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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. Residual lens effects in 2D mode of auto-stereoscopic lenticular-based switchable 2D/3D displays

    NASA Astrophysics Data System (ADS)

    Sluijter, M.; IJzerman, W. L.; de Boer, D. K. G.; de Zwart, S. T.

    2006-04-01

    We discuss residual lens effects in multi-view switchable auto-stereoscopic lenticular-based 2D/3D displays. With the introduction of a switchable lenticular, it is possible to switch between a 2D mode and a 3D mode. The 2D mode displays conventional content, whereas the 3D mode provides the sensation of depth to the viewer. The uniformity of a display in the 2D mode is quantified by the quality parameter modulation depth. In order to reduce the modulation depth in the 2D mode, birefringent lens plates are investigated analytically and numerically, by ray tracing. We can conclude that the modulation depth in the 2D mode can be substantially decreased by using birefringent lens plates with a perfect index match between lens material and lens plate. Birefringent lens plates do not disturb the 3D performance of a switchable 2D/3D display.

  3. Graphene band structure and its 2D Raman mode

    NASA Astrophysics Data System (ADS)

    Narula, Rohit; Reich, Stephanie

    2014-08-01

    High-precision simulations are used to generate the 2D Raman mode of graphene under a range of screening conditions and laser energies EL. We reproduce the decreasing trend of the 2D mode FWHM vs EL and the nearly linearly increasing dispersion ∂ω2D/∂EL seen experimentally in freestanding (unscreened) graphene, and propose relations between these experimentally accessible quantities and the local, two-dimensional gradients |∇ | of the electronic and TO phonon bands. In light of state-of-the-art electronic structure calculations that acutely treat the long-range e-e interactions of isolated graphene and its experimentally observed 2D Raman mode, our calculations determine a 40% greater slope of the TO phonons about K than given by explicit phonon measurements performed in graphite or GW phonon calculations in graphene. We also deduce the variation of the broadening energy γ [EL] for freestanding graphene and find a nominal value γ ˜140 meV, showing a gradually increasing trend for the range of frequencies available experimentally.

  4. Extreme Growth of Enstrophy on 2D Bounded Domains

    NASA Astrophysics Data System (ADS)

    Protas, Bartosz; Sliwiak, Adam

    2016-11-01

    We study the vortex states responsible for the largest instantaneous growth of enstrophy possible in viscous incompressible flow on 2D bounded domain. The goal is to compare these results with estimates obtained using mathematical analysis. This problem is closely related to analogous questions recently considered in the periodic setting on 1D, 2D and 3D domains. In addition to systematically characterizing the most extreme behavior, these problems are also closely related to the open question of the finite-time singularity formation in the 3D Navier-Stokes system. We demonstrate how such extreme vortex states can be found as solutions of constrained variational optimization problems which in the limit of small enstrophy reduce to eigenvalue problems. Computational results will be presented for circular and square domains emphasizing the effect of geometric singularities (corners of the domain) on the structure of the extreme vortex states. Supported by an NSERC (Canada) Discovery Grant.

  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.

  6. Improved structural quality of AlN grown on sapphire by 3D/2D alternation growth

    NASA Astrophysics Data System (ADS)

    Guo, Yanmin; Fang, Yulong; Yin, Jiayun; Zhang, Zhirong; Wang, Bo; Li, Jia; Lu, Weili; Feng, Zhihong

    2017-04-01

    Three dimensional (3D) and two dimensional (2D) alternation growth was used to grow AlN epitaxial layers on sapphire substrates. AlN samples grown using this technique have higher crystalline quality and lower dislocation density than samples grown using only 3D or 2D growth modes as witnessed by the high-resolution X-ray diffraction. Smooth atomic terraces with root mean square roughness of 0.107 nm were observed using atomic force microscopy (AFM) when the 3D and 2D AlN were 75 nm and 425 nm, respectively. This sample possesses single crystallographic orientation along the c-axis identified by Raman spectroscopy. Furthermore, the 3D/2D alternating growth mode modulates internal stress in AlN epitaxial layer by adjusting 2D AlN thickness, and the mechanism was studied in detail.

  7. 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.

  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

    2016-09-01

    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.

  9. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

  11. Enhanced detection limit by dark mode perturbation in 2D photonic crystal slab refractive index sensors.

    PubMed

    Nicolaou, Costa; Lau, Wah Tung; Gad, Raanan; Akhavan, Hooman; Schilling, Ryan; Levi, Ofer

    2013-12-16

    We demonstrate for the first time a 300nm thick, 300μm × 300μm 2D dielectric photonic crystal slab membrane with a quality factor of 10,600 by coupling light to slightly perturbed dark modes through alternating nano-hole sizes. The newly created fundamental guided resonances greatly reduce nano-fabrication accuracy requirements. Moreover, we created a new layer architecture resulting in electric field enhancement at the interface between the slab and sensing regions, and spectral sensitivity of >800 nm/RIU, that is, >0.8 of the single-mode theoretical upper limit of spectral sensitivity.

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

    SciTech Connect

    Imbert-Gérard, Lise-Marie

    2015-12-15

    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.

  13. 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.

  14. Anharmonic vibrational modes of nucleic acid bases revealed by 2D IR spectroscopy.

    PubMed

    Peng, Chunte Sam; Jones, Kevin C; Tokmakoff, Andrei

    2011-10-05

    Polarization-dependent two-dimensional infrared (2D IR) spectra of the purine and pyrimadine base vibrations of five nucleotide monophosphates (NMPs) were acquired in D(2)O at neutral pH in the frequency range 1500-1700 cm(-1). The distinctive cross-peaks between the ring deformations and carbonyl stretches of NMPs indicate that these vibrational modes are highly coupled, in contrast with the traditional peak assignment, which is based on a simple local mode picture such as C═O, C═N, and C═C double bond stretches. A model of multiple anharmonically coupled oscillators was employed to characterize the transition energies, vibrational anharmonicities and couplings, and transition dipole strengths and orientations. No simple or intuitive structural correlations are found to readily assign the spectral features, except in the case of guanine and cytosine, which contain a single local CO stretching mode. To help interpret the nature of these vibrational modes, we performed density functional theory (DFT) calculations and found that multiple ring vibrations are coupled and delocalized over the purine and pyrimidine rings. Generally, there is close correspondence between the experimental and computational results, provided that the DFT calculations include explicit waters solvating hydrogen-bonding sites. These results provide direct experimental evidence of the delocalized nature of the nucleotide base vibrations via a nonperturbative fashion and will serve as building blocks for constructing a structure-based model of DNA and RNA vibrational spectroscopy.

  15. 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.

  16. 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

  17. Epitaxial Growth of Ternary Topological Insulator Bi2 Te2 Se 2D Crystals on Mica.

    PubMed

    Liu, Yujing; Tang, Min; Meng, Mengmeng; Wang, Mingzhan; Wu, Jinxiong; Yin, Jianbo; Zhou, Yubing; Guo, Yunfan; Tan, Congwei; Dang, Wenhui; Huang, Shaoyun; Xu, H Q; Wang, Yong; Peng, Hailin

    2017-03-06

    Nanostructures of ternary topological insulator (TI) Bi2 Te2 Se are, in principle, advantageous to the manifestation of topologically nontrivial surface states, due to significantly enhanced surface-to-volume ratio compared with its bulk crystals counterparts. Herein, the synthesis of 2D Bi2 Te2 Se crystals on mica via the van der Waals epitaxy method is explored and systematically the growth behaviors during the synthesis process are investigated. Accordingly, 2D Bi2 Te2 Se crystals with domain size up to 50 µm large and thickness down to 2 nm are obtained. A pronounced weak antilocalization effect is clearly observed in the 2D Bi2 Te2 Se crystals at 2 K. The method for epitaxial growth of 2D ternary Bi2 Te2 Se crystals may inspire materials engineering toward enhanced manifestation of the subtle surface states of TIs and thereby facilitate their potential applications in next-generation spintronics.

  18. The immunoreceptor NKG2D promotes tumour growth in a model of hepatocellular carcinoma

    PubMed Central

    Sheppard, Sam; Guedes, Joana; Mroz, Anna; Zavitsanou, Anastasia-Maria; Kudo, Hiromi; Rothery, Stephen M.; Angelopoulos, Panagiotis; Goldin, Robert; Guerra, Nadia

    2017-01-01

    Inflammation is recognized as one of the drivers of cancer. Yet, the individual immune components that possess pro- and anti-tumorigenic functions in individual cancers remain largely unknown. NKG2D is a potent activating immunoreceptor that has emerged as an important player in inflammatory disorders besides its well-established function as tumour suppressor. Here, we provide genetic evidence of an unexpected tumour-promoting effect of NKG2D in a model of inflammation-driven liver cancer. Compared to NKG2D-deficient mice, NKG2D-sufficient mice display accelerated tumour growth associated with, an increased recruitment of memory CD8+T cells to the liver and exacerbated pro-inflammatory milieu. In addition, we show that NKG2D contributes to liver damage and consequent hepatocyte proliferation known to favour tumorigenesis. Thus, the NKG2D/NKG2D-ligand pathway provides an additional mechanism linking chronic inflammation to tumour development in hepatocellular carcinoma. Our findings expose the need to selectively target the types of cancer that could benefit from NKG2D-based immunotherapy. PMID:28128200

  19. Dynamical Analysis and Big Bang Bifurcations of 1D and 2D Gompertz's Growth Functions

    NASA Astrophysics Data System (ADS)

    Rocha, J. Leonel; Taha, Abdel-Kaddous; Fournier-Prunaret, D.

    In this paper, we study the dynamics and bifurcation properties of a three-parameter family of 1D Gompertz's growth functions, which are defined by the population size functions of the Gompertz logistic growth equation. The dynamical behavior is complex leading to a diversified bifurcation structure, leading to the big bang bifurcations of the so-called “box-within-a-box” fractal type. We provide and discuss sufficient conditions for the existence of these bifurcation cascades for 1D Gompertz's growth functions. Moreover, this work concerns the description of some bifurcation properties of a Hénon's map type embedding: a “continuous” embedding of 1D Gompertz's growth functions into a 2D diffeomorphism. More particularly, properties that characterize the big bang bifurcations are considered in relation with this coupling of two population size functions, varying the embedding parameter. The existence of communication areas of crossroad area type or swallowtails are identified for this 2D diffeomorphism.

  20. 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.

  1. 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.

  2. Bond and mode selectivity in the OH + NH2D reaction: a quasi-classical trajectory calculation.

    PubMed

    Monge-Palacios, M; Espinosa-Garcia, J

    2013-11-28

    A state-to-state dynamics study was performed to analyze the effects of vibrational excitation on the dynamics of the OH + NH2D gas-phase reaction, which are connected to issues such as bond and mode selectivity. This reaction can evolve along two channels: H-abstraction, H2O(ν) + NHD(ν); and D-abstraction, HOD(ν) + NH2(ν). Based on an analytical potential energy surface previously developed by our group, quasi-classical trajectory calculations and subsequent normal mode analysis were performed. While vibrational excitation of the NH-sym mode of NH2D slightly favours H-abstraction over the D-abstraction, vibrational excitation of the ND mode shows that there is no clear preference for the H- or D-abstraction. These results show that this reaction does not exhibit bond selectivity, suggesting a breakdown of the spectator model. For H-abstraction, vibrational excitation of the non-reactive ND mode is partially retained in the NHD product; and for D-abstraction, excitation of the non-reactive NH mode is also partially retained in the products, indicating that this reaction exhibits mode selectivity only partially. In sum, we rule out bond and mode selectivity for this reaction. All these results were interpreted on the basis of strong coupling between modes along the reaction path, a behaviour which seems to be more the general tendency than the exception in polyatomic reactions.

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

    DOE PAGES

    Mahjouri-Samani, Masoud; Tian, Mengkun; Wang, Kai; ...

    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

  4. 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.

  5. On extended analytic theory of 2D ballooning modes in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Abdoul, Peshwaz; Dickinson, David; Roach, Colin; Wilson, Howard

    2016-10-01

    We have extended the leading order ballooning theory which typically yields more unstable isolated mode (IM) that usually sit on the outboard mid-plane, to higher order where less unstable general mode (GM) sits at a different poloidal location. Our analytic theory has revealed that any poloidal shift of the mode with respect to the outboard mid-plane - arising from the effect of profile variations, for example - is always accompanied by an asymmetry of the radial eigenmode structure. Hence, GMs have radial asymmetry. Our theory can have important consequences, especially for calculations that invoke quasilinear theory to model intrinsic rotation arising from Reynolds stress. This is very important in ITER for which external torques are small. In such theories it is the radial asymmetry in the global GM mode which can generate a Reynolds stress that could in principle contribute to the poloidal flow during the low to high (L-H) mode transition in tokamaks. I am also an associate member at the York Plasma Institute, University of York and teaching at the Physics Department, University of Sulaimani, Kurdistan Region, Iraq.

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

    PubMed

    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.

  7. 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.

  8. 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.

  9. 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.

  10. EDGE2D-EIRENE modelling of near SOL E r: possible impact on the H-mode power threshold

    NASA Astrophysics Data System (ADS)

    Chankin, A. V.; Delabie, E.; Corrigan, G.; Harting, D.; Maggi, C. F.; Meyer, H.; Contributors, JET

    2017-04-01

    Recent EDGE2D-EIRENE simulations of JET plasmas showed a significant difference between radial electric field (E r) profiles across the separatrix in two divertor configurations, with the outer strike point on the horizontal target (HT) and vertical target (VT) (Chankin et al 2016 Nucl. Mater. Energy, doi: 10.1016/j.nme.2016.10.004). Under conditions (input power, plasma density) where the HT plasma went into the H-mode, a large positive E r spike in the near scrape-off layer (SOL) was seen in the code output, leading to a very large E × B shear across the separatrix over a narrow region of a fraction of a cm width. No such E r feature was obtained in the code solution for the VT configuration, where the H-mode power threshold was found to be twice as high as in the HT configuration. It was hypothesised that the large E × B shear across the separatrix in the HT configuration could be responsible for the turbulence suppression leading to an earlier (at lower input power) L–H transition compared to the VT configuration. In the present work these ideas are extended to cover some other experimental observations on the H-mode power threshold variation with parameters which typically are not included in the multi-machine H-mode power threshold scalings, namely: ion mass dependence (isotope H–D–T exchange), dependence on the ion ∇B drift direction, and dependence on the wall material composition (ITER-like wall versus carbon wall in JET). In all these cases EDGE2D-EIRENE modelling shows larger positive E r spikes in the near SOL under conditions where the H-mode power threshold is lower, at least in the HT configuration.

  11. Pharmacophore, QSAR, and binding mode studies of substrates of human cytochrome P450 2D6 (CYP2D6) using molecular docking and virtual mutations and an application to chinese herbal medicine screening.

    PubMed

    Mo, Sui-Lin; Liu, Wei-Feng; Li, Chun-Guang; Zhou, Zhi-Wei; Luo, Hai-Bin; Chew, Helen; Liang, Jun; Zhou, Shu-Feng

    2012-07-01

    The highly polymorphic human cytochrome P450 2D6 (CYP2D6) metabolizes about 25% of currently used drugs. In this study, we have explored the interaction of a large number of substrates (n = 120) with wild-type and mutated CYP2D6 by molecular docking using the CDOCKER module. Before we conducted the molecular docking and virtual mutations, the pharmacophore and QSAR models of CYP2D6 substrates were developed and validated. Finally, we explored the interaction of a traditional Chinese herbal formula, Fangjifuling decoction, with CYP2D6 by virtual screening. The optimized pharmacophore model derived from 20 substrates of CYP2D6 contained two hydrophobic features and one hydrogen bond acceptor feature, giving a relevance ratio of 76% when a validation set of substrates were tested. However, our QSAR models gave poor prediction of the binding affinity of substrates. Our docking study demonstrated that 117 out of 120 substrates could be docked into the active site of CYP2D6. Forty one out of 117 substrates (35.04%) formed hydrogen bonds with various active site residues of CYP2D6 and 53 (45.30%) substrates formed a strong π-π interaction with Phe120 (53/54), with only carvedilol showing π-π interaction with Phe483. The active site residues involving hydrogen bond formation with substrates included Leu213, Lys214, Glu216, Ser217, Gln244, Asp301, Ser304, Ala305, Phe483, and Phe484. Furthermore, the CDOCKER algorithm was further applied to study the impact of mutations of 28 active site residues (mostly non-conserved) of CYP2D6 on substrate binding modes using five probe substrates including bufuralol, debrisoquine, dextromethorphan, sparteine, and tramadol. All mutations of the residues examined altered the hydrogen bond formation and/or aromatic interactions, depending on the probe used in molecular docking. Apparent changes of the binding modes have been observed with the Glu216Asp and Asp301Glu mutants. Overall, 60 compounds out of 130 from Fangjifuling decoction

  12. 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.

  13. Polymorphic polytypic transition induced in crystals by interaction of spirals and 2D growth mechanisms

    NASA Astrophysics Data System (ADS)

    Aquilano, Dino; Veesler, Stéphane; Astier, Jean Pierre; Pastero, Linda

    2003-01-01

    The relationship between crystal polymorphism and polytypism can be revealed by surface patterns through the interlacing of the growth spirals. Simple high-symmetry structures as SiC, ZnS, CdI2 and more complex low-symmetry layered structures as n-paraffins, n-alcohols and micas are concerned with polymorphic-polytypic transition. In this paper, we will show for the first time, through in situ AFM observations and X-ray diffractometry, that a protein polymorph (P2 12 12 1α-amylase) locally changes, during growth, to a monoclinic P2 1 polytype, thanks to the screw dislocation activity. The interplay between spiral steps and 2D nuclei of the polytypes coexisting in the same crystalline individual allows to foresee the consequences on the crystal quality. The discussion is extended to other mineral and biological molecules and a new general rule is proposed to explain the interactions between surface patterns and the bulk crystal structure.

  14. Coupled leaky mode theory for light absorption in 2D, 1D, and 0D semiconductor nanostructures.

    PubMed

    Yu, Yiling; Cao, Linyou

    2012-06-18

    We present an intuitive, simple theoretical model, coupled leaky mode theory (CLMT), to analyze the light absorption of 2D, 1D, and 0D semiconductor nanostructures. This model correlates the light absorption of nanostructures to the optical coupling between incident light and leaky modes of the nanostructure. Unlike conventional methods such as Mie theory that requests specific physical features of nanostructures to evaluate the absorption, the CLMT model provides an unprecedented capability to analyze the absorption using eigen values of the leaky modes. Because the eigenvalue shows very mild dependence on the physical features of nanostructures, we can generally apply one set of eigenvalues calculated using a real, constant refractive index to calculations for the absorption of various nanostructures with different sizes, different materials, and wavelength-dependent complex refractive index. This CLMT model is general, simple, yet reasonably accurate, and offers new intuitive physical insights that the light absorption of nanostructures is governed by the coupling efficiency between incident light and leaky modes of the structure.

  15. Drift mode growth rates and associated transport

    SciTech Connect

    Redd, A.J.; Kritz, A.H.; Bateman, G.; Rewoldt, G.; Tang, W.M.

    1999-04-01

    Drift mode linear growth rates and quasilinear transport are investigated using the FULL kinetic stability code [Rewoldt {ital et al.}, Phys. Plasmas {bold 5}, 1815 (1998)] and a version of the Weiland transport model [Strand {ital et al.}, Nucl. Fusion {bold 38}, 545 (1998)]. It is shown that the drift mode growth rates (as well as the marginal stability temperature gradient) obtained using the FULL code are dependent on the accuracy of the equilibrium employed. In particular, when an approximate equilibrium model is utilized by the FULL code, the results can differ significantly from those obtained using a more accurate numerical equilibrium. Also investigated are the effects of including full electron physics. It is shown, using both the FULL code and the Weiland model, that the nonadiabatic (e.g., trapped) electron response produces a significant increase in the linear growth rate of the ion-temperature-gradient (ITG) driven branch of the drift instability. Other consequences of the nonadiabatic electron response include a reduction in the marginal temperature gradient for the onset of the ITG mode and an additional contribution to transport due to the excitation of the Trapped Electron Mode (TEM). Physical explanations are given for the sensitivity of the mode growth rates to the equilibrium and the nonadiabatic electron response. Finally, linear growth rates for the ITG mode computed using the FULL code are compared with growth rates obtained using the Weiland model. {copyright} {ital 1999 American Institute of Physics.}

  16. 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

  17. Photon-Assisted Resonant Tunneling and 2-D Plasmon Modes in Double Quantum Wells in Intense Terahertz Electric Fields

    NASA Astrophysics Data System (ADS)

    Peralta, X. G.; Allen, S. J.; Lin, S. Y.; Simmons, J. A.; Blount, M. A.; Baca, W. E.

    1998-03-01

    We explore photon-assisted resonant tunneling in double quantum well systems in intense terahertz electric fields that have separately- contacted wells. We have two goals in mind: 1) increase the basic understanding of photon assisted tunneling in semiconductors and 2) assess the potential of this structure as a detector. We can control the tunneling current by varying the electron density of each 2D electron gas or by changing the relative separation of the Fermi levels. This allows us to prepare the system in such a way that photons of the appropriate energy may induce resonant tunneling, which is monitored by a change in conductance. We also examine the possible enhancement of the resonant tunneling by resonant excitations of acoustic plasmon modes. This work is supported by ONR, the U. S. Dept. of Energy under Contract DE-AC04-94AL85000 and Consejo Nacional de Ciencia y Tecnología, México.

  18. Laser characterization of the unsteady 2-D ion flow field in a Hall thruster with breathing mode oscillations

    NASA Astrophysics Data System (ADS)

    Lucca Fabris, Andrea; Young, Christopher; MacDonald-Tenenbaum, Natalia; Hargus, William, Jr.; Cappelli, Mark

    2016-10-01

    Hall thrusters are a mature form of electric propulsion for spacecraft. One commonly observed low frequency (10-50 kHz) discharge current oscillation in these E × B devices is the breathing mode, linked to a propagating ionization front traversing the channel. The complex time histories of ion production and acceleration in the discharge channel and near-field plume lead to interesting dynamics and interactions in the central plasma jet and downstream plume regions. A time-resolved laser-induced fluorescence (LIF) diagnostic non-intrusively measures 2-D ion velocity and relative ion density throughout the plume of a commercial BHT-600 Hall thruster manufactured by Busek Co. Low velocity classes of ions observed in addition to the main accelerated population are linked to propellant ionization outside of the device. Effects of breathing mode dynamics are shown to persist far downstream where modulations in ion velocity and LIF intensity are correlated with discharge current oscillations. This work is sponsored by the U.S. Air Force Office of Scientific Research with Dr. M. Birkan as program manager. C.Y. acknowledges support from the DOE NSSA Stewardship Science Graduate Fellowship under contract DE-FC52-08NA28752.

  19. Evolution of 2D Visible and VUV Divertor Emission Profiles During DIII-D H-MODE Detachment Transitions

    NASA Astrophysics Data System (ADS)

    Fenstermacher, M. E.; Jalufka, N.; Meyer, W. H.; Nilson, D. G.; Gafert, J.

    1999-07-01

    The peak heat flux to divertor target surfaces (Pdiv) must be reduced, compared with present experimental levels, before a tokamak operating in the high confinement regime (H-mode) can be extrapolated to a reactor. Partially Detached Divertor (PDD) operation (1), in which deuterium gas is injected into an H-mode plasma, reduces Pdiv by factors of 3-5 in DIII-D. A key element in the physics model of PDD operation is that carbon radiation near the X-point dissipates the energy flowing in the scrape-off-layer (SOL) before it enters the divertor (2). This allows the divertor temperature to be low, density to be high and thereby reduces the heat flux and ion particle flux to the targets both by reduced recycling and increased recombination. Previous line integrated SPRED measurements (3) and computer simulations indicated that the 155 nm (Delta)n = 0 transition of C3+ was the main power radiator from carbon during PDD operation. This paper presents the first 2D profiles of 155 nm CIV emission in any tokamak divertor. The images were obtained on DIII-D with a new tangentially viewing VUV camera (4) and established image reconstruction techniques (5). The discharges were lower single null configurations with, I p = 1.75 MA, BT = 2.1 (Tau), q95 = 3.2, Pinj = 9 MW, (kappa) = 1.9 and the (nabla)B drift toward the lower divertor. After establishing an ELMing H-mode with neutral beam injection, deuterium gas was injected at 17 Pa m3/s (130 T (ell)/s) to increase the divertor density and produce a transition to PDD operation. A practical discharge scenario is given in Ref. (2).

  20. 2D protrusion but not motility predicts growth factor-induced cancer cell migration in 3D collagen.

    PubMed

    Meyer, Aaron S; Hughes-Alford, Shannon K; Kay, Jennifer E; Castillo, Amalchi; Wells, Alan; Gertler, Frank B; Lauffenburger, Douglas A

    2012-06-11

    Growth factor-induced migration is a critical step in the dissemination and metastasis of solid tumors. Although differences in properties characterizing cell migration on two-dimensional (2D) substrata versus within three-dimensional (3D) matrices have been noted for particular growth factor stimuli, the 2D approach remains in more common use as an efficient surrogate, especially for high-throughput experiments. We therefore were motivated to investigate which migration properties measured in various 2D assays might be reflective of 3D migratory behavioral responses. We used human triple-negative breast cancer lines stimulated by a panel of receptor tyrosine kinase ligands relevant to mammary carcinoma progression. Whereas 2D migration properties did not correlate well with 3D behavior across multiple growth factors, we found that increased membrane protrusion elicited by growth factor stimulation did relate robustly to enhanced 3D migration properties of the MDA-MB-231 and MDA-MB-157 lines. Interestingly, we observed this to be a more reliable relationship than cognate receptor expression or activation levels across these and two additional mammary tumor lines.

  1. Coherent phenomena in terahertz 2D plasmonic structures: strong coupling, plasmonic crystals, and induced transparency by coupling of localized modes

    NASA Astrophysics Data System (ADS)

    Dyer, Gregory C.; Aizin, Gregory R.; Allen, S. James; Grine, Albert D.; Bethke, Don; Reno, John L.; Shaner, Eric A.

    2014-05-01

    The device applications of plasmonic systems such as graphene and two dimensional electron gases (2DEGs) in III-V heterostructures include terahertz detectors, mixers, oscillators and modulators. These two dimensional (2D) plasmonic systems are not only well-suited for device integration, but also enable the broad tunability of underdamped plasma excitations via an applied electric field. We present demonstrations of the coherent coupling of multiple voltage tuned GaAs/AlGaAs 2D plasmonic resonators under terahertz irradiation. By utilizing a plasmonic homodyne mixing mechanism to downconvert the near field of plasma waves to a DC signal, we directly detect the spectrum of coupled plasmonic micro-resonator structures at cryogenic temperatures. The 2DEG in the studied devices can be interpreted as a plasmonic waveguide where multiple gate terminals control the 2DEG kinetic inductance. When the gate tuning of the 2DEG is spatially periodic, a one-dimensional finite plasmonic crystal forms. This results in a subwavelength structure, much like a metamaterial element, that nonetheless Bragg scatters plasma waves from a repeated crystal unit cell. A 50% in situ tuning of the plasmonic crystal band edges is observed. By introducing gate-controlled defects or simply terminating the lattice, localized states arise in the plasmonic crystal. Inherent asymmetries at the finite crystal boundaries produce an induced transparency-like phenomenon due to the coupling of defect modes and crystal surface states known as Tamm states. The demonstrated active control of coupled plasmonic resonators opens previously unexplored avenues for sensitive direct and heterodyne THz detection, planar metamaterials, and slow-light devices.

  2. New growth mode through decorated twin boundaries.

    PubMed

    Bleikamp, Sebastian; Thoma, Arne; Polop, Celia; Pirug, Gerhard; Linke, Udo; Michely, Thomas

    2006-03-24

    Scanning tunneling microscopy and low energy electron diffraction were used to investigate the growth of partly twinned Ir thin films on Ir(111). A transition from the expected layer-by-layer to a defect dominated growth mode with a fixed lateral length scale and increasing roughness is observed. During growth, the majority of the film is stably transformed to twinned stacking. This transition is initiated by the energetic avoidance of the formation of intrinsic stacking faults compared to two independent twin faults. The atomistic details of the defect kinetics are outlined.

  3. 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] controls growth plate development by inhibiting apoptosis in the reserve zone and stimulating response to 1alpha,25(OH)2D3 in hypertrophic cells.

    PubMed

    Boyan, B D; Hurst-Kennedy, J; Denison, T A; Schwartz, Z

    2010-07-01

    Previously we showed that costochondral growth plate resting zone (RC) chondrocytes response primarily to 24R,25(OH)2D3 whereas prehypertrophic and hypertrophic (GC) cells respond to 1alpha,25(OH)2D3. 24R,25(OH)2D3 increases RC cell proliferation and inhibits activity of matrix processing enzymes, suggesting it stabilizes cells in the reserve zone, possibly by inhibiting the matrix degradation characteristic of apoptotic hypertrophic GC cells. To test this, apoptosis was induced in rat RC cells by treatment with exogenous inorganic phosphate (Pi). 24R,25(OH)2D3 blocked apoptotic effects in a dose-dependent manner. Similarly, apoptosis was induced in ATDC5 cell cultures and 24R,25(OH)2D3 blocked this effect. Further studies indicated that 24R,25(OH)2D3 acts via at least two independent pathways. 24R,25(OH)2D3 increases LPA receptor-1 (LPA R1) expression and production of lysophosphatidic acid (LPA), and subsequent LPA R1/3-dependent signaling, thereby decreasing p53 abundance. LPA also increases the Bcl-2/Bax ratio. In addition, 24R,25(OH)2D3 acts by increasing PKC activity. 24R,25(OH)2D3 stimulates 1-hydroxylase activity, resulting in increased levels of 1,25(OH)2D3, and it increases levels of phospholipase A2 activating protein, which is required for rapid 1alpha,25(OH)2D3-dependent activation of PKC in GC cells. These results suggest that 24R,25(OH)2D3 modulates growth plate development by controlling the rate and extent of RC chondrocyte transition to a GC chondrocyte phenotype.

  4. 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

  5. 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.

  6. Wannier-Stark electro-optical effect, quasi-guided and photonic modes in 2D macroporous silicon structures with SiO2 coatings

    NASA Astrophysics Data System (ADS)

    Karachevtseva, L.; Goltviansky, Yu.; Sapelnikova, O.; Lytvynenko, O.; Stronska, O.; Bo, Wang; Kartel, M.

    2016-12-01

    Opportunities to enhance the properties of structured surfaces were demonstrated on 2D macroporous silicon structures with SiO2 coatings. We investigated the IR light absorption oscillations in macroporous silicon structures with SiO2 coatings 0-800 nm thick. The Wannier-Stark electro-optical effect due to strong electric field on Si-SiO2boundary and an additional electric field of quasi-guided optical modes were taken into account. The photonic modes and band gaps were also considered as peculiarities in absorbance spectra of macroporous silicon structures with a thick SiO2 coating. The photonic modes do not coincide with the quasi-guided modes in the silicon matrix and do not appear in absorption spectra of 2D macroporous silicon structures with surface nanocrystals.

  7. 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

  8. 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.

  9. 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.

  10. Growth of 2D sheets of a MOF on graphene surfaces to yield composites with novel gas adsorption characteristics.

    PubMed

    Kumar, Ram; Jayaramulu, Kolleboyina; Maji, Tapas Kumar; Rao, C N R

    2014-05-28

    Homogeneous graphene-MOF composites based on a 2D pillared-bilayer MOF (Cd-PBM), {[Cd4(azpy)2(pyrdc)4(H2O)2]·9H2O}n (azpy = 4,4'-azopyridine, pyrdc = pyridine-2,3-dicarboxylate), have been synthesized, using both graphene oxide (GO) and benzoic acid functionalized graphene (BFG). The composites GO@Cd-PBM and BFG@Cd-PBM demonstrate growth of the 2D nano-sheets of MOF on the graphene surface. While the pristine MOF, Cd-PBM shows selective CO2 uptake with a single-step type-I adsorption profile, the composites show stepwise CO2 uptake with a large hysteresis. With H2O and MeOH, on the other hand, the composites show a single-step adsorption unlike the parent MOF.

  11. 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

    2015-10-15

    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.

  12. 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).

  13. Co-nucleus 1D/2D Heterostructures with Bi2S3 Nanowire and MoS2 Monolayer: One-Step Growth and Defect-Induced Formation Mechanism.

    PubMed

    Li, Yongtao; Huang, Le; Li, Bo; Wang, Xiaoting; Zhou, Ziqi; Li, Jingbo; Wei, Zhongming

    2016-09-27

    Heterostructures constructed by low-dimensional (such as 0D, 1D, and 2D) materials have opened up opportunities for exploring interesting physical properties and versatile (opto)electronics. Recently, 2D/2D heterostructures, in particular, atomically thin graphene and transition-metal dichalcogenides, including graphene/MoS2, WSe2/MoS2, and WS2/WSe2, were efficiently prepared (by transfer techniques, chemical vapor deposition (CVD) growth, etc.) and systematically studied. In contrast, investigation of 1D/2D heterostructures was still very challenging and rarely reported, and the understanding of such heterostructures was also not well established. Herein, we demonstrate the one-step growth of a heterostructure on the basis of a 1D-Bi2S3 nanowire and a 2D-MoS2 monolayer through the CVD method. Multimeans were employed, and the results proved the separated growth of a Bi2S3 nanowire and a MoS2 sheet in the heterostructure rather than forming a BixMo1-xSy alloy due to their large lattice mismatch. Defect-induced co-nucleus growth, which was an important growth mode in 1D/2D heterostructures, was also experimentally confirmed and systematically investigated in our research. Such 1D/2D heterostructures were further fabricated and utilized in (opto)electronic devices, such as field-effect transistors and photodetectors, and revealed their potential for multifunctional design in electrical properties. The direct growth of such nanostructures will help us to gain a better comprehension of these specific configurations and allow device functionalities in potential applications.

  14. 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.

  15. Droplet growth during vapor-liquid transition in a 2D Lennard-Jones fluid.

    PubMed

    Midya, Jiarul; Das, Subir K

    2017-01-14

    Results for the kinetics of vapor-liquid phase transition have been presented from the molecular dynamics simulations of a single component two-dimensional Lennard-Jones fluid. The phase diagram for the model, primary prerequisite for this purpose, has been obtained via the Monte Carlo simulations. Our focus is on the region very close to the vapor branch of the coexistence curve. Quenches to such region provide morphology that consists of disconnected circular clusters in the vapor background. We identified that these clusters exhibit diffusive motion and grow via sticky collisions among them. The growth follows power-law behavior with time, exponent of which is found to be in nice agreement with a theoretical prediction.

  16. Droplet growth during vapor-liquid transition in a 2D Lennard-Jones fluid

    NASA Astrophysics Data System (ADS)

    Midya, Jiarul; Das, Subir K.

    2017-01-01

    Results for the kinetics of vapor-liquid phase transition have been presented from the molecular dynamics simulations of a single component two-dimensional Lennard-Jones fluid. The phase diagram for the model, primary prerequisite for this purpose, has been obtained via the Monte Carlo simulations. Our focus is on the region very close to the vapor branch of the coexistence curve. Quenches to such region provide morphology that consists of disconnected circular clusters in the vapor background. We identified that these clusters exhibit diffusive motion and grow via sticky collisions among them. The growth follows power-law behavior with time, exponent of which is found to be in nice agreement with a theoretical prediction.

  17. 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.

  18. Measured count-rate performance of the Discovery STE PET/CT scanner in 2D, 3D and partial collimation acquisition modes.

    PubMed

    Macdonald, L R; Schmitz, R E; Alessio, A M; Wollenweber, S D; Stearns, C W; Ganin, A; Harrison, R L; Lewellen, T K; Kinahan, P E

    2008-07-21

    We measured count rates and scatter fraction on the Discovery STE PET/CT scanner in conventional 2D and 3D acquisition modes, and in a partial collimation mode between 2D and 3D. As part of the evaluation of using partial collimation, we estimated global count rates using a scanner model that combined computer simulations with an empirical live-time function. Our measurements followed the NEMA NU2 count rate and scatter-fraction protocol to obtain true, scattered and random coincidence events, from which noise equivalent count (NEC) rates were calculated. The effect of patient size was considered by using 27 cm and 35 cm diameter phantoms, in addition to the standard 20 cm diameter cylindrical count-rate phantom. Using the scanner model, we evaluated two partial collimation cases: removing half of the septa (2.5D) and removing two-thirds of the septa (2.7D). Based on predictions of the model, a 2.7D collimator was constructed. Count rates and scatter fractions were then measured in 2D, 2.7D and 3D. The scanner model predicted relative NEC variation with activity, as confirmed by measurements. The measured 2.7D NEC was equal or greater than 3D NEC for all activity levels in the 27 cm and 35 cm phantoms. In the 20 cm phantom, 3D NEC was somewhat higher ( approximately 15%) than 2.7D NEC at 100 MBq. For all higher activity concentrations, 2.7D NEC was greater and peaked 26% above the 3D peak NEC. The peak NEC in 2.7D mode occurred at approximately 425 MBq, and was 26-50% greater than the peak 3D NEC, depending on object size. NEC in 2D was considerably lower, except at relatively high activity concentrations. Partial collimation shows promise for improved noise equivalent count rates in clinical imaging without altering other detector parameters.

  19. 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

  20. 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

    2015-12-19

    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

  1. Synthesis of silver nanostructures by simple redox under electrodeposited copper microcubes and the orient attachment growth of 2D silver

    NASA Astrophysics Data System (ADS)

    Wu, Guoxing; Yang, Sanjun; Liu, Qiming

    2015-12-01

    Copper microcubes about 500 nm were electrodeposited on ITO glasses. Silver nanoparticles, netty consist of short nanorods or nanowires, nanosheets with thickness about 40 nm, were successfully obtained by immersing ITOs with different concentration of AgNO3 solution. XRD, SEM and TEM were applied to characterize the products. Silver ions were initially reduced on the surface of copper, and then gradually decomposed the copper. Cuprous oxide intermediate was found to participate in the redox reaction. Both agglomerates on the cubes and escaped reductant nanoparticles act as the positions for anisotropic growth. Based on the experimental results, the roles of three kinds of cubes are discussed in preparing the nanosheets before proposing the possible growth process. Oriented attachment influenced and controlled the final shapes, such as layered nanonets, nanoplates and nanosheets. Big nanoparticles were inclined to link as nanowires, netty and even 2D porous structure consisted of 'nanosnakes', small reductant nanoparticles with silver around absorbed on the edge of silver nanoplate and further accelerated the extension of nanoplate until worked out, holes on the nanoplate confirmed that the adsorbed matters could be reductant nanoparticles. Reductant nanoparticles can also be exhausted before silver nanoparticles and nanoflakes absorbed on the growth positions.

  2. Chiral Second-Sound Collective Modes at the Edge of 2D Systems with a Nontrivial Berry Curvature

    NASA Astrophysics Data System (ADS)

    Principi, Alessandro; Katsnelson, Mikhail I.; Levchenko, Alex

    2017-01-01

    We study the thermal transport in two-dimensional systems with a nontrivial Berry curvature texture. The physical realizations are many; for the sake of definiteness, we consider undoped graphene gapped by the presence of an aligned hexagonal-boron-nitride substrate. The same phenomenology applies, i.e., to surface states of 3D topological insulators in the presence of a uniform magnetization. We find that chiral valley-polarized second-sound collective modes propagate along the edges of the system. The localization length of the edge modes has a topological origin stemming from the anomalous velocity term in the quasiparticle current. At low temperature, the single-particle contribution to the transverse thermal conductance is exponentially suppressed, and only second-sound modes carry heat along the boundary. A sharp change in the behavior of the thermal Hall conductance, extracted from nonlocal measurements of the temperature along the edge, marks the onset of ballistic heat transport due to second-sound edge modes.

  3. 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.

  4. Numerical investigation of the flat band Bloch modes in a 2D photonic crystal with Dirac cones.

    PubMed

    Zhang, Peng; Fietz, Chris; Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M

    2015-04-20

    A numerical method combining complex-k band calculations and absorbing boundary conditions for Bloch waves is presented. We use this method to study photonic crystals with Dirac cones. We demonstrate that the photonic crystal behaves as a zero-index medium when excited at normal incidence, but that the zero-index behavior is lost at oblique incidence due to excitation of modes on the flat band. We also investigate the formation of monomodal and multimodal cavity resonances inside the photonic crystals, and the physical origins of their different line-shape features.

  5. 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.

  6. A first attempt to enhance the 2-D single-crystal growth of a protein at an air/water interface from hydrodynamics

    NASA Astrophysics Data System (ADS)

    Drazek, L.; Legrand, J.-F.; Davoust, L.

    2005-02-01

    An alternative technique to grow a 2-D crystal of protein at a functionalized air/water interface is proposed. The first part of this paper briefly reviews 2-D crystal growth at a fluid interface and deals with our first experiments on streptavidin whose 2-D (poly)crystallization ability is well known. In the experiments, the involved air/water interface is functionalized with a mixed lipidic monolayer made of DOPC and biotinylated lipids. The second part of the paper relates to an alternative strategy we propose in order to enhance the 2-D single-crystal growth of a protein at a liquid interface. The idea is to get benefit from an axisymmetric swirling flow driven in a water sub-phase confined within an annular channel. The swirl is expected to control the distribution of the proteins at the air/water interface and to promote the growth of a 2-D single crystal from the smallest to the largest radii (radial segregation). An analytical modelling based on a low Reynolds number asymptotic development demonstrates how two control parameters, the mean channel curvature and the Reynolds number of the shear flow, can be helpful in tuning the magnitude of the swirl and therefore the crystal growth.

  7. 2D Si island nucleation on the Si(111) surface at initial and late growth stages: On the role of step permeability in pyramidlike growth

    NASA Astrophysics Data System (ADS)

    Rogilo, D. I.; Fedina, L. I.; Kosolobov, S. S.; Ranguelov, B. S.; Latyshev, A. V.

    2017-01-01

    Initial and late stages of 2D Si island nucleation and growth (2DNG) on extra-large ( 100 μm) and medium size (1-10 μm) atomically flat Si(111)-(7×7) terraces bordered by step bunches have been studied by in situ REM at T =600-750 °С. At first, the layer-by-layer 2DNG takes place on whole terraces and 2D island concentration dependence on deposition rate R corresponds to critical nucleus size i =1. Continuous 2DNG triggers morphological instabilities: elongated pyramidlike waves and separate pyramids emerge on all terraces at T ≤720 °С and T =750 °С, respectively. Both instabilities arise due to the imbalance of uphill/downhill adatom currents related with large Ehrlich-Schwöbel (ES) barriers and permeability of straight [ 11 bar 2 ] -type step edges. However, the first one is initiated by dominant downhill adatom current to distant sinks: bunches, wave's step edges, and "vacancy" islands emerging on terraces due to 2D island coalescence. As a result, top layer size decreases to the critical terrace width λ where 2DNG takes place. From the analysis of λ ∝ R - χ / 2 scaling at T =650 °C, we have found that i increases from i =2 on a three-layer wave to i =6-8 on a six-layer wave. This authenticates the significance of downhill adatom sink to distant steps related to the step permeability. The second instability type at T >720 °C is related to the raising of uphill adatom current due to slightly larger ES barrier for step-up attachment comparing to the step-down one (EES- 0.9 eV [Phys. Rev. Lett. 111 (2013) 036105]). This leads to "second layer" 2D nucleation on top layers, which triggers the growth of separate pyramids. Because of small difference between ES barriers, net uphill/downhill adatom currents are nearly equivalent, and therefore layer coverage distributions of both instabilities display similar linear slopes.

  8. 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.

  9. Temporal evolution of magma flow and degassing conditions during dome growth, insights from 2D numerical modeling

    NASA Astrophysics Data System (ADS)

    Chevalier, Laure; Collombet, Marielle; Pinel, Virginie

    2017-03-01

    Understanding magma degassing evolution during an eruption is essential to improving forecasting of effusive/explosive regime transitions at andesitic volcanoes. Lava domes frequently form during effusive phases, inducing a pressure increase both within the conduit and within the surrounding rocks. To quantify the influence of dome height on magma flow and degassing, we couple magma and gas flow in a 2D numerical model. The deformation induced by magma flow evolution is also quantified. From realistic initial magma flow conditions in effusive regime (Collombet, 2009), we apply increasing pressure at the conduit top as the dome grows. Since volatile solubility increases with pressure, dome growth is then associated with an increase in magma dissolved water content at a given depth, which corresponds with a decrease in magma porosity and permeability. Magma flow evolution is associated with ground deflation of a few μrad in the near field. However this signal is not detectable as it is hidden by dome subsidence (a few mrad). A Darcy flow model is used to study the impact of pressure and permeability conditions on gas flow in the conduit and surrounding rock. We show that dome permeability has almost no influence on magma degassing. However, increasing pressure in the surrounding rock, due to dome loading, as well as decreasing magma permeability in the conduit limit permeable gas loss at the conduit walls, thus causing gas pressurization in the upper conduit by a few tens of MPa. Decreasing magma permeability and increasing gas pressure increase the likelihood of magma explosivity and hazard in the case of a rapid decompression due to dome collapse.

  10. 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.

  11. Improved EDGE2D-EIRENE simulations of JET ITER-like wall L-mode discharges utilising poloidal VUV/visible spectral emission profiles

    NASA Astrophysics Data System (ADS)

    Lawson, K. D.; Groth, M.; Belo, P.; Brezinsek, S.; Corrigan, G.; Czarnecka, A.; Delabie, E.; Drewelow, P.; Harting, D.; Książek, I.; Maggi, C. F.; Marchetto, C.; Meigs, A. G.; Menmuir, S.; Stamp, M. F.; Wiesen, S.

    2015-08-01

    A discrepancy in the divertor radiated powers between EDGE2D-EIRENE simulations, both with and without drifts, and JET-ILW experiments employing a set of NBI-heated L-mode discharges with step-wise density variation is investigated. Results from a VUV/visible poloidally scanning spectrometer are used together with bolometric measurements to determine the radiated power and its composition. The analysis shows the importance of D line radiation in contributing to the divertor radiated power, while contributions from D radiative recombination are smaller than expected. Simulations with W divertor plates underestimate the Be content in the divertor, since no allowance is made for Be previously deposited on the plates being re-eroded. An improved version of EDGE2D-EIRENE is used to test the importance of the deposited layer in which the sputtering yield from supposed pure Be divertor plates is reduced to match the spectroscopic signals, while keeping the sputtering yield for the Be main chamber walls unchanged.

  12. 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

  13. 1alpha,25(OH)2D3 is an autocrine regulator of extracellular matrix turnover and growth factor release via ERp60 activated matrix vesicle metalloproteinases.

    PubMed

    Boyan, Barbara D; Wong, Kevin L; Fang, Mimi; Schwartz, Zvi

    2007-03-01

    Growth plate chondrocytes produce proteoglycan-rich type II collagen extracellular matrix (ECM). During cell maturation and hypertrophy, ECM is reorganized via a process regulated by 1alpha,25(OH)(2)D(3) and involving matrix metalloproteinases (MMPs), including MMP-3 and MMP-2. 1alpha,25(OH)(2)D(3) regulates MMP incorporation into matrix vesicles (MVs), where they are stored until released. Like plasma membranes (PM), MVs contain the 1alpha,25(OH)(2)D(3)-binding protein ERp60, phospholipase A(2) (PLA(2)), and caveolin-1, but appear to lack nuclear Vitamin D receptors (VDRs). Chondrocytes produce 1alpha,25(OH)(2)D(3) (10(-8)M), which binds ERp60, activating PLA(2), and resulting lysophospholipids lead to MV membrane disorganization, releasing active MMPs. MV MMP-3 activates TGF-beta1 stored in the ECM as large latent TGF-beta1 complexes, consisting of latent TGF-beta1 binding protein, latency associated peptide, and latent TGF-beta1. Others have shown that MMP-2 specifically activates TGF-beta2. TGF-beta1 regulates 1alpha,25(OH)(2)D(3)-production, providing a mechanism for local control of growth factor activation. 1alpha,25(OH)(2)D(3) activates PKCalpha in the PM via ERp60-signaling through PLA(2), lysophospholipid production, and PLCbeta. It also regulates distribution of phospholipids and PKC isoforms between MVs and PMs, enriching the MVs in PKCzeta. Direct activation of MMP-3 in MVs requires ERp60. However, when MVs are treated with 1alpha,25(OH)(2)D(3), PKCzeta activity is decreased and PKCalpha is unaffected, suggesting a more complex feedback mechanism, potentially involving MV lipid signaling.

  14. Synergistic Effects of Temperature, Oxidation and Multicracking Modes on Damage Evolution and Life Prediction of 2D Woven Ceramic-Matrix Composites under Tension-Tension Fatigue Loading

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-11-01

    In this paper, the synergistic effects of temperature, oxidation and multicracking modes on damage evolution and life prediction in 2D woven ceramic-matrix composites (CMCs) have been investigated. The damage parameter of fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of CMCs. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperature, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composite fatigue fractures. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S-N curves of SiC/SiC at 1000, 1200 and 1300 °C in air and steam condition have been predicted. The synergistic effects of temperature, oxidation, fatigue peak stress, and multicracking modes on the evolution of interface shear stress and fatigue hysteresis dissipated energy versus cycle numbers curves have been analyzed.

  15. 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.

  16. 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

    2016-05-05

    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.

  17. 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.

  18. 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.

  19. 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.

  20. Possible burst-like facet growth mode at high temperatures

    NASA Astrophysics Data System (ADS)

    Lovrić, Davorin; Vučić, Zlatko; Gladić, Jadranko

    2008-07-01

    A decade ago, a burst-like growth mode of c-facets of 4He crystals growing at mK temperatures, characterized by the alternation of time intervals during which the facet does not advance with the intervals of its fast advancement, was found [J.P. Ruutu, P.J. Hakonen, A.V. Babkin, A.Y. Parshin, J.S. Penttilä, J.P. Saramäki, G. Tvalashvili, Phys. Rev. Lett. 76 (1996) 4187]. We investigate the possibility that a similar facet growth mode exists for facets at high growth temperatures. We have applied the digital laser interferometry for monitoring facet kinetics of spherical copper selenide single crystals during their growth at constant volume growth rate around 800 K. Our analysis of directly measured (1 1 1) facet advancement curves has revealed that they consist of time intervals during which the facet does not advance vertically alternating with the time intervals of enhanced growth, resembling the burst-like facet growth mode. The results are discussed in terms of the enhancement of the local supersaturation induced by the existence of nucleation barrier.

  1. Growth mechanisms of 2D organic assemblies generated from dialkylated melaminium derivatives: the length difference of the two alkyl chains that matters.

    PubMed

    Xu, Jun; Wu, Guanglu; Wang, Zhiqiang; Zhang, Xi

    2013-08-27

    This research is aimed to understand the growth mechanisms for self-assembly of dialkylated melamine derivatives. The dialkylated melamine derivatives with different alkyl chains (Mela-m-n) are able to self-assemble with hydrochloric acid in dichloromethane to form 2D organic assemblies, exhibiting similar lamellar structures as Mela-n·HCl with identical alkyl chains. The most interesting finding is that the growth mechanism of Mela-n·HCl with identical alkyl chains is revealed to be layer growth, while Mela-m-n·HCl with asymmetric alkyl chains adopts a spiral growth mechanism. The asymmetric alkyl chains in Mela-m-n may lead to the formation of dislocation, which is responsible for the spiral growth mechanism.

  2. 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

  3. 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.

  4. 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%).

  5. Dynamic growth of mixed-mode shear cracks

    USGS Publications Warehouse

    Andrews, D.J.

    1994-01-01

    A pure mode II (in-plane) shear crack cannot propagate spontaneously at a speed between the Rayleigh and S-wave speeds, but a three-dimensional (3D) or two-dimensional (2D) mixed-mode shear crack can propagate in this range, being driven by the mode III (antiplane) component. Two different analytic solutions have been proposed for the mode II component in this case. The first is the solution valid for crack speed less than the Rayleigh speed. When applied above the Rayleigh speed, it predicts a negative stress intensity factor, which implies that energy is generated at the crack tip. Burridge proposed a second solution, which is continuous at the crack tip, but has a singularity in slip velocity at the Rayleigh wave. Spontaneous propagation of a mixed-mode rupture has been calculated with a slip-weakening friction law, in which the slip velocity vector is colinear with the total traction vector. Spontaneous trans-Rayleigh rupture speed has been found. The solution depends on the absolute stress level. The solution for the in-plane component appears to be a superposition of smeared-out versions of the two analytic solutions. The proportion of the first solution increases with increasing absolute stress. The amplitude of the negative in-plane traction pulse is less than the absolute final sliding traction, so that total in-plane traction does not reverse. The azimuth of the slip velocity vector varies rapidly between the onset of slip and the arrival of the Rayleigh wave. The variation is larger at smaller absolute stress.

  6. Two-Dimensional Visualization of Growth and Burst of the Edge-Localized Filaments in KSTAR H-Mode Plasmas

    NASA Astrophysics Data System (ADS)

    Yun, G. S.; Lee, W.; Choi, M. J.; Lee, J.; Park, H. K.; Tobias, B.; Domier, C. W.; Luhmann, N. C., Jr.; Donné, A. J. H.; Lee, J. H.

    2011-07-01

    The filamentary nature and dynamics of edge-localized modes (ELMs) in the KSTAR high-confinement mode plasmas have been visualized in 2D via electron cyclotron emission imaging. The ELM filaments rotating with a net poloidal velocity are observed to evolve in three distinctive stages: initial linear growth, interim quasisteady state, and final crash. The crash is initiated by a narrow fingerlike perturbation growing radially from a poloidally elongated filament. The filament bursts through this finger, leading to fast and collective heat convection from the edge region into the scrape-off layer, i.e., ELM crash.

  7. Characterization of Mode I and Mode II delamination growth and thresholds in AS4/PEEK composites

    NASA Technical Reports Server (NTRS)

    Martin, Roderick H.; Murri, Gretchen Bostaph

    1990-01-01

    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.

  8. 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.

  9. 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.

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

    PubMed

    Bielewicz, Thomas; Klein, Eugen; Klinke, Christian

    2016-09-02

    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.

  11. 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.

  12. Initiation and growth of mode II delamination in toughened composites

    NASA Astrophysics Data System (ADS)

    Russell, Alan J.

    The origins of nonlinearity in the mode-II delamination fracture of three organic-matrix carbon-fiber composite materials was investigated. This was accomplished by testing specimens with different types of starter cracks and by loading and unloading these specimens several times so that the change in nonlinearity as the delaminations grew could be measured. The load at which crack growth initiated was determined by acoustic emission. Slow crack growth as found to be the principal cause of nonlinearity in the materials tested. The crack velocity obeyed the same power law dependence on GII as is observed for slow crack growth in viscoelastic polymers. For the first loading from the end of the starter cracks, plastic deformation at the crack tip also contributed to the nonlinearity. Other sources of nonlinearity included an increasing fracture resistance in one of the materials as well as problems associated with producing a clean starter notch with a straight crack front.

  13. Promotion of protein crystal growth by actively switching crystal growth mode via femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Tominaga, Yusuke; Maruyama, Mihoko; Yoshimura, Masashi; Koizumi, Haruhiko; Tachibana, Masaru; Sugiyama, Shigeru; Adachi, Hiroaki; Tsukamoto, Katsuo; Matsumura, Hiroyoshi; Takano, Kazufumi; Murakami, Satoshi; Inoue, Tsuyoshi; Yoshikawa, Hiroshi Y.; Mori, Yusuke

    2016-11-01

    Large single crystals with desirable shapes are essential for various scientific and industrial fields, such as X-ray/neutron crystallography and crystalline devices. However, in the case of proteins the production of such crystals is particularly challenging, despite the efforts devoted to optimization of the environmental, chemical and physical parameters. Here we report an innovative approach for promoting the growth of protein crystals by directly modifying the local crystal structure via femtosecond laser ablation. We demonstrate that protein crystals with surfaces that are locally etched (several micrometers in diameter) by femtosecond laser ablation show enhanced growth rates without losing crystal quality. Optical phase-sensitive microscopy and X-ray topography imaging techniques reveal that the local etching induces spiral growth, which is energetically advantageous compared with the spontaneous two-dimensional nucleation growth mode. These findings prove that femtosecond laser ablation can actively switch the crystal growth mode, offering flexible control over the size and shape of protein crystals.

  14. Identification of the Excited-State C═C and C═O Modes of trans-β-Apo-8'-carotenal with Transient 2D-IR-EXSY and Femtosecond Stimulated Raman Spectroscopy.

    PubMed

    Di Donato, Mariangela; Ragnoni, Elena; Lapini, Andrea; Kardaś, Tomasz M; Ratajska-Gadomska, Boźena; Foggi, Paolo; Righini, Roberto

    2015-05-07

    Assigning the vibrational modes of molecules in the electronic excited state is often a difficult task. Here we show that combining two nonlinear spectroscopic techniques, transient 2D exchange infrared spectroscopy (T2D-IR-EXSY) and femtosecond stimulated Raman spectroscopy (FSRS), the contribution of the C═C and C═O modes in the excited-state vibrational spectra of trans-β-apo-8'-carotenal can be unambiguously identified. The experimental results reported in this work confirm a previously proposed assignment based on quantum-chemical calculations and further strengthen the role of an excited state with charge-transfer character in the relaxation pathway of carbonyl carotenoids. On a more general ground, our results highlight the potentiality of nonlinear spectroscopic methods based on the combined use of visible and infrared pulses to correlate structural and electronic changes in photoexcited molecules.

  15. Insights into the growth rate of spatially evolving plane turbulent free-shear layers from 2D vortex-gas simulations

    NASA Astrophysics Data System (ADS)

    Suryanarayanan, Saikishan; Narasimha, Roddam

    2017-02-01

    Although the free-shear or mixing layer has been a subject of extensive research over nearly a century, there are certain fundamental issues that remain controversial. These include the influence of initial and downstream conditions on the flow, the effect of velocity ratio across the layer, and the nature of any possible coupling between small scale dynamics and the large scale evolution of layer thickness. In the spirit of the temporal vortex-gas simulations of Suryanarayanan et al. ["Free turbulent shear layer in a point vortex gas as a problem in nonequilibrium statistical mechanics," Phys. Rev. E 89, 013009 (2014)], we revisit the simple 2D inviscid vortex-gas model with extensive computations and detailed analysis, in order to gain insights into some of the above issues. Simulations of the spatially evolving vortex-gas shear layer are carried out at different velocity ratios using a computational model based on the work of Basu et al. ["Vortex sheet simulation of a plane canonical mixing layer," Comput. Fluids 21, 1-30 (1992) and "Modelling plane mixing layers using vortex points and sheets," Appl. Math. Modell. 19, 66-75 (1995)], but with a crucial improvement that ensures conservation of global circulation. The simulations show that the conditions imposed at the origin of the free shear layer and at the exit to the computational domain can affect flow evolution in their respective downstream and upstream neighbourhoods, the latter being particularly strong in the single stream limit. In between these neighbourhoods at the ends is a regime of universal self-preserving growth rate given by a universal function of velocity ratio. The computed growth rates are generally located within the scatter of experimental data on plane mixing layers and closely agree with recent high Reynolds number experiments and 3D large eddy simulation studies. These findings support the view that observed free-shear layer growth can be largely explained by the 2D vortex dynamics of

  16. Island growth as a growth mode in atomic layer deposition: A phenomenological model

    NASA Astrophysics Data System (ADS)

    Puurunen, Riikka L.; Vandervorst, Wilfried

    2004-12-01

    Atomic layer deposition (ALD) has recently gained world-wide attention because of its suitability for the fabrication of conformal material layers with thickness in the nanometer range. Although the principles of ALD were realized about 40 years ago, the description of many physicochemical processes that occur during ALD growth is still under development. A constant amount of material deposited in an ALD reaction cycle, that is, growth-per-cycle (GPC), has been a paradigm in ALD through decades. The GPC may vary, however, especially in the beginning of the ALD growth. In this work, a division of ALD processes to four classes is proposed, on the basis of how the GPC varies with the number of ALD reaction cycles: linear growth, substrate-enhanced growth, and substrate-inhibited growth of type 1 and type 2. Island growth is identified as a likely origin for type 2 substrate-inhibited growth, where the GPC increases and goes through a maximum before it settles to a constant value characteristic of a steady growth. A simple phenomenological model is developed to describe island growth in ALD. The model assumes that the substrate is unreactive with the ALD reactants, except for reactive defects. ALD growth is assumed to proceed symmetrically from the defects, resulting islands of a conical shape. Random deposition is the growth mode on the islands. The model allows the simulation of GPC curves, surface fraction curves, and surface roughness, with physically significant parameters. When the model is applied to the zirconium tetrachloride/water and the trimethylaluminum/water ALD processes on hydrogen-terminated silicon, the calculated GPC curves and surface fractions agree with the experiments. The island growth model can be used to assess the occurrence of island growth, the size of islands formed, and point of formation of a continuous ALD-grown film. The benefits and limitations of the model and the general characteristics of type 2 substrate-inhibited ALD are

  17. Growth rate, transmission mode and virulence in human pathogens

    PubMed Central

    Cornwallis, Charlie K.; Buckling, Angus; West, Stuart A.

    2017-01-01

    The harm that pathogens cause to hosts during infection, termed virulence, varies across species from negligible to a high likelihood of rapid death. Classic theory for the evolution of virulence is based on a trade-off between pathogen growth, transmission and host survival, which predicts that higher within-host growth causes increased transmission and higher virulence. However, using data from 61 human pathogens, we found the opposite correlation to the expected positive correlation between pathogen growth rate and virulence. We found that (i) slower growing pathogens are significantly more virulent than faster growing pathogens, (ii) inhaled pathogens and pathogens that infect via skin wounds are significantly more virulent than pathogens that are ingested, but (iii) there is no correlation between symptoms of infection that aid transmission (such as diarrhoea and coughing) and virulence. Overall, our results emphasize how virulence can be influenced by mechanistic life-history details, especially transmission mode, that determine how parasites infect and exploit their hosts. This article is part of the themed issue ‘Opening the black box: re-examining the ecology and evolution of parasite transmission’. PMID:28289261

  18. Characterization of the growth of 2D protein crystals on a lipid monolayer by ellipsometry and rigidity measurements coupled to electron microscopy.

    PubMed Central

    Vénien-Bryan, C; Lenne, P F; Zakri, C; Renault, A; Brisson, A; Legrand, J F; Berge, B

    1998-01-01

    We present here some sensitive optical and mechanical experiments for monitoring the process of formation and growth of two-dimensional (2D) crystals of proteins on a lipid monolayer at an air-water interface. The adsorption of proteins on the lipid monolayer was monitored by ellipsometry measurements. An instrument was developed to measure the shear elastic constant (in plane rigidity) of the monolayer. These experiments have been done using cholera toxin B subunit (CTB) and annexin V as model proteins interacting with a monosialoganglioside (GM1) and dioleoylphosphatidylserine (DOPS), respectively. Electron microscopy observations of the protein-lipid layer transferred to grids were systematically used as a control. We found a good correlation between the measured in-plane rigidity of the monolayer and the presence of large crystalline domains observed by electron microscopy grids. Our interpretation of these data is that the crystallization process of proteins on a lipid monolayer passes through at least three successive stages: 1) molecular recognition between protein and lipid-ligand, i.e., adsorption of the protein on the lipid layer; 2) nucleation and growth of crystalline patches whose percolation is detected by the appearance of a non-zero in-plane rigidity; and 3) annealing of the layer producing a slower increase of the lateral or in-plane rigidity. PMID:9591688

  19. 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.

  20. 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.

  1. The mode I crack growth resistance of metallic foams

    NASA Astrophysics Data System (ADS)

    Chen, C.; Fleck, N. A.; Lu, T. J.

    2001-02-01

    A Dugdale-type cohesive zone model is used to predict the mode I crack growth resistance ( R-curve) of metallic foams, with the fracture process characterised by an idealised traction-separation law that relates the crack surface traction to crack opening displacement. A quadratic yield function, involving the von Mises effective stress and mean stress, is used to account for the plastic compressibility of metallic foams. Finite element calculations are performed for the crack growth resistance under small scale yielding and small scale bridging in plane strain, with K-field boundary conditions. The following effects upon the fracture process are quantified: material hardening, bridging strength, T-stress (the non-singular stress acting parallel to the crack plane), and the shape of yield surface. To study the failure behaviour and notch sensitivity of metallic foams in the presence of large scale yielding, a study is made for panels embedded with either a centre-crack or an open hole and subjected to tensile stressing. For the centre-cracked panel, a transition crack size is predicted for which the fracture response switches from net section yielding to elastic-brittle fracture. Likewise, for a panel containing a centre-hole, a transition hole diameter exists for which the fracture response switches from net section yielding to a local maximum stress criterion at the edge of the hole.

  2. A combination of 2D similarity search, pharmacophore, and molecular docking techniques for the identification of vascular endothelial growth factor receptor-2 inhibitors.

    PubMed

    Ai, Guanhua; Tian, Caiping; Deng, Dawei; Fida, Guissi; Chen, Haiyan; Ma, Yuxiang; Ding, Li; Gu, Yueqing

    2015-04-01

    The human vascular endothelial growth factor receptor-2 (VEGFR-2) has been an attractive target for the inhibition of angiogenesis. In the current study, we used a hybrid protocol of virtual screening methods to retrieve new VEGFR-2 inhibitors from the Zinc-Specs Database (441 574 compounds). The hybrid protocol included the initial screening of candidates by comparing the 2D similarity to five reported top active inhibitors of 13 VEGFR-2 X-ray crystallography structures, followed by the pharmacophore modeling of virtual screening on the basis of receptor-ligand interactions and further narrowing by LibDOCK to obtain the final hits. Two compounds (AN-919/41439526 and AK-968/40939851) with a high libscore were selected as the final hits for a subsequent cell cytotoxicity study. The two compounds screened exerted significant inhibitory effects on the proliferation of cancer cells (U87 and MCF-7). The results indicated that the hybrid procedure is an effective approach for screening specific receptor inhibitors.

  3. 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.

  4. 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).

  5. 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.

  6. 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.

  7. 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.

  8. Growth mode and structures of magnetic Mn clusters on graphene

    DOE PAGES

    Liu, Xiaojie; Wang, Cai-Zhuang

    2016-06-22

    We present a systematic study of Mn clusters on graphene by first-principles calculations. We show that the growth of Mn on graphene follows a three-dimensional (3D) mode. Both adsorption and attachment energies show that (Mn)3 and (Mn)6 on graphene are energetically favorable in the size range (Mn)1-7. Moreover, larger formation energy for Mn cluster on graphene implies the incoming Mn atoms are likely to nucleate and grow into bigger and bigger Mn clusters on graphene. The magnetic moments of (Mn)1,5,7 on graphene are enhanced by 11%, 186%, and 26% from their values at free-standing clusters, respectively. By contrast, the netmore » magnetic moment of (Mn)2,3,4,6 on graphene is reduced from that of the corresponding free-standing clusters. The origin of the magnetic moment changes can be attributed to the charge transfer within the Mn clusters and between the clusters and graphene upon adsorption.« less

  9. Growth mode and structures of magnetic Mn clusters on graphene

    SciTech Connect

    Liu, Xiaojie; Wang, Cai-Zhuang

    2016-06-22

    We present a systematic study of Mn clusters on graphene by first-principles calculations. We show that the growth of Mn on graphene follows a three-dimensional (3D) mode. Both adsorption and attachment energies show that (Mn)3 and (Mn)6 on graphene are energetically favorable in the size range (Mn)1-7. Moreover, larger formation energy for Mn cluster on graphene implies the incoming Mn atoms are likely to nucleate and grow into bigger and bigger Mn clusters on graphene. The magnetic moments of (Mn)1,5,7 on graphene are enhanced by 11%, 186%, and 26% from their values at free-standing clusters, respectively. By contrast, the net magnetic moment of (Mn)2,3,4,6 on graphene is reduced from that of the corresponding free-standing clusters. The origin of the magnetic moment changes can be attributed to the charge transfer within the Mn clusters and between the clusters and graphene upon adsorption.

  10. 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.

  11. Characterization of Mode I and mixed-mode delamination growth in T300/5208 graphite/epoxy

    NASA Technical Reports Server (NTRS)

    Ramkumar, R. L.; Whitcomb, J. D.

    1985-01-01

    The roles played by Mode I and Mode II strain-energy release rates (G-I and G-II, respectively) in inducing delamination growth under static and fatigue loading were investigated, using T300/5208 graphite/epoxy specimens. Double cantilever beam (DCB) specimens and cracked lap shear (CLS) specimens were used for pure Mode I and mixed-mode tests, respectively. Fatigue-induced delamination growth was characterized by constant-amplitude fatigue tests at a minimum to maximum cyclic load ratio of 0.05 and a frequency of 10 Hz. During the tests, the maximum and minimum strain-energy release rates (Gmax, Gmin) and the delamination growth rate (da/dN) were monitored. Static tests on mixed-mode CLS specimens measured the total strain-energy release rate, which was broken into G-I and G-II components using finite-element analysis. A power-law relationship between da/dN and G-Imax, and da/dN and Gmax were obtained from fatigue test results on DCB and CLS specimens, respectively. The power law for a pure Mode II delamination was derived from CLS results by subtracting the contribution due to G-I.

  12. 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.

  13. High-Performance One-Body Core/Shell Nanowire Supercapacitor Enabled by Conformal Growth of Capacitive 2D WS2 Layers.

    PubMed

    Choudhary, Nitin; Li, Chao; Chung, Hee-Suk; Moore, Julian; Thomas, Jayan; Jung, Yeonwoong

    2016-12-27

    Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have emerged as promising capacitive materials for supercapacitor devices owing to their intrinsically layered structure and large surface areas. Hierarchically integrating 2D TMDs with other functional nanomaterials has recently been pursued to improve electrochemical performances; however, it often suffers from limited cyclic stabilities and capacitance losses due to the poor structural integrity at the interfaces of randomly assembled materials. Here, we report high-performance core/shell nanowire supercapacitors based on an array of one-dimensional (1D) nanowires seamlessly integrated with conformal 2D TMD layers. The 1D and 2D supercapacitor components possess "one-body" geometry with atomically sharp and structurally robust core/shell interfaces, as they were spontaneously converted from identical metal current collectors via sequential oxidation/sulfurization. These hybrid supercapacitors outperform previously developed any stand-alone 2D TMD-based supercapacitors; particularly, exhibiting an exceptional charge-discharge retention over 30,000 cycles owing to their structural robustness, suggesting great potential for unconventional energy storage technologies.

  14. Modification of the tearing mode growth rate by the presence of a stochastic magnetic field

    SciTech Connect

    Carreras, B. A.; Rosenbluth, M. N.; Hicks, H. R.

    1980-12-01

    We have studied the effect of a stochastic magnetic field on the growth of a tearing mode. An analytic solution is given for the case in which the stochastic magnetic field is static. In that case, an unstable tearing mode is further destabilized (stabilized) if the ..delta..' values of the nonlinearly driven modes are positive (negative). This mechanism explains the destabilization of the (m = 3; n = 2) tearing mode observed in nonlinear three-dimensional calculations.

  15. 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.

  16. The essential features and modes of bacterial polar growth.

    PubMed

    Cameron, Todd A; Zupan, John R; Zambryski, Patricia C

    2015-06-01

    Polar growth represents a surprising departure from the canonical dispersed cell growth model. However, we know relatively little of the underlying mechanisms governing polar growth or the requisite suite of factors that direct polar growth. Underscoring how classic doctrine can be turned on its head, the peptidoglycan layer of polar-growing bacteria features unusual crosslinks and in some species the quintessential cell division proteins FtsA and FtsZ are recruited to the growing poles. Remarkably, numerous medically important pathogens utilize polar growth, accentuating the need for intensive research in this area. Here we review models of polar growth in bacteria based on recent research in the Actinomycetales and Rhizobiales, with emphasis on Mycobacterium and Agrobacterium species.

  17. Transverse instability of electron plasma waves study via direct 2 +2D Vlasov simulations

    NASA Astrophysics Data System (ADS)

    Silantyev, Denis; Lushnikov, Pavel; Rose, Harvey

    2016-10-01

    Transverse instability can be viewed as initial stage of electron plasma waves (EPWs) filamentation. We performed direct 2 +2D Vlasov-Poisson simulations of collisionless plasma to systematically study the growth rates of oblique modes of finite-amplitude EPW depending on its amplitude, wavenumber, angle of the oblique mode wavevector relative to the EPW's wavevector and the configuration of the trapped electrons in the EPW. Simulation results are compared to the predictions of theoretical models.

  18. Antibiotic growth promoters in agriculture: history and mode of action.

    PubMed

    Dibner, J J; Richards, J D

    2005-04-01

    This report will review the history of antibiotic growth promoter (AGP) use in the animal industry, concerns about development of antimicrobial resistance, and response in the European Union and United States to these concerns. A brief description of the history of legislation regarding feed use of antimicrobials in Denmark and the experience of animal producers following the 1998 ban will serve to illustrate the consequences on animal performance and health of withdrawing the approval for this use. The biological basis for antibiotic effects on animal growth efficiency will consider effects on intestinal microbiota and effects on the host animal and will use the germ-free animal to illustrate effects of the conventional microflora. The probability that no single compound will replace all of the functions of antimicrobial growth promoters will be considered, and methods to consolidate and analyze the enlarging database will be discussed.

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

    DOE PAGES

    Tselev, Alexander; Vasudevan, Rama K.; Gianfrancesco, Anthony G.; ...

    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

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

    SciTech Connect

    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 parameter is dependent on the mechanism of epitaxial strain relaxation, which is controlled by the oxidative power of the deposition environment.

  1. 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.

  2. Biofilm mode of growth of Streptococcus intermedius favored by a competence-stimulating signaling peptide.

    PubMed

    Petersen, Fernanda C; Pecharki, Daniele; Scheie, Anne A

    2004-09-01

    Gram-positive and gram-negative bacteria use quorum sensing to coordinate population behavior. In several streptococci, quorum sensing mediated by competence-stimulating peptides (CSP) is associated with development of competence for transformation. We show here that a synthetic CSP favored the biofilm mode of growth of Streptococcus intermedius without affecting the rate of culture growth.

  3. 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.

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

    PubMed

    Dahiya, Abhishek Singh; Opoku, Charles; Alquier, Daniel; Poulin-Vittrant, Guylaine; Cayrel, Frederic; Graton, Olivier; Hue, Louis-Pascal Tran Huu; Camara, Nicolas

    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.

  5. 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

  6. [Effects of nitrogen source and aeration mode on algae growth in freshwater].

    PubMed

    Liu, Chun-Guang; Jin, Xiang-Can; Sun, Ling; Sun, Hong-Wen; Zhu, Lin; Yu, Yang; Dai, Shu-Gui; Zhuang, Yuan-Yi

    2006-01-01

    Aquarium microcosms were used to study the effects of nitrogen source and aeration mode on the growth and species changes of algae in freshwater. Nitrate nitrogen(NO3(-) -N) and ammonia nitrogen(NH4(+) -N) were used as nitrogen sources. For each nitrogen source, four modes of aeration were selected, including control, continuous aeration, aeration during the day, and aeration at night. In the early stage of the experiment, algae in the NH4(+) -N treatment experiment grew well. In the later stage, algae in the NO3(-) -N treatment experiment grew better. For different aeration modes, continuous aeration show varied effects on algae growth in the two nitrogen source treatments. Day-only aeration had little effect on algae growth. Night-only aeration inhibited algae growth considerably. In NH(+) -N treatments, cyanophyta became dominant species easily. In contrast, chlorophyta dominated in NO3(-) -N treatments.

  7. 2D semiconductor optoelectronics

    NASA Astrophysics Data System (ADS)

    Novoselov, Kostya

    The advent of graphene and related 2D materials has recently led to a new technology: heterostructures based on these atomically thin crystals. The paradigm proved itself extremely versatile and led to rapid demonstration of tunnelling diodes with negative differential resistance, tunnelling transistors, photovoltaic devices, etc. By taking the complexity and functionality of such van der Waals heterostructures to the next level we introduce quantum wells engineered with one atomic plane precision. Light emission from such quantum wells, quantum dots and polaritonic effects will be discussed.

  8. 2D quasiperiodic plasmonic crystals

    PubMed Central

    Bauer, Christina; Kobiela, Georg; Giessen, Harald

    2012-01-01

    Nanophotonic structures with irregular symmetry, such as quasiperiodic plasmonic crystals, have gained an increasing amount of attention, in particular as potential candidates to enhance the absorption of solar cells in an angular insensitive fashion. To examine the photonic bandstructure of such systems that determines their optical properties, it is necessary to measure and model normal and oblique light interaction with plasmonic crystals. We determine the different propagation vectors and consider the interaction of all possible waveguide modes and particle plasmons in a 2D metallic photonic quasicrystal, in conjunction with the dispersion relations of a slab waveguide. Using a Fano model, we calculate the optical properties for normal and inclined light incidence. Comparing measurements of a quasiperiodic lattice to the modelled spectra for angle of incidence variation in both azimuthal and polar direction of the sample gives excellent agreement and confirms the predictive power of our model. PMID:23209871

  9. Dacarbazine-mediated upregulation of NKG2D ligands on tumor cells activates NK and CD8 T cells and restrains melanoma growth.

    PubMed

    Hervieu, Alice; Rébé, Cédric; Végran, Frédérique; Chalmin, Fanny; Bruchard, Mélanie; Vabres, Pierre; Apetoh, Lionel; Ghiringhelli, François; Mignot, Grégoire

    2013-02-01

    Dacarbazine (DTIC) is a cytotoxic drug widely used for melanoma treatment. However, the putative contribution of anticancer immune responses in the efficacy of DTIC has not been evaluated. By testing how DTIC affects host immune responses to cancer in a mouse model of melanoma, we unexpectedly found that both natural killer (NK) and CD8(+) T cells were indispensable for DTIC therapeutic effect. Although DTIC did not directly affect immune cells, it triggered the upregulation of NKG2D ligands on tumor cells, leading to NK cell activation and IFNγ secretion in mice and humans. NK cell-derived IFNγ subsequently favored upregulation of major histocompatibility complex class I molecules on tumor cells, rendering them sensitive to cytotoxic CD8(+) T cells. Accordingly, DTIC markedly enhanced cytotoxic T lymphocyte antigen 4 inhibition efficacy in vivo in an NK-dependent manner. These results underscore the immunogenic properties of DTIC and provide a rationale to combine DTIC with immunotherapeutic agents that relieve immunosuppression in vivo.

  10. The Growth Mechanism of Transition Metal Dichalcogenides by using Sulfurization of Pre-deposited Transition Metals and the 2D Crystal Hetero-structure Establishment

    PubMed Central

    Wu, Chong-Rong; Chang, Xiang-Rui; Wu, Chao-Hsin; Lin, Shih-Yen

    2017-01-01

    A growth model is proposed for the large-area and uniform MoS2 film grown by using sulfurization of pre-deposited Mo films on sapphire substrates. During the sulfurization procedure, the competition between the two mechanisms of the Mo oxide segregation to form small clusters and the sulfurization reaction to form planar MoS2 film is determined by the amount of background sulfur. Small Mo oxide clusters are observed under the sulfur deficient condition, while large-area and complete MoS2 films are obtained under the sulfur sufficient condition. Precise layer number controllability is also achieved by controlling the pre-deposited Mo film thicknesses. The drain currents in positive dependence on the layer numbers of the MoS2 transistors with 1-, 3- and 5- layer MoS2 have demonstrated small variation in material characteristics between each MoS2 layer prepared by using this growth technique. By sequential transition metal deposition and sulfurization procedures, a WS2/MoS2/WS2 double hetero-structure is demonstrated. Large-area growth, layer number controllability and the possibility of hetero-structure establishment by using sequential metal deposition and following sulfurization procedures have revealed the potential of this growth technique for practical applications. PMID:28176836

  11. The Growth Mechanism of Transition Metal Dichalcogenides by using Sulfurization of Pre-deposited Transition Metals and the 2D Crystal Hetero-structure Establishment

    NASA Astrophysics Data System (ADS)

    Wu, Chong-Rong; Chang, Xiang-Rui; Wu, Chao-Hsin; Lin, Shih-Yen

    2017-02-01

    A growth model is proposed for the large-area and uniform MoS2 film grown by using sulfurization of pre-deposited Mo films on sapphire substrates. During the sulfurization procedure, the competition between the two mechanisms of the Mo oxide segregation to form small clusters and the sulfurization reaction to form planar MoS2 film is determined by the amount of background sulfur. Small Mo oxide clusters are observed under the sulfur deficient condition, while large-area and complete MoS2 films are obtained under the sulfur sufficient condition. Precise layer number controllability is also achieved by controlling the pre-deposited Mo film thicknesses. The drain currents in positive dependence on the layer numbers of the MoS2 transistors with 1-, 3- and 5- layer MoS2 have demonstrated small variation in material characteristics between each MoS2 layer prepared by using this growth technique. By sequential transition metal deposition and sulfurization procedures, a WS2/MoS2/WS2 double hetero-structure is demonstrated. Large-area growth, layer number controllability and the possibility of hetero-structure establishment by using sequential metal deposition and following sulfurization procedures have revealed the potential of this growth technique for practical applications.

  12. On a separating method for mixed-modes crack growth in wood material using image analysis

    NASA Astrophysics Data System (ADS)

    Moutou Pitti, R.; Dubois, F.; Pop, O.

    2010-06-01

    Due to the complex wood anatomy and the loading orientation, the timber elements are subjected to a mixed-mode fracture. In these conditions, the crack tip advance is characterized by mixed-mode kinematics. In order to characterize the fracture process function versus the loading orientation, a new mixed-mode crack growth timber specimen is proposed. In the present paper, the design process and the experimental validation of this specimen are proposed. Using experimental results, the energy release rate is calculated for several modes. The calculi consist on the separation of each fracture mode. The design of the specimen is based on the analytical approach and numerical simulation by finite element method. The specimen particularity is the stability of the crack propagation under a force control.

  13. 2D ultrathin core-shell Pd@Ptmonolayer nanosheets: defect-mediated thin film growth and enhanced oxygen reduction performance

    NASA Astrophysics Data System (ADS)

    Wang, Wenxin; Zhao, Yunfeng; Ding, Yi

    2015-07-01

    An operational strategy for the synthesis of atomically smooth Pt skin by a defect-mediated thin film growth method is reported. Extended ultrathin core-shell structured d@Ptmonolayer nanosheets (thickness below 5 nm) exhibit nearly seven-fold enhancement in mass-activity and surprisingly good durability toward oxygen reduction reaction as compared with the commercial Pt/C catalyst.An operational strategy for the synthesis of atomically smooth Pt skin by a defect-mediated thin film growth method is reported. Extended ultrathin core-shell structured d@Ptmonolayer nanosheets (thickness below 5 nm) exhibit nearly seven-fold enhancement in mass-activity and surprisingly good durability toward oxygen reduction reaction as compared with the commercial Pt/C catalyst. Electronic supplementary information (ESI) available: Sample preparation, physical and electrochemical characterization, Fig. S1 to S11. See DOI: 10.1039/c5nr02748a

  14. What is the growth mode of ultrathin Co films on Pd(001)

    NASA Astrophysics Data System (ADS)

    Shi, Y. S.

    2016-12-01

    Thin Co films with varying thickness from 1 to 8 monolayers (ML) are epitaxially grown on Pd (001) and are studied in situ by using reflection high-energy electron diffraction (RHEED), scanning tunneling microscope (STM), low-energy electron diffraction (LEED), and magneto-optical Kerr effect (MOKE). The films take the layer-by-layer growth mode up to 3 ML, and then switch to the 3-dimensional growth mode afterward. For the as-grown films, MOKE measurements show that the easy axis of magnetism is in-plane and the interfacial Pd layer is magnetized. These results are confirmed and explained by density functional calculations.

  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. Mixed-mode static and fatigue crack growth in central notched and compact tension shear specimens

    SciTech Connect

    Shlyannikov, V.N.

    1999-07-01

    Elastic-plastic crack growth under mixed Mode I and 2 in six types of aluminum alloys and three types of steel were investigated. The experimental study of fatigue crack growth in six types of the aluminum alloys and one type of the steel is performed on biaxially loaded eight-petal specimens (EPS). All specimens for biaxial loading contained inclined through thickness central cracks. Mixed Mode I/2 static and fatigue crack growth experiments on the three types of steels and one type of the aluminum alloy used compact tension shear (CTS) specimens. Two approaches are developed for geometrical modeling of crack growth trajectories for the central notched and compact tension shear specimens respectively. The principal feature of such modeling is the determination of crack growth direction and the definition of crack length increment in this direction. On the basis of the analysis of the experimental data for the aluminum alloys and the steels an empirical crack reorientation criterion is suggested for both brittle and ductile materials. The damage process zone size concept is used for calculations and mixed-mode crack path. The influence of specimen geometry, biaxial loading and properties of the aluminum alloys and the steels on both crack growth direction and crack path at the macroscopic scale is discussed.

  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. Incubation time of heterogeneous growth of islands in the mode of incomplete condensation

    NASA Astrophysics Data System (ADS)

    Dubrovskii, V. G.

    2016-11-01

    The incubation time necessary for the growth of surface islands on heterogeneous nucleation centers to begin has been theoretically analyzed depending on the material gas flow and surface temperature. It is shown that, under heterogeneous growth in the mode of incomplete condensation, the incubation time increases with temperature according to the Arrhenius law and is inversely proportional to the flow, irrespective of the mechanism of diffusion transport to islands. The results obtained have been qualitatively compared with the experimental data on the incubation time for three-dimensional GaN islands arising in the initial stage of self-induced growth of GaN nanowires.

  20. A model for predicting crack growth rate for mixed mode fracture under biaxial loads

    NASA Astrophysics Data System (ADS)

    Shliannikov, V. N.; Braude, N. Z.

    1992-09-01

    A model for predicting the crack growth rate of an initially angled crack under biaxial loads of arbitrary direction is suggested. The model is based on a combination of both the Manson-Coffin equation for low cycle fatigue and the Paris equation for fatigue crack propagation. The model takes into consideration the change in material plastic properties in the region around the crack tip due to the stress state, together with the initial orientation of the crack and also its trajectory of growth. Predictions of crack growth rate for any mixed mode fracture is based on the results of uniaxial tension experiments.

  1. 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.

  2. 2-D Versus 3-D Magnetotelluric Data Interpretation

    NASA Astrophysics Data System (ADS)

    Ledo, Juanjo

    2005-09-01

    In recent years, the number of publications dealing with the mathematical and physical 3-D aspects of the magnetotelluric method has increased drastically. However, field experiments on a grid are often impractical and surveys are frequently restricted to single or widely separated profiles. So, in many cases we find ourselves with the following question: is the applicability of the 2-D hypothesis valid to extract geoelectric and geological information from real 3-D environments? The aim of this paper is to explore a few instructive but general situations to understand the basics of a 2-D interpretation of 3-D magnetotelluric data and to determine which data subset (TE-mode or TM-mode) is best for obtaining the electrical conductivity distribution of the subsurface using 2-D techniques. A review of the mathematical and physical fundamentals of the electromagnetic fields generated by a simple 3-D structure allows us to prioritise the choice of modes in a 2-D interpretation of responses influenced by 3-D structures. This analysis is corroborated by numerical results from synthetic models and by real data acquired by other authors. One important result of this analysis is that the mode most unaffected by 3-D effects depends on the position of the 3-D structure with respect to the regional 2-D strike direction. When the 3-D body is normal to the regional strike, the TE-mode is affected mainly by galvanic effects, while the TM-mode is affected by galvanic and inductive effects. In this case, a 2-D interpretation of the TM-mode is prone to error. When the 3-D body is parallel to the regional 2-D strike the TE-mode is affected by galvanic and inductive effects and the TM-mode is affected mainly by galvanic effects, making it more suitable for 2-D interpretation. In general, a wise 2-D interpretation of 3-D magnetotelluric data can be a guide to a reasonable geological interpretation.

  3. In situ investigation of growth modes during plasma-assisted molecular beam epitaxy of (0001) GaN

    SciTech Connect

    Koblmueller, G.; Fernandez-Garrido, S.; Calleja, E.; Speck, J. S.

    2007-10-15

    Real-time analysis of the growth modes during homoepitaxial (0001) GaN growth by plasma-assisted molecular beam epitaxy was performed using reflection high energy electron diffraction. A growth mode map was established as a function of Ga/N flux ratio and growth temperature, exhibiting distinct transitions between three-dimensional (3D), layer-by-layer, and step-flow growth modes. The layer-by-layer to step-flow growth transition under Ga-rich growth was surfactant mediated and related to a Ga adlayer coverage of one monolayer. Under N-rich conditions the transition from 3D to layer-by-layer growth was predominantly thermally activated, facilitating two-dimensional growth at temperatures of thermal decomposition.

  4. 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.

  5. A logical circuit for the regulation of fission yeast growth modes.

    PubMed

    Bähler, Jürg; Svetina, Sasa

    2005-11-21

    Growth of fission yeast at the ends of its cylindrical cells switches from a monopolar to a bipolar mode, before it ceases during mitosis and cell division. Here we assume that these growth modes correspond to three stable states of an underlying regulatory circuit, which is a relatively simple and to a large degree autonomous subsystem of an otherwise complex cellular control system. We develop a switch-like logical circuit based on three elements defined as binary variables. Effects of circuit variables on each other are expressed in terms of logical operations. We analyse this circuit for its behavior ("phenotypes") after removing single or multiple operations ("mutants"). Known fission yeast polarity mutants such as those defective in the switch to bipolar growth can be classified based on these predicted 'phenotypes'. Differences in growth patterns between daughter cells in different bipolar growth mutants are also predicted by the circuit model. The model presented here should provide a useful framework to guide future experiments into mechanisms of cellular polarity. This paper illustrates the usefulness of simple logical circuits to describe and dissect features of complex regulatory processes such as the fission yeast growth patterns in both wild type and mutant cells.

  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. 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.

  8. E-2D Advanced Hawkeye Aircraft (E-2D AHE)

    DTIC Science & Technology

    2015-12-01

    Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-364 E-2D Advanced Hawkeye Aircraft (E-2D AHE) As of FY 2017 President’s Budget Defense...Office Estimate RDT&E - Research, Development, Test, and Evaluation SAR - Selected Acquisition Report SCP - Service Cost Position TBD - To Be Determined

  9. Evidence for two growth modes during tungsten oxide vapor deposition on mica substrates

    NASA Astrophysics Data System (ADS)

    Mašek, Karel; Gillet, Marcel; Matolín, Vladimír

    2014-05-01

    The morphology, the structure and the orientation of tungsten oxide nanorods grown on mica are investigated as a function of the deposition time. The previous results are recalled to point out the changes with the nanorod thickness. The investigations were conducted by Atomic Force Microscopy (AFM) and Reflection High Energy Electron Diffraction (RHEED). The results evidence two successive growth modes. In the first stage thin and long nanorods were formed. They grew layer by layer with a hexagonal tungsten bronze structure and two different (1-10) and (2-10) planes parallel to the mica surface. In the second stage, as the deposition time increased thin nanorods with the (1-10) orientation grew in thickness when the others preserve their morphology and structure. In the discussion the difference between the two growth modes is emphasized. In the first stage the nanorod growth proceeds mainly by the surface diffusion of KxWO3 species. In the second stage the growth is due to the by direct impinging of WO3 molecules on some thin nanorods having already the (1-10) orientation, leading to growth of thick nanorods with a monoclinic structure.

  10. Characterization of Mode I fatigue crack growth in GFRP woven laminates at low temperatures

    SciTech Connect

    Shindo, Yasuhide . E-mail: shindo@material.tohoku.ac.jp; Inamoto, Akihiro; Narita, Fumio

    2005-03-01

    This paper describes an experimental and analytical study on the cryogenic fatigue behavior of glass fiber reinforced polymer woven laminates under Mode I loading. Fatigue crack growth rate tests were performed using compact tension specimens at room temperature, liquid nitrogen temperature (77 K), and liquid helium temperature (4 K). The fracture surfaces were also examined by scanning electron microscopy to correlate with the fatigue properties. A finite element method coupled with fatigue damage was adopted for the extensional analysis. The effects of temperature and loading condition on the fatigue crack growth rates are examined.

  11. Guided-mode refraction model for optical fiber sensing of surface crystal growth.

    PubMed

    Lamb, David W; Boerkamp, Martijn; Lye, Peter G

    2010-11-01

    An empirical "guided-mode refraction model" has been invoked to explain the optical attenuation of radiation in an exposed core optical fiber sensor subject to heterogeneous (surface) crystal growth. Based on Fresnel reflectance values at the internal fiber-crystal and crystal-solution interfaces, the model predictions agree with experimental observations of radial loss of radiation from the fiber core through the crystals as well as attenuation of guided radiation as a function of the radiation launch angle into the fiber.

  12. Source region and growth analysis of narrowband Z-mode emission at Saturn

    NASA Astrophysics Data System (ADS)

    Menietti, J. D.; Yoon, P. H.; Písa, D.; Ye, S.-Y.; Santolík, O.; Arridge, C. S.; Gurnett, D. A.; Coates, A. J.

    2016-12-01

    Intense Z-mode emission is observed in the lower density region near the inner edge of the Enceladus torus at Saturn, where these waves may resonate with MeV electrons. The source mechanism of this emission, which is narrow-banded and most intense near 5 kHz, is not well understood. We survey the Cassini Radio and Plasma Wave Science data to isolate several probable source regions near the inner edge of the Enceladus density torus. Electron phase space distributions are obtained from the Cassini Electron Spectrometer, part of the Cassini Plasma Spectrometer investigation. We perform a plasma wave growth analysis to conclude that an electron temperature anisotropy and possibly a weak loss cone can drive the Z mode as observed. Electrostatic electron acoustic waves and perhaps weak beam modes are also found to be unstable coincident with the Z mode. Quasi-steady conditions near the Enceladus density torus may result in the observations of narrowband Z-mode emission at Saturn.

  13. Growth modes in metal-organic molecular beam epitaxy of TiO{sub 2} on r-plane sapphire

    SciTech Connect

    Jalan, Bharat; Engel-Herbert, Roman; Cagnon, Joeel; Stemmer, Susanne

    2009-03-15

    Phase pure, epitaxial (101) rutile TiO{sub 2} films were grown on (012) sapphire substrates at temperatures between 485 and 725 deg. C using metal-organic molecular beam epitaxy with titanium tetraisopropoxide as the Ti source. Growth modes and rates were investigated as a function of substrate temperature using reflection high-energy electron diffraction, x-ray reflectivity, atomic force microscopy, and transmission electron microscopy. Growth rates were as high as 125 nm/h. The influence of additional oxygen supplied from a rf plasma source was investigated. Without oxygen plasma, the growth rate exhibited reaction and flux-limited regimes and layer-by-layer growth was observed in the initial stages of film growth. With oxygen plasma the growth rate became independent of temperature; films grew initially in step-flow mode and were insulating. The mechanisms for the different growth modes as a function of film thickness, temperature, and presence of oxygen are discussed.

  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. Linear growth rates of resistive tearing modes with sub-Alfvénic streaming flow

    SciTech Connect

    Wu, L. N.; Ma, Z. W.

    2014-07-15

    The tearing instability with sub-Alfvénic streaming flow along the external magnetic field is investigated using resistive MHD simulation. It is found that the growth rate of the tearing mode instability is larger than that without the streaming flow. With the streaming flow, there exist two Alfvén resonance layers near the central current sheet. The larger perturbation of the magnetic field in two closer Alfvén resonance layers could lead to formation of the observed cone structure and can largely enhance the development of the tearing mode for a narrower streaming flow. For a broader streaming flow, a larger separation of Alfvén resonance layers reduces the magnetic reconnection. The linear growth rate decreases with increase of the streaming flow thickness. The growth rate of the tearing instability also depends on the plasma beta (β). When the streaming flow is embedded in the current sheet, the growth rate increases with β if β < β{sub s}, but decreases if β > β{sub s}. The existence of the specific value β{sub s} can be attributed to competition between the suppressing effect of β and the enhancing effect of the streaming flow on the magnetic reconnection. The critical value β{sub s} increases with increase of the streaming flow strength.

  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. 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.

  19. Effect of Viscosity on Growth Rates of Interchange Modes in Magnetic Inertial Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Morse, R. L.; Nachtrieb, R.

    1999-11-01

    Thermal insulating B fields in imploding MIF/MTF confinement systems, as in predecessor static wall confinement systems, must close in the confined plasma and, therefore, have unfavorable curvature for MHD interchange mode stability. Analytic inviscid estimates with typical compressed z-pinch fields Bth=1MG, plasma density n=3.e20 and radius a=1cm give max. m=0 mode growth rates, Gm, of order 1.e8s-1 with wavelengths Lz of .1a to .5a. Thermal conduction to the confining wall increases B there and Gm significantly, as Vekstein discusses in concluding in effect that such confinement would not be useful for fusion. These growth rates and mode forms are confirmed by two supporting compressible models(Freidberg/McCrory). Happily when viscosity(Braginskii) is included; G is reduced, esp. at longer wavelengths, Lz, with scaling Lz**-1, and viscosities of 1e2 to 1e4 poise for the example plasmas give Gm's of order 1.e7s-1 and less with realistic time dependent profiles. We conclude that these Gm's are consistent with significant fusion yields. This work was presented at the UCLA/DoE ICC conference, 3/3-6/97.

  20. The contribution of feeding mode to obesogenic growth trajectories in American Samoan infants

    PubMed Central

    Hawley, Nicola L; Johnson, William; Nu’usolia, Ofeira; McGarvey, Stephen T

    2013-01-01

    Background Samoans are recognized for their particularly high body mass index and prevalent adult obesity but infants are understudied. Objective To examine the prevalence of overweight and obesity and determine the contribution of feeding mode to obesogenic growth trajectories in American Samoan infants. Methods Data were extracted from the well baby records of 795 (n=417 male) Samoan infants aged 0-15 months. Mixed-effects growth models were used to produce individual weight and length curves. Further mixed-effects models were fitted with feeding mode (breastfed, formula- or mixed-fed) as a single observation at age four (±2) months. Weight and length values were converted to Z-scores according to the CDC 2000 reference. Results At 15 months, 23.3% of boys and 16.7% of girls were obese (weight-for-length > 95th percentile). Feeding mode had a significant effect on weight and length trajectories. Formula-fed infants gained weight and length faster than breastfed infants. Formula-fed boys were significantly more likely to be obese at 15 months (38.6%) than breastfed boys (23.4%), χ2=8.4, P<0.01, odds ratio=2.05, 95% CI [1.04, 4.05]. Conclusion Obesity in American Samoans is not confined to adults. Obesity prevention efforts should be targeted at early life and promotion of breastfeeding may be a suitable intervention target. PMID:23386576

  1. Interface chemistry and epitaxial growth modes of SrF2 on Si(001)

    NASA Astrophysics Data System (ADS)

    Pasquali, L.; Suturin, S. M.; Kaveev, A. K.; Ulin, V. P.; Sokolov, N. S.; Doyle, B. P.; Nannarone, S.

    2007-02-01

    Molecular beam epitaxy has been used to grow SrF2 thin films on Si(001). The growth modes have been investigated by atomic force microscopy, electron diffraction, and photoemission. Two principal growth regimes have been identified: (i) when deposition is carried out with the substrate held at a temperature of 700-750°C , SrF2 molecules react with the substrate giving rise to a Sr-rich wetting layer on top of which three dimensional bulklike fluoride ridges develop; (ii) when deposition is carried out with the substrate held at 400°C , a nanopatterned film forms with characteristic triangular islands. Results are compared to the growth mode of CaF2 on Si(001) under analogous deposition conditions. Morphological and structural differences between the two systems are associated with the larger lattice parameter of SrF2 with respect to CaF2 , resulting in a larger mismatch with the Si substrate.

  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.

    1997-04-15

    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.

  3. 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.

  4. 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.}

  5. Non-equilibrium atomic condensates and mixtures: collective modes, condensate growth and thermalisation

    NASA Astrophysics Data System (ADS)

    Loon Lee, Kean; Proukakis, Nick P.

    2016-11-01

    The non-equilibrium dynamics of trapped ultracold atomic gases, or mixtures thereof, is an extremely rich subject. Despite 20 years of studies, and remarkable progress mainly on the experimental front, numerous open question remain, related to the growth, relaxation and thermalisation of such systems, and there is still no universally accepted theory for their theoretical description. In this paper we discuss one of the state-of-the-art kinetic approaches, which gives an intuitive picture of the physical processes happening at the microscopic scale, being broadly applicable both below and above the critical region (but not within the critical region itself, where fluctuations become dominant and symmetry breaking takes place). Specifically, the ‘Zaremba-Nikuni-Griffin’ (ZNG) scheme provides a self-consistent description of the coupling between the condensate and the thermal atoms, including the collisions between these two subsystems. It has been successfully tested against experiments in various settings, including investigation of collective modes (e.g. monopole, dipole and quadrupole modes), dissipation of topological excitations (solitons and vortices) as well as surface evaporative cooling. Here, we show that the ZNG model can capture two important aspects of non-equilibrium dynamics for both single-component and two-component BECs: the Kohn mode (the undamped dipole oscillation independent of interactions and temperature) and (re)thermalisation leading to condensate growth following sudden evaporation. Our simulations, performed in a spherically symmetric trap reveal (i) an interesting two-stage dynamics and the emergence of a prominent monopole mode in the evaporative cooling of a single-component Bose gas, and (ii) the long thermalisation time associated with the sympathetic cooling of a realistic two-component mixture. Related open questions arise about the mechanisms and the nature of thermalisation in such systems, where further controlled

  6. Controlled Growth of one-dimensional zinc oxide nanostructures in the pulsed electrodeposition mode

    SciTech Connect

    Klochko, N. P. Khrypunov, G. S.; Myagchenko, Yu. O.; Melnychuk, E. E.; Kopach, V. R.; Klepikova, E. S.; Lyubov, V. M.; Kopach, A. V.

    2012-06-15

    Zinc oxide nanostructures are objects of study in the field of optoelectronics, solar power engineering, nanosensorics, and catalysis. For the purpose of the controlled growth of one-dimensional submicrometer zinc oxide structures in the pulsed electrodeposition mode, the effect of the pulse electrolysis parameters on the morphology of ZnO layers, their optical properties, and structural and substructural characteristics is determined using X-ray diffraction, optical spectrophotometry, and atomic-force microscopy. The possibility of fabricating arrays of ZnO nanowires with different geometrical shapes, perpendicular to the substrate surface, by varying the frequency of cathode-substrate potential pulses is shown.

  7. Characterization of debond growth mechanism in adhesively bonded composites under mode II static and fatigue loadings

    NASA Technical Reports Server (NTRS)

    Mall, S.; Kochhar, N. K.

    1988-01-01

    An experimental investigation of adhesively bonded composite joint was conducted to characterize the debond growth mechanism under mode II static and fatigue loadings. For this purpose, end-notched flexure specimens of graphite/epoxy (T300/5208) adherends bonded with EC 3445 adhesive were tested. In all specimen tested, the fatigue failure occurred in the form of cyclic debonding. The present study confirmed the result of previous studies that total strain-energy-release rate is the driving parameter for cyclic debonding. Further, the debond growth resistance under cyclic loading with full shear reversal (i.e., stress ratio, R = -1) is drastically reduced in comparison to the case when subjected to cyclic shear loading with no shear reversal (i.e., R = 0.1).

  8. Optoelectronics with 2D semiconductors

    NASA Astrophysics Data System (ADS)

    Mueller, Thomas

    2015-03-01

    Two-dimensional (2D) atomic crystals, such as graphene and layered transition-metal dichalcogenides, are currently receiving a lot of attention for applications in electronics and optoelectronics. In this talk, I will review our research activities on electrically driven light emission, photovoltaic energy conversion and photodetection in 2D semiconductors. In particular, WSe2 monolayer p-n junctions formed by electrostatic doping using a pair of split gate electrodes, type-II heterojunctions based on MoS2/WSe2 and MoS2/phosphorene van der Waals stacks, 2D multi-junction solar cells, and 3D/2D semiconductor interfaces will be presented. Upon optical illumination, conversion of light into electrical energy occurs in these devices. If an electrical current is driven, efficient electroluminescence is obtained. I will present measurements of the electrical characteristics, the optical properties, and the gate voltage dependence of the device response. In the second part of my talk, I will discuss photoconductivity studies of MoS2 field-effect transistors. We identify photovoltaic and photoconductive effects, which both show strong photoconductive gain. A model will be presented that reproduces our experimental findings, such as the dependence on optical power and gate voltage. We envision that the efficient photon conversion and light emission, combined with the advantages of 2D semiconductors, such as flexibility, high mechanical stability and low costs of production, could lead to new optoelectronic technologies.

  9. Effect of pressure on the semipolar GaN (10-11) growth mode on patterned Si substrates

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Ming; Zhang, Jie; Lin, Wen-Yu; Ye, Meng-Xin; Feng, Xiang-Xu; Zhang, Dong-Yan; Steve, Ding; Xu, Chen-Ke; Liu, Bao-Lin

    2015-05-01

    In this paper, we investigate the effect of pressure on the growth mode of high quality (10-11) GaN using an epitaxial lateral over growth (ELO) technique by metal organic chemical vapor deposition (MOCVD). Two pressure growth conditions, high pressure (HP) 1013 mbar and low pressure growth (LP) 500 mbar, are employed during growth. In the high pressure growth conditions, the crystal quality is improved by decreasing the dislocation and stack fault density in the strip connection locations. The room temperature photoluminescence measurement also shows that the light emission intensity increases three times using the HP growth condition compared with that using the LP growth conditions. In the low temperature (77 K) photoluminescence, the defects-related peaks are very obvious in the low pressure growth samples. This result also indicates that the crystal quality is improved using the high pressure growth conditions. Project support by the National High Technology Research and Development Program of China (Green Laser).

  10. Initial Single-Mode Rayleigh-Taylor Growth Rates Measured with the OMEGA Laser System

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.; Meyerhofer, D. D.; Boehly, T. R.; Ofer, D.; Verdon, C. P.; Bradley, D. K.; McKenty, P. W.; Smalyuk, V. A.

    1996-11-01

    A series of single-mode growth measurements done with the OMEGA laser system are reported. These measurements were done to qualify the laser irradiation and diagnostic suite for future experiments that will use the growth of perturbations at the ablation interface to quantify improvements in irradiation uniformity, reduced growth due to increased ablation velocities, and the effect of increased density scale lengths on the growth rate at the ablation interface. This series of measurements used a laser intensity of 2 × 10^14 W/cm^2 over a spot size of 700 μm for both Gaussian and non-Gaussian shaped pulses with an rms irradiation nonuniformity of 7%. Data were collected with a gated x-ray framing camera with a 10-μm spatial resolution and a 40-ps temporal resolution. This work was supported by the U. S. Department of Energy Office of Inertial Confinement Fusion under cooperative Agreement No. DE-FC03-92SF19460.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    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.

  13. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Lin, Jerry

    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. The 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.

  14. Temperature-gradient epitaxy under in situ growth mode diagnostics by scanning reflection high-energy electron diffraction

    NASA Astrophysics Data System (ADS)

    Koida, T.; Komiyama, D.; Koinuma, H.; Ohtani, M.; Lippmaa, M.; Kawasaki, M.

    2002-01-01

    We have developed a parallel film growth method on a temperature-gradient substrate to quickly control and optimize the film growth mode. A continuous-wave neodymium-doped yttrium-aluminum-garnet laser heating was used to achieve a stable temperature gradient covering a 300 °C range of temperatures over a distance of 11 mm. The growth mode was determined by time-resolved scanning reflection high-energy electron diffraction. Transition from layer-by-layer to step-flow growth by the deposition temperature was observed during La0.5Sr0.5MnO3 film growth on a single SrTiO3 substrate, proving a powerful tool not only for investigating the growth dynamics but also for seeking the optimized deposition conditions in one run of experiment.

  15. Highly crystalline 2D superconductors

    NASA Astrophysics Data System (ADS)

    Saito, Yu; Nojima, Tsutomu; Iwasa, Yoshihiro

    2016-12-01

    Recent advances in materials fabrication have enabled the manufacturing of ordered 2D electron systems, such as heterogeneous interfaces, atomic layers grown by molecular beam epitaxy, exfoliated thin flakes and field-effect devices. These 2D electron systems are highly crystalline, and some of them, despite their single-layer thickness, exhibit a sheet resistance more than an order of magnitude lower than that of conventional amorphous or granular thin films. In this Review, we explore recent developments in the field of highly crystalline 2D superconductors and highlight the unprecedented physical properties of these systems. In particular, we explore the quantum metallic state (or possible metallic ground state), the quantum Griffiths phase observed in out-of-plane magnetic fields and the superconducting state maintained in anomalously large in-plane magnetic fields. These phenomena are examined in the context of weakened disorder and/or broken spatial inversion symmetry. We conclude with a discussion of how these unconventional properties make highly crystalline 2D systems promising platforms for the exploration of new quantum physics and high-temperature superconductors.

  16. Extensions of 2D gravity

    SciTech Connect

    Sevrin, A.

    1993-06-01

    After reviewing some aspects of gravity in two dimensions, I show that non-trivial embeddings of sl(2) in a semi-simple (super) Lie algebra give rise to a very large class of extensions of 2D gravity. The induced action is constructed as a gauged WZW model and an exact expression for the effective action is given.

  17. 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

  18. 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.

  19. 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.

  20. Growth mode and defect evaluation of GaSb on GaAs substrate: a transmission electron microscopy study.

    PubMed

    Huang, Shenghong; Balakrishnan, Ganesh; Huffaker, Diana L

    2011-06-01

    We use transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques to confirm and analyze the interfacial misfit (IMF) and non-IMF growth modes for GaSb epilayers on GaAs substrates. Under optimized IMF growth conditions, only pure 90 degrees dislocations are generated along both [110] and [1-10] directions and located exactly at the epi-substrate interface, which leads to very low density of misfit dislocations propagating from the GaSb/GaAs interface along the growth direction, compared to the non-IMF growth condition. The mechanism of defect annihilation indicates that this IMF mergence process happens without formation of threading dislocations into the GaSb epilayer, which is a completely relaxed growth mode with extremely low defect density. Based on scanning several sets of wafer surfaces, plan-view TEM confirms that the misfit defect densities are estimated to be approximately 5 x 10(5) cm(-2) for IMF growth mode and approximately 10(9) cm(-2) for non-IMF growth mode.

  1. Anisotropic 2D Materials for Tunable Hyperbolic Plasmonics.

    PubMed

    Nemilentsau, Andrei; Low, Tony; Hanson, George

    2016-02-12

    Motivated by the recent emergence of a new class of anisotropic 2D materials, we examine their electromagnetic modes and demonstrate that a broad class of the materials can host highly directional hyperbolic plasmons. Their propagation direction can be manipulated on the spot by gate doping, enabling hyperbolic beam reflection, refraction, and bending. The realization of these natural 2D hyperbolic media opens up a new avenue in dynamic control of hyperbolic plasmons not possible in the 3D version.

  2. 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.

  3. Axial-bundle phases--new modes of 2D, 3D, and helical columnar self-assembly in liquid crystalline phases of bolaamphiphiles with swallow tail lateral chains.

    PubMed

    Prehm, Marko; Liu, Feng; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2011-04-06

    Two series of polyphilic molecules composed of a rigid and linear p-terphenyl core, terminated at both ends with polar glycerol groups capable of hydrogen bonding, and two branched swallow tail-type lateral chains, composed of a fluorinated and a nonfluorinated branch or two fluorinated branches, were synthesized and investigated by differential scanning calorimetry, polarizing microscopy, and X-ray diffraction (XRD) with respect to their self-assembly in thermotropic liquid crystalline (LC) phases. Hexagonal columnar phases were formed by all molecules, at least at the highest temperature. In these phases the columns are composed of a core of aromatic rods and an aliphatic shell. The aromatic rods form bundles which are rotationally averaged and lie parallel to the column long axis. This unique organization is proven by different optical and XRD methods. The aromatic and glycerol groups inside the rod bundles are segregated into alternating segments. Depending on temperature and molecular structure, long-range intercolumnar correlation of this periodicity could take place, leading to a 3D-ordered LC phase with rhombohedral R ̄3m symmetry. The bundles are embedded in the matrix of the lateral chains, which is divided into fluoroalkyl- and aliphatic-rich regions. In the 2D columnar phase the fluorinated regions take the form of either straight columns running along the edges of the hexagonal Voronoi cells or, for compounds with a higher degree of fluorination, fuse to a hexagonal honeycomb enclosing the aromatic cores. In the R ̄3m phase the fluorine-rich chains are preferentially found along right- and left-handed helices wound around the 3(1) screw axes between the main aromatic columns.

  4. 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

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

    PubMed

    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.

  6. Linear growth rates of types I and II convective modes within the rotating-cone boundary layer

    NASA Astrophysics Data System (ADS)

    Garrett, S. J.

    2010-04-01

    Experimental observations have shown that the transition characteristics of the boundary-layer flow over rotating cones depends on the cone half-angle. In particular, pairs of counter-rotating Görtler-type vortices are observed over cones with slender half-angles and co-rotating vortices are observed over broad cones. Garrett et al (2009 J. Fluid Mech. 622 209-32) have hypothesized the existence of a centrifugal instability mode over slender cones that is more dangerous than the types I (crossflow) and II (streamline curvature) modes which dominate over rotating disks and broad cones. Work is currently underway to clarify this alternative mode; however, a clear understanding of the growth rates of types I and II modes is crucial to the ultimate understanding of how the dominant mode changes with half-angle. In this paper, we demonstrate that the maximum growth rate for types I and II modes decreases with reduced half-angle, which clears the way for the dominance of the alternative instability mode. Furthermore, it is suggested that vortices travelling at 75% of the cone surface speed will be selected over smooth, clean rotating cones with half-angle such that the type I mode is dominant. Interestingly, this vortex speed has been experimentally observed by Kobayashi and Arai within the rotating-sphere boundary layer.

  7. Surface structures and growth mode for the {Cu}/{Si(110)} surfaces depending on heat treatment

    NASA Astrophysics Data System (ADS)

    Ikeda, T.; Kawashima, Y.; Itoh, H.; Ichinokawa, T.

    1995-11-01

    The surface structures and growth mode for the {Cu}/{Si(110)} surfaces depending on Cu segregation by heat treatment have been studied with low energy electron diffraction (LEED), Auger electron spectroscopy (AES), isothermal desorption spectroscopy (ITDS), and scanning electron microscopy (SEM). At room temperature, Cu was intermixed with Si and no defined interface structure was observed at coverages higher than 2 ML. However, the growth mode of the {Cu}/{Si(110)} surface above 400°C is the Stranski-Krastanov type and a part of Cu atoms deposited on the surface diffuse into the bulk above 400°C in addition to the island formation on the surface. The Cu atoms diffusing into the bulk are segregated to the surface by quenching and the segregated Cu atoms form several new structures depending on quenching temperature and annealing time. The 2 × 1, 4 × 5, 4 × 3, and 6 × 6 structures were found by LEED in the ranges of {Cu}/{Si} Auger ratios, 0.01-0.04, 0.04-0.06, 0.06-0.1, and 0.1-0.2, respectively. There are one to one correspondences between surface structures and surface Cu concentrations. The islands nucleated on the surface at Cu 10 ML above 800°C are rectangular with a composition of Cu3Si. The segregation of Cu to the surface by quenching and the trapping of Cu to islands by annealing are discussed with comparing to those of the {Cu}/{Si(100)} surfaces.

  8. 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

  9. [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).

  10. 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).

  11. On new non-modal hydrodynamic stability modes and resulting non-exponential growth rates - a Lie symmetry approach

    NASA Astrophysics Data System (ADS)

    Oberlack, Martin; Nold, Andreas; Sanjon, Cedric Wilfried; Wang, Yongqi; Hau, Jan

    2016-11-01

    Classical hydrodynamic stability theory for laminar shear flows, no matter if considering long-term stability or transient growth, is based on the normal-mode ansatz, or, in other words, on an exponential function in space (stream-wise direction) and time. Recently, it became clear that the normal mode ansatz and the resulting Orr-Sommerfeld equation is based on essentially three fundamental symmetries of the linearized Euler and Navier-Stokes equations: translation in space and time and scaling of the dependent variable. Further, Kelvin-mode of linear shear flows seemed to be an exception in this context as it admits a fourth symmetry resulting in the classical Kelvin mode which is rather different from normal-mode. However, very recently it was discovered that most of the classical canonical shear flows such as linear shear, Couette, plane and round Poiseuille, Taylor-Couette, Lamb-Ossen vortex or asymptotic suction boundary layer admit more symmetries. This, in turn, led to new problem specific non-modal ansatz functions. In contrast to the exponential growth rate in time of the modal-ansatz, the new non-modal ansatz functions usually lead to an algebraic growth or decay rate, while for the asymptotic suction boundary layer a double-exponential growth or decay is observed.

  12. Population growth rate responses of Ceriodaphnia dubia to ternary mixtures of specific acting chemicals: pharmacological versus ecotoxicological modes of action.

    PubMed

    Barata, Carlos; Fernández-San Juan, María; Feo, Maria Luisa; Eljarrrat, Ethel; Soares, Amadeu M V M; Barceló, Damià; Baird, Donald J

    2012-09-04

    When considering joint toxic apical effects at higher levels of biological organization, such as the growth of populations, the so-called pharmacological mode of action that relies on toxicological mechanistic effects on molecular target sites may not be relevant. Such effects on population growth rate will depend on the extent to which juvenile and adult survival rates and production rates (juvenile developmental rates and reproduction) are affected by toxic exposure and also by the sensitivity of population growth rates to life-history changes. In such cases, the ecotoxicological mode of action, defined as the crucial life-history trait processes and/or xenobiotic-life-history trait interactions underlying a toxicological effect on population growth rate, should be considered. Life-table response experiments with the crustacean Ceriodaphnia dubia exposed to single and ternary mixtures of nine compounds were conducted to test the hypothesis that joint effects on population growth rates could be predicted from the mixture constituent ecotoxicological mode of action. Joint effects of mixtures containing pharmacologically dissimilar compounds (cadmium, λ-cyhalothrin, and chlorpyrifos) that differentially affected life-history traits contributing to population growth rates were accurately predicted by the independent-action concept. Conversely, the concentration-addition concept accurately predicted joint effects of two different mixtures: one containing pharmacologically similar acting pyrethroids that also affected similarly life-history traits, the other one that included pharmacologically dissimilar compounds (3,4-dichloroaniline, sodium bromide, and fenoxycarb) acting mainly on reproduction rates. These results indicate that when assessing combined effects on population growth rate responses, selection of mixture toxicity conceptual models based on the ecotoxicological mode of action of mixture constituents provided more accurate predictions than those based on

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

    NASA Astrophysics Data System (ADS)

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

  14. A 2D-QSAR and Grid-Independent Molecular Descriptor (GRIND) Analysis of Quinoline-Type Inhibitors of Akt2: Exploration of the Binding Mode in the Pleckstrin Homology (PH) Domain

    PubMed Central

    Akhtar, Noreen; Jabeen, Ishrat

    2016-01-01

    Protein kinase B-β (PKBβ/Akt2) is a serine/threonine-specific protein kinase that has emerged as one of the most important regulators of cell growth, differentiation, and division. Upregulation of Akt2 in various human carcinomas, including ovarian, breast, and pancreatic, is a well-known tumorigenesis phenomenon. Early on, the concept of the simultaneous administration of anticancer drugs with inhibitors of Akt2 was advocated to overcome cell proliferation in the chemotherapeutic treatment of cancer. However, clinical studies have not lived up to the high expectations, and several phase II and phase III clinical studies have been terminated prematurely because of severe side effects related to the non-selective isomeric inhibition of Akt2. The notion that the sequence identity of pleckstrin homology (PH) domains within Akt-isoforms is less than 30% might indicate the possibility of the development of selective antagonists against the Akt2 PH domain. Therefore, in this study, various in silico tools were utilized to explore the hypothesis that quinoline-type inhibitors bind in the Akt2 PH domain. A Grid-Independent Molecular Descriptor (GRIND) analysis indicated that two hydrogen bond acceptors, two hydrogen bond donors and one hydrophobic feature at a certain distance from each other were important for the selective inhibition of Akt2. Our docking results delineated the importance of Lys30 as an anchor point for mapping the distances of important amino acid residues in the binding pocket, including Lys14, Glu17, Arg25, Asn53, Asn54 and Arg86. The binding regions identified complement the GRIND-based pharmacophoric features. PMID:28036396

  15. Phonon thermal conduction in novel 2D materials

    NASA Astrophysics Data System (ADS)

    Xu, Xiangfan; Chen, Jie; Li, Baowen

    2016-12-01

    Recently, there has been increasing interest in phonon thermal transport in low-dimensional materials, due to the crucial importance of dissipating and managing heat in micro- and nano-electronic devices. Significant progress has been achieved for one-dimensional (1D) systems, both theoretically and experimentally. However, the study of heat conduction in two-dimensional (2D) systems is still in its infancy due to the limited availability of 2D materials and the technical challenges of fabricating suspended samples that are suitable for thermal measurements. In this review, we outline different experimental techniques and theoretical approaches for phonon thermal transport in 2D materials, discuss the problems and challenges of phonon thermal transport measurements and provide a comparison between existing experimental data. Special attention will be given to the effects of size, dimensionality, anisotropy and mode contributions in novel 2D systems, including graphene, boron nitride, MoS2, black phosphorous and silicene.

  16. Phonon thermal conduction in novel 2D materials.

    PubMed

    Xu, Xiangfan; Chen, Jie; Li, Baowen

    2016-12-07

    Recently, there has been increasing interest in phonon thermal transport in low-dimensional materials, due to the crucial importance of dissipating and managing heat in micro- and nano-electronic devices. Significant progress has been achieved for one-dimensional (1D) systems, both theoretically and experimentally. However, the study of heat conduction in two-dimensional (2D) systems is still in its infancy due to the limited availability of 2D materials and the technical challenges of fabricating suspended samples that are suitable for thermal measurements. In this review, we outline different experimental techniques and theoretical approaches for phonon thermal transport in 2D materials, discuss the problems and challenges of phonon thermal transport measurements and provide a comparison between existing experimental data. Special attention will be given to the effects of size, dimensionality, anisotropy and mode contributions in novel 2D systems, including graphene, boron nitride, MoS2, black phosphorous and silicene.

  17. 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

  18. Growth and smolting in lower-mode Atlantic Salmon stocked into the Penobscot River, Maine

    USGS Publications Warehouse

    Zydlewski, Joseph; O'Malley, Andrew; Cox, Oliver; Ruksznis, Peter; Trial, Joan G.

    2014-01-01

    Restoration of Atlantic Salmon Salmo salar in Maine has relied on hatchery-produced fry and smolts for critical stocking strategies. Stocking fry minimizes domestication selection, but these fish have poor survival. Conversely, stocked smolts have little freshwater experience but provide higher adult returns. Lower-mode (LM) fish, those not growing fast enough to ensure smolting by the time of stocking, are a by-product of the smolt program and are an intermediate hatchery product. From 2002 to 2009, between 70,000 and 170,000 marked LM Atlantic Salmon were stocked into the Pleasant River (a tributary in the Penobscot River drainage, Maine) in late September to early October. These fish were recaptured as actively migrating smolts (screw trapping), as nonmigrants (electrofishing), and as returning adults to the Penobscot River (Veazie Dam trap). Fork length (FL) was measured and a scale sample was taken to retrospectively estimate FL at winter annulus one (FW1) using the intercept-corrected direct proportion model. The LM fish were observed to migrate as age-1, age-2, and infrequently as age-3 smolts. Those migrating as age-1 smolts had a distinctly larger estimated FL at FW1 (>112 mm) than those that remained in the river for at least one additional year. At the time of migration, age-2 and age-3 smolts were substantially larger than age-1 smolts. Returning adult Atlantic Salmon of LM origin had estimated FLs at FW1 that corresponded to smolt age (greater FL for age 1 than age 2). The LM product produces both age-1 and age-2 smolts that have greater freshwater experience than hatchery smolts and may have growth and fitness advantages. The data from this study will allow managers to better assess the probability of smolting age and manipulate hatchery growth rates to produce a targeted-size LM product.

  19. Valleytronics in 2D materials

    NASA Astrophysics Data System (ADS)

    Schaibley, John R.; Yu, Hongyi; Clark, Genevieve; Rivera, Pasqual; Ross, Jason S.; Seyler, Kyle L.; Yao, Wang; Xu, Xiaodong

    2016-11-01

    Semiconductor technology is currently based on the manipulation of electronic charge; however, electrons have additional degrees of freedom, such as spin and valley, that can be used to encode and process information. Over the past several decades, there has been significant progress in manipulating electron spin for semiconductor spintronic devices, motivated by potential spin-based information processing and storage applications. However, experimental progress towards manipulating the valley degree of freedom for potential valleytronic devices has been limited until very recently. We review the latest advances in valleytronics, which have largely been enabled by the isolation of 2D materials (such as graphene and semiconducting transition metal dichalcogenides) that host an easily accessible electronic valley degree of freedom, allowing for dynamic control.

  20. Unparticle example in 2D.

    PubMed

    Georgi, Howard; Kats, Yevgeny

    2008-09-26

    We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.

  1. Steady-state crack growth in single crystals under Mode I loading

    NASA Astrophysics Data System (ADS)

    Juul, K. J.; Nielsen, K. L.; Niordson, C. F.

    The active plastic zone that surrounds the tip of a sharp crack growing under plane strain Mode I loading conditions at a constant velocity in a single crystal is studied. Both the characteristics of the plastic zone and its effect on the macroscopic toughness is investigated in terms of crack tip shielding due to plasticity (quantified by employing the Suo, Shih, and Varias set-up). Three single crystals (FCC, BCC, HCP) are modelled in a steady-state elastic visco-plastic framework, with emphasis on the influence of rate-sensitivity and crystal structures. Distinct velocity discontinuities at the crack tip predicted by Rice [Rice J.R., 1987. Tensile crack tip fields in elastic-ideally plastic crystals. Mech. Mater. 6, pp. 317-335] for quasi-static crack growth are confirmed through the numerical simulations and highly refined details are revealed. Through a detailed study, it is demonstrated that the largest shielding effect develops in HCP crystals, while the lowest shielding exists for FCC crystals. Rate-sensitivity is found to affect the plastic zone size, but the characteristics overall remain similar for each individual crystal structure. An increasing rate-sensitivity at low crack velocities monotonically increases the crack tip shielding, whereas the opposite behaviour is observed at high velocities. This observation leads to the existence of a characteristic velocity at which the crack tip shielding becomes independent of the rate-sensitivity.

  2. Permanent neonatal diabetes mellitus: epidemiology, mode of presentation, pathogenesis and growth.

    PubMed

    Soliman, A T; elZalabany, M M; Bappal, B; alSalmi, I; de Silva, V; Asfour, M

    1999-01-01

    Permanent neonatal diabetes mellitus (PNIDDM) is a rare form of IDDM with unclear etiology and pathogenesis. We determined the incidence and prevalence rates and studied the clinical and biochemical features of PNIDDM in the Sultanate of Oman. The mean incidence rate during the study period from January 1989 to December 1994 was 1.788 +/- 0.82 per 100,000 live births per year. At the end of December 1994 the prevalence rate was 2.4 per 100,000 children below the age of 5 years. They constituted 41.6% of all cases of IDDM in this age group. Diarrhoea, fever, lethargy, poor feeding and failure to thrive were the most common presenting symptoms. Dehydration and tachypnoea were the most common signs. All patients who developed IDDM during the neonatal period had intrauterine growth retardation and 4.5 presented with diabetic ketoacidosis (plasma glucose 37 +/- 9 mmol/L, pH 7.12 +/- 0.1). Hypertriglyceridemia was a constant feature (19.4 +/- 4.8 mmol/L). They were products of consanguineous marriage with significantly high prevalence of IDDM and NIDDM in their family members. None of the infants had clinical or immunological evidence of congenital viral infection. Three of the five children had HLA-DR2, the diabetes resistance alleles. C-peptide secretion was absent during and after metabolic control of hyperglycemia in all the studied infants and none had circulating islet cell antibody at presentation or during the first year after diagnosis. Despite marked growth retardation at birth, there was a significant improvement of growth after initiating insulin therapy. Four of the 5 patients had normal developmental milestones, one had mild developmental delay following a severe and prolonged attack of hypoglycemia. None of the patients had exocrine pancreatic deficiency. In summary, the very high rate of parental consanguinity, occurrence in both sexes and in two siblings in the same family, absence of islet cell antibodies and the presence of HLA-DR2 loci in 3/5 of

  3. Quantum coherence selective 2D Raman–2D electronic spectroscopy

    PubMed Central

    Spencer, Austin P.; Hutson, William O.; Harel, Elad

    2017-01-01

    Electronic and vibrational correlations report on the dynamics and structure of molecular species, yet revealing these correlations experimentally has proved extremely challenging. Here, we demonstrate a method that probes correlations between states within the vibrational and electronic manifold with quantum coherence selectivity. Specifically, we measure a fully coherent four-dimensional spectrum which simultaneously encodes vibrational–vibrational, electronic–vibrational and electronic–electronic interactions. By combining near-impulsive resonant and non-resonant excitation, the desired fifth-order signal of a complex organic molecule in solution is measured free of unwanted lower-order contamination. A critical feature of this method is electronic and vibrational frequency resolution, enabling isolation and assignment of individual quantum coherence pathways. The vibronic structure of the system is then revealed within an otherwise broad and featureless 2D electronic spectrum. This method is suited for studying elusive quantum effects in which electronic transitions strongly couple to phonons and vibrations, such as energy transfer in photosynthetic pigment–protein complexes. PMID:28281541

  4. Quantum coherence selective 2D Raman-2D electronic spectroscopy

    NASA Astrophysics Data System (ADS)

    Spencer, Austin P.; Hutson, William O.; Harel, Elad

    2017-03-01

    Electronic and vibrational correlations report on the dynamics and structure of molecular species, yet revealing these correlations experimentally has proved extremely challenging. Here, we demonstrate a method that probes correlations between states within the vibrational and electronic manifold with quantum coherence selectivity. Specifically, we measure a fully coherent four-dimensional spectrum which simultaneously encodes vibrational-vibrational, electronic-vibrational and electronic-electronic interactions. By combining near-impulsive resonant and non-resonant excitation, the desired fifth-order signal of a complex organic molecule in solution is measured free of unwanted lower-order contamination. A critical feature of this method is electronic and vibrational frequency resolution, enabling isolation and assignment of individual quantum coherence pathways. The vibronic structure of the system is then revealed within an otherwise broad and featureless 2D electronic spectrum. This method is suited for studying elusive quantum effects in which electronic transitions strongly couple to phonons and vibrations, such as energy transfer in photosynthetic pigment-protein complexes.

  5. Quantum coherence selective 2D Raman-2D electronic spectroscopy.

    PubMed

    Spencer, Austin P; Hutson, William O; Harel, Elad

    2017-03-10

    Electronic and vibrational correlations report on the dynamics and structure of molecular species, yet revealing these correlations experimentally has proved extremely challenging. Here, we demonstrate a method that probes correlations between states within the vibrational and electronic manifold with quantum coherence selectivity. Specifically, we measure a fully coherent four-dimensional spectrum which simultaneously encodes vibrational-vibrational, electronic-vibrational and electronic-electronic interactions. By combining near-impulsive resonant and non-resonant excitation, the desired fifth-order signal of a complex organic molecule in solution is measured free of unwanted lower-order contamination. A critical feature of this method is electronic and vibrational frequency resolution, enabling isolation and assignment of individual quantum coherence pathways. The vibronic structure of the system is then revealed within an otherwise broad and featureless 2D electronic spectrum. This method is suited for studying elusive quantum effects in which electronic transitions strongly couple to phonons and vibrations, such as energy transfer in photosynthetic pigment-protein complexes.

  6. 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.

  7. 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.

  8. Effects of adhesion layer on Ag nanorod growth mode and morphology using glancing angle physical vapor deposition

    NASA Astrophysics Data System (ADS)

    Davies, Matthew P.; McKinney, Casey S.; Serrano, Joel M.; Mullen, Thomas J.; Stagon, Stephen P.

    2017-01-01

    This letter reports on the transition from a non-wetting to an effectively wetting growth mode of silver (Ag) nanorods when an adhesion layer is used during glancing angle physical vapor deposition growth. When deposited onto a silicon substrate without an adhesion layer, Ag nanorods grow from partially interconnected non-wetting islands with diameters of ˜100 nm, although many connect with their neighbors due to small rod-to-rod spacing. When a 1 nm thick Cr adhesion layer is used, which is shown not to completely coat the substrate, the growth mode becomes effectively wetting through the coalescence of closely spaced nuclei, and both Ag nanorod diameter and spacing increase. Alternatively, when a thicker 10 nm Cr adhesion layer is used, the growth mode becomes mixed, as both small effective wetting regions and film gaps exist. For the cases of no adhesion layer and 1 nm Cr adhesion layer, the nanorods are oriented at ˜23° from the substrate but lay down onto the substrate when a 10 nm thick Cr adhesion layer is used. Thin film adhesion tests demonstrate that both 1 nm and 10 nm Cr adhesion layers offer an enhanced performance over no adhesion layer or a glancing angle adhesion layer.

  9. Scale Invariance in 2D BCS-BEC Crossover

    NASA Astrophysics Data System (ADS)

    Sensarma, Rajdeep; Taylor, Edward; Randeria, Mohit

    2013-03-01

    In 2D BCS-BEC crossover, the frequency of the breathing mode in a harmonic trap, as well as the lower edge of the radio frequency spectroscopy response, show remarkable scale-invariance throughout the crossover regime, i.e. they are independent of the coupling constant. Using functional integral methods, we study the behaviour of these quantities in the 2D BCS-BEC crossover and comment on the possible reasons for this scale independence. RS was supported by DAE, Govt. of India. MR was supported by NSF Grant No. DMR-1006532. ET was supported by NSERC and the Canadian Institute for Advanced Research.

  10. Physiological state, growth mode, and oxidative stress play a role in Cd(II)-mediated inhibition of Nitrosomonas europaea 19718.

    PubMed

    Chandran, Kartik; Love, Nancy G

    2008-04-01

    The goal of this study was to determine the impact of physiological growth states (batch exponential and batch stationary growth) and growth modes (substrate-limited chemostat, substrate-sufficient exponential batch, and substrate-depleted stationary batch growth) on several measures of growth and responses to Cd(II)-mediated inhibition of Nitrosomonas europaea strain 19718. The specific oxygen uptake rate (sOUR) was the most sensitive indicator of inhibition among the different responses analyzed, including total cell abundance, membrane integrity, intracellular 16S rRNA/DNA ratio, and amoA expression. This observation remained true irrespective of the physiological state, the growth mode, or the mode of Cd(II) exposure. Based on the sOUR, a strong time-dependent exacerbation of inhibition (in terms of an inhibition coefficient [K(i)]) in exponential batch cultures was observed. Long-term inhibition levels (based on K(i) estimates) in metabolically active chemostat and exponential batch cultures were also especially severe and comparable. In contrast, the inhibition level in stationary-phase cultures was 10-fold lower and invariable with exposure time. Different strategies for surviving substrate limitation (a 10-fold increase in amoA expression) and starvation (the retention of 16S rRNA levels) in N. europaea cultures were observed. amoA expression was most negatively impacted by Cd(II) exposure in the chemostat cultures, was less impacted in exponential batch cultures, and was least impacted in stationary batch cultures. Although the amoA response was consistent with that of the sOUR, the amoA response was not as strong. The intracellular 16S rRNA/DNA ratio, as determined by fluorescence in situ hybridization, also did not uniformly correlate with the sOUR under conditions of inhibition or no inhibition. Finally, Cd(II)-mediated inhibition of N. europaea was attributed partially to oxidative stress.

  11. An atomistic study of growth mode and microstructure evolution of amorphous carbon films by different incident carbon atoms

    NASA Astrophysics Data System (ADS)

    Xue, Chen; Zhou, Jianqiu

    2014-09-01

    In this paper, molecular dynamics (MD) simulation has been performed to describe the growth and interfacial microstructure of amorphous carbon films. We focus on the film growth mode and surface morphology for diverse deposition process parameters mainly including incident energy and incident angle. To explore the relationship between the motion of deposition atoms and amorphous films growth, a series of snapshots for each deposition process has been taken for comparison. The snapshots show that the films growth modes are diverse at different incident parameters. In the next step, surface morphology, atom distribution along film growth direction and internal structure including vacancy defects evolution during deposition process are analyzed. The results reveal that incident energy on the horizontal plane dominates the surface roughness, and incident energy on the vertical plane dominates the compactness of the film. We conclude that a suitable incident parameter is not only beneficial to prepare amorphous films with compact and smooth or bump-like surface which will meet different needs, but also can avoid formation of defects during deposition. The simulation results are expected to provide useful guidance for improving amorphous carbon films quality.

  12. Growth rate and shape as possible control mechanisms for the selection of mode development in optimal biological branching processes

    NASA Astrophysics Data System (ADS)

    Alarcón, Tomás; Castillo, Jorge; García-Ponce, Berenice; Herrero, Miguel Angel; Padilla, Pablo

    2016-11-01

    Recently three branching modes were characterized during the formation of the lung in mice. These modes are highly stereotyped and correspond to domain formation, planar bifurcation and three dimensional branching respectively. At the same time it is proved that although genetic control mechanisms are presumably related to the selection of any of these modes, other external factors will most probably be involved in the branching process during development. In this paper we propose that the underlying controling factors might be related to the rate at which the tubes that form the lung network grow. We present a mathematical model that allows us to formulate specific experimental predictions on these growth rates. Moreover we show that according to this formulation, there is an optimization criterion which governs the branching process during lung development, namely, efficient local space filling properties of the network. If there is no space limitation the branches are allowed to grow freely and faster, selecting one branching mode, namely, domain formation. As soon as volume constraints appear the growth rate decreases, triggering the selection of planar and orthogonal bifurcation.

  13. Extended MHD simulations of Rayleigh-Taylor instability with real frequency in a 2D slab

    NASA Astrophysics Data System (ADS)

    Goto, Ryosuke; Miura, Hideaki; Ito, Atsushi; Sato, Masahiko; Hatori, Tomoharu

    2014-10-01

    Small scale effects such as the Finite Larmor Radius (FLR) effect and the Hall term can change the linear and non-linear growth of the high wave number unstable modes of the pressure driven instability considerably. Here we consider a simple Rayleigh-Taylor (R-T) instability in a 2D slab, and study the effect of the Hall term and the FLR effect to the R-T instability by means of numerical simulations of the Braginskii-type extended MHD equations. As we have reported earlier, the linear growth rates of the high wave number modes are highly reduced when the Hall term and the FLR effect are added simultaneously. However, there appears little real frequency in the previous work. Since the diamagnetic drift associated with the real frequency is considered to affect the growth of the linear and nonlinear evolutions, we provide a new equilibrium in which appearance of the real frequency is expected and carry out numerical simulations. Influences of the real frequency on the growth rates as well as on the nonlinear mixing width for some combinations of the Hall and the FLR parameters are going to be presented.

  14. 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

  15. 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

  16. Towards functional assembly of 3D and 2D nanomaterials

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher B.; Wang, Kai; Ievlev, Anton V.; Muckley, Eric S.; Ivanov, Ilia N.

    2016-09-01

    Functional assemblies of materials can be realized by tuning the work function and band gap of nanomaterials by rational material selection and design. Here we demonstrate the structural assembly of 2D and 3D nanomaterials and show that layering a 2D material monolayer on a 3D metal oxide leads to substantial alteration of both the surface potential and optical properties of the 3D material. A 40 nm thick film of polycrystalline NiO was produced by room temperature rf-sputtering, resulting in a 3D nanoparticle assembly. Chemical vapor deposition (CVD) grown 10-30 μm WS2 flakes (2D material) were placed on the NiO surface using a PDMS stamp transfer technique. The 2D/3D WS2/NiO assembly was characterized using confocal micro Raman spectroscopy to evaluate the vibrational properties and using Kelvin probe force microscopy (KPFM) to evaluate the surface potential. Raman maps of the 2D/3D assembly show spatial non-uniformity of the A1g mode ( 418 cm-1) and the disorder-enhanced longitudinal acoustic mode, 2LA(M) ( 350 cm-1), suggesting that the WS2 exists in a strained condition on when transferred onto 3D polycrystalline NiO. KPFM measurements show that single layer WS2 on SiO2 has a surface potential 75 mV lower than that of SiO2, whereas the surface potential of WS2 on NiO is 15 mV higher than NiO, indicating that WS2 could act as electron donor or acceptor depending on the 3D material it is interfaced with. Thus 2D and 3D materials can be organized into functional assemblies with electron flow controlled by the WS2 either as the electron donor or acceptor.

  17. III-Vs at Scale: A PV Manufacturing Cost Analysis of the Thin Film Vapor-Liquid-Solid Growth Mode

    SciTech Connect

    Zheng, Maxwell; Horowitz, Kelsey; Woodhouse, Michael; Battaglia, Corsin; Kapadia, Rehan; Javey, Ali

    2016-06-01

    The authors present a manufacturing cost analysis for producing thin-film indium phosphide modules by combining a novel thin-film vapor-liquid-solid (TF-VLS) growth process with a standard monolithic module platform. The example cell structure is ITO/n-TiO2/p-InP/Mo. For a benchmark scenario of 12% efficient modules, the module cost is estimated to be $0.66/W(DC) and the module cost is calculated to be around $0.36/W(DC) at a long-term potential efficiency of 24%. The manufacturing cost for the TF-VLS growth portion is estimated to be ~$23/m2, a significant reduction compared with traditional metalorganic chemical vapor deposition. The analysis here suggests the TF-VLS growth mode could enable lower-cost, high-efficiency III-V photovoltaics compared with manufacturing methods used today and open up possibilities for other optoelectronic applications as well.

  18. 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.

  19. [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.

  20. 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.

  1. Quantitative 2D liquid-state NMR.

    PubMed

    Giraudeau, Patrick

    2014-06-01

    Two-dimensional (2D) liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, it suffers from two main drawbacks that probably explain its relatively late development. First, the 2D NMR signal is strongly molecule-dependent and site-dependent; second, the long duration of 2D NMR experiments prevents its general use for high-throughput quantitative applications and affects its quantitative performance. Fortunately, the last 10 years has witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. This review aims at presenting these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. After highlighting the interest of 2D NMR for quantitative analysis, the different strategies to determine the absolute concentrations from 2D NMR spectra are described and illustrated by recent applications. The last part of the manuscript concerns the recent development of fast quantitative 2D NMR approaches, aiming at reducing the experiment duration while preserving - or even increasing - the analytical performance. We hope that this comprehensive review will help readers to apprehend the current landscape of quantitative 2D NMR, as well as the perspectives that may arise from it.

  2. Mixotrophic growth of Phaeodactylum tricornutum on fructose and glycerol in fed-batch and semi-continuous modes.

    PubMed

    Cerón-García, M C; Fernández-Sevilla, J M; Sánchez-Mirón, A; García-Camacho, F; Contreras-Gómez, A; Molina-Grima, E

    2013-11-01

    Mixotrophic cultures of Phaeodactylum tricornutum were carried out in bubble columns using fructose and glycerol in indoor fed-batch and semi-continuous modes. In the fed-batch cultures, different nutrient-addition strategies, combined with stepwise increments in the light intensity, were assayed. It was found that glycerol promoted significantly higher biomass productivity than fructose. A glycerol-induced photoinhibition that arrested the growth of P. tricornutun was also observed. As this was considered a limitation as regards transferring the fed-batch mode to outdoor conditions, this information was used to culture P. tricornutum in semi-continuous mode. Similar glycerol-induced photoinhibition was not observed in these cultures, even at highest dilution rates. Although the highest biomass (1.5 g L(-1) d(-1)) and EPA (40 mg L(-1) d(-1)) productivities found in the semi-continuous cultures were lower than those obtained photoautotrophically in outdoor photobioreactors, the findings showed that semi-continuous mode was an excellent candidate for transferring mixotrophic culture to an outdoor setting.

  3. Investigation of YBa2Cu3O7-δ growth mode effect on the dielectric properties of BaxSr1-xTiO3 for BaxSr1-xTiO3/YBa2Cu3O7-δ bilayered thin films epitaxially grown on vicinal LaAlO3 substrates

    NASA Astrophysics Data System (ADS)

    Zhu, X. H.; Peng, W.; Tian, H. F.; Yong, L. P.; Li, J.; Li, J. Q.; Zheng, D. N.

    2006-10-01

    Epitaxial bilayered thin films of BaxSr1-xTiO3 (BSTO, x = 0.1 and 0.5)/YBa2Cu3O7-δ (YBCO), with different YBCO film thicknesses, have been grown in situ by pulsed-laser deposition on 1.2° vicinal LaAlO3 substrates. The critical thickness for the transformation of the growth mode in YBCO between two-dimensional (2D) step flow and three-dimensional island is experimentally confirmed to be around 180 nm. As the YBCO-film thickness increases from 145 to 250 nm, the tremendous degradation of the film quality, due to the growth-mode change in YBCO, leads to drastic deterioration in the dielectric properties of BSTO thin films, with severe decrease in the figure of merit factor from 148 to 10 in Ba0.1Sr0.9TiO3/YBCO (at 77 K and 100 kHz) and from 56 to 6 in Ba0.5Sr0.5TiO3/YBCO (at 300 K and 100 kHz). As a result, the dielectric properties of BSTO thin films could be significantly enhanced by strictly tailoring the growth mode in YBCO as a 2D step flow for this kind of BSTO/YBCO bilayers.

  4. Growth and decay of discrete nonlinear Schrodinger breathers interacting with internal modes or standing-wave phonons

    PubMed

    Johansson; Aubry

    2000-05-01

    We investigate the long-time evolution of weakly perturbed single-site breathers (localized stationary states) in the discrete nonlinear Schrodinger equation. The perturbations we consider correspond to time-periodic solutions of the linearized equations around the breather, and can be either (i) spatially localized or (ii) spatially extended. For case (i), which corresponds to the excitation of an internal mode of the breather, we find that the nonlinear interaction between the breather and its internal mode always leads to a slow growth of the breather amplitude and frequency. In case (ii), corresponding to interaction between the breather and a standing-wave phonon, the breather will grow provided that the wave vector of the phonon is such that the generation of radiating higher harmonics at the breather is possible. In other cases, breather decay is observed. This condition yields a limit value for the breather frequency above which no further growth is possible. We also discuss another mechanism for breather growth and destruction which becomes important when the amplitude of the perturbation is non-negligible, and which originates from the oscillatory instabilities of the nonlinear standing-wave phonons.

  5. Optoelectronics based on 2D TMDs and heterostructures

    NASA Astrophysics Data System (ADS)

    Huo, Nengjie; Yang, Yujue; Li, Jingbo

    2017-03-01

    2D materials including graphene and TMDs have proven interesting physical properties and promising optoelectronic applications. We reviewed the growth, characterization and optoelectronics based on 2D TMDs and their heterostructures, and demonstrated their unique and high quality of performances. For example, we observed the large mobility, fast response and high photo-responsivity in MoS2, WS2 and WSe2 phototransistors, as well as the novel performances in vdW heterostructures such as the strong interlayer coupling, am-bipolar and rectifying behaviour, and the obvious photovoltaic effect. It is being possible that 2D family materials could play an increasingly important role in the future nano- and opto-electronics, more even than traditional semiconductors such as silicon.

  6. Kinetic growth mode of epitaxial GaAs on Si(001) micro-pillars

    NASA Astrophysics Data System (ADS)

    Bergamaschini, Roberto; Bietti, Sergio; Castellano, Andrea; Frigeri, Cesare; Falub, Claudiu V.; Scaccabarozzi, Andrea; Bollani, Monica; von Känel, Hans; Miglio, Leo; Sanguinetti, Stefano

    2016-12-01

    Three-dimensional, epitaxial GaAs crystals are fabricated on micro-pillars patterned into Si(001) substrates by exploiting kinetically controlled growth conditions in Molecular Beam Epitaxy. The evolution of crystal morphology during growth is assessed by considering samples with increasing GaAs deposit thickness. Experimental results are interpreted by a kinetic growth model, which takes into account the fundamental aspects of the growth and mutual deposition flux shielding between neighboring crystals. Different substrate pattern geometries with dissimilar lateral sizes and periodicities of the Si micro-pillars are considered and self-similar crystal structures are recognized. It is demonstrated that the top faceting of the GaAs crystals is tunable, which can pave the way to locally engineer compound semiconductor quantum structures on Si(001) substrates.

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

    PubMed

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

    2013-12-31

    Fermenting cells growing exponentially on rich (YPAD) medium underwent a transition 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 transition period, the high-affinity Fe import rate declined slower than the cell-growth rate declined, causing Fe to accumulate, initially as Fe(III) oxyhydroxide nanoparticles but eventually as mitochondrial and vacuolar Fe. Once the cells had reached 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 the exponential phase and underwent a transition to a true stationary state as glucose levels declined. The Fe concentration of MM cells that just entered the stationary state was similar to that of YPAD cells, but MM cells continued to accumulate Fe in the stationary state. Fe initially accumulated as nanoparticles and high-spin Fe(II) species, but vacuolar Fe(III) also eventually accumulated. Surprisingly, Fe-packed 5-day-old MM cells suffered no more reactive oxygen species (ROS) damage than younger cells, suggesting that the 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 the import of Fe via a regulated high-affinity pathway and an unregulated low-affinity pathway. The import of Fe from the cytosol to 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

  8. 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.

  9. 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.

  10. THE MODE OF ACTION OF ANTIBIOTICS IN STIMULATING GROWTH OF CHICKS

    PubMed Central

    Eyssen, H.; de Somer, P.

    1963-01-01

    A study was made of the effect of antibiotics on growth of chicks and on intestinal absorption of fats and carbohydrates. Around the 8th day of life, chicks fed an antibiotic-free casein-sucrose diet developed a transitory syndrome of malabsorption of fats and carbohydrates, associated with disturbance of the efficiency of feed utilization and poor weight increase. Administration of virginiamycin, at a level of 20 ppm, suppressed this period of malabsorption and resulted in improved feed conversion and increased weight gain. The temporary growth depression and malabsorption were not observed in disinfected rooms in new quarters. Under these conditions virginiamycin did not stimulate growth nor was the efficiency of feed utilization improved by the antibiotic. However, the growth-depressing flora could be introduced to the new quarters by feeding each bird 50 mg of fresh feces collected from chicks in old quarters. Both the intestinal absorption and the growth-promoting effect of virginiamycin were influenced by the type of carbohydrate in the basal diet, and have been found to be most pronounced when sucrose was fed as the sole source of carbohydrate. The malabsorption was less obvious when cornstarch was substituted for sucrose. In this case virginiamycin had only a limited effect on growth and on feed conversion. The present investigations suggest that antibiotics stimulate growth of chicks by their antibacterial action against Gram-positive microorganisms which interfere with the absorption of nutrients. Furthermore, the growth-promoting effect seems to be most pronounced during a limited period of a few days around the 8th day of life. PMID:19867220

  11. Growth of large-scale boron nanowire patterns with identical base-up mode and in situ field emission studies of individual boron nanowire.

    PubMed

    Liu, Fei; Gan, Haibo; Tang, Dai-Ming; Cao, Yunzhe; Mo, Xiaoshu; Chen, Jun; Deng, Shaozhi; Xu, Ningsheng; Golberg, Dmitri; Bando, Yoshio

    2014-02-26

    Boron nanowires (BNWs) are considered as an ideal optoelectronic nanomaterial, but controlling them in identical growth mode and large-area patterns is technically challenging. Here, large-scale BNW patterns with a uniform base-up growth mode are successfully fabricated by choosing Ni film as the catalyst. Moreover, they exhibit low turn-on field (4.3 V/μm) and excellent field emission uniformity (88%).

  12. 2-D Clinostat for Simulated Microgravity Experiments with Arabidopsis Seedlings

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Li, Xugang; Krause, Lars; Görög, Mark; Schüler, Oliver; Hauslage, Jens; Hemmersbach, Ruth; Kircher, Stefan; Lasok, Hanna; Haser, Thomas; Rapp, Katja; Schmidt, Jürgen; Yu, Xin; Pasternak, Taras; Aubry-Hivet, Dorothée; Tietz, Olaf; Dovzhenko, Alexander; Palme, Klaus; Ditengou, Franck Anicet

    2016-04-01

    Ground-based simulators of microgravity such as fast rotating 2-D clinostats are valuable tools to study gravity related processes. We describe here a versatile g-value-adjustable 2-D clinostat that is suitable for plant analysis. To avoid seedling adaptation to 1 g after clinorotation, we designed chambers that allow rapid fixation. A detailed protocol for fixation, RNA isolation and the analysis of selected genes is described. Using this clinostat we show that mRNA levels of LONG HYPOCOTYL 5 (HY5), MIZU-KUSSEI 1 (MIZ1) and microRNA MIR163 are down-regulated in 5-day-old Arabidopsis thaliana roots after 3 min and 6 min of clinorotation using a maximal reduced g-force of 0.02 g, hence demonstrating that this 2-D clinostat enables the characterization of early transcriptomic events during root response to microgravity. We further show that this 2-D clinostat is able to compensate the action of gravitational force as both gravitropic-dependent statolith sedimentation and subsequent auxin redistribution (monitoring D R5 r e v :: G F P reporter) are abolished when plants are clinorotated. Our results demonstrate that 2-D clinostats equipped with interchangeable growth chambers and tunable rotation velocity are suitable for studying how plants perceive and respond to simulated microgravity.

  13. Plasmonic Excitations of 1D Metal-Dielectric Interfaces in 2D Systems: 1D Surface Plasmon Polaritons

    NASA Astrophysics Data System (ADS)

    Mason, Daniel R.; Menabde, Sergey G.; Yu, Sunkyu; Park, Namkyoo

    2014-04-01

    Surface plasmon-polariton (SPP) excitations of metal-dielectric interfaces are a fundamental light-matter interaction which has attracted interest as a route to spatial confinement of light far beyond that offered by conventional dielectric optical devices. Conventionally, SPPs have been studied in noble-metal structures, where the SPPs are intrinsically bound to a 2D metal-dielectric interface. Meanwhile, recent advances in the growth of hybrid 2D crystals, which comprise laterally connected domains of distinct atomically thin materials, provide the first realistic platform on which a 2D metal-dielectric system with a truly 1D metal-dielectric interface can be achieved. Here we show for the first time that 1D metal-dielectric interfaces support a fundamental 1D plasmonic mode (1DSPP) which exhibits cutoff behavior that provides dramatically improved light confinement in 2D systems. The 1DSPP constitutes a new basic category of plasmon as the missing 1D member of the plasmon family: 3D bulk plasmon, 2DSPP, 1DSPP, and 0D localized SP.

  14. 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.

  15. 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

  16. 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

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

    NASA Astrophysics Data System (ADS)

    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%).

  18. 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%)

  19. Hall and gyro-viscous effects to the Rayleigh-Taylor instability in a 2D slab

    NASA Astrophysics Data System (ADS)

    Goto, Ryosuke; Miura, Hideaki; Ito, Atsushi; Sato, Masahiko; Hatori, Tomotoharu

    2013-10-01

    Small scale effects such as the Finite Larmor Radius (FLR) effect and the Hall term which are ignored in the single-fluid MHD model can be important for the growth of the high wave number unstable modes such as the ballooning instability. Here we consider a simple Rayleigh-Taylor (R-T) instability in a 2D slab, and study the effect of the Hall term and the FLR effect to the R-T instability. The FLR effect is modeled as the gyro-viscous tensor. It is shown that the linear growth rate of the high wave number modes are reduced by the FLR effect and increased by the Hall term. However, when the Hall term and the FLR effect are added simultaneously, high wave number modes are strongly reduced. We will compare results of linear stability analysis to those of nonlinear simulations, and study some aspects of nonlinear growth under the effect of the FLR and the Hall terms by the use of an appropriate index such as the mixing width. In the Hall case, mixing width is slightly increased compared with MHD case. However growth rate reduces when the Hall term and the gyro-viscosity are added simultaneously, mixing width reaches comparable level with MHD case.

  20. Mode of Action of Polyamine Analogues on the Growth and Biochemistry of Leishmanial Cells.

    DTIC Science & Technology

    1981-09-15

    At least two of these compounds,namely MGBG ( methylglyoxal bis-(guanylhydrazone) and sinefungin gave promising results (18,19). In addition, known...K.P., Steiger, R.F., Dave, C., Cheng, Y.-C.: Effect of methylglyoxal bis(guanylhydrazone) on tryponosomatid flagellates: Tnhibition of growth and

  1. 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.

  2. Mixed gravity mode growth during directional dendritic solidification aboard the KC-135

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.

    1989-01-01

    NASA's KC-135, which flies a cyclic parabolic route designed to furnish periods of low gravity alternating with periods of high gravity, has been used to directionally solidify a superalloy and a FE-C-Si alloy. Probable transient effects, due to the rapid changes in the gravity levels, must be taken into account. An effort is presently made to show that experimental design is especially critical in the case of dendritic directional solidification experiments in which mixed gravity modes occur; inappropriate design easily leads to anomalous structures and data.

  3. Bi-sided integral imaging with 2D/3D convertibility using scattering polarizer.

    PubMed

    Yeom, Jiwoon; Hong, Keehoon; Park, Soon-gi; Hong, Jisoo; Min, Sung-Wook; Lee, Byoungho

    2013-12-16

    We propose a two-dimensional (2D) and three-dimensional (3D) convertible bi-sided integral imaging. The proposed system uses the polarization state of projected light for switching its operation mode between 2D and 3D modes. By using an optical module composed of two scattering polarizers and one linear polarizer, the proposed integral imaging system simultaneously provides 3D images with 2D background images for observers who are located in the front and the rear sides of the system. The occlusion effect between 2D images and 3D images is realized by using a compensation mask for 2D images and the elemental images. The principle of proposed system is experimentally verified.

  4. Flow transitions in a 2D directional solidification model

    NASA Technical Reports Server (NTRS)

    Larroude, Philippe; Ouazzani, Jalil; Alexander, J. Iwan D.

    1992-01-01

    Flow transitions in a Two Dimensional (2D) model of crystal growth were examined using the Bridgman-Stockbarger me thod. Using a pseudo-spectral Chebyshev collocation method, the governing equations yield solutions which exhibit a symmetry breaking flow tansition and oscillatory behavior indicative of a Hopf bifurcation at higher values of Ra. The results are discussed from fluid dynamic viewpoint, and broader implications for process models are also addressed.

  5. Superlinear growth of Rayleigh scattering-induced intensity noise in single-mode fibers.

    PubMed

    Cahill, James P; Okusaga, Olukayode; Zhou, Weimin; Menyuk, Curtis R; Carter, Gary M

    2015-03-09

    Rayleigh scattering generates intensity noise close to an optical carrier that propagates in a single-mode optical fiber. This noise degrades the performance of optoelectronic oscillators and RF-photonic links. When using a broad linewidth laser, we previously found that the intensity noise power scales linearly with optical power and fiber length, which is consistent with guided entropy mode Rayleigh scattering (GEMRS), a third order nonlinear scattering process, in the spontaneous limit. In this work, we show that this behavior changes significantly with the use of a narrow linewidth laser. Using a narrow linewidth laser, we measured the bandwidth of the intensity noise plateau to be 10 kHz. We found that the scattered noise power scales superlinearly with fiber length up to lengths of 10 km in the frequency range of 500 Hz to 10 kHz, while it scales linearly in the frequency range of 10 Hz to 100 Hz. These results suggest that the Rayleigh-scattering-induced intensity noise cannot be explained by third-order nonlinear scattering in the spontaneous limit, as previously hypothesized.

  6. 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.

  7. 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.

  8. 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.

  9. 2D/3D switchable displays

    NASA Astrophysics Data System (ADS)

    Dekker, T.; de Zwart, S. T.; Willemsen, O. H.; Hiddink, M. G. H.; IJzerman, W. L.

    2006-02-01

    A prerequisite for a wide market acceptance of 3D displays is the ability to switch between 3D and full resolution 2D. In this paper we present a robust and cost effective concept for an auto-stereoscopic switchable 2D/3D display. The display is based on an LCD panel, equipped with switchable LC-filled lenticular lenses. We will discuss 3D image quality, with the focus on display uniformity. We show that slanting the lenticulars in combination with a good lens design can minimize non-uniformities in our 20" 2D/3D monitors. Furthermore, we introduce fractional viewing systems as a very robust concept to further improve uniformity in the case slanting the lenticulars and optimizing the lens design are not sufficient. We will discuss measurements and numerical simulations of the key optical characteristics of this display. Finally, we discuss 2D image quality, the switching characteristics and the residual lens effect.

  10. 2-d Finite Element Code Postprocessor

    SciTech Connect

    Sanford, L. A.; Hallquist, J. O.

    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 forces 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.

  11. Transition to chaos in an open unforced 2D flow

    NASA Technical Reports Server (NTRS)

    Pulliam, Thomas H.; Vastano, John A.

    1993-01-01

    The present numerical study of unsteady, low Reynolds number flow past a 2D airfoil attempts to ascertain the bifurcation sequence leading from simple periodic to complex aperiodic flow with rising Reynolds number, as well as to characterize the degree of chaos present in the aperiodic flow and assess the role of numerics in the modification and control of the observed bifurcation scenario. The ARC2D Navier-Stokes code is used in an unsteady time-accurate mode for most of these computations. The system undergoes a period-doubling bifurcation to chaos as the Reynolds number is increased from 800 to 1600; its chaotic attractors are characterized by estimates of the fractal dimension and partial Liapunov exponent spectra.

  12. 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.

  13. Growth mode of carbide from C 2H 4 or CO on Ni( 1 1 1 )

    NASA Astrophysics Data System (ADS)

    Nakano, H.; Ogawa, J.; Nakamura, J.

    2002-08-01

    The growth of carbide on a Ni(1 1 1) surface by the decomposition of C 2H 4 and the Boudouard reaction (2CO g→C a+CO 2,g) was studied using scanning tunneling microscopy (STM), Auger electron spectroscopy and low energy electron diffraction. STM results showed that the carbide growth by the Boudouard reaction started at step edges on Ni(1 1 1), while for the C 2H 4 decomposition the carbide was formed preferentially at terrace sites with very low concentration of carbide at the step edge. The different behavior for the carbide growth was ascribed to the difference in the dissociation sites of CO and C 2H 4. As for the Boudouard reaction, CO was dissociated at the step edge and then carbon migrated into the bulk at a reaction temperature of 500 K. The carbon was then segregated at room temperature to the surface from the bulk to form a single domain of the ( 39× 39) R16.1° structure at the step edge. On the other hand, the C 2H 4 decomposition took place on the terrace leading to an isolated carbide unit or carbide short strings on the terrace.

  14. Growth of compaction bands: A new deformation mode for porous rock

    SciTech Connect

    OLSSON,WILLIAM A.; HOLCOMB,DAVID J.

    2000-03-14

    Compaction bands are thin, tabular zones of grain breakage and reduced porosity that are found in sandstones. These structures may form due to tectonic stresses or as a result of local stresses induced during production of fluids from wells, resulting in barriers to fluid (oil, gas, water) movement in sandstone reservoirs. To gain insight into the formation of compaction bands the authors have produced them in the laboratory. Acoustic emission locations were used to define and track the thickness of compaction bands throughout the stress history during axisymmetric compression experiments. Narrow zones of intense acoustic emission, demarcating the boundaries between the uncompacted and compacted regions were found to develop. Unexpectedly, these boundaries moved at velocities related to the fractional porosity reduction across the boundary and to the imposed specimen compression stress. This appears to be a previously unrecognized, fundamental mode of deformation of a porous, granular material subjected to compressive loading with significant implications for the production of hydrocarbons.

  15. 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

  16. 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.

  17. 2D vibrational properties of epitaxial silicene on Ag(111)

    NASA Astrophysics Data System (ADS)

    Solonenko, Dmytro; Gordan, Ovidiu D.; Le Lay, Guy; Sahin, Hasan; Cahangirov, Seymur; Zahn, Dietrich R. T.; Vogt, Patrick

    2017-03-01

    The two-dimensional silicon allotrope, silicene, could spur the development of new and original concepts in Si-based nanotechnology. Up to now silicene can only be epitaxially synthesized on a supporting substrate such as Ag(111). Even though the structural and electronic properties of these epitaxial silicene layers have been intensively studied, very little is known about its vibrational characteristics. Here, we present a detailed study of epitaxial silicene on Ag(111) using in situ Raman spectroscopy, which is one of the most extensively employed experimental techniques to characterize 2D materials, such as graphene, transition metal dichalcogenides, and black phosphorous. The vibrational fingerprint of epitaxial silicene, in contrast to all previous interpretations, is characterized by three distinct phonon modes with A and E symmetries. Both, energies and symmetries of theses modes are confirmed by ab initio theory calculations. The temperature dependent spectral evolution of these modes demonstrates unique thermal properties of epitaxial silicene and a significant electron-phonon coupling. These results unambiguously support the purely two-dimensional character of epitaxial silicene up to about 300 °C, whereupon a 2D-to-3D phase transition takes place. The detailed fingerprint of epitaxial silicene will allow us to identify it in different environments or to study its modifications.

  18. 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.

  19. 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).

  20. 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

  1. 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.

  2. 2D photonic crystal and its angular reflective azimuthal spectrum

    NASA Astrophysics Data System (ADS)

    Senderakova, Dagmar; Drzik, Milan; Tomekova, Juliana

    2016-12-01

    Contemporary, attention is paid to photonic crystals, which can strongly modify light propagation through them and enable a controllable light manipulation. The contribution is focused on a sub-wavelength 2D structure formed by Al2O3 layer on silicon substrate, patterned with periodic hexagonal lattice of deep air holes. Using various laser sources of light at single wavelength, azimuthal angle dependence of the mirror-like reflected light intensity was recorded photo-electrically. The results obtained can be used to sample the band-structure of leaky modes of the photonic crystal more reliably and help us to map the photonic dispersion diagram.

  3. 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.

  4. 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.

  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. 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. Orthotropic Piezoelectricity in 2D Nanocellulose

    NASA Astrophysics Data System (ADS)

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-10-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V‑1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.

  8. Orthotropic Piezoelectricity in 2D Nanocellulose

    PubMed Central

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-01-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V−1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies. PMID:27708364

  9. Orthotropic Piezoelectricity in 2D Nanocellulose.

    PubMed

    García, Y; Ruiz-Blanco, Yasser B; Marrero-Ponce, Yovani; Sotomayor-Torres, C M

    2016-10-06

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V(-1), ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.

  10. 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.

  11. 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.

  12. 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.

  13. Assessing 2D electrophoretic mobility spectroscopy (2D MOSY) for analytical applications.

    PubMed

    Fang, Yuan; Yushmanov, Pavel V; Furó, István

    2016-12-08

    Electrophoretic displacement of charged entity phase modulates the spectrum acquired in electrophoretic NMR experiments, and this modulation can be presented via 2D FT as 2D mobility spectroscopy (MOSY) spectra. We compare in various mixed solutions the chemical selectivity provided by 2D MOSY spectra with that provided by 2D diffusion-ordered spectroscopy (DOSY) spectra and demonstrate, under the conditions explored, a superior performance of the former method. 2D MOSY compares also favourably with closely related LC-NMR methods. The shape of 2D MOSY spectra in complex mixtures is strongly modulated by the pH of the sample, a feature that has potential for areas such as in drug discovery and metabolomics. Copyright © 2016 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd. StartCopTextCopyright © 2016 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.

  14. 2D Distributed Sensing Via TDR

    DTIC Science & Technology

    2007-11-02

    plate VEGF CompositeSensor Experimental Setup Air 279 mm 61 78 VARTM profile: slope RTM profile: rectangle 22 1 Jul 2003© 2003 University of Delaware...2003 University of Delaware All rights reserved Vision: Non-contact 2D sensing ü VARTM setup constructed within TL can be sensed by its EM field: 2D...300.0 mm/ns. 1 2 1 Jul 2003© 2003 University of Delaware All rights reserved Model Validation “ RTM Flow” TDR Response to 139 mm VEGC

  15. 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.

  16. 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.

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

    PubMed

    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

    2010-11-01

    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.

  18. 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.

  19. 2D depiction of nonbonding interactions for protein complexes.

    PubMed

    Zhou, Peng; Tian, Feifei; Shang, Zhicai

    2009-04-30

    A program called the 2D-GraLab is described for automatically generating schematic representation of nonbonding interactions across the protein binding interfaces. The input file of this program takes the standard PDB format, and the outputs are two-dimensional PostScript diagrams giving intuitive and informative description of the protein-protein interactions and their energetics properties, including hydrogen bond, salt bridge, van der Waals interaction, hydrophobic contact, pi-pi stacking, disulfide bond, desolvation effect, and loss of conformational entropy. To ensure these interaction information are determined accurately and reliably, methods and standalone programs employed in the 2D-GraLab are all widely used in the chemistry and biology community. The generated diagrams allow intuitive visualization of the interaction mode and binding specificity between two subunits in protein complexes, and by providing information on nonbonding energetics and geometric characteristics, the program offers the possibility of comparing different protein binding profiles in a detailed, objective, and quantitative manner. We expect that this 2D molecular graphics tool could be useful for the experimentalists and theoreticians interested in protein structure and protein engineering.

  20. 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

    2016-03-23

    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.

  1. The basics of 2D DIGE.

    PubMed

    Beckett, Phil

    2012-01-01

    The technique of two-dimensional (2D) gel electrophoresis is a powerful tool for separating complex mixtures of proteins, but since its inception in the mid 1970s, it acquired the stigma of being a very difficult application to master and was generally used to its best effect by experts. The introduction of commercially available immobilized pH gradients in the early 1990s provided enhanced reproducibility and easier protocols, leading to a pronounced increase in popularity of the technique. However gel-to-gel variation was still difficult to control without the use of technical replicates. In the mid 1990s (at the same time as the birth of "proteomics"), the concept of multiplexing fluorescently labeled proteins for 2D gel separation was realized by Jon Minden's group and has led to the ability to design experiments to virtually eliminate gel-to-gel variation, resulting in biological replicates being used for statistical analysis with the ability to detect very small changes in relative protein abundance. This technology is referred to as 2D difference gel electrophoresis (2D DIGE).

  2. Parallel stitching of 2D materials

    DOE PAGES

    Ling, Xi; Wu, Lijun; Lin, Yuxuan; ...

    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.

  3. Flat or lumpy: Surface structure and growth modes in silicon-germanium epitaxy

    NASA Astrophysics Data System (ADS)

    Bailes, Allison Arthur, III

    We have investigated the surface structure of Ge/Sb/Si(100) and H/Ge/Si(100) with transmission ion channeling. The former was a continuation of our studies of surfactant-mediated epitaxy and our attempt to determine the exchange mechanism as the surfactant segregates to the surface during growth. The method of analysis used for this part was comparison of experimental with simulated scattered ion energy distributions. Our interest in the latter system grew out of the differences observed between H/Si(100) and H/Ge(100). We studied this system using the traditional angular scan (yield versus tilt) analysis. After depositing Ge on Sb-terminated Si(100)-2x1 at room temperature (RT), we collected ion scattering data near the < 100> direction of beam incidence. First, we determined that the single adatom exchange model did not fit our previous data for Ge coverages of 0.15 ML and 0.68 ML. Second, we deposited 2 ML Ge and found the system at RT to be in the same configuration that we had found for 0.68 ML Ge (elongated Ge dimers). Third, we studied this system with 0.4 ML Ge after RT and after anneals at 80sp°C, 150sp°C, 200sp°C, 350sp°C, and 500sp°C. We found the Ge to be described by the all dimer model at RT and 80sp°C, an intermediate state at 150sp°C and 200sp°C, and the final state (Sb dimers and near-substitutional Ge) at 350sp°C, and 500sp°C. We had difficulty distinguishing between which of three models best described the Sb structure in this experiment because of limitations in the method of analyzing energy distributions. We found energy shifts in the experimental distributions that can be caused by thickness variation and perhaps by deformation of the sample because of strain in the Ge layer. Finally, in our study of the monohydride-covered Ge/Si(100) surface, we determined that the Ge dimers were elongated relative to the previously-studied Ge/Si(100) without H. The dimer bond length was 2.8 A and the dimers were untilted, whereas previous work

  4. Raman 2D-band splitting in graphene: theory and experiment.

    PubMed

    Frank, Otakar; Mohr, Marcel; Maultzsch, Janina; Thomsen, Christian; Riaz, Ibtsam; Jalil, Rashid; Novoselov, Kostya S; Tsoukleri, Georgia; Parthenios, John; Papagelis, Konstantinos; Kavan, Ladislav; Galiotis, Costas

    2011-03-22

    We present a systematic experimental and theoretical study of the two-phonon (2D) Raman scattering in graphene under uniaxial tension. The external perturbation unveils that the 2D mode excited with 785 nm has a complex line-shape mainly due to the contribution of two distinct double resonance scattering processes (inner and outer) in the Raman signal. The splitting depends on the direction of the applied strain and the polarization of the incident light. The results give new insight into the nature of the 2D band and have significant implications for the use of graphene as reinforcement in composites since the 2D mode is crucial to assess how effectively graphene uptakes an applied stress or strain.

  5. 2D OR NOT 2D: THE EFFECT OF DIMENSIONALITY ON THE DYNAMICS OF FINGERING CONVECTION AT LOW PRANDTL NUMBER

    SciTech Connect

    Garaud, Pascale; Brummell, Nicholas

    2015-12-10

    Fingering convection (otherwise known as thermohaline convection) is an instability that occurs in stellar radiative interiors in the presence of unstable compositional gradients. Numerical simulations have been used in order to estimate the efficiency of mixing induced by this instability. However, fully three-dimensional (3D) computations in the parameter regime appropriate for stellar astrophysics (i.e., low Prandtl number) are prohibitively expensive. This raises the question of whether two-dimensional (2D) simulations could be used instead to achieve the same goals. In this work, we address this issue by comparing the outcome of 2D and 3D simulations of fingering convection at low Prandtl number. We find that 2D simulations are never appropriate. However, we also find that the required 3D computational domain does not have to be very wide: the third dimension only needs to contain a minimum of two wavelengths of the fastest-growing linearly unstable mode to capture the essentially 3D dynamics of small-scale fingering. Narrow domains, however, should still be used with caution since they could limit the subsequent development of any large-scale dynamics typically associated with fingering convection.

  6. Arrayed van der Waals Vertical Heterostructures Based on 2D GaSe Grown by Molecular Beam Epitaxy.

    PubMed

    Yuan, Xiang; Tang, Lei; Liu, Shanshan; Wang, Peng; Chen, Zhigang; Zhang, Cheng; Liu, Yanwen; Wang, Weiyi; Zou, Yichao; Liu, Cong; Guo, Nan; Zou, Jin; Zhou, Peng; Hu, Weida; Xiu, Faxian

    2015-05-13

    Vertically stacking two-dimensional (2D) materials can enable the design of novel electronic and optoelectronic devices and realize complex functionality. However, the fabrication of such artificial heterostructures on a wafer scale with an atomically sharp interface poses an unprecedented challenge. Here, we demonstrate a convenient and controllable approach for the production of wafer-scale 2D GaSe thin films by molecular beam epitaxy. In situ reflection high-energy electron diffraction oscillations and Raman spectroscopy reveal a layer-by-layer van der Waals epitaxial growth mode. Highly efficient photodetector arrays were fabricated, based on few-layer GaSe on Si. These photodiodes show steady rectifying characteristics and a high external quantum efficiency of 23.6%. The resultant photoresponse is super-fast and robust, with a response time of 60 μs. Importantly, the device shows no sign of degradation after 1 million cycles of operation. We also carried out numerical simulations to understand the underlying device working principles. Our study establishes a new approach to produce controllable, robust, and large-area 2D heterostructures and presents a crucial step for further practical applications.

  7. Krüppel-like factor 9 promotes hepatic cytochrome P450 2D6 expression during pregnancy in CYP2D6-humanized mice.

    PubMed

    Koh, Kwi Hye; Pan, Xian; Zhang, Wei; McLachlan, Alan; Urrutia, Raul; Jeong, Hyunyoung

    2014-12-01

    Cytochrome P450 2D6 (CYP2D6), a major drug-metabolizing enzyme, is responsible for metabolism of approximately 25% of marketed drugs. Clinical evidence indicates that metabolism of CYP2D6 substrates is increased during pregnancy, but the underlying mechanisms remain unclear. To identify transcription factors potentially responsible for CYP2D6 induction during pregnancy, a panel of genes differentially expressed in the livers of pregnant versus nonpregnant CYP2D6-humanized (tg-CYP2D6) mice was compiled via microarray experiments followed by real-time quantitative reverse-transcription polymerase chain reaction(qRT-PCR) verification. As a result, seven transcription factors-activating transcription factor 5 (ATF5), early growth response 1 (EGR1), forkhead box protein A3 (FOXA3), JUNB, Krüppel-like factor 9 (KLF9), KLF10, and REV-ERBα-were found to be up-regulated in liver during pregnancy. Results from transient transfection and promoter reporter gene assays indicate that KLF9 itself is a weak transactivator of CYP2D6 promoter but significantly enhances CYP2D6 promoter transactivation by hepatocyte nuclear factor 4 (HNF4α), a known transcriptional activator of CYP2D6 expression. The results from deletion and mutation analysis of CYP2D6 promoter activity identified a KLF9 putative binding motif at -22/-14 region to be critical in the potentiation of HNF4α-induced transactivation of CYP2D6. Electrophoretic mobility shift assays revealed a direct binding of KLF9 to the putative KLF binding motif. Results from chromatin immunoprecipitation assay showed increased recruitment of KLF9 to CYP2D6 promoter in the livers of tg-CYP2D6 mice during pregnancy. Taken together, our data suggest that increased KLF9 expression is in part responsible for CYP2D6 induction during pregnancy via the potentiation of HNF4α transactivation of CYP2D6.

  8. 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

  9. 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

    2016-02-06

    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.

  10. 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).

  11. Numerical modelling of spallation in 2D hydrodynamics codes

    NASA Astrophysics Data System (ADS)

    Maw, J. R.; Giles, A. R.

    1996-05-01

    A model for spallation based on the void growth model of Johnson has been implemented in 2D Lagrangian and Eulerian hydrocodes. The model has been extended to treat complete separation of material when voids coalesce and to describe the effects of elevated temperatures and melting. The capabilities of the model are illustrated by comparison with data from explosively generated spall experiments. Particular emphasis is placed on the prediction of multiple spall effects in weak, low melting point, materials such as lead. The correlation between the model predictions and observations on the strain rate dependence of spall strength is discussed.

  12. Fracture surfaces of heterogeneous materials: A 2D solvable model

    NASA Astrophysics Data System (ADS)

    Katzav, E.; Adda-Bedia, M.; Derrida, B.

    2007-05-01

    Using an elastostatic description of crack growth based on the Griffith criterion and the principle of local symmetry, we present a stochastic model describing the propagation of a crack tip in a 2D heterogeneous brittle material. The model ensures the stability of straight cracks and allows for the study of the roughening of fracture surfaces. When neglecting the effect of the nonsingular stress, the problem becomes exactly solvable and yields analytic predictions for the power spectrum of the paths. This result suggests an alternative to the conventional power law analysis often used in the analysis of experimental data.

  13. Murine cytomegalovirus regulation of NKG2D ligands.

    PubMed

    Lenac, Tihana; Arapović, Jurica; Traven, Luka; Krmpotić, Astrid; Jonjić, Stipan

    2008-06-01

    Human cytomegalovirus (HCMV) is a ubiquitous pathogen that causes morbidity risk in immunologically suppressed and immunodeficient patients including congenital infections. Approaches to curb the consequences of HCMV infections are restricted by a lack of complete understanding of viral pathogenesis. The infection of mice with murine cytomegalovirus (MCMV) as a model of HCMV infection has been particularly useful in elucidating the role of innate and adaptive immune response mechanisms. A large number of cytomegalovirus genes modulate the innate and the adaptive host immune response. The products of several MCMV genes are involved in subverting the natural killer (NK) cell response by down-modulating cellular ligands for the NKG2D receptor expressed on NK cells and CD8(+) T cells. Mutant viruses lacking these immunoevasion genes are attenuated with respect to virus growth in vivo. Given the importance of the NKG2D receptor in controlling both NK- and T cell-mediated immunity, it is of tremendous importance to understand the molecular mechanisms and consequences of viral regulation of the NKG2D ligands.

  14. Compatible embedding for 2D shape animation.

    PubMed

    Baxter, William V; Barla, Pascal; Anjyo, Ken-Ichi

    2009-01-01

    We present new algorithms for the compatible embedding of 2D shapes. Such embeddings offer a convenient way to interpolate shapes having complex, detailed features. Compared to existing techniques, our approach requires less user input, and is faster, more robust, and simpler to implement, making it ideal for interactive use in practical applications. Our new approach consists of three parts. First, our boundary matching algorithm locates salient features using the perceptually motivated principles of scale-space and uses these as automatic correspondences to guide an elastic curve matching algorithm. Second, we simplify boundaries while maintaining their parametric correspondence and the embedding of the original shapes. Finally, we extend the mapping to shapes' interiors via a new compatible triangulation algorithm. The combination of our algorithms allows us to demonstrate 2D shape interpolation with instant feedback. The proposed algorithms exhibit a combination of simplicity, speed, and accuracy that has not been achieved in previous work.

  15. 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.

  16. Extrinsic Cation Selectivity of 2D Membranes

    PubMed Central

    2017-01-01

    From a systematic study of the concentration driven diffusion of positive and negative ions across porous 2D membranes of graphene and hexagonal boron nitride (h-BN), we prove their cation selectivity. Using the current–voltage characteristics of graphene and h-BN monolayers separating reservoirs of different salt concentrations, we calculate the reversal potential as a measure of selectivity. We tune the Debye screening length by exchanging the salt concentrations and demonstrate that negative surface charge gives rise to cation selectivity. Surprisingly, h-BN and graphene membranes show similar characteristics, strongly suggesting a common origin of selectivity in aqueous solvents. For the first time, we demonstrate that the cation flux can be increased by using ozone to create additional pores in graphene while maintaining excellent selectivity. We discuss opportunities to exploit our scalable method to use 2D membranes for applications including osmotic power conversion. PMID:28157333

  17. Static & Dynamic Response of 2D Solids

    SciTech Connect

    Lin, Jerry

    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 surface 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.

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

    PubMed

    Vijayakumar, Paul Priyesh; Muriana, Peter M

    2015-06-11

    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.

  19. Influence of surface hydroxylation on 3-aminopropyltriethoxysilane growth mode during chemical functionalization of GaN Surfaces: an angle-resolved X-ray photoelectron spectroscopy Study.

    PubMed

    Arranz, A; Palacio, C; García-Fresnadillo, D; Orellana, G; Navarro, A; Muñoz, E

    2008-08-19

    A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown on sapphire substrates by metal-organic chemical vapor deposition was carried out. Both types of samples were chemically functionalized with 3-aminopropyltriethoxysilane (APTES) using a well-established silane-based approach for functionalizing hydroxylated surfaces. The untreated surfaces as well as those modified by hydroxylation and APTES deposition were analyzed using angle-resolved X-ray photoelectron spectroscopy. Strong differences were found between the APTES growth modes on n- and p-GaN surfaces that can be associated with the number of available hydroxyl groups on the GaN surface of each sample. Depending on the density of surface hydroxyl groups, different mechanisms of APTES attachment to the GaN surface take place in such a way that the APTES growth mode changes from a monolayer to a multilayer growth mode when the number of surface hydroxyl groups is decreased. Specifically, a monolayer growth mode with a surface coverage of approximately 78% was found on p-GaN, whereas the formation of a dense film, approximately 3 monolayers thick, was observed on n-GaN.

  20. Quasiparticle interference in unconventional 2D systems

    NASA Astrophysics Data System (ADS)

    Chen, Lan; Cheng, Peng; Wu, Kehui

    2017-03-01

    At present, research of 2D systems mainly focuses on two kinds of materials: graphene-like materials and transition-metal dichalcogenides (TMDs). Both of them host unconventional 2D electronic properties: pseudospin and the associated chirality of electrons in graphene-like materials, and spin-valley-coupled electronic structures in the TMDs. These exotic electronic properties have attracted tremendous interest for possible applications in nanodevices in the future. Investigation on the quasiparticle interference (QPI) in 2D systems is an effective way to uncover these properties. In this review, we will begin with a brief introduction to 2D systems, including their atomic structures and electronic bands. Then, we will discuss the formation of Friedel oscillation due to QPI in constant energy contours of electron bands, and show the basic concept of Fourier-transform scanning tunneling microscopy/spectroscopy (FT-STM/STS), which can resolve Friedel oscillation patterns in real space and consequently obtain the QPI patterns in reciprocal space. In the next two parts, we will summarize some pivotal results in the investigation of QPI in graphene and silicene, in which systems the low-energy quasiparticles are described by the massless Dirac equation. The FT-STM experiments show there are two different interference channels (intervalley and intravalley scattering) and backscattering suppression, which associate with the Dirac cones and the chirality of quasiparticles. The monolayer and bilayer graphene on different substrates (SiC and metal surfaces), and the monolayer and multilayer silicene on a Ag(1 1 1) surface will be addressed. The fifth part will introduce the FT-STM research on QPI in TMDs (monolayer and bilayer of WSe2), which allow us to infer the spin texture of both conduction and valence bands, and present spin-valley coupling by tracking allowed and forbidden scattering channels.

  1. 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.

  2. 2D Metals by Repeated Size Reduction.

    PubMed

    Liu, Hanwen; Tang, Hao; Fang, Minghao; Si, Wenjie; Zhang, Qinghua; Huang, Zhaohui; Gu, Lin; Pan, Wei; Yao, Jie; Nan, Cewen; Wu, Hui

    2016-10-01

    A general and convenient strategy for manufacturing freestanding metal nanolayers is developed on large scale. By the simple process of repeatedly folding and calendering stacked metal sheets followed by chemical etching, free-standing 2D metal (e.g., Ag, Au, Fe, Cu, and Ni) nanosheets are obtained with thicknesses as small as 1 nm and with sizes of the order of several micrometers.

  3. 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.

  4. 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.

  5. Irreversibility-inversions in 2D turbulence

    NASA Astrophysics Data System (ADS)

    Bragg, Andrew; de Lillo, Filippo; Boffetta, Guido

    2016-11-01

    We consider a recent theoretical prediction that for inertial particles in 2D turbulence, the nature of the irreversibility of their pair dispersion inverts when the particle inertia exceeds a certain value. In particular, when the particle Stokes number, St , is below a certain value, the forward-in-time (FIT) dispersion should be faster than the backward-in-time (BIT) dispersion, but for St above this value, this should invert so that BIT becomes faster than FIT dispersion. This non-trivial behavior arises because of the competition between two physically distinct irreversibility mechanisms that operate in different regimes of St . In 3D turbulence, both mechanisms act to produce faster BIT than FIT dispersion, but in 2D, the two mechanisms have opposite effects because of the inverse energy cascade in the turbulent velocity field. We supplement the qualitative argument given by Bragg et al. by deriving quantitative predictions of this effect in the short-time dispersion limit. These predictions are then confirmed by results of inertial particle dispersion in a direct numerical simulation of 2D turbulence.

  6. Epitaxial Growth of GaN Films by Pulse-Mode Hot-Mesh Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Komae, Yasuaki; Yasui, Kanji; Suemitsu, Maki; Endoh, Tetsuo; Ito, Takashi; Nakazawa, Hideki; Narita, Yuzuru; Takata, Masasuke; Akahane, Tadashi

    2009-07-01

    Intermittent gas supplies for hot-mesh chemical vapor deposition (CVD) for the epitaxial growth of gallium nitride (GaN) films were investigated to improve film crystallinity and optical properties. The GaN films were deposited on SiC/Si(111) substrates using an alternating-source gas supply or an intermittent supply of source gases such as ammonia (NH3) and trimethylgallium (TMG) in hot-mesh CVD after deposition of an aluminum nitride (AlN) buffer layer. The AlN layer was deposited using NH3 and trimethylaluminum (TMA) on a SiC layer grown by carbonization of a Si substrate using propane (C3H8). GaN films were grown on the AlN layer by a reaction between NHx radicals generated on a ruthenium (Ru)-coated tungsten (W) mesh and TMG molecules. After testing various gas supply modes, GaN films with good crystallinity and surface morphology were obtained using an intermittent supply of TMG and a continuous supply of NH3 gas. An optimal interval for the TMG gas supply was also obtained for the apparatus employed.

  7. 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

  8. 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

  9. 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.

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

    PubMed

    Wang, Zenghui; Feng, Philip X-L

    2016-07-28

    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. Effects of Trophic Modes, Carbon Sources, and Salinity on the Cell Growth and Lipid Accumulation of Tropic Ocean Oilgae Strain Desmodesmus sp. WC08.

    PubMed

    Zhao, Zhenyu; Ma, Shasha; Li, Ang; Liu, Pinghuai; Wang, Meng

    2016-10-01

    The effects of trophic modes, carbon sources, and salinity on the growth and lipid accumulation of a marine oilgae Desmodesmus sp. WC08 in different trophic cultures were assayed by single factor experiment based on the blue-green algae medium (BG-11). The results implied that biomass and lipid accumulation culture process were optimized depending on the tophic modes, sorts, and concentration of carbon sources and salinity in the cultivation. There was no significant difference in growth or lipid accumulation with Na2CO3 amendment or NaHCO3 amendment. However, Na2CO3 amendment did enhance the biomass and lipid accumulation to some extent. The highest Desmodesmus sp. WC08 biomass and lipid accumulation was achieved in the growth medium with photoautotrophic cultivation, 0.08 g L(-1) Na2CO3 amendment and 15 g L(-1) sea salt, respectively.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Codon Constraints on Closed 2D Shapes,

    DTIC Science & Technology

    2014-09-26

    19843$ CODON CONSTRAINTS ON CLOSED 2D SHAPES Go Whitman Richards "I Donald D. Hoffman’ D T 18 Abstract: Codons are simple primitives for describing plane...RSONAL AUT"ORtIS) Richards, Whitman & Hoffman, Donald D. 13&. TYPE OF REPORT 13b. TIME COVERED N/A P8 AT F RRrT t~r. Ago..D,) is, PlE COUNT Reprint...outlines, if figure and ground are ignored. Later, we will address the problem of indexing identical codon descriptors that have different figure

  17. Meshfree natural vibration analysis of 2D structures

    NASA Astrophysics Data System (ADS)

    Kosta, Tomislav; Tsukanov, Igor

    2014-02-01

    Determination of resonance frequencies and vibration modes of mechanical structures is one of the most important tasks in the product design procedure. The main goal of this paper is to describe a pioneering application of the solution structure method (SSM) to 2D structural natural vibration analysis problems and investigate the numerical properties of the method. SSM is a meshfree method which enables construction of the solutions to the engineering problems that satisfy exactly all prescribed boundary conditions. This method is capable of using spatial meshes that do not conform to the shape of a geometric model. Instead of using the grid nodes to enforce boundary conditions, it employs distance fields to the geometric boundaries and combines them with the basis functions and prescribed boundary conditions at run time. This defines unprecedented geometric flexibility of the SSM as well as the complete automation of the solution procedure. In the paper we will explain the key points of the SSM as well as investigate the accuracy and convergence of the proposed approach by comparing our results with the ones obtained using analytical methods or traditional finite element analysis. Despite in this paper we are dealing with 2D in-plane vibrations, the proposed approach has a straightforward generalization to model vibrations of 3D structures.

  18. 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.

  19. 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.

  20. Remarks on thermalization in 2D CFT

    NASA Astrophysics Data System (ADS)

    de Boer, Jan; Engelhardt, Dalit

    2016-12-01

    We revisit certain aspects of thermalization in 2D conformal field theory (CFT). In particular, we consider similarities and differences between the time dependence of correlation functions in various states in rational and non-rational CFTs. We also consider the distinction between global and local thermalization and explain how states obtained by acting with a diffeomorphism on the ground state can appear locally thermal, and we review why the time-dependent expectation value of the energy-momentum tensor is generally a poor diagnostic of global thermalization. Since all 2D CFTs have an infinite set of commuting conserved charges, generic initial states might be expected to give rise to a generalized Gibbs ensemble rather than a pure thermal ensemble at late times. We construct the holographic dual of the generalized Gibbs ensemble and show that, to leading order, it is still described by a Banados-Teitelboim-Zanelli black hole. The extra conserved charges, while rendering c <1 theories essentially integrable, therefore seem to have little effect on large-c conformal field theories.

  1. 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.

  2. 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.

  3. Two Ingredients for My Dinner with R2D2: Integration and Adjustable Autonomy

    DTIC Science & Technology

    2000-01-01

    robotics and multi-modal interface research; namely, how crucial integration of multiple modes of communication are for adjustable autonomy, which in...turn is crucial for having dinner with R2D2. Furthermore, we discuss how our multi- modal interface to autonomous robots addresses these issues by...tracking goals, allowing for both natural and mechanical modes of input, and how our robotic system adjusts itself to ensure that goals are achieved

  4. Scale-free behavior of a 2D complex plasma during rapid cooling.

    PubMed

    Knapek, C A; Durniak, C; Samsonov, D; Morfill, G E

    2013-01-18

    Experimental evidence is presented for a scale-free transition from an unordered to an ordered state in a 2D complex plasma that differs from the KTHNY theory of phase transitions in 2D systems. The transition is characterized by the formation and growth of ordered domains. A fractal relationship is found between the domain areas and domain boundary lengths, which can be explained by a recent theoretical model. The experimental findings are supported by a molecular dynamics simulation of a 2D particle system.

  5. 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

  6. HI Intensity Mapping: Parkes-2dFGRS and BAO science

    NASA Astrophysics Data System (ADS)

    Li, Yi-Chao; Staveley-Smith, Lister; Pen, Ue-Li; Chang, Tzu-Ching; Peterson, Jeff; Bandura, Kevin; Chen, Xuelei; Wang, Xin; Price, Danny; Montero-Castano, Maria; Anderson, Christopher; Voytek, Tabitha; Masui, Kiyoshi; Switzer, Eric; Wu, Feng-Quan; Timbie, Peter; Liao, Yu-Wei Victor; Li, zhigang

    2012-10-01

    We propose to scan the 2dF survey field with Parkes multibeam in driftscan mode to make a map of cosmological large scale structure. This allows a statistical detection of HI large scale structure out to z=0.15. In this cross correlation, the HI in ALL galaxies contributes, not only the bright ones, which significantly boosts the sensitivity.

  7. 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.

  8. Transition to turbulence: 2D directed percolation

    NASA Astrophysics Data System (ADS)

    Chantry, Matthew; Tuckerman, Laurette; Barkley, Dwight

    2016-11-01

    The transition to turbulence in simple shear flows has been studied for well over a century, yet in the last few years has seen major leaps forward. In pipe flow, this transition shows the hallmarks of (1 + 1) D directed percolation, a universality class of continuous phase transitions. In spanwisely confined Taylor-Couette flow the same class is found, suggesting the phenomenon is generic to shear flows. However in plane Couette flow the largest simulations and experiments to-date find evidence for a discrete transition. Here we study a planar shear flow, called Waleffe flow, devoid of walls yet showing the fundamentals of planar transition to turbulence. Working with a quasi-2D yet Navier-Stokes derived model of this flow we are able to attack the (2 + 1) D transition problem. Going beyond the system sizes previously possible we find all of the required scalings of directed percolation and thus establish planar shears flow in this class.

  9. 2D quantum gravity from quantum entanglement.

    PubMed

    Gliozzi, F

    2011-01-21

    In quantum systems with many degrees of freedom the replica method is a useful tool to study the entanglement of arbitrary spatial regions. We apply it in a way that allows them to backreact. As a consequence, they become dynamical subsystems whose position, form, and extension are determined by their interaction with the whole system. We analyze, in particular, quantum spin chains described at criticality by a conformal field theory. Its coupling to the Gibbs' ensemble of all possible subsystems is relevant and drives the system into a new fixed point which is argued to be that of the 2D quantum gravity coupled to this system. Numerical experiments on the critical Ising model show that the new critical exponents agree with those predicted by the formula of Knizhnik, Polyakov, and Zamolodchikov.

  10. 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.

  11. 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).

  12. 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.

  13. 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.

  14. 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.

  15. Experimental and theoretical studies of active control of resistive wall mode growth in the EXTRAP T2R reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Drake, J. R.; Brunsell, P. R.; Yadikin, D.; Cecconello, M.; Malmberg, J. A.; Gregoratto, D.; Paccagnella, R.; Bolzonella, T.; Manduchi, G.; Marrelli, L.; Ortolani, S.; Spizzo, G.; Zanca, P.; Bondeson, A.; Liu, Y. Q.

    2005-07-01

    Active feedback control of resistive wall modes (RWMs) has been demonstrated in the EXTRAP T2R reversed-field pinch experiment. The control system includes a sensor consisting of an array of magnetic coils (measuring mode harmonics) and an actuator consisting of a saddle coil array (producing control harmonics). Closed-loop (feedback) experiments using a digital controller based on a real time Fourier transform of sensor data have been studied for cases where the feedback gain was constant and real for all harmonics (corresponding to an intelligent-shell) and cases where the feedback gain could be set for selected harmonics, with both real and complex values (targeted harmonics). The growth of the dominant RWMs can be reduced by feedback for both the intelligent-shell and targeted-harmonic control systems. Because the number of toroidal positions of the saddle coils in the array is half the number of the sensors, it is predicted and observed experimentally that the control harmonic spectrum has sidebands. Individual unstable harmonics can be controlled with real gains. However if there are two unstable mode harmonics coupled by the sideband effect, control is much less effective with real gains. According to the theory, complex gains give better results for (slowly) rotating RWMs, and experiments support this prediction. In addition, open loop experiments have been used to observe the effects of resonant field errors applied to unstable, marginally stable and robustly stable modes. The observed effects of field errors are consistent with the thin-wall model, where mode growth is proportional to the resonant field error amplitude and the wall penetration time for that mode harmonic.

  16. Numerical investigation of 3D effects on a 2D-dominated shocked mixing layer

    NASA Astrophysics Data System (ADS)

    Reese, Daniel; Weber, Christopher

    2016-11-01

    A nominally two-dimensional interface, unstable to the Rayleigh-Taylor or Richtmyer-Meshkov instability, will become three-dimensional at high Reynolds numbers due to the growth of background noise and 3D effects like vortex stretching. This three-dimensionality changes macroscopic features, such as the perturbation growth rate and mixing, as it enhances turbulent dissipation. In this study, a 2D perturbation with small-scale, 3D fluctuations is modeled using the hydrodynamics code Miranda. A Mach 1.95 shockwave accelerates a helium-over-SF6 interface, similar to the experiments of Motl et al. ["Experimental validation of a Richtmyer-Meshkov scaling law over large density ratio and shock strength ranges," Phys. Fluids 21(12), 126102 (2009)], to explore the regime where a 2D dominated flow will experience 3D effects. We report on the structure, growth, and mixing of the post-shocked interface in 2D and 3D.

  17. HfSe2 thin films: 2D transition metal dichalcogenides grown by molecular beam epitaxy.

    PubMed

    Yue, Ruoyu; Barton, Adam T; Zhu, Hui; Azcatl, Angelica; Pena, Luis F; Wang, Jian; Peng, Xin; Lu, Ning; Cheng, Lanxia; Addou, Rafik; McDonnell, Stephen; Colombo, Luigi; Hsu, Julia W P; Kim, Jiyoung; Kim, Moon J; Wallace, Robert M; Hinkle, Christopher L

    2015-01-27

    In this work, we demonstrate the growth of HfSe2 thin films using molecular beam epitaxy. The relaxed growth criteria have allowed us to demonstrate layered, crystalline growth without misfit dislocations on other 2D substrates such as highly ordered pyrolytic graphite and MoS2. The HfSe2 thin films exhibit an atomically sharp interface with the substrates used, followed by flat, 2D layers with octahedral (1T) coordination. The resulting HfSe2 is slightly n-type with an indirect band gap of ∼ 1.1 eV and a measured energy band alignment significantly different from recent DFT calculations. These results demonstrate the feasibility and significant potential of fabricating 2D material based heterostructures with tunable band alignments for a variety of nanoelectronic and optoelectronic applications.

  18. 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

  19. 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.

  20. Evidence of critical cooling rates in the nonisothermal crystallization of triacylglycerols: a case for the existence and selection of growth modes of a lipid crystal network.

    PubMed

    Bouzidi, Laziz; Narine, Suresh S

    2010-03-16

    The isoconversional method, a model-free analysis of the kinetics of liquid-solid transformations, was used to determine the effective activation energy of the nonisothermal crystallization of melts of pure and complex systems of triacylglycerols (TAGs). The method was applied to data from differential scanning calorimetry (DSC) measurements of the heat of crystallization of purified 1,3-dilauroyl-2-stearoyl-sn-glycerol (LSL) and commercially available cocoa butter melts. The method conclusively demonstrated the existence of specific growth modes and critical rates of cooling at specific degrees of conversion. The existence of critical rates suggests that the crystallization mechanism is composed of growth modes that can be effectively treated as mutually exclusive, each being predominant for one range of cooling rates and extent of conversion. Importantly, the data suggests that knowledge of the critical cooling rates at specific rates of conversion can be exploited to select preferred growth modes for lipid networks, with concomitant benefits of structural organization and resultant physical functionality. Differences in transport phenomena induced by different cooling rates suggest the existence of thresholds for particular growth mechanisms and help to explain the overall complexity of lipid crystallization. The results of this model-free analysis may be attributed to the relative importance of nucleation and growth at different stages of crystallization. A mechanistic explanation based on the competing effects of the thermodynamic driving force and limiting heat and transport phenomena is provided to explain the observed behavior. This work, furthermore, offers satisfactory explanations for the noted effect of cooling-rate-induced changes in the physical functionality of lipid networks.

  1. CASTOR3D: linear stability studies for 2D and 3D tokamak equilibria

    NASA Astrophysics Data System (ADS)

    Strumberger, E.; Günter, S.

    2017-01-01

    The CASTOR3D code, which is currently under development, is able to perform linear stability studies for 2D and 3D, ideal and resistive tokamak equilibria in the presence of ideal and resistive wall structures and coils. For these computations ideal equilibria represented by concentric nested flux surfaces serve as input (e.g. computed with the NEMEC code). Solving an extended eigenvalue problem, the CASTOR3D code takes simultaneously plasma inertia and wall resistivity into account. The code is a hybrid of the CASTOR_3DW stability code and the STARWALL code. The former is an extended version of the CASTOR and CASTOR_FLOW code, respectively. The latter is a linear 3D code computing the growth rates of resistive wall modes in the presence of multiply-connected wall structures. The CASTOR_3DW code, and some parts of the STARWALL code have been reformulated in a general 3D flux coordinate representation that allows to choose between various types of flux coordinates. Furthermore, the implemented many-valued current potentials in the STARWALL part allow a correct treatment of the m  =  0, n  =  0 perturbation. In this paper, we outline the theoretical concept, and present some numerical results which illustrate the present status of the code and demonstrate its numerous application possibilities.

  2. Variable growth modes of CaF2 on Si(111) determined by x-ray photoelectron diffraction

    NASA Astrophysics Data System (ADS)

    Denlinger, J. D.; Rotenberg, Eli; Hessinger, Uwe; Leskovar, M.; Olmstead, Marjorie A.

    1993-04-01

    Chemical discrimination of bulk and interface Ca 2p x-ray photoelectron diffraction modulations is used to identify three growth regimes during the initial stages of CaF2 epitaxy on Si(111). Low flux, high temperature conditions produce island growth atop a nonwetting, chemically reacted Ca-F interface layer. Changing the growth kinetics by increasing the flux produces more laminar growth. Lowering the substrate temperature produces a more stoichiometric CaF2 interface layer that results in immediate wetting and laminar growth.

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

    PubMed

    Morishita, Yoshihiro; Kuroiwa, Atsushi; Suzuki, Takayuki

    2015-05-01

    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.

  4. Persistence Measures for 2d Soap Froth

    NASA Astrophysics Data System (ADS)

    Feng, Y.; Ruskin, H. J.; Zhu, B.

    Soap froths as typical disordered cellular structures, exhibiting spatial and temporal evolution, have been studied through their distributions and topological properties. Recently, persistence measures, which permit representation of the froth as a two-phase system, have been introduced to study froth dynamics at different length scales. Several aspects of the dynamics may be considered and cluster persistence has been observed through froth experiment. Using a direct simulation method, we have investigated persistent properties in 2D froth both by monitoring the persistence of survivor cells, a topologically independent measure, and in terms of cluster persistence. It appears that the area fraction behavior for both survivor and cluster persistence is similar for Voronoi froth and uniform froth (with defects). Survivor and cluster persistent fractions are also similar for a uniform froth, particularly when geometries are constrained, but differences observed for the Voronoi case appear to be attributable to the strong topological dependency inherent in cluster persistence. Survivor persistence, on the other hand, depends on the number rather than size and position of remaining bubbles and does not exhibit the characteristic decay to zero.

  5. SEM signal emulation for 2D patterns

    NASA Astrophysics Data System (ADS)

    Sukhov, Evgenii; Muelders, Thomas; Klostermann, Ulrich; Gao, Weimin; Braylovska, Mariya

    2016-03-01

    The application of accurate and predictive physical resist simulation is seen as one important use model for fast and efficient exploration of new patterning technology options, especially if fully qualified OPC models are not yet available at an early pre-production stage. The methodology of using a top-down CD-SEM metrology to extract the 3D resist profile information, such as the critical dimension (CD) at various resist heights, has to be associated with a series of presumptions which may introduce such small, but systematic CD errors. Ideally, the metrology effects should be carefully minimized during measurement process, or if possible be taken into account through proper metrology modeling. In this paper we discuss the application of a fast SEM signal emulation describing the SEM image formation. The algorithm is applied to simulated resist 3D profiles and produces emulated SEM image results for 1D and 2D patterns. It allows estimating resist simulation quality by comparing CDs which were extracted from the emulated and from the measured SEM images. Moreover, SEM emulation is applied for resist model calibration to capture subtle error signatures through dose and defocus. Finally, it should be noted that our SEM emulation methodology is based on the approximation of physical phenomena which are taking place in real SEM image formation. This approximation allows achieving better speed performance compared to a fully physical model.

  6. 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.

  7. 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

  8. Gene expression studies of mRNAs encoding the NMDA receptor subunits NMDAR1, NMDAR2A, NMDAR2B, NMDAR2C, and NMDAR2D following long-term treatment with cis-and trans-flupenthixol as a model for understanding the mode of action of schizophrenia drug treatment.

    PubMed

    Chen, A C; McDonald, B; Moss, S J; Gurling, H M

    1998-02-01

    It has been hypothesized that glutamate receptor function is important in both the aetiology and treatment of schizophrenia. In order to understand how specific glutamate receptor genes are involved in the treatment of schizophrenia we have used a multiprobe oligonucleotide solution hybridization (MOSH) technique to examine the regulation of gene express of the NMDAR1, 2A, 2B, 2C, 2D receptor subunits in the left rat brain following treatment with the optical isomers of flupenthixol. cis- and trans-flupenthixol are both present in the commonly used oral and depot treatments for schizophrenia and a controlled trial showed that cis-flupenthixol had a significantly superior ability to ameliorate the positive symptoms of schizophrenia compared to its trans-isomer. At a dose of 0.2 mg/kg/day over a period of 1, 2, 4, 8, 12 and 24 weeks, we found that both isomers down regulated the expression of NMDAR1 mRNA in most regions of the brain. NMDAR2A, 2B and 2C receptor subunits showed a significantly decreased expression from 12 to 24 weeks but after 2 weeks NMDAR2B, 2C, 2D expression was increased in several brain regions. The NMDAR1 receptor subunit immunoreactivity in the right brain following 4 and 24 weeks of drug treatment was also examined by Western blotting. Both trans- and cis-flupenthixol significantly decreased the NR1 immunoreactivity in the right cerebellum after 24 weeks of treatment. These results suggest that NMDA receptor subunits may have a role in the action of antipsychotic drugs. If we assume that the NMDA receptor expression changes reflect a beneficial and significant mechanism in the treatment of schizophrenia, it could be argued that NMDA receptor changes are more related to the negative or non-specific symptoms of schizophrenia.

  9. Substrate-assisted 2D DNA lattices and algorithmic lattices from single-stranded tiles.

    PubMed

    Kim, Junghoon; Ha, Tai Hwan; Park, Sung Ha

    2015-08-07

    We present a simple route to circumvent kinetic traps which affect many types of DNA nanostructures in their self-assembly process. Using this method, a new 2D DNA lattice made up of short, single-stranded tile (SST) motifs was created. Previously, the growth of SST DNA assemblies was restricted to 1D (tubes and ribbons) or finite-sized 2D (molecular canvases). By utilizing the substrate-assisted growth method, sets of SSTs were designed as unit cells to self-assemble into periodic and aperiodic 2D lattices which continuously grow both along and orthogonal to the helical axis. Notably, large-scale (∼1 μm(2)) fully periodic 2D lattices were fabricated using a minimum of just 2 strand species. Furthermore, the ability to create 2D lattices from a few motifs enables certain rules to be encoded into these SSTs to carry out algorithmic self-assembly. A set of these motifs was designed to execute simple 1-input 1-output COPY and NOT algorithms, the space-time manifestations which were aperiodic 2D algorithmic SST lattices. The methodology presented here can be straightforwardly applied to other motifs which fall into this type of kinetic trap to create novel DNA crystals.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. Low 2D:4D Values Are Associated with Video Game Addiction

    PubMed Central

    Kornhuber, Johannes; Zenses, Eva-Maria; Lenz, Bernd; Stoessel, Christina; Bouna-Pyrrou, Polyxeni; Rehbein, Florian; Kliem, Sören; Mößle, Thomas

    2013-01-01

    Androgen-dependent signaling regulates the growth of the fingers on the human hand during embryogenesis. A higher androgen load results in lower 2D:4D (second digit to fourth digit) ratio values. Prenatal androgen exposure also impacts brain development. 2D:4D values are usually lower in males and are viewed as a proxy of male brain organization. Here, we quantified video gaming behavior in young males. We found lower mean 2D:4D values in subjects who were classified according to the CSAS-II as having at-risk/addicted behavior (n = 27) compared with individuals with unproblematic video gaming behavior (n = 27). Thus, prenatal androgen exposure and a hyper-male brain organization, as represented by low 2D:4D values, are associated with problematic video gaming behavior. These results may be used to improve the diagnosis, prediction, and prevention of video game addiction. PMID:24236143

  15. Low 2D:4D values are associated with video game addiction.

    PubMed

    Kornhuber, Johannes; Zenses, Eva-Maria; Lenz, Bernd; Stoessel, Christina; Bouna-Pyrrou, Polyxeni; Rehbein, Florian; Kliem, Sören; Mößle, Thomas

    2013-01-01

    Androgen-dependent signaling regulates the growth of the fingers on the human hand during embryogenesis. A higher androgen load results in lower 2D:4D (second digit to fourth digit) ratio values. Prenatal androgen exposure also impacts brain development. 2D:4D values are usually lower in males and are viewed as a proxy of male brain organization. Here, we quantified video gaming behavior in young males. We found lower mean 2D:4D values in subjects who were classified according to the CSAS-II as having at-risk/addicted behavior (n = 27) compared with individuals with unproblematic video gaming behavior (n = 27). Thus, prenatal androgen exposure and a hyper-male brain organization, as represented by low 2D:4D values, are associated with problematic video gaming behavior. These results may be used to improve the diagnosis, prediction, and prevention of video game addiction.

  16. 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.

  17. 2D discrete Fourier transform on sliding windows.

    PubMed

    Park, Chun-Su

    2015-03-01

    Discrete Fourier transform (DFT) is the most widely used method for determining the frequency spectra of digital signals. In this paper, a 2D sliding DFT (2D SDFT) algorithm is proposed for fast implementation of the DFT on 2D sliding windows. The proposed 2D SDFT algorithm directly computes the DFT bins of the current window using the precalculated bins of the previous window. Since the proposed algorithm is designed to accelerate the sliding transform process of a 2D input signal, it can be directly applied to computer vision and image processing applications. The theoretical analysis shows that the computational requirement of the proposed 2D SDFT algorithm is the lowest among existing 2D DFT algorithms. Moreover, the output of the 2D SDFT is mathematically equivalent to that of the traditional DFT at all pixel positions.

  18. 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.

  19. 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

  20. MAGNUM2D. Radionuclide Transport Porous Media

    SciTech Connect

    Langford, D.W.; Baca, R.G.

    1989-03-01

    MAGNUM2D was developed to analyze thermally driven fluid motion in the deep basalts below the Paco Basin at the Westinghouse Hanford Site. Has been used in the Basalt Waste Isolation Project to simulate nonisothermal groundwater flow in a heterogeneous anisotropic medium and heat transport in a water/rock system near a high level nuclear waste repository. Allows three representations of the hydrogeologic system: an equivalent porous continuum, a system of discrete, unfilled, and interconnecting fractures separated by impervious rock mass, and a low permeability porous continuum with several discrete, unfilled fractures traversing the medium. The calculations assume local thermodynamic equilibrium between the rock and groundwater, nonisothermal Darcian flow in the continuum portions of the rock, and nonisothermal Poiseuille flow in discrete unfilled fractures. In addition, the code accounts for thermal loading within the elements, zero normal gradient and fixed boundary conditions for both temperature and hydraulic head, and simulation of the temperature and flow independently. The Q2DGEOM preprocessor was developed to generate, modify, plot and verify quadratic two dimensional finite element geometries. The BCGEN preprocessor generates the boundary conditions for head and temperature and ICGEN generates the initial conditions. The GRIDDER postprocessor interpolates nonregularly spaced nodal flow and temperature data onto a regular rectangular grid. CONTOUR plots and labels contour lines for a function of two variables and PARAM plots cross sections and time histories for a function of time and one or two spatial variables. NPRINT generates data tables that display the data along horizontal or vertical cross sections. VELPLT differentiates the hydraulic head and buoyancy data and plots the velocity vectors. The PATH postprocessor plots flow paths and computes the corresponding travel times.

  1. MAGNUM2D. Radionuclide Transport Porous Media

    SciTech Connect

    Langford, D.W.; Baca, R.G.

    1988-08-01

    MAGNUM2D was developed to analyze thermally driven fluid motion in the deep basalts below the Paco Basin at the Westinghouse Hanford Site. Has been used in the Basalt Waste Isolation Project to simulate nonisothermal groundwater flow in a heterogeneous anisotropic medium and heat transport in a water/rock system near a high level nuclear waste repository. Allows three representations of the hydrogeologic system: an equivalent porous continuum, a system of discrete, unfilled, and interconnecting fractures separated by impervious rock mass, and a low permeability porous continuum with several discrete, unfilled fractures traversing the medium. The calculation assumes local thermodynamic equilibrium between the rock and groundwater, nonisothermal Darcian flow in the continuum portions of the rock, and nonisothermal Poiseuille flow in discrete unfilled fractures. In addition, the code accounts for thermal loading within the elements, zero normal gradient and fixed boundary conditions for both temperature and hydraulic head, and simulation of the temperature and flow independently. The Q2DGEOM preprocessor was developed to generate, modify, plot and verify quadratic two dimensional finite element geometries. The BCGEN preprocessor generates the boundary conditions for head and temperature and ICGEN generates the initial conditions. The GRIDDER postprocessor interpolates nonregularly spaced nodal flow and temperature data onto a regular rectangular grid. CONTOUR plots and labels contour lines for a function of two variables and PARAM plots cross sections and time histories for a function of time and one or two spatial variables. NPRINT generates data tables that display the data along horizontal or vertical cross sections. VELPLT differentiates the hydraulic head and buoyancy data and plots the velocity vectors. The PATH postprocessor plots flow paths and computes the corresponding travel times.

  2. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Hallquist, J. O.; Sanford, Larry

    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.

  3. 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.

  4. NIKE2D96. Static & Dynamic Response of 2D Solids

    SciTech Connect

    Raboin, P.; Engelmann, B.; Halquist, J.O.

    1992-01-24

    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 surface 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.

  5. 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.

  6. 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

    2016-02-05

    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.

  7. Representativeness of 2D models to simulate 3D unstable variable density flow in porous media

    NASA Astrophysics Data System (ADS)

    Knorr, Bastian; Xie, Yueqing; Stumpp, Christine; Maloszewski, Piotr; Simmons, Craig T.

    2016-11-01

    Variable density flow in porous media has been studied primarily using numerical models because it is a semi-chaotic and transient process. Most of these studies have been 2D, owing to the computational restrictions on 3D simulations, and the ability to observe variable density flow in 2D experimentation. However, it is recognised that variable density flow is a three-dimensional process. A 3D system may cause weaker variable density flow than a 2D system due to stronger dispersion, but may also result in bigger fingers and hence stronger variable density flow because of more space for fingers to coalesce. This study aimed to determine the representativeness of 2D modelling to simulate 3D variable density flow. 3D homogeneous sand column experiments were conducted at three different water flow velocities with three different bromide tracer solutions mixed with methanol resulting in different density ratios. Both 2D axisymmetric and 3D numerical simulations were performed to reproduce experimental data. Experimental results showed that the magnitude of variable density flow increases with decreasing flow rates and decreasing density ratios. The shapes of the observed breakthrough curves differed significantly from those produced by 2D axisymmetric and 3D simulations. Compared to 2D simulations, the onset of instabilities was delayed but the growth was more pronounced in 3D simulations. Despite this difference, both 2D axisymmetric and 3D models successfully simulated mass recovery with high efficiency (between 77% and 99%). This study indicates that 2D simulations are sufficient to understand integrated features of variable density flow in homogeneous sand column experiments.

  8. 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

  9. Investigation of fast particle driven instabilities by 2D electron cyclotron emission imaging on ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Classen, I. G. J.; Lauber, Ph; Curran, D.; Boom, J. E.; Tobias, B. J.; Domier, C. W.; Luhmann, N. C., Jr.; Park, H. K.; Garcia Munoz, M.; Geiger, B.; Maraschek, M.; Van Zeeland, M. A.; da Graça, S.; ASDEX Upgrade Team

    2011-12-01

    Detailed measurements of the 2D mode structure of Alfvén instabilities in the current ramp-up phase of neutral beam heated discharges were performed on ASDEX Upgrade, using the electron cyclotron emission imaging (ECEI) diagnostic. This paper focuses on the observation of reversed shear Alfvén eigenmodes (RSAEs) and bursting modes that, with the use of the information from ECEI, have been identified as beta-induced Alfvén eigenmodes (BAEs). Both RSAEs with first and second radial harmonic mode structures were observed. Calculations with the linear gyro-kinetic code LIGKA revealed that the ratio of the damping rates and the frequency difference between the first and second harmonic modes strongly depended on the shape of the q-profile. The bursting character of the BAE type modes, which were radially localized to rational q surfaces, was observed to sensitively depend on the plasma parameters, ranging from strongly bursting to almost steady state.

  10. Tight-Binding Approximations in 1D and 2D Coupled-Cavity Photonic Crystal Structures

    NASA Astrophysics Data System (ADS)

    Day, Nicole C. L.

    Light confinement and controlling an optical field has numerous applications in the field of telecommunications for optical signals processing. When the wavelength of the electromagnetic field is on the order of the period of a photonic microstructure, the field undergoes reflection, refraction, and coherent scattering. This produces photonic bandgaps, forbidden frequency regions or spectral stop bands where light cannot exist. Dielectric perturbations that break the perfect periodicity of these structures produce what is analogous to an impurity state in the bandgap of a semiconductor. The defect modes that exist at discrete frequencies within the photonic bandgap are spatially localized about the cavity-defects in the photonic crystal. In this thesis the properties of two tight-binding approximations (TBAs) are investigated in one-dimensional and two-dimensional coupled-cavity photonic crystal structures. We require an efficient and simple approach that ensures the continuity of the electromagnetic field across dielectric interfaces in complex structures. In this thesis we develop E- and D-TBAs to calculate the modes in finite 1D and 2D two-defect coupled-cavity photonic crystal structures. In the E- and D-TBAs we expand the coupled-cavity [vector electron]-modes in terms of the individual [vector electron]- and [vector D meson]-modes, respectively. We investigate the dependence of the defect modes, their frequencies and quality factors on the relative placement of the defects in the photonic crystal structures. We then elucidate the differences between the two TBA formulations, and describe the conditions under which these formulations may be more robust when encountering a dielectric perturbation. Our 1D analysis showed that the 1D modes were sensitive to the structure geometry. The antisymmetric D mode amplitudes show that the D. TBA did not capture the correct (tangential [vector electron]-field) boundary conditions. However, the D-TBA did not yield

  11. Stability of two-dimensional (2D) natural convection flows in air-filled differentially heated cavities: 2D/3D disturbances

    NASA Astrophysics Data System (ADS)

    Xin, Shihe; Le Quéré, Patrick

    2012-06-01

    Following our previous two-dimensional (2D) studies of flows in differentially heated cavities filled with air, we studied the stability of 2D natural convection flows in these cavities with respect to 3D periodic perturbations. The basis of the numerical methods is a time-stepping code using the Chebyshev spectral collocation method and the direct Uzawa method for velocity-pressure coupling. Newton's iteration, Arnoldi's method and the continuation method have been used in order to, respectively, compute the 2D steady-state base solution, estimate the leading eigenmodes of the Jacobian and perform linear stability analysis. Differentially heated air-filled cavities of aspect ratios from 1 to 7 were investigated. Neutral curves (Rayleigh number versus wave number) have been obtained. It turned out that only for aspect ratio 7, 3D stationary instability occurs at slightly higher Rayleigh numbers than the onset of 2D time-dependent flow and that for other aspect ratios 3D instability always takes place before 2D time-dependent flows. 3D unstable modes are stationary and anti-centro-symmetric. 3D nonlinear simulations revealed that the corresponding pitchfork bifurcations are supercritical and that 3D instability leads only to weak flow in the third direction. Further 3D computations are also performed at higher Rayleigh number in order to understand the effects of the weak 3D fluid motion on the onset of time-dependent flow. 3D flow structures are responsible for the onset of time-dependent flow for aspect ratios 1, 2 and 3, while for larger aspect ratios they do not alter the transition scenario, which was observed in the 2D cases and that vertical boundary layers become unstable to traveling waves.

  12. Fas-ligand-mediated paracrine T cell regulation by the receptor NKG2D in tumor immunity.

    PubMed

    Groh, Veronika; Smythe, Kimberly; Dai, Zhenpeng; Spies, Thomas

    2006-07-01

    Tumor-associated ligands of the activating NKG2D receptor can effectively stimulate T cell responses at early but not late stages of tumor growth. In late-stage human tumor settings, we observed MIC-driven proliferation of NKG2D(+)CD4(+) T cells that produced the cytokine Fas ligand (FasL) as a result of NKG2D costimulation but were themselves protected from Fas-mediated growth arrest. In contrast, FasL suppressed proliferation of T cells in vitro that did not receive NKG2D costimulation. Similar observations with normal peripheral blood NKG2D(+)CD8(+) T cells demonstrated unrecognized NKG2D-mediated immune functions, whereby FasL release promotes tumor cell death and NKG2D costimulation prolongs T cell survival. These effects, beneficial in conditions of limited NKG2D ligand expression, may be counterweighed when massive expression and shedding of MIC occurs, such as in some late-stage tumors, that causes sustained NKG2D costimulation and population expansion of immunosuppressive T cells.

  13. Advanced Photoemission Spectroscopy Investigations Correlated with DFT Calculations on the Self-Assembly of 2D Metal Organic Frameworks Nano Thin Films.

    PubMed

    Elzein, Radwan; Chang, Chun-Min; Ponomareva, Inna; Gao, Wen-Yang; Ma, Shengqian; Schlaf, Rudy

    2016-11-16

    Metal-organic frameworks (MOFs) deposited from solution have the potential to form 2-dimensional supramolecular thin films suitable for molecular electronic applications. However, the main challenges lie in achieving selective attachment to the substrate surface, and the integration of organic conductive ligands into the MOF structure to achieve conductivity. The presented results demonstrate that photoemission spectroscopy combined with preparation in a system-attached glovebox can be used to characterize the electronic structure of such systems. The presented results demonstrate that porphyrin-based 2D MOF structures can be produced and that they exhibit similar electronic structure to that of corresponding conventional porphyrin thin films. Porphyrin MOF multilayer thin films were grown on Au substrates prefunctionalized with 4-mercaptopyridine (MP) via incubation in a glovebox, which was connected to an ultrahigh vacuum system outfitted with photoelectron spectroscopy. The thin film growth process was carried out in several sequential steps. In between individual steps the surface was characterized by photoemission spectroscopy to determine the valence bands and evaluate the growth mode of the film. A comprehensive evaluation of X-ray photoemission spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and inverse photoemission spectroscopy (IPES) data was performed and correlated with density functional theory (DFT) calculations of the density of states (DOS) of the films involved to yield the molecular-level insights into the growth and the electronic properties of MOF-based 2D thin films.

  14. 2D crossed electric field for electrokinetic remediation of chromium contaminated soil.

    PubMed

    Zhang, Peng; Jin, Chunji; Zhao, Zhenhuan; Tian, Guobin

    2010-05-15

    Chromium contaminated soil can be remediated by electrokinetic techniques. However, in practical application, Cr(VI) may migrate with water deep into the soil, contaminating previously unpolluted layers. Both horizontal and vertical electric fields were applied simultaneously to improve traditional electrokinetic remediation. Contrasting experiments using four operation modes (none, solely horizontal, solely vertical and 2D crossed electric field) were designed and tested at the bench-scale with the practical sample of chromium contaminated soil (1.3 x 10(5)mg/kg) from a chemical plant to investigate Cr(VI) migration downward in each test and the effectiveness and feasible of the new design. During the tests, Cr(VI) could migrate deep into the soil in the solely horizontal mode. Cr(VI) migration downward could be prevented by vertical barrier in the solely vertical mode. However, using the 2D crossed mode, Cr(VI) was significantly prevented from migrating downward and the chromium contaminated soil was treated effectively. Thus, the 2D crossed electric field is a promising and practical method for the remediation of contaminated soils.

  15. Relative performance of biofilm configuration over suspended growth operation on azo dye based wastewater treatment in periodic discontinuous batch mode operation.

    PubMed

    Mohan, S Venkata; Reddy, C Nagendranatha; Kumar, A Naresh; Modestra, J Annie

    2013-11-01

    Functional role of biofilm and suspended growth bioreactor configurations in response to the treatment of azo-dye (C.I. Acid Black 10B) bearing wastewater was evaluated in periodic discontinuous batch mode operation at varying dye concentrations. The biofilm system depicted higher dye removal efficiency (93.14%) compared to suspended mode (84.29%) at 350 mg dye/l operation. Both the reactor configurations did not show much process inhibition at higher dye loads studied. Azo reductase and dehydrogenase enzyme activities showed significant variation indicating the different metabolic capabilities of the native-microflora, stable proton shuttling between metabolic intermediates and differences in the delivery of reducing powers from the substrate metabolism towards dye removal. Voltammograms visualized marked variations in electron discharge properties with the function of reactor configuration, time intervals and dye load. Higher redox catalytic currents, lower Tafel slopes and polarization resistance showed good correlation with enzyme activities and dye removal.

  16. 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.

  17. Multifunctional 2D- Materials: Selenides and Halides

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Su, Ching Hua; Arnold, Brad; Choa, Fow-Sen; Bohorfous, Sara

    2016-01-01

    Material is the key component and controls the performance of the detectors, devices and sensors. The materials design, processing, growth and fabrication of bulk and nanocrystals and fabrication into devices and sensors involve multidisciplinary team of experts. This places a large burden on the cost of the novel materials development. Due to this reason there is a big thrust for the prediction of multifunctionality of materials before design and development. Up to some extent design can achieve certain properties. In multinary materials processing is also a big factor. In this presentation, examples of two classes of industrially important materials will be described.

  18. SPA-LEED Study of the Morphology and Nucleation of a Novel Growth Mode and the ''devil's staircase'' on Pb/Si(111)

    SciTech Connect

    Yeh, Wang-Chi Vincent

    2003-01-01

    This thesis was developed to address the following questions for the Pb/Si(111) system: (1) Is it possible to control the nano-structure growth by changing the initial substrate; (2) is the nucleation theory applicable to the case of the 7-step growth mode; and (3) what phase or phases could be formed between coverage 6/5 ML and 4/3 ML? The first question was answered in chapter 2, different growth results were observed for different initial substrate, suggesting the possibility of controlling nano-structure growth by selecting the initial substrate. The applicability of nucleation theory was determined to be unclear in chapter 3, from the results that the saturation island density does not depend on deposition rate, in contrary to the prediction of nucleation theory. Chapter 4 revealed a novel ''devil's staircase'' in Pb/Si(111) within the coverage range 6/5 ML and 4/3 ML. Low temperature deposition experiments showed high order of self-organization in such a system. Theoretical studies are needed to understand such a low temperature behavior. In general, this thesis provides possibilities of controlling nano-structure growth, which can be possibly an indication for future application. It also raises interesting questions in fundamental researches: a modified theory of nucleation is needed, and a detailed study of low temperature behavior is required. Details of the conclusions in each of the chapters are collected in the following sections.

  19. 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.

  20. Construction of cuprous oxide electrodes composed of 2D single-crystalline dendritic nanosheets.

    PubMed

    Jang, Ho Seong; Kim, Suk Jun; Choi, Kyoung-Shin

    2010-10-04

    An unusual anisotropic growth of Cu(2)O is stabilized via the electrochemical synthesis of Cu(2)O in the presence of Ag(+) ions, which results in the formation of Cu(2)O electrodes composed of 2D sheetlike crystals containing complex dendritic patterns. It is quite unusual for Cu(2)O to form a 2D morphology since it has a 3D isotropic cubic crystal structure where the a, b, and c axes are equivalent. Each Cu(2)O sheet is single-crystalline in nature and is grown parallel to the {110} plane, which is rarely observed in Cu(2)O crystal shapes. A various set of experiments are performed to understand the role of Ag(+) ions on the 2D growth of Cu(2)O. The results show that Ag(+) ions are deposited as silver islands on already growing Cu(2)O crystals and serve as nucleation sites for the new growth of Cu(2)O crystals. As a result, the growth direction of the newly forming Cu(2)O crystals is governed by the diffusion layer structure created by the pre-existing Cu(2)O crystals, which results in the formation of 2D dendritic patterns. The thin 2D crystal morphology can significantly increase the surface-to-volume ratio of Cu(2)O crystals, which is beneficial for enhancing various electrochemical and photoelectrochemical properties of the electrodes. The photoelectrochemical properties of the Cu(2)O electrodes composed of 2D dendritic crystals are investigated and compared to those of 3D dendritic crystals. This study provides a unique and effective route to maximize the {110} area per unit volume of Cu(2)O, which will be beneficial for any catalytic/sensing abilities that can be anisotropically enhanced by the {110} planes of Cu(2)O.

  1. Antiproliferative action of menadione and 1,25(OH)2D3 on breast cancer cells.

    PubMed

    Marchionatti, Ana M; Picotto, Gabriela; Narvaez, Carmen J; Welsh, Joellen; Tolosa de Talamoni, Nori G

    2009-02-01

    Calcitriol or 1,25(OH)(2)D(3) is a negative growth regulator of MCF-7 breast cancer cells. The growth arrest is due to apoptosis activation, which involves mitochondrial disruption. This effect is blunted in vitamin D resistant cells (MCF-7(DRes) cells). Menadione (MEN), a glutathione (GSH)-depleting compound, may potentiate antitumoral effects of anticancer drugs. The aim of this study was to investigate whether MEN enhances cellular responsiveness of MCF-7 cells to 1,25(OH)(2)D(3). Cells were cultured and treated with different concentrations of 1,25(OH)(2)D(3)+/-MEN or vehicle for 96 h. GSH levels and the activity of antioxidant enzymes were determined by spectrophotometry and ROS production by flow cytometry. Both drugs decreased growth and enhanced ROS in MCF-7 cells, obtaining the maximal effects when 1,25(OH)(2)D(3) was combined with MEN (P<0.01 vs. Control and vs. each compound alone). MCF-7(DRes) cells were not responsive to 1,25(OH)(2)D(3), but the cell proliferation was slightly inhibited by the combined treatment. Calcitriol and MEN separately enhanced antioxidant enzyme activities, but when they were used in combination, the effect was more pronounced (P<0.05 vs. Control and vs. each compound alone). MEN, calcitriol and the combined treatment decreased GSH levels (P<0.05 vs. Control). The data indicate that MEN potentiates the effect of 1,25(OH)(2)D(3) on growth arrest in MCF-7 cells by oxidative stress and increases the activities of antioxidant enzymes, probably as a compensatory mechanism.

  2. 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.

  3. 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

  4. 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

  5. Effects of dietary fructooligosaccharide levels and feeding modes on growth, immune responses, antioxidant capability and disease resistance of blunt snout bream (Megalobrama amblycephala).

    PubMed

    Zhang, Chun-Nuan; Li, Xiang-Fei; Jiang, Guang-Zhen; Zhang, Ding-Dong; Tian, Hong-Yan; Li, Jun-Yi; Liu, Wen-Bin

    2014-12-01

    This study aimed to determine the effects of fructooligosaccharide (FOS) levels and its feeding modes on growth, immune response, antioxidant capability and disease resistance of blunt snout bream (Megalobrama amblycephala). Fish (12.5 ± 0.5 g) were subjected to three FOS levels (0, 0.4% and 0.8%) and two feeding modes (supplementing FOS continuously and supplementing FOS two days interval 5 days) according to a 3 × 2 factorial design. At the end of 8-week feeding trial, fish were challenged by Aeromonas hydrophila with concentration of 1 × 10(5) CFU mL(-1) and mortality was recorded for the next 96 h. Fish fed 0.4% FOS continuously (D2) and fish fed the basal diet for 5 days followed by 0.8% FOS for 2 days (D5) showed admirable growth performance. The highest plasma lysozyme, acid phosphatase and myeloperoxidase activities as well as complement component 3, total protein and immunoglobulin M (IgM) levels were all observed in fish fed D5. They were significantly higher (P < 0.05) than those of the control group and/or fish fed 0.8% FOS continuously, but exhibited no statistical difference (P > 0.05) with that of fish fed D2. A similar trend was also observed in antioxidant capability as well as the expression of Leap-I and Leap-Ⅱ. Mortality showed an opposite trend with the immune response with the lowest rate observed in fish fed D5. The results indicated that diet supplementing FOS in appropriate levels and feeding modes could improve the growth, immune response and antioxidant capability of fish, as might consequently lead to enhanced disease resistance. It can be speculated that the basal diet for 5 days followed by 0.8% FOS for 2 days was most suitable for blunt snout bream.

  6. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires

    DOE PAGES

    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.

  7. 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.

  8. 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

    2016-03-04

    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.

  9. 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.

  10. Nonlinear standing waves in 2-D acoustic resonators.

    PubMed

    Cervenka, Milan; Bednarik, Michal

    2006-12-22

    This paper deals with 2-D simulation of finite-amplitude standing waves behavior in rectangular acoustic resonators. Set of three partial differential equations in third approximation formulated in conservative form is derived from fundamental equations of gas dynamics. These equations form a closed set for two components of acoustic velocity vector and density, the equations account for external driving force, gas dynamic nonlinearities and thermoviscous dissipation. Pressure is obtained from solution of the set by means of an analytical formula. The equations are formulated in the Cartesian coordinate system. The model equations set is solved numerically in time domain using a central semi-discrete difference scheme developed for integration of sets of convection-diffusion equations with two or more spatial coordinates. Numerical results show various patterns of acoustic field in resonators driven using vibrating piston with spatial distribution of velocity. Excitation of lateral shock-wave mode is observed when resonant conditions are fulfilled for longitudinal as well as for transversal direction along the resonator cavity.

  11. 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.

  12. 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.

  13. 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.

  14. [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.

  15. 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.

  16. In situ doping of catalyst-free InAs nanowires with Si: Growth, polytypism, and local vibrational modes of Si

    NASA Astrophysics Data System (ADS)

    Dimakis, Emmanouil; Ramsteiner, Manfred; Huang, Chang-Ning; Trampert, Achim; Davydok, Anton; Biermanns, Andreas; Pietsch, Ullrich; Riechert, Henning; Geelhaar, Lutz

    2013-09-01

    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-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.

  17. 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.

  18. Differential CYP 2D6 metabolism alters primaquine pharmacokinetics.

    PubMed

    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; Marcsisin, Sean R

    2015-04-01

    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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Calcium-dependent activation and autolysis of Arabidopsis metacaspase 2d.

    PubMed

    Watanabe, Naohide; Lam, Eric

    2011-03-25

    Metacaspases (MCPs) are members of a new family of cysteine proteases found in plants, fungi, and protozoa that are structurally related to metazoan caspases. Recent studies showed that plant MCPs are arginine/lysine-specific cysteine proteases with caspase-like processing activities in vitro and in vivo, and some of the plant type II MCPs exhibit Ca(2+) dependence for their endopeptidase activity in vitro. However, the mechanisms and biological relevance of Ca(2+) dependence and self-processing of plant MCPs remains unclear. Here we show that recombinant AtMCP2d, the most abundantly expressed member of Arabidopsis type II MCPs at the transcriptional level, exhibits a strict Ca(2+) dependence for its catalytic activation that is apparently mediated by intramolecular self-cleavage mechanism. However, rapid inactivation of AtMCP2d activity concomitant with Ca(2+)-induced self-processing at multiple internal sites was observed. Because active AtMCP2d can cleave its inactive form, intermolecular cleavage (autolysis) of AtMCP2d could also occur under our assay conditions. Ca(2+)-induced self-processing of recombinant AtMCP2d was found to correlate with the sequential appearance of at least six intermediates, including self-cleaved forms, during the proenzyme purification process. Six of these peptides were characterized, and the cleavage sites were mapped through N-terminal protein sequencing. Mutation analysis of AtMCP2d revealed that cleavage after Lys-225, which is a highly conserved residue among the six Arabidopsis type II MCPs, is critical for the catalytic activation by Ca(2+), and we demonstrate that this residue is essential for AtMCP2d activation of H(2)O(2)-induced cell death in yeast. Together, our results provide clues to understand the mode of regulation for this class of proteases.

  4. Epitaxial Growth of Rhenium with Sputtering

    DTIC Science & Technology

    2016-05-06

    islands when a thick film is grown at 850 °C on the seed layer . We also find that when a room temperature deposited Re film is annealed to higher...corresponds to two atomic Re layers , considering that the c-axis lattice constant of the tri- atomic layered hcp Re unit cell is ~4.5 Å. Frequently, two...mode (2D growth) [13]. The initial VW 3D mode can be avoided by use of a seed layer technique [14]. When a thin (2 nm) Re is deposited at room

  5. 2D-ELDOR using full S(c-) fitting and absorption lineshapes.

    PubMed

    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 S(c-) 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 S(c-) signal. The full S(c-) 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 S(c-) 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 S(c-) method" especially for exploring the complexity of model and biological membranes.

  6. 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.

  7. Large area growth of monolayer MoS2 film on quartz and its use as a saturable absorber in laser mode-locking

    NASA Astrophysics Data System (ADS)

    Zhao, Wei-fang; Yu, Hua; Liao, Meng-zhou; Zhang, Ling; Zou, Shu-zhen; Yu, Hai-juan; He, Chao-jian; Zhang, Jing-yuan; Zhang, Guang-yu; Lin, Xue-chun

    2017-02-01

    Monolayer MoS2 film on quartz was fabricated by a home-made three-temperature zone chemical vapor deposition method. The photo, AFM image, Raman spectroscopy and HRTEM image showed that high quality as-grown MoS2 film completely covered the whole quartz substrate of a few cm2. A Nd:YVO4 laser with mode-locking operation was obtained by using the monolayer MoS2 on quartz as the saturable absorber (SA). To the best of our knowledge, this is the first report on large-area growth of high quality monolayer MoS2 film on transparent quartz substrate, and the first time that the CVD MoS2 SA was used in mode-locked solid state lasers. Because of the large area, high transmission, low non-saturable loss and high optical damage threshold of this material, it is very suitable for application in mode-locked solid state lasers.

  8. Growth mode, magnetic and magneto-optical properties of pulsed-laser-deposited Au/Co/Au(1 1 1) trilayers

    NASA Astrophysics Data System (ADS)

    Clavero, C.; Cebollada, A.; Armelles, G.; Fruchart, O.

    2010-03-01

    The growth mode, magnetic and magneto-optical properties of epitaxial Au/Co/Au(1 1 1) ultrathin trilayers grown by pulsed-laser deposition (PLD) under ultra-high vacuum are presented. Sapphire wafers buffered with a single-crystalline Mo(1 1 0) buffer layer were used as substrates. Owing to PLD-induced interfacial intermixing at the lower Co/Au(1 1 1) interface, a close-to layer-by-layer growth mode is promoted. Surprisingly, despite this intermixing, ferromagnetic behavior is found at room temperature for coverings starting at 1 atomic layer (AL). The films display perpendicular magnetization with anisotropy constants reduced by 50% compared to TD-grown or electrodeposited films, and with a coercivity more than one order of magnitude lower (≲5 mT). The magneto-optical (MO) response in the low Co thickness range is dominated by Au/Co interface contributions. For thicknesses starting at 3 AL Co, the MO response has a linear dependence with the Co thickness, indicative of a continuous-film-like MO behavior.

  9. Computational Screening of 2D Materials for Photocatalysis.

    PubMed

    Singh, Arunima K; Mathew, Kiran; Zhuang, Houlong L; Hennig, Richard G

    2015-03-19

    Two-dimensional (2D) materials exhibit a range of extraordinary electronic, optical, and mechanical properties different from their bulk counterparts with potential applications for 2D materials emerging in energy storage and conversion technologies. In this Perspective, we summarize the recent developments in the field of solar water splitting using 2D materials and review a computational screening approach to rapidly and efficiently discover more 2D materials that possess properties suitable for solar water splitting. Computational tools based on density-functional theory can predict the intrinsic properties of potential photocatalyst such as their electronic properties, optical absorbance, and solubility in aqueous solutions. Computational tools enable the exploration of possible routes to enhance the photocatalytic activity of 2D materials by use of mechanical strain, bias potential, doping, and pH. We discuss future research directions and needed method developments for the computational design and optimization of 2D materials for photocatalysis.

  10. 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...

  11. Stabilizing effects on 2D channel flow due to longitudinal wall oscillation

    NASA Astrophysics Data System (ADS)

    Atobe, Takashi

    2017-01-01

    Stabilizing effect of longitudinal wall oscillation on two dimensional channel flow is analytically investigated. Model flow considered here is constituted of a superposition of the plane Poiseuille flow and the Stokes layer. The two walls are periodically oscillated in phase. Since the present system has a periodicity, the Floquet method is employed for the stability analysis. For this, a partial difference equation with a periodic function is derived from the time dependent version of the Orr-Sommerfeld equation using the Chebyshev spectral collocation method. The parameters governing the present system are the Reynolds number Re, the period Ω and amplitude Uw of the wall oscillation. Depending on the parameters, it is found that the 2D Tollmein-Shlichtin (TS) modes can be stabilized by the wall oscillation. Furthermore there are some case that 2D TS modes are more stabilized than the oblique TS mode. These results suggest that the oblique TS mode can appear earlier than the TS mode contrary to the Squire's Theorem.

  12. 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.

  13. Synthetic Covalent and Non-Covalent 2D Materials.

    PubMed

    Boott, Charlotte E; Nazemi, Ali; Manners, Ian

    2015-11-16

    The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers.

  14. Epitaxial 2D SnSe2/ 2D WSe2 van der Waals Heterostructures.

    PubMed

    Aretouli, Kleopatra Emmanouil; Tsoutsou, Dimitra; Tsipas, Polychronis; Marquez-Velasco, Jose; Aminalragia Giamini, Sigiava; Kelaidis, Nicolaos; Psycharis, Vassilis; Dimoulas, Athanasios

    2016-09-07

    van der Waals heterostructures of 2D semiconductor materials can be used to realize a number of (opto)electronic devices including tunneling field effect devices (TFETs). It is shown in this work that high quality SnSe2/WSe2 vdW heterostructure can be grown by molecular beam epitaxy on AlN(0001)/Si(111) substrates using a Bi2Se3 buffer layer. A valence band offset of 0.8 eV matches the energy gap of SnSe2 in such a way that the VB edge of WSe2 and the CB edge of SnSe2 are lined up, making this materials combination suitable for (nearly) broken gap TFETs.

  15. Molecular beam epitaxy of 2D-layered gallium selenide on GaN substrates

    NASA Astrophysics Data System (ADS)

    Lee, Choong Hee; Krishnamoorthy, Sriram; O'Hara, Dante J.; Brenner, Mark R.; Johnson, Jared M.; Jamison, John S.; Myers, Roberto C.; Kawakami, Roland K.; Hwang, Jinwoo; Rajan, Siddharth

    2017-03-01

    Large area epitaxy of two-dimensional (2D) layered materials with high material quality is a crucial step in realizing novel device applications based on 2D materials. In this work, we report high-quality, crystalline, large-area gallium selenide (GaSe) films grown on bulk substrates such as c-plane sapphire and gallium nitride (GaN) using a valved cracker source for Se. (002)-Oriented GaSe with random in-plane orientation of domains was grown on sapphire and GaN substrates at a substrate temperature of 350-450 °C with complete surface coverage. Higher growth temperature (575 °C) resulted in the formation of single-crystalline ɛ-GaSe triangular domains with six-fold symmetry confirmed by in-situ reflection high electron energy diffraction and off-axis x-ray diffraction. A two-step growth method involving high temperature nucleation of single crystalline domains and low temperature growth to enhance coalescence was adopted to obtain continuous (002)-oriented GaSe with an epitaxial relationship with the substrate. While six-fold symmetry was maintained in the two step growth, β-GaSe phase was observed in addition to the dominant ɛ-GaSe in cross-sectional scanning transmission electron microscopy images. This work demonstrates the potential of growing high quality 2D-layered materials using molecular beam epitaxy and can be extended to the growth of other transition metal chalcogenides.

  16. 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.

  17. Interaction mechanism of biomolecules on vacancy defected 2D materials

    NASA Astrophysics Data System (ADS)

    Gürel, Hikmet Hakan; Salmankurt, Bahadır

    2017-02-01

    In this work, we present a first principles study of the adsorption of Adenine which is a nucleobases, Histide and Leucine molecules, which are the amino acids, on vacancy defected single layer materials such as graphene and phosphorene. Among these materials, graphene, which is a single layer honeycomb structure of carbon. Also, phosphorene is recently synthesized by mechanical exfoliation of the black phosphorus. Phosphorene forming a puckered honeycomb structure similar to silicene. However, unlike zero-bandgap graphene and silicene, phosphorene is a direct band gap semiconductor, which makes it very attractive for the nanoelectronic devices. According to the studies, local defects can always exist at any temperature. The most probable defect type is the single vacancy in the single layer honeycomb structures. Vacancy defects can be emerged during growth process and they change the properties of materials significantly. In this study, we show that how to manipulate interaction and binding mechanisms of biomolecules with 2D materials with increased chemical activity by vacancy defects.

  18. Photocarrier transport in 2D macroporous silicon structures

    NASA Astrophysics Data System (ADS)

    Karachevtseva, L.; Onyshchenko, V.; Sachenko, A.

    2010-12-01

    The mechanisms of photocarrier transport through a barrier in the surface space-charge region (SCR) of 2D macroporous silicon structures have been studied at photon energies comparable to that of the silicon indirect band-to-band transition. It was found that the photoconductivity relaxation time was determined by the light modulation of barrier on the macropore surface; as a result, the relaxation itself obeyed the logarithmic law. The temperature dependence of the photoconductivity relaxation time was determined by the thermionic emission mechanism of the current transport in the SCR at temperatures T > 180 K, and by the tunnel current flow at T < 100 K, with temperature-independent tunnelling probability. The photo-emf was found to become saturated or reverse its sign to negative at temperatures below 130 K because of light absorption due to optical transitions via surface electronic states close to the silicon conduction band. In this case, the surface band bending increases due to the growth of a negative charge of the semiconductor surface. The equilibrium electrons in the bulk and photoexcited holes on the macropore surface recombine through the channel of multistage tunnel recombination between the conduction and valence bands.

  19. 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.

  20. 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.

  1. 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,...

  2. Novel Mode of Nucleation and Growth of Complex Oxide Heterostructures at the Extreme of High Supersaturation. Effects of Orbital Reconstruction

    DTIC Science & Technology

    2009-08-31

    adatom population and either facilitates the ease of nucleation (low SS) or for a sufficiently high pulse-rate acts to bound the critical radius to a...temperature and (B) corresponding layer roughness, Δ. The stages of growth marked as 1-3 correspond to the same time- intevals in Fig. 2(A). Supplementary...intervals are defined in Fig. 2(A). Dashed lines represent lower and upper confidence limits. Figure 6: Auxiliary Supplement:(Color online) RHEED

  3. 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.

  4. 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.

  5. Circular photogalvanic effect caused by the transitions between edge and 2D states in a 2D topological insulator

    NASA Astrophysics Data System (ADS)

    Magarill, L. I.; Entin, M. V.

    2016-12-01

    The electron absorption and the edge photocurrent of a 2D topological insulator are studied for transitions between edge states to 2D states. The circular polarized light is found to produce the edge photocurrent, the direction of which is determined by light polarization and edge orientation. It is shown that the edge-state current is found to exceed the 2D current owing to the topological protection of the edge states.

  6. Fabrication and magnetic behaviour of 2D ordered Fe/SiO2 nanodots array

    NASA Astrophysics Data System (ADS)

    Liu, W.; Zhong, W.; Qiu, L. J.; Lü, L. Y.; Du, Y. W.

    2006-06-01

    We have demonstrated a simple and universal morphology-controlled growth of 2D ordered Fe/SiO2 magnetic nanodots array, which was based on 2D colloidal monolayer template composed of polystyrene (PS) spheres and one-step sol-gel spin-coating technique. The Fe/SiO2 nanodots have a well-ordered structure arranged in a hexagonal pattern. The dots have the shape of quasi-pyramidal tetrahedron, which reside in the interstitial region between three PS spheres and the substrate. Magnetic measurements reveal that the nanodots array exhibits the in-plane easy magnetization direction. Compared with the unpatterned Fe/SiO2 thin film, the dots array has lower saturated field, higher remanence and coercivity. The present method is applicable to 2D ordered nanodots array of other magnetic materials.

  7. 2D DEM model of sand transport with wind interaction

    NASA Astrophysics Data System (ADS)

    Oger, L.; Valance, A.

    2013-06-01

    The advance of the dunes in the desert is a threat to the life of the local people. The dunes invade houses, agricultural land and perturb the circulation on the roads. It is therefore very important to understand the mechanism of sand transport in order to fight against desertification. Saltation in which sand grains are propelled by the wind along the surface in short hops, is the primary mode of blown sand movement [1]. The saltating grains are very energetic and when impact a sand surface, they rebound and consequently eject other particles from the sand bed. The ejected grains, called reptating grains, contribute to the augmentation of the sand flux. Some of them can be promoted to the saltation motion. We use a mechanical model based on the Discrete Element Method to study successive collisions of incident energetic beads with granular packing in the context of Aeolian saltation transport. We investigate the collision process for the case where the incident bead and those from the packing have identical mechanical properties. We analyze the features of the consecutive collision processes made by the transport of the saltating disks by a wind in which its profile is obtained from the counter-interaction between air flow and grain flows. We used a molecular dynamics method known as DEM (soft Discrete Element Method) with a initial static packing of 20000 2D particles. The dilation of the upper surface due to the consecutive collisions is responsible for maintaining the flow at a given energy input due to the wind.

  8. 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.

  9. 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

  10. Application of 3D and 2D quantitative shear wave elastography (SWE) to differentiate between benign and malignant breast masses

    PubMed Central

    Tian, Jie; Liu, Qianqi; Wang, Xi; Xing, Ping; Yang, Zhuowen; Wu, Changjun

    2017-01-01

    As breast cancer tissues are stiffer than normal tissues, shear wave elastography (SWE) can locally quantify tissue stiffness and provide histological information. Moreover, tissue stiffness can be observed on three-dimensional (3D) colour-coded elasticity maps. Our objective was to evaluate the diagnostic performances of quantitative features in differentiating breast masses by two-dimensional (2D) and 3D SWE. Two hundred ten consecutive women with 210 breast masses were examined with B-mode ultrasound (US) and SWE. Quantitative features of 3D and 2D SWE were assessed, including elastic modulus standard deviation (ESDE) measured on SWE mode images and ESDU measured on B-mode images, as well as maximum elasticity (Emax). Adding quantitative features to B-mode US improved the diagnostic performance (p < 0.05) and reduced false-positive biopsies (p < 0.0001). The area under the receiver operating characteristic curve (AUC) of 3D SWE was similar to that of 2D SWE for ESDE (p = 0.026) and ESDU (p = 0.159) but inferior to that of 2D SWE for Emax (p = 0.002). Compared with ESDU, ESDE showed a higher AUC on 2D (p = 0.0038) and 3D SWE (p = 0.0057). Our study indicates that quantitative features of 3D and 2D SWE can significantly improve the diagnostic performance of B-mode US, especially 3D SWE ESDE, which shows considerable clinical value. PMID:28106134

  11. Energy Efficiency of D2D Multi-User Cooperation.

    PubMed

    Zhang, Zufan; Wang, Lu; Zhang, Jie

    2017-03-28

    The Device-to-Device (D2D) communication system is an important part of heterogeneous networks. It has great potential to improve spectrum efficiency, throughput and energy efficiency cooperation of multiple D2D users with the advantage of direct communication. When cooperating, D2D users expend extraordinary energy to relay data to other D2D users. Hence, the remaining energy of D2D users determines the life of the system. This paper proposes a cooperation scheme for multiple D2D users who reuse the orthogonal spectrum and are interested in the same data by aiming to solve the energy problem of D2D users. Considering both energy availability and the Signal to Noise Ratio (SNR) of each D2D user, the Kuhn-Munkres algorithm is introduced in the cooperation scheme to solve relay selection problems. Thus, the cooperation issue is transformed into a maximum weighted matching (MWM) problem. In order to enhance energy efficiency without the deterioration of Quality of Service (QoS), the link outage probability is derived according to the Shannon Equation by considering the data rate and delay. The simulation studies the relationships among the number of cooperative users, the length of shared data, the number of data packets and energy efficiency.

  12. 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…

  13. 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.

  14. Adaptation algorithms for 2-D feedforward neural networks.

    PubMed

    Kaczorek, T

    1995-01-01

    The generalized weight adaptation algorithms presented by J.G. Kuschewski et al. (1993) and by S.H. Zak and H.J. Sira-Ramirez (1990) are extended for 2-D madaline and 2-D two-layer feedforward neural nets (FNNs).

  15. Regulation of ligands for the NKG2D activating receptor

    PubMed Central

    Raulet, David H.; Gasser, Stephan; Gowen, Benjamin G.; Deng, Weiwen; Jung, Heiyoun

    2014-01-01

    NKG2D is an activating receptor expressed by all NK cells and subsets of T cells. It serves as a major recognition receptor for detection and elimination of transformed and infected cells and participates in the genesis of several inflammatory diseases. The ligands for NKG2D are self-proteins that are induced by pathways that are active in certain pathophysiological states. NKG2D ligands are regulated transcriptionally, at the level of mRNA and protein stability, and by cleavage from the cell surface. In some cases, ligand induction can be attributed to pathways that are activated specifically in cancer cells or infected cells. We review the numerous pathways that have been implicated in the regulation of NKG2D ligands, discuss the pathologic states in which those pathways are likely to act, and attempt to synthesize the findings into general schemes of NKG2D ligand regulation in NK cell responses to cancer and infection. PMID:23298206

  16. 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.

  17. New generation transistor technologies enabled by 2D crystals

    NASA Astrophysics Data System (ADS)

    Jena, D.

    2013-05-01

    The discovery of graphene opened the door to 2D crystal materials. The lack of a bandgap in 2D graphene makes it unsuitable for electronic switching transistors in the conventional field-effect sense, though possible techniques exploiting the unique bandstructure and nanostructures are being explored. The transition metal dichalcogenides have 2D crystal semiconductors, which are well-suited for electronic switching. We experimentally demonstrate field effect transistors with current saturation and carrier inversion made from layered 2D crystal semiconductors such as MoS2, WS2, and the related family. We also evaluate the feasibility of such semiconducting 2D crystals for tunneling field effect transistors for low-power digital logic. The article summarizes the current state of new generation transistor technologies either proposed, or demonstrated, with a commentary on the challenges and prospects moving forward.

  18. 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.

  19. Antimicrobial growth promoter use in livestock: a requirement to understand their modes of action to develop effective alternatives.

    PubMed

    Brown, Kirsty; Uwiera, Richard R E; Kalmokoff, Martin L; Brooks, Steve P J; Inglis, G Douglas

    2017-01-01

    Antimicrobial agents (AMAs) have been used in agriculture since the 1950s as growth-promoting agents [antimicrobial growth promoters (AGPs)]. They have provided benefits to the agricultural industry by increasing production efficiencies and maximising livestock health, yet the potential risks surrounding resistance to AMAs in medically important pathogenic bacteria have enhanced public and government scrutiny regarding AMA use in agriculture. Although it is recognised that AGP administration can select for resistance to AMAs in enteric bacteria of livestock, conclusive evidence showing a link between resistant bacteria from livestock and human health is lacking (e.g. transmission of resistant zoonotic pathogens). Livestock production output must be increased significantly due to the increase in global population, and thus the identification of non-AMA alternatives to AGP use is required. One strategy employed to identify alternatives to AGPs is an observational empirical methodology, but this approach has failed to deliver effective alternatives. A second approach is aimed at understanding the mechanisms involved in AGP function and developing alternatives that mimic the physiological responses to AGPs. New evidence indicates that AGP function is more complex than merely affecting enteric bacterial populations, and AGPs likely function by directly or indirectly modulating host responses such as the immune system. As such, a more comprehensive understanding of the mechanisms associated with AMA function as AGPs will facilitate the development of effective alternatives.

  20. Estrogen-Induced Cholestasis Leads to Repressed CYP2D6 Expression in CYP2D6-Humanized Mice.

    PubMed

    Pan, Xian; Jeong, Hyunyoung

    2015-07-01

    Cholestasis activates bile acid receptor farnesoid X receptor (FXR) and subsequently enhances hepatic expression of small heterodimer partner (SHP). We previously demonstrated that SHP represses the transactivation of cytochrome P450 2D6 (CYP2D6) promoter by hepatocyte nuclear factor (HNF) 4α. In this study, we investigated the effects of estrogen-induced cholestasis on CYP2D6 expression. Estrogen-induced cholestasis occurs in subjects receiving estrogen for contraception or hormone replacement, or in susceptible women during pregnancy. In CYP2D6-humanized transgenic (Tg-CYP2D6) mice, cholestasis triggered by administration of 17α-ethinylestradiol (EE2) at a high dose led to 2- to 3-fold decreases in CYP2D6 expression. This was accompanied by increased hepatic SHP expression and subsequent decreases in the recruitment of HNF4α to CYP2D6 promoter. Interestingly, estrogen-induced cholestasis also led to increased recruitment of estrogen receptor (ER) α, but not that of FXR, to Shp promoter, suggesting a predominant role of ERα in transcriptional regulation of SHP in estrogen-induced cholestasis. EE2 at a low dose (that does not cause cholestasis) also increased SHP (by ∼ 50%) and decreased CYP2D6 expression (by 1.5-fold) in Tg-CYP2D6 mice, the magnitude of differences being much smaller than that shown in EE2-induced cholestasis. Taken together, our data indicate that EE2-induced cholestasis increases SHP and represses CYP2D6 expression in Tg-CYP2D6 mice in part through ERα transactivation of Shp promoter.

  1. Viscoelastic-damage interface model formulation with friction to simulate the delamination growth in mode II shear

    NASA Astrophysics Data System (ADS)

    Goodarzi, Mohammad Saeed; Hosseini-Toudeshky, Hossein

    2017-02-01

    In this paper a formulation of a viscoelastic-damage interface model with friction in mode-II is presented. The cohesive constitutive law contains elastic and damage regimes. It has been assumed that the shear stress in the elastic regime follows the viscoelastic properties of the matrix material. The three element Voigt model has been used for the formulation of relaxation modulus of the material. Damage evolution proceeds according to the bilinear cohesive constitutive law combined with friction stress consideration. Combination of damage and friction is based on the presumption that the damaged area, related to an integration point, can be dismembered into the un-cracked area with the cohesive damage and cracked area with friction. Samples of a one element model have been presented to see the effect of parameters on the cohesive constitutive law. A comparison between the predicted results with available results of end-notched flexure specimens in the literature is also presented to verify the model. Transverse crack tension specimens are also simulated for different applied displacement velocities.

  2. 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

    2016-08-04

    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.

  3. Structural differences between capped GaSb nanostructures grown by Stranski-Krastanov and droplet epitaxy growth modes

    NASA Astrophysics Data System (ADS)

    DeJarld, Matt; Yan, Lifan; Luengo-Kovac, Marta; Sih, Vanessa; Millunchick, Joanna

    2017-01-01

    Droplet epitaxy (DE) has emerged as an alternative to Stranski-Krastanov (SK) as a method for epitaxial nanostructure formation. We find significant structural differences of similar sized nanostructures embedded in GaAs between the two methods. Atomic force microscopy and atom probe tomography measurements reveal that uncapped and capped SK structures resemble each other. However, the DE nanostructures appear as rings topographically but are quantum dots compositionally. A GaSb wetting layer is present regardless of the growth method and shares a nearly identical Sb concentration profile. DE nanostructures are shown to have a lower Sb concentration, and transmission electron microscopy measurements reveal that they produce less strain on the capping layer. Despite significant structural differences, SK and DE nanostructures exhibit the same photoluminescence response, suggesting that the emission is from a shared feature such as the wetting layer, rather than the nanostructures.

  4. Interface and growth-mode characterization of Ce/Fe and CeH≊2/Fe multilayers by x-ray diffraction and Rutherford backscattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Klose, F.; Steins, M.; Kacsich, T.; Felsch, W.

    1993-07-01

    The detailed structural characterization of ion beam sputtered Ce/Fe and CeH≊2/Fe multilayers offers the possibility for a better understanding of their magnetic properties. In the case of the Ce/Fe multilayers the extension of the interface, as one of the most important features, is determined to 5-7 Å by means of Monte Carlo simulations of the small-angle x-ray scattering diagrams. Below a critical thickness of ≊24 Å Fe grows in an amorphous structure. Here the interface extension is enhanced. In contrast all CeH≊2/Fe multilayers show nearly abrupt interfaces. X-ray scattering experiments at higher angles in reflection and transmission mode provide information about the crystal structure, the texture, and the lateral dimensions of the grains in the samples. Depths profiles of the multilayers are generated by Rutherford backscattering spectroscopy, which confirm the well-ordered periodic structures. Surprisingly indications of an island-like growth mode of the Fe layers onto the Ce and CeH≊2 layers could be resolved by using this procedure.

  5. Growth and Implementation of Carbon-Doped AlGaN Layers for Enhancement-Mode HEMTs on 200 mm Si Substrates

    NASA Astrophysics Data System (ADS)

    Su, Jie; Posthuma, Niels; Wellekens, Dirk; Saripalli, Yoga N.; Decoutere, Stefaan; Arif, Ronald; Papasouliotis, George D.

    2016-12-01

    We are reporting the growth of AlGaN based enhancement-mode high electron mobility transistors (HEMTs) on 200 mm silicon (111) substrates using a single wafer metalorganic chemical vapor deposition reactor. It is found that TMAl pre-dosing conditions are critical in controlling the structural quality, surface morphology, and wafer bow of the HEMT stack. Optimal structural quality and pit-free surface are demonstrated for AlGaN HEMTs with pre-dosing temperature at 750°C. Intrinsically, carbon-doped AlGaN, is used as the current blocking layer in the HEMT structures. The lateral buffer breakdown and device breakdown characteristics, reach 400 V at a leakage current of 1 μA/mm measured at 150°C. The fabricated HEMT devices, with a Mg doped p-GaN gate layer, are operating in enhancement mode reaching a positive threshold voltage of 2-2.5 V, a low on-resistance of 10.5 Ω mm with a high drain saturation current of 0.35 A/mm, and a low forward bias gate leakage current of 0.5 × 10-6 A/mm ( V gs = 7 V). Tight distribution of device parameters across the 200 mm wafers and over repeat process runs is observed.

  6. Effects on Tumor Development and Metastatic Dissemination by the NKG2D Lymphocyte Receptor Expressed on Cancer Cells

    PubMed Central

    El-Gazzar, Ahmed; Cai, Xin; Reeves, Rebecca S.; Dai, Zhenpeng; Caballero-Benitez, Andrea; McDonald, David L.; Vazquez, Julio; Gooley, Ted A.; Sale, George E.; Spies, Thomas; Groh, Veronika

    2014-01-01

    The stimulatory NKG2D lymphocyte receptor together with its tumor-associated ligands enable the immune system to recognize and destroy cancer cells. However, with dynamic changes unfolding, cancers exploit NKG2D and its ligands for immune evasion and suppression. Recent findings have added yet another functional dimension wherein cancer cells themselves coopt NKG2D for their own benefit to complement the presence of its ligands for self stimulation of parameters of tumorigenesis. Those findings are here extended to in vivo tumorigenicity testing by employing orthotopic xenotransplant breast cancer models in mice. Using human cancer lines with ectopic NKG2D expression and RNAi-mediated protein depletion among other controls, we show that NKG2D self-stimulation has tumor promoting capacity. NKG2D signals had no notable effects on cancer cell proliferation and survival but acted at the level of angiogenesis, thus promoting tumor growth, tumor cell intravasation and dissemination. NKG2D-mediated effects on tumor initiation may represent another factor in the observed overall enhancement of tumor development. Altogether, these results may impact immunotherapy approaches, which currently do not account for such NKG2D effects in cancer patients and thus could be misdirected as underlying assumptions are incomplete. PMID:24141776

  7. Effects on tumor development and metastatic dissemination by the NKG2D lymphocyte receptor expressed on cancer cells.

    PubMed

    El-Gazzar, A; Cai, X; Reeves, R S; Dai, Z; Caballero-Benitez, A; McDonald, D L; Vazquez, J; Gooley, T A; Sale, G E; Spies, T; Groh, V

    2014-10-09

    The stimulatory NKG2D lymphocyte receptor together with its tumor-associated ligands enable the immune system to recognize and destroy cancer cells. However, with dynamic changes unfolding, cancers exploit NKG2D and its ligands for immune evasion and suppression. Recent findings have added yet another functional dimension, wherein cancer cells themselves co-opt NKG2D for their own benefit to complement the presence of its ligands for self-stimulation of parameters of tumorigenesis. Those findings are here extended to in vivo tumorigenicity testing by employing orthotopic xenotransplant breast cancer models in mice. Using human cancer lines with ectopic NKG2D expression and RNA interference (RNAi)-mediated protein depletion among other controls, we show that NKG2D self-stimulation has tumor-promoting capacity. NKG2D signals had no notable effects on cancer cell proliferation and survival but acted at the level of angiogenesis, thus promoting tumor growth, tumor cell intravasation and dissemination. NKG2D-mediated effects on tumor initiation may represent another factor in the observed overall enhancement of tumor development. Altogether, these results may have an impact on immunotherapy approaches, which currently do not account for such NKG2D effects in cancer patients and thus could be misdirected as underlying assumptions are incomplete.

  8. 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.

  9. 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.

  10. Evolution of the 2D Spatial Profile of Visible Emission During an ELM in the DIII-D Divertor

    NASA Astrophysics Data System (ADS)

    Fenstermacher, M. E.; Groth, M.; Lasnier, C. J.; Boedo, J. C.; Leonard, A. W.

    2001-10-01

    The transient particle and energy loads due to Edge Localized Modes (ELMs) are a significant problem for the design of divertors in future tokamak reactors. Detailed understanding of the effect of the ELM perturbation on the 2D distribution of radiation in the divertor is needed to validate computer simulations and investigate mitigation schemes. Gated, intensified, tangentially viewing cameras with wavelength filters were used in combination with tomographic reconstruction techniques to provide 2D profiles of carbon and deuterium emission during ELM evolution in the DIII-D divertor. Preliminary 2D reconstructions of D_α and CIII visible emission during large Type-I ELMs will be shown. The dramatic broadening of the D_α emission profile near the target will be compared with the broadening of the heat flux profiles during ELMs from IRTV. Plans for obtaining the detailed temporal evolution of the 2D spatial profile of the divertor emission throughout an ELM will be described.

  11. 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.

  12. 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.

  13. Real-time 2D Imaging of Thermal and Mechanical Tissue Response to Focused Ultrasound

    NASA Astrophysics Data System (ADS)

    Liu, Dalong; Ebbini, Emad S.

    2010-03-01

    An integrated system capable of performing high frame-rate two-dimensional (2D) temperature imaging in realtime is has been developed. The system consists of a SonixRP ultrasound scanner and a custom built data processing unit connected with Gigabit Ethernet (GbE). The SonixRP scanner which serves as the frontend of the integrated system allows us to have flexibilities of controlling the beam sequence and accessing the radio frequency (RF) data in realtime through its research interface. The RF data is then streamlined to the backend of the system through GbE, where the data is processed using a 2D temperature estimation algorithm running in a general purpose graphics processing unit (GPU). Using this system, we have developed a 2D high frame-rate imaging mode, M2D, for imaging the mechanical and thermal tissue response to subtherapeutic HIFU beams. In this paper, we present results from imaging subtherapetic HIFU beams in vitro porcine heart before and after lesion formation. The results demonstrate the feasibility of tissue parameter changes due to HIFU-induced lesions.

  14. 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.

  15. 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.

  16. Joint 2D and 3D phase processing for quantitative susceptibility mapping: application to 2D echo-planar imaging.

    PubMed

    Wei, Hongjiang; Zhang, Yuyao; Gibbs, Eric; Chen, Nan-Kuei; Wang, Nian; Liu, Chunlei

    2017-04-01

    Quantitative susceptibility mapping (QSM) measures tissue magnetic susceptibility and typically relies on time-consuming three-dimensional (3D) gradient-echo (GRE) MRI. Recent studies have shown that two-dimensional (2D) multi-slice gradient-echo echo-planar imaging (GRE-EPI), which is commonly used in functional MRI (fMRI) and other dynamic imaging techniques, can also be used to produce data suitable for QSM with much shorter scan times. However, the production of high-quality QSM maps is difficult because data obtained by 2D multi-slice scans often have phase inconsistencies across adjacent slices and strong susceptibility field gradients near air-tissue interfaces. To address these challenges in 2D EPI-based QSM studies, we present a new data processing procedure that integrates 2D and 3D phase processing. First, 2D Laplacian-based phase unwrapping and 2D background phase removal are performed to reduce phase inconsistencies between slices and remove in-plane harmonic components of the background phase. This is followed by 3D background phase removal for the through-plane harmonic components. The proposed phase processing was evaluated with 2D EPI data obtained from healthy volunteers, and compared against conventional 3D phase processing using the same 2D EPI datasets. Our QSM results were also compared with QSM values from time-consuming 3D GRE data, which were taken as ground truth. The experimental results show that this new 2D EPI-based QSM technique can produce quantitative susceptibility measures that are comparable with those of 3D GRE-based QSM across different brain regions (e.g. subcortical iron-rich gray matter, cortical gray and white matter). This new 2D EPI QSM reconstruction method is implemented within STI Suite, which is a comprehensive shareware for susceptibility imaging and quantification. Copyright © 2016 John Wiley & Sons, Ltd.

  17. 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.

  18. 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

  19. NKG2D Receptor and Its Ligands in Host Defense.

    PubMed

    Lanier, Lewis L

    2015-06-01

    NKG2D is an activating receptor expressed on the surface of natural killer (NK) cells, CD8(+) T cells, and subsets of CD4(+) T cells, invariant NKT cells (iNKT), 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 eight 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 posttranslation. In general, healthy adult tissues do not express NKG2D glycoproteins on the cell surface, but these ligands can be induced by hyperproliferation and transformation, as well as when cells are infected by pathogens. Thus, the NKG2D pathway serves as 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.

  20. Selective inhibition of the cytochrome P450 isoform by hyperoside and its potent inhibition of CYP2D6.

    PubMed

    Song, Min; Hong, Miri; Lee, Min Young; Jee, Jun-Goo; Lee, You Mie; Bae, Jong-Sup; Jeong, Tae Cheon; Lee, Sangkyu

    2013-09-01

    Hyperoside, quercetin-3-O-galactoside, is a flavonoid isolated from Oenanthe javanica. In the present study, we investigated potential herb-drug inhibitory effects of hyperoside on nine cytochrome P450 (CYP) isoforms in pooled human liver microsomes (HLMs) and human recombinant cDNA expressed CYP using a cocktail probe assay. Hyperoside strongly inhibited CYP2D6-catalyzed dextromethorphan O-demethylation, with IC₅₀ values of 1.2 and 0.81 μM after 0 and 15 min of preincubation, and a Ki value of 2.01 μM in HLMs, respectively. Hyperoside strongly decreased CYP2D6 activity dose-, but not time-, dependently in HLMs. In addition, the Lineweaver-Burk and Secondary plots for the inhibition of CYP2D6 in HLMs fitted a competitive inhibition mode. Furthermore, hyperoside decreased CYP2D6-catalyzed dextromethorphan O-demethylation activity of human recombinant cDNA-expressed CYP2D6, with an IC₅₀ value of 3.87 μM. However, other CYPs were not inhibited significantly by hyperoside. In conclusion, our data demonstrate that hyperoside is a potent selective CYP2D6 inhibitor in HLMs, and suggest that hyperoside might cause herb-drug interactions when co-administrated with CYP2D substrates.

  1. Recent advances in 2D materials for photocatalysis.

    PubMed

    Luo, Bin; Liu, Gang; Wang, Lianzhou

    2016-04-07

    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.

  2. 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

  3. 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.

  4. 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

  5. Selenium-Doped Black Phosphorus for High-Responsivity 2D Photodetectors.

    PubMed

    Xu, Yijun; Yuan, Jian; Fei, Linfeng; Wang, Xinliang; Bao, Qiaoliang; Wang, Yu; Zhang, Kai; Zhang, Yuegang

    2016-09-01

    Se-doped black phosphorus (BP) crystal, in centimeter scale, is synthesized by a scalable gas-phase growth method under mild conditions. The Se-doped BP exhibits high quality with excellent electrical properties. The Se dope induces over 20-fold enhancement of responsivity (R) for BP-based 2D photodetectors, resulting in a high R and external quantum efficiency of 15.33 A W(-1) and 2993%, respectively.

  6. Critical slowing down of cluster algorithms for Ising models coupled to 2-d gravity

    NASA Astrophysics Data System (ADS)

    Bowick, Mark; Falcioni, Marco; Harris, Geoffrey; Marinari, Enzo

    1994-02-01

    We simulate single and multiple Ising models coupled to 2-d gravity using both the Swendsen-Wang and Wolff algorithms to update the spins. We study the integrated autocorrelation time and find that there is considerable critical slowing down, particularly in the magnetization. We argue that this is primarily due to the local nature of the dynamical triangulation algorithm and to the generation of a distribution of baby universes which inhibits cluster growth.

  7. The Influence of Prior Modes of Growth, Temperature, Medium, and Substrate Surface on Biofilm Formation by Antibiotic-Resistant Campylobacter jejuni.

    PubMed

    Teh, Amy Huei Teen; Lee, Sui Mae; Dykes, Gary A

    2016-12-01

    Campylobacter jejuni is one of the most common causes of bacterial gastrointestinal food-borne infection worldwide. It has been suggested that biofilm formation may play a role in survival of these bacteria in the environment. In this study, the influence of prior modes of growth (planktonic or sessile), temperatures (37 and 42 °C), and nutrient conditions (nutrient broth and Mueller-Hinton broth) on biofilm formation by eight C. jejuni strains with different antibiotic resistance profiles was examined. The ability of these strains to form biofilm on different abiotic surfaces (stainless steel, glass, and polystyrene) as well as factors potentially associated with biofilm formation (bacterial surface hydrophobicity, auto-aggregation, and initial attachment) was also determined. The results showed that cells grown as sessile culture generally have a greater ability to form biofilm (P < 0.05) compared to their planktonic counterparts. Biofilm was also greater (P < 0.05) in lower nutrient media, while growth at different temperatures affects biofilm formation in a strain-dependent manner. The strains were able to attach and form biofilms on different abiotic surfaces, but none of them demonstrated strong, complex, or structured biofilm formation. There were no clear trends between the bacterial surface hydrophobicity, auto-aggregation, attachment, and biofilm formation by the strains. This finding suggests that environmental factors did affect biofilm formation by C. jejuni, and they are more likely to persist in the environment in the form of mixed-species rather than monospecies biofilms.

  8. 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.

  9. 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.

  10. Influence of exercise contraction mode and protein supplementation on human skeletal muscle satellite cell content and muscle fiber growth.

    PubMed

    Farup, Jean; Rahbek, Stine Klejs; Riis, Simon; Vendelbo, Mikkel Holm; Paoli, Frank de; Vissing, Kristian

    2014-10-15

    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.

  11. 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.

  12. Double resonance rotational spectroscopy of CH2D+

    NASA Astrophysics Data System (ADS)

    Töpfer, Matthias; Jusko, Pavol; Schlemmer, Stephan; Asvany, Oskar

    2016-09-01

    Context. Deuterated forms of CH are thought to be responsible for deuterium enrichment in lukewarm astronomical environments. There is no unambiguous detection of CH2D+ in space to date. Aims: Four submillimetre rotational lines of CH2D+ are documented in the literature. Our aim is to present a complete dataset of highly resolved rotational lines, including millimetre (mm) lines needed for a potential detection. Methods: We used a low-temperature ion trap and applied a novel IR-mm-wave double resonance method to measure the rotational lines of CH2D+. Results: We measured 21 low-lying (J ≤ 4) rotational transitions of CH2D+ between 23 GHz and 1.1 THz with accuracies close to 2 ppb.

  13. Recovering 3D particle size distributions from 2D sections

    NASA Astrophysics Data System (ADS)

    Cuzzi, Jeffrey N.; Olson, Daniel M.

    2017-03-01

    We discuss different ways to convert observed, apparent particle size distributions from 2D sections (thin sections, SEM maps on planar surfaces, etc.) into true 3D particle size distributions. We give a simple, flexible, and practical method to do this; show which of these techniques gives the most faithful conversions; and provide (online) short computer codes to calculate both 2D-3D recoveries and simulations of 2D observations by random sectioning. The most important systematic bias of 2D sectioning, from the standpoint of most chondrite studies, is an overestimate of the abundance of the larger particles. We show that fairly good recoveries can be achieved from observed size distributions containing 100-300 individual measurements of apparent particle diameter.

  14. 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.

  15. Exact Solution of Ising Model in 2d Shortcut Network

    NASA Astrophysics Data System (ADS)

    Shanker, O.

    We give the exact solution to the Ising model in the shortcut network in the 2D limit. The solution is found by mapping the model to the square lattice model with Brascamp and Kunz boundary conditions.

  16. 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.

  17. Reconstruction-based 3D/2D image registration.

    PubMed

    Tomazevic, Dejan; Likar, Bostjan; Pernus, Franjo

    2005-01-01

    In this paper we present a novel 3D/2D registration method, where first, a 3D image is reconstructed from a few 2D X-ray images and next, the preoperative 3D image is brought into the best possible spatial correspondence with the reconstructed image by optimizing a similarity measure. Because the quality of the reconstructed image is generally low, we introduce a novel asymmetric mutual information similarity measure, which is able to cope with low image quality as well as with different imaging modalities. The novel 3D/2D registration method has been evaluated using standardized evaluation methodology and publicly available 3D CT, 3DRX, and MR and 2D X-ray images of two spine phantoms, for which gold standard registrations were known. In terms of robustness, reliability and capture range the proposed method outperformed the gradient-based method and the method based on digitally reconstructed radiographs (DRRs).

  18. 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

    2016-03-09

    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.

  19. 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.

  20. Studying Zeolite Catalysts with a 2D Model System

    SciTech Connect

    Boscoboinik, Anibal

    2016-12-07

    Anibal Boscoboinik, a materials scientist at Brookhaven’s Center for Functional Nanomaterials, discusses the surface-science tools and 2D model system he uses to study catalysis in nanoporous zeolites, which catalyze reactions in many industrial processes.

  1. ORION96. 2-d Finite Element Code Postprocessor

    SciTech Connect

    Sanford, L.A.; Hallquist, J.O.

    1992-02-02

    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 forces 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.

  2. Emerging and potential opportunities for 2D flexible nanoelectronics

    NASA Astrophysics Data System (ADS)

    Zhu, Weinan; Park, Saungeun; Akinwande, Deji

    2016-05-01

    The last 10 years have seen the emergence of two-dimensional (2D) nanomaterials such as graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BP) among the growing portfolio of layered van der Waals thin films. Graphene, the prototypical 2D material has advanced rapidly in device, circuit and system studies that has resulted in commercial large-area applications. In this work, we provide a perspective of the emerging and potential translational applications of 2D materials including semiconductors, semimetals, and insulators that comprise the basic material set for diverse nanosystems. Applications include RF transceivers, smart systems, the so-called internet of things, and neurotechnology. We will review the DC and RF electronic performance of graphene and BP thin film transistors. 2D materials at sub-um channel length have so far enabled cut-off frequencies from baseband to 100GHz suitable for low-power RF and sub-THz concepts.

  3. Two human ULBP/RAET1 molecules with transmembrane regions are ligands for NKG2D.

    PubMed

    Bacon, Louise; Eagle, Robert A; Meyer, Martina; Easom, Nicholas; Young, Neil T; Trowsdale, John

    2004-07-15

    We characterized two novel members of the RAET1/ULBP gene cluster, RAET1E and RAET1G. The encoded proteins were similar to the ULBP in their class I-like alpha1 and alpha2 domains, but differed in that, instead of being GPI-anchored, their sequences were type 1 membrane-spanning molecules. Both proteins were capable of being expressed at the cell surface. Both proteins bound the activating receptor NKG2D, and RAET1G bound the human CMV protein UL16. The expression of diverse NKG2D-binding molecules in different tissues and with different properties is consistent with multiple modes of infection- or stress-induced activation.

  4. Infrared pulsed fiber lasers employing 2D nanomaterials as saturable absorbers

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Li, Heping; Li, Jianfeng

    2016-11-01

    We demonstrate that two kinds of 2D nanomaterials are employed as saturable absorbers to realize infrared pulsed fiber lasers at 1.5 μm and 3 μm, respectively. Mode-locked optical pulses are achieved at 1.5 μm erbium-doped fiber lasers by using multilayer molybdenum disulfide (MoS2). In addition, Q-switched fiber lasers are realized at 3 μm region by using topological insulator: Bi2Te3. Experimental proofs are provided. Our work reveals that 2D nanomaterials like MoS2 and TI: Bi2Te3 are absolutely a class of promising and reliable saturable absorbers for optical pulse generation at infrared waveband.

  5. Nanohole-array-based device for 2D snapshot multispectral imaging.

    PubMed

    Najiminaini, Mohamadreza; Vasefi, Fartash; Kaminska, Bozena; Carson, Jeffrey J L

    2013-01-01

    We present a two-dimensional (2D) snapshot multispectral imager that utilizes the optical transmission characteristics of nanohole arrays (NHAs) in a gold film to resolve a mixture of input colors into multiple spectral bands. The multispectral device consists of blocks of NHAs, wherein each NHA has a unique periodicity that results in transmission resonances and minima in the visible and near-infrared regions. The multispectral device was illuminated over a wide spectral range, and the transmission was spectrally unmixed using a least-squares estimation algorithm. A NHA-based multispectral imaging system was built and tested in both reflection and transmission modes. The NHA-based multispectral imager was capable of extracting 2D multispectral images representative of four independent bands within the spectral range of 662 nm to 832 nm for a variety of targets. The multispectral device can potentially be integrated into a variety of imaging sensor systems.

  6. Modulating the vibronic correlation in 2D superconductor by electric field

    NASA Astrophysics Data System (ADS)

    Kazempour, Ali; Morshedloo, Toktam

    2017-04-01

    Superconductivity in the extreme two-dimensional atomic layers has been suffered because of the strong affection dimensionality confinement on electron-phonon binding. Here, using first-principles method, we study the effect of applied perpendicular and parallel electric field on the strength of phonon renormalization and electron-phonon coupling in bi-layer MgB2 as a known 2D superconductor. The changes of phonon frequency and line-width demonstrate that important E2 g optical modes are strongly sensitive to the applied parallel electric field which directs to sharp reduction of vibronic coupling. Whereas, we show that perpendicular electric field modulates the system to the strong-coupling superconductor and predict the enhancement of critical temperature Tc . Our study opens up the use of electric filed to probe and measure the variation amount of electron-phonon renormalization as a gauge in 2D superconductivity.

  7. Podosomes in space: macrophage migration and matrix degradation in 2D and 3D settings.

    PubMed

    Wiesner, Christiane; Le-Cabec, Véronique; El Azzouzi, Karim; Maridonneau-Parini, Isabelle; Linder, Stefan

    2014-01-01

    Migration of macrophages is a key process for a variety of physiological functions, such as pathogen clearance or tissue homeostasis. However, it can also be part of pathological scenarios, as in the case of tumor-associated macrophages. This review presents an overview of the different migration modes macrophages can adopt, depending on the physical and chemical properties of specific environments, and the constraints they impose upon cells. We discuss the importance of these environmental and also of cellular parameters, as well as their relative impact on macrophage migration and on the formation of matrix-lytic podosomes in 2D and 3D. Moreover, we present an overview of routinely used and also newly developed assays for the study of macrophage migration in both 2D and 3D contexts, their respective advantages and limitations, and also their potential to reliably mimic in vivo situations.

  8. De-Li-DAQ-2D - a new data acquisition system for position-sensitive neutron detectors with delay-line readout

    NASA Astrophysics Data System (ADS)

    Levchanovskiy, F. V.; Murashkevich, S. M.

    2016-09-01

    Software for a data acquisition system of modern one- and two-dimensional position-sensitive detectors with delay-line readout, which includes a software interface to a new electronic module De-Li-DAQ-2D with a USB interface, is presented. The new system after successful tests on the stand and on several spectrometers of the IBR-2 reactor has been integrated into the software complex SONIX+ [1]. The De-Li- DAQ-2D module [2] contains an 8-channel time-code converter (TDC-GPX) with a time resolution of 80 ps, field programmable gate array (FPGA), 1 Gbyte histogram memory and high-speed interface with a fiber-optic communication line. A real count rate is no less than 106 events/s. The De-Li-DAQ-2D module is implemented in the NIM standard. The De-Li-DAQ-2D module can operate in two modes: histogram mode and list mode.

  9. RNA folding pathways and kinetics using 2D energy landscapes.

    PubMed

    Senter, Evan; Dotu, Ivan; Clote, Peter

    2015-01-01

    RNA folding pathways play an important role in various biological processes, such as (i) the hok/sok (host-killing/suppression of killing) system in E. coli to check for sufficient plasmid copy number, (ii) the conformational switch in spliced leader (SL) RNA from Leptomonas collosoma, which controls trans splicing of a portion of the '5 exon, and (iii) riboswitches--portions of the 5' untranslated region of messenger RNA that regulate genes by allostery. Since RNA folding pathways are determined by the energy landscape, we describe a novel algorithm, FFTbor2D, which computes the 2D projection of the energy landscape for a given RNA sequence. Given two metastable secondary structures A, B for a given RNA sequence, FFTbor2D computes the Boltzmann probability p(x, y) = Z(x,y)/Z that a secondary structure has base pair distance x from A and distance y from B. Using polynomial interpolationwith the fast Fourier transform,we compute p(x, y) in O(n(5)) time and O(n(2)) space, which is an improvement over an earlier method, which runs in O(n(7)) time and O(n(4)) space. FFTbor2D has potential applications in synthetic biology, where one might wish to design bistable switches having target metastable structures A, B with favorable pathway kinetics. By inverting the transition probability matrix determined from FFTbor2D output, we show that L. collosoma spliced leader RNA has larger mean first passage time from A to B on the 2D energy landscape, than 97.145% of 20,000 sequences, each having metastable structures A, B. Source code and binaries are freely available for download at http://bioinformatics.bc.edu/clotelab/FFTbor2D. The program FFTbor2D is implemented in C++, with optional OpenMP parallelization primitives.

  10. Supported and Free-Standing 2D Semimetals

    DTIC Science & Technology

    2015-01-15

    of this effort on focusing on rare- earth arsenides (RE-A), although not a van der Waals 2D solid, nonetheless, exhibits substantial 2D quantum size...this effort on focusing on rare- earth arsenides (RE- A), although not a van der Waals 20 solid, nonetheless, exhibits substantial 20 quantum size...Brongersma and S.R. Bank, "Rare- earth monopnictide alloys for tunable, epitaxial metals" in preparation. iii. S. Rahimi, E. M. Krivoy, J. Lee, M. E

  11. Application of 2-D graphical representation of DNA sequence

    NASA Astrophysics Data System (ADS)

    Liao, Bo; Tan, Mingshu; Ding, Kequan

    2005-10-01

    Recently, we proposed a 2-D graphical representation of DNA sequence [Bo Liao, A 2-D graphical representation of DNA sequence, Chem. Phys. Lett. 401 (2005) 196-199]. Based on this representation, we consider properties of mutations and compute the similarities among 11 mitochondrial sequences belonging to different species. The elements of the similarity matrix are used to construct phylogenic tree. Unlike most existing phylogeny construction methods, the proposed method does not require multiple alignment.

  12. phase_space_cosmo_fisher: Fisher matrix 2D contours

    NASA Astrophysics Data System (ADS)

    Stark, Alejo

    2016-11-01

    phase_space_cosmo_fisher produces Fisher matrix 2D contours from which the constraints on cosmological parameters can be derived. Given a specified redshift array and cosmological case, 2D marginalized contours of cosmological parameters are generated; the code can also plot the derivatives used in the Fisher matrix. In addition, this package can generate 3D plots of qH^2 and other cosmological quantities as a function of redshift and cosmology.

  13. A simultaneous