance with the data reported regarding RPGRIP1L, our results indicate phenotype-genotype correlations, as missense and presumably hypomorphic mutations lead to JBS while all null alleles lead to MKS. PMID:19777577

  18. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator

    PubMed Central

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben

    2013-01-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability. PMID:24307756

  19. Development and Evaluation of 2-D and 3-D Exocentric Synthetic Vision Navigation Display Concepts for Commercial Aircraft

    NASA Technical Reports Server (NTRS)

    Prinzel, Lawrence J., III; Kramer, Lynda J.; Arthur, J. J., III; Bailey, Randall E.; Sweeters, Jason L.

    2005-01-01

    NASA's Synthetic Vision Systems (SVS) project is developing technologies with practical applications that will help to eliminate low visibility conditions as a causal factor to civil aircraft accidents while replicating the operational benefits of clear day flight operations, regardless of the actual outside visibility condition. The paper describes experimental evaluation of a multi-mode 3-D exocentric synthetic vision navigation display concept for commercial aircraft. Experimental results evinced the situation awareness benefits of 2-D and 3-D exocentric synthetic vision displays over traditional 2-D co-planar navigation and vertical situation displays. Conclusions and future research directions are discussed.

  20. 2D and 3D X-Ray Structural Microscopy Using Submicron-Resolution Laue Microdiffraction

    SciTech Connect

    Budai, John D.; Yang, Wenge; Larson, Bennett C.; Tischler, Jonathan Z.; Liu, Wenjun; Ice, Gene E.

    2010-11-10

    We have developed a scanning, polychromatic x-ray microscopy technique with submicron spatial resolution at the Advanced Photon Source. In this technique, white undulator radiation is focused to submicron diameter using elliptical mirrors. Laue diffraction patterns scattered from the sample are collected with an area detector and then analyzed to obtain the local crystal structure, lattice orientation, and strain tensor. These new microdiffraction capabilities have enabled both 2D and 3D structural studies of materials on mesoscopic length-scales of tenths-to-hundreds of microns. For thin samples such as deposited films, 2D structural maps are obtained by step-scanning the area of interest. For example, 2D x-ray microscopy has been applied in studies of the epitaxial growth of oxide films. For bulk samples, a 3D differential-aperture x-ray microscopy technique has been developed that yields the full diffraction information from each submicron volume element. The capabilities of 3D x-ray microscopy are demonstrated here with measurements of grain orientations and grain boundary motion in polycrystalline aluminum during 3D thermal grain growth. X-ray microscopy provides the needed, direct link between the experimentally measured 3D microstructural evolution and the results of theory and modeling of materials processes on mesoscopic length scales.