Sample records for diffusive cavity growth

  1. Double diffusive instability in an inclined cavity

    NASA Astrophysics Data System (ADS)

    Bergeon, A.; Ghorayeb, K.; Mojtabi, A.

    1999-03-01

    Double diffusive convection in a rectangular two-dimensional cavity with imposed temperatures and concentrations along two opposite sidewalls is considered. The study is performed for two-dimensional cavities in which the thermal and solutal buoyancy forces have the same magnitude, but are of opposite sign. The influence on the convective instability of the aspect ratio A (height/length) of the cavity and the cavity inclination ? with respect to gravity is discussed. The onset of convection is computed for an infinite layer and compared to that for bounded boxes. The study is completed by the continuation of bifurcating solutions. It is found that, due to centrosymmetry, steady bifurcations are either pitchfork or transcritical depending on A and ?. However, a primary pitchfork bifurcation is found to create unstable steady solutions, even if it is the first bifurcation. For the aspect ratios we studied, and close to the onset of convection, the stable solutions are mainly one-roll structures that can be destabilized by further interactions with asymmetric solutions created at primary pitchfork bifurcations. For large aspect ratios, additional asymmetric one-roll solutions are created via more complex branch interactions.

  2. Fabrication of whispering gallery mode cavity using crystal growth

    E-print Network

    Kudo, Hiroshi; Kato, Takumi; Yokoo, Atsushi; Tanabe, Takasumi

    2013-01-01

    We developed a new method for fabricating crystalline whispering gallery mode cavities based on laser-heated pedestal growth. We fabricated sapphire cavities and obtained a Q factor of 16000 with a cavity whose diameter was about 240 um. We showed numerically that the cross-sectional shape of the cavity is sensitive to the cavity Q, and we controlled it successfully by changing the growth condition in the molten zone, without significantly degrading the crystal structure.

  3. Diffusion of circular DNA in two-dimensional cavity arrays.

    PubMed

    Nykypanchuk, Dmytro; Hoagland, David A; Strey, Helmut H

    2009-11-01

    Through a two-dimensional cavity array with connecting pores of submolecular size, diffusion of relaxed circular and linear DNA molecules is visualized by fluorescence microscopy. Across the entropic barriers transport regime, associated with spatially heterogeneous confinement of flexible polymers, circular DNA diffuses slower than linear DNA of the same length, a trend indicating that linear DNA preferably moves through connecting pores by the threading of an end rather than the looping of a midsection. PMID:19821478

  4. Modelling grain boundary cavity growth in irradiated nimonic PE16

    NASA Astrophysics Data System (ADS)

    Boothby, R. M.

    1990-05-01

    Experimental evidence for the growth and coalescence of cavities nucleated at grain boundary helium bubbles in Nimonic PE16 is presented. A model for creep constrained cavity growth in this alloy is developed and applied over a range of stresses covering in-reactor applications and post-irradiation test conditions. It is shown that low failure strains are the direct result of cavity nucleation at closely spaced helium bubbles. Both the strain and time to failure decrease as the grain size increases. The high creep strength of PE16 is of benefit in restricting cavity growth rates.

  5. Steady-state creep crack growth by continually nucleating cavities

    NASA Astrophysics Data System (ADS)

    Chung, J. O.; Yu, Jin; Hong, S. H.

    F OR CREEP crack growths by the nucleation and growth of grain boundary cavities, steady-state crack growth rates ( ?) are derived when the cavity nucleation is assumed to be continual and strain controlled. For the crack growth under HRR fields, a is linearly proportional to C? as reported in other models. However, when the crack growth occurs under elastic fields, ?K 1{2 + 3n}/{5} (n > {8}/{3}) for diffusional cavity growth and ? ˜ K n1 (n > 2) for cavity growth by power law creep. Predictions of the model are applied to a Ni-Cr steel and a Nimonic 80A, and compared with other models through analyses on the dependence of a on macroscopic load parameters and the activation energy of a.

  6. CAVITY GROWTH MECHANISMS IN UCG WITH SIDE WALL BURN GASIFICATION

    Microsoft Academic Search

    Sidney Schwartz; Thomas Eddy; Kirti Mehta; Steven Lutz; Mahmoud Binaie-Kondolojy

    1978-01-01

    A preliminary 2-dimensional model for in situ underground coal gasification is presented for discussion. The model describes cavity formation from the injection well end and link zone burn up, where the initial link zone geometry is assumed at this time. Cavity growth is predicted via an integral boundary layer analysis with boundary conditions determined by oxygen mass transfer to the

  7. Diffusion, Viscosity and Crystal Growth in Microgravity

    NASA Technical Reports Server (NTRS)

    Myerson, Allan S.

    1996-01-01

    The diffusivity of TriGlycine Sulfate (TGS), Potassium Dihydrogen Phosphate (KDP), Ammonium Dihydrogen Phosphate (ADF) and other compounds of interest to microgravity crystal growth, in supersaturated solutions as a function of solution concentration, 'age' and 'history was studied experimentally. The factors that affect the growth of crystals from water solutions in microgravity have been examined. Three non-linear optical materials have been studied, potassium dihydrogen phosphate (KDP), ammonium dihydrogen phosphate (ADP) and triglycine sulfate (TGC). The diffusion coefficient and viscosity of supersaturated water solutions were measured. Also theoretical model of diffusivity and viscosity in a metastable state, model of crystal growth from solution including non-linear time dependent diffusivity and viscosity effect and computer simulation of the crystal growth process which allows simulation of the microgravity crystal growth were developed.

  8. Effect of underwater local cavity welding method conditions on diffusible hydrogen content in deposited metal

    Microsoft Academic Search

    Dariusz Fydrych; Grzegorz Rogalski

    2011-01-01

    One of the methods with great potential for applications in underwater repairs is local cavity welding. In local cavity method, cooling conditions and diffusible hydrogen amount in weld metal are nearly the same as those existed during welding in the air. This paper presents the results of literature survey and preliminary tests of the effect of local cavity welding conditions

  9. Diffuse interface model of diffusion-limited crystal growth

    Microsoft Academic Search

    Joseph B. Collins; Herbert Levine

    1985-01-01

    A general approach to diffusion-limited crystal growth is proposed. It consists of a modified (nonequilibrium) Cahn-Hilliard representation of the interface coupled to a diffusion equation. Arguments are given as to its superiority over previous models. These are illlustrated in a one-dimensional solution which shows how the system selects a unique interface velocity. The selection can be interpreted as the requirement

  10. Study of small-scale cavity growth mechanisms for UCG

    Microsoft Academic Search

    D. L. Yeary; J. B. Riggs

    1987-01-01

    An experimental study has been conducted to evaluate previously proposed small-scale cavity growth mechanisms in Underground Coal Gasification (UCG). Quarried blocks of lignite from Rockdale, Texas, and subbituminous coal from Hanna, Wyoming, were exposed to high-temperature gases in a refractory chamber in order to access their behavior under UCG conditions. Effects of gas temperature, gas composition, and gas flow rate

  11. Interfacial growth in driven diffusive systems

    Microsoft Academic Search

    A. Hernández-Machado; Hong Guo; J. L. Mozos; David Jasnow

    1989-01-01

    We have studied the growth of interfaces in driven diffusive systems well below the critical temperature by means of Monte Carlo simulations. We consider the region beyond the linear regime and of large values of the external field which has not been explored before. The simulations support the existence of interfacial traveling waves when asymmetry is introduced in the model,

  12. Simple, accurate, and precise measurements of thermal diffusivity in liquids using a thermal-wave cavity

    E-print Network

    Mandelis, Andreas

    -wave phase and cavity length. Measurement precision is directly related to the corresponding precision to the precision with which the relevant cavity lengths can be measured. The methodology was appliedSimple, accurate, and precise measurements of thermal diffusivity in liquids using a thermal

  13. Thermal-wave resonator cavity design and measurements of the thermal diffusivity of liquids

    E-print Network

    Mandelis, Andreas

    Thermal-wave resonator cavity design and measurements of the thermal diffusivity of liquids J. A 2000 A liquid-ambient-compatible thermal wave resonant cavity TWRC has been constructed-significant-figure precision as follows: (0.1445 0.0002) 10 2 cm2 /s distilled water ; (0.0922 0.0002) 10 2 cm2 /s glycerol

  14. CFD Based Design Optimizations of the Diffuser of a Gas Dynamically Driven Laser Cavity

    Microsoft Academic Search

    S. D. Ravi; M. A. Sriram; N. K. S. Rajan; P. S. Kulkarni

    Based on the an earlier CFD analysis of the performance of the gas-dynamically controlled laser cavity (1) it was found that there is possibility of optimizing the geometry of the diffuser that can bring about reductions in both size and cost of the system by examining the critical dimensional requirements of the diffuser. Consequently, an extensive CFD analysis has been

  15. Study of small-scale cavity growth mechanisms for UCG

    SciTech Connect

    Yeary, D.L.; Riggs, J.B.

    1987-01-01

    An experimental study has been conducted to evaluate previously proposed small-scale cavity growth mechanisms in Underground Coal Gasification (UCG). Quarried blocks of lignite from Rockdale, Texas, and subbituminous coal from Hanna, Wyoming, were exposed to high-temperature gases in a refractory chamber in order to access their behavior under UCG conditions. Effects of gas temperature, gas composition, and gas flow rate on the surface recession rates were studied for coal samples using the bedding plan orientation of the side wall of the cavity. The effect of gas temperature on the surface recession rate with cavity roof bedding plane orientation was also studied. For the side wall tests, structural failure of the char or ash was not observed. In addition, the surface recession rate was round to increase significantly with gas temperature and gas flow rate. These results indicate that the surface recession process was heat transfer controlled gasification. For the tests conducted using the bedding plane orientation of the cavity roof, it was found that significant structural failure of the lignite resulted while no structural failure of the subbituminous coal was observed. As a result, the surface recession rate for lignite was three times that for subbituminous coal at 1300/sup 0/K. It is theorized that the structural failure of the lignite is caused by clay stringers present in the lignite.

  16. Diffuse reflecting material for integrating cavity spectroscopy, including ring-down spectroscopy.

    PubMed

    Cone, Michael T; Musser, Joseph A; Figueroa, Eleonora; Mason, John D; Fry, Edward S

    2015-01-10

    We report the development of a diffuse reflecting material with measured reflectivity values as high as 0.99919 at 532 nm and 0.99686 at 266 nm. This material is a high-purity fumed silica, or quartz powder, with particle sizes on the order of 40 nm. We demonstrate that this material can be used to produce surfaces with nearly Lambertian behavior, which in turn can be used to form the inner walls of high-reflectivity integrating cavities. Light reflecting off such a surface penetrates into the material. This means there will be an effective "wall time" for each reflection off the walls in an integrating cavity. We measure this wall time and show that it can be on the order of several picoseconds. Finally, we introduce a technique for absorption spectroscopy in an integrating cavity based on cavity ring-down spectroscopy. We call this technique integrating cavity ring-down spectroscopy. PMID:25967634

  17. Thermal-wave resonant-cavity measurements of the thermal diffusivity of air: A comparison between cavity-length and modulation-frequency scans

    Microsoft Academic Search

    J. Shen; A. Mandelis; B. D. Aloysius

    1996-01-01

    The application of a thermal-wave resonant cavity to thermal-diffusivity measurements of gases has been investigated. The cavity was constructed using a thin aluminum foil wall as the intensitv-modulated laser-beam oscillator source opposite a pyroclectric polyvilidene fluoride wall acting as a signal transducer. Theoretically, cavity-length and modulation-frequency scans both produce resonance-like extrema in lock-in in-phase and quadrature curses. These extrema can

  18. ORIGINAL PAPER Diffusion-controlled spherulite growth in obsidian inferred

    E-print Network

    Martin, Michael C.

    crystals that occur naturally in rhyolitic obsidian. The growth of spherulites requires diffusion and uptake of crystal forming components from the host rhyolite melt or glass, and rejection of non these profiles to models of water diffusion in rhyolite to estimate timescales for spherulite growth. Using

  19. Diffusion processes in Al2O3 scales - Void growth, grain growth, and scale growth

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Gibala, R.

    1983-01-01

    The internal microstructure and growth kinetics of Al2O3 scales on Ni-15Cr-13Al (wt percent) are investigated by TEM and analyzed in relation to models of diffusivity. Polished arc-melted specimens were oxidized in 1-atm air at 1100 C for 0.1, 1.0, and 20 hours and ion-thinned for TEM at 100 kV. The frequency distribution of void size and grain size is determined for different oxidation times and scale depths. The kinetics of microvoid growth and of grain and scale growth are plotted and related via simplified models to lattice and grain-boundary oxygen diffusivity, respectively. Good agreement is found between model predictions and data obtained by Oishi and Kingery (1960) on oxygen diffusion in bulk Al2O3. The further implications and limitations of these findings are discssed.

  20. Experimental estimate of the diffusivity of Vascular Endothelial Growth Factor

    E-print Network

    Núñez, Daniel A

    2006-01-01

    The diffusivity of Vascular Endothelial Growth Factor (VEGF) is a number that is very important in determining the transport of VEGF. The transport of VEGF determines crucial processes such as angiogenesis and vasculogenesis. ...

  1. Multinational enterprises, technology diffusion, and host country productivity growth

    Microsoft Academic Search

    Bin Xu

    2000-01-01

    This paper investigates US multinational enterprises (MNEs) as a channel of international technology diffusion in 40 countries from 1966 to 1994. We use data on technology transfer to distinguish between the technology diffusion effect and other productivity-enhancing effects of MNEs. We find that the technology transfer provided by US MNEs contributes to the productivity growth in DCs but not in

  2. Multinational Enterprises, Technology Diffusion, and Host Country Productivity Growth

    Microsoft Academic Search

    Bin Xu

    1999-01-01

    This paper investigates US multinational enterprises MNEs as a channel of interna- tional technology diffusion in 40 countries from 1966 to 1994. We use data on technology transfer to distinguish between the technology diffusion effect and other productivity-en- hancing effects of MNEs. We find that the technology transfer provided by US MNEs contributes to the productivity growth in DCs but

  3. On The Anomalous Fast Ion Energy Diffusion in Toroidal Plasmas Due to Cavity Modes

    SciTech Connect

    N.N. Gorelenkov, N.J. Fisch and E. Fredrickson

    2010-03-09

    An enormous wave-particle diffusion coefficient along paths suitable for alpha channeling had been deduced in mode converted ion Bernstein wave experiments on Tokamak Fusion Test Reactor (TFTR) the only plausible explanation advanced for such a large diffusion coefficient was the excitation of internal cavity modes which induce particle diffusion along identical diffusion paths, but at much higher rates. Although such a mode was conjectured, it was never observed. However, recent detailed observations of high frequency compressional Alfven eigenmodes (CAEs) on the National Spherical torus Experiment (NSTX) indirectly support the existence of the related conjectured modes on TFTR. The eigenmodes responsible for the high frequency magnetic activity can be identified as CAEs through the polarization of the observed magnetic field oscillations in NSTX and through a comparison with the theoretically derived freuency dispersion relation. Here, we show how these recent observations of high frequency CAEs lend support to this explanation of the long-standing puzzle of anomalous fast ion energy diffusion on TFTR. The support of the conjecure that these internal modes could have caused the remarkable ion energy diffusion on TFTR carries significant and favorable implications for the possibilities in achieving the alpha channeling effect with small injected power in a tokamak reactor.

  4. Motion of an atom in a weakly driven fiber-Bragg-grating cavity: Force, friction, and diffusion

    SciTech Connect

    Le Kien, Fam; Hakuta, K. [Center for Photonic Innovations and Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan)

    2010-06-15

    We study the translational motion of an atom in the vicinity of a weakly driven nanofiber with two fiber-Bragg-grating mirrors. We calculate numerically and analytically the force, the friction coefficients, and the momentum diffusion. We find that the spatial dependences of the force, the friction coefficients, and the momentum diffusion are very complicated due to the evanescent-wave nature of the atom-field coupling as well as the effect of the van der Waals potential. We show that the time development of the mean number of photons in the cavity closely follows the translational motion of the atom through the nodes and antinodes of the fiber-guided cavity standing-wave field even though the cavity finesse is moderate, the cavity is long, and the probe field is weak.

  5. Growth of droplets on a substrate by diffusion and coalescence

    NASA Astrophysics Data System (ADS)

    Steyer, A.; Guenoun, P.; Beysens, D.; Knobler, C. M.

    1991-12-01

    An analytical and numerical study of the early stages condensation of three-dimensional (3D) droplets onto a partially wetting 2D substrate is presented. We show that when surface coverage is low, a mechanism involving Brownian diffusion of the droplets, leading to interaction through coalescences, can explain a number of experimental features (e.g., in breath-figure experiments). First, a motionless drop that incorporates diffusing droplets can asymptotically grow as t1/3. In the second situation, we consider a constant flux of monomers diffusing on the substrate. These monomers coalesce and form bigger drops with mass conservation. These drops diffuse in turn with a lower diffusion coefficient. A numerical simulation of this process shows a rapid formation of a well-defined, monodisperse family of droplets. A scaling analysis of the simulation is able to predict a number of growth exponents. These laws are finally compared with recent experiments and their relevance is discussed.

  6. Neuronal growth as diffusion in an effective potential

    NASA Astrophysics Data System (ADS)

    Rizzo, Daniel J.; White, James D.; Spedden, Elise; Wiens, Matthew R.; Kaplan, David L.; Atherton, Timothy J.; Staii, Cristian

    2013-10-01

    Current understanding of neuronal growth is mostly qualitative, as the staggering number of physical and chemical guidance cues involved prohibit a fully quantitative description of axonal dynamics. We report on a general approach that describes axonal growth in vitro, on poly-D-lysine-coated glass substrates, as diffusion in an effective external potential, representing the collective contribution of all causal influences on the growth cone. We use this approach to obtain effective growth rules that reveal an emergent regulatory mechanism for axonal pathfinding on these substrates.

  7. Development of Nb{sub 3}Sn Cavity Vapor Diffusion Deposition System

    SciTech Connect

    Eremeev, Grigory V.; Macha, Kurt M.; Clemens, William A.; Park, HyeKyoung; Williams, R. Scott

    2014-02-01

    Nb{sub 3}Sn is a BCS superconductors with the superconducting critical temperature higher than that of niobium, so theoretically it surpasses the limitations of niobium in RF fields. The feasibility of technology has been demonstrated at 1.5 GHz with Nb{sub 3}Sn vapor deposition technique at Wuppertal University. The benefit at these frequencies is more pronounced at 4.2 K, where Nb{sub 3}Sn coated cavities show RF resistances an order of magnitude lower than that of niobium. At Jefferson Lab we started the development of Nb{sub 3}Sn vapor diffusion deposition system within an R\\&D development program towards compact light sources. Here we present the current progress of the system development.

  8. [Determining the volume of solution necessary for intraoperative disinfection lavage of the abdominal cavity in diffuse suppurative peritonitis].

    PubMed

    Nifant'ev, O E; Popov, A E; Voevodina, T V; Okolelova, E V

    1990-01-01

    The advantages of lavage of the abdominal cavity in diffuse purulent peritonitis by means of a developed device "Geyser" are shown. Changes in the bacterial contamination, toxicity and metabolite contents in the lavage solution and peritoneum depended on a volume of the fluid used. PMID:2338787

  9. Surface Diffusion: The Low Activation Energy Path for Nanotube Growth

    NASA Astrophysics Data System (ADS)

    Hofmann, S.; Csányi, G.; Ferrari, A. C.; Payne, M. C.; Robertson, J.

    2005-07-01

    We present the temperature dependence of the growth rate of carbon nanofibers by plasma-enhanced chemical vapor deposition with Ni, Co, and Fe catalysts. We extrapolate a common low activation energy of 0.23 0.4 eV, much lower than for thermal deposition. The carbon diffusion on the catalyst surface and the stability of the precursor molecules, C2H2 or CH4, are investigated by ab initio plane wave density functional calculations. We find a low activation energy of 0.4 eV for carbon surface diffusion on Ni and Co (111) planes, much lower than for bulk diffusion. The energy barrier for C2H2 and CH4 dissociation is at least 1.3 eV and 0.9 eV, respectively, on Ni(111) planes or step edges. Hence, the rate-limiting step for plasma-enhanced growth is carbon diffusion on the catalyst surface, while an extra barrier is present for thermal growth due to gas decomposition.

  10. Investigation of cavity growth mechanisms for underground coal gasification of western coal

    SciTech Connect

    Park, K.Y.

    1984-01-01

    Numerous UCG field tests have been performed during the past ten years. Due to the high cost of obtaining sweep efficiency data, limited field data on cavity shape in the coal seam have been obtained. Because of the importance of resource recovery on the economic viability of the UCG process, laboratory studies on cavity growth have been undertaken for Texas lignite, a coal which has also been tested in the field. The laboratory-scale tests show that for Texas-lignite the cavity and affected region were elongated in the direction perpendicular to the bedding plane. This behavior is similar to that exhibited by some sub-bituminous coal, as tested at Lawrence Livermore Laboratory.

  11. Cobalt self-diffusion during cobalt silicide growth

    NASA Astrophysics Data System (ADS)

    Diale, M.; Challens, C.; Zingu, E. C.

    1993-03-01

    The flux of atoms during Si/Co interdiffusion has been investigated by means of thin tantalum marker layers imbedded in the deposited Co layer. The silicide phase CoSi is found to grow in the Si/CoSi/Co structure without any conversion of CoSi to Co2Si. Cobalt is found to be the dominant diffusing species in CoSi during its growth in Si/CoSi/Co structures. Cobalt atoms are also found to diffuse in the unreacted Co layer from the Co surface towards the CoSi/Co interface. These results present evidence that some of the Co vacancies in the metal silicide layer are annihilated at the Co surface.

  12. Random ballistic growth and diffusion in symmetric spaces

    NASA Astrophysics Data System (ADS)

    Gorsky, A.; Nechaev, S.; Santachiara, R.; Schehr, G.

    2012-09-01

    Sequential ballistic deposition (BD) with next-nearest-neighbor (NNN) interactions in a N-column box is viewed as a time-ordered product of (N×N)-matrices consisting of a single sl2-block which has a random position along the diagonal. We relate the uniform BD growth with the diffusion in the symmetric space HN=SL(N,R)/SO(N). In particular, the distribution of the maximal height of a growing heap is connected with the distribution of the maximal distance for the diffusion process in HN. The coordinates of HN are interpreted as the coordinates of particles of the one-dimensional Toda chain. The group-theoretic structure of the system and links to some random matrix models are also discussed.

  13. Random ballistic growth and diffusion in symmetric spaces

    E-print Network

    A. Gorsky; S. Nechaev; R. Santachiara; G. Schehr

    2012-04-27

    Sequential ballistic deposition (BD) with next-nearest-neighbor (NNN) interactions in a N-column box is viewed a time-ordered product of N\\times N-matrices consisting of a single sl_2-block which has a random position along the diagonal. We relate the uniform BD growth with the diffusion in the symmetric space H_N=SL(N,R)/SO(N). In particular, the distribution of the maximal height of a growing heap is connected with the distribution of the maximal distance for the diffusion process in H_N. The coordinates of H_N are interpreted as the coordinates of particles of the one--dimensional Toda chain. The group-theoretic structure of the system and links to some random matrix models are also discussed.

  14. Further development of an axisymmetric global UCG (underground coal gasification) cavity growth simulator

    SciTech Connect

    Britten, J.A.; Thorsness, C.B.

    1987-07-15

    Development has continued on the global underground coal gasification (UCG) cavity simulation model CAVSMII, first described at the 12th UCG symposium, with the result that it now treats essentially all major processes that occur during a UCG operation. To a large extent these modifications were motivated by insight into UCG cavity growth gained from observation of the excavated Partial Seam CRIP (PSC) UCG site. A submodel for water influx has been formulated and added, based on gravity drainage and water reflux, including compressibility effects of the medium. A submodel empirically describing the growth of an outflow channel from a horizontal uncased production borehole in the coal seam has been developed as well. The settling of solids in the rubble pile caused by removal of carbon from spalled char has been reformulated more realistically. Another major modeling reformulation is the addition of a resistance to gas flow through the overburden rubble, which was previously assumed negligible in comparison to the ash pile flow resistance. Also, the submodel describing dynamics of the reaction zone between the ash rubble and the competent coal wall, which previously consisted of an empirical two-parameter model, is now fully integrated into the global cavity evolution model and solved for each time step. At the same time, more efficient algorithms for computing flow of injection gas through the rubble pile have reduced both total CPU time and code memory requirements by more than a factor of two. The present state of the simulator is presented and the effect of some key physical and process parameters is explored. Finally, results are presented for the simulation of UCG cavity growth for the PSC test, the upcoming Rocky Mountain I test and a test of a high-ash, relatively thin seam coal proposed for Brazil. 13 refs.

  15. A model for cavity growth and resource recovery during underground coal gasification

    SciTech Connect

    Britten, J.A.; Thorsness, C.B. (Lawrence Livermore National Lab., CA (USA))

    1989-01-01

    A model describing cavity growth and gas production during underground coal gasification (UCG) has been developed. It is applicable to UCG of shrinking coals in which oxidant injection is maintained at a fixed point low in the coal seam. It is based on a few fundamental assumptions; namely that the cavity is axisymmetric about the injection point, all resistance to injected gas flow is through ash and overburden rubble that accumulates on the cavity floor, thermal radiation dominates in the well-mixed void space, and the coal and overburden spall or rubblize on a small scale du to parameterized thermal effects. The model calculates water influx from the coal aquifer, flow dispersion trough the rubble piles, radiant and convective heat transfer, gas/solid, gas-phase and simple pyrolysis reactions to calculate, through mass and energy balances, recession rates of cavity surfaces and generation rates of major product species. Model predictions are shown to compare very well with process and geometrical data from two UCG field tests, and the model is used to simulate UCG Of other coals of UCG interest.

  16. Pyroelectric Thermal-Wave Resonant Cavity: A Precision Thermal Diffusivity Sensor for Gases and Vapors

    Microsoft Academic Search

    J. Shen; A. Mandelis; T. Ashe

    1998-01-01

    A novel thermal-wave resonant cavity (TWRC) was constructed and used for thermophysical measurements of gases and vapors, with an AC current-heated thin-film resistive element acting as a thermal-wave source. A thin-film pyroelectric element was used both as a cavity wall and as a signal transducer. A theoretical model of the cavity length-scanned thermal-wave field was developed to quantify the standing-wave

  17. Formal asymptotic limit of a diffuse-interface tumor-growth

    E-print Network

    Paris-Sud XI, Université de

    Formal asymptotic limit of a diffuse-interface tumor-growth model Danielle Hilhorst , Johannes-interface tumor-growth model, which has the form of a phase-field system. We discuss the singular limit perturbation, interface mo- tion, matched asymptotic expansion, tumor-growth model. 1 Introduction Diffuse

  18. Evidence of preferential diffusion of impurities along grain boundaries in very pure niobium used for radio frequency cavities

    SciTech Connect

    Antoine, C.; Bonin, B.; Safa, H. [CEA, DSM/DAPNIA/Service d`Etude des Accelerateurs, CE-Saclay, 91191 Gif-sur-Yvette Cedex (France)] [CEA, DSM/DAPNIA/Service d`Etude des Accelerateurs, CE-Saclay, 91191 Gif-sur-Yvette Cedex (France); Berthier, B.; Tessier, C.; Tocellier, P. [CEA, DSM/DRECAM/Laboratoire Pierre Sue, CE-Saclay, 91191 Gif-sur-Yvette Cedex (France)] [CEA, DSM/DRECAM/Laboratoire Pierre Sue, CE-Saclay, 91191 Gif-sur-Yvette Cedex (France); Chevarier, A.; Chevarier, N.; Roux, B. [Institut de Physique Nucleaire de Lyon, IN2P3-CNRS et Universite Claude Bernard, 43, Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex (France)] [Institut de Physique Nucleaire de Lyon, IN2P3-CNRS et Universite Claude Bernard, 43, Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex (France)

    1997-02-01

    In order to overcome dissipation due to impurity segregation at grain boundaries, niobium cavities are submitted to a purification annealing (1300{degree}C{plus_minus}200{degree}C under vacuum) during which titanium is evaporated onto the Nb surface. The resulting titanium layer acts as a solid state getter reacting with light impurities (H, C, N, O), thereby removing these impurities from the bulk of the niobium. Preferential titanium diffusion along grain boundaries have been studied using proton-induced x-ray emission. {copyright} {ital 1997 American Institute of Physics.}

  19. Diffusion-controlled spherulite growth in obsidian inferred from H2O concentration profiles

    SciTech Connect

    Watkins, Jim; Watkins, Jim; Manga, Michael; Huber, Christian; Martin, Michael C.

    2007-11-02

    Spherulites are spherical clusters of radiating crystals that occur naturally in rhyolitic obsidian. The growth of spherulites requires diffusion and uptake of crystal forming components from the host rhyolite melt or glass, and rejection of non-crystal forming components from the crystallizing region. Water concentration profiles measured by synchrotron-source Fourier transform spectroscopy reveal that water is expelled into the surrounding matrix during spherulite growth, and that it diffuses outward ahead of the advancing crystalline front. We compare these profiles to models of water diffusion in rhyolite to estimate timescales for spherulite growth. Using a diffusion-controlled growth law, we find that spherulites can grow on the order of days to months at temperatures above the glass transition. The diffusion-controlled growth law also accounts for spherulite size distribution, spherulite growth below the glass transition, and why spherulitic glasses are not completely devitrified.

  20. A New Diffuse Reflecting Material with Applications Including Integrating Cavity Ring-Down Spectroscopy 

    E-print Network

    Cone, Michael Thomas

    2014-04-16

    We report the development of a new diffuse reflecting material with measured diffuse reflectivity values as high as 0.9992 at 532 nm, and 0.9969 at 266 nm. These values are, to the author’s best knowledge, the highest diffuse reflectivity values...

  1. Ice crystal growth in a dynamic thermal diffusion chamber

    NASA Technical Reports Server (NTRS)

    Keller, V. W.

    1980-01-01

    Ice crystals were grown in a supersaturated environment produced by a dynamic thermal diffusion chamber, which employed two horizontal plates separated by a distance of 2.5 cm. Air was circulated between and along the 1.2 m length of the plates past ice crystals which nucleated and grew from a fiber suspended vertically between the two plates. A zoom stereo microscope with a magnification which ranged from 3X to 80X and both 35 mm still photographs and 16 mm time lapse cine films taken through the microscope were used to study the variation of the shape and linear growth rate of ice crystals as a function of the ambient temperature, the ambient supersaturation, and the forced ventilation velocity. The ambient growth conditions were varied over the range of temperature 0 to -40 C, over the range of supersaturation 4% to 50% with respect to ice, and over the range of forced ventilation velocities 0 cm/s to 20 cm/s.

  2. O(minus 2) grain boundary diffusion and grain growth in pure dense MgO

    NASA Technical Reports Server (NTRS)

    Kapadia, C. M.; Leipold, M. H.

    1973-01-01

    Grain growth behavior in fully dense compacts of MgO of very high purity was studied, and the results compared with other similar behaving materials. The activation energy for the intrinsic self-diffusion of Mg(2minus) is discussed along with the grain boundary diffusion of O(2minus). Grain boundary diffusion of O(2minus) is proposed as the controlling mechanism for grain growth.

  3. Resource recovery and cavity growth during the Rocky Mountain 1 field test

    SciTech Connect

    Cena, R.J.; Britten, J.A.; Thorsness, C.B.

    1988-08-01

    Resource recovery and cavity growth remain important issues affecting performance, scale-up and overall process efficiency for underground coal gasification (UCG). Results from the recently completed dual-module Rocky Mountain I (RM I) UCG experiment give us firsthand information concerning these important parameters. During the RM I test, two gasifiers, the Controlled Retracting Injection Point (CRIP) and the Extended Linked Well (ELW) modules, were operated simultaneously. These modules differed in well completion geometry and to a lesser extent in operating strategy. Using material balance, thermowell and tracer gas information, cavity development, gas production rates and yields, and general features of the two modules are discussed and compared. Also, the linking phase of the test is described, and effects of process parameter changes on system performance are discussed. The major conclusion obtained from data analysis is the importance of maintaining oxidant injection low in the coal seam at all times. Performance of the CRIP gasifier, for which the above condition was met, is shown to compare very favorably with performance of surface gasifiers. 10 refs., 15 figs., 3 tabs.

  4. Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth

    Microsoft Academic Search

    Guus Rijnders; Dave H. A. Blank; Junghoon Choi; Chang-Beom Eom

    2004-01-01

    During the initial growth of the ferromagnetic oxide SrRuO3 on TiO2-terminated SrTiO3, we observe a self-organized conversion of the terminating atomic layer from RuO2 to SrO. This conversion induces an abrupt change in growth mode from layer by layer to growth by step advancement, indicating a large enhancement of the surface diffusivity. This growth mode enables the growth of single-crystalline

  5. Interferometric measurements of a dendritic growth front solutal diffusion layer

    NASA Technical Reports Server (NTRS)

    Hopkins, John A.; Mccay, T. D.; Mccay, Mary H.

    1991-01-01

    An experimental study was undertaken to measure solutal distributions in the diffusion layer produced during the vertical directional solidification (VDS) of an ammonium chloride - water (NH4Cl-H2O) solution. Interferometry was used to obtain concentration measurements in the 1-2 millimeter region defining the diffusion layer. These measurements were fitted to an exponential form to extract the characteristic diffusion parameter for various times after the start of solidification. The diffusion parameters are within the limits predicted by steady state theory and suggest that the effective solutal diffusivity is increasing as solidification progresses.

  6. Journal of Crystal Growth 232 (2001) 273284 Precision measurement of ternary diffusion coefficients and

    E-print Network

    Annunziata, Onofrio

    2001-01-01

    Journal of Crystal Growth 232 (2001) 273­284 Precision measurement of ternary diffusion coefficients and implications for protein crystal growth: lysozyme chloride in aqueous ammonium chloride at 258 the driving force for nucleation and crystal growth of lysozyme chloride. # 2001 Elsevier Science B.V. All

  7. Large interface diffusion in endotaxial growth of MnP films on GaP substrates

    SciTech Connect

    Nateghi, N., E-mail: seyyed-nima.nateghi@polymtl.ca; Ménard, D.; Masut, R. A. [Regroupement québécoise sur les matériaux de pointe (RQMP), Département de Génie Physique, Polytechnique Montréal, C.P. 6079, succ. Centre-ville, Montréal, Québec H3C 3A7 (Canada)

    2014-10-07

    The metal organic vapor deposition of MnP films on GaP (100) substrates is shown to have a substantial endotaxial component. A study of the growth time evolution of the endotaxial depths of MnP grains reveals a diffusion-controlled growth with a relatively large diffusion coefficient of Mn in GaP. The value (2.2 ± 1.5) × 10?¹? (cm²/s) obtained at 650 °C is at least two orders of magnitude larger than the reported Mn diffusion in bulk GaP. GaP surface mounds provide further indirect evidence that this large diffusion coefficient is concurrent with the out-diffusion of Ga atoms at the growing MnP/GaP interface. No trace of dislocations could be observed at or near this interface, which strongly suggests that Mn diffusion occurs through vacant sites generated by the difference between the crystallographic structures of MnP and GaP.

  8. Molecular dynamics simulations of surface diffusion and growth on silver and gold clusters

    Microsoft Academic Search

    F. Baletto; C. Mottet; R. Ferrando

    2000-01-01

    We report a systematic study of the diffusion of single adatoms and of the growth of fcc silver and gold clusters (Wulff polyhedra) by molecular dynamics simulations. Both metals have been modelled by many-body tight-binding potentials. The energy barriers for adatom diffusion on the cluster facets are calculated by the nudged elastic band method. Concerning single-adatom diffusion, we have studied

  9. Technology Diffusion, Services, and Endogenous Growth in EuropeIs the Lisbon Strategy Useful?

    Microsoft Academic Search

    Paolo Guerrieri; Bernardo Maggi; Valentina Meliciani; Pier Carlo Padoan

    2005-01-01

    We explore the role of business services in knowledge accumulation and growth and the determinants of knowledge diffusion including the role of distance. A continuous-time model is estimated on several European countries, Japan, and the United States. Policy simulations illustrate the benefits for EU growth of the deepening of the single market, the reduction of regulatory barriers, and the accumulation

  10. A Nonlinear Master Equation for a Degenerate Diffusion Model of Biofilm Growth

    E-print Network

    Hillen, Thomas

    A Nonlinear Master Equation for a Degenerate Diffusion Model of Biofilm Growth Hassan Khassehkhan1@math.ualberta.ca Abstract. We present a continuous time/discrete space model of biofilm growth, starting from the semi models of biofilms. Grid refinement leads formally to a degenerate parabolic equation. We show that a set

  11. From Brownian motion with a local time drift to Feller's branching diffusion with logistic growth

    E-print Network

    Wakolbinger, Anton

    ) of the population that is alive at the time corresponding to this height. This mass is Zt, the state intensity ) that counteract the supercritical growth of the population. This population model and itsFrom Brownian motion with a local time drift to Feller's branching diffusion with logistic growth

  12. Thermal diffusivity measurements in liquids using signal common-mode-rejection demodulation in a thermal-wave cavity

    E-print Network

    Mandelis, Andreas

    measurements in liquids using a thermal-wave cavity. This methodology combines the precision of the thermal in a thermal-wave cavity J. A. Balderas-Lo´peza) and Andreas Mandelis Photothermal and Optoelectronic-wave cavity scan and the flexibility of modulation-frequency scan modes, along with baseline suppression

  13. Growth by rectified diffusion of strongly acoustically forced gas bubbles in nearly saturated liquids

    Microsoft Academic Search

    Olivier Louisnard; Francisco Gomez

    2003-01-01

    The growth or dissolution of small gas bubbles (R0<15 mum) by rectified diffusion in nearly saturated liquids, subject to low frequencies (20 kHzdiffusion threshold radius merges with the Blake threshold radius, which means that a growing bubble is

  14. Diffusive transport enhancement by isolated resonances and distribution tails growth in hadronic beams

    SciTech Connect

    Gerasimov, A.

    1990-12-06

    The escape rates and evolution of a distribution of particles are considered for a 2-D model of transverse motion of particles in hadronic storage rings, when nonlinear resonances and external diffusion are present. Dynamic enhancement of diffusion inside separatrices can develop under a certain geometry of resonance oscillations and relatively wide resonances, leading to the fast growth of distribution tails and escape rates. The phenomenon is absent in 1-D. 10 refs., 4 figs.

  15. High-Precision and High-Resolution Measurements of Thermal Diffusivity and Infrared Emissivity of Water–Methanol Mixtures Using a Pyroelectric Thermal Wave Resonator Cavity: Frequency-Scan Approach

    Microsoft Academic Search

    A. Matvienko; A. Mandelis

    2005-01-01

    The thermal diffusivity and effective infrared emissivity of water–methanol mixtureswere measured at atmospheric pressure and ambient temperature using a pyroelectric thermal-wave resonator cavity. The applied frequency-scan method allows keeping the cavity length fixed, which eliminates instrumental errors and substantially improves the precision and accuracy of the measurements. A theoretical model describing conduction and radiation heat transfer in the cavity was

  16. Strong Surface Diffusion Mediated Glancing-Angle Deposition: Growth, Recrystallization and Reorientation of Tin Nanorods

    NASA Astrophysics Data System (ADS)

    Wang, Huan-Hua; Shi, Yi-Jian; William, Chu; Yigal, Blum

    2008-01-01

    Different from usual glancing-angle deposition where low surface diffusion is necessary to form nanorods, strong surface diffusion mediated glancing-angle deposition is exemplified by growing tin nanorod films on both silicon and glass substrates simultaneously via thermal evaporation. During growth, the nanorods were simultaneously baked by the high-temperature evaporator, and therefore re-crystallized into single crystals in consequence of strong surface diffusion. The monocrystalline tin nanorods have a preferred orientation perpendicular to the substrate surface, which is quite different from the usual uniformly oblique nanorods without recrystallization.

  17. Morphological evidence for diffusion-controlled growth of garnet from metapelites

    NASA Astrophysics Data System (ADS)

    Gulbin, Yu. L.; Glazov, A. I.

    2013-12-01

    The surface microtopography of garnet from metamorphic schists of the northern Ladoga region has been investigated. The morphology of garnet is distinguished by a rough stepped surface on dodecahedral faces {110} and by the absence of sharp crystal edges. As follows from experimental results on crystal growth under hydrothermal conditions, the microtopography pattern gives evidence for a highly oversaturated inter-granular medium and the important role of diffusion as a factor controlling garnet growth.

  18. A comparison of boron and phosphorus diffusion and dislocation loop growth from silicon implants into silicon

    E-print Network

    Florida, University of

    A comparison of boron and phosphorus diffusion and dislocation loop growth from silicon implants performed an experiment using boron, phosphorus, and dislocation markers to compare TED effects. This experiment shows that phosphorus is enhanced significantly more than boron during damage annealing

  19. Realistic Simulation of the 3D Growth of Brain Tumors in MR Images Coupling Diffusion with

    E-print Network

    Ayache, Nicholas

    1 Realistic Simulation of the 3D Growth of Brain Tumors in MR Images Coupling Diffusion Centre Antoine Lacassagne, Nice, France Computational Radiology Laboratory, Brigham and Women's Hospital or the ventricles. These different structures are introduced into the model using an atlas matching technique

  20. Changes in the pattern of horseradish peroxidase diffusion into predentin and dentin after cavity preparation in rat molars

    Microsoft Academic Search

    Toshio Izumi; Hiroshi Inoue; Hiroshi Matsuura; Fumihiko Mukae; Hiromichi Osoegawa; Hirofumi Hirano; Naoharu Tamura

    2001-01-01

    Objective: The purpose of this study was to examine the process of reducing dentin permeability in adult rat molars after cavity preparation with horseradish peroxidase as a tracer. Study Design: Class V cavities were prepared on the upper first molars of 18 rats. Horseradish peroxidase was injected into the vascular system at intervals of 3 hours and 3, 5, 7,

  1. Accelerated kinetics and mechanism of growth of boride layers on titanium under isothermal and cyclic diffusion

    NASA Astrophysics Data System (ADS)

    Sarma, Biplab

    2011-12-01

    The tendency of titanium (Ti) and its alloys to wear, gall and seize during high contact stresses between sliding surfaces severely limits their applications in bearings, gears etc. One way to mitigate these problems is to modify their surfaces by applying hard and wear resistant surface coatings. Boriding, which involves solid state diffusion of boron (B) into Ti, thereby forming hard surface layers consisting of TiB2 and TiB compounds has been shown to produce extremely high wear resistant surfaces in Ti and its alloys. The growth kinetics of these layers are, however, limited by the low diffusivities of B in the high melting TiB2 and TiB compounds. On the basis of the fact that HCP metals such as Ti show enhanced (anomalous) self-diffusion near the phase transition temperature, the first hypothesis of this work has been that the diffusivity enhancement should cause rapid ingress of B atoms, thereby accelerating the growth of the hard boride layers. Isothermal boriding experiments were performed close to phase transition temperature (890, 910, and 915°C) for time periods ranging from 3 to 24 hours. It was found that indeed a much deeper growth of TiB into the Ti substrate (˜75 mum) occurred at temperatures very close to the transition temperature (910°C), compared to that obtained at 1050°C. A diffusion model based on error-function solutions of Fick's second law was developed to quantitatively illustrate the combined effects of the normal B diffusion in the TiB phase and the anomalous B diffusion in Ti phase in accelerating TiB layer growth. Furthermore, isothermal boriding experiments close to transition temperature (900°C) for a period of 71 hours resulted in coating thickness well above 100 mum, while at 1050°C, the layer growth saturated after about 24 hours of treatment time. In the second part of this work, a novel approach named "cyclic-phase-changediffusion, (CPCD)," to create deeper TiB2 and TiB coating layers on CP-Ti by cyclic thermal processing, has been investigated. It was found that thermal cyclic B diffusion in Ti across the alpha(alpha)-beta(beta) phase transition temperature led to highly hardened surface layers enriched with TiB whiskers that grow to depths exceeding 120 mum. By solving the transient heat transport problem for cyclic changes in surface temperatures, it was found that there is a "heat-packet" that travels back and forth from the surface to the interior of the material. This heat-packet appears to transport B dissolved in beta-Ti into interior causing increased coating depths.

  2. Analysis of the diffusion controlled growth of cobalt silicides in bulk and thin film couples

    NASA Astrophysics Data System (ADS)

    Barge, T.; Gas, P.; D'Heurle, F. M.

    1995-05-01

    The solid state reaction between Co and Si has been studied in bulk diffusion couples between 850 and 1100 C. At the scale of the observations made, the three phases Co2Si, CoSi, and CoSi2 are found to grow simultaneously, according to diffusion controlled kinetics. The results are analyzed in term of the Nernst-Einstein equation that directly relates diffusion fluxes to the free energy changes driving the formation. The growth rates obtained for CoSi2 at high temperatures, in the present bulk samples, are compared with those determined by others in thin films, at much lower temperatures. The comparison requires that attention should be paid to two factors. The first one is that the laws of growth are slightly different for a phase growing simultaneously with two other ones (bulk) and one phase growing alone (thin films). The second factor is the grain size of the various samples, which varies with the temperature of reaction. Once this is done, excellent agreement is obtained between the two sets of measurements. Moreover it is shown that knowing the grain size, it is possible to calculate quite accurately the growth rate from the respective isotope diffusion coefficients both for lattice and grain boundaries of Co and Si in CoSi2.

  3. Dynamic scaling for the growth of non-equilibrium fluctuations during thermophoretic diffusion in microgravity

    E-print Network

    Roberto Cerbino; Yifei Sun; Aleksandar Donev; Alberto Vailati

    2015-05-27

    Diffusion processes are widespread in biological and chemical systems, where they play a fundamental role in the exchange of substances at the cellular level and in determining the rate of chemical reactions. Recently, the classical picture that portrays diffusion as random uncorrelated motion of molecules has been revised, when it was shown that giant non-equilibrium fluctuations develop during diffusion processes. Under microgravity conditions and at steady-state, non-equilibrium fluctuations exhibit scale invariance and their size is only limited by the boundaries of the system. In this work, we investigate the onset of non-equilibrium concentration fluctuations induced by thermophoretic diffusion in microgravity, a regime not accessible to analytical calculations but of great relevance for the understanding of several natural and technological processes. A combination of state of the art simulations and experiments allows us to attain a fully quantitative description of the development of fluctuations during transient diffusion in microgravity. Both experiments and simulations show that during the onset the fluctuations exhibit scale invariance at large wave vectors. In a broader range of wave vectors simulations predict a spinodal-like growth of fluctuations, where the amplitude and length-scale of the dominant mode are determined by the thickness of the diffuse layer.

  4. Spectral and angular dependence of mid-infrared diffuse scattering from explosives residues for standoff detection using external cavity quantum cascade lasers

    SciTech Connect

    Suter, Jonathan D.; Bernacki, Bruce E.; Phillips, Mark C.

    2012-09-01

    We present a study of the spectral and angular dependence of scattered mid-infrared light from surfaces coated with explosives residues (TNT, RDX, and tetryl) detected at a 2 meter standoff distance. An external cavity quantum cascade laser provided tunable illumination between 7 and 8 µm. Important differences were identified in the spectral features between specular reflection and diffuse scattering which will impact most practical testing scenarios and complicate material identification. We discuss some of the factors influencing the dependence of observed spectra on the experimental geometry.

  5. Nucleation and growth by diffusion under Ostwald-Freundlich boundary condition

    SciTech Connect

    Iwamatsu, Masao, E-mail: iwamatsu@ph.ns.tcu.ac.jp [Department of Physics, Faculty of Liberal Arts and Sciences, Tokyo City University, Setagaya-ku, Tokyo 158-8557 (Japan)] [Department of Physics, Faculty of Liberal Arts and Sciences, Tokyo City University, Setagaya-ku, Tokyo 158-8557 (Japan)

    2014-02-14

    The critical radius of a nucleus grown by diffusion in a solution is studied thermodynamically as well as kinetically. The thermodynamic growth equation called Zeldovich equation of classical nucleation theory and the kinetic diffusional growth equation combined with the Ostwald-Freundlich boundary condition lead to the same critical radius. However, it should be pointed out that the diffusional equation may lead to a kinetic critical radius that is different from the thermodynamic critical radius, thus indicating the possibility of kinetically controlling the critical radius of a nucleus.

  6. Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth

    E-print Network

    Eom, Chang Beom

    Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth Guus of the ferromagnetic oxide SrRuO3 on TiO2-terminated SrTiO3 , we observe a self-organized conversion of the terminating prerequisites to utilize all opportunities. SrRuO3 has been subject to many studies because of its unique

  7. Growth of intermediate phases in Co\\/Si diffusion couples: Bulk versus thin-film studies

    Microsoft Academic Search

    Chia-Hong Jan; Chia-Ping Chen; Y. Austin Chang

    1993-01-01

    Bulk diffusion couples of Co\\/Si were annealed at 800, 900, 1000, and 1050 °C for times ranging from 24 h to 1 month. The growth rates of the three intermediate phases Co2Si, CoSi, and CoSi2 and the concentration profiles across the couples were determined by optical microscopy and electron probe microanalysis, respectively. Using these data and the data reported in

  8. Physicochemical analysis of compound growth in a diffusion couple with two-phase end-members

    Microsoft Academic Search

    A. Paul; A. A. Kodentsov; F. J. J. van Loo

    2006-01-01

    A general treatment of a diffusion-controlled growth of a stoichiometric intermetallic in reaction between two two-phase alloys is introduced. A reaction couple, in which a layer of Co2Si is formed during interdiffusion from its adjacent saturated phases is used as a model system. On the basis of chemical reaction equations occurring at the interphase interfaces, data on relative mobilities of

  9. Parasite-mediated growth patterns and nutritional constraints in a cavity-nesting bird

    Microsoft Academic Search

    Erin L. O’Brien; Russell D. Dawson

    2008-01-01

    Summary 1. Trade-offs between growth and immunity of nestling birds can be influenced by parasites, but the magnitude of these effects may depend on availability of critical dietary nutrients. Owing to their importance for both immune system function and growth, dietary carotenoids have the potential to mediate parasite-induced developmental strategies of avian hosts. 2. The effects of ectoparasitic blow flies

  10. Extracellular distribution of diffusible growth factors controlled by heparan sulfate proteoglycans during mammalian embryogenesis.

    PubMed

    Matsuo, Isao; Kimura-Yoshida, Chiharu

    2014-12-01

    During mouse embryogenesis, diffusible growth factors, i.e. fibroblast growth factors, Wnt, bone morphogenetic protein and Hedgehog family members, emanating from localized areas can travel through the extracellular space and reach their target cells to specify the cell fate and form tissue architectures in coordination. However, the mechanisms by which these growth factors travel great distances to their target cells and control the signalling activity as morphogens remain an enigma. Recent studies in mice and other model animals have revealed that heparan sulfate proteoglycans (HSPGs) located on the cell surface (e.g. syndecans and glypicans) and in the extracellular matrix (ECM; e.g. perlecan and agrin) play crucial roles in the extracellular distribution of growth factors. Principally, the function of HSPGs depends primarily on the fine features and localization of their heparan sulfate glycosaminoglycan chains. Cell-surface-tethered HSPGs retain growth factors as co-receptors and/or endocytosis mediators, and enzymatic release of HSPGs from the cell membrane allows HSPGs to transport or move multiple growth factors. By contrast, ECM-associated HSPGs function as a reservoir or barrier in a context-dependent manner. This review is focused on our current understanding of the extracellular distribution of multiple growth factors controlled by HSPGs in mammalian development. PMID:25349453

  11. History induced critical scaling in disordered media and super diffusive growth in highly advective random environments

    NASA Astrophysics Data System (ADS)

    Carpenter, John Halsey

    The behavior of non-equilibrium systems in the presence of quenched random disorder is studied. In noisy, hysteretic systems, the role of driving force history is studied in the context of the non-equilibrium, zero-temperature Random Field Ising Model (RFIM). The RFIM was originally developed as a simple model for disordered magnets, but has applications far beyond magnetic systems. Previous work examining history effects in models and experiments are briefly reviewed, followed by a summary of the saturation loop behavior of the RFIM. A numerical scaling analysis of the AC demagnetization curve of the RFIM is performed, examining the effect of the underlying disorder on avalanche size distributions, correlation functions, and spanning avalanches. Furthermore, a similar scaling analysis for nested, concentric, symmetric subloops is performed via an analysis of history-induced disorder. Next the effects of long range demagnetizing fields on the demagnetization curve and subloops are studied. Finally, an analysis of corrections to scaling for subloops is presented, along with a derivation of the exponent relations. Disorder in population biology is studied for the case of a spreading cluster of bacteria in a highly advective environment with inhomogeneous nutrient concentration. A model reaction-diffusion equation with Fisher growth terms is introduced with a brief discussion of previous work on similar equations and experiments. The linear two-dimensional problem is mapped onto a simplified one-dimensional equation. Numerical simulations of concentration profiles reveal anomalous growth and super-diffusive spreading in the direction perpendicular to the convection velocity. A time characterizing the crossover from pure diffusion to this super-diffusive behavior is perturbatively calculated. The crossover time's dependence on the velocity and disorder strength is then tested numerically. Two-dimensional simulations of the full linear reaction-diffusion equation also show the onset of super-diffusive growth in concentration contour maps. On the other hand, with nonlinear growth in two dimensions, a symmetric wave front develops with a propagation velocity greater than the minimum Fisher velocity. An expression is derived and tested for this velocity.

  12. Matrix Models for Size-Structured Populations: Unrealistic Fast Growth or Simply Diffusion?

    PubMed Central

    Picard, Nicolas; Liang, Jingjing

    2014-01-01

    Matrix population models are widely used to study population dynamics but have been criticized because their outputs are sensitive to the dimension of the matrix (or, equivalently, to the class width). This sensitivity is concerning for the population growth rate () because this is an intrinsic characteristic of the population that should not depend on the model specification. It has been suggested that the sensitivity of to matrix dimension was linked to the existence of fast pathways (i.e. the fraction of individuals that systematically move up a class), whose proportion increases when class width increases. We showed that for matrix population models with growth transition only from class to class , was independent of the class width when the mortality and the recruitment rates were constant, irrespective of the growth rate. We also showed that if there were indeed fast pathways, there were also in about the same proportion slow pathways (i.e. the fraction of individuals that systematically remained in the same class), and that they jointly act as a diffusion process (where diffusion here is the movement in size of an individual whose size increments are random according to a normal distribution with mean zero). For 53 tree species from a tropical rain forest in the Central African Republic, the diffusion resulting from common matrix dimensions was much stronger than would be realistic. Yet, the sensitivity of to matrix dimension for a class width in the range 1–10 cm was small, much smaller than the sampling uncertainty on the value of . Moreover, could either increase or decrease when class width increased depending on the species. Overall, even if the class width should be kept small enough to limit diffusion, it had little impact on the estimate of for tree species. PMID:24905941

  13. The Spatio-temporal Evolution of Solar Flares Observed with AIA/SDO: Fractal Diffusion, Sub-diffusion, or Logistic Growth?

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.

    2012-09-01

    We explore the spatio-temporal evolution of solar flares by fitting a radial expansion model r(t) that consists of an exponentially growing acceleration phase, followed by a deceleration phase that is parameterized by the generalized diffusion function r(t)vprop?(t - t 1)?/2, which includes the logistic growth limit (? = 0), sub-diffusion (? = 0-1), classical diffusion (? = 1), super-diffusion (? = 1-2), and the linear expansion limit (? = 2). We analyze all M- and X-class flares observed with Geostationary Operational Environmental Satellite and Atmospheric Imaging Assembly/Solar Dynamics Observatory (SDO) during the first two years of the SDO mission, amounting to 155 events. We find that most flares operate in the sub-diffusive regime (? = 0.53 ± 0.27), which we interpret in terms of anisotropic chain reactions of intermittent magnetic reconnection episodes in a low plasma-? corona. We find a mean propagation speed of v = 15 ± 12 km s-1, with maximum speeds of v max = 80 ± 85 km s-1 per flare, which is substantially slower than the sonic speeds expected for thermal diffusion of flare plasmas. The diffusive characteristics established here (for the first time for solar flares) is consistent with the fractal-diffusive self-organized criticality model, which predicted diffusive transport merely based on cellular automaton simulations.

  14. THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES OBSERVED WITH AIA/SDO: FRACTAL DIFFUSION, SUB-DIFFUSION, OR LOGISTIC GROWTH?

    SciTech Connect

    Aschwanden, Markus J., E-mail: aschwanden@lmsal.com [Lockheed Martin Advanced Technology Center, Solar and Astrophysics Laboratory, Organization ADBS, Building 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

    2012-09-20

    We explore the spatio-temporal evolution of solar flares by fitting a radial expansion model r(t) that consists of an exponentially growing acceleration phase, followed by a deceleration phase that is parameterized by the generalized diffusion function r(t){proportional_to}{kappa}(t - t{sub 1}){sup {beta}/2}, which includes the logistic growth limit ({beta} = 0), sub-diffusion ({beta} = 0-1), classical diffusion ({beta} = 1), super-diffusion ({beta} = 1-2), and the linear expansion limit ({beta} = 2). We analyze all M- and X-class flares observed with Geostationary Operational Environmental Satellite and Atmospheric Imaging Assembly/Solar Dynamics Observatory (SDO) during the first two years of the SDO mission, amounting to 155 events. We find that most flares operate in the sub-diffusive regime ({beta} = 0.53 {+-} 0.27), which we interpret in terms of anisotropic chain reactions of intermittent magnetic reconnection episodes in a low plasma-{beta} corona. We find a mean propagation speed of v = 15 {+-} 12 km s{sup -1}, with maximum speeds of v{sub max} = 80 {+-} 85 km s{sup -1} per flare, which is substantially slower than the sonic speeds expected for thermal diffusion of flare plasmas. The diffusive characteristics established here (for the first time for solar flares) is consistent with the fractal-diffusive self-organized criticality model, which predicted diffusive transport merely based on cellular automaton simulations.

  15. Stability of Densely Branched Growth in Dissipative Diffusion Controlled Systems Juan K. Lin and David G. Grier

    E-print Network

    Grier, David

    Stability of Densely Branched Growth in Dissipative Diffusion Controlled Systems Juan K. Lin emerge when the interface between two phases is driven out of equilibrium by a diffusive field. Highly forming systems. Neither ordered nor fractal, this pattern is characterized by a large number of branches

  16. Modelling the Effect of Fruit Growth on Surface Conductance to Water Vapour Diffusion

    PubMed Central

    GIBERT, CAROLINE; LESCOURRET, FRANÇOISE; GÉNARD, MICHEL; VERCAMBRE, GILLES; PÉREZ PASTOR, ALEJANDRO

    2005-01-01

    • Background and Aims A model of fruit surface conductance to water vapour diffusion driven by fruit growth is proposed. It computes the total fruit conductance by integrating each of its components: stomata, cuticle and cracks. • Methods The stomatal conductance is computed from the stomatal density per fruit and the specific stomatal conductance. The cuticular component is equal to the proportion of cuticle per fruit multiplied by its specific conductance. Cracks are assumed to be generated when pulp expansion rate exceeds cuticle expansion rate. A constant percentage of cracks is assumed to heal each day. The proportion of cracks to total fruit surface area multiplied by the specific crack conductance accounts for the crack component. The model was applied to peach fruit (Prunus persica) and its parameters were estimated from field experiments with various crop load and irrigation regimes. • Key Results The predictions were in good agreement with the experimental measurements and for the different conditions (irrigation and crop load). Total fruit surface conductance decreased during early growth as stomatal density, and hence the contribution of the stomatal conductance, decreased from 80 to 20 % with fruit expansion. Cracks were generated for fruits exhibiting high growth rates during late growth and the crack component could account for up to 60 % of the total conductance during the rapid fruit growth. The cuticular contribution was slightly variable (around 20 %). Sensitivity analysis revealed that simulated conductance was highly affected by stomatal parameters during the early period of growth and by both crack and stomatal parameters during the late period. Large fruit growth rate leads to earlier and greater increase of conductance due to higher crack occurrence. Conversely, low fruit growth rate accounts for a delayed and lower increase of conductance. • Conclusions By predicting crack occurrence during fruit growth, this model could be helpful in managing cropping practices for integrated plant protection. PMID:15655107

  17. Growth of intermediate phases in Co/Si diffusion couples: Bulk versus thin-film studies

    NASA Astrophysics Data System (ADS)

    Jan, Chia-Hong; Chen, Chia-Ping; Chang, Y. Austin

    1993-02-01

    Bulk diffusion couples of Co/Si were annealed at 800, 900, 1000, and 1050 °C for times ranging from 24 h to 1 month. The growth rates of the three intermediate phases Co2Si, CoSi, and CoSi2 and the concentration profiles across the couples were determined by optical microscopy and electron probe microanalysis, respectively. Using these data and the data reported in the literature at lower temperatures, the interdiffusion coefficients of Co2Si, CoSi, and CoSi2 were obtained as a function of temperature. The activation energies obtained were 140, 160, and 190 kJ/mol (or 1.45, 1.66, and 1.97 eV) for Co2Si, CoSi, and CoSi2, respectively. The generally small interdiffusion coefficient of CoSi2 and its high activation energy cause the growth rate of CoSi2 to be extremely small at low temperatures. Using the interdiffusion coefficients of Co2Si, CoSi, and CoSi2 extrapolated to low temperatures, the growth rates of Co2Si, CoSi, and CoSi2 in thin-film Co/Si couples were predicted. The predictions were made by numerically solving the diffusion equations with boundary conditions appropriate for thin-film couples. Good agreement was obtained between the calculated values and nearly all the experimental data reported in the literature using different configurations of thin-film couples. Although the methodology was applied successfully to predict the growth of Co2Si, CoSi, and CoSi2 sequentially in thin-film Co/Si couples, it is equally applicable to any binary thin-film diffusion couple.

  18. Modeling Lymphoma Growth in an Evolving Lymph Node Using a Diffuse Domain Approach

    NASA Astrophysics Data System (ADS)

    Chuang, Yao-Li; Cristini, Vittorio; Chen, Ying; Li, Xiangrong; Frieboes, Hermann; Lowengrub, John

    2012-11-01

    Tumor growth often poses as a multiphase free-boundary problem as tumor cells aggregate into distinct subdomains due to differentiated cell-cell and cell-matrix adhesion. In ``Three-dimensional multispecies nonlinear tumor growth - I Model and numerical method'' [Wise et al., J. Theor. Biol. 253, pp. 524-543 (2008)], we have developed a multiphase Cahn-Hilliard model to study morphological patterns of tumor growth in a homogeneous open environment, and the results resembled in-vitro experiments. In living tissues, however, tumors are often confined in a closed environment of an organ, where the tissue geometry can also evolve in response to the pressure of tumor growth. Here we adapt our previous Cahn-Hilliard tumor growth model to an evolving geometry using a recently developed diffuse domain approach. We use the model to study the growth of lymphoma in a lymph node that swells during the process. An angiogenesis model for tumor-induced vasculature is also adapted to investigate substrate distribution and drug delivery within the lymph node. Supported by NIH-PSOC grant 1U54CA143907-01.

  19. Parasite-mediated growth patterns and nutritional constraints in a cavity-nesting bird.

    PubMed

    O'Brien, Erin L; Dawson, Russell D

    2008-01-01

    1. Trade-offs between growth and immunity of nestling birds can be influenced by parasites, but the magnitude of these effects may depend on availability of critical dietary nutrients. Owing to their importance for both immune system function and growth, dietary carotenoids have the potential to mediate parasite-induced developmental strategies of avian hosts. 2. The effects of ectoparasitic blow flies Protocalliphora spp. and dietary carotenoids (lutein and zeaxanthin) on immune function and patterns of growth in nestling mountain bluebirds Sialia currucoides were investigated by combining parasite removal and carotenoid supplementation treatments in a 2 x 2 design. 3. Supplemental carotenoids enhanced nestlings' T-cell-mediated immune response following intradermal injection of phytohaemagglutinin. 4. The effect of carotenoid supplementation on rate of mass gain depended on whether broods were exposed to parasites: among parasitized broods, those receiving supplemental carotenoids gained mass more rapidly than nonsupplemented broods, whereas there was no effect of supplemental carotenoids on growth of mass in broods that had parasites removed. This suggests that additional dietary carotenoids allowed nestlings to compensate for the otherwise detrimental effects of parasites on mass gain. For length of the eighth primary feather at fledging, early and late broods differed in their response to parasitism: early broods showed an increase in feather length when parasites were removed, while nestlings in late broods had shorter feathers in the absence of parasites. We suggest that this may reflect within-season variation in parasite-mediated growth strategies of nestlings. 5. Maternal condition was positively associated with mass, condition and rate of feather growth of offspring under all conditions, and also influenced nestling immunocompetence, but only in the absence of parasites. 6. We conclude that dietary carotenoids alleviate some of the detrimental effects of parasites on nestling birds; however, parasites also appear to specifically influence other growth and resource allocation strategies, and possibly constrain maternal or genetic effects on offspring phenotype, irrespective of dietary carotenoid availability. PMID:18177333

  20. Diffusion coefficients for crystal nucleation and growth in deeply undercooled glass-forming liquids.

    PubMed

    Fokin, Vladimir M; Schmelzer, Jürn W P; Nascimento, Marcio L F; Zanotto, Edgar D

    2007-06-21

    We calculate, employing the classical theory of nucleation and growth, the effective diffusion coefficients controlling crystal nucleation of nanosize clusters and the subsequent growth of micron-size crystals at very deep undercoolings, below and above Tg, using experimental nucleation and growth data obtained for stoichiometric Li2O.2SiO2 and Na2O.2CaO.3SiO2 glasses. The results show significant differences in the magnitude and temperature dependence of these kinetic coefficients. We explain this difference showing that the composition and/or structure of the nucleating critical clusters deviate from those of the stable crystalline phase. These results for diffusion coefficients corroborate our previous conclusion for the same glasses, based on different experiments, and support the view that, even for the so-called case of stoichiometric (polymorphic) crystallization, the nucleating phase may have a different composition and/or structure as compared to the parent glass and the evolving macroscopic crystalline phase. This finding gives a key to explain the discrepancies between calculated (by classical nucleation theory) and experimentally observed nucleation rates in these systems, in particular, and in deeply undercooled glass-forming liquids, in general. PMID:17600425

  1. Stochastic Boundary, Diffusion, Emittance Growth and Lifetime calculation for the RHIC e-lens

    SciTech Connect

    Abreu,N.P.; Fischer, W.; Luo, Y.; Robert-Demolaize, G.

    2009-01-20

    To compensate the large tune shift and tune spread generated by the head-on beam-beam interactions in polarized proton operation in the Relativistic Heavy Ion Collider (RHIC), a low energy electron beam with proper Gaussian transverse profiles was proposed to collide head-on with the proton beam. In this article, using a modified version of SixTrack [1], we investigate stability of the single particle in the presence of head-on beam-beam compensation. The Lyapunov exponent and action diffusion are calculated and compared between the cases without and with beam-beam compensation for two different working points and various bunch intensities. Using the action diffusion results the emittance growth rate and lifetime of the proton beam is also estimated for the different scenarios.

  2. In-situ observation of impurity diffusion boundary layer in silicon Czochralski growth

    NASA Astrophysics Data System (ADS)

    Kakimoto, Koichi; Eguchi, Minoru; Watanabe, Hisao; Hibiya, Taketoshi

    1990-01-01

    In-situ observation of the impurity diffusion boundary layer during single crystal growth of indium-doped silicon was carried out by X-ray radiography. The difference in the transmitted X-ray image compared with molten silicon just beneath the crystal-melt interface was attributed to the concentration of indium impurities having a larger absorption coefficient. The intensity profile of the transmitted X-ray can be reproduced by a transmittance calculation that considers the meniscus shape and impurity distribution. The impurity distribution profile near the crystal-melt interface was estimated using the Burton-Prim-Slichter (BPS) equation. The observed impurity diffusion boundary layer thickness was about 0.5 mm. It was found that the boundary layer thickness was not constant in the radial direction, which cannot be explained by the BPS theory, since it is based on a one-dimensional calculation.

  3. PHYSICAL REVIEW B 90, 045410 (2014) Island size evolution and molecular diffusion during growth of organic thin films followed by

    E-print Network

    Schreiber, Frank

    2014-01-01

    PHYSICAL REVIEW B 90, 045410 (2014) Island size evolution and molecular diffusion during growth of organic thin films followed by time-resolved specular and off-specular scattering C. Frank,1 J. Nov´ak,1 growth study of ultrathin films of the prototypical organic semiconductor diindenoperylene (DIP, C32H16

  4. Wetting Layer Super-Diffusive Motion and QSE Growth in Pb/Si

    NASA Astrophysics Data System (ADS)

    Tringides, M. C.; Hupalo, M.; Man, K. L.; Loy, M. M. T.; Altman, M. S.

    The unusual growth mode of uniform height islands discovered in Pb/Si was related to the electronic energy modulation with island height due to quantum size effects (QSEs). In addition to these energetic reasons provided by QSE, there is also the question of kinetics, i.e., how atoms move at relatively low temperatures (as low as 150 K) to build the islands in the short time of minutes. Controlled experiments with different techniques have shown the intriguing role of the dense wetting layer in transporting mass. STM experiments monitoring how unstable islands transform into stable islands have shown that the wetting layer between the islands moves selectively to the unstable islands, climbs over their sides, forms quickly rings of constant width ˜ 20 nm, and finally it completes the island top, but at a slower rate than the ring completion. This growth is independent of the starting interface, whether it is the amorphous wetting layer on the Si(111) (7 × 7) or the well-ordered Si(111)-Pb ? (surd 3× surd 3) surface (except Pb diffusion on the latter interface is faster by a factor of ˜ 5). Real-time low-energy electron microscopy (LEEM) observations of mass transport phenomena have confirmed the fast mobility of the wetting layer in Pb/Si and in addition have revealed some unusual features that are unexpected from classical diffusion behavior. The experiment monitors the refilling of a circular vacant area generated by a laser pulse. The concentration profile does not disperse as in normal diffusion, the refilling speed ? x/? t is constant (instead of ? x/surd ? t = constant), and the equilibration time diverges below a critical coverage, ? c, as 1/tau ˜ (? c - ?)^{-kappa}. The absolute value of the refilling speed 0.05 nm/s at 190 K is orders of magnitude higher than what is expected from Pb diffusion on Pb crystals at higher temperatures. These results are compared with predictions of three candidate models: (i) a conventional diffusion model with a step-like coverage-dependent diffusion coefficient Dc(?), (ii) a model with mass transport due to adatoms on top of the wetting layer with coverage-dependent adatom vacancy formation energy, and (iii) the carpet unrolling mechanism proposed for other systems. None of these models can account for the unusual observations, which suggests that the wetting layer most likely enters a novel state of very high mobility for ? > ? c, similar to a phase transition that needs to be better understood theoretically.

  5. Moderators of the Diffusion of Technological Innovation: Growth of the Japanese PC Industry

    E-print Network

    West, Joel

    1996-01-01

    This pattern of technology diffusion in Japan is examined inTechnology and Innovation Management Division Innovation Diffusion:Technology and Innovation Management Division Moderators of the Diffusion

  6. On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion

    USGS Publications Warehouse

    Kile, D.E.; Eberl, D.D.

    2003-01-01

    Crystal growth experiments were conducted using potassium alum and calcite crystals in aqueous solution under both non-stirred and stirred conditions to elucidate the mechanism for size-dependent (proportionate) and size-independent (constant) crystal growth. Growth by these two laws can be distinguished from each other because the relative size difference among crystals is maintained during proportionate growth, leading to a constant crystal size variance (??2) for a crystal size distribution (CSD) as the mean size increases. The absolute size difference among crystals is maintained during constant growth, resulting in a decrease in size variance. Results of these experiments show that for centimeter-sized alum crystals, proportionate growth occurs in stirred systems, whereas constant growth occurs in non-stirred systems. Accordingly, the mechanism for proportionate growth is hypothesized to be related to the supply of reactants to the crystal surface by advection, whereas constant growth is related to supply by diffusion. Paradoxically, micrometer-sized calcite crystals showed proportionate growth both in stirred and in non-stirred systems. Such growth presumably results from the effects of convection and Brownian motion, which promote an advective environment and hence proportionate growth for minute crystals in non-stirred systems, thereby indicating the importance of solution velocity relative to crystal size. Calcite crystals grown in gels, where fluid motion was minimized, showed evidence for constant, diffusion-controlled growth. Additional investigations of CSDs of naturally occurring crystals indicate that proportionate growth is by far the most common growth law, thereby suggesting that advection, rather than diffusion, is the dominant process for supplying reactants to crystal surfaces.

  7. Structure and morphology in diffusion-driven growth of nanowires: the case of ZnTe.

    PubMed

    Rueda-Fonseca, P; Bellet-Amalric, E; Vigliaturo, R; den Hertog, M; Genuist, Y; André, R; Robin, E; Artioli, A; Stepanov, P; Ferrand, D; Kheng, K; Tatarenko, S; Cibert, J

    2014-01-01

    Gold-catalyzed ZnTe nanowires were grown at low temperature by molecular beam epitaxy on a ZnTe(111) B buffer layer, under different II/VI flux ratios, including with CdTe insertions. High-resolution electron microscopy and energy-dispersive X-ray spectroscopy (EDX) gave information about the crystal structure, polarity, and growth mechanisms. We observe, under stoichiometric conditions, the simultaneous presence of zinc-blende and wurtzite nanowires spread homogeneously on the same sample. Wurtzite nanowires are cylinder-shaped with a pyramidal-structured base. Zinc-blende nanowires are cone-shaped with a crater at their base. Both nanowires and substrate show a Te-ended polarity. Te-rich conditions favor zinc-blende nanowires, while Zn-rich suppress nanowire growth. Using a diffusion-driven growth model, we present a criterion for the existence of a crater or a pyramid at the base of the nanowires. The difference in nanowire morphology indicates lateral growth only for zinc-blende nanowires. The role of the direct impinging flux on the nanowire's sidewall is discussed. PMID:24564275

  8. Concentration Dependence of Solution Shear Viscosity and Solute Mass Diffusivity in Crystal Growth from Solutions

    NASA Technical Reports Server (NTRS)

    Izmailov, Alexander F.; Myerson, Allan S.

    1995-01-01

    The physical properties of a supersaturated binary solution such as its density rho, shear viscosity eta, and solute mass diffusivity D are dependent on the solute concentration c: rho = rho(c), eta = eta(c), and D = D(c). The diffusion boundary layer equations related to crystal growth from solution are derived for the case of natural convection with a solution density, a shear viscosity, and a solute diffusivity that are all depen- dent on solute concentration. The solution of these equations has demonstrated the following. (1) At the vicinity of the saturation concentration c(sub s) the solution shear viscosity eta depends on rho as eta(sub s) = eta(rho(sub s))varies as square root of rho(c(sub s)). This theoretically derived result has been verified in experiments with several aqueous solutions of inorganic and organic salts. (2) The maximum solute mass transfer towards the growing crystal surface can be achieved for values of c where the ratio of d ln(D(c)/dc) to d ln(eta(c)/dc) is a maximum.

  9. Growth by rectified diffusion of strongly acoustically forced gas bubbles in nearly saturated liquids.

    PubMed

    Louisnard, Olivier; Gomez, Francisco

    2003-03-01

    The growth or dissolution of small gas bubbles (R0<15 microm) by rectified diffusion in nearly saturated liquids, subject to low frequencies (20 kHzdiffusion threshold radius merges with the Blake threshold radius, which means that a growing bubble is also an inertially oscillating bubble. On the assumption that such a bubble keeps its integrity up to the shape instability threshold predicted by single-bubble theory, a numerical estimation and a fully analytical approximation of its growth rate are derived. On the one hand, the merging of the two thresholds raises the problem of the construction and self-sustainment of acoustic cavitation fields. On the other hand, the lifetime of the growing inertial bubbles calculated within the present theory is found to be much shorter than the time necessary to rectify argon. This allows an alternative interpretation of the absence of single-bubble sonoluminescence emission in multibubble fields, without resorting to the conventional picture of shape instabilities caused by the presence of other bubbles. PMID:12689182

  10. Coupler induced transverse kick and emittance growth in single cell elliptical cavities of 10 MeV superconducting electron linac injector

    NASA Astrophysics Data System (ADS)

    Dechoudhury, Siddhartha; Pandey, Hemendra Kumar; Pratim Dutta, Dipta; Naik, Vaishali; Chakrabarti, Alok; Chao, Yu-Chiu; Laxdal, Robert E.

    2015-03-01

    A Capture Cryo Module (CCM) consisting of two single cell 1.3 GHz, ? = 1, niobium cavities is being developed for the superconducting electron linac injector at VECC. Electron beam of 100 keV and 2 mA from a thermionic gun will be accelerated in the CCM and thereafter in an Injector Cryo Module (ICM) to 10 MeV. Single cell cavities in the CCM are independently phased and a coaxial TTF-III coupler is chosen for rf power coupling into each cavity. The presence of the coupler perturbs the field symmetry of the cavity introducing local transverse kicks to the incoming electron beam in the coupler region. Numerical analysis taking into account the changing velocity profile as well as the off-axis field seen by the electron as it moves through the cavities has been carried out for estimating the kick. The variation of the kick with longitudinal position of electrons in the beam bunch introduces transverse emittance growth. This has been calculated using the field seen by the electron. The analytical calculations are compared with results from particle tracking with simulated 3D fields. It is found that coupler induced kick does not appreciably change the emittance values at 10 MeV.

  11. Diffusion

    NSDL National Science Digital Library

    Christopher Thomas (None; )

    2006-11-09

    Diffusion is the movement of particles from an area of high concentration to an area of low concentration. The molecules move until equilibrium is reached. If a perfume is sprayed on one side of the room, the perfume molecules will eventually spread out all over the room until there are equal concentrations of the molecules throughout the space.

  12. Analysis of growth of non-spherical silica particles in a counterflow diffusion flame considering chemical reactions, coagulation and coalescence

    Microsoft Academic Search

    B. W. Lee; J. I. Jeong; J. Y. Hwang; M. Choi; S. H. Chung

    2001-01-01

    The evolution of non-spherical silica particles in a counterflow diffusion flame has been studied considering the effects of convection, diffusion, thermophoresis, chemical reactions, coagulation and coalescence. The counterflow geometry provides a one-dimensional flow field along the stagnation point streamline which greatly simplifies the analysis of non-spherical particle growth. Flame analysis of multi-step chemical reactions of hydrogen\\/oxygen including both oxidation and

  13. Monolithic, multiple-wavelength vertical-cavity surface-emitting laser arrays by surface-controlled MOCVD growth rate enhancement and reduction

    Microsoft Academic Search

    G. G. Ortiz; S. Q. Luong; S. Z. Sun; Julian Cheng; H. Q. Hou; G. A. Vawter; B. E. Hammons

    1997-01-01

    Monolithic, multiple-wavelength vertical-cavity surface-emitting laser (VCSEL) arrays have been obtained by the surface-controlled enhancement and reduction of the MOCVD epitaxial growth rate, achieving a periodic, graded wavelength span greater than 30 nm. Room-temperature (RT), electrically pumped continuous-wave (CW) lasing is demonstrated, with uniform threshold currents of 5.5±0.5 mA with typical output powers of 0.5 mW. We show here for the

  14. Bayesian calibration, validation, and uncertainty quantification of diffuse interface models of tumor growth.

    PubMed

    Hawkins-Daarud, Andrea; Prudhomme, Serge; van der Zee, Kristoffer G; Oden, J Tinsley

    2013-12-01

    The idea that one can possibly develop computational models that predict the emergence, growth, or decline of tumors in living tissue is enormously intriguing as such predictions could revolutionize medicine and bring a new paradigm into the treatment and prevention of a class of the deadliest maladies affecting humankind. But at the heart of this subject is the notion of predictability itself, the ambiguity involved in selecting and implementing effective models, and the acquisition of relevant data, all factors that contribute to the difficulty of predicting such complex events as tumor growth with quantifiable uncertainty. In this work, we attempt to lay out a framework, based on Bayesian probability, for systematically addressing the questions of Validation, the process of investigating the accuracy with which a mathematical model is able to reproduce particular physical events, and Uncertainty quantification, developing measures of the degree of confidence with which a computer model predicts particular quantities of interest. For illustrative purposes, we exercise the process using virtual data for models of tumor growth based on diffuse-interface theories of mixtures utilizing virtual data. PMID:23053536

  15. Diffusion

    NSDL National Science Digital Library

    Since the advent of the internet, a number of artists and related organizations have become interested in utilizing the web to promulgate new forms of artistic creation and their subsequent dissemination. Supported by the Arts Council of England, these Diffusion eBooks are essentially pdf files that readers can download, print out and make into booklets. As the site suggests, "the Diffusion format challenges conventions of interactivity-blending the physical and the virtual and breaking the dominance of mouse and screen as the primary forms of human computer interaction...the format's aim is to take the reader away from the screen and computer and engage them in the process of production." There are a number of creative booklets available here for visitors, complete with instruction on how to assemble them for the desired effect. For anyone with even a remote interest in the possibilities afforded by this rather curious new form of expression, this website is worth a look.

  16. Predicting in vivo glioma growth with the reaction diffusion equation constrained by quantitative magnetic resonance imaging data

    NASA Astrophysics Data System (ADS)

    Hormuth, David A., II; Weis, Jared A.; Barnes, Stephanie L.; Miga, Michael I.; Rericha, Erin C.; Quaranta, Vito; Yankeelov, Thomas E.

    2015-07-01

    Reaction–diffusion models have been widely used to model glioma growth. However, it has not been shown how accurately this model can predict future tumor status using model parameters (i.e., tumor cell diffusion and proliferation) estimated from quantitative in vivo imaging data. To this end, we used in silico studies to develop the methods needed to accurately estimate tumor specific reaction–diffusion model parameters, and then tested the accuracy with which these parameters can predict future growth. The analogous study was then performed in a murine model of glioma growth. The parameter estimation approach was tested using an in silico tumor ‘grown’ for ten days as dictated by the reaction–diffusion equation. Parameters were estimated from early time points and used to predict subsequent growth. Prediction accuracy was assessed at global (total volume and Dice value) and local (concordance correlation coefficient, CCC) levels. Guided by the in silico study, rats (n = 9) with C6 gliomas, imaged with diffusion weighted magnetic resonance imaging, were used to evaluate the model’s accuracy for predicting in vivo tumor growth. The in silico study resulted in low global (tumor volume error <8.8%, Dice >0.92) and local (CCC values >0.80) level errors for predictions up to six days into the future. The in vivo study showed higher global (tumor volume error >11.7%, Dice <0.81) and higher local (CCC <0.33) level errors over the same time period. The in silico study shows that model parameters can be accurately estimated and used to accurately predict future tumor growth at both the global and local scale. However, the poor predictive accuracy in the experimental study suggests the reaction–diffusion equation is an incomplete description of in vivo C6 glioma biology and may require further modeling of intra-tumor interactions including segmentation of (for example) proliferative and necrotic regions.

  17. Influence of mass diffusion on the stability of thermophoretic growth of a solid from the vapor phase

    NASA Technical Reports Server (NTRS)

    Castillo, J. L.; Garcia-Ybarra, P. L.; Rosner, D. E.

    1991-01-01

    The stability of solid planar growth from a binary vapor phase with a condensing species dilute in a carrier gas is examined when the ratio of depositing to carrier species molecular mass is large and the main diffusive transport mechanism is thermal diffusion. It is shown that a deformation of the solid-gas interface induces a deformation of the gas phase isotherms that increases the thermal gradients and thereby the local mass deposition rate at the crests and reduces them at the valleys. The initial surface deformation is enhanced by the modified deposition rates in the absence of appreciable Fick/Brownian diffusion and interfacial energy effects.

  18. Adhesion between cells, diffusion of growth factors, and elasticity of the AER produce the paddle shape of the chick limb

    PubMed Central

    Pop?awski, Nikodem J.; Swat, Maciej; Gens, J. Scott; Glazier, James A.

    2007-01-01

    A central question in developmental biology is how cells interact to organize into tissues? In this paper, we study the role of mesenchyme-ectoderm interaction in the growing chick limb bud using Glazier and Graner's cellular Potts model, a grid-based stochastic framework designed to simulate cell interactions and movement. We simulate cellular mechanisms including cell adhesion, growth, and division and diffusion of morphogens, to show that differential adhesion between the cells, diffusion of growth factors through the extracellular matrix, and the elastic properties of the apical ectodermal ridge together can produce the proper shape of the limb bud. PMID:18167520

  19. The effects of plasma diffusion and viscosity on turbulent instability growth

    SciTech Connect

    Haines, Brian M., E-mail: bmhaines@lanl.gov; Vold, Erik L.; Molvig, Kim; Aldrich, Charles; Rauenzahn, Rick [Los Alamos National Laboratory, MS T087, Los Alamos, New Mexico 87545 (United States)

    2014-09-15

    We perform two-dimensional simulations of strongly–driven compressible Rayleigh–Taylor and Kelvin–Helmholtz instabilities with and without plasma transport phenomena, modeling plasma species diffusion, and plasma viscosity in order to determine their effects on the growth of the hydrodynamic instabilities. Simulations are performed in hydrodynamically similar boxes of varying sizes, ranging from 1 ?m to 1?cm in order to determine the scale at which plasma effects become important. Our results suggest that these plasma effects become noticeable when the box size is approximately 100 ?m, they become significant in the 10 ?m box, and dominate when the box size is 1 ?m. Results suggest that plasma transport may be important at scales and conditions relevant to inertial confinement fusion, and that a plasma fluid model is capable of representing some of the kinetic transport effects.

  20. The effects of plasma diffusion and viscosity on turbulent instability growth

    NASA Astrophysics Data System (ADS)

    Haines, Brian M.; Vold, Erik L.; Molvig, Kim; Aldrich, Charles; Rauenzahn, Rick

    2014-09-01

    We perform two-dimensional simulations of strongly-driven compressible Rayleigh-Taylor and Kelvin-Helmholtz instabilities with and without plasma transport phenomena, modeling plasma species diffusion, and plasma viscosity in order to determine their effects on the growth of the hydrodynamic instabilities. Simulations are performed in hydrodynamically similar boxes of varying sizes, ranging from 1 ?m to 1 cm in order to determine the scale at which plasma effects become important. Our results suggest that these plasma effects become noticeable when the box size is approximately 100 ?m, they become significant in the 10 ?m box, and dominate when the box size is 1 ?m. Results suggest that plasma transport may be important at scales and conditions relevant to inertial confinement fusion, and that a plasma fluid model is capable of representing some of the kinetic transport effects.

  1. Growth of nanoparticles and microparticles by controlled reaction-diffusion processes.

    PubMed

    Walliser, Roché M; Boudoire, Florent; Orosz, Eszter; Tóth, Rita; Braun, Artur; Constable, Edwin C; Rácz, Zoltán; Lagzi, István

    2015-02-10

    The synthesis of different sizes of nanoparticles and microparticles is important in designing nanostructured materials with various properties. Wet synthesis methods lack the flexibility to create various sizes of particles (particle libraries) using fixed conditions without the repetition of the steps in the method with a new set of parameters. Here, we report a synthesis method based on nucleation and particle growth in the wake of a moving chemical front in a gel matrix. The process yields well-separated regions (bands) filled with nearly monodisperse nanoparticles and microparticles, with the size of the particles varying from band to band in a predictable way. The origin of the effect is due to an interplay of a precipitation reaction of the reagents and their diffusion that is controlled in space and time by the moving chemical front. The method represents a new approach and a promising tool for the fast and competitive synthesis of various sizes of colloidal particles. PMID:25586218

  2. Sn diffusion during Ni germanide growth on Ge1-xSnx

    NASA Astrophysics Data System (ADS)

    Demeulemeester, J.; Schrauwen, A.; Nakatsuka, O.; Zaima, S.; Adachi, M.; Shimura, Y.; Comrie, C. M.; Fleischmann, C.; Detavernier, C.; Temst, K.; Vantomme, A.

    2011-11-01

    We report on the redistribution of Sn during Ni germanide formation on Ge1-xSnx/ and its influence on the thin film growth and properties. These results show that the reaction involves the formation of Ni5Ge3 and NiGe. Sn redistributes homogenously in both phases, in which the Sn/Ge ratio retains the ratio of the as-deposited Ge1-xSnx film. Sn continues to diffuse after full NiGe formation and segregates in two regions: (1) at the interface between the germanide and Ge1-xSnx and (2) at the surface, which has major implications for the thin film and contact properties.

  3. Diffusion-driven precipitate growth and ripening of oxygen precipitates in boron doped silicon by dynamical x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Will, J.; Gröschel, A.; Bergmann, C.; Spiecker, E.; Magerl, A.

    2014-03-01

    X-ray Pendellösung fringes from three silicon single crystals measured at 900 °C are analyzed with respect to density and size of oxygen precipitates within a diffusion-driven growth model and compared with TEM investigations. It appears that boron doped (p+) material shows a higher precipitate density and a higher strain than moderately (p-) boron crystals. In-situ diffraction reveals a diffusion-driven precipitate growth followed by a second growth regime in both materials. An interpretation of the second growth regime in terms of Ostwald ripening yields surface energy values (around 70 erg/cm2) similar to published data. Further, an increased nucleation rate by a factor of ˜13 is found in the p+ sample as compared to a p- sample at a nucleation temperature of 450 °C.

  4. Diffusion-driven precipitate growth and ripening of oxygen precipitates in boron doped silicon by dynamical x-ray diffraction

    SciTech Connect

    Will, J., E-mail: will@krist.uni-erlangen.de; Gröschel, A.; Bergmann, C.; Magerl, A. [Crystallography and Structural Physics, University of Erlangen-Nürnberg, Staudtstr. 3, 91058 Erlangen (Germany); Spiecker, E. [Center for Nanoanalysis and Electron Microscopy, University of Erlangen-Nürnberg, Cauerstr. 6, 91058 Erlangen (Germany)

    2014-03-28

    X-ray Pendellösung fringes from three silicon single crystals measured at 900?°C are analyzed with respect to density and size of oxygen precipitates within a diffusion-driven growth model and compared with TEM investigations. It appears that boron doped (p+) material shows a higher precipitate density and a higher strain than moderately (p-) boron crystals. In-situ diffraction reveals a diffusion-driven precipitate growth followed by a second growth regime in both materials. An interpretation of the second growth regime in terms of Ostwald ripening yields surface energy values (around 70?erg/cm{sup 2}) similar to published data. Further, an increased nucleation rate by a factor of ?13 is found in the p+ sample as compared to a p- sample at a nucleation temperature of 450?°C.

  5. Cardiac looping may be driven by compressive loads resulting from unequal growth of the heart and pericardial cavity. Observations on a physical simulation model

    PubMed Central

    Bayraktar, Meriç; Männer, Jörg

    2014-01-01

    The transformation of the straight embryonic heart tube into a helically wound loop is named cardiac looping. Such looping is regarded as an essential process in cardiac morphogenesis since it brings the building blocks of the developing heart into an approximation of their definitive topographical relationships. During the past two decades, a large number of genes have been identified which play important roles in cardiac looping. However, how genetic information is physically translated into the dynamic form changes of the looping heart is still poorly understood. The oldest hypothesis of cardiac looping mechanics attributes the form changes of the heart loop (ventral bending ? simple helical coiling ? complex helical coiling) to compressive loads resulting from growth differences between the heart and the pericardial cavity. In the present study, we have tested the physical plausibility of this hypothesis, which we call the growth-induced buckling hypothesis, for the first time. Using a physical simulation model, we show that growth-induced buckling of a straight elastic rod within the confined space of a hemispherical cavity can generate the same sequence of form changes as observed in the looping embryonic heart. Our simulation experiments have furthermore shown that, under bilaterally symmetric conditions, growth-induced buckling generates left- and right-handed helices (D-/L-loops) in a 1:1 ratio, while even subtle left- or rightward displacements of the caudal end of the elastic rod at the pre-buckling state are sufficient to direct the buckling process toward the generation of only D- or L-loops, respectively. Our data are discussed with respect to observations made in biological “models.” We conclude that compressive loads resulting from unequal growth of the heart and pericardial cavity play important roles in cardiac looping. Asymmetric positioning of the venous heart pole may direct these forces toward a biased generation of D- or L-loops. PMID:24772086

  6. First-principles study of carbon diffusion in bulk nickel during the growth of fishbone-type carbon nanofibers

    Microsoft Academic Search

    Yi-An Zhu; Ying-Chun Dai; De Chen; Wei-Kang Yuan

    2007-01-01

    Ab initio plane wave density functional theory calculations are performed to investigate the carbon diffusion in bulk nickel during the growth of fishbone-type carbon nanofibers (CNFs). Results indicate that the octahedral interstitial sites are preferred for C dissolution relative to the tetrahedral sites. And the heat of solution of C in paramagnetic (PM) Ni is larger than that in ferromagnetic

  7. PHYSICAL REVIEW B 83, 115329 (2011) Diffusion and interface growth in hafnium oxide and silicate ultrathin films on Si(001)

    E-print Network

    Garfunkel, Eric

    2011-01-01

    PHYSICAL REVIEW B 83, 115329 (2011) Diffusion and interface growth in hafnium oxide and silicate ultrathin films on Si(001) L.V. Goncharova,1,* M. Dalponte,1 T. Feng,1 T. Gustafsson,1 E. Garfunkel,2 P elemental depth distributions and elucidate oxygen transport in 2­5 nm thick HfO2 and HfSiOx films grown

  8. Hydrogen adsorption and diffusion, and subcritical-crack growth in high strength steels and nickel base alloys

    NASA Technical Reports Server (NTRS)

    Wei, R. P.; Klier, K.; Simmons, G. W.; Chornet, E.

    1973-01-01

    Embrittlement, or the enhancement of crack growth by gaseous hydrogen in high strength alloys, is of primary interest in selecting alloys for various components in the space shuttle. Embrittlement is known to occur at hydrogen gas pressures ranging from fractions to several hundred atmospheres, and is most severe in the case of martensitic high strength steels. Kinetic information on subcritical crack growth in gaseous hydrogen is sparse at this time. Corroborative information on hydrogen adsorption and diffusion is inadequate to permit a clear determination of the rate controlling process and possible mechanism in hydrogen enhanced crack growth, and for estimating behavior over a range of temperatures and pressures. Therefore, coordinated studies of the kinetics of crack growth, and adsorption and diffusion of hydrogen, using identical materials, have been initiated. Comparable conditions of temperature and pressure will be used in the chemical and mechanical experiments. Inconel 718 alloy and 18Ni(200) maraging steel have been selected for these studies. Results from these studies are expected to provide not only a better understanding of the gaseous hydrogen embrittlement phenomenon itself, but also fundamental information on hydrogen adsorption and diffusion, and crack growth information that can be used directly for design.

  9. Relationships Between Infarct Growth, Clinical Outcome, and Early Recanalization in Diffusion and Perfusion Imaging for Understanding Stroke Evolution (DEFUSE)

    PubMed Central

    Olivot, Jean-Marc; Mlynash, Michael; Thijs, Vincent N.; Kemp, Stephanie; Lansberg, Maarten G.; Wechsler, Lawrence; Schlaug, Gottfried; Bammer, Roland; Marks, Michael P.; Albers, Gregory W.

    2009-01-01

    Background and Purpose The purpose of this study was to determine the relationships between ischemic lesion growth, recanalization, and clinical response in stroke patients with and without a perfusion/diffusion mismatch. Methods DEFUSE is an open label multicenter study in which 74 consecutive acute stroke patients were treated with intravenous tPA 3 to 6 hours after stroke onset. Magnetic resonance imaging (MRI) scans were obtained before, 3 to 6 hours after, and 30 days after treatment. Lesion growth was defined as the difference between the final infarct volume (30 day FLAIR) and the baseline diffusion lesion. Baseline MRI profiles were used to categorize 44 patients into Mismatch versus Absence of Mismatch subgroups. Early recanalization was assessed in 28 patients with an initial vessel lesion on magnetic resonance angiography. Infarct growth was compared based on whether a favorable clinical response (FCR) occurred and whether early recanalization was achieved. Results In the Mismatch subgroup, FCR was associated with less infarct growth P=0.03 and early recanalization was predictive of both FCR (odds ratio: 22, P=0.047) and reduced infarct growth P=0.024. There was no significant relationship between recanalization, infarct growth, and clinical outcome in the Absence of Mismatch subgroup. A threshold of <7 cc of growth had the highest sensitivity and specificity for predicting a FCR in Mismatch patients (odds ratio: 65, P=0.015, sensitivity 82%, specificity 75%). Conclusion In contrast to Absence of Mismatch patients, significant associations between recanalization, reduced infarct growth, and favorable clinical response were documented in patients with a perfusion/diffusion mismatch who were treated with tPA within 3 to 6 hours after stroke onset. These findings support the Mismatch hypothesis but require validation in a larger study. PMID:18566302

  10. Growth behavior of intermetallic compounds during reactive diffusion between aluminum alloy 1060 and magnesium at 573-673 K

    NASA Astrophysics Data System (ADS)

    Xiao, Lin; Wang, Ning

    2015-01-01

    A potential new research reactor fuel design proposes to use U-Mo fuel in a Mg matrix clad with Al. Interdiffusion between the Mg containing fuel core and Al cladding can result in the formation of intermetallic compounds that can be detrimental to fuel element performance. The kinetics of the reactive diffusion in the binary Al-Mg system was experimentally studied. Layers of the intermetallic compounds, ? (Al3Mg2) and ? (Al12Mg17) phases, were formed between the Al alloy 1060 and Mg during annealing. The ? layer was observed to grow faster than the ? phase. The thickness of each layer can be expressed by a power function of the annealing time with the exponent n close to 0.5 for the ? phase and less than 0.5 for the ? phase. The results suggest that the growth of ? phase is controlled by lattice diffusion and that of the ? phase by grain boundary and lattice diffusion. Metallographic examination showed the grain boundary diffusion in the form of columnar growth of ? phase during annealing. Based on the reactive diffusion equation developed in this work, in the absence of irradiation effects, it will take more than 110 h to consume a half thickness of 400 ?m of the cladding.

  11. A model for the diffusive growth of hydrate saturation anomalies in layered sediments

    NASA Astrophysics Data System (ADS)

    Rempel, A. W.

    2011-10-01

    Sediment particles affect the phase behavior of gas hydrates, both by increasing the surface energy where pore geometry forces hydrate crystals to attain high curvatures and through wetting interactions that cause aqueous films to coat particle surfaces. These effects produce only slight changes to the gas solubility through most of the hydrate stability zone, so the particle size has only a modest influence on the rate of hydrate accumulation when the sediments are homogeneous. In hydrate reservoirs, however, discontinuous changes in sediment properties are common and such stratigraphic boundaries often coincide with hydrate anomalies. These anomalies are a natural consequence of variations in subsurface sediment properties. By accounting for sediment-hydrate interactions, I show how compositional diffusion supplies the growth of hydrate spikes in coarse-grained sediments immediately adjacent to hydrate-free regions (HFRs) in more fine-grained sediments where the solubility is slightly elevated. Over timescales comparable with Milankovitch cycles, hydrate spikes are typically less than a meter in width and contain essentially all of the hydrate that would have otherwise occupied the much larger adjacent HFR if sediment heterogeneities were absent. Hydrate can form in the more fine-grained sediments only once the spike achieves a sufficiently high saturation level (often >90% of pore volume) that the solubility is continuous across the stratigraphic boundary. The wetting interactions that stabilize much of the residual liquid when hydrate forms an interconnected skeleton spanning many pore diameters can also partially unload sediment particle contacts, and lead to the growth of segregated hydrate nodules and lenses.

  12. [Selected parameters of hemolymph biochemistry in two growth classes of the snail Planorbarius corneus (L.), regarding infection of the pulmonary cavity with Chaetogaster limnaei limnaei baer (Oligochaeta: naididae)].

    PubMed

    Pokora, Z; Szilman, P; Szilman, E

    1993-01-01

    We have proved highly significant differences in glucose concentration and activity of alpha-amylase in haemolymph of two growth classes of Planorbarius corneus with width of shell smaller and equal or greater than 20 mm, respectively. Both these parameters were higher and were characterized by greater range of individual variability in snails with smaller width of shell. Any differences in levels of total protein and haemoglobin in haemolymph of these animals, in comparison with adult individuals, were not observed. Effect of infection of the pulmonary cavity of investigated snails with Chaetogaster limnaei limnaei on the examined parameters was not ascertained. PMID:8128728

  13. Precision Measurements of Binary and Multicomponent Diffusion Coefficients in Protein Solutions Relevant to Crystal Growth

    E-print Network

    Annunziata, Onofrio

    Precision Measurements of Binary and Multicomponent Diffusion Coefficients in Protein Solutions binary diffusion coefficients Dv for lysozyme chloride/water at concentrations from 0.43 to 3.08 mM (6 Naples, Italy ReceiVed October 1, 1998 Abstract: Accurate models of protein diffusion are important

  14. MICROSCOPIC SIMULATION OF EPIDERMAL GROWTH FACTOR RECEPTOR DIFFUSION ON CORRALLED MEMBRANE SURFACES

    Microsoft Academic Search

    Anne Marie; S. Niehaus; Dionisios G. Vlachos; Jeremy S. Edwards; Petr Plechac; Roger Tribe

    The current understanding of how receptors diffuse and cluster in the plasma membrane is limited. Data from single particle tracking and laser tweezer experiments have suggested that membrane diffusion is affected by the presence of barriers dividing the membrane into corrals. Herein, we have developed a stochastic, spatial model to simulate the effect of corrals on the diffusion of receptors

  15. Precision of Interferometric Diffusion Coefficients in a Four-Component System Relevant to Protein Crystal Growth: Lysozyme-Tetra(ethylene glycol)-NaCl-H2O

    E-print Network

    Annunziata, Onofrio

    Crystal Growth: Lysozyme-Tetra(ethylene glycol)-NaCl-H2O Onofrio Annunziata, Alessandro Vergara, Luigi in a four-component system, relevant to crystal growth. The motivation follows. The quality of protein for modeling diffusive transport in crystal growth. In this protein context, we find that the flows

  16. New explicit equations for the accurate calculation of the growth and evaporation of hydrometeors by the diffusion of water vapor

    NASA Technical Reports Server (NTRS)

    Srivastava, R. C.; Coen, J. L.

    1992-01-01

    The traditional explicit growth equation has been widely used to calculate the growth and evaporation of hydrometeors by the diffusion of water vapor. This paper reexamines the assumptions underlying the traditional equation and shows that large errors (10-30 percent in some cases) result if it is used carelessly. More accurate explicit equations are derived by approximating the saturation vapor-density difference as a quadratic rather than a linear function of the temperature difference between the particle and ambient air. These new equations, which reduce the error to less than a few percent, merit inclusion in a broad range of atmospheric models.

  17. Growth of Ultralong ZnS/SiO2 Core-Shell Nanowires by Volume and Surface Diffusion VLS Process

    E-print Network

    Wang, Zhong L.

    Growth of Ultralong ZnS/SiO2 Core-Shell Nanowires by Volume and Surface Diffusion VLS Process to be composed of a single-crystalline ZnS core and amorphous SiO2 shell. Gold catalyst particles were found and optical devices.1,2,6 Zinc sulfide (ZnS), a member of the wurtzite family, is a direct wide band gap (3

  18. Elimination of gold diffusion in the heterostructure core/shell growth of high performance Ge/Si nanowire HFETs

    SciTech Connect

    Picraux, Samuel T [Los Alamos National Laboratory; Dayeh, Shadi A [Los Alamos National Laboratory

    2010-01-01

    Radial heterostructure nanowires offer the possibility of surface, strain, band-edge and modulution-doped engineering for optimizing performance of nanowire transistors. Synthesis of such heterostructures is non-trivial and is typically accompanied with Au diffusion on the nanowire sidewalls that result in rough morphology and undesired whisker growth. Here, they report a novel growth procedure to synthesize Ge/Si core/multi-shell nanowires by engineering the growth interface between the Au seed and the nanowire sidewalls. Single crystal Ge/Si core/multi-shell nanowires are used to fabricate side-by-side FET transistors with and without Au diffusion. Elimination of Au diffusion in the synthesis of such structures led to {approx} 2X improvement in hole field-effect mobility, transconductances and currents. Initial prototype devices with a 10 nm PECVD nitride gate dielectric resulted in a record maximum on current of 430 {micro}A/V (I{sub DS}L{sub G}/{pi}DV{sub DS}), {approx} 2X higher than ever achieved before in a p-type FET.

  19. Model on cell movement, growth, differentiation and de-differentiation: reaction-diffusion equation and wave propagation.

    PubMed

    Wang, Mao-Xiang; Li, Yu-Jung; Lai, Pik-Yin; Chan, C K

    2013-06-01

    We construct a model for cell proliferation with differentiation into different cell types, allowing backward de-differentiation and cell movement. With different cell types labeled by state variables, the model can be formulated in terms of the associated transition probabilities between various states. The cell population densities can be described by coupled reaction-diffusion partial differential equations, allowing steady wavefront propagation solutions. The wavefront profile is calculated analytically for the simple pure growth case (2-states), and analytic expressions for the steady wavefront propagating speeds and population growth rates are obtained for the simpler cases of 2-, 3- and 4-states systems. These analytic results are verified by direct numerical solutions of the reaction-diffusion PDEs. Furthermore, in the absence of de-differentiation, it is found that, as the mobility and/or self-proliferation rate of the down-lineage descendant cells become sufficiently large, the propagation dynamics can switch from a steady propagating wavefront to the interesting situation of propagation of a faster wavefront with a slower waveback. For the case of a non-vanishing de-differentiation probability, the cell growth rate and wavefront propagation speed are both enhanced, and the wavefront speeds can be obtained analytically and confirmed by numerical solution of the reaction-diffusion equations. PMID:23807466

  20. Analysis of the diffusion controlled growth of cobalt silicides in bulk and thin film couples

    Microsoft Academic Search

    T. Barge; P. Gas; F. M. D'Heurle

    1995-01-01

    The solid state reaction between Co and Si has been studied in bulk diffusion couples between 850 and 1100 C. At the scale of the observations made, the three phases Co2Si, CoSi, and CoSi2 are found to grow simultaneously, according to diffusion controlled kinetics. The results are analyzed in term of the Nernst-Einstein equation that directly relates diffusion fluxes to

  1. Native-oxide-based selective area growth of InP nanowires via metal-organic molecular beam epitaxy mediated by surface diffusion

    NASA Astrophysics Data System (ADS)

    Calahorra, Yonatan; Greenberg, Yaakov; Cohen, Shimon; Ritter, Dan

    2012-06-01

    The growth of InP nanowires on an InP(111) B substrate is reported. The substrate native oxide was not removed from the surface prior to growth. Nanowires were grown at 400?°C from gold catalysts in a selective area manner, without bulk growth. Unlike SiO2-based metal-organic molecular beam epitaxy selective area growth, the growth reported here is mediated by surface diffusion with a characteristic diffusion length of 4 ?m, about an order of magnitude larger than values for diffusion on bare substrates. A pre-growth heating treatment at 450?°C was found to increase the yield of nanowire nucleation from the gold catalysts.

  2. The Origins and Development of the Diffusion of Innovations Paradigm as an Example of Scientific Growth.

    ERIC Educational Resources Information Center

    Valente, Thomas W.; Rogers, Everett M.

    1995-01-01

    Describes some of the history of rural sociological research on the diffusion of agricultural innovations, and shows how research followed (and deviated from) the Kuhnian concept of paradigm development. Examines the Iowa Hybrid Seed Corn Study which contributed to the rise of sociological diffusion research. (103 references) (AEF)

  3. Diffusion Versus Surface Limitations in Vapor-Solvent Growth of Germanium

    Microsoft Academic Search

    F. Jona

    1965-01-01

    Measurements of transport rates as functions of pressure in the systems germanium—iodine and germanium—bromine have been carried out. The results are discussed in terms of Lever's theory for diffusive transport. It is concluded that while the germanium—iodine system is highly diffusion limited, the germanium—bromine system is noticeably surface controlled.

  4. Explaining the trade-growth link: Assessing diffusion-based and structure-based models of exchange.

    PubMed

    Clark, Rob; Mahutga, Matthew C

    2013-03-01

    International development scholars advance contrasting theoretical explanations for the hypothesized link between trade and growth. Diffusion-based models suggest that trade with integrated partners provides states with greater access to technical knowledge. Structure-based models propose that trading with isolated partners produces a bargaining advantage. In this study, we adjudicate between these competing visions by applying Bonacich's (1987) measure of power centrality to the international trade network. We manipulate the procedure's "attenuation factor" (?) such that a state's trade centrality can be enhanced when a state is connected to either central or isolated partners. Drawing from a sample of 101 states during the 1980-2000 period, we use difference-of-logs models to assess the impact of trade centrality on economic growth net of controls. We find that the positive relationship between trade centrality and growth peaks when states trade with isolated partners in the periphery. PMID:23347484

  5. Diffusion-controlled and ``diffusionless'' crystal growth near the glass transition temperature: Relation between liquid dynamics and growth kinetics of seven ROY polymorphs

    NASA Astrophysics Data System (ADS)

    Sun, Ye; Xi, Hanmi; Ediger, M. D.; Richert, Ranko; Yu, Lian

    2009-08-01

    The liquid dynamics of 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, named ROY for its red, orange, and yellow crystal polymorphs, was characterized by dielectric spectroscopy and differential scanning calorimetry. Four of these polymorphs show fast "diffusionless" crystal growth at low temperatures while three others do not. ROY was found to be a typical fragile organic liquid. Its ? relaxation process has time-temperature superposition symmetry across the viscous range (??=100 s-100 ns) with the width of the relaxation peak characterized by a constant ?KWW of 0.73. No secondary relaxation peak was observed, even with glasses made by fast quenching. For the polymorphs not showing fast crystal growth in the glassy state, the growth rate has a power-law relation with ??, u ???-?, where ? ?0.7. For the polymorphs showing fast crystal growth in the glassy state, the growth is so fast near and below the glass transition temperature Tg that thousands of molecular layers can be added to the crystalline phase during one structural relaxation time of the liquid. In the glassy state, this mode of growth slows slightly over time. This slowdown is not readily explained by the effect of physical aging on the thermodynamic driving force of crystallization, the glass vapor pressure, or the rate of structural relaxation. This study demonstrates that from the same liquid or glass, the growth of some polymorphs is accurately described as being limited by the rate of structural relaxation or bulk diffusion, whereas the growth of other polymorphs is too fast to be under such control.

  6. Hydrogen adsorption and diffusion, and subcritical-crack growth in high-strength steels and nickel base alloys

    NASA Technical Reports Server (NTRS)

    Wei, R. P.; Klier, K.; Simmons, G. W.

    1974-01-01

    Coordinated studies of the kinetics of crack growth and of hydrogen adsorption and diffusion were initiated to develop information that is needed for a clearer determination of the rate controlling process and possible mechanism for hydrogen enhanced crack growth, and for estimating behavior over a range of temperatures and pressures. Inconel 718 alloy and 18Ni(200) maraging steel were selected for these studies. 18Ni(250) maraging steel, 316 stainless steel, and iron single crystal of (111) orientation were also included in the chemistry studies. Crack growth data on 18Ni(250) maraging steel from another program are included for comparison. No sustained-load crack growth was observed for the Inconel 718 alloy in gaseous hydrogen. Gaseous hydrogen assisted crack growth in the 18Ni maraging steels were characterized by K-independent (Stage 2) extension over a wide range of hydrogen pressures (86 to 2000 torr or 12 kN/m2 to 266 kN/m2) and test temperatures (-60 C to +100 C). The higher strength 18Ni(250) maraging steel was more susceptible than the lower strength 200 grade. A transition temperature was observed, above which crack growth rates became diminishingly small.

  7. Analysis of ?18O and ?D values of environmental waters at high temporal and spatial resolution by continuous diffusion sampling cavity ring-down spectrometry

    NASA Astrophysics Data System (ADS)

    Munksgaard, Niels; Bass, Adrian; Wurster, Chris; Bird, Michael

    2013-04-01

    A novel sampling device utilises diffusion through porous PTFE tubing to deliver water vapour continuously from a liquid water source for analysis of ?18O and ?D values by Cavity Ring-Down Spectrometry (CRDS). Comparison of isotopic data for a range of water samples analysed by Diffusion Sampling-CRDS (DS-CRDS) and Isotope Ratio Mass Spectrometry (IRMS) shows significant linear correlations between the two methods allowing for accurate standardisation of DS-CRDS data. The internal precision for an integration period of 3 min (standard deviation = 0.1 ‰ and 0.3 ‰ for ?18O and ?D values, respectively) is similar to analysis of water by injection/evaporation CRDS of discrete water samples. The isotopic effects of variable air and water temperature, water vapour concentration and water pumping rate were found to be either negligible or correctable by analysis of water standards. Separation of the analysed water vapour from non-volatile dissolved and particulate contaminants in the liquid sample minimises interferences associated with CRDS analyses of many aqueous samples. Coupling of the DS-CRDS instrument to an auto sampler enables rapid analysis (10 min) of discrete water samples. The DS-CRDS system was used in the first continuous shipboard measurement of ?18O and ?D of water. Combined with continuous salinity recordings, a data set of nearly 6,000 isotope measurements was made at 30-s intervals during a 3-day voyage through the Great Barrier Reef Lagoon. Precise identification of river plumes within the Great Barrier Reef Lagoon was possible because unique ?18O/?D-salinity relationships of individual plumes were measured at high spatial and temporal resolution. Continuous shipboard measurement of ?18O/?D values by DS-CRDS provides additional discriminatory power for assessing water mass formation processes and histories at a small fraction of the cost of traditional isotope analysis of discrete samples. In a second application of DS-CRDS, continuous real-time analysis, at 30-s intervals, of precipitation at an Australian tropical location revealed extreme and rapidly changing ?18O and ?D values related to variations in moisture source areas, transport paths and precipitation histories. The range of ?18O (-19.6 ‰ to +2.6 ‰) and ?D (-140 ‰ to +13 ‰) values from almost 6,000 measurements of nine rain events over 15 days during an 8-month period at a single location was comparable with the range measured in 1532 monthly samples from all seven Australian Global Network of Isotopes in Precipitation stations from 1962 to 2002. Extreme variations in ?18O (-8.7 ‰ to -19.6 ‰) and ?D (-54 ‰ to -140 ‰) were recorded within a single 4-h period. Real-time stable isotope monitoring of environmental waters at high temporal and spatial resolution enables new and powerful tracer applications in climatology, hydrology, eco-physiology and palaeo-climatology.

  8. Hypoxia upregulates adhesion ability to peritoneum through a transforming growth factor-beta-dependent mechanism in diffuse-type gastric cancer cells.

    PubMed

    Noda, Satoru; Yashiro, Masakazu; Nshii, Takafumi; Hirakawa, Kosei

    2010-03-01

    Gastric cancer cells leaving the primary tumour are exposed to low oxygen levels in the peritoneal cavity; however, peritoneal metastatic phenotypes of hypoxic cancer cells remain unclear. We used 6 gastric cancer cell lines, including 3 diffuse-type gastric cancer (DGC) and 3 non-DGC cell lines. Using adhesion assay, we examined the effect of hypoxic conditions on their ability to adhere to peritoneal components. The expression level of transforming growth factor-beta (TGF-beta) and integrins mRNA of cancer cells was examined using reverse transcriptase-polymerase chain reaction. We further examined the effect of anti-integrin neutralising antibodies and a TGF-beta receptor inhibitor on the adhesion ability of hypoxic cancer cells. The binding ability of DGC cells was higher than that of non-DGC cells; it was significantly increased by hypoxic (1% O2) conditions compared to normoxic (21% O2) conditions. In contrast, no remarkable change in adhesion ability was observed in the non-DGC cells under normoxic and hypoxic conditions. Integrins and TGF-beta expression of hypoxic DGC cells was significantly higher than that of normoxic cells. TGF-beta increased the adhesion ability and alpha2-, alpha3- and alpha5-integrin expression of hypoxic DGC cells, whereas the TGF-beta receptor inhibitor decreased them. Neutralising antibodies against alpha2-, alpha3- and alpha5-integrin inhibited the adhesion ability of DGC cells. These findings suggested that hypoxic conditions promote the adhesion of DGC cells to the peritoneum. The upregulation of alpha2-, alpha3- and alpha5-integrin by TGF-beta under hypoxic conditions may be one of the mechanisms responsible for the high metastatic potential of hypoxic DGC cells to the peritoneum. PMID:20144860

  9. Discerning crystal growth from diffusion profiles in zoned olivine by in situ Mg–Fe isotopic analyses

    USGS Publications Warehouse

    Sio, Corliss Kin I.; Dauphas, Nicolas; Teng, Fang-Zhen; Chaussidon, Marc; Helz, Rosalind T.; Roskosz, Mathieu

    2013-01-01

    Mineral zoning is used in diffusion-based geospeedometry to determine magmatic timescales. Progress in this field has been hampered by the challenge to discern mineral zoning produced by diffusion from concentration gradients inherited from crystal growth. A zoned olivine phenocryst from Kilauea Iki lava lake (Hawaii) was selected for this study to evaluate the potential of Mg and Fe isotopes for distinguishing these two processes. Microdrilling of the phenocryst (?300 ?m drill holes) followed by MC-ICPMS analysis of the powders revealed negatively coupled Mg and Fe isotopic fractionations (?26Mg from +0.1‰ to ?0.2‰ and ?56Fe from ?1.2‰ to ?0.2‰ from core to rim), which can only be explained by Mg–Fe exchange between melt and olivine. The data can be explained with ratios of diffusivities of Mg and Fe isotopes in olivine scaling as D2/D1 = (m1/m2)? with ?Mg ?0.16 and ?Fe ?0.27. LA-MC-ICPMS and MC-SIMS Fe isotopic measurements are developed and are demonstrated to yield accurate ?56Fe measurements within precisions of ?0.2‰ (1 SD) at spatial resolutions of ?50 ?m. ?56Fe and ?26Mg stay constant with Fo# in the rim (late-stage overgrowth), whereas in the core (original phenocryst) ?56Fe steeply trends toward lighter compositions and ?26Mg trends toward heavier compositions with higher Fo#. A plot of ?56Fe vs. Fo# immediately distinguishes growth-controlled from diffusion-controlled zoning in these two regions. The results are consistent with the idea that large isotopic fractionation accompanies chemical diffusion in crystals, whereas fractional crystallization induces little or no isotopic fractionation. The cooling timescale inferred from the chemical-isotope zoning profiles is consistent with the documented cooling history of the lava lake. In the absence of geologic context, in situ stable isotopic measurements may now be used to interpret the nature of mineral zoning. Stable isotope measurements by LA-MC-ICPMS and MC-SIMS can be used as standard petrologic tools to identify samples for diffusion-based geospeedometry.

  10. Ion assisted growth of B{sub 4}C diffusion barrier layers in Mo/Si multilayered structures

    SciTech Connect

    Bruijn, S.; Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F. [FOM Institute for Plasma Physics Rijnhuizen, P.O. Box 3430 BE, Nieuwegein (Netherlands)

    2012-03-15

    We investigated the thermal stability of e-beam deposited Mo/B{sub 4}C/Si/B{sub 4}C layered systems, with and without ion assistance during the growth of the B{sub 4}C diffusion barrier layers. The thermal stability was investigated by in situ thermal annealing during grazing incidence X-ray reflection. By studying partially treated B{sub 4}C barrier layers, we found that the improvement in thermal stability is caused by an enhanced density of the B{sub 4}C layer.

  11. Numerical and Physical Simulation of the Low-Velocity Air Flow in a Diffuser with a Circular Cavity in the Case of Suction of the Air from the Central Cylindrical Body Positioned in the Cavity

    NASA Astrophysics Data System (ADS)

    Isaev, S. A.; Guvernyuk, S. V.; Zubin, M. A.; Baranov, P. A.; Ermakov, A. M.

    2015-01-01

    Comparative analysis of the results of solution of the steady-state Reynolds equations closed with the use of the shear-stress transfer model for the air fl ow in a divergent channel with suction of the air from the surface of the cylindrical central body positioned in the circular vortex cavity built in the lower wall of the channel with the corresponding experimental data has been performed.

  12. Improving protein crystal quality by decoupling nucleation and growth in vapor diffusion.

    PubMed Central

    Saridakis, E.; Chayen, N. E.

    2000-01-01

    A simple method for growing protein crystals in the metastable zone using the vapor diffusion technique is described. The coverslips holding the hanging drops are transferred, after being incubated for some time at conditions normally giving many small crystals, over reservoirs at concentrations that normally yield clear drops. Fewer, much larger and better diffracting crystals are obtained, compared with conventional crystallization at similar conditions. To our knowledge, this is the first report of a significant crystal improvement due to "backing off" from nucleation conditions, using the hanging drop method. A correlation of the transfer time with published results for vapor diffusion equilibration of poly(ethylene glycol) solutions is also presented. PMID:10794418

  13. Cavity coalescence in superplastic deformation

    SciTech Connect

    Stowell, M.J.; Livesey, D.W.; Ridley, N.

    1984-01-01

    An analysis of the probability distribution function of particles randomly dispersed in a solid has been applied to cavitation during superplastic deformation and a method of predicting cavity coalescence developed. Cavity size distribution data were obtained from two microduplex nickel-silver alloys deformed superplastically to various extents at elevated temperature, and compared to theoretical predictions. Excellent agreement occurred for small void sizes but the model underestimated the number of voids in the largest size groups. It is argued that the discrepancy results from a combination of effects due to non-random cavity distributions and to enhanced growth rates and incomplete spheroidization of the largest cavities.

  14. Two-dimensional growth of a root system modelled as a diffusion process. I. Analytical solutions

    Microsoft Academic Search

    P. de Willigen; M. Heinen; A. Mollier; M. Van Noordwijk

    2002-01-01

    For functioning of a root system, the temporal development of distribution of roots in the soil is important. For example, for computing uptake of water and nutrients the root length density distribution might be required. A way to describe root proliferation is to consider it as a diffusion process with a first-order sink term accounting for decay. In this paper,

  15. Cluster growth and dynamic scaling in a two-lane driven diffusive system

    Microsoft Academic Search

    I. T. Georgiev; B. Schmittmann; R. K. P. Zia

    2006-01-01

    Using high precision Monte Carlo simulations and a mean-field theory, we explore coarsening phenomena in a simple driven diffusive system. The model is reminiscent of vehicular traffic on a two-lane ring road. At sufficiently high density, the system develops jams (clusters) which coarsen with time. A key parameter is the passing probability, ?. For small values of ?, the growing

  16. Cluster growth and dynamic scaling in a two-lane driven diffusive system

    Microsoft Academic Search

    I. T. Georgiev; B. Schmittmann; R. K. P. Zia

    2006-01-01

    Using high precision Monte Carlo simulations and a mean-field theory, we explore coarsening phenomena in a simple driven diffusive system. The model is reminiscent of vehicular traffic on a two-lane ring road. At sufficiently high density, the system develops jams (clusters) which coarsen with time. A key parameter is the passing probability, gamma. For small values of gamma, the growing

  17. The Growth and Decline of Research on the Diffusion of the News, 1945-1985

    Microsoft Academic Search

    MELVIN L. DE FLEUR

    1987-01-01

    Research on word-of-mouth diffusion of news, presented initially by media, began in 1945. The Kennedy assassination stimulated numerous studies. However, by the 1970s the pace of such research slowed. At present, the tradition has all but run out. The findings of forty years yield six broad generalizations, but little theory. In view of the vital role of the news in

  18. Directed d-mer diffusion describing the Kardar-Parisi-Zhang surface growth

    E-print Network

    Odor, Geza; Heinig, Karl-Heinz

    2009-01-01

    We show that d+1-dimensional surface growth models can be mapped onto driven lattice gases of d-mers. The Kardar-Parisi-Zhang growth corresponds to one dimensional drift of d-mers perpendicular to the (d-1)-dimensional "plane" spanned by the d-mers. This facilitates efficient, bit-coded algorithms with generalized Kawasaki dynamics of spins. Our simulations in d=2,3,4,5 dimensions provide scaling exponent estimates on much larger system sizes and simulations times published so far, where the effective growth exponent exhibits an increase. We provide evidence for the agreement of some field theoretical predictions and numerics. We show that the (2+1)-dimensional exponents conciliate with the values suggested by Lassig within error margin. The increase of the effective growth exponents suggest a crossover to a different, anisotropic scaling behavior in d=5 dimensions.

  19. International Technology Diffusion and the Growth of TFP in the Manufacturing Sector of Developing Economies

    Microsoft Academic Search

    Andreas Savvides; Marios Zachariadis

    2005-01-01

    AbstractThis paper evaluates various channels through which foreign technology diffuses to the manufacturing sector of developing economies. These economies undertake virtually no own R&D, so they rely on foreign technology to a much larger extent than developed economies. We investigate the direct effect of foreign R&D, as well as technology embodied in imports of intermediate and capital goods and foreign

  20. Quantifying the rate of biofilm growth of S. meliloti strains in microfluidics via the diffusion coefficient of microspheres

    NASA Astrophysics Data System (ADS)

    Dorian, Matthew; Seitaridou, Effrosyni

    2014-03-01

    Understanding the rate of biofilm growth is essential for studying genes and preventing unwanted biofilms. In this study, the diffusion coefficient (D) of polystyrene microspheres was used to quantify biofilm growth rates of Sinorhizobia meliloti, a nitrogen fixing bacteria that forms a symbiotic relationship with alfalfa plants. Five strains were studied, two wild types (8530 expR+ and 1021) and three mutants in the exopolysaccharide (EPS I, EPS II) synthesis (8530 exoY , 9034 expG , and 9030-2 expA 1); 1021 and 9030-2 expA 1 are known to be unable to form biofilms. Each strain was inserted into a microfluidic channel with the microspheres. As the cultures grew, the spheres' D values were obtained every 24 hours for 4 days using fluorescence microscopy. Although the D values for 9030-2 expA 1 were inconclusive, 8530 expR+ , 8530 exoY , and 9034 expG showed significant decreases in D between 3 days of growth (| z | > 2 . 25 , p < 0 . 025). The data also indicated that 8530 expR+ and 8530 exoY grew at similar rates. There was no significant change in D for 1021 (?2(2) = 5 . 76 , p > 0 . 05), which shows the lack of a structured biofilm community. Thus, D can be used as an indicator of the presence of a biofilm and its development.

  1. An image-driven parameter estimation problem for a reaction-diffusion glioma growth model with mass effects

    PubMed Central

    Hogea, Cosmina; Davatzikos, Christos; Biros, George

    2010-01-01

    We present a framework for modeling gliomas growth and their mechanical impact on the surrounding brain tissue (the so-called, mass-effect). We employ an Eulerian continuum approach that results in a strongly coupled system of nonlinear Partial Differential Equations (PDEs): a reaction-diffusion model for the tumor growth and a piecewise linearly elastic material for the background tissue. To estimate unknown model parameters and enable patient-specific simulations we formulate and solve a PDE-constrained optimization problem. Our two main goals are the following: (1) to improve the deformable registration from images of brain tumor patients to a common stereotactic space, thereby assisting in the construction of statistical anatomical atlases; and (2) to develop predictive capabilities for glioma growth, after the model parameters are estimated for a given patient. To our knowledge, this is the first attempt in the literature to introduce an adjoint-based, PDE-constrained optimization formulation in the context of image-driven modeling spatio-temporal tumor evolution. In this paper, we present the formulation, and the solution method and we conduct 1D numerical experiments for preliminary evaluation of the overall formulation/methodology. PMID:18026731

  2. Fluctuations in reaction-diffusion systems: a new exactly soluble growth model

    SciTech Connect

    van Dongen, P.G.J.

    1988-10-01

    The method of compounding moments devised by Van Kampen is used to study the spatial fluctuations in a model describing the irreversible formation of clusters. The reaction and diffusion constants in this model are chosen independent of the cluster sizes. For a monodisperse initial distribution explicit expressions are calculated for the equal-time and two-time correlation functions of the concentrations of m- and n-mers. For general initial conditions the fluctuations in the mass density are considered and a scaling theory is presented for the fluctuations at large times. Extensions to more general models are discussed.

  3. Growth of a root system described as diffusion. II. Numerical model and application

    Microsoft Academic Search

    Marius Heinen; Alain Mollier; Peter De Willigen

    2003-01-01

    In simulation models for water movement and nutrient transport, uptake of water and nutrients by roots forms an essential part. As roots are spatially distributed, prediction of root growth and root distribution is crucial for modelling water and nutrient uptake. In a preceding paper, De Willigen et al. (2002; Plant and Soil 240, 225–234) presented an analytical solution for describing

  4. Diffusion of Ideas by 19th Century Feminists: The Growth of Women's Magazines.

    ERIC Educational Resources Information Center

    Jolliffe, Lee

    The communications of suffragist Lucy Stone illustrate the changes that the growth of women's magazines brought to nineteenth century feminists. As indicated in letters to friends and family, Lucy Stone became an active proponent of women's rights at a time when public speaking tours were the best means of reaching a wide audience. As the printing…

  5. A hybrid stochastic-deterministic computational model accurately describes spatial dynamics and virus diffusion in HIV-1 growth competition assay.

    PubMed

    Immonen, Taina; Gibson, Richard; Leitner, Thomas; Miller, Melanie A; Arts, Eric J; Somersalo, Erkki; Calvetti, Daniela

    2012-11-01

    We present a new hybrid stochastic-deterministic, spatially distributed computational model to simulate growth competition assays on a relatively immobile monolayer of peripheral blood mononuclear cells (PBMCs), commonly used for determining ex vivo fitness of human immunodeficiency virus type-1 (HIV-1). The novel features of our approach include incorporation of viral diffusion through a deterministic diffusion model while simulating cellular dynamics via a stochastic Markov chain model. The model accounts for multiple infections of target cells, CD4-downregulation, and the delay between the infection of a cell and the production of new virus particles. The minimum threshold level of infection induced by a virus inoculum is determined via a series of dilution experiments, and is used to determine the probability of infection of a susceptible cell as a function of local virus density. We illustrate how this model can be used for estimating the distribution of cells infected by either a single virus type or two competing viruses. Our model captures experimentally observed variation in the fitness difference between two virus strains, and suggests a way to minimize variation and dual infection in experiments. PMID:22814476

  6. Control of Seed Respiration and Growth in Vicia faba by Oxygen and Temperature: No Evidence for an Oxygen Diffusion Barrier

    PubMed Central

    de Visser, Ries; Dekhuijzen, Harold M.; Verkerke, Dick R.

    1990-01-01

    The rate of dry matter accumulation by seeds of Vicia faba L. cv. Minica increases with temperature in the range of 16 to 26°C. The duration of dry matter accumulation decreases with temperature, resulting in a decrease of final seed dry weight. In this study we test the hypothesis that a diffusion barrier for O2, located in the seed coat, inhibits seed respiration and growth. The rate of O2 uptake of intact seeds and of excised embryos and seed coats (separated seeds) was measured in air and buffer at 16, 20, and/or 26°C at various O2 concentrations and developmental stages. Oxygen uptake rates of intact seeds in buffer were only 9 to 15% of those in air. In buffer, the respiration rate of intact seeds decreased at a pO2 below air saturation (21 kilopascals), whereas separated seeds showed a decline of O2 uptake only below 80% of air saturation. In air, embryo excision had no effect on the sensitivity of seed respiration to pO2, at both 20 and 26°C. In air at 20°C, separated and intact seeds showed similar rates of O2 uptake. Oxygen uptake by intact seeds, both halfway and beyond the linear growth phase, showed a temperature coefficient Q10 of 2.3 and was insensitive to pO2 in the range of 80 to 100% of ambient. These results indicate that V. faba seed respiration in air is not limited by the diffusion of O2 into the seed. PMID:16667521

  7. Effective emissivity of a cylindrical cavity with an inclined bottom: I. Isothermal cavity

    NASA Astrophysics Data System (ADS)

    Prokhorov, Alexander V.; Hanssen, Leonard M.

    2004-12-01

    The Monte Carlo method is applied to the computation of the effective emissivity of a specular-diffuse isothermal blackbody cavity shaped by a cylindrical generatrix, a flat inclined bottom and a flat diaphragm. The dependences of the normal effective emissivity on the bottom inclination angle are studied for different cavity depths and various values of the diffuse component of the cavity wall reflectance. The distributions of the local normal effective emissivity over the cavity aperture and the dependences of the integrated effective emissivity on the distance between the aperture and the radiation detector are computed. The choice of optimal geometrical parameters for improving the radiometric performance of artificial blackbodies is discussed.

  8. Microfabricated diffusion source

    DOEpatents

    Oborny, Michael C. (Albuquerque, NM); Frye-Mason, Gregory C. (Cedar Crest, NM); Manginell, Ronald P. (Albuquerque, NM)

    2008-07-15

    A microfabricated diffusion source to provide for a controlled diffusion rate of a vapor comprises a porous reservoir formed in a substrate that can be filled with a liquid, a headspace cavity for evaporation of the vapor therein, a diffusion channel to provide a controlled diffusion of the vapor, and an outlet to release the vapor into a gas stream. The microfabricated diffusion source can provide a calibration standard for a microanalytical system. The microanalytical system with an integral diffusion source can be fabricated with microelectromechanical systems technologies.

  9. Wetting Layer Super-Diffusive Motion and QSE Growth in Pb\\/Si

    Microsoft Academic Search

    M. C. Tringides; M. Hupalo; K. L. Man; M. M. T. Loy; M. S. Altman

    \\u000a The unusual growth mode of uniform height islands discovered in Pb\\/Si was related to the electronic energy modulation with\\u000a island height due to quantum size effects (QSEs). In addition to these energetic reasons provided by QSE, there is also the\\u000a question of kinetics, i.e., how atoms move at relatively low temperatures (as low as 150 K) to build the islands in

  10. Diffusion generated motion for grain growth in two and three dimensions

    NASA Astrophysics Data System (ADS)

    Elsey, Matt; Esedog¯lu, Selim; Smereka, Peter

    2009-11-01

    An efficient algorithm for accurately simulating curvature flow for large networks of curves in two dimensions and surfaces in three dimensions on uniform grids is proposed. This motion arises in the technologically important problem of simulating grain boundary motion in polycrystalline materials. In this formulation grain boundaries are zero-level sets of signed distance functions. Curvature motion is achieved by first diffusing locally maintained signed distance functions followed by a reinitialization step. A technique is devised to allow a single signed distance function to represent a large subset of spatially separated grains. Hundreds of thousands of grains can be simulated using a small number of signed distance functions (in this work, 32 in two dimensions and 64 in three dimensions are more than sufficient) using modest computational hardware.

  11. Single vacancy defects diffusion at the initial stage of graphene growth: A first-principles study

    NASA Astrophysics Data System (ADS)

    Du, H. B.; Jia, Y.; Sun, Q.; Guo, Z. X.

    2015-06-01

    The migration of a single vacancy (SV) defect in graphene fragment (GF) has been investigated by density functional theory (DFT). The results revealed that a single vacancy defect is easy to migrate to the GF edge. The interaction between an SV and a five-numbered ring at the edge results in two neighboring five-membered rings finally, while the interaction between an SV and a seven-membered ring defect at the edge of the GF leads to a five-numbered ring and a neighbor seven-numbered ring. Our findings shed light upon understanding of the growth process of the graphene grain boundary.

  12. Diffusion limited aggregation of particles with different sizes: Fractal dimension change by anisotropic growth

    NASA Astrophysics Data System (ADS)

    Braga, F. L.; Mattos, O. A.; Amorin, V. S.; Souza, A. B.

    2015-07-01

    Clusters formation models have been extensively studied in literature, and one of the main task of this research area is the analysis of the particle aggregation processes. Some work support that the main characteristics of this processes are strictly correlated to the cluster morphology, for example in DLA. It is expected that in the DLA clusters formation with particles containing different sizes the modification of the aggregation processes can be responsible for changes in the DLA morphology. The present article is going to analyze the formation of DLA clusters of particles with different sizes and show that the aggregates obtained by this approach generate an angle selection mechanism on dendritic growth that influences the shielding effect of the DLA edge and affect the fractal dimension of the clusters.

  13. Toward CH4 dissociation and C diffusion during Ni/Fe-catalyzed carbon nanofiber growth: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Fan, Chen; Zhou, Xing-Gui; Chen, De; Cheng, Hong-Ye; Zhu, Yi-An

    2011-04-01

    First-principles calculations have been performed to investigate CH4 dissociation and C diffusion during the Ni/Fe-catalyzed growth of carbon nanofibers (CNFs). Two bulk models with different Ni to Fe molar ratios (1:1 and 2:1) are constructed, and x-ray diffraction (XRD) simulations are conducted to evaluate their reliability. With the comparison between the calculated and experimental XRD patterns, these models are found to be well suited to reproduce the crystalline structures of Ni/Fe bulk alloys. The calculations indicate the binding of the C1 derivatives to the Ni/Fe closest-packed surfaces is strengthened compared to that on Ni(111), arising from the upshift of the weighted d-band centers of catalyst surfaces. Then, the transition states for the four successive dehydrogenation steps in CH4 dissociation are located using the dimer method. It is found that the energy barriers for the first three steps are rather close on the alloyed Ni/Fe and Ni surfaces, while the activation energy for CH dissociation is substantially lowered with the introduction of Fe. The dissolution of the generated C from the surface into the bulk of the Ni/Fe alloys is thermodynamically favorable, and the diffusion of C through catalyst particles is hindered by the Fe component. With the combination of density functional theory calculations and kinetic analysis, the C concentration in catalyst particles is predicted to increase with the Fe content. Meanwhile, other experimental conditions, such as the composition of carbon-containing gases, feedstock partial pressure, and reaction temperature, are also found to play a key role in determining the C concentration in bulk metal, and hence the microstructures of generated CNFs.

  14. Nonvascular, Symplasmic Diffusion of Sucrose Cannot Satisfy the Carbon Demands of Growth in the Primary Root Tip of Zea mays L.

    PubMed Central

    Bret-Harte, M. S.; Silk, W. K.

    1994-01-01

    Nonvascular, symplasmic transport of sucrose (Suc) was investigated theoretically in the primary root tip of maize (Zea mays L. cv WF9 x Mo 17) seedlings. Symplasmic diffusion has been assumed to be the mechanism of transport of Suc to cells in the root apical meristem (R.T. Giaquinta, W. Lin, N.L. Sadler, V.R. Franceschi [1983] Plant Physiol 72: 362-367), which grow apical to the end of the phloem and must build all biomass with carbon supplied from the shoot or kernel. We derived an expression for the growth-sustaining Suc flux, which is the minimum longitudinal flux that would be required to meet the carbon demands of growth in the root apical meristem. We calculated this flux from data on root growth velocity, area, and biomass density, taking into account construction and maintenance respiration and the production of mucilage by the root cap. We then calculated the conductivity of the symplasmic pathway for diffusion, from anatomical data on cellular dimensions and the frequency and dimensions of plasmodesmata, and from two estimates of the diffusive conductance of a plasmodesma, derived from independent data. Then, the concentration gradients required to drive a growth-sustaining Suc flux by diffusion alone were calculated but were found not to be physiologically reasonable. We also calculated the hydraulic conductivity of the plasmodesmatal pathway and found that mass flow of Suc solution through plasmodesmata would also be insufficient, by itself, to satisfy the carbon demands of growth. However, much of the demand for water to cause cell expansion could be met by the water unloaded from the phloem while unloading Suc to satisfy the carbon demands of growth, and the hydraulic conductivity of plasmodesmata is high enough that much of that water could move symplasmically. Either our current understanding of plasmodesmatal ultrastructure and function is flawed, or alternative transport mechanisms must exist for Suc transport to the meristem. PMID:12232183

  15. Void Nucleation, Growth and Coalescence in Irradiated Metals

    SciTech Connect

    Surh, M P; Sturgeon, J B; Wolfer, W G

    2008-01-11

    A novel computational treatment of dense, stiff, coupled reaction rate equations is introduced to study the nucleation, growth, and possible coalescence of cavities during neutron irradiation of metals. Radiation damage is modeled by the creation of Frenkel pair defects and helium impurity atoms. A multi-dimensional cluster size distribution function allows independent evolution of the vacancy and helium content of cavities, distinguishing voids and bubbles. A model with sessile cavities and no cluster-cluster coalescence can result in a bimodal final cavity size distribution with coexistence of small, high-pressure bubbles and large, low-pressure voids. A model that includes unhindered cavity diffusion and coalescence ultimately removes the small helium bubbles from the system, leaving only large voids. The terminal void density is also reduced and the incubation period and terminal swelling rate can be greatly altered by cavity coalescence. Temperature-dependent trapping of voids/bubbles by precipitates and alterations in void surface diffusion from adsorbed impurities and internal gas pressure may give rise to intermediate swelling behavior through their effects on cavity mobility and coalescence.

  16. Growth patterns and nuclear distribution in white muscle fibers from black sea bass, Centropristis striata: evidence for the influence of diffusion

    PubMed Central

    Priester, Carolina; Morton, Lindsay C.; Kinsey, Stephen T.; Watanabe, Wade O.; Dillaman, Richard M.

    2011-01-01

    SUMMARY This study investigated the influence of fiber size on the distribution of nuclei and fiber growth patterns in white muscle of black sea bass, Centropristis striata, ranging in body mass from 0.45 to 4840 g. Nuclei were counted in 1 ?m optical sections using confocal microscopy of DAPIand Acridine-Orange-stained muscle fibers. Mean fiber diameter increased from 36±0.87 ?m in the 0.45 g fish to 280±5.47 ?m in the 1885 g fish. Growth beyond 2000 g triggered the recruitment of smaller fibers, thus significantly reducing mean fiber diameter. Nuclei in the smaller fibers were exclusively subsarcolemmal (SS), whereas in larger fibers nuclei were more numerous and included intermyofibrillar (IM) nuclei. There was a significant effect of body mass on nuclear domain size (F=118.71, d.f.=3, P<0.0001), which increased to a maximum in fish of medium size (282–1885 g) and then decreased in large fish (>2000 g). Although an increase in the number of nuclei during fiber growth can help preserve the myonuclear domain, the appearance of IM nuclei during hypertrophic growth seems to be aimed at maintaining short effective diffusion distances for nuclear substrates and products. If only SS nuclei were present throughout growth, the diffusion distance would increase in proportion to the radius of the fibers. These observations are consistent with the hypothesis that changes in nuclear distribution and fiber growth patterns are mechanisms for avoiding diffusion limitation during animal growth. PMID:21430198

  17. Growth of resonant cavity quantum well light emitting diodes and two-junction solar cells by solid source molecular beam epitaxy

    Microsoft Academic Search

    M. Pessa; M Toivonen; P Savolainen; S Orsila; P Sipilä; M Saarinen; P Melanen; V Vilokkinen; P Uusimaa; J Haapamaa

    2000-01-01

    Monolithic resonant cavity light emitting diodes (RCLED's) for room temperature operation at 650–670 nm and 850–880 nm wavelengths and double-junction GaInP\\/GaAs solar cells have been designed and grown using a toxic-gas-free solid-source molecular beam epitaxy method. The presence of the microcavity in RCLED's causes strong cavity enhancement, which can be utilized to modify natural spontaneous emission. These devices are shown

  18. Synchronization in an Optomechanical Cavity

    E-print Network

    Keren Shlomi; D. Yuvaraj; Ilya Baskin; Oren Suchoi; Roni Winik; Eyal Buks

    2014-10-01

    We study self-excited oscillations (SEO) in an on-fiber optomechanical cavity. Synchronization is observed when the optical power that is injected into the cavity is periodically modulated. A theoretical analysis based on the Fokker-Planck equation evaluates the expected phase space distribution (PSD) of the self-oscillating mechanical resonator. A tomography technique is employed for extracting PSD from the measured reflected optical power. Time-resolved state tomography measurements are performed to study phase diffusion and phase locking of the SEO. The detuning region inside which synchronization occurs is experimentally determined and the results are compared with the theoretical prediction.

  19. {ital Ab} {ital initio} calculations of energies and self-diffusion on flat and stepped surfaces of Al and their implications on crystal growth

    SciTech Connect

    Stumpf, R.; Scheffler, M. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin-Dahlem (Germany)] [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin-Dahlem (Germany)

    1996-02-01

    Using density-functional theory we investigate properties of Al(111), Al(100), Al(110), and stepped Al(111) surfaces, including formation energies of surfaces, steps, adatoms, and vacancies. For adsorption and diffusion of Al on flat regions of Al(111) surfaces hcp site is energetically slightly preferred over the fcc site. Energy barrier for self-diffusion on Al(111) is very low (0.04 eV). Close to either of the two sorts of close packed, monoatomic steps on Al(111), Al adatoms experience indirect attraction of {approx_lt} 0.1 eV with the step edge, which has a range of several atomic spacings and is of electronic origin. At the lower step edge, an adatom attaches with no barrier at a low-energy fivefold coordinated site. Coming from the upper terrace, it incorporates into the step by an atomic exchange process, which has a barrier below 0.1 eV for both sorts of close-packed steps. The barrier for diffusion along the lower edge is 0.32 eV at the 100-faceted step and 0.39 eV at the {l_brace}111{r_brace}-faceted step. Unexpectedly, the latter diffusion process proceeds by an exchange mechanism. Diffusion by an exchange mechanism is also found for the {open_quote}{open_quote}easy{close_quote}{close_quote} direction on the Al(110) surface, i.e., along the channels. We show that Al(110) is a model system for diffusion at the {l_brace}111{r_brace}-faceted step on Al(111) because of its similar local geometry. We estimate temperature ranges for different modes of homoepitaxial growth on Al(111). Of particular importance are the rather low barriers for diffusion across the descending steps and the rather high barriers for diffusion along the steps. We discuss island shapes on Al(111) during growth and in thermodynamic equilibrium. Depending on the temperature the growth shapes can be fractal, triangular, or hexagonal and mainly determined by kinetics; in equilibrium the island shape is hexagonal and determined by the different step formation energies. (Abstract Truncated)

  20. Coupled Geomechanical Simulations of UCG Cavity Evolution

    Microsoft Academic Search

    J P Morris; T A Buscheck; Y Hao

    2009-01-01

    This paper presents recent work from an ongoing project to develop predictive tools for cavity\\/combustion-zone growth and to gain quantitative understanding of the processes and conditions (both natural and engineered) affecting underground coal gasification (UCG). In this paper we will focus upon the development of coupled geomechanical capabilities for simulating the evolution of the UCG cavity using discrete element methodologies.

  1. Up-Regulation of Intestinal Vascular Endothelial Growth Factor by Afa/Dr Diffusely Adhering Escherichia coli

    PubMed Central

    Cane, Gaëlle; Moal, Vanessa Liévin-Le; Pagès, Gilles; Servin, Alain L.; Hofman, Paul; Vouret-Craviari, Valérie

    2007-01-01

    Background Angiogenesis has been recently described as a novel component of inflammatory bowel disease pathogenesis. The level of vascular endothelial growth factor (VEGF) has been found increased in Crohn's disease and ulcerative colitis mucosa. To question whether a pro-inflammatory Escherichia coli could regulate the expression of VEGF in human intestinal epithelial cells, we examine the response of cultured human colonic T84 cells to infection by E. coli strain C1845 that belongs to the typical Afa/Dr diffusely adhering E. coli family (Afa/Dr DAEC). Methodology VEGF mRNA expression was examined by Northern blotting and q-PCR. VEGF protein levels were assayed by ELISA and its bioactivity was analysed in endothelial cells. The bacterial factor involved in VEGF induction was identified using recombinant E. coli expressing Dr adhesin, purified Dr adhesin and lipopolysaccharide. The signaling pathway activated for the up-regulation of VEGF was identified using a blocking monoclonal anti-DAF antibody, Western blot analysis and specific pharmacological inhibitors. Principal Findings C1845 bacteria induce the production of VEGF protein which is bioactive. VEGF is induced by adhering C1845 in both a time- and bacteria concentration-dependent manner. This phenomenon is not cell line dependent since we reproduced this observation in intestinal LS174, Caco2/TC7 and INT407 cells. Up-regulation of VEGF production requires: (1) the interaction of the bacterial F1845 adhesin with the brush border-associated decay accelerating factor (DAF, CD55) acting as a bacterial receptor, and (2) the activation of a Src protein kinase upstream of the activation of the Erk and Akt signaling pathways. Conclusions Results demonstrate that a Afa/Dr DAEC strain induces an adhesin-dependent activation of DAF signaling that leads to the up-regulation of bioactive VEGF in cultured human intestinal cells. Thus, these results suggest a link between an entero-adherent, pro-inflammatory E. coli strain and angiogenesis which appeared recently as a novel component of IBD pathogenesis. PMID:18159242

  2. Fast turnover of L1 adhesions in neuronal growth cones involving both surface diffusion and exo/endocytosis of L1 molecules.

    PubMed

    Dequidt, Caroline; Danglot, Lydia; Alberts, Philipp; Galli, Thierry; Choquet, Daniel; Thoumine, Olivier

    2007-08-01

    We investigated the interplay between surface trafficking and binding dynamics of the immunoglobulin cell adhesion molecule L1 at neuronal growth cones. Primary neurons were transfected with L1 constructs bearing thrombin-cleavable green fluorescent protein (GFP), allowing visualization of newly exocytosed L1 or labeling of membrane L1 molecules by Quantum dots. Intracellular L1-GFP vesicles showed preferential centrifugal motion, whereas surface L1-GFP diffused randomly, revealing two pathways to address L1 to adhesive sites. We triggered L1 adhesions using microspheres coated with L1-Fc protein or anti-L1 antibodies, manipulated by optical tweezers. Microspheres coupled to the actin retrograde flow at the growth cone periphery while recruiting L1-GFP molecules, of which 50% relied on exocytosis. Fluorescence recovery after photobleaching experiments revealed a rapid recycling of L1-GFP molecules at L1-Fc (but not anti-L1) bead contacts, attributed to a high lability of L1-L1 bonds at equilibrium. L1-GFP molecules truncated in the intracellular tail as well as neuronal cell adhesion molecules (NrCAMs) missing the clathrin adaptor binding sequence showed both little internalization and reduced turnover rates, indicating a role of endocytosis in the recycling of mature L1 contacts at the base of the growth cone. Thus, unlike for other molecules such as NrCAM or N-cadherin, diffusion/trapping and exo/endocytosis events cooperate to allow the fast renewal of L1 adhesions. PMID:17538021

  3. Unified heat kernel regression for diffusion, kernel smoothing and wavelets on manifolds and its application to mandible growth modeling in CT images.

    PubMed

    Chung, Moo K; Qiu, Anqi; Seo, Seongho; Vorperian, Houri K

    2015-05-01

    We present a novel kernel regression framework for smoothing scalar surface data using the Laplace-Beltrami eigenfunctions. Starting with the heat kernel constructed from the eigenfunctions, we formulate a new bivariate kernel regression framework as a weighted eigenfunction expansion with the heat kernel as the weights. The new kernel method is mathematically equivalent to isotropic heat diffusion, kernel smoothing and recently popular diffusion wavelets. The numerical implementation is validated on a unit sphere using spherical harmonics. As an illustration, the method is applied to characterize the localized growth pattern of mandible surfaces obtained in CT images between ages 0 and 20 by regressing the length of displacement vectors with respect to a surface template. PMID:25791435

  4. Segmented trapped vortex cavity

    NASA Technical Reports Server (NTRS)

    Grammel, Jr., Leonard Paul (Inventor); Pennekamp, David Lance (Inventor); Winslow, Jr., Ralph Henry (Inventor)

    2010-01-01

    An annular trapped vortex cavity assembly segment comprising includes a cavity forward wall, a cavity aft wall, and a cavity radially outer wall there between defining a cavity segment therein. A cavity opening extends between the forward and aft walls at a radially inner end of the assembly segment. Radially spaced apart pluralities of air injection first and second holes extend through the forward and aft walls respectively. The segment may include first and second expansion joint features at distal first and second ends respectively of the segment. The segment may include a forward subcomponent including the cavity forward wall attached to an aft subcomponent including the cavity aft wall. The forward and aft subcomponents include forward and aft portions of the cavity radially outer wall respectively. A ring of the segments may be circumferentially disposed about an axis to form an annular segmented vortex cavity assembly.

  5. Diffusion Geometry Diffusion Geometry

    E-print Network

    Hirn, Matthew

    Diffusion Geometry Diffusion Geometry for High Dimensional Data Matthew J. Hirn July 3, 2013 #12;Diffusion Geometry Introduction Embedding of closed curve Figure: Left: A closed, non-self-intersecting curve in 3 dimensions. Right: Its embedding as a circle. #12;Diffusion Geometry Introduction Cartoon

  6. Growth Kinetics of a Reaction Rim Between Iron and Graphite/Diamond and the Carbon Diffusion Mechanism at High Pressure and Temperature

    NASA Astrophysics Data System (ADS)

    Stagno, V.; Crispin, K. L.; Shahar, A.; Fei, Y.

    2014-12-01

    Thermodynamic calculations of the fo2 on modeled bulk silicate Earth mantle composition predict the formation of Fe-Ni metal alloy at about 250-300 km in depth. At such conditions the speciation of subducted carbon will be mainly affected by the local Fe(Ni)/C ratio, with diamond, Fe3C and C-bearing Fe-Ni alloys being the most likely stable phases. To date however, no data are available to determine the effect of pressure and temperature on 1) the transport of carbon by diffusion in iron metal and 2) the kinetics of formation of carbide phases. We performed multianvil experiments between 3 and 10 GPa and temperatures of 700-1200 ºC with the aim of measuring C diffusion in ?-Fe. Glassy carbon and synthetic diamond were used as diffusants, placed directly in contact with pure iron rod rods with a thickness of 800-1400 ?m. FE-SEM was used for accurate analyses of the Fe-C interface and concentration profiles of carbon in iron were measured by electron microprobe. Results show that the diffusion coefficient for carbon in iron metal (~3x10-11 m2s-1) and the activation energy (~62 kJ/mol) are similar to previous data from 1 atm and suggest a small pressure effect. The activation volume (~1.5x10-6 m3/mol) determined from isothermal runs is in agreement with that determined for other elements for which an interstitial diffusion mechanism in iron has been established. At the interface between carbon and Fe the growth of a reaction rim was often observed. Time series experiments were therefore performed, to investigate the growth kinetics of iron carbide (Fe3C). Results will be used to 1) determine a model for the storage of C in metallic phases in the Earth's interior and 2) provide an experimental constraint on the formation of carbide phases during subduction, with implications for the deep carbon cycle and isotopic fractionation.

  7. The Kinetic Theory of Growth of Zr-Sn Diffusion Layers on Zr55 Cu30 Al10 Ni5 Metallic Glass

    NASA Astrophysics Data System (ADS)

    Chai, Kan; Lin, Tie-Song; He, Peng; Sun, Jian-Fei

    2014-11-01

    The growth kinetics of the intermetallic compound layer between molten pure Sn and Zr55 Cu30 Al10 Ni5 bulk metallic glass (BMG) is mainly controlled by the diffusion mechanism at stage I at which the value of the time exponent is approximately 1/2, also there is unusual or unique stage II whose time exponent of the growth is suppressed to 1/3. It is deduced that phase transition such as nucleation, coalescence occurring in the vicinity of the interface of the diffusion layer within the BMG and the average size growing as one-third power of time, called the Lifshitz—Slezov law. A more elegant means of attack is based upon the Fokker—Planck approach, which permits us to calculate directly the probability of the distribution of steady-state thickness fluctuations. Physical implications of the analytical results also give the one-third power of time of distance scale. The transmission of Sn particles through a disorder system of the BMG, scattered by the local fluctuation levels, is the source of the time exponent from 1/2 to 1/3 as a macroscopic cumulative effect.

  8. International Journal of Thermophysica, Vol. 19, No. 2, 1998 Pyroelectric Thermal-Wave Resonant Cavity

    E-print Network

    Mandelis, Andreas

    Cavity: A Precision Thermal Diffusivity Sensor for Gases and Vapors1 J. Shen,2 A. Mandelis,2 3 and T, and helium) were measured using the cavity. Fourth-significant-figure precision was obtained. Ashe4 A novel thermal-wave resonant cavity (TWRC) was constructed and used for thermophysical

  9. LHC Beam Diffusion Dependence on RF Noise: Models And Measurements

    SciTech Connect

    Mastorides, T.; /SLAC; Rivetta, C.; /SLAC; Fox, J.D.; /SLAC; Van Winkle, D.; /SLAC; Baudrenghien, P.; /CERN; Butterworth, A.; /CERN; Molendijk, J.; /CERN; ,

    2010-09-14

    Radio Frequency (RF) accelerating system noise and non-idealities can have detrimental impact on the LHC performance through longitudinal motion and longitudinal emittance growth. A theoretical formalism has been developed to relate the beam and RF loop dynamics with the bunch length growth [1]. Measurements were conducted at LHC to validate the formalism, determine the performance limiting RF components, and provide the foundation for beam diffusion estimates for higher energies and intensities. A brief summary of these results is presented in this work. During a long store, the relation between the energy lost to synchrotron radiation and the noise injected to the beam by the RF accelerating voltage determines the growth of the bunch energy spread and longitudinal emittance. Since the proton synchrotron radiation in the LHC is very low, the beam diffusion is extremely sensitive to RF perturbations. The theoretical formalism presented in [1], suggests that the noise experienced by the beam depends on the cavity phase noise power spectrum, filtered by the beam transfer function, and aliased due to the periodic sampling of the accelerating voltage signal V{sub c}. Additionally, the dependence of the RF accelerating cavity noise spectrum on the Low Level RF (LLRF) configurations has been predicted using time-domain simulations and models [2]. In this work, initial measurements at the LHC supporting the above theoretical formalism and simulation predictions are presented.

  10. Investigation of Cu(In,Ga)Se{sub 2} polycrystalline growth: Ga diffusion and surface morphology evolution

    SciTech Connect

    Han, Jun-feng, E-mail: junfeng.han@cnrs-imn.fr [Department of Physics, Peking University, Beijing 100871 (China); Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, UMR CNRS 6502, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France); Liao, Cheng [Department of Physics, Peking University, Beijing 100871 (China); Chengdu Green Energy and Green Manufacturing Technology R and D Center, Chengdu, Sichuan Province 601207 (China); Jiang, Tao; Xie, Hua-mu; Zhao, Kui [Department of Physics, Peking University, Beijing 100871 (China)

    2014-01-01

    Graphical abstract: - Highlights: • Ga diffusion in CIGS absorption layer after annealing treatment. • Phenomenon of surface reconstruction after annealing treatment. • Understand selenium effect on CIGS annealing process. • Explain the kinetic of Ga diffusion and MoSe{sub 2} formation. - Abstract: We report a study of selenization and annealing treatment of copper indium gallium selenide (CIGS) film. Morphologies and composition of surface and cross section were observed by scanning electron microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS). X-ray diffraction (XRD) and Raman spectra were used to investigate film structure. Depth profiles of element distributions were detected by Auger electron spectroscopy (AES). A double-layer structure was formed in the film by selenizing metallic precursor at 450 °C. Further annealing at 600 °C in pure argon enhanced gallium diffusion from the bottom to the top of the film, while additional selenium in the annealing had a negative effect. A MoSe{sub 2} layer was detected between CIGS and Mo layers with annealing in additional Se. The annealing treatment also significantly modified the film surface morphology. A large amount of triangular and polygon shaped islands were observed by SEM. That might be due to different nucleation kinetics for different crystal facets.

  11. Precision measurements of binary and multicomponent diffusion coefficients in protein solutions relevant to crystal growth: Lysozyme chloride in water and aqueous NaCl at pH 4.5 and 25°C

    Microsoft Academic Search

    John G. Albright; Onofrio Annunziata; Donald G. Miller; Luigi Paduano; Arne J. Pearlstein

    1999-01-01

    Accurate models of protein diffusion are important in a number of applications, including liquid-liquid phase separation and growth of protein crystals for X-ray diffraction studies. In concentrated multicomponent protein systems, significant deviations from pseudobinary behavior can be expected. Rayleigh interferometry is used to measure the four elements (D{sub if}){sub v} of the ternary diffusion coefficient matrix for the extensively investigated

  12. Over-expression of Thioredoxin-1 mediates growth, survival, and chemoresistance and is a druggable target in diffuse large B-cell lymphoma

    PubMed Central

    Li, Changping; Thompson, Michael A.; Tamayo, Archito T.; Zuo, Zhuang; Lee, John; Vega, Francisco; Ford, Richard J.; Pham, Lan V.

    2012-01-01

    Diffuse Large B cell lymphomas (DLBCL) are the most prevalent of the non-Hodgkin lymphomas and are currently initially treated fairly successfully, but frequently relapse as refractory disease, resulting in poor salvage therapy options and short survival. The greatest challenge in improving survival of DLBCL patients is overcoming chemo-resistance, whose basis is poorly understood. Among the potential mediators of DLBCL chemo-resistance is the thioredxoin (Trx) family, primarily because Trx family members play critical roles in the regulation of cellular redox homeostasis, and recent studies have indicated that dysregulated redox homeostasis also plays a key role in chemoresistance. In this study, we showed that most of the DLBCL-derived cell lines and primary DLBCL cells express higher basal levels of Trx-1 than normal B cells and that Trx-1 expression level is associated with decreased patients survival. Our functional studies showed that inhibition of Trx-1 by small interfering RNA or a Trx-1 inhibitor (PX-12) inhibited DLBCL cell growth, clonogenicity, and also sensitized DLBCL cells to doxorubicin-induced cell growth inhibition in vitro. These results indicate that Trx-1 plays a key role in cell growth and survival, as well as chemoresistance, and is a potential target to overcome drug resistance in relapsed/refractory DLBCL. PMID:22447839

  13. All about Cavities

    MedlinePLUS

    All About Cavities What's in Your Mouth? How Your Teeth Decay Types of Decay Preventing Cavities What's ... candy and ice cream we're talking about. All carbohydrate foods eventually break down into simple sugars. ...

  14. Real-time detection of epidermal growth factor receptor expression in fresh oral cavity biopsies using a molecular-specific contrast agent

    Microsoft Academic Search

    Elizabeth R. Hsu; Ann M. Gillenwater; M. Qasim Hasan; Michelle D. Williams; Adel K. El-Naggar; Rebecca R. Richards-Kortum

    2006-01-01

    Early diagnosis of individuals with high risk of developing head and neck squamous carcinoma should lead to decreased morbidity and increased survival. To aid in noninvasive early detection of oral neoplasia in vivo, we have developed a molecular-specific fluo- rescent contrast agent, consisting of a far-red fluorescent dye coupled to a monoclonal antibody targeted against the epidermal growth factor receptor.

  15. Analysis of Interactions between the Epidermal Growth Factor Receptor and Soluble Ligands on the Basis of Single-Molecule Diffusivity in the Membrane of Living Cells.

    PubMed

    Kim, Do-Hyeon; Zhou, Kai; Kim, Dong-Kyun; Park, Soyeon; Noh, Jungeun; Kwon, Yonghoon; Kim, Dayea; Song, Nam Woong; Lee, Jong-Bong; Suh, Pann-Ghill; Lee, Nam Ki; Ryu, Sung Ho

    2015-06-01

    We present a single-molecule diffusional-mobility-shift assay (smDIMSA) for analyzing the interactions between membrane and water-soluble proteins in the crowded membrane of living cells. We found that ligand-receptor interactions decreased the diffusional mobility of ErbB receptors and ?-adrenergic receptors, as determined by single-particle tracking with super-resolution microscopy. The shift in diffusional mobility was sensitive to the size of the water-soluble binders that ranged from a few tens of kilodaltons to several hundred kilodaltons. This technique was used to quantitatively analyze the dissociation constant and the cooperativity of antibody interactions with the epidermal growth factor receptor and its mutants. smDIMSA enables the quantitative investigation of previously undetected ligand-receptor interactions in the intact membrane of living cells on the basis of the diffusivity of single-molecule membrane proteins without ligand labeling. PMID:25940988

  16. Cavity turnover and equilibrium cavity densities in a cottonwood bottomland

    USGS Publications Warehouse

    Sedgwick, James A.; Knopf, Fritz L.

    1992-01-01

    A fundamental factor regulating the numbers of secondary cavity nesting (SCN) birds is the number of extant cavities available for nesting. The number of available cavities may be thought of as being in an approximate equilibrium maintained by a very rough balance between recruitment and loss of cavities. Based on estimates of cavity recruitment and loss, we ascertained equilibrium cavity densities in a mature plains cottonwood (Populus sargentii) bottomland along the South Platte River in northeastern Colorado. Annual cavity recruitment, derived from density estimates of primary cavity nesting (PCN) birds and cavity excavation rates, was estimated to be 71-86 new cavities excavated/100 ha. Of 180 active cavities of 11 species of cavity-nesting birds found in 1985 and 1986, 83 were no longer usable by 1990, giving an average instantaneous rate of cavity loss of r = -0.230. From these values of cavity recruitment and cavity loss, equilibrium cavity density along the South Platte is 238-289 cavities/100 ha. This range of equilibrium cavity density is only slightly above the minimum of 205 cavities/100 ha required by SCN's and suggests that cavity availability may be limiting SCN densities along the South Platte River. We submit that snag management alone does not adequately address SCN habitat needs, and that cavity management, expressed in terms of cavity turnover and cavity densities, may be more useful.

  17. International Technology Diffusion

    Microsoft Academic Search

    Wolfgang Keller

    2001-01-01

    I discuss the concept and empirical importance of international technology diffusion from the point of view of recent work on endogenous technological change. In this literature, technology is viewed as technological knowledge. I first review the major concepts, and how international technology diffusion relates to other factors affecting economic growth in open economies. The following main section of the paper

  18. Cancer of the oral cavity and oropharynx

    PubMed Central

    Zbaeren, Peter; Thoeny, Harriet C.

    2010-01-01

    Abstract Tumours in the oral cavity and oropharynx differ in presentation and prognosis and the detection of spread of tumour from one subsite to another is essential for the T-staging. This article reviews the anatomy and describes the pattern of spread of different cancers arising in the oral cavity and oropharynx; the imaging findings on computerized tomography and magnetic resonance imaging are also described. Brief mention is made on the role of newer imaging modalities such as [18F]fluorodeoxyglucose-positron emission tomography/computed tomography, perfusion studies and diffusion-weighted magnetic resonance imaging. PMID:20233682

  19. Cosmic ray modulation inside stellar wind cavities

    NASA Astrophysics Data System (ADS)

    Van Der Schyff, August; Scherer, Klaus; Ferreira, Stefan; Toit Strauss, Du

    In this study we attempt to model the cosmic ray flux in a stellar wind cavity of a O or B type star using a transport model based on stochastic differential equations. The required parameters, for example the coefficients of the diffusion tensor, are determined from an underlying magneto-hydrodynamical model. We discuss the transport in different astrospheric models with varying parameters for the transport coefficients. We will argue that large stellar wind cavities can act as sinks for the galactic cosmic ray flux.

  20. Growth advantage and enhanced toxicity of Escherichia coli adherent to tissue culture cells due to restricted diffusion of products secreted by the cells.

    PubMed Central

    Zafriri, D; Oron, Y; Eisenstein, B I; Ofek, I

    1987-01-01

    This study was undertaken to examine whether Escherichia coli adherent to tissue cells gain advantages over nonadherent bacteria due to their proximity to the cells. We used tissue culture cells and isogenic derivatives of a proline auxotrophic strain of E. coli that were fimbriated (Fim+) or nonfimbriated (Fim-), and were heat-labile enterotoxin producing (Tox+) or toxin nonproducing (Tox-). We found that the Fim+ bacteria; which were capable of adhering to tissue culture cells, initiated growth much sooner than did nonadherent Fim- bacteria; the adherent bacteria used tissue cell-derived proline, which was available at high concentrations only in the zone of bacterial adherence. Likewise, cyclic AMP secreted by adherent (Fim+) bacteria was maintained at high concentration on the tissue cell surfaces. As few as 2 X 10(5) adherent Fim+ Tox+ bacteria exert toxic activity upon Y1 adrenal cells, whereas toxin secreted in the medium by 6 X 10(6) Fim- Tox+ bacteria was undetectable. The results suggest that the growth advantage and enhanced toxicity of adherent E. coli is due to restricted diffusion of products secreted by the tissue culture and bacterial cells, respectively. Images PMID:3031133

  1. Megakaryocytic Potentiating Factor and Mature Mesothelin Stimulate the Growth of a Lung Cancer Cell Line in the Peritoneal Cavity of Mice

    PubMed Central

    Liu, Wenhai; Du, Xing; Alewine, Christine; Hassan, Raffit; Pastan, Ira

    2014-01-01

    The mesothelin (MSLN) gene encodes a 71 kilodalton (kDa) precursor protein that is processed into megakaryocytic potentiating factor (MPF), a 31 kDa protein that is secreted from the cell, and mature mesothelin (mMSLN), a 40 kDa cell surface protein. The mMSLN binds to CA125, an interaction that has been implicated in the intra-cavitary spread of mesothelioma and ovarian cancer. To better define the role of MPF and mMSLN, growth of the lung cancer cell line A549 was evaluated in immuno-deficient mice with inactivation of the Msln gene. We observed that Msln–/– mice xenografted with intraperitoneal A549 tumors survive significantly long than tumor-bearing Msln+/+ mice. When tumor-bearing Msln–/– mice are supplemented with recombinant MPF (and to a lesser extent mMSLN), most of this survival advantage is lost. These studies demonstrate that MPF and mMSLN have an important role in the growth of lung cancer cells in vivo and raise the possibility that inactivation of MPF may be a useful treatment for lung and other MSLN expressing cancers. PMID:25118887

  2. Electromagnetic SCRF Cavity Tuner

    SciTech Connect

    Kashikhin, V.; Borissov, E.; Foster, G.W.; Makulski, A.; Pischalnikov, Y.; Khabiboulline, T.; /Fermilab

    2009-05-01

    A novel prototype of SCRF cavity tuner is being designed and tested at Fermilab. This is a superconducting C-type iron dominated magnet having a 10 mm gap, axial symmetry, and a 1 Tesla field. Inside the gap is mounted a superconducting coil capable of moving {+-} 1 mm and producing a longitudinal force up to {+-} 1.5 kN. The static force applied to the RF cavity flanges provides a long-term cavity geometry tuning to a nominal frequency. The same coil powered by fast AC current pulse delivers mechanical perturbation for fast cavity tuning. This fast mechanical perturbation could be used to compensate a dynamic RF cavity detuning caused by cavity Lorentz forces and microphonics. A special configuration of magnet system was designed and tested.

  3. Tungsten diffusion in silicon

    SciTech Connect

    De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B. [Aix-Marseille Université, IM2NP UMR 7334, Faculté des Sciences et Techniques, Campus de Saint-Jérôme, Avenue Escadrille Normandie Niemen - Case 142, F-13397 Marseille Cedex (France); Portavoce, A., E-mail: alain.portavoce@im2np.fr [CNRS, IM2NP UMR 7334, Faculté des Sciences et Techniques, Campus de Saint-Jérôme, Avenue Escadrille Normandie Niemen - Case 142, F-13397 Marseille Cedex (France); Grosjean, C. [STMicroelectronics, Rousset (France)

    2014-01-07

    Two doses (10{sup 13} and 10{sup 15}?cm{sup ?2}) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960?°C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%–0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.

  4. International Journal of Thermophysics, Vol. 17, No. 6, 1996 Thermal-Wave Resonant-Cavity Measurements of the

    E-print Network

    Mandelis, Andreas

    used to measure the thermal dif- fusivity of the gas within the cavity with a high precision for measuring the thermal diffusivity of room air within the cavity, in terms of precision of measurementInternational Journal of Thermophysics, Vol. 17, No. 6, 1996 Thermal-Wave Resonant-Cavity

  5. Cavity enhanced terahertz modulation

    SciTech Connect

    Born, N., E-mail: norman.born@physik.uni-marburg.de [College of Optical Sciences, University of Arizona, 1630 E University Boulevard, Tucson, Arizona 85721 (United States); Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany); Scheller, M.; Moloney, J. V. [College of Optical Sciences, University of Arizona, 1630 E University Boulevard, Tucson, Arizona 85721 (United States)] [College of Optical Sciences, University of Arizona, 1630 E University Boulevard, Tucson, Arizona 85721 (United States); Koch, M. [Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany)] [Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany)

    2014-03-10

    We present a versatile concept for all optical terahertz (THz) amplitude modulators based on a Fabry-Pérot semiconductor cavity design. Employing the high reflectivity of two parallel meta-surfaces allows for trapping selected THz photons within the cavity and thus only a weak optical modulation of the semiconductor absorbance is required to significantly damp the field within the cavity. The optical switching yields to modulation depths of more than 90% with insertion efficiencies of 80%.

  6. Growth kinetics of MgSiO3 perovskite reaction rim between stishovite and periclase up to 50 GPa and its implication for grain boundary diffusivity in the lower mantle

    NASA Astrophysics Data System (ADS)

    Nishi, Masayuki; Nishihara, Yu; Irifune, Tetsuo

    2013-09-01

    The growth rate of MgSiO3 perovskite reaction rims between periclase and stishovite was investigated at 24-50 GPa and 1650-2150 K using a Kawai-type high-pressure apparatus. The textural observations of the recovered samples and rim growth kinetic data revealed that the reaction is controlled by coupled grain boundary diffusion of MgO and grain coarsening in the perovskite reaction layer. Assuming a high diffusivity of O compared with Mg, the grain boundary diffusivity of Mg in the perovskite was determined to be ?DgbMg[m/s]=10-15.1exp{-[176,000+(P-24)×3.8×103]/RT}, which is ˜3-5 orders of magnitude faster than that of Si. We found that the bulk diffusivity of Mg in polycrystalline perovskite is affected by the grain boundary when we consider the possible grain sizes and temperatures in the lower mantle. Accordingly, grain boundary diffusion in perovskite may be an effective mechanism for chemical transportation of divalent cations in the lower mantle.

  7. Optically measuring interior cavities

    DOEpatents

    Stone, Gary Franklin (Livermore, CA)

    2008-12-21

    A method of measuring the three-dimensional volume or perimeter shape of an interior cavity includes the steps of collecting a first optical slice of data that represents a partial volume or perimeter shape of the interior cavity, collecting additional optical slices of data that represents a partial volume or perimeter shape of the interior cavity, and combining the first optical slice of data and the additional optical slices of data to calculate of the three-dimensional volume or perimeter shape of the interior cavity.

  8. Protein kinase CK2 is widely expressed in follicular, Burkitt and diffuse large B-cell lymphomas and propels malignant B-cell growth

    PubMed Central

    Agostinelli, Claudio; Fuligni, Fabio; Benvenuti, Pietro; Mandato, Elisa; Casellato, Alessandro; Rugge, Massimo; Semenzato, Gianpietro; Pileri, Stefano A.

    2015-01-01

    Serine-threonine kinase CK2 is highly expressed and pivotal for survival and proliferation in multiple myeloma, chronic lymphocytic leukemia and mantle cell lymphoma. Here, we investigated the expression of ? catalytic and ? regulatory CK2 subunits by immunohistochemistry in 57 follicular (FL), 18 Burkitt (BL), 52 diffuse large B-cell (DLBCL) non-Hodgkin lymphomas (NHL) and in normal reactive follicles. In silico evaluation of available Gene Expression Profile (GEP) data sets from patients and Western blot (WB) analysis in NHL cell-lines were also performed. Moreover, the novel, clinical-grade, ATP-competitive CK2-inhibitor CX-4945 (Silmitasertib) was assayed on lymphoma cells. CK2 was detected in 98.4% of cases with a trend towards a stronger CK2? immunostain in BL compared to FL and DLBCL. No significant differences were observed between Germinal Center B (GCB) and non-GCB DLBCL types. GEP data and WB confirmed elevated CK2 mRNA and protein levels as well as active phosphorylation of specific targets in NHL cells. CX-4945 caused a dose-dependent growth-arresting effect on GCB, non-GCB DLBCL and BL cell-lines and it efficiently shut off phosphorylation of NF-?B RelA and CDC37 on CK2 target sites. Thus, CK2 is highly expressed and could represent a suitable therapeutic target in BL, FL and DLBCL NHL. PMID:25788269

  9. Suppression of Cavity-Driven Flow Separation in a Simulated Mixed Compression Inlet

    NASA Technical Reports Server (NTRS)

    Wendt, Bruce J.

    2000-01-01

    A test facility designed to simulate a bifurcated subsonic diffuser operating within a mixed compression inlet is described. The subsonic diffuser in this facility modeled a bypass cavity feature often used in mixed compression inlets for engine flow matching and normal shock control. A bypass cavity-driven flow separation was seen to occur in the subsonic diffuser without applied flow control. Flow control in the form of vortex generators and/or a partitioned bypass cavity cover plate were used to eliminate this flow separation, providing a 2% increase in area-averaged total pressure recovery, and a 70% reduction in circumferential distortion intensity.

  10. Passivated niobium cavities

    DOEpatents

    Myneni, Ganapati Rao (Yorktown, VA); Hjorvarsson, Bjorgvin (Lagga Arby, SE); Ciovati, Gianluigi (Newport News, VA)

    2006-12-19

    A niobium cavity exhibiting high quality factors at high gradients is provided by treating a niobium cavity through a process comprising: 1) removing surface oxides by plasma etching or a similar process; 2) removing hydrogen or other gases absorbed in the bulk niobium by high temperature treatment of the cavity under ultra high vacuum to achieve hydrogen outgassing; and 3) assuring the long term chemical stability of the niobium cavity by applying a passivating layer of a superconducting material having a superconducting transition temperature higher than niobium thereby reducing losses from electron (cooper pair) scattering in the near surface region of the interior of the niobium cavity. According to a preferred embodiment, the passivating layer comprises niobium nitride (NbN) applied by reactive sputtering.

  11. Diffusion of water submonolayers on hydrophilic surfaces.

    PubMed

    Park, Jae Hyun; Aluru, N R

    2008-12-22

    In this letter, we investigate using molecular dynamics simulations the diffusion of water submonolayers on hydrophilic surfaces. In contrast to a strong hydrophilic Ag surface, on a weak hydrophilic Pb surface, the diffusion coefficient is remarkably enhanced at a critical surface coverage and a Lambda-shape anomaly with surface coverage is observed, i.e., the diffusion coefficient increases with the increase in surface coverage until a critical surface coverage, beyond which the diffusion coefficient decreases. We explain the anomalous diffusion of water on hydrophilic surfaces by a detailed understanding of molecular cavities and monolayer tail contributing to three-dimensional hydrogen bonding. PMID:19529784

  12. Lithium diffusion at Si-C interfaces in silicon-graphene composites

    SciTech Connect

    Odbadrakh, Khorgolkhuu [Joint Institute for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); McNutt, N. W. [Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States); Nicholson, D. M. [Computational Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); Department of Physics, University of North Carolina, Asheville, North Carolina 28804 (United States); Rios, O. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); Keffer, D. J. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)

    2014-08-04

    Models of intercalated Li and its diffusion in Si-Graphene interfaces are investigated using density functional theory. Results suggest that the presence of interfaces alters the energetics of Li binding and diffusion significantly compared to bare Si or Graphene surfaces. Our results show that cavities along reconstructed Si surface provide diffusion paths for Li. Diffusion barriers calculated along these cavities are significantly lower than penetration barriers to bulk Si. Interaction with Si surface results in graphene defects, creating Li diffusion paths that are confined along the cavities but have still lower barrier than in bulk Si.

  13. Lithium diffusion at Si-C interfaces in Silicon-Graphene composites

    SciTech Connect

    Odbadrakh, Khorgolkhuu [ORNL; McNutt, Nichiolas William [University of Tennessee, Knoxville (UTK); Nicholson, Donald M. [Oak Ridge National Laboratory (ORNL); Rios, Orlando [ORNL; Keffer, David J. [University of Tennessee, Knoxville (UTK)

    2014-01-01

    Models of intercalated Li and its diffusion in Si-Graphene interfaces are investigated using Density Functional Theory. Results suggest that the presence of interfaces alters the energetics of Li binding and diffusion significantly compared to bare Si or Graphene surfaces. Our results show that cavities along reconstructed Si surface provide diffusion paths for Li. Diffusion barriers calculated along these cavities are significantly lower than penetration barriers to bulk Si. Interaction with Si surface results in graphene defects, creating Li diffusion paths that are confined along the cavities but have still lower barrier than in bulk Si.

  14. Digital Cavity Resonance Monitor, alternative method of measuring cavity microphonics

    Microsoft Academic Search

    Tomasz Plawski; G. Davis; Hai Dong; J. Hovater; John Musson; Thomas Powers

    2005-01-01

    As is well known, mechanical vibration or microphonics in a cryomodule causes the cavity resonance frequency to change at the vibration frequency. One way to measure the cavity microphonics is to drive the cavity with a Phase Locked Loop. Measurement of the instantaneous frequency or PLL error signal provides information about the cavity microphonic frequencies. Although the PLL error signal

  15. Hydroforming of elliptical cavities

    NASA Astrophysics Data System (ADS)

    Singer, W.; Singer, X.; Jelezov, I.; Kneisel, P.

    2015-02-01

    Activities of the past several years in developing the technique of forming seamless (weldless) cavity cells by hydroforming are summarized. An overview of the technique developed at DESY for the fabrication of single cells and multicells of the TESLA cavity shape is given and the major rf results are presented. The forming is performed by expanding a seamless tube with internal water pressure while simultaneously swaging it axially. Prior to the expansion the tube is necked at the iris area and at the ends. Tube radii and axial displacements are computer controlled during the forming process in accordance with results of finite element method simulations for necking and expansion using the experimentally obtained strain-stress relationship of tube material. In cooperation with industry different methods of niobium seamless tube production have been explored. The most appropriate and successful method is a combination of spinning or deep drawing with flow forming. Several single-cell niobium cavities of the 1.3 GHz TESLA shape were produced by hydroforming. They reached accelerating gradients Eacc up to 35 MV /m after buffered chemical polishing (BCP) and up to 42 MV /m after electropolishing (EP). More recent work concentrated on fabrication and testing of multicell and nine-cell cavities. Several seamless two- and three-cell units were explored. Accelerating gradients Eacc of 30 - 35 MV /m were measured after BCP and Eacc up to 40 MV /m were reached after EP. Nine-cell niobium cavities combining three three-cell units were completed at the company E. Zanon. These cavities reached accelerating gradients of Eacc=30 - 35 MV /m . One cavity is successfully integrated in an XFEL cryomodule and is used in the operation of the FLASH linear accelerator at DESY. Additionally the fabrication of bimetallic single-cell and multicell NbCu cavities by hydroforming was successfully developed. Several NbCu clad single-cell and double-cell cavities of the TESLA shape have been fabricated. The clad seamless tubes were produced using hot bonding or explosive bonding and subsequent flow forming. The thicknesses of Nb and Cu layers in the tube wall are about 1 and 3 mm respectively. The rf performance of the best NbCu clad cavities is similar to that of bulk Nb cavities. The highest accelerating gradient achieved was 40 MV /m . The advantages and disadvantages of hydroformed cavities are discussed in this paper.

  16. Hydroforming of elliptical cavities

    DOE PAGESBeta

    Singer, W.; Singer, X.; Jelezov, I.; Kneisel, Peter

    2015-02-01

    Activities of the past several years in developing the technique of forming seamless (weldless) cavity cells by hydroforming are summarized. An overview of the technique developed at DESY for the fabrication of single cells and multicells of the TESLA cavity shape is given and the major rf results are presented. The forming is performed by expanding a seamless tube with internal water pressure while simultaneously swaging it axially. Prior to the expansion the tube is necked at the iris area and at the ends. Tube radii and axial displacements are computer controlled during the forming process in accordance with resultsmore »of finite element method simulations for necking and expansion using the experimentally obtained strain-stress relationship of tube material. In cooperation with industry different methods of niobium seamless tube production have been explored. The most appropriate and successful method is a combination of spinning or deep drawing with flow forming. Several single-cell niobium cavities of the 1.3 GHz TESLA shape were produced by hydroforming. They reached accelerating gradients Eacc up to 35 MV/m after buffered chemical polishing (BCP) and up to 42 MV/m after electropolishing (EP). More recent work concentrated on fabrication and testing of multicell and nine-cell cavities. Several seamless two- and three-cell units were explored. Accelerating gradients Eacc of 30–35 MV/m were measured after BCP and Eacc up to 40 MV/m were reached after EP. Nine-cell niobium cavities combining three three-cell units were completed at the company E. Zanon. These cavities reached accelerating gradients of Eacc = 30–35 MV/m. One cavity is successfully integrated in an XFEL cryomodule and is used in the operation of the FLASH linear accelerator at DESY. Additionally the fabrication of bimetallic single-cell and multicell NbCu cavities by hydroforming was successfully developed. Several NbCu clad single-cell and double-cell cavities of the TESLA shape have been fabricated. The clad seamless tubes were produced using hot bonding or explosive bonding and subsequent flow forming. The thicknesses of Nb and Cu layers in the tube wall are about 1 and 3 mm respectively. The rf performance of the best NbCu clad cavities is similar to that of bulk Nb cavities. The highest accelerating gradient achieved was 40 MV/m. The advantages and disadvantages of hydroformed cavities are discussed in this paper.« less

  17. Enhanced fluorescence diffuse optical tomography with indocyanine green-encapsulating liposomes targeted to receptors for vascular endothelial growth factor in tumor vasculature

    NASA Astrophysics Data System (ADS)

    Zanganeh, Saeid; Xu, Yan; Hamby, Carl V.; Backer, Marina V.; Backer, Joseph M.; Zhu, Quing

    2013-12-01

    To develop an indocyanine green (ICG) tracer with slower clearance kinetics, we explored ICG-encapsulating liposomes (Lip) in three different formulations: untargeted (Lip/ICG), targeted to vascular endothelial growth factor (VEGF) receptors (scVEGF-Lip/ICG) by the receptor-binding moiety single-chain VEGF (scVEGF), or decorated with inactivated scVEGF (inactive-Lip/ICG) that does not bind to VEGF receptors. Experiments were conducted with tumor-bearing mice that were placed in a scattering medium with tumors located at imaging depths of either 1.5 or 2.0 cm. Near-infrared fluorescence diffuse optical tomography that provides depth-resolved spatial distributions of fluorescence in tumor was used for the detection of postinjection fluorescent signals. All liposome-based tracers, as well as free ICG, were injected intravenously into mice in the amounts corresponding to 5 nmol of ICG/mouse, and the kinetics of increase and decrease of fluorescent signals in tumors were monitored. A signal from free ICG reached maximum at 15-min postinjection and then rapidly declined with t of ˜20 min. The signals from untargeted Lip/ICG and inactive-Lip/ICG also reached maximum at 15-min postinjection, however, declined somewhat slower than free ICG with t of ˜30 min. By contrast, a signal from targeted scVEGF-Lip/ICG grew slower than that of all other tracers, reaching maximum at 30-min postinjection and declined much slower than that of other tracers with t of ˜90 min, providing a more extended observation window. Higher scVEGF-Lip/ICG tumor accumulation was further confirmed by the analysis of fluorescence on cryosections of tumors that were harvested from animals at 400 min after injection with different tracers.

  18. Enhanced fluorescence diffuse optical tomography with indocyanine green-encapsulating liposomes targeted to receptors for vascular endothelial growth factor in tumor vasculature

    PubMed Central

    Zanganeh, Saeid; Xu, Yan; Hamby, Carl V.; Backer, Marina V.; Backer, Joseph M.; Zhu, Quing

    2013-01-01

    Abstract. To develop an indocyanine green (ICG) tracer with slower clearance kinetics, we explored ICG-encapsulating liposomes (Lip) in three different formulations: untargeted (Lip/ICG), targeted to vascular endothelial growth factor (VEGF) receptors (scVEGF-Lip/ICG) by the receptor-binding moiety single-chain VEGF (scVEGF), or decorated with inactivated scVEGF (inactive-Lip/ICG) that does not bind to VEGF receptors. Experiments were conducted with tumor-bearing mice that were placed in a scattering medium with tumors located at imaging depths of either 1.5 or 2.0 cm. Near-infrared fluorescence diffuse optical tomography that provides depth-resolved spatial distributions of fluorescence in tumor was used for the detection of postinjection fluorescent signals. All liposome-based tracers, as well as free ICG, were injected intravenously into mice in the amounts corresponding to 5 nmol of ICG/mouse, and the kinetics of increase and decrease of fluorescent signals in tumors were monitored. A signal from free ICG reached maximum at 15-min postinjection and then rapidly declined with t1/2 of ?20??min. The signals from untargeted Lip/ICG and inactive-Lip/ICG also reached maximum at 15-min postinjection, however, declined somewhat slower than free ICG with t1/2 of ?30??min. By contrast, a signal from targeted scVEGF-Lip/ICG grew slower than that of all other tracers, reaching maximum at 30-min postinjection and declined much slower than that of other tracers with t1/2 of ?90??min, providing a more extended observation window. Higher scVEGF-Lip/ICG tumor accumulation was further confirmed by the analysis of fluorescence on cryosections of tumors that were harvested from animals at 400 min after injection with different tracers. PMID:24346856

  19. Formation of Co–Si intermetallics in bulk diffusion couples. Part I. Growth kinetics and mobilities of species in the silicide phases

    Microsoft Academic Search

    M. J. H van Dal; D. G. G. M Huibers; A. A Kodentsov; F. J. J van Loo

    2001-01-01

    Diffusion couples, in which one single-phased layer of Co-silicide is growing from its saturated adjacent phases, were employed to study diffusion properties of the Co–Si intermetallics over the temperature range 914–1217°C. The position of the Kirkendall marker plane inside the reaction zones revealed that in this temperature interval Co is by far the fastest diffusing element in the Co2Si-intermetallic, the

  20. Calibration of the absorptance cavities for the spaceflight solar radiometer TIM

    E-print Network

    sensors in each instrument are hollow conical silver cavities with a cylindrical entrance extension and a diffuse black nickel phosphorous (NiP) interior that converts absorbed incident radiation to thermal

  1. Precision tunable resonant microwave cavity

    Microsoft Academic Search

    Shigeo Nakanishi; Frank S. Calco; August R. Scarpelli

    1987-01-01

    A tunable microwave cavity containing ionizable metallic vapor or gases and an apparatus for precisely positioning a microwave coupling tip in the cavity and for precisely adjusting at least one dimension of the cavity are disclosed. With this combined structure, resonance may be achieved with various types of ionizable gases. A coaxial probe extends into a microwave cavity through a

  2. Cavity optoelectromechanical regenerative amplification

    E-print Network

    Michael A. Taylor; Alex Szorkovszky; Joachim Knittel; Kwan H. Lee; Terry G. McRae; Warwick P. Bowen

    2012-06-29

    Cavity optoelectromechanical regenerative amplification is demonstrated. An optical cavity enhances mechanical transduction, allowing sensitive measurement even for heavy oscillators. A 27.3 MHz mechanical mode of a microtoroid was linewidth narrowed to 6.6\\pm1.4 mHz, 30 times smaller than previously achieved with radiation pressure driving in such a system. These results may have applications in areas such as ultrasensitive optomechanical mass spectroscopy.

  3. Signal generation mechanisms, intracavity-gas thermal-diffusivity temperature dependence, and absolute infrared emissivity measurements

    E-print Network

    Mandelis, Andreas

    the thermal diffusivities of gases with very high precision and resolution.2,3 The cavity consists of two, and absolute infrared emissivity measurements in a thermal-wave resonant cavity Jun Shen, Andreas Mandelis transfer mechanisms in a thermal-wave resonant cavity were explored theoretically and experimentally. Both

  4. Coupled resonator vertical cavity laser

    SciTech Connect

    Choquette, K.D.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.

    1998-01-01

    The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.

  5. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, Richard N. (Stanford, CA); Martin, Juergen (Jena-Wogau, DE); Paldus, Barbara A. (Stanford, CA); Xie, Jinchun (Sunnyvale, CA)

    1999-01-01

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS).

  6. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, R.N.; Martin, J.; Paldus, B.A.; Xie, J.

    1999-06-15

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS). 6 figs.

  7. Diffusion /Osmosis

    NSDL National Science Digital Library

    Jensen

    2007-11-26

    This project is use to review the concepts of diffusion and osmosis 1. Watch the tutorials on diffusion and osmosis. Take the online quiz at the end of each one. Diffusion Animation Osmosis Animation 2. Do the interactive lab on diffusion. Stop when you get to the calculating water potential section. Diffusion/Osmosis Interactive Demo 3. Play the Quia review games. Quia Games- matching/concetration Quia Jeopardy 4. Check out the Elodea leaf cells. Be able to ...

  8. Coupled Geomechanical Simulations of UCG Cavity Evolution

    SciTech Connect

    Morris, J P; Buscheck, T A; Hao, Y

    2009-07-13

    This paper presents recent work from an ongoing project to develop predictive tools for cavity/combustion-zone growth and to gain quantitative understanding of the processes and conditions (both natural and engineered) affecting underground coal gasification (UCG). In this paper we will focus upon the development of coupled geomechanical capabilities for simulating the evolution of the UCG cavity using discrete element methodologies. The Discrete Element Method (DEM) has unique advantages for facilitating the prediction of the mechanical response of fractured rock masses, such as cleated coal seams. In contrast with continuum approaches, the interfaces within the coal can be explicitly included and combinations of both elastic and plastic anisotropic response are simulated directly. Additionally, the DEM facilitates estimation of changes in hydraulic properties by providing estimates of changes in cleat aperture. Simulation of cavity evolution involves a range of coupled processes and the mechanical response of the host coal and adjoining rockmass plays a role in every stage of UCG operations. For example, cavity collapse during the burn has significant effect upon the rate of the burn itself. In the vicinity of the cavity, collapse and fracturing may result in enhanced hydraulic conductivity of the rock matrix in the coal and caprock above the burn chamber. Even far from the cavity, stresses due to subsidence may be sufficient to induce new fractures linking previously isolated aquifers. These mechanical processes are key in understanding the risk of unacceptable subsidence and the potential for groundwater contamination. These mechanical processes are inherently non-linear, involving significant inelastic response, especially in the region closest to the cavity. In addition, the response of the rock mass involves both continuum and discrete mechanical behavior. We have recently coupled the LDEC (Livermore Distinct Element Code) and NUFT (Non-isothermal Unsaturated Flow and Transport) codes to investigate the interaction between combustion, water influx and mechanical response. The modifications to NUFT are described in detail in a companion paper. This paper considers the extension of the LDEC code and the application of the coupled tool to the simulation of cavity growth and collapse. The distinct element technology incorporated into LDEC is ideally suited to simulation of the progressive failure of the cleated coal mass by permitting the simulation of individual planes of weakness. We will present details of the coupling approach and then demonstrate the capability through simulation of several test cases.

  9. Coupled Surface Diffusion and Motion by Mean Curvature from a Diffuse Interface Model

    E-print Network

    Novick-Cohen, Amy

    of binary alloys coupled motion by mean curvature and motion by surface diffusion occurs the coarseningCoupled Surface Diffusion and Motion by Mean Curvature from a Diffuse Interface Model Amy Novick growth, surface diffusion, theory. Abstract A degenerate Allen-Cahn/Cahn-Hilliard system which

  10. Cancer Stem Cells and Oral Cavity Cancer Metastasis

    Microsoft Academic Search

    Mark Prince

    \\u000a Oral cavity squamous cell carcinoma is a common malignancy with a high propensity for the development of metastasis. Even\\u000a early stage oral cavity tumors are frequently associated with metastasis to regional lymph nodes. Cancer stem cells have recently\\u000a been isolated from head and neck squamous cell cancer and represent the critical population of cancer cells responsible for\\u000a primary tumor growth.

  11. ISABELLE cavity gap assemblies

    SciTech Connect

    Plotkin, M

    1981-01-01

    In a storage ring, where beam lifetime is measured in hours, it is necessary to keep the longitudinal impedance, as seen by the beam, very low, even into the gigahertz region. This is necessary to prevent the excitation of longitudinal instabilities. These impedances are due to the resistive wall effect and any deviation from a smooth vacuum chamber such as at pick-up electrodes, vacuum pump stations, rf cavities, etc. At low frequencies, up to 10 to 20 MHz, the low impedance requirement for the cavities can be satisfied by designing the driving power amplifiers with a very low output impedance. For ISABELLE a method has been designed for building a network into the cavity accelerating gaps which will satisfy the impedance criteria to at least 1300 MHz. The maximum allowable impedance at any frequency, f, is given in the form Z/n where n = f/f/sub rotation/. For the ISABELLE accelerating cavity, operating at 235.5 KHz, Z/n must be less than 10 ohms. For the stacking cavity, operating at 4.45 MHz, Z/n < 1 ohm.

  12. Photonic Crystal Cavity Lasers

    NASA Astrophysics Data System (ADS)

    Gong, Yiyang; Ellis, Bryan; Vu?kovi?, Jelena

    Photonic laser sources have great potential in communication and lighting applications. Optical resonators reduce the lasing threshold by enhancing the light-matter interaction, increasing the efficiency and modulation rate. We explore the design, fabrication, and characterization of lasers based on photonic crystal (PC) cavities. We first describe the fundamentals of the PC cavity in one dimensional (1D) and two dimensional (2D) settings, and how cavity designs enable high quality factor, low mode volume resonators that facilitate high Purcell enhancements. Next, we show how such designs are implemented to fabricate low threshold lasers using quantum dot(QD) materials. Experimentally under optical injection, we are able to obtain lasing thresholds of microwatts at room temperature and cryogenic temperature, fitting the behavior of different lasers to rate equations. We also theoretically and experimentally characterize the time dynamics of the lasers at cryogenic temperature under modulated pumping, observing that the lasers can be modulated at 30 GHz. Finally, we explore novel approaches to electrically inject PC cavity devices using a lithographically defined lateral p-i-n junction, and demonstrate a lateral junction PC cavity light-emitting device.

  13. Pb-Zn liquid metal diffusion

    NASA Technical Reports Server (NTRS)

    Pond, R. B., Sr.; Winter, J. M., Jr.

    1988-01-01

    The Lead-Zinc binary equilibrium system is currently being investigated. Ground based studies of this system were performed to examine the possibility of obtaining a couple which, after diffusion, could be examined continuously along the diffusion axis by quantitative metallography to determine the extent of diffusion. The specimens were analyzed by X-ray fluorescence in the scanning electron microscope to provide exact information on the chemical composition gradient. Two diffusion experiments were run simultaneously in the multipurpose furnace, each in its own isothermal cavity. Two flight samples, two flight backup samples, and two flight space samples were generated.

  14. Diffusion Limited Aggregation

    NSDL National Science Digital Library

    David Joiner

    The Diffusion Limited Aggregation (DLA) algorithm models the growth of an object one particle at a time sticking in random places. This calculator computes DLA on a square, hexagonal, or octagonal lattice, and allows for the computation of fractal dimension by a box counting method.

  15. Precision tunable resonant microwave cavity

    NASA Technical Reports Server (NTRS)

    Nakanishi, Shigeo (inventor); Calco, Frank S. (inventor); Scarpelli, August R. (inventor)

    1987-01-01

    A tunable microwave cavity containing ionizable metallic vapor or gases and an apparatus for precisely positioning a microwave coupling tip in the cavity and for precisely adjusting at least one dimension of the cavity are disclosed. With this combined structure, resonance may be achieved with various types of ionizable gases. A coaxial probe extends into a microwave cavity through a tube. One end of the tube is retained in a spherical joint attached in the cavity wall. This allows the coaxial probe to be pivotally rotated. The coaxial probe is slideable within the tube thus allowing the probe to be extended toward or retracted from the center of the cavity.

  16. Video Toroid Cavity Imager

    DOEpatents

    Gerald, Rex E. II; Sanchez, Jairo; Rathke, Jerome W.

    2004-08-10

    A video toroid cavity imager for in situ measurement of electrochemical properties of an electrolytic material sample includes a cylindrical toroid cavity resonator containing the sample and employs NMR and video imaging for providing high-resolution spectral and visual information of molecular characteristics of the sample on a real-time basis. A large magnetic field is applied to the sample under controlled temperature and pressure conditions to simultaneously provide NMR spectroscopy and video imaging capabilities for investigating electrochemical transformations of materials or the evolution of long-range molecular aggregation during cooling of hydrocarbon melts. The video toroid cavity imager includes a miniature commercial video camera with an adjustable lens, a modified compression coin cell imager with a fiat circular principal detector element, and a sample mounted on a transparent circular glass disk, and provides NMR information as well as a video image of a sample, such as a polymer film, with micrometer resolution.

  17. Impact of mesophyll diffusion on estimated global land CO2 fertilization

    PubMed Central

    Sun, Ying; Gu, Lianhong; Dickinson, Robert E.; Norby, Richard J.; Pallardy, Stephen G.; Hoffman, Forrest M.

    2014-01-01

    In C3 plants, CO2 concentrations drop considerably along mesophyll diffusion pathways from substomatal cavities to chloroplasts where CO2 assimilation occurs. Global carbon cycle models have not explicitly represented this internal drawdown and therefore overestimate CO2 available for carboxylation and underestimate photosynthetic responsiveness to atmospheric CO2. An explicit consideration of mesophyll diffusion increases the modeled cumulative CO2 fertilization effect (CFE) for global gross primary production (GPP) from 915 to 1,057 PgC for the period of 1901–2010. This increase represents a 16% correction, which is large enough to explain the persistent overestimation of growth rates of historical atmospheric CO2 by Earth system models. Without this correction, the CFE for global GPP is underestimated by 0.05 PgC/y/ppm. This finding implies that the contemporary terrestrial biosphere is more CO2 limited than previously thought. PMID:25313079

  18. Impact of mesophyll diffusion on estimated global land CO2 fertilization.

    PubMed

    Sun, Ying; Gu, Lianhong; Dickinson, Robert E; Norby, Richard J; Pallardy, Stephen G; Hoffman, Forrest M

    2014-11-01

    In C3 plants, CO2 concentrations drop considerably along mesophyll diffusion pathways from substomatal cavities to chloroplasts where CO2 assimilation occurs. Global carbon cycle models have not explicitly represented this internal drawdown and therefore overestimate CO2 available for carboxylation and underestimate photosynthetic responsiveness to atmospheric CO2. An explicit consideration of mesophyll diffusion increases the modeled cumulative CO2 fertilization effect (CFE) for global gross primary production (GPP) from 915 to 1,057 PgC for the period of 1901-2010. This increase represents a 16% correction, which is large enough to explain the persistent overestimation of growth rates of historical atmospheric CO2 by Earth system models. Without this correction, the CFE for global GPP is underestimated by 0.05 PgC/y/ppm. This finding implies that the contemporary terrestrial biosphere is more CO2 limited than previously thought. PMID:25313079

  19. Between scylla and charybdis: hydrophobic graphene-guided water diffusion on hydrophilic substrates.

    PubMed

    Kim, Jin-Soo; Choi, Jin Sik; Lee, Mi Jung; Park, Bae Ho; Bukhvalov, Danil; Son, Young-Woo; Yoon, Duhee; Cheong, Hyeonsik; Yun, Jun-Nyeong; Jung, Yousung; Park, Jeong Young; Salmeron, Miquel

    2013-01-01

    The structure of water confined in nanometer-sized cavities is important because, at this scale, a large fraction of hydrogen bonds can be perturbed by interaction with the confining walls. Unusual fluidity properties can thus be expected in the narrow pores, leading to new phenomena like the enhanced fluidity reported in carbon nanotubes. Crystalline mica and amorphous silicon dioxide are hydrophilic substrates that strongly adsorb water. Graphene, on the other hand, interacts weakly with water. This presents the question as to what determines the structure and diffusivity of water when intercalated between hydrophilic substrates and hydrophobic graphene. Using atomic force microscopy, we have found that while the hydrophilic substrates determine the structure of water near its surface, graphene guides its diffusion, favouring growth of intercalated water domains along the C-C bond zigzag direction. Molecular dynamics and density functional calculations are provided to help understand the highly anisotropic water stripe patterns observed. PMID:23896759

  20. A colony-forming assay for human tumour xenografts using agar in diffusion chambers.

    PubMed Central

    Smith, I. E.; Courtenay, V. D.; Gordon, M. Y.

    1976-01-01

    A technique for growing colonies from single-cell suspensions of human tumour xenografts using agar in diffusion chambers is described. Modified Millipore diffusion chambers containing tumour cells in semi-solid agar-medium were implanted into the peritoneal cavity of pre-irradiated mice and provided standard culture conditions for the study of colony-forming cells. All 11 xenograft tumours so far studied produced colonies. The incubation period for colony growth ranged from 12 to 28 days and the plating efficiency ranged from 0-3% to 16% for different tumours, but both parameters were constant for each individual tumour. The reproducibility of the system provides a colony-forming assay which can be used to study the effects of irradiation and cytotoxic drugs on human tumour clonogenic cells and may therefore have some advantages over similar assays based on experimental animal tumours. Images Fig. 1(b) Fig. 1(c) Fig. 1(a) PMID:999782

  1. Cavity Cooling with a Hot Cavity Vladan Vuletic

    E-print Network

    Vuletic, Vladan

    Cavity Cooling with a Hot Cavity Vladan Vuleti´c 1 Introduction Whereas from a classical point precision spectroscopy of anti-hydrogen, implement magnetic motors to move Bose-Einstein condensates to the atomic level structure [9], this cavity cooling technique holds promise for generalizing laser cooling

  2. Broadband cavity electromagnetically induced transparency

    SciTech Connect

    Wei Xiaogang [Department of Physics, Florida International University, Miami, Florida 33199 (United States); College of Physics, Jilin University, Changchun 130023 (China); Wang Yanhua [Department of Physics, Florida International University, Miami, Florida 33199 (United States); College of Physics and Electronics, Shanxi University, Taiyuan 030006 (China); Zhang Jiepeng [Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Physics Division P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States); Zhu Yifu [Department of Physics, Florida International University, Miami, Florida 33199 (United States)

    2011-10-15

    Cavity electromagnetically induced transparency (EIT) is created in a three-level atomic system confined in a cavity and coupled to a free-space control laser and is manifested as a narrow transmission peak of a probe laser coupled into the cavity mode and tuned to the two-photon Raman resonance with the control laser. Cavity EIT can be observed with a control laser detuned from the atomic transition frequency in a range limited by the vacuum Rabi splitting of two cavity-atom normal modes. This leads to the broadband cavity EIT obtained in the coupled-cavity-atom system with a free-space, broadband control laser. We report an experimental observation of broadband cavity EIT in cold Rb atoms with a frequency-modulated control laser and discuss its application in multichannel and multifrequency light memory.

  3. Progress towards cavity induced transparency

    E-print Network

    Li, Tracy (Tracy Yang)

    2010-01-01

    Inspired by electromagnetically induced transparency (EIT), cavity induced transparency (CIT) uses a cavity rather than a laser to couple a ground state with the excited state of a three-level system. In this thesis, I ...

  4. Photopyroelectric method using a thermal wave resonator cavity for detection of phase transitions in agar

    Microsoft Academic Search

    R. Medina-Esquivel; J. M. Yanez-Limon; Juan J. Alvarado-Gil

    2005-01-01

    In this work, the Photopyroelectric (PPE) technique using a Thermal Wave Resonator Cavity (TWRC) is used to measure the thermal diffusivity of agar. We, determine the liquid to gel phase transition temperature as a function of agar concentration, detecting a shift in that temperature. As agar concentration decreases, the phase transition temperatures get lower. The thermal diffusivity of agar as

  5. Effects of surface diffusion on high temperature selective emitters

    DOE PAGESBeta

    Peykov, Daniel; Yeng, Yi Xiang; Celanovic, Ivan; Joannopoulos, John D.; Schuh, Christopher A.

    2015-01-01

    Using morphological and optical simulations of 1D tantalum photonic crystals at 1200K, surface diffusion was determined to gradually reduce the efficiency of selective emitters. This was attributed to shifting resonance peaks and declining emissivity caused by changes to the cavity dimensions and the aperture width. Decreasing the structure’s curvature through larger periods and smaller cavity widths, as well as generating smoother transitions in curvature through the introduction of rounded cavities, was found to alleviate this degradation. An optimized structure, that shows both high efficiency selective emissivity and resistance to surface diffusion, was presented.

  6. Effects of surface diffusion on high temperature selective emitters.

    PubMed

    Peykov, Daniel; Yeng, Yi Xiang; Celanovic, Ivan; Joannopoulos, John D; Schuh, Christopher A

    2015-04-20

    Using morphological and optical simulations of 1D tantalum photonic crystals at 1200K, surface diffusion was determined to gradually reduce the efficiency of selective emitters. This was attributed to shifting resonance peaks and declining emissivity caused by changes to the cavity dimensions and the aperture width. Decreasing the structure's curvature through larger periods and smaller cavity widths, as well as generating smoother transitions in curvature through the introduction of rounded cavities, was found to alleviate this degradation. An optimized structure, that shows both high efficiency selective emissivity and resistance to surface diffusion, was presented. PMID:25969039

  7. Hollow waveguide cavity ringdown spectroscopy

    NASA Technical Reports Server (NTRS)

    Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

    2012-01-01

    Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

  8. Elemental diffusion during the droplet epitaxy growth of In(Ga)As/GaAs(001) quantum dots by metal-organic chemical vapor deposition

    SciTech Connect

    Chen, Z. B.; Chen, B.; Wang, Y. B.; Liao, X. Z., E-mail: xiaozhou.liao@sydney.edu.au [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Lei, W. [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, Perth, WA 6009 (Australia); Tan, H. H.; Jagadish, C. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Zou, J. [Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, QLD 4072 (Australia); Ringer, S. P. [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia)

    2014-01-13

    Droplet epitaxy is an important method to produce epitaxial semiconductor quantum dots (QDs). Droplet epitaxy of III-V QDs comprises group III elemental droplet deposition and the droplet crystallization through the introduction of group V elements. Here, we report that, in the droplet epitaxy of InAs/GaAs(001) QDs using metal-organic chemical vapor deposition, significant elemental diffusion from the substrate to In droplets occurs, resulting in the formation of In(Ga)As crystals, before As flux is provided. The supply of As flux suppresses the further elemental diffusion from the substrate and promotes surface migration, leading to large island formation with a low island density.

  9. Long Wavelength Multiple Resonant Cavities RCE Photodetectors on GaAs Substrates

    Microsoft Academic Search

    Xiaofeng Duan; Yongqing Huang; Xiaomin Ren; Wei Wang; Hui Huang; Qi Wang; Shiwei Cai

    2011-01-01

    A 1550-nm high-speed, high efficiency, and narrow- linewidth resonant cavity enhanced photodetector with three reso- nant cavities is demonstrated. The photodetector, operating at a long wavelength, is monolithically integrated by using a heteroepi- taxy growth of an InP-based p-i-n structure on the GaAs-based multiple resonant cavities. High-quality heteroepitaxy was real- ized by employing a thin low-temperature buffer layer. A peak

  10. Water in channel-like cavities: structure and dynamics.

    PubMed Central

    Sansom, M S; Kerr, I D; Breed, J; Sankararamakrishnan, R

    1996-01-01

    Ion channels contain narrow columns of water molecules. It is of interest to compare the structure and dynamics of such intrapore water with those of the bulk solvent. Molecular dynamics simulations of modified TIP3P water molecules confined within channel-like cavities have been performed and the orientation and dynamics of the water molecules analyzed. Channels were modeled as cylindrical cavities with lengths ranging from 15 to 60 A and radii from 3 to 12 A. At the end of the molecular dynamics simulations water molecules were observed to be ordered into approximately concentric cylindrical shells. The waters of the outermost shell were oriented such that their dipoles were on average perpendicular to the normal of the wall of the cavity. Water dynamics were analyzed in terms of self-diffusion coefficients and rotational reorientation rates. For cavities of radii 3 and 6 A, water mobility was reduced relative to that of simulated bulk water. For 9- and 12-A radii confined water molecules exhibited mobilities comparable with that of the bulk solvent. If water molecules were confined within an hourglass-shaped cavity (with a central radius of 3 A increasing to 12 A at either end) a gradient of water mobility was observed along the cavity axis. Thus, water within simple models of transbilayer channels exhibits perturbations of structure and dynamics relative to bulk water. In particular the reduction of rotational reorientation rate is expected to alter the local dielectric constant within a transbilayer pore. Images FIGURE 6 PMID:8789086

  11. Crab Cavities for Linear Colliders

    SciTech Connect

    Burt, G.; Ambattu, P.; Carter, R.; Dexter, A.; Tahir, I.; /Cockcroft Inst. Accel. Sci. Tech. /Lancaster U.; Beard, C.; Dykes, M.; Goudket, P.; Kalinin, A.; Ma, L.; McIntosh, P.; /Daresbury; Shulte, D.; /CERN; Jones, Roger M.; /Cockcroft Inst. Accel. Sci. Tech. /Manchester U.; Bellantoni, L.; Chase, B.; Church, M.; Khabouline, T.; Latina, A.; /Fermilab; Adolphsen, C.; Li, Z.; Seryi, Andrei; /SLAC

    2011-11-08

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  12. RF Cavity Characterization with VORPAL

    SciTech Connect

    C. Nieter, C. Roark, P. Stoltz, C.D. Zhou, F. Marhauser

    2011-03-01

    When designing a radio frequency (RF) accelerating cavity structure various figures of merit are considered before coming to a final cavity design. These figures of merit include specific field and geometry based quantities such as the ratio of the shunt impedance to the quality factor (R/Q) or the normalized peak fields in the cavity. Other important measures of cavity performance include the peak surface fields as well as possible multipacting resonances in the cavity. High fidelity simulations of these structures can provide a good estimate of these important quantities before any cavity prototypes are built. We will present VORPAL simulations of a simple pillbox structure where these quantities can be calculated analytically and compare them to the results from the VORPAL simulations. We will then use VORPAL to calculate these figures of merit and potential multipacting resonances for two cavity designs under development at Jefferson National Lab for Project X.

  13. ACAO of cavities

    NASA Astrophysics Data System (ADS)

    Weiland, T.; Zhang, M.

    1993-12-01

    An example for automatic Computer-Aided Optimizations (aCAO) is presented. The aCAO is performed with a newly-born MAFIA optimization driver (OO), which is operated within the MAFIA software environment. The whole optimization procedure with OO is a fully hardware-independent and automatic operation. In the example, the PETRA cavity, now used in the PETRA storage ring, DESY, Germany, is optimized with respect to a goal function of max{Rs/?kt?}. With a view to demonstrating the capability and practicality of the presented optimization driver-OO, we concentrate ourselves mainly on the procedure itself, not on the very essence of how to build a practical PETRA cavity. The obtained results are briefly discussed at the end of the paper.

  14. CAVITY CONTROL ALGORITHM

    SciTech Connect

    Tomasz Plawski, J. Hovater

    2010-09-01

    A digital low level radio frequency (RF) system typically incorporates either a heterodyne or direct sampling technique, followed by fast ADCs, then an FPGA, and finally a transmitting DAC. This universal platform opens up the possibilities for a variety of control algorithm implementations. The foremost concern for an RF control system is cavity field stability, and to meet the required quality of regulation, the chosen control system needs to have sufficient feedback gain. In this paper we will investigate the effectiveness of the regulation for three basic control system algorithms: I&Q (In-phase and Quadrature), Amplitude & Phase and digital SEL (Self Exciting Loop) along with the example of the Jefferson Lab 12 GeV cavity field control system.

  15. High reflected cubic cavity as long path absorption cell for infrared gas sensing

    NASA Astrophysics Data System (ADS)

    Yu, Jia; Gao, Qiang; Zhang, Zhiguo

    2014-10-01

    One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f', and the EOPL equaled to the sum of that of two single cubic cavities at f'<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.

  16. Vertical-cavity surface emitting lasers: moving from research to manufacturing

    Microsoft Academic Search

    KENT D. CHOQUETTE; HONG Q. HOU

    1997-01-01

    After more than a decade of research, vertical-cavity surface emitting lasers (VCSELs) are making the transition into the manufacturing arena. We review unique VCSEL properties found in their structure, growth, fabrication, and performance, which have precipitated their commercial acceptance. The short optical cavity that is formed between two distributed Bragg reflector mirrors is a distinctive VCSEL attribute. The spectral alignment

  17. Multiple membrane cavity optomechanics

    E-print Network

    M. Bhattacharya; P. Meystre

    2008-04-08

    We investigate theoretically the extension of cavity optomechanics to multiple membrane systems. We describe such a system in terms of the coupling of the collective normal modes of the membrane array to the light fields. We show these modes can be optically addressed individually and be cooled, trapped and characterized, e.g. via quantum nondemolition measurements. Analogies between this system and a linear chain of trapped ions or dipolar molecules imply the possibility of related applications in the quantum regime.

  18. Oral melanoacanthoma: A rare case of diffuse oral pigmentation

    PubMed Central

    Gupta, Anish Ashok; Nainani, Purshotam; Upadhyay, Bipin; Kavle, Pratibha

    2012-01-01

    The clinical presentation of diffuse pigmentation can be alarming to the patient as well as the clinician. A histopathologic examination of a pigmented lesion is necessary in most of the cases in the oral cavity. Oral melanoacanthoma is a very rare diffuse pigmentation with no specific treatment required. It shows increased number of dendritic melanocytes in an acanthotic epithelium. We present a rare case of diffuse pigmentation in the oral cavity whose diagnosis was done on the basis of clinical presentation and histopathology. Also immunohistochemistry was done. PMID:23248484

  19. Diffusion barrier cladding in Si\\/SiGe resonant interband tunneling diodes and their patterned growth on PMOS source\\/drain regions

    Microsoft Academic Search

    Niu Jin; Sung-Yong Chung; Anthony T. Rice; Paul R. Berger; Phillip E. Thompson; Cristian Rivas; Roger Lake; Stephen Sudirgo; Jeremy J. Kempisty; Branislav Curanovic; Sean L. Rommel; Karl D. Hirschman; Santosh K. Kurinec; Peter H. Chi; David S. Simons

    2003-01-01

    Si\\/SiGe resonant interband tunnel diodes (RITDs) employing ?-doping spikes that demonstrate negative differential resistance (NDR) at room temperature are presented. Efforts have focused on improving the tunnel diode peak-to-valley current ratio (PVCR) figure-of-merit, as well as addressing issues of manufacturability and CMOS integration. Thin SiGe layers sandwiching the B ?-doping spike used to suppress B out-diffusion are discussed. A room-temperature

  20. Interface Evolution in Three Dimensions¶with Curvature-Dependent Energy¶and Surface Diffusion:¶Interface-Controlled Evolution, Phase Transitions, Epitaxial Growth of Elastic Films

    Microsoft Academic Search

    Morton E. Gurtin; Michel E. Jabbour

    2002-01-01

    When the interfacial energy is a nonconvex function of orientation, the anisotropic-curvature-flow equation becomes backward\\u000a parabolic. To overcome the instability thus generated, a regularization of the equation that governs the evolution of the\\u000a interface is needed. In this paper we develop a regularized theory of curvature flow in three dimensions that incorporates\\u000a surface diffusion and bulk-surface interactions. The theory is

  1. Superconducting cavities and modulated RF

    SciTech Connect

    Farkas, Z.D.

    1981-02-01

    If a cavity has an infinite Q/sub o/, 81.5% of the energy contained in a pulse incident upon the cavity is transferred into the cavity by the end of the pulse if the cavity Q/sub e/ is chosen so that the cavity time constant is 0.796 pulse width (T/sub a/). As Q/sug o/ decreases, the energy in the cavity at the end of the pulse decreases very slowly as long as T/sub a/ is much less than the unloaded cavity time constant, T/sub co/. SC cavities with very high Q/sub o/ enable one to obtain very high gradients with a low power cw source. At high gradients, however, one often does not attain the high Q/sub o/ predicted by theory. Therefore, if one is inteerested in attaining maximum energy in the cavity, as is the case for RF processing and diagnostics, for a given available source energy there is no point in keeping the power on for longer than 0.1 T/sub co/ because the energy expended after 0.1 T/sub co/ is wasted. Therefore, to attain high fields at moderate Q/sub o/, pulsed operation is indicated. This note derives the fields and energy stored and dissipated in the cavity when Q/sub e/ is optimized for a given T/sub a/. It shows how to use this data to measure Q/sub o/ of an SC cavity as a function of field level, how to process the cavity with high RF fields, how to operate SC cavities in the pulsed mode to obtain higher efficiencies and gradients. Experimental results are also reported.

  2. Diffusion of spherical particles in microcavities

    E-print Network

    A. Imperio; J. T. Padding; W. J. Briels

    2011-03-25

    The diffusive motion of a colloidal particle trapped inside a small cavity filled with fluid is reduced by hydrodynamic interactions with the confining walls. In this work, we study these wall effects on a spherical particle entrapped in a closed cylinder. We calculate the diffusion coefficient along the radial, azimuthal and axial direction for different particle positions. At all locations the diffusion is smaller than in a bulk fluid and it becomes anisotropic near the container's walls. We present a simple model which reasonably well desribes the simulation results for the given dimensions of the cylinder, which are taken from recent experimental work.

  3. Fokker-Planck . . . Diffusion . . .

    E-print Network

    Fokker-Planck . . . Diffusion . . . Diffusion- . . . Application: . . . Summary and . . . First #12;Fokker-Planck . . . Diffusion . . . Diffusion- . . . Application: . . . Summary and . . . Topics: 1. Fokker-Planck transport equation 2. Diffusion approximation 3. Diffusion-convection transport

  4. Introduction Diffusion Tensor Imaging

    E-print Network

    Zhang, Shuzhong

    Introduction Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further ·Full Screen ·Close ·Quit Diffusion Tensor and Diffusion Kurtosis Tensor in Biomedical Engineering Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further Discussion Home Page

  5. FORWARD MODELING CAVITY DENSITY: A MULTI-INSTRUMENT DIAGNOSTIC

    SciTech Connect

    Schmit, D. J. [Department of Astrophysical and Planetary Science, University of Colorado, Boulder, CO 80305 (United States); Gibson, S. E. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307 (United States)

    2011-05-20

    The thermodynamic properties of coronal prominence cavities present a unique probe into the energy and mass budget of prominences. Using a three-dimensional morphological model, we forward model the polarization brightness and extreme-ultraviolet (EUV) emission of a cavity and its surrounding streamer. Using a genetic algorithm, we find the best-fit density model by comparing the models to Mauna Loa Solar Observatory MK4 and Hinode EUV Imaging Spectrometer data. The effect of temperature variations on the derived density is also measured. We have measured the density inside a cavity down to 1.05 R{sub sun} with height-dependent error bars. Our forward modeling technique compensates for optically thin projection effects. This method provides a complementary technique to traditional line ratio diagnostics that is useful for diffuse off-limb coronal structures.

  6. Relativistic diffusion

    E-print Network

    Haba, Z

    2008-01-01

    We define a relativistic diffusion equation on the phase space. We consider stochastic Ito (Langevin) differential equation on the phase space as a perturbation by noise of relativistic dynamics. The motion in an electromagnetic field is treated as an example. Transport equations and equilibrium probability distributions are investigated. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  7. Hillslope diffusion

    NSDL National Science Digital Library

    Jeni McDermott

    This lab is designed to help students apply hillslope diffusion equations (derived in class prior to the lab) to understand real-world hillslopes. The major goal is a deeper understanding of hillslope processes and the equations used to describe hillslope diffusion by observing the same factors described in the equations on real-world hillslopes.

  8. Hypersonic flow past open cavities

    NASA Technical Reports Server (NTRS)

    Morgenstern, Alagacyr, Jr.; Chokani, Ndaona

    1993-01-01

    The hypersonic flow over a cavity is investigated. The time-dependent compressible Navier-Stokes equations, in terms of mass averaged variables, are numerically solved. An implicit algorithm, with a subiteration procedure to recover time-accuracy, is used to perform the time-accurate computations. The objective of the study is to investigate the effects of Reynolds number and cavity dimensions. The comparison of the computations with available experimental data, in terms of time mean static pressure, heat transfer, and Mach number show good agreement. In the computations large vortex structures, which adversely affect the cavity flow characteristics, are observed at the rear of the cavity. A self-sustained oscillatory motion occurs within the cavity over a range of Reynolds number and cavity dimensions. The frequency spectra of the oscillations show good agreement with a modified semi-empirical relation.

  9. Hypersonic flow past open cavities

    NASA Technical Reports Server (NTRS)

    Morgenstern, Algacyr, Jr.; Chokani, Ndaona

    1994-01-01

    The hypersonic flow over a cavity is investigated. The time-dependent compressible Navier-Stokes equations are numerically solved. An implicit algorithm, with a subiteration procedure to recover time accuracy, is used to perform the time-accurate computations. The objective of the study is to investigate the effects of Reynolds number and cavity dimensions. The comparsion of the computations with available experimental data, in terms of time mean static pressure, heat transfer, and Mach number, show good agreement. In the computations large vortex structures, which adversely affect the cavity flow characteristics, are observed at the rear of the cavity. A self-sustained oscillatory motion occurs within the cavity over a range of Reynolds number and cavity dimensions. The frequency spectra of the oscillations show good agreement with a modified semiempirical relation.

  10. Diffusion-Limited Aggregation with Active Edge Diffusion

    Microsoft Academic Search

    Holger Röder; Karsten Bromann; Harald Brune; Klaus Kern

    1995-01-01

    Diffusion-limited aggregation of Ag on Pt(111) and Ag(111) has been studied by scanning tunneling microscopy. In both metal-on-metal systems fractal growth shapes are found in an extended range of deposition temperature and deposition flux. In contrast to classic hit-and-stick diffusion-limited aggregation simulations the average branch width of the ramified aggregates is not monatomic and increases with increasing deposition temperature, which

  11. Superconducting Radio-Frequency Cavities

    NASA Astrophysics Data System (ADS)

    Padamsee, Hasan S.

    2014-10-01

    Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

  12. Nose, Nasal Cavities & Paranasal Sinuses

    MedlinePLUS

    Search SEER Training: SEER Training Modules Print Home Glossary Citation Help Home » Cancer Registration & Surveillance Modules » Anatomy & Physiology » Respiratory System » Conducting Passages » Nose, Nasal Cavities & ...

  13. Cavity optoelectromechanical regenerative amplification

    E-print Network

    Taylor, Michael A; Knittel, Joachim; Lee, Kwan H; McRae, Terry G; Bowen, Warwick P

    2011-01-01

    Regenerative amplification is demonstrated in a cavity optoelectromechanical system using electrical gradient forces and optomechanical transduction. Mechanical linewidth narrowing to $6.6 \\pm 1.4$ mHz was observed at a frequency of 27.3 MHz, corresponding to an effective mechanical quality factor of $4 \\times 10^9$. A theoretical model of the system was formulated, showing that the delay in electrical feedback allows additional linewidth narrowing compared to purely optomechanical regenerative amplification. The linewidth was confirmed experimentally to scale inversely with the mechanical energy as predicted by the model.

  14. Counterion Diffusion in Ionomers

    NASA Astrophysics Data System (ADS)

    Walter, Russell; Winey, Karen; Kim, Joon-Seop; Composto, Russell

    2004-03-01

    Diffusion of Cs counterions to the air/ionomer film interface is followed using Rutherford backscattering spectrometry and results compared with the "sticky reptation" model[1]. The ionomer system is poly(styrene-ran-methacrylic acid) (Cs-SMAA) neutralized at 100% by Cs. The concentration profiles exhibit a surface excess, z*, of Cs followed by a depletion of Cs. The z* and depletion layer thickness grow as t1/2, consistent with diffusion limited growth. Annealing studies at 130 °C, 145 °C and 208 °C were used to extract the diffusion coefficient, D. In all cases, D is greater than that of the matrix chains. These results suggest that the diffusion rate is controlled by the fraction of counterions that disassociate from the acid groups and migrate through the matrix. Moreover, the "sticky reptation" model doesn't appear to predict the diffusion behavior in the Cs-SMAA system. [1] Leibler, L, Ludwick, L., Rubinstein, M., Colby, R.H., Macromolecules 24 (1991) 4701.

  15. New Chorus Diffusion Matrix

    NASA Astrophysics Data System (ADS)

    Horne, Richard B.; Kersten, Tobias; Glauert, Sarah A.; Meredith, Nigel P.; Boscher, Daniel; Sicard, Angelica; Maget, Vincent

    2013-04-01

    Whistler mode chorus waves play a major role in the loss and acceleration of electrons in the Earth's radiation belts. While high time resolution satellite data show that these waves are highly structured in frequency and time, at present their effects on the electron distribution can only be assessed on a global scale by using quasi-linear diffusion theory. Here we present new quasi-linear diffusion coefficients for upper and lower band chorus waves for use in global radiation belt models. Using data from DE 1 CRRES, Cluster 1, Double Star TC1 and THEMIS, we have constructed a database of wave properties and used this to construct new diffusion coefficients for L* = 1.5 to 10 in steps of 0.5, 10 latitude bins between 0o and 60o ,8 bins in MLT and 5 levels of geomagnetic activity as measured by Kp. We find that the peak frequency of lower band chorus is close to 0.2 fce, which is lower than that used in previous models. The combined upper and lower band chorus diffusion shows structure that should result in an energy dependent pitch angle anisotropy, particularly between 1 keV and 100 keV. The diffusion rates suggest that wave-particle interactions should still be very important outside geostationary orbit, out to at least L* = 8. We find significant energy diffusion near 1 keV near the loss cone, consistent with wave growth. By including the new chorus diffusion matrix into the BAS radiation belt (BRB) model we compare the effects on the evolution of the radiation belts against previous models.

  16. Potassium-Induced Cortical Spreading Depressions During Focal Cerebral Ischemia in Rats: Contribution to Lesion Growth Assessed by Diffusion-Weighted NMR and Biochemical Imaging

    Microsoft Academic Search

    Elmar Busch; Michael L. Gyngell; Manfred Eis; Mathias Hoehn-Berlage; Konstantin-Alexander Hossmann

    1996-01-01

    In focal ischemia of rats, the volume of ischemic lesion correlates with the number of peri-infarct depolarizations. To test the hypothesis that depolarizations accelerate infarct growth, we combined focal ischemia with externally evoked spreading depression (SD) waves. Ischemic brain infarcts were produced in halothane-anaesthetized rats by intraluminal thread occlusion of the middle cerebral artery (MCA). In one group of animals,

  17. Tissue culture in synthetic atmospheres: diffusion rate effects on cytokinin-induced callus growth and isoflavonoid production in soybean [ Glycine max (L.) Merr. cv. Acme

    Microsoft Academic Search

    Lindsey K. Tuominen; Mary E. Musgrave

    2006-01-01

    Concentration is one factor that is known to determine how metabolic gases influence the growth and secondary metabolism of plant tissues in culture. How actual gas bioavailability influences these processes has not been studied despite its potential importance in specialized applications. A simple model system, soybean [Glycine max (L.) Merr. cv. Acme] callus culture, was selected for experiments because exogenous

  18. Gigahertz Modulation of a Photonic Crystal Cavity

    NASA Astrophysics Data System (ADS)

    Ali, Aaron Karim Taylor

    Photonic crystal (PtC) cavities are an increasingly important way to create all optical methods to control optical data. Not only must the data be controlled, but interfacing it with high frequency electrical signals is particularly interesting especially if this occurs in the 1.55microm telecom band. We present an experiment that uses Rayleigh surface acoustic waves (SAWs) to modulate the frequency of the guided mode of an L3-cavity PtC created on a silicon slab. This work has the potential to interface optical and electrical signals via a mechanical strain wave operating at gigahertz frequencies. Defects are carefully designed into a triangular lattice PtC to realize a waveguide coupled optical cavity. The cavity can be experimentally accessed through grating couplers excited by polarized light at 10° incidence from normal. The optical components are fabricated on a silicon-on-insulator platform, with light confined to the silicon slab region. Through transmission experiments, the L3 cavity was found to have a narrow resonance characterized by a Lorentzian distribution. A quality factor of 165 centered at 6255cm --1 (1.599microm) was measured. Aluminum interdigitated transducers (IDTs) were fabricated through a lithography liftoff process. Their ability to create SAWs requires a piezoelectric medium. As silicon does not have this property, growth of a thin ZnO film was required. The transducers were measured using a network analyzer and were found to produce Rayleigh SAWs at a frequency of 179MHz and a wavelength of 24microm. The acoustic energy traveled 70microm to the target optical device. The L3 cavity has dimensions of around 4microm a side - less than 1/2 a SAW wavelength. Modulation of the L3 PtC resonant frequency was monitored through a repeat of the transmission experiment but with RF excitation of the IDTs at the SAW frequency. A broadening of the transmission spectrum was expected. Unfortunately no change in the fitting parameters could be measured. An HF etch was used to undercut the L3 PtC such that a silicon slab suspended in air could be realized. Simulations had been conducted showing an order of magnitude increase in the quality factor was possible. Broken wirebonds on the transducers created unintended etch channels rendering the SAW non-operational.

  19. Human capital and technology diffusion

    Microsoft Academic Search

    Jess Benhabib; Mark M. Spiegel

    2002-01-01

    This paper generalizes the Nelson-Phelps catch-up model of technology diffusion. We allow for the possibility that the pattern of technology diffusion can be exponential, which would predict that nations would exhibit positive catch-up with the leader nation, or logistic, in which a country with a sufficiently small capital stock may exhibit slower total factor productivity growth than the leader nation.

  20. Applications of cavity optomechanics

    SciTech Connect

    Metcalfe, Michael [Booz Allen Hamilton, 3811 Fairfax Drive, Arlington, Virginia 22203 (United States)

    2014-09-15

    Cavity-optomechanics” aims to study the quantum properties of mechanical systems. A common strategy implemented in order to achieve this goal couples a high finesse photonic cavity to a high quality factor mechanical resonator. Then, using feedback forces such as radiation pressure, one can cool the mechanical mode of interest into the quantum ground state and create non-classical states of mechanical motion. On the path towards achieving these goals, many near-term applications of this field have emerged. After briefly introducing optomechanical systems and describing the current state-of-the-art experimental results, this article summarizes some of the more exciting practical applications such as ultra-sensitive, high bandwidth accelerometers and force sensors, low phase noise x-band integrated microwave oscillators and optical signal processing such as optical delay-lines, wavelength converters, and tunable optical filters. In this rapidly evolving field, new applications are emerging at a fast pace, but this article concentrates on the aforementioned lab-based applications as these are the most promising avenues for near-term real-world applications. New basic science applications are also becoming apparent such as the generation of squeezed light, testing gravitational theories and for providing a link between disparate quantum systems.

  1. Microwave Cavity Searches

    NASA Astrophysics Data System (ADS)

    Carosi, Gianpaolo; Bibber, Karl Van

    This chapter will cover the search for dark matter axions based on microwave cavity experiments proposed by Pierre Sikivie. We will start with a brief overview of halo dark matter and the axion as a candidate. The principle of resonant conversion of axions in an external magnetic field will be described as well as practical considerations in optimizing the experiment as a signal-to-noise problem. A major focus of this chapter will be the two complementary strategies for ultra-low noise detection of the microwave photons the “photon-as-wave” approach (i.e., conventional heterojunction amplifiers and soon to be quantum-limited SQUID devices), and the “photon-as-particle” approach (i.e.,Rydberg-atom single-quantum detection). Experimental results will be presented; these experiments have already reached well into the range of sensitivity to exclude plausible axion models, for limited ranges of mass. The chapter will conclude with a discussion of future plans and challenges for the microwave cavity experiment.

  2. Accelerated shrinkage of creep cavities by thermal cycling of dispersion-strengthened aluminum

    SciTech Connect

    Schuh, C.; Han, B.Q.; Dunand, D.C.

    1999-07-01

    High-temperature engineering materials which develop creep cavities in service can be rejuvenated by intermediate annealing, with or without external hydrostatic pressure to close creep cavities. The authors report here experimental data of creep cavity shrinkage for dispersion-strengthened-cast aluminum with about 23% submicron Al{sub 2}O{sub 3} dispersoids, annealed isothermally or subjected to thermal cycling without applied stress. They demonstrate that thermal cycling increases the rate of cavity shrinkage relative to isothermal annealing, allowing for recovery of full theoretical density in a shorter time. Isothermal and thermal cycling densification is considered in light of diffusive cavity shrinkage mechanisms, and a simple model considering thermal mismatch stresses is employed to estimate the enhanced rate of densification during thermal cycling.

  3. Diffuse radiation

    NASA Technical Reports Server (NTRS)

    1981-01-01

    A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

  4. Critical Oxide Thickness for Efficient Single-walled Carbon Nanotube Growth on Silicon Using Thin SiO2 Diffusion Barriers

    Microsoft Academic Search

    J. M. Simmons; B. M. Nichols; Matthew S. Marcus; O. M. Castellini; R. J. Hamers; M. A. Eriksson

    2007-01-01

    The ability to integrate carbon nanotubes, especially single-walled carbon nanotubes, seamlessly onto silicon would expand the range of applications considerably. Though direct integration using chemical vapor deposition is the simplest method, the growth of single-walled carbon nanotubes on bare silicon and on ultra-thin oxides is greatly inhibited due to the formation of a non-catalytic silicide. Using x-ray photoelectron spectroscopy, we

  5. Critical oxide thickness for efficient single-walled carbon nanotube growth on silicon using thin SiO2 diffusion barriers

    Microsoft Academic Search

    Robert J. Hamers

    2006-01-01

    The ability to integrate carbon nanotubes, especially single-walled carbon nanotubes, seamlessly onto silicon would expand their range of applications considerably. Though direct integration using chemical vapor deposition is the simplest method, the growth of single-walled carbon nanotubes on bare silicon and on ultrathin oxides is greatly inhibited due to the formation of a noncatalytic silicide. Using X-ray photoelectron spectroscopy, we

  6. 2.5 D Cavity Balancing

    E-print Network

    Jin, S.

    Cavity balancing is the process of altering the flow front within a cavity through thickness and design changes such that the desired fill pattern is achieved. The 2 dimensional (2D) cavity-balancing algorithm, developed ...

  7. Temporary Sealing of Cavities for Leak Testing

    NASA Technical Reports Server (NTRS)

    Little, J.

    1984-01-01

    Wax Seals cavity openings to permit helium leak test of cavity welds. Technique facilitates leak testing of cavities in components of larger systems not otherwise sealed off at time leak testing done.

  8. Quench studies of ILC cavities

    SciTech Connect

    Eremeev, Grigory; Geng, Rongli; Palczewski, Ari; Dai, Jin

    2011-07-01

    Quench limits accelerating gradient in SRF cavities to a gradient lower than theoretically expected for superconducting niobium. Identification of the quenching site with thermometry and OST, optical inspection, and replica of the culprit is an ongoing effort at Jefferson Lab aimed at better understanding of this limiting phenomenon. In this contribution we present our finding with several SRF cavities that were limited by quench.

  9. Identification of EZH2 and EZH1 small molecule inhibitors with selective impact on diffuse large B cell lymphoma cell growth.

    PubMed

    Garapaty-Rao, Shivani; Nasveschuk, Christopher; Gagnon, Alexandre; Chan, Eric Y; Sandy, Peter; Busby, Jennifer; Balasubramanian, Srividya; Campbell, Robert; Zhao, Feng; Bergeron, Louise; Audia, James E; Albrecht, Brian K; Harmange, Jean-Christophe; Cummings, Richard; Trojer, Patrick

    2013-11-21

    The histone methyltransferase enhancer of Zeste homolog 2 (EZH2) is a candidate oncogene due to its prevalent overexpression in malignant diseases, including late stage prostate and breast cancers. The dependency of cancer cells on EZH2 activity is also predicated by recurrent missense mutations residing in the catalytic domain of EZH2 that have been identified in subtypes of diffuse large B cell lymphoma, follicular lymphoma and melanoma. Herein, we report the identification of a highly selective small molecule inhibitor series of EZH2 and EZH1. These compounds inhibit wild-type and mutant versions of EZH2 with nanomolar potency, suppress global histone H3-lysine 27 methylation, affect gene expression, and cause selective proliferation defects. These compounds represent a structurally distinct EZH2 inhibitor chemotype for the exploration of the role of Polycomb Repressive Complex 2-mediated H3K27 methylation in various biological contexts. PMID:24183969

  10. Probing Water Density and Dynamics in the Chaperonin GroEL Cavity

    PubMed Central

    2015-01-01

    ATP-dependent binding of the chaperonin GroEL to its cofactor GroES forms a cavity in which encapsulated substrate proteins can fold in isolation from bulk solution. It has been suggested that folding in the cavity may differ from that in bulk solution owing to steric confinement, interactions with the cavity walls, and differences between the properties of cavity-confined and bulk water. However, experimental data regarding the cavity-confined water are lacking. Here, we report measurements of water density and diffusion dynamics in the vicinity of a spin label attached to a cysteine in the Tyr71 ? Cys GroES mutant obtained using two magnetic resonance techniques: electron-spin echo envelope modulation and Overhauser dynamic nuclear polarization. Residue 71 in GroES is fully exposed to bulk water in free GroES and to confined water within the cavity of the GroEL–GroES complex. Our data show that water density and translational dynamics in the vicinity of the label do not change upon complex formation, thus indicating that bulk water-exposed and cavity-confined GroES surface water share similar properties. Interestingly, the diffusion dynamics of water near the GroES surface are found to be unusually fast relative to other protein surfaces studied. The implications of these findings for chaperonin-assisted folding mechanisms are discussed. PMID:24888581

  11. Monochromatic radio frequency accelerating cavity

    DOEpatents

    Giordano, S.

    1984-02-09

    A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

  12. Monochromatic radio frequency accelerating cavity

    DOEpatents

    Giordano, Salvatore (Port Jefferson, NY)

    1985-01-01

    A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

  13. Superconducting Storage Cavity for RHIC

    SciTech Connect

    Ben-Zvi,I.

    2009-01-02

    This document provides a top-level description of a superconducting cavity designed to store hadron beams in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It refers to more detailed documents covering the various issues in designing, constructing and operating this cavity. The superconducting storage cavity is designed to operate at a harmonic of the bunch frequency of RHIC at a relatively low frequency of 56 MHz. The current storage cavities of RHIC operate at 197 MHz and are normal-conducting. The use of a superconducting cavity allows for a high gap voltage, over 2 MV. The combination of a high voltage and low frequency provides various advantages stemming from the resulting large longitudinal acceptance bucket.

  14. Hopf bifurcation in the driven cavity

    NASA Technical Reports Server (NTRS)

    Goodrich, John W.; Gustafson, Karl; Halasi, Kadosa

    1989-01-01

    Incompressible two dimensional calculations are reported for the impulsively started lid driven cavity with aspect ratio two. The algorithm is based on the time dependent streamfunction equation, with a Crank-Nicolson differencing scheme for the diffusion terms, and with an Adams-Bashforth scheme for the convection terms. A multigrid method is used to solve the linear implicit equations at each time step. Periodic asymptotic solutions have been found for Re = 10000 and for Re = 5000. The Re = 5000 results are validated by grid refinement calculations. The solutions are shown to be precisely periodic, and care is taken to demonstrate that asymptotic states were reached. A discussion is included about the indicators that are used to show that an asymptotic state was reached, and to show that the asymptotic state is indeed periodic.

  15. Changeability of Oral Cavity Environment

    PubMed Central

    Surdacka, Anna; Strzyka³a, Krystyna; Rydzewska, Anna

    2007-01-01

    Objectives In dentistry, the results of in vivo studies on drugs, dental fillings or prostheses are routinely evaluated based on selected oral cavity environment parameters at specific time points. Such evaluation may be confounded by ongoing changes in the oral cavity environment induced by diet, drug use, stress and other factors. The study aimed to confirm oral cavity environment changeability. Methods 24 healthy individuals aged 20–30 had their oral cavity environment prepared by having professional hygiene procedures performed and caries lesions filled. Baseline examination and the examination two years afterwards, evaluated clinical and laboratory parameters of oral cavity environment. Caries incidence was determined based on DMFT and DMFS values, oral cavity hygiene on Plaque Index (acc. Silness & Loe) and Hygiene Index (acc. O’Leary), and the gingival status on Gingival Index (acc. Loe & Silness) and Gingival Bleeding Index (acc. Ainamo & Bay). Saliva osmolarity, pH and concentrations of Ca2+, Pi, Na+, Cl?, total protein, albumins, F? and Sr2+ were determined. Results The results confirmed ongoing changeability of the oral cavity environment. After 2 years of the study reduction in oral cavity hygiene parameters PLI and HI (P<0.1), and gingival indices as well as lower saliva concentration of Ca2+ (P<.001), Pi (P<.06), K+ (P<.04), Sr2+ (P<.03), Na+ (P<.1), against the baseline values, were observed. Total protein and albumin saliva concentrations were also significantly lower. Conclusion Physiological oral cavity environment is subject to constant, individually different, changes which should be considered when analysing studies that employ oral cavity environment parameters. PMID:19212491

  16. A scanning cavity microscope

    PubMed Central

    Mader, Matthias; Reichel, Jakob; Hänsch, Theodor W.; Hunger, David

    2015-01-01

    Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1,700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1?nm2; we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems. PMID:26105690

  17. A scanning cavity microscope.

    PubMed

    Mader, Matthias; Reichel, Jakob; Hänsch, Theodor W; Hunger, David

    2015-01-01

    Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1,700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1?nm(2); we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems. PMID:26105690

  18. A Scanning Cavity Microscope

    E-print Network

    Mader, Matthias; Hänsch, Theodor W; Hunger, David

    2014-01-01

    Imaging of the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1700-fold signal enhancement compared to diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross section of gold nanoparticles with a sensitivity below 1 nm2, we show a method to improve spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for opt...

  19. Composite resonator vertical cavity laser diode

    SciTech Connect

    Choquette, K.D.; Hou, H.Q.; Chow, W.W.; Geib, K.M.; Hammons, B.E.

    1998-05-01

    The use of two coupled laser cavities has been employed in edge emitting semiconductor lasers for mode suppression and frequency stabilization. The incorporation of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. Composite resonators can be utilized to control spectral and temporal properties within the laser; previous studies of coupled cavity vertical cavity lasers have employed photopumped structures. The authors report the first composite resonator vertical cavity laser diode consisting of two optical cavities and three monolithic distributed Bragg reflectors. Cavity coupling effects and two techniques for external modulation of the laser are described.

  20. Critical Oxide Thickness for Efficient Single-walled Carbon Nanotube Growth on Silicon Using Thin SiO2 Diffusion Barriers

    Microsoft Academic Search

    J. M. Simmons; Beth M. Nichols; Matthew S. Marcus; O. M. Castellini; R. J. Hamers; M. A. Eriksson

    2007-01-01

    The ability to integrate carbon nanotubes, especially single-walled carbon\\u000ananotubes, seamlessly onto silicon would expand the range of applications\\u000aconsiderably. Though direct integration using chemical vapor deposition is the\\u000asimplest method, the growth of single-walled carbon nanotubes on bare silicon\\u000aand on ultra-thin oxides is greatly inhibited due to the formation of a\\u000anon-catalytic silicide. Using x-ray photoelectron spectroscopy, we

  1. Design of external cavities for vertical-cavity semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Paxton, Alan H.; White, Cheryl J.; Hersee, Stephen D.; McInerney, John G.

    1993-08-01

    High power density can be obtained from vertical-cavity surface emitting semiconductor lasers (VCSELs), but the emitting area must be kept small if spatial coherence is desired. We present the result of a theoretical and calculational study of the possibility of placing the gain regions of VCSELs in external cavities to provide mode control over a larger area. A Fabry-Perot or stable resonator with very low loss is required. Several configurations are discussed and evaluated. A ring cavity is the most practical due to its relative lack of sensitivity to misalignment of the mirrors.

  2. Prognostic significance of the aggregative perivascular growth pattern of tumor cells in primary central nervous system diffuse large B-cell lymphoma

    PubMed Central

    He, Miaoxia; Zuo, Changjing; Wang, Jianjun; Liu, Jianmin; Jiao, Binghua; Zheng, Jianmin; Cai, Zailong

    2013-01-01

    Background Primary central nervous system lymphomas, predominantly diffuse large B-cell lymphomas (PCNS-DLBCL), are aggressive malignancies, and no histopathological variables with independent prognostic value are currently available. The aim of this study is to determine the prognostic value of histopathological variables of PCNS-DLBCL. Methods Aggregative perivascular tumor cells (APVTs) and reactive perivascular T cell infiltrates (RPVIs) in tumor samples from 62 immunocompetent patients with PCNS-DLBCL were histopathologically and immunohistochemically studied. A mouse brain DLBCL model was established to confirm the special morphological features of PCNS-DLBCL. The therapy, overall response rate (ORR), and overall survival (OS) among patients were followed up. Results APVT was present in 54 (87%) of the 62 cases, whereas RPVI was present in 20 (32%). Patients with APVT-positive lesions exhibited significantly worse OS, with intermediate to high International Extranodal Lymphoma Study Group (IELSG) scores, compared with patients with RPVI-positive lesions. Among cases of APVT-positive lymphoma, the semiquantitative score of immunostaining of X-box–binding protein (XBP1) and CD44 demonstrated prognostic significance. Multivariate analysis confirmed independent associations between APVT and XBP1 and between CD44 staining and survival. Conclusions The presence of APVT and staining of XBP1 and CD44 are independently associated with survival among patients with PCNS-DLBCL. These features could be routinely assessed in histopathological and immunohistochemical specimens. PMID:23482670

  3. Microscopic toy model for Cavity dynamical Casimir effect

    E-print Network

    I. M. de Sousa; A. V. Dodonov

    2015-04-09

    We develop a microscopic toy model for Cavity dynamical Casimir effect (DCE), namely, the photon generation from vacuum due to a nonstationary dielectric slab in a fixed single mode cavity. We represent the slab by $N\\gg 1$ noninteracting two-level atoms coupled to the field via the standard dipole interaction. We show that the DCE is contained implicitly in the light-matter interaction Hamiltonian when its parameters are externally prescribed functions of time. We also predict several new phenomena, such as saturation of the photon growth due to effective Kerr nonlinearity, generation of pairs of atomic excitations instead of photons ("Inverse DCE") and coherent annihilation of pair of system excitations due to the atomic modulation ("Anti-DCE"). These results are extended to the circuit QED architecture, where similar effects can be implemented with a single qubit providing an alternative way to generate cavity and atom-field entangled states.

  4. The Diffusion Mediated Biochemical Signal Relay Channel

    E-print Network

    Thomas, Peter J.

    The Diffusion Mediated Biochemical Signal Relay Channel Peter J. Thomas , Donald J. Spencer localization by the immune system, Corresponding author: pjthomas@salk.edu dspencer@salk.edu #12;growth-cone

  5. Environmental enhancement of creep crack growth in Inconel 718 by oxygen and water vapor

    SciTech Connect

    Valerio, P.; Gao, M.; Wei, R.P. (Lehigh Univ., Bethlehem, PA (United States). Dept. of Mechanical Engineering and Mechanics)

    1994-05-15

    Inconel 718 alloy is widely used in high temperature applications. Because of its sensitivity to environmentally enhanced crack growth at high temperatures, its use has been limited to modest temperatures (i.e., below 973 K). To improve its performance and to better predict its service life, it is important to develop a better understanding of the processes of crack growth at high temperatures in this alloy. It has been shown that the creep crack growth rates (CCGR) in air are at least two orders of magnitude faster than those in vacuum or inert environments. CCGR were also found to depend strongly on temperature. Fractographic studies showed that crack growth was intergranular in air and in vacuum with brittle appearing grain boundary separation in air and extensive cavity formation in vacuum. The increased CCGR in air has been attributed to the enhancement by oxygen; principally through enhanced cavity nucleation and growth by high-pressure carbon monoxide/dioxide formed by the reactions of oxygen that diffused into the material with the grain boundary carbides. The appropriateness of this mechanism, however, may be questioned by the absence of cavitation on the crack surfaces produced in air. As such the mechanism for crack growth needs to be re-examined. Because of the presence of moisture in air, the possible influence of hydrogen needs to be considered as well. In this study, preliminary experiments were conducted to examine the process of environmentally enhanced creep crack growth in Inconel 718 alloy in terms of possible mechanisms and rate controlling processes. Creep crack growth experiments were carried out in air, oxygen (from 2.67 to 100 kPa), moist argon (water vapor) and pure argon at temperatures from 873 to 973 K.

  6. Fast anomalous diffusion of small hydrophobic species in water.

    PubMed

    Kirchner, Barbara; Stubbs, John; Marx, Dominik

    2002-11-18

    Using Car-Parrinello molecular dynamics a structural diffusion mechanism for the simplest hydrophobic species in water, an H atom, is proposed. The hydrophobic solvation cavity is a highly dynamical aggregate that actually drives, by its own hydrogen-bond fluctuations, the diffusion of the enclosed solute. This makes possible an anomalously fast diffusion that falls only short of that of "Grotthuss structural diffusion" of H+ in water. Here, the picture of a static, i.e., "iceberglike," clathrate cage is a misleading concept. The uncovered scenario is similar to the "dynamical hole mechanism" found in a very different context, that is, large molecules moving in hot polymeric melts. PMID:12443432

  7. A Theory of Diffusion Cloud Chambers

    Microsoft Academic Search

    R. P. Shutt

    1951-01-01

    An attempt is made to understand quantitatively the effects of a given gas, gas pressure, vapor, ionization density, and temperature distribution on the operation of diffusion chambers. An integral equation is set up which takes into account diffusion of the vapor through the gas, removal of vapor by condensation, drop growth, and the motion of the drops due to gravity.

  8. Relativistic diffusion.

    PubMed

    Haba, Z

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed. PMID:19391727

  9. Relativistic diffusion

    E-print Network

    Z. Haba

    2009-02-26

    We discuss a relativistic diffusion in the proper time in an approach of Schay and Dudley. We derive (Langevin) stochastic differential equations in various coordinates.We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form.We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution.We discuss drag terms leading to an equilibrium distribution.The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Juettner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  10. Relativistic diffusion

    Microsoft Academic Search

    Z. Haba

    2009-01-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic

  11. Diffusion Models

    NSDL National Science Digital Library

    Alexei Sharov

    Web-based intructional material describing the use of diffusion models in population ecology. This page is part of a set of on-line lectures on Quantitative Population Ecology produced by Alexei Sharov in the Department of Entomology at Virginia Tech.

  12. Relativistic diffusion

    NASA Astrophysics Data System (ADS)

    Haba, Z.

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  13. Model based study of various configurations of jet crossing a cavity. Application to the CEPRA 19 wind tunnel of propulsion test center (CEPr)

    Microsoft Academic Search

    P. Rebuffet; A. Guedel

    1982-01-01

    A scale model study of a jet crossing the cavity made by the chamber of an anechoic wind tunnel was undertaken. The length of the free jet and the dimensions of the diffuser inlet were varied. Cavity resonances due to aeroacoustic coupling which can prevent measurements from being made, were investigated. Background noise was measured. The aerodynamic characteristics of the

  14. Folded layer multiple-pass cavity

    Microsoft Academic Search

    Yuguang Xu; Qinyue Yu; Bo Lyu; Shou-Hau Chen; Zhong-Hua Rong

    1991-01-01

    Structure of the folded layered multiple-pass cavity and its image quality are described, uniformity of scanning beam intensity at vertical direction in the middle position of the cavity is discussed, and the high precision result of the reflectance cavity mirror is given. The folded layered multiple-pass cavity presented in this article has the following physical requirements: it must have a

  15. Improved integrating cavity absorption meter

    E-print Network

    Cui, Liqiu

    2000-01-01

    combined with our uses of isotropic illumination. The latter is achieved by employing a high reflectivity (greater than 0.99) lambertian material to build the integrating cavity. We provide complete documentation of the apparatus, both the hardware...

  16. Nonlocal Intracranial Cavity Extraction

    PubMed Central

    Manjón, José V.; Eskildsen, Simon F.; Coupé, Pierrick; Romero, José E.; Collins, D. Louis; Robles, Montserrat

    2014-01-01

    Automatic and accurate methods to estimate normalized regional brain volumes from MRI data are valuable tools which may help to obtain an objective diagnosis and followup of many neurological diseases. To estimate such regional brain volumes, the intracranial cavity volume (ICV) is often used for normalization. However, the high variability of brain shape and size due to normal intersubject variability, normal changes occurring over the lifespan, and abnormal changes due to disease makes the ICV estimation problem challenging. In this paper, we present a new approach to perform ICV extraction based on the use of a library of prelabeled brain images to capture the large variability of brain shapes. To this end, an improved nonlocal label fusion scheme based on BEaST technique is proposed to increase the accuracy of the ICV estimation. The proposed method is compared with recent state-of-the-art methods and the results demonstrate an improved performance both in terms of accuracy and reproducibility while maintaining a reduced computational burden. PMID:25328511

  17. Illumination devices for photodynamic therapy of the oral cavity

    PubMed Central

    Canavesi, Cristina; Fournier, Florian; Cassarly, William J.; Foster, Thomas H.; Rolland, Jannick P.

    2010-01-01

    Three compact and efficient designs are proposed to deliver an average irradiance of 50 mW/cm2 with spatial uniformity well above 90% over a 25 mm2 target area for photodynamic therapy of the oral cavity. The main goal is to produce uniform illumination on the target while limiting irradiation of healthy tissue, thus overcoming the need of shielding the whole oral cavity and greatly simplifying the treatment protocol. The first design proposed consists of a cylindrical diffusing fiber placed in a tailored reflector derived from the edge-ray theorem with dimensions 5.5 × 7.2 × 10 mm3; the second device combines a fiber illuminator and a lightpipe with dimensions 6.8 × 6.8 × 50 mm3; the third design, inspired by the tailored reflector, is based on a cylindrical diffusing fiber and a cylinder reflector with dimensions 5 × 10 × 11 mm3. A prototype for the cylinder reflector was built that provided the required illumination for photodynamic therapy of the oral cavity, producing a spatial uniformity on the target above 94% and an average irradiance of 51 mW/cm2 for an input power of 70 mW. PMID:21157577

  18. Rf accelerating cavity for COSY

    NASA Astrophysics Data System (ADS)

    Fougeron, C.; Clerc, G.; Langlois, M.; Tardy, M. P.

    1993-04-01

    Based on the long experience of the Saclay's Laboratoire National Saturne in the field of radio frequency cavities, a pool constituted of LNS and Thomson Tubes Electroniques has built and delivered the rf system ( h = 1) for the COSY synchrotron of KFA-Jülich. The characteristics of this system are described. The paper will also present other realizations in this field, and new developments towards very wide band cavities for heavy ion synchrotrons.

  19. Diseases of the Oral Cavity

    Microsoft Academic Search

    Zohra Zaidi; Sean W. Lanigan

    \\u000a The oral cavity can provide valuable clues to cutaneous disorders, and should be included in every skin examination. A number\\u000a of skin diseases have oral manifestations, such as pemphigus, erythema multiforme, SLE, lichen planus, psoriasis, viral infections,\\u000a etc. Most of the lesions are in the form of ulcers or white patches.\\u000a \\u000a \\u000a The mucous membrane of the oral cavity is covered

  20. TEM observations of crack tip: cavity interactions

    SciTech Connect

    Horton, J.A.; Ohr, S.M.; Jesser, W.A.

    1981-01-01

    Crack tip-cavity interactions have been studied by performing room temperature deformation experiments in a transmission electron microscope on ion-irradiated type 316 stainless steel with small helium containing cavities. Slip dislocations emitted from a crack tip cut, sheared, and thereby elongated cavities without a volume enlargement. As the crack tip approached, a cavity volume enlargement occurred. Instead of the cavities continuing to enlarge until they touch, the walls between the cavities fractured. Fracture surface dimples do not correlate in size or density with these enlarged cavities.

  1. Bacterial penetration of restored cavities.

    PubMed

    Zivkovi?, S; Bojovi?, S; Pavlica, D

    2001-03-01

    The aim of this study was to assess the quality of the marginal seals of 7 restoratives by means of a bacterial penetration test in vitro. Sixty intact premolars and third molars that were scheduled for extraction were used in the test. There were 2 experimental groups of teeth, as follows: (1) A class V conventional cavity and a wedge erosion cavity were prepared on the buccal surface and the lingual surface, respectively, of each tooth. (2) A class V conventional cavity and a wedge erosion cavity were prepared on the buccal surface and the lingual surface, respectively, of each tooth with a completely removed enamel layer. The cavities were then reconstructed with different restorative materials. The quality of the marginal seals was evaluated by submerging the teeth in a bacterial suspension and incubating them in an anaerobic milieu at 37 degrees C for 20 hours. The teeth were subsequently processed for histologic data and bacterial staining. The best marginal sealing in both the wedge erosion and the class V cavities was provided by the Herculite/Optibond system and the Valux Plus/Scotchbond Multipurpose system. Bacterial penetration was slightly greater with the Luxat compomer and the Dyrect compomer, as well as with Vitremer glass ionomer cement and Fuji LC glass ionomer cement. The bacterial penetration test showed that the use of restorative material does not entirely eliminate microleakage. PMID:11250635

  2. Coupled-resonator vertical-cavity laser

    NASA Astrophysics Data System (ADS)

    Choquette, Kent D.; Chow, Weng W.; Hou, Hong Q.; Geib, Kent M.; Hammons, B. E.

    1998-04-01

    The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. We report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising form the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.

  3. Hydrophobic cavity formed by oligopeptide for doxorubicin delivery based on dendritic poly(L-lysine).

    PubMed

    Niidome, Takuro; Yamauchi, Hisayo; Takahashi, Kayo; Naoyama, Kenshiro; Watanabe, Kazuto; Mori, Takeshi; Katayama, Yoshiki

    2014-01-01

    To deliver anti-cancer drugs to tumors, a hydrophobic cavity was prepared in the dendritic molecule, dendritic poly(L-lysine) of sixth generation (KG6), which was used as a drug carrier. The dendritic molecule was modified with polyethylene glycol (PEG)-linked hydrophobic penta-phenylalanine or penta-alanine. The hydrophobic cavity was formed between the KG6 and PEG chains. The penta-phenylalanine peptide was better in encapsulating doxorubicin (DOX) in the cavity compared with penta-alanine. The loaded DOX was slowly released from the cavity, and it depended on pH. After intravenous injection, the DOX-loaded dendrimers accumulated in the tumor by the enhanced permeability and retention effect, and showed significant suppression of tumor growth without loss of body weight. These results indicate that hydrophobic oligopeptides can be used for forming a hydrophobic cavity in a dendritic molecule for delivery of anti-cancer drugs to tumor sites. PMID:25040893

  4. Cavity Alighment Using Beam Induced Higher Order Modes Signals in the TTF Linac

    SciTech Connect

    Ross, M.; Frisch, J.; Hacker, K.E.; Jones, R.M.; McCormick, D.; O'Connell, C.; Smith, T.; /SLAC; Napoly, O.; Paparella, R.; /DAPNIA, Saclay; Baboi, N.; Wendt, M.; /DESY

    2005-07-06

    Each nine cell superconducting (SC) accelerator cavity in the TESLA Test Facility (TTF) at DESY [1] has two higher order mode (HOM) couplers that efficiently remove the HOM power [2]. They can also provide useful diagnostic signals. The most interesting modes are in the first 2 cavity dipole passbands. They are easy to identify and their amplitude depends linearly on the beam offset from the cavity axis making them excellent beam position monitors (BPM). By steering the beam through an eight-cavity cryomodule, we can use the HOM signals to estimate internal residual alignment errors and minimize wakefield related beam emittance growth. We built and tested a time-domain based waveform recorder system that captures information from each mode in these two bands on each beam pulse. In this paper we present a preliminary experimental study of the single-bunch generated HOM signals at the TTF linac including estimates of cavity alignment precision and HOM BPM resolution.

  5. Active Cavity Radiometer (ACR)

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1988-01-01

    The objective of the Active Cavity Radiometer (ACR) experiment on the Atmospheric Laboratory for Applications and Science (ATLAS) mission is the measurement of the total solar irradiance with state-of-the-art accuracy and precision. This experiment is part of an ongoing program of space flight observations to study short- and long-term variations in the total solar output of optical energy. Precise observations of solar total irradiance provide information on the solar cycle and other long-term trends in solar output that are of climatological significance as well as short-term solar physics phenomena such as radiation anisotropy, active region structure, missing flux due to sunsports, bolometry of solar flares, global oscillations, coronal holes, and large-scale convective flows. The principal role of the ATLAS ACR observations will be in support of extended solar irradiance experiments on free-flying satellites. Annual in-flight comparison of observations by both ATLAS and free-flying experiments is an important part of sustaining the long-term precision of the climatological solar irradiance data base at the required + or - 0.1 percent level. Another role for ATLAS solar irradiance measurements will be establishment of the radiation scale at the solar total flux level in the International System of Units (SI). Two types of pyrheliometers, the ACR and SOLCON, will be directly intercompared during the ATLAS 1 mission. Addition of other sensors is planned for future reflights. Comparisons of solar observations by different pyrheliometers in the shuttle space environment will provide the most definitive experiment for determining their accuracy in defining the radiation scale at the solar total flux level.

  6. Human Capital and Economic Growth.

    ERIC Educational Resources Information Center

    Mincer, Jacob

    1984-01-01

    The framework of an aggregate production function shows that growth of human capital is both a condition and a consequence of economic growth. The concurrent growth and diffusion of human capital, involving production of new knowledge, appears necessary to ensure sustained economic development worldwide. (TE)

  7. Maximum energy of cosmic-ray particles accelerated by supernova remnant shocks in stellar wind cavities

    Microsoft Academic Search

    Heinrich J. Voelk; Peter L. Biermann

    1988-01-01

    Diffusive shock acceleration, balanced by adiabatic losses, leads readily to particle energies of more than 10 to the 15th eV in the case of a supernova shock freely expanding into a stellar wind cavity. This process accelerates particles early on out of stellar wind material which is often enriched in certain elements (isotopes), and may thus contribute to explain elemental

  8. 600-Hz linewidth short-linear-cavity fiber laser.

    PubMed

    Mo, Shupei; Huang, Xiang; Xu, Shanhui; Li, Can; Yang, Changsheng; Feng, Zhouming; Zhang, Weinan; Chen, Dongdan; Yang, Zhongmin

    2014-10-15

    We proposed a short-linear-cavity (SLC) fiber laser based on a virtual-folded-ring (VFR) resonator and a fiber Bragg grating Fabry-Perot filter. Spatial hole burning effect was reduced by retarding the polarization state of the counter-propagating light waves utilizing the VFR structure. The photon lifetime of the resonator was extended due to the multi-reflection inside the FBG FP, which increased the intra-cavity power and relatively suppressed the contribution of phase diffusion from spontaneous emission. The relaxation oscillation frequency is around 160 kHz due to the slow light effect. The linewidth of the SLC fiber laser was measured to be less than 600 Hz. PMID:25361093

  9. A Hot Cavity Laser Ion Source at IGISOL

    E-print Network

    M. Reponen; T. Kessler; I. D. Moore; S. Rothe; J. Äystö

    2008-12-08

    A development program is underway at the IGISOL (Ion Guide Isotope Separator On-Line) facility, University of Jyvaskyla, to efficiently and selectively produce low-energy radioactive ion beams of silver isotopes and isomers, with a particular interest in N=Z 94Ag. A hot cavity ion source has been installed, based on the FEBIAD (Forced Electron Beam Induced Arc Discharge) technique, combined with a titanium:sapphire laser system for selective laser ionization. The silver recoils produced via the heavy-ion fusion-evaporation reaction, 40Ca(58Ni, p3n)94Ag, are stopped in a graphite catcher, diffused, extracted and subsequently ionized using a three-step laser ionization scheme. The performance of the different components of the hot cavity laser ion source is discussed and initial results using stable 107,109Ag are presented.

  10. Estimating the geographic diffusion of the videocassette recorder market

    Microsoft Academic Search

    Yu-Min Chen; Hirokazu Takada

    1994-01-01

    The majority of studies concerning diffusion or product growth of consumer durables have treated the U.S. market as a whole and have applied the diffusion model on the assumption that the market exhibits a homogeneous response in its diffusion process. If the market is heterogeneous, however, an aggregate model entails a misspecification problem which could adversely affect the applicability and

  11. Doping optimization for ultra-high quality factor superconducting niobium cavities for particle acceleration

    NASA Astrophysics Data System (ADS)

    Vostrikov, Alexander; Romanenko, Alexander; Grassellino, Anna; Kim, Young-Kee

    2014-03-01

    Increasing quality factor of the fundamental mode in superconducting radio frequency (SRF) niobium cavities is vital for development of the future particle accelerator facilities, i.e. LCLS-II, Project X, ERLs, and ADS for nuclear energy and waste transmutation, since it directly affects the dissipated power in cavity walls. It has been discovered that doping of certain concentration of nitrogen into the surface of superconducting niobium significantly improves the quality factor of SRF cavities. We report the results of the nitrogen doping optimization guided by diffusion model and present two surface treatment procedures that allow achieving optimal value of nitrogen concentration at the surface of cavity: one with electropolishing required, another one without it.

  12. Numerical optimization of the radial dependence of effective emissivity in blackbody cylindrical cavities

    NASA Astrophysics Data System (ADS)

    De Lucas, Javier

    2014-10-01

    The effective emissivity of a blackbody with cylindrical geometry has a definite radial dependence, at the bottom cavity, which is a function of the surface intrinsic emissivity, cavity geometry (L/D) and the temperature gradient along the cylinder walls. The optimal use of large aperture blackbody cavities, particularly in thermal imager calibration applications or for the characterization of size-of-source effect of radiation thermometers for example, requires quite precise control of the thermal gradient, in order to achieve sources as uniform as possible in effective emissivity, over the complete aperture. In this paper, we present a numerical model in which the radial profile of effective emissivity is optimized, by means of the theoretical modification of the temperature gradients in a cylindrical diffuse cavity. The distribution functions of secondary absorption impacts are defined and the criteria for a suitable choice of experimentally realizable temperature gradients are presented, including the uncertainty analysis.

  13. 3D cavity detection technique and its application based on cavity auto scanning laser system

    Microsoft Academic Search

    Xi-ling Liu; Xi-bing Li; Fa-ben Li; Guo-yan Zhao; Yu-hui Qin

    2008-01-01

    Ground constructions and mines are severely threatened by underground cavities especially those unsafe or inaccessible ones.\\u000a Safe and precise cavity detection is vital for reasonable cavity evaluation and disposal. The conventional cavity detection\\u000a methods and their limitation were analyzed. Those methods cannot form 3D model of underground cavity which is used for instructing\\u000a the cavity disposal; and their precisions in

  14. Traveling wave model of a multimode Fabry-Perot laser in free running and external cavity configurations

    SciTech Connect

    Homar, M.; San Miguel, M. [Univ. of Arizona, Tucson, AZ (United States). Arizona Center for Mathematical Sciences] [Univ. of Arizona, Tucson, AZ (United States). Arizona Center for Mathematical Sciences; [Univ. de les Illes Balears, Palma de Mallorca (Spain). Dept. de Fisica; Moloney, J.V. [Univ. of Arizona, Tucson, AZ (United States). Arizona Center for Mathematical Sciences] [Univ. of Arizona, Tucson, AZ (United States). Arizona Center for Mathematical Sciences

    1996-03-01

    The authors report the results of a numerical study of multimode behavior of a Fabry-Perot laser. The model is based on traveling-wave equations for the slowly varying amplitudes of the counterpropagating waves in the cavity, coupled to equations for spatially dependent population inversion and polarization of a two-level active medium. Variations in the material variables on the scale of a wavelength are taken into account by means of an expansion in a Fourier series. Results are given for typical semiconductor laser parameters. Spatially distributed spontaneous emission noise and carrier diffusion are taken into account. The competing roles of Spatial Hole Burning (SHB), spontaneous emission noise, and carrier diffusion in determining multimode behavior are elucidated; with no carrier diffusion, spontaneous emission noise excites a large number of modes close to threshold, while SHB leads to a fixed number of significant lasing modes well above threshold. Carrier diffusion washes out the gratings in the material variables, and the resulting strengthening of the inter-mode coupling (cross-saturation) restores dominant single-mode emission well above threshold. They have also studied the effects of optical feedback and opportunities for mode selection with short external cavities; for an external cavity much shorter than the laser cavity length and a small field amplitude reflectivity coefficient, a single mode can be selected. For a large reflectivity coefficient, two groups of intracavity modes separated by the external cavity mode interspacing are selected. For an external cavity with a round trip time half that of the laser cavity, the laser can be forced with modest feedback to operate on two modes that are both quasiresonant with the external cavity. Mode selection is not found, even for weak feedback, when the external mode spacing is about 90% of the laser mode spacing.

  15. Selective advantage of diffusing faster.

    PubMed

    Pigolotti, Simone; Benzi, Roberto

    2014-05-01

    We study a stochastic spatial model of biological competition in which two species have the same birth and death rates, but different diffusion constants. In the absence of this difference, the model can be considered as an off-lattice version of the voter model and presents similar coarsening properties. We show that even a relative difference in diffusivity on the order of a few percent may lead to a strong bias in the coarsening process favoring the more agile species. We theoretically quantify this selective advantage and present analytical formulas for the average growth of the fastest species and its fixation probability. PMID:24856726

  16. Analog detection for cavity lifetime spectroscopy

    DOEpatents

    Zare, Richard N. (Stanford, CA); Harb, Charles C. (Palo Alto, CA); Paldus, Barbara A. (Mountain View, CA); Spence, Thomas G. (Palo Alto, CA)

    2001-05-15

    An analog detection system for determining a ring-down rate or decay rate 1/.tau. of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

  17. Analog detection for cavity lifetime spectroscopy

    DOEpatents

    Zare, Richard N. (Stanford, CA); Harb, Charles C. (Palo Alto, CA); Paldus, Barbara A. (Mountain View, CA); Spence, Thomas G. (Palo Alto, CA)

    2003-01-01

    An analog detection system for determining a ring-down rate or decay rate 1/.tau. of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

  18. Progress on a Be Cavity Design

    SciTech Connect

    Li, D.; Palmer, R.; Stratakis, D.; Virostek, S.; Zisman, Michael S.

    2010-12-24

    Previous RF experiments with normal-conducting cavities have demonstrated that there is a significant degradation in maximum gradient when the cavity is subjected to a strong axial magnetic field. We have developed a model suggesting that a cavity with beryllium walls may perform better than copper cavities. In this paper we outline the issues that led us to propose fabricating a Be-wall cavity. We also discuss a concept for fabricating such a cavity and mention some of the manufacturing issues we expect to face.

  19. Holographic Graphene in a Cavity

    E-print Network

    Nick Evans; Peter A. R. Jones

    2014-07-11

    The effective strength of EM interactions can be controlled by confining the fields to a cavity and these effects might be used to push graphene into a strongly coupled regime. We study the similar D3/probe D5 system on a compact space and discuss the gravity dual for a cavity between two mirrors. We show that the introduction of a conformal symmetry breaking length scale introduces a mass gap on a single D5 sheet. Bilayer configurations display exciton condensation between the sheets. There is a first order phase transition away from the exciton condensate if a strong enough magnetic field is applied. We finally map out the phase structure of these systems in a cavity with the presence of mirror reflections of the probes - a mass gap may form through exciton condensation with the mirror image.

  20. Acute subendocardial infarction with diffuse intense Tc-99m PYP uptake and minimal Tl-201 abnormality.

    PubMed

    Taki, J; Taki, S; Ichiyanagi, K; Akashi, Y; Hisada, K

    1992-08-01

    Tc-99m PYP scintigraphy performed on a patient with severe anterior chest pain showed diffuse intense uptake with central decreased activity corresponding to the left ventricular cavity. Tl-201 myocardial perfusion scintigraphy at rest revealed a minimal perfusion abnormality with decreased apical uptake in the lateral view. Because of these findings, diffuse subendocardial infarction was suggested. PMID:1387053

  1. Measurement of thermal diffusivity of air using photopyroelectric interferometry

    E-print Network

    Mandelis, Andreas

    the thermal diffusivity of ambient gases with optimal precision is introduced. The technique is based on destructive PPE interferometric detection inside a thermal-wave resonant cavity with an optically transparent-to-noise ratio and the measurement dynamic range and precision by suppressing the large optically transmitted

  2. Field Fluctuation Spectroscopy in a Reverberant Cavity with Moving Scatterers

    NASA Astrophysics Data System (ADS)

    de Rosny, Julien; Roux, Philippe; Fink, Mathias; Page, J. H.

    2003-03-01

    We report a study of transient ultrasonic waves inside a reverberant cavity containing moving scatterers. We show that the elastic mean free path and the dynamics of the scatterers govern the evolution of the autocorrelation of acoustic wave field. A parallel is established between these results and a closely related technique, diffusing acoustic wave spectroscopy. Excellent agreement is found between experiment and theory for a moving stainless steel ball in a water tank, thereby elucidating the underlying physics, and a potential application, fish monitoring inside aquariums, is demonstrated.

  3. Multipactor simulations in superconducting cavities

    SciTech Connect

    Gonin, I.; Solyak, N.; /Fermilab; DeFord, J.; Held, B.

    2007-06-01

    The multipactor (MP) is a well-known phenomenon. The existence of resonant trajectories can lead to electron avalanche under certain field levels and surface conditions, and can limit the performance of high power superconducting (SC) radio-frequency (RF) devices. In this paper we describe features of the ANALYST particle tracking code PT3P developed for MP simulations in real 3D RF structures, such as cavities, couplers, RF windows etc. Also we present the results of MP simulations in HOM couplers of TESLA, SNS and FNAL 3rd harmonic cavities. We discuss the comparison of simulations with experimental results.

  4. Effects of cavities in the bacterial reaction center

    SciTech Connect

    Schiffer, M.; Deng, Y.-L.; Marrufo, A.; Hanson, D.K.

    1995-12-31

    A site-specific double mutant of Rhodobacter capsulatus, in which the large aromatic residues M208Tyr and L181Phe in the interior of the photosynthetic reaction center (RC) complex were replaced by smaller theonine residues, showed a dramatic reduction in the number of assembled complexes and was incapable of photosynthetic growth. The cavity created by the smaller side chains interferes mostly with the assembly of the complex. Phenotypic revertants were recovered in which a spontaneous second-site mutation restored photocompetence in the presence of the original site-specific mutations. In these strains, an Ala to Pro substitution in neighboring transmembrane helix (at M271) resulted in an increased yield of RC complexes. To test the hypothesis that the original phenotype was due to a cavity, other mutants were constructed where L180Phe and M207Leu were replaced with alanines that created similar-sized voids at other positions in the membrane-spanning interior. The L180Ala-M207A mutant had the same phenotype. Coupling of the above proline substitution to these new cavity mutants also resulted in photocompetant strains that carry increased levels of RC complexes. Therefore, the proline substitution at M271 serves as a global suppressor of the phenotype caused by these internal cavities.

  5. Stages of Lip and Oral Cavity Cancer

    MedlinePLUS

    ... ongoing clinical trials is available from the NCI Web site . Stages of Lip and Oral Cavity Cancer Key Points After lip and oral cavity cancer has been diagnosed, tests are done to find out if cancer cells ...

  6. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...3260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3260 Cavity varnish. (a) Identification. Cavity...

  7. Organized Oscillations of Initially-Turbulent Flow Past a Cavity

    SciTech Connect

    J.C. Lin; D. Rockwell

    2002-09-17

    Flow past an open cavity is known to give rise to self-sustained oscillations in a wide variety of configurations, including slotted-wall, wind and water tunnels, slotted flumes, bellows-type pipe geometries, high-head gates and gate slots, aircraft components and internal piping systems. These cavity-type oscillations are the origin of coherent and broadband sources of noise and, if the structure is sufficiently flexible, flow-induced vibration as well. Moreover, depending upon the state of the cavity oscillation, substantial alterations of the mean drag may be induced. In the following, the state of knowledge of flow past cavities, based primarily on laminar inflow conditions, is described within a framework based on the flow physics. Then, the major unresolved issues for this class of flows will be delineated. Self-excited cavity oscillations have generic features, which are assessed in detail in the reviews of Rockwell and Naudascher, Rockwell, Howe and Rockwell. These features, which are illustrated in the schematic of Figure 1, are: (i) interaction of a vorticity concentration(s) with the downstream corner, (ii) upstream influence from this corner interaction to the sensitive region of the shear layer formed from the upstream corner of the cavity; (iii) conversion of the upstream influence arriving at this location to a fluctuation in the separating shear layer; and (iv) amplification of this fluctuation in the shear layer as it develops in the streamwise direction. In view of the fact that inflow shear-layer in the present investigation is fully turbulent, item (iv) is of particular interest. It is generally recognized, at least for laminar conditions at separation from the leading-corner of the cavity, that the disturbance growth in the shear layer can be described using concepts of linearized, inviscid stability theory, as shown by Rockwell, Sarohia, and Knisely and Rockwell. As demonstrated by Knisely and Rockwell, on the basis of experiments interpreted with the aid of linearized theory, not only the fundamental component of the shear layer instability may be present, but a number of additional, primarily lower frequency components can exist as well. In fact, the magnitude of these components can be of the same order as the fundamental component. These issues have not been addressed for the case of a fully-turbulent in-flow and its separation from the leading corner of the cavity.

  8. Quench Localization in Superconducting Radio-frequency (SRF) Cavities

    E-print Network

    Baltisberger, Jay H.

    Quench Localization in Superconducting Radio-frequency (SRF) Cavities Ramesh Adhikari Lee Teng distance. Solution - Superconduting Radio-Frequency Cavities Ramesh Adhikari Quench Localization in SRF Cavities #12;Superconducting Radio-frequency Cavity (SRF) Accelerating structures for next generation

  9. General Information about Paranasal Sinus and Nasal Cavity Cancer

    MedlinePLUS

    ... About Paranasal Sinus and Nasal Cavity Cancer Key Points Paranasal sinus and nasal cavity cancer is a ... of Paranasal Sinus and Nasal Cavity Cancer Key Points After paranasal sinus and nasal cavity cancer has ...

  10. Paranasal Sinus and Nasal Cavity Cancer (Treatment Options by Stage)

    MedlinePLUS

    ... About Paranasal Sinus and Nasal Cavity Cancer Key Points Paranasal sinus and nasal cavity cancer is a ... of Paranasal Sinus and Nasal Cavity Cancer Key Points After paranasal sinus and nasal cavity cancer has ...

  11. An economical wireless cavity-nest viewer

    Microsoft Academic Search

    Daniel P. Huebner; Sarah R. Hurteau

    2007-01-01

    Inspection of cavity nests and nest boxes is often required during studies of cavity-nesting birds, and fiberscopes and pole-mounted video cameras are sometimes used for such inspection. However, the cost of these systems may be prohibitive for some potential users. We describe a user-built, wireless cavity viewer that can be used to access cavities as high as 15 m and

  12. Superconducting Niobium Cavity Measurements at SLAC

    Microsoft Academic Search

    M. A. Allen; Z. D. Farkas; H. A. Hogg; E. W. HoytandP; P. B. Wilson

    1971-01-01

    The program of measurements at SLAC on superconducting niobium cavities is described. Results for TE and TM mode X-band cavities are presented. An RF magnetic breakdown field of 960 gauss and Q values greater than 1011 were measured for an electron beam welded TE011 mode cavity at 10.5 GHz. The best result for a TM mode cavity was a Q

  13. Large-mode enhancement cavities.

    PubMed

    Carstens, Henning; Holzberger, Simon; Kaster, Jan; Weitenberg, Johannes; Pervak, Volodymyr; Apolonski, Alexander; Fill, Ernst; Krausz, Ferenc; Pupeza, Ioachim

    2013-05-01

    In passive enhancement cavities the achievable power level is limited by mirror damage. Here, we address the design of robust optical resonators with large spot sizes on all mirrors, a measure that promises to mitigate this limitation by decreasing both the intensity and the thermal gradient on the mirror surfaces. We introduce a misalignment sensitivity metric to evaluate the robustness of resonator designs. We identify the standard bow-tie resonator operated close to the inner stability edge as the most robust large-mode cavity and implement this cavity with two spherical mirrors with 600 mm radius of curvature, two plane mirrors and a round trip length of 1.2 m, demonstrating a stable power enhancement of near-infrared laser light by a factor of 2000. Beam radii of 5.7 mm × 2.6 mm (sagittal × tangential 1/e(2) intensity radius) on all mirrors are obtained. We propose a simple all-reflective ellipticity compensation scheme. This will enable a significant increase of the attainable power and intensity levels in enhancement cavities. PMID:23670017

  14. Cavity Enhanced Velocity Modulation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Siller, Brian; Mills, Andrew; McCall, Benjamin J.

    2010-06-01

    Velocity modulation spectroscopy has traditionally been used with a unidirectional multipass White cell to obtain several passes through a plasma in order to obtain strong signals from the absorption of ions, but the total number of passes allowed by this type of setup is limited to ˜8. By placing an optical cavity around an N_2^+ plasma and locking the cavity to a Ti:Sapphire laser, the effective number of passes has been increased to several hundred. Demodulating the signal from the transmitted light at twice the plasma frequency (due to the symmetric nature of the cavity) gives a 2nd derivative lineshape for ions and a Gaussian lineshape for excited neutrals. N_2^+ and N_2^* have been observed to be 78° out of phase with one another. The different lineshapes and phases allow for discrimination and separation of the ion and neutral signals. The high intensity laser light within the cavity causes the transitions to saturate, which allows for the observation of lamb dips; this opens the door to sub-Doppler spectroscopy, as well as to studies of ion-neutral collisional rate coefficients.

  15. Call for Papers: Cavity QED

    Microsoft Academic Search

    W. Lange; J.-M. Gerard

    2003-01-01

    Cavity QED interactions of light and matter have been investigated in a wide range of systems covering the spectrum from microwaves to optical frequencies, using media as diverse as single atoms and semiconductors. Impressive progress has been achieved technologically as well as conceptually. This topical issue of Journal of Optics B: Quantum and Semiclassical Optics is intended to provide a

  16. A Micromachined Tunable Cavity Resonator

    Microsoft Academic Search

    D. Mercier; M. Chatras; J. C. Orlianges; C. Champeaux; A. Catherinot; P. Blondy; D. Cros; J. Papapolymerou

    2003-01-01

    This paper focuses on a tunable resonator fabricated using bulk and surface micro-machining techniques. The resonator consists of a silicon micro-machined metalized cavity coupled with a MEMS bridge capacitor for tunability purposes. The resonator is excited using coplanar waveguide lines to avoid losses from transitions and facilitate measurements. The unloaded quality factor of the device is about 150 depending on

  17. ADPF spoke cavity cryomodule concept

    SciTech Connect

    Kelley, J. P. (John Patrick); Roybal, P. L. (Phillip L.); La Fave, R. P. (Richard P.); Waynert, J. A. (Joseph A.); Schrage, D. L. (Dale L.); Schmierer, E. N. (Eric N.); Krawczyk, F. L. (Frank L.); Garnett, R. W. (Robert W.)

    2001-01-01

    The Accelerator Driven Test Facility (ADTF) is being developed as a reactor concepts test bed for transmutation of nuclear waste. A 13.3 mA continuous-wave (CW) proton beam will be accelerated to 600 MeV and impinged on a spallation target. The subsequent neutron shower is used to create a nuclear reaction within a subcritical assembly of waste material that reduces the waste half-life from the order of 10{sup 5} years to 10{sup 2} years. Additionally, significant energy is produced that can be used to generate electrical power. The ADTF proton accelerator consists of room-temperature (RT) structures that accelerate the beam to 6.7-MeV and superconducting (SC) elements that boost the beam's energy to 600-MeV. Traditional SC elliptical cavities experience structural difficulties at low energies due to their geometry. Therefore, stiff-structured SC spoke cavities have been adopted for the energy range between 6.7 and 109 MeV. Elliptical cavities are used at the higher energies. This paper describes a multi-spoke-cavity cryomodule concept for ADTF.

  18. Cavity nano-optomechanics: a nanomechanical system in a high finesse optical cavity

    E-print Network

    Ludwig-Maximilians-Universität, München

    to nanomechanical systems, cavity nano-optomechanics should advance into precision displacement measurements nearCavity nano-optomechanics: a nanomechanical system in a high finesse optical cavity Sebastian of interest, as recent reviews report.1, 2 This coupling is enhanced when confining light in an optical cavity

  19. Optical cavity enhancement of light-sound interaction in acoustic phonon cavities

    Microsoft Academic Search

    P. Lacharmoise; A. Fainstein; B. Jusserand; V. Thierry-Mieg

    2004-01-01

    We describe a device that has a resonant cavity for acoustic phonons embedded inside an optical cavity. This double cavity structure is a resonator for acoustical phonons and enhances the interaction between sound and light. We discuss the design and material parameters relevant for the optimization of the acoustic phonon cavities, and we present Raman scattering experiments on GaAs\\/AlAs structures

  20. Discrete wavelength-locked external cavity laser

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S. (Inventor); Silver, Joel A. (Inventor)

    2005-01-01

    An external cavity laser (and method of generating laser light) comprising: a laser light source; means for collimating light output by the laser light source; a diffraction grating receiving collimated light; a cavity feedback mirror reflecting light received from the diffraction grating back to the diffraction grating; and means for reliably tuning the external cavity laser to discrete wavelengths.

  1. SRF CAVITY STIFFENING BY THERMAL SPRAYING

    Microsoft Academic Search

    S. Bousson; M. Fouaidy; H. Gassot; T. Junquera; J. Lesrel

    In this paper, we report on the advances in the new stiffening method using a thermally sprayed copper layer onto bulk niobium cavities. This technique could be used either for replacing the actual EB welded stiffening rings in TESLA cavities, or to fabricate Superconducting Radio Frequency (SRF) proton cavities at low ? with reduced niobium thickness. The latest measurements performed

  2. Computer codes for RF cavity design

    SciTech Connect

    Ko, K.

    1992-08-01

    In RF cavity design, numerical modeling is assuming an increasingly important role with the help of sophisticated computer codes and powerful yet affordable computers. A description of the cavity codes in use in the accelerator community has been given previously. The present paper will address the latest developments and discuss their applications to cavity toning and matching problems.

  3. Optimisation of laser linewidth and cavity alignment in off-axis cavity-enhanced absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Kasyutich, Vasili L.; Sigrist, Markus W.

    2015-07-01

    Laser linewidth affects baseline mode structured variations and hence measurement absorption sensitivity in off-axis cavity enhanced absorption spectroscopy with a continuous-wave tunable laser and a stable optical cavity formed by two high reflectivity mirrors. Cavity transmittances have been calculated for various laser linewidths and different optical beam re-entrant conditions for the cavity when overlapping of the optical beams occurs on the cavity mirrors after a finite number of beam round trips within the cavity. It is shown that in order to achieve maximum absorption sensitivity both a specific laser linewidth and specific arrangement of the optical cavity have to be selected and defined using the proposed approach.

  4. LINEAR DIFFUSION Erkut Erdem

    E-print Network

    Erdem, Erkut

    LINEAR DIFFUSION Erkut Erdem Hacettepe University February 24th, 2012 CONTENTS 1 Linear Diffusion 1 2 Appendix - The Calculus of Variations 5 References 6 1 LINEAR DIFFUSION The linear diffusion (heat (noisy) input image and u(x, t) be initialized with u(x, 0) = u0(x) = f (x). Then, the linear diffusion

  5. NONLINEAR DIFFUSION Erkut Erdem

    E-print Network

    Erdem, Erkut

    NONLINEAR DIFFUSION Erkut Erdem Hacettepe University March 9th, 2013 CONTENTS 1 Perona-Malik Type Nonlinear Diffusion 1 2 Total Variation (TV) Regularization 5 3 Edge Enhancing Diffusion 8 References 11 1 PERONA-MALIK TYPE NONLINEAR DIFFUSION The main theory behind nonlinear diffusion models is to use

  6. Technology Diffusion and Aggregate Dynamics

    Microsoft Academic Search

    David Andolfatto; Glenn M. MacDonald

    1998-01-01

    This paper develops and analyzes a macroeconomic model in which aggregate growth and fluctuations arise from the discovery and diffusion of new technologies; there are no exogenous aggregate shocks. The temporal behavior of aggregates is driven by individuals' efforts to innovate and\\/or make use of others' innovations. Parameters describing preferences, production possibilities, and learning technologies are estimated using post-war U.S.

  7. Transient Diffusion of Beryllium and Silicon in Gallium Arsenide

    NASA Astrophysics Data System (ADS)

    Haddara, Yaser M.; Bravman, John C.

    1998-08-01

    Transient diffusion is an increasingly important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant, as well as the sources of transient effects under a given set of experimental conditions. Theoretical, experimental, and simulation results were obtained to understand transient diffusivities of beryllium and silicon in grown-in and implanted samples. In implanted samples, by understanding implant damage and modeling the evolution of point defect populations, the observed transient effects can be explained. Such phenomena cannot account for the time-dependent diffusivity observed when the dopant is introduced during molecular beam epitaxial growth. Transient diffusivities for grown-in beryllium were investigated and explained by modeling the evolution of point defect populations as they increase beyond their equilibrium levels at the growth temperature to achieve equilibrium at the anneal temperature.

  8. Status of the ILC Crab Cavity Development

    SciTech Connect

    Burt, G.; Dexter, A.; /Cockcroft Inst. Accel. Sci. Tech.; Beard, C.; Goudket, P.; McIntosh, P.; /Daresbury; Bellantoni, L.; /Fermilab; Grimm, T.; Li, Z.; Xiao, L.; /SLAC

    2011-10-20

    The International Linear Collider (ILC) will require two dipole cavities to 'crab' the electron and positron bunches prior to their collision. It is proposed to use two 9 cell SCRF dipole cavities operating at a frequency of 3.9 GHz, with a transverse gradient of 3.8MV/m in order to provide the required transverse kick. Extensive numerical modelling of this cavity and its couplers has been performed. Aluminium prototypes have been manufactured and tested to measure the RF properties of the cavity and couplers. In addition single cell niobium prototypes have been manufactured and tested in a vertical cryostat. The International Collider (ILC) [1] collides bunches of electrons and positrons at a crossing angle of 14 mrad. The angle between these bunches causes a loss in luminosity due to geometric effects [2]. The luminosity lost from this geometric effect can be recovered by rotating the bunches into alignment prior to collision. One possible method of rotating the bunches is to use a crab cavity [3]. A crab cavity is a transverse defecting cavity, where the phase of the cavity is such that the head and tail of the bunch receive equal and opposite kicks. As the bunches are only 500 nm wide in the horizontal plane, the cavity phase must be strictly controlled to avoid the bunch centre being deflected too much. In order to keep the phase stability within the required limits it is required that the cavity be superconducting to avoid thermal effects in both the cavity and its RF source. At the location of the crab cavity in the ILC there is only 23 cm separation between the centre of the cavity and the extraction line, hence the cavity must be small enough to fit in this space. This, along with the difficulty of making high frequency SRF components, set the frequency of the cavity to 3.9 GHz.

  9. Optical Material Characterization Using Microdisk Cavities

    NASA Astrophysics Data System (ADS)

    Michael, Christopher P.

    Since Jack Kilby recorded his "Monolithic Idea" for integrated circuits in 1958, microelectronics companies have invested billions of dollars in developing the silicon material system to increase performance and reduce cost. For decades, the industry has made Moore's Law, concerning cost and transistor density, a self-fulfilling prophecy by integrating technical and material requirements vertically down their supply chains and horizontally across competitors in the market. At recent technology nodes, the unacceptable scaling behavior of copper interconnects has become a major design constraint by increasing latency and power consumption---more than 50% of the power consumed by high speed processors is dissipated by intrachip communications. Optical networks at the chip scale are a potential low-power high-bandwidth replacement for conventional global interconnects, but the lack of efficient on-chip optical sources has remained an outstanding problem despite significant advances in silicon optoelectronics. Many material systems are being researched, but there is no ideal candidate even though the established infrastructure strongly favors a CMOS-compatible solution. This thesis focuses on assessing the optical properties of materials using microdisk cavities with the intention to advance processing techniques and materials relevant to silicon photonics. Low-loss microdisk resonators are chosen because of their simplicity and long optical path lengths. A localized photonic probe is developed and characterized that employs a tapered optical-fiber waveguide, and it is utilized in practical demonstrations to test tightly arranged devices and to help prototype new fabrication methods. A case study in AlxGa1-xAs illustrates how the optical scattering and absorption losses can be obtained from the cavity-waveguide transmission. Finally, single-crystal Er2O3 epitaxially grown on silicon is analyzed in detail as a potential CMOS-compatable gain medium due to its high Er3+ density and the control offered by the precise epitaxy. The growth and fabrication methods are discussed. Spectral measurements at cryogenic and room temperatures show negligible background losses and resonant Er3+ absorption strong enough to produce cavity-polaritons that persist to above 361 K. Cooperative relaxation and upconversion limit the optical performance in the telecommunications bands by transferring the excitations to quenching sites or by further exciting the ions up to visible transitions. Future prospects and alternative applications for Er2O3 and other epitaxial rare-earth oxides are also considered.

  10. Deterministic and Robust Entanglement of Nitrogen Vacancy Centers using Low-Q Photonic Crystal Cavities

    E-print Network

    Janik Wolters; Julia Kabuss; Andreas Knorr; Oliver Benson

    2014-06-19

    We propose an experiment to generate deterministic entanglement between separate nitrogen vacancy (NV) centers mediated by the mode of a photonic crystal cavity. Using numerical simulations the applicability and robustness of the entanglement operation to parameter regimes achievable with present technology is investigated. We find that even with moderate cavity Q-factors of $10^{4}$ a concurrence of $c>0.6$ can be achieved within a time of $t_{max}\\approx150$~ns, while Q-factors of $10^{5}$ promise $c>0.8$. Most importantly, the investigated scheme is relative insensitive to spectral diffusion and differences between the optical transitions frequencies of the used NV centers.

  11. Differential ultrafast all-optical switching of the resonances of a micropillar cavity

    SciTech Connect

    Thyrrestrup, Henri, E-mail: h.t.nielsen@utwente.nl; Yüce, Emre; Ctistis, Georgios; Vos, Willem L. [Complex Photonic Systems (COPS), MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede (Netherlands); Claudon, Julien; Gérard, Jean-Michel, E-mail: jean-michel.gerard@cea.fr [University Grenoble Alpes, INAC-SP2M, Nanophysics and Semiconductors Lab, F-38000 Grenoble (France); CEA, INAC-SP2M, Nanophysics and Semiconductors Lab, F-38000 Grenoble (France)

    2014-09-15

    We perform frequency- and time-resolved all-optical switching of a GaAs-AlAs micropillar cavity using an ultrafast pump-probe setup. The switching is achieved by two-photon excitation of free carriers. We track the cavity resonances in time with a high frequency resolution. The pillar modes exhibit simultaneous frequency shifts, albeit with markedly different maximum switching amplitudes and relaxation dynamics. These differences stem from the non-uniformity of the free carrier density in the micropillar, and are well understood by taking into account the spatial distribution of injected free carriers, their spatial diffusion and surface recombination at micropillar sidewalls.

  12. Reconfigurable microfluidic photonic crystal slab cavities.

    PubMed

    Smith, Cameron L; Bog, Uwe; Tomljenovic-Hanic, Snjezana; Lee, Michael W; Wu, Darran K C; O'Faolain, Liam; Monat, Christelle; Grillet, Christian; Krauss, Thomas F; Karnutsch, Christian; McPhedran, Ross C; Eggleton, Benjamin J

    2008-09-29

    We demonstrate the spectral and spatial reconfigurability of photonic crystal double-heterostructure cavities in silicon by microfluidic infiltration of selected air holes. The lengths of the microfluidic cavities are changed by adjusting the region of infiltrated holes in steps of several microns. We systematically investigate the spectral signature of these cavities, showing high Q-factor resonances for a broad range of cavity lengths. The fluid can be removed by immersing the device in toluene, offering complete reconfigurability. Our cavity writing technique allows for tolerances in the infiltration process and provides flexibility as it can be employed at any time after photonic crystal fabrication. PMID:18825225

  13. Microwave energy storage in resonant cavities

    SciTech Connect

    Alvarez, R.A.

    1983-02-01

    One method of generating short, high-power microwave pulses is to store rf energy in a resonant cavity over a relatively long fill time and extract is rapidly. A power gain roughly equal to the ratio of fill time to extraction time can be obtained. During the filling of a resonant cavity some of the energy is lost in heating the cavity walls, and some will generally be reflected at the input coupling of the cavity. In this paper we discuss the time dependence of the stored energy and related quantities and the way in which it depends on the coupling of the source to the cavity.

  14. Vented Cavity Radiant Barrier Assembly And Method

    DOEpatents

    Dinwoodie, Thomas L. (Piedmont, CA); Jackaway, Adam D. (Berkeley, CA)

    2000-05-16

    A vented cavity radiant barrier assembly (2) includes a barrier (12), typically a PV module, having inner and outer surfaces (18, 22). A support assembly (14) is secured to the barrier and extends inwardly from the inner surface of the barrier to a building surface (14) creating a vented cavity (24) between the building surface and the barrier inner surface. A low emissivity element (20) is mounted at or between the building surface and the barrier inner surface. At least part of the cavity exit (30) is higher than the cavity entrance (28) to promote cooling air flow through the cavity.

  15. Parallel flow diffusion battery

    DOEpatents

    Yeh, H.C.; Cheng, Y.S.

    1984-01-01

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  16. Parallel flow diffusion battery

    DOEpatents

    Yeh, Hsu-Chi (Albuquerque, NM); Cheng, Yung-Sung (Albuquerque, NM)

    1984-08-07

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  17. Experimental determination of the critical cavity radius in Fe-10% Cr for ion irradiation

    SciTech Connect

    Horton, L.L.; Mansur, L.K.

    1984-01-01

    An ion bombardment experiment was designed to investigate the minimum critical radius, r/sub c/sup c*/, for the ferritic alloy Fe-10% Cr. Specimens were implanted with 300 appM Helium, annealed, and then irradiated to 30 dpa at 850K with 4-MeV Fe/sup 2 +/ ions. The specimens contained a bimodal cavity distribution consisting of a population of larger cavities (average radius 7.6 nm) and a population of smaller cavities (average radius 1.2 nm). The upper cut-off of the cavity radii for the smaller cavities, 2.5 nm, is interpreted as r/sub c/sup c*/. Theoretical calculations of r/sub c/sup c*/ for physically allowable combinations of bias, surface energy, vacancy migration energy, and vacancy formation energy and entropy were performed using the measured minimum critical radius and microstructural data. Thus, an indirect determination of these fundamental parameters was made for this alloy. The results suggest that a bias of approx. 0.2 is reasonable. An assessment of the possible values of the other fundamental parameters is given. In addition, the low irradiation-induced dislocation density (1 x 10/sup 13/m/sup -2/), which results in the ratio of the dislocation and cavity sink strengths, Q, being much less than unity, may be partially responsible for the low cavity growth rate in this alloy.

  18. Relationship between thermal convection intensity and aspect ratio of two triangular cavities inscribed in horizontal rectangular cavities

    Microsoft Academic Search

    El Hassan Ridouane; Antonio Campo

    2006-01-01

    Purpose – Sets out to discuss laminar free convection characteristics of air confined to a square cavity and a horizontal rectangular cavity (aspect ratio A=2) along with the viable isosceles triangular cavities and right-angle triangular cavities that may be inscribed inside the two original cavities. Design\\/methodology\\/approach – The three distinct cavities shared the base wall as the heated wall, while

  19. Control of Cavity Resonance Using Oscillatory Blowing

    NASA Technical Reports Server (NTRS)

    Scarfe, Alison Lamp; Chokani, Ndaona

    2000-01-01

    The near-zero net mass oscillatory blowing control of a subsonic cavity flow has been experimentally investigated. An actuator was designed and fabricated to provide both steady and oscillatory blowing over a range of blowing amplitudes and forcing frequencies. The blowing was applied just upstream of the cavity front Wall through interchangeable plate configurations These configurations enabled the effects of hole size, hole shape, and blowing angle to be examined. A significant finding is that in terms of the blowing amplitude, the near zero net mass oscillatory blowing is much more effective than steady blowing; momentum coefficients Lip two orders of magnitude smaller than those required for steady blowing are sufficient to accomplish the same control of cavity resonance. The detailed measurements obtained in the experiment include fluctuating pressure data within the cavity wall, and hot-wire measurements of the cavity shear layer. Spectral and wavelet analysis techniques are applied to understand the dynamics and mechanisms of the cavity flow with control. The oscillatory blowing, is effective in enhancing the mixing in the cavity shear layer and thus modifying the feedback loop associated with the cavity resonance. The nonlinear interactions in the cavity flow are no longer driven by the resonant cavity modes but by the forcing associated with the oscillatory blowing. The oscillatory blowing does not suppress the mode switching behavior of the cavity flow, but the amplitude modulation is reduced.

  20. Distinctive Signature of Indium Gallium Nitride Quantum Dot Lasing in Microdisks Cavities

    E-print Network

    Woolf, Alexander; Aharanovich, Igor; Zhu, Tongtong; Niu, Nan; Wang, Danqing; Oliver, Rachel A; Hu, Evelyn L

    2014-01-01

    Low threshold lasers realized within compact, high quality optical cavities enable a variety of nanophotonics applications. Gallium nitride (GaN) materials containing indium gallium nitride (InGaN) quantum dots and quantum wells offer an outstanding platform to study light matter interactions and realize practical devices such as efficient light emitting diodes and nanolasers. Despite progress in the growth and characterization of InGaN quantum dots, their advantages as the gain medium in low threshold lasers have not been clearly demonstrated. This work seeks to better understand the reasons for these limitations by focusing on the simpler, limited-mode microdisk cavities, and by carrying out comparisons of lasing dynamics in those cavities using varying gain media including InGaN quantum wells, fragmented quantum wells, and a combination of fragmented quantum wells with quantum dots. For each gain medium, we utilize the distinctive, high quality (Q~5500) modes of the cavities, and the change in the highest ...

  1. Coupled Resonator Vertical Cavity Laser Diode

    SciTech Connect

    CHOQUETTE, KENT D.; CHOW, WENG W.; FISCHER, ARTHUR J.; GEIB, KENT M.; HOU, HONG Q.

    1999-09-16

    We report the operation of an electrically injected monolithic coupled resonator vertical cavity laser which consists of an active cavity containing In{sub x}Ga{sub 1{minus}x}As quantum wells optically coupled to a passive GaAs cavity. This device demonstrates novel modulation characteristics arising from dynamic changes in the coupling between the active and passive cavities. A composite mode theory is used to model the output modulation of the coupled resonator vertical cavity laser. It is shown that the laser intensity can be modulated by either forward or reverse biasing the passive cavity. Under forward biasing, the modulation is due to carrier induced changes in the refractive index, while for reverse bias operation the modulation is caused by field dependent cavity enhanced absorption.

  2. Knowledge diffusion in the collaboration hypernetwork

    NASA Astrophysics Data System (ADS)

    Yang, Guang-Yong; Hu, Zhao-Long; Liu, Jian-Guo

    2015-02-01

    As knowledge constitutes a primary productive force, it is important to understand the performance of knowledge diffusion. In this paper, we present a knowledge diffusion model based on the local-world non-uniform hypernetwork, which introduces the preferential diffusion mechanism and the knowledge absorptive capability ?j, where ?j is correlated with the hyperdegree dH(j) of node j. At each time step, we randomly select a node i as the sender; a receiver node is selected from the set of nodes that the sender i has published with previously, with probability proportional to the number of papers they have published together. Applying the average knowledge stock V bar(t) , the variance ?2(t) and the variance coefficient c(t) of knowledge stock to measure the growth and diffusion of knowledge and the adequacy of knowledge diffusion, we have made 3 groups of comparative experiments to investigate how different network structures, hypernetwork sizes and knowledge evolution mechanisms affect the knowledge diffusion, respectively. As the diffusion mechanisms based on the hypernetwork combine with the hyperdegree of node, the hypernetwork is more suitable for investigating the performance of knowledge diffusion. Therefore, the proposed model could be helpful for deeply understanding the process of the knowledge diffusion in the collaboration hypernetwork.

  3. Magnetic spheres in microwave cavities

    NASA Astrophysics Data System (ADS)

    Zare Rameshti, Babak; Cao, Yunshan; Bauer, Gerrit E. W.

    2015-06-01

    We apply Mie scattering theory to study the interaction of magnetic spheres with microwaves in cavities beyond the magnetostatic and rotating wave approximations. We demonstrate that both strong and ultrastrong coupling can be realized for stand alone magnetic spheres made from yttrium iron garnet (YIG), acting as an efficient microwave antenna. The eigenmodes of YIG spheres with radii of the order mm display distinct higher angular momentum character that has been observed in experiments.

  4. Diffusing Diffusivity: A Model for Anomalous, yet Brownian, Diffusion

    NASA Astrophysics Data System (ADS)

    Chubynsky, Mykyta V.; Slater, Gary W.

    2014-08-01

    Wang et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 15160 (2009)] have found that in several systems the linear time dependence of the mean-square displacement (MSD) of diffusing colloidal particles, typical of normal diffusion, is accompanied by a non-Gaussian displacement distribution G(x ,t), with roughly exponential tails at short times, a situation they termed "anomalous yet Brownian" diffusion. The diversity of systems in which this is observed calls for a generic model. We present such a model where there is diffusivity memory but no direction memory in the particle trajectory, and we show that it leads to both a linear MSD and a non-Gaussian G(x ,t) at short times. In our model, the diffusivity is undergoing a (perhaps biased) random walk, hence the expression "diffusing diffusivity". G(x ,t) is predicted to be exactly exponential at short times if the distribution of diffusivities is itself exponential, but an exponential remains a good fit for a variety of diffusivity distributions. Moreover, our generic model can be modified to produce subdiffusion.

  5. Temperature Structure of a Coronal Cavity

    NASA Technical Reports Server (NTRS)

    Kucera, T. A.; Gibson, S. E.; Schmit, D. J.

    2011-01-01

    we analyze the temperature structure of a coronal cavity observed in Aug. 2007. coronal cavities are long, low-density structures located over filament neutral lines and are often seen as dark elliptical features at the solar limb in white light, EUV and x-rays. when these structures erupt they form the cavity portions of CMEs. It is important to establish the temperature structure of cavities in order to understand the thermodynamics of cavities in relation to their three-dimensional magnetic structure. To analyze the temperature we compare temperature ratios of a series of iron lines observed by the Hinode/EUv Imaging spectrometer (EIS). We also use those lines to constrain a forward model of the emission from the cavity and streamer. The model assumes a coronal streamer with a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel lenth. Temperature and density can be varied as a function of altitude both in the cavity and streamer. The general cavity morphology and the cavity and streamer density have already been modeled using data from STEREO's SECCHI/EUVI and Hinode/EIS (Gibson et al 2010 and Schmit & Gibson 2011).

  6. Intrauterine device for laser light diffusion and method of using the same

    DOEpatents

    Tadir, Yona (Irvine, CA); Berns, Michael W. (Trabuco Canyon, CA); Svaasand, Lars O. (Trondheim, NO); Tromberg, Bruce J. (Irvine, CA)

    1995-01-01

    An improved device for delivery of photoenergy from a light source, such as a laser, into a uterine cavity for photodynamic therapy is comprised of a plurality of optic fibers, which are bundled together and inserted into the uterine cavity by means of a uterine cannula. The cannula is positioned within the uterine cavity at a preferred location and then withdrawn thereby allowing the plurality of optic fibers to splay or diverge one from the other within the cavity. Different portions of the distal tip of the optic fiber is provided with a light diffusing tip, the remainder being provided with a nondiffusing tip portion. The fiber optic shape, as well as the segment which is permitted to actively diffuse light through the tip, is selected in order to provide a more uniform exposure intensity of the photo energy or at least sufficient radiation directed to each segment of the uterine walls.

  7. Cavity Optomechanics at Millikelvin Temperatures

    NASA Astrophysics Data System (ADS)

    Meenehan, Sean Michael

    The field of cavity optomechanics, which concerns the coupling of a mechanical object's motion to the electromagnetic field of a high finesse cavity, allows for exquisitely sensitive measurements of mechanical motion, from large-scale gravitational wave detection to microscale accelerometers. Moreover, it provides a potential means to control and engineer the state of a macroscopic mechanical object at the quantum level, provided one can realize sufficiently strong interaction strengths relative to the ambient thermal noise. Recent experiments utilizing the optomechanical interaction to cool mechanical resonators to their motional quantum ground state allow for a variety of quantum engineering applications, including preparation of non-classical mechanical states and coherent optical to microwave conversion. Optomechanical crystals (OMCs), in which bandgaps for both optical and mechanical waves can be introduced through patterning of a material, provide one particularly attractive means for realizing strong interactions between high-frequency mechanical resonators and near-infrared light. Beyond the usual paradigm of cavity optomechanics involving isolated single mechanical elements, OMCs can also be fashioned into planar circuits for photons and phonons, and arrays of optomechanical elements can be interconnected via optical and acoustic waveguides. Such coupled OMC arrays have been proposed as a way to realize quantum optomechanical memories, nanomechanical circuits for continuous variable quantum information processing and phononic quantum networks, and as a platform for engineering and studying quantum many-body physics of optomechanical meta-materials. However, while ground state occupancies (that is, average phonon occupancies less than one) have been achieved in OMC cavities utilizing laser cooling techniques, parasitic absorption and the concomitant degradation of the mechanical quality factor fundamentally limit this approach. On the other hand, the high mechanical frequency of these systems allows for the possibility of using a dilution refrigerator to simultaneously achieve low thermal occupancy and long mechanical coherence time by passively cooling the device to the millikelvin regime. This thesis describes efforts to realize the measurement of OMC cavities inside a dilution refrigerator, including the development of fridge-compatible optical coupling schemes and the characterization of the heating dynamics of the mechanical resonator at sub-kelvin temperatures. We will begin by summarizing the theoretical framework used to describe cavity optomechanical systems, as well as a handful of the quantum applications envisioned for such devices. Then, we will present background on the design of the nanobeam OMC cavities used for this work, along with details of the design and characterization of tapered fiber couplers for optical coupling inside the fridge. Finally, we will present measurements of the devices at fridge base temperatures of Tf = 10 mK, using both heterodyne spectroscopy and time-resolved sideband photon counting, as well as detailed analysis of the prospects for future quantum applications based on the observed optically-induced heating.

  8. Whispering gallery modes in hexagonal microcavities fabricated by crystal growth

    E-print Network

    Kudo, Hiroshi; Tanabe, Takasumi

    2013-01-01

    We investigated the whispering gallery modes of cavities with a hexagonal cross-section. We found two different modes, namely perturbed and quasi-WGMs, of which the former exhibits the higher Q when the corner radius is large. We studied the dependence of Q on the curvature radius of the polygonal cavities and found that the coupling between the two modes determines the Q of the cavity. In addition we fabricated a cavity by employing laser heated pedestal growth and demonstrated a high Q.

  9. The Effect of Artificial Diffusivity on the Flute Instability

    SciTech Connect

    Ryutov, D D; Cohen, B I; Cohen, R H; Hooper, E B; Sovinec, C R

    2005-05-03

    Sometimes, in order to improve the performance of magneto-hydrodynamical codes, artificial diffusivity (D) is introduced in the mass continuity equation. In this communication, an analysis of the effect of the artificial diffusivity on the low-beta plasma stability in a simple geometry is presented. It is shown that, at low diffusivity, one recovers classical results, whereas at high diffusivity the plasma becomes more unstable. Dependence of the stability on D is suppressed if the volume of flux-tube varies insignificantly in the course of the perturbation growth. These observations may help the code runners to identify regimes where the artificial diffusivity is not affecting the results (or vise versa).

  10. Molecular diffusion into horse spleen ferritin: a nitroxide radical spin probe study.

    PubMed Central

    Yang, X; Chasteen, N D

    1996-01-01

    Electron paramagnetic resonance spectroscopy and gel permeation chromatography were employed to study the molecular diffusion of a number of small nitroxide spin probes (approximately 7-9 A diameter) into the central cavity of the iron-storage protein ferritin. Charge and polarity of these radicals play a critical role in the diffusion process. The negatively charged radical 4-carboxy-2,2,6,6-tetramethylpiperidine-N-oxyl (4-carboxy-TEMPO) does not penetrate the cavity whereas the positively charged 4-amino-TEMPO and 3-(aminomethyl)-proxyl radical and polar 4-hydroxy-TEMPO radical do. Unlike the others, the apolar TEMPO radical does not enter the cavity but instead binds to ferritin, presumably at a hydrophobic region of the protein. The kinetic data indicate that diffusion is not purely passive, the driving force coming not only from the concentration gradient between the inside and outside of the protein but also from charge interactions between the diffusant and the protein. A model for diffusion is derived that describes the observed kinetics. First-order half-lives for diffusion into the protein of 21-26 min are observed, suggesting that reductant molecules with diameters considerably larger than approximately 9 A would probably enter the protein cavity too slowly to mobilize iron efficiently by direct interaction with the mineral core. PMID:8874032

  11. Effective emissivity of a blackbody cavity formed by two coaxial tubes.

    PubMed

    Mei, Guohui; Zhang, Jiu; Zhao, Shumao; Xie, Zhi

    2014-04-10

    A blackbody cavity is developed for continuously measuring the temperature of molten steel, which consists of a cylindrical outer tube with a flat bottom, a coaxial inner tube, and an aperture diaphragm. The ray-tracing approach based on the Monte Carlo method was applied to calculate the effective emissivity for the isothermal cavity with the diffuse walls. And the dependences of the effective emissivity on the inner tube relative length were calculated for various inner tube radii, outer tube lengths, and wall emissivities. Results indicate that the effective emissivity usually has a maximum corresponding to the inner tube relative length, which can be explained by the impact of the inner tube relative length on the probability of the rays absorbed after two reflections. Thus, these results are helpful to the optimal design of the blackbody cavity. PMID:24787424

  12. Communication: Escape kinetics of self-propelled Janus particles from a cavity: numerical simulations.

    PubMed

    Ghosh, Pulak Kumar

    2014-08-14

    We numerically investigate the escape kinetics of elliptic Janus particles from narrow two-dimensional cavities with reflecting walls. The self-propulsion velocity of the Janus particle is directed along either their major (prolate) or minor (oblate) axis. We show that the mean exit time is very sensitive to the cavity geometry, particle shape, and self-propulsion strength. The mean exit time is found to be a minimum when the self-propulsion length is equal to the cavity size. We also find the optimum mean escape time as a function of the self-propulsion velocity, translational diffusion, and particle shape. Thus, effective transport control mechanisms for Janus particles in a channel can be implemented. PMID:25134544

  13. [A case of pulmonary aspergillosis subacutely forming a cavity during the course of microscopic polyangiitis].

    PubMed

    Kazuyori, Taisuke; Maeshima, Arafumi; Sakai, Masako; Shimizu, Kumi; Kurata, Kiyoko; Seki, Hiromi; Wakaki, Misa; Goto, Taichiro; Saitou, Yasuhiro; Onaka, Akio; Kato, Ryouichi; Oyamada, Yoshitaka

    2009-04-01

    A 77-year-old woman was referred to our department with hemoptysis. Microscopic polyangiitis (MPA) with resultant alveolar hemorrhage was diagnosed because of diffuse infiltrate of the right lung, proteinurea, renal dysfunction and the presence of MPO-ANCA. The disease responded well to corticosteroid therapy. She was discharged, but as corticosteroid was gradually tapered, an irregularly-shaped nodule appeared in the right upper lung field within 2 weeks. She was re-admitted because the nodule increased in size with cavity formation in spite of the administration of antibacterial agent. Pulmonary aspergillosis was diagnosed, since bronchial washing and transbronchial lung biopsy revealed the presence of Aspergillus fumigatus. Serum beta-D-glucan was decreased and the cavity was reduced in size, responding to the treatment with micafungin. However, she died later of systemic infection by a herpesvirus. We report this case because of the interesting course of pulmonary aspergillosis that subacutely formed a cavity. PMID:19455964

  14. Pulsed discharge nozzle optimization and its application to the cavity ring-down spectroscopy of cold PAH ions

    Microsoft Academic Search

    Jerome Remy; Ludovic Biennier; Farid Salama; Louis J. Allamandola; James J. Scherer; Anthony O'Keefe

    2002-01-01

    In an effort to address the problem of the identification of the diffuse interstellar bands, the Astrochemistry Laboratory at NASA Ames has developed a new instrument to measure the visible absorption spectra of selected free cold polycylic aromatic hydrocarbon (PAH) ions in astrophysically relevant conditions [1]. The experimental set-up is based on a cavity ring-down (CRD) spectrometer - relying on

  15. Joint nucleation in layered rocks with non-uniform distribution of cavities

    Microsoft Academic Search

    Ram Weinberger

    2001-01-01

    Characterization of ‘critical flaws’ that initiate into systematic joints is essential for understanding the process of fracturing in sedimentary rocks. In this study, advantage is taken of the well-developed surface morphology of joints in the dolomite layers of the Judea Group, central Israel, and the role played by spherical cavity-shaped flaws during nucleation and growth of joints is analyzed. An

  16. Modeling and Feedback Control for Subsonic Cavity Flows: A Collaborative Approach

    E-print Network

    Debiasi, Marco

    a discontinuity or obstacle in the flow (e.g. the cavity trailing edge) scatter acoustic waves that propagate upstream and reach the shear layer receptivity region where they tune and enhance the development and growth of shear layer structures. The resulting acoustic fluctuations can be very intense and can lead

  17. In situ measurement of gas diffusion properties of sealing polymers for MEMS packages by an optical gas leak test

    Microsoft Academic Search

    Changsoo Jang; Arindam Goswami; Bongtae Han

    2009-01-01

    A novel inverse approach based on an optical leak test is developed and implemented for in-situ measurement of gas diffusion properties of polymeric seals used in MEMS packages. Cavity pressure evolution during a leak test is documented as a function of time using laser-based interferometry, and the diffusion properties of a polymeric seal are subsequently determined from the measured pressure

  18. Nd3+ ion diffusion during sintering of Nd:YAG transparent ceramics

    SciTech Connect

    Hollingsworth, J P; Kuntz, J D; Soules, T F

    2008-10-24

    Using an electron microprobe, we measured and characterized the Nd{sup 3+} ion diffusion across a boundary between Nd doped and undoped ceramic yttrium aluminum garnet (YAG) for different temperature ramps and hold times and temperatures. The results show significant Nd ion diffusion on the order of micrometers to tens of micrometers depending on the time and temperature of sintering. The data fit well a model including bulk diffusion, grain boundary diffusion and grain growth. Grain boundary diffusion dominates and grain growth limits grain boundary diffusion by reducing the total cross sectional area of grain boundaries.

  19. Emerging applications for vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Harris, J. S.; O'sullivan, T.; Sarmiento, T.; Lee, M. M.; Vo, S.

    2011-01-01

    Vertical cavity surface emitting lasers (VCSELs) emitting at 850 nm have experienced explosive growth in the past decade because of their many attractive optical features and incredibly low-cost manufacturability. This review reviews the foundations for GaAs-based VCSEL technology as well as the materials and device challenges to extend the operating wavelength to both shorter and longer wavelengths. We discuss some of the applications that are enabled by the integration of VCSELs with both active and passive semiconductor elements for telecommunications, both in vivo and in vitro biosensing, high-density optical storage and imaging at wavelengths much less than the diffraction limit of light.

  20. Photon trapping in cavity quantum electrodynamics

    E-print Network

    Agarwal, G S

    2015-01-01

    We propose and analyze a scheme for photon trapping in an optical resonator coupled with two-level atoms. We show that when the cavity is excited by two identical light fields from two ends of the cavity respectively, the output light from the cavity is suppressed while the intra-cavity light field is near the maximum due to the excitation of the polariton state of the coupled cavity and atom system. We also present methods for the direct probing of the trapped polariton state. The photon trapping is manifested by the destructive interference of the transmitted light and the incident light. Such photon trapping is quite generic and should be observable experimentally in a variety of cavity quantum electrodynamics systems.

  1. Cavity-Dumped Communication Laser Design

    NASA Technical Reports Server (NTRS)

    Roberts, W. T.

    2003-01-01

    Cavity-dumped lasers have significant advantages over more conventional Q-switched lasers for high-rate operation with pulse position modulation communications, including the ability to emit laser pulses at 1- to 10-megahertz rates, with pulse widths of 0.5 to 5 nanoseconds. A major advantage of cavity dumping is the potential to vary the cavity output percentage from pulse to pulse, maintaining the remainder of the energy in reserve for the next pulse. This article presents the results of a simplified cavity-dumped laser model, establishing the requirements for cavity efficiency and projecting the ultimate laser efficiency attainable in normal operation. In addition, a method of reducing or eliminating laser dead time is suggested that could significantly enhance communication capacity. The design of a laboratory demonstration laser is presented with estimates of required cavity efficiency and demonstration potential.

  2. Eigenmode in a misaligned triangular optical cavity

    E-print Network

    Kawazoe, Fumiko; Lueck, Harald

    2010-01-01

    We derive relationships between various types of small misalignments on a triangular Fabry-Perot cavity and associated geometrical eigenmode changes. We focus on the changes of beam spot positions on cavity mirrors, the beam waist position, and its angle. A comparison of analytical and numerical results shows excellent agreement. The results are applicable to any triangular cavity close to an isosceles triangle, with the lengths of two sides much bigger than the other, consisting of a curved mirror and two flat mirrors yielding a waist equally separated from the two flat mirrors. This cavity shape is most commonly used in laser interferometry. The analysis presented here can easily be extended to more generic cavity shapes. The geometrical analysis not only serves as a method of checking a simulation result, but also gives an intuitive and handy tool to visualize the eigenmode of a misaligned triangular cavity.

  3. Tunable-cavity QED with phase qubits

    NASA Astrophysics Data System (ADS)

    Whittaker, Jed D.; da Silva, Fabio; Allman, Michael Shane; Lecocq, Florent; Cicak, Katarina; Sirois, Adam; Teufel, John; Aumentado, Jose; Simmonds, Raymond W.

    2014-03-01

    We describe a tunable-cavity QED architecture with an rf SQUID phase qubit inductively coupled to a single-mode, resonant cavity with a tunable frequency that allows for both tunneling and dispersive measurements. Dispersive measurement is well characterized by a three-level model, strongly dependent on qubit anharmonicity, qubit-cavity coupling and detuning. The tunable cavity frequency provides dynamic control over the coupling strength and qubit-cavity detuning helping to minimize Purcell losses and cavity-induced dephasing during qubit operation. The maximum decay time T1 = 1 . 5 ?s is limited by dielectric losses from a design geometry similar to planar transmon qubits. This work supported by NIST and NSA grant EAO140639.

  4. Coupled-cavity drift-tube linac

    DOEpatents

    Billen, James H. (Los Alamos, NM)

    1996-01-01

    A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the .pi.-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is .beta..lambda., where .lambda. is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a .pi./2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range.

  5. Coupled-cavity drift-tube linac

    DOEpatents

    Billen, J.H.

    1996-11-26

    A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the {pi}-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is {beta}{lambda}, where {lambda} is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a {pi}/2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range. 5 figs.

  6. Mounting system for optical frequency reference cavities

    NASA Technical Reports Server (NTRS)

    Notcutt, Mark (Inventor); Hall, John L. (Inventor); Ma, Long-Sheng (Inventor)

    2008-01-01

    A technique for reducing the vibration sensitivity of laser-stabilizing optical reference cavities is based upon an improved design and mounting method for the cavity, wherein the cavity is mounted vertically. It is suspended at one plane, around the spacer cylinder, equidistant from the mirror ends of the cavity. The suspension element is a collar of an extremely low thermal expansion coefficient material, which surrounds the spacer cylinder and contacts it uniformly. Once the collar has been properly located, it is cemented in place so that the spacer cylinder is uniformly supported and does not have to be squeezed at all. The collar also includes a number of cavities partially bored into its lower flat surface, around the axial bore. These cavities are support points, into which mounting base pins will be inserted. Hence the collar is supported at a minimum of three points.

  7. Nanobeam photonic crystal cavity quantum dot laser

    E-print Network

    Gong, Yiyang; Shambat, Gary; Sarmiento, Tomas; Harris, James S; Vuckovic, Jelena

    2010-01-01

    The lasing behavior of one dimensional GaAs nanobeam cavities with embedded InAs quantum dots is studied at room temperature. Lasing is observed throughout the quantum dot PL spectrum, and the wavelength dependence of the threshold is calculated. We study the cavity lasers under both 780 nm and 980 nm pump, finding thresholds as low as 0.3 uW and 19 uW for the two pump wavelengths, respectively. Finally, the nanobeam cavity laser wavelengths are tuned by up to 7 nm by employing a fiber taper in near proximity to the cavities. The fiber taper is used both to efficiently pump the cavity and collect the cavity emission.

  8. Nanobeam photonic crystal cavity quantum dot laser.

    PubMed

    Gong, Yiyang; Ellis, Bryan; Shambat, Gary; Sarmiento, Tomas; Harris, James S; Vuckovic, Jelena

    2010-04-26

    The lasing behavior of one dimensional GaAs nanobeam cavities with embedded InAs quantum dots is studied at room temperature. Lasing is observed throughout the quantum dot PL spectrum, and the wavelength dependence of the threshold is calculated. We study the cavity lasers under both 780 nm and 980 nm pump, finding thresholds as low as 0.3 microW and 19 microW for the two pump wavelengths, respectively. Finally, the nanobeam cavity laser wavelengths are tuned by up to 7 nm by employing a fiber taper in near proximity to the cavities. The fiber taper is used both to efficiently pump the cavity and collect the cavity emission. PMID:20588722

  9. Grain Growth in Niobium for Superconducting Radio Frequency Cavities 

    E-print Network

    Vernon, Joshua A.

    2009-06-09

    were changed to reflect this offset. 11 Mounting Samples were mounted according to ASTM E3-01 [8]. Here, four samples went into a pressurized cylinder with bakelite powder and placed under 4 kpsi pressure and heated up to about 135 degrees... followed ASTM E3-01 [8]. Once the samples were mounted, they were taken to a polishing wheel that resembles a pottery wheel. Each sample went through several polishing steps to achieve a surface containing scratches smaller than 0.05 microns...

  10. Grain Growth in Niobium for Superconducting Radio Frequency Cavities

    E-print Network

    Vernon, Joshua A.

    2009-06-09

    Associate Dean for Undergraduate Research: Robert C. Webb Major: Mechanical Engineering April 2009 Submitted to the Office of Undergraduate Research Texas A&M University in partial fulfillment of the requirements for the designation... when I was not in the lab. When I came home frustrated and confused, she would listen intently, whether she understood or not. vii NOMENCLATURE ECAE Equal Channel Angular Extrusion ASTM American Society for Testing and Materials viii...

  11. Amplitude Noise Squeezing in Cavity-Driven Oscillations of a Mechanical Resonator

    E-print Network

    D. A. Rodrigues; A. D. Armour

    2010-02-02

    We analyze the amplitude and phase noise of limit-cycle oscillations in a mechanical resonator coupled parametrically to an optical cavity driven above its resonant frequency. At a given temperature the limit-cycle oscillations have lower amplitude noise than states of the same average amplitude excited by a pure harmonic drive; for sufficiently low thermal noise a sub-Poissonian resonator state can be produced. We also calculate the linewidth narrowing that occurs in the limit-cycle states, and show that while the minimum is set by direct phase diffusion, diffusion due to the optical spring effect can dominate if the cavity is not driven exactly at a side-band resonance.

  12. Reaction-diffusion textures

    Microsoft Academic Search

    Andrew P. Witkin; Michael Kass

    1991-01-01

    We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

  13. Simulating Growth Dynamics of Neurons on Substrates

    NASA Astrophysics Data System (ADS)

    Bernath, Sawyer; Staii, Cristian; Atherton, Timothy

    2012-02-01

    We present computer simulations of neuron growth in which growth cones both create and are guided by growth promoter molecules which move diffusively. Our model predicts several features of the trajectories that are experimentally measurable, including arclength and curvature as functions of time. By comparing these predictions to time-lapse microscopy experiments of axon growth in a controlled environment, we gain new insights into neuronal growth and connectivity.

  14. Method of varying a characteristic of an optical vertical cavity structure formed by metalorganic vapor phase epitaxy

    DOEpatents

    Hou, Hong Q. (Albuquerque, NM); Coltrin, Michael E. (Albuquerque, NM); Choquette, Kent D. (Albuquerque, NM)

    2001-01-01

    A process for forming an array of vertical cavity optical resonant structures wherein the structures in the array have different detection or emission wavelengths. The process uses selective area growth (SAG) in conjunction with annular masks of differing dimensions to control the thickness and chemical composition of the materials in the optical cavities in conjunction with a metalorganic vapor phase epitaxy (MOVPE) process to build these arrays.

  15. Status of the SSC LEB rf cavity

    SciTech Connect

    Coleman, P.C.; Brandeberry, F.; Friedrichs, C.; Goren, Y.; Grimm, T.; Hulsey, G.; Kwiatkowski, S.; Propp, A.; Taylor, L.; Walling, L. (Superconducting Super Collider Lab., Dallas, TX (United States)); Averbukh, J.; Karliner, M.; Petrov, V.; Yakovlev, S. (Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation))

    1993-05-01

    A tunable, high-accelerating-gradient cavity prototype has been designed and built for use in the rf system for the Low Energy Booster (LEB) at the Superconducting Super Collider (SSC). Testing of the cavity using one tuner cooling variant has been completed. This paper reports on results of low level, high level and tuning tests performed on the cavity. The tuner damaged during high power testing. Discussion of the is included.

  16. Non linear effects in ferrite tuned cavities

    SciTech Connect

    Goren, Y.; Mahale, N.; Walling, L.; Enegren, T.; Hulsey, G. [Superconducting Super Collider Lab., Dallas, TX (United States); Yakoviev, V.; Petrov, V. [Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation)

    1993-05-01

    The phenomenon of dependence of the resonance shape and frequency on the RF power level in perpendicular biased ferrite-tuned cavities has been observed by G. Hulsey and C. Friedrichs in the SSC test cavity experiment. This paper presents a theoretical as well as numerical analysis of this phenomenon and compares the results with experimental data. The effect of this nonlinearity on the SSC low energy booster prototype cavity is discussed.

  17. Single Atom Detection With Optical Cavities

    E-print Network

    R. Poldy; B. C. Buchler; J. C. Close

    2008-07-08

    We present a thorough analysis of single atom detection using optical cavities. The large set of parameters that influence the signal-to-noise ratio for cavity detection is considered, with an emphasis on detunings, probe power, cavity finesse and photon detection schemes. Real device operating restrictions for single photon counting modules and standard photodiodes are included in our discussion, with heterodyne detection emerging as the clearly favourable technique, particularly for detuned detection at high power.

  18. FABRICATION OF SUPERCONDUCTING CAVITIES FOR SNS

    Microsoft Academic Search

    M. Pekeler; S. Bauer; J. Schwellenbach; M. Tradt; H. Vogel

    2004-01-01

    During the last three years ACCEL fabricated almost all 109 superconducting cavities for the Spallation Neutron Source (SNS) in Oak Ridge, Tennessee. Two series of 35 medium beta (beta=0.61) and 74 high beta (beta=0.81) cavities will be delivered until October 2004. Besides cavity manufacturing ACCEL also performed RF tuning and chemical surface preparation. We give an outline on the current

  19. Resonant-cavity antenna for plasma heating

    DOEpatents

    Perkins, Jr., Francis W. (Princeton, NJ); Chiu, Shiu-Chu (San Diego, CA); Parks, Paul (San Diego, CA); Rawls, John M. (Del Mar, CA)

    1987-01-01

    Disclosed is a resonant coil cavity wave launcher for energizing a plasma immersed in a magnetic field. Energization includes launching fast Alfven waves to excite ion cyclotron frequency resonances in the plasma. The cavity includes inductive and capacitive reactive members spaced no further than one-quarter wavelength from a first wall confinement chamber of the plasma. The cavity wave launcher is energized by connection to a waveguide or transmission line carrying forward power from a remote radio frequency energy source.

  20. Soft x-ray laser cavities

    SciTech Connect

    Ceglio, N.M.; Stearns, D.G.; Hawryluk, A.M.; Barbee, T.M.; Danzmann, K.; Kuehne, M.; Mueller, P.; Wende, B.; Stearns, M.B.; Petford-Long, A.K.

    1986-07-08

    We report progress in the development of multilayer components for use in multiple pass soft x-ray laser cavities operating in the 100A to 300A spectral range. Our work includes fabrication and characterization of multilayer components; simple resonant cavity design; damage threshold assessment for multilayers in the x-ray laser environment; and multipass cavity experiments for efficiency enhancement and transverse mode selection. 14 refs., 9 figs.

  1. Scattering model description of cascaded cavity configurations

    E-print Network

    András Dombi; Peter Domokos

    2014-04-30

    Cascaded optical cavities appear in various quantum information processing schemes in which atomic qubits are sitting in separate cavities interconnected by photons as flying qubits. The usual theoretical description relies on a coupled-mode Hamiltonian approach. Here we investigate the system of cascaded cavities without modal decomposition by using a scattering model approach and determine the validity regime of the coupled-mode models.

  2. Surveying Diffusion in Complex Geometries. An Essay

    E-print Network

    Denis Grebenkov

    2009-09-08

    The surrounding world surprises us by the beauty and variety of complex shapes that emerge from nanometric to macroscopic scales. Natural or manufactured materials (sandstones, sedimentary rocks and cement), colloidal solutions (proteins and DNA), biological cells, tissues and organs (lungs, kidneys and placenta), they all present irregularly shaped "scenes" for a fundamental transport "performance", that is, diffusion. Here, the geometrical complexity, entangled with the stochastic character of diffusive motion, results in numerous fascinating and sometimes unexpected effects like diffusion screening or localization. These effects control many diffusion-mediated processes that play an important role in heterogeneous catalysis, biochemical mechanisms, electrochemistry, growth phenomena, oil recovery, or building industry. In spite of a long and rich history of academic and industrial research in this field, it is striking to see how little we know about diffusion in complex geometries, especially the one which occurs in three dimensions. We present our recent results on restricted diffusion. We look into the role of geometrical complexity at different levels, from boundary microroughness to hierarchical structure and connectivity of the whole diffusion-confining domain. We develop a new approach which consists in combining fast random walk algorithms with spectral tools. The main focus is on studying diffusion in model complex geometries (von Koch boundaries, Kitaoka acinus, etc.), as well as on developing and testing spectral methods. We aim at extending this knowledge and at applying the accomplished arsenal of theoretical and numerical tools to structures found in nature and industry.

  3. Dynamic relaxation of a liquid cavity under amorphous boundary conditions

    NASA Astrophysics Data System (ADS)

    Cavagna, Andrea; Grigera, Tomás S.; Verrocchio, Paolo

    2012-05-01

    The growth of cooperatively rearranging regions was invoked long ago by Adam and Gibbs to explain the slowing down of glass-forming liquids. The lack of knowledge about the nature of the growing order, though, complicates the definition of an appropriate correlation function. One option is the point-to-set (PTS) correlation function, which measures the spatial span of the influence of amorphous boundary conditions on a confined system. By using a swap Monte Carlo algorithm we measure the equilibration time of a liquid droplet bounded by amorphous boundary conditions in a model glass-former at low temperature, and we show that the cavity relaxation time increases with the size of the droplet, saturating to the bulk value when the droplet outgrows the point-to-set correlation length. This fact supports the idea that the point-to-set correlation length is the natural size of the cooperatively rearranging regions. On the other hand, the cavity relaxation time computed by a standard, nonswap dynamics, has the opposite behavior, showing a very steep increase when the cavity size is decreased. We try to reconcile this difference by discussing the possible hybridization between mode-coupling theory and activated processes, and by introducing a new kind of amorphous boundary conditions, inspired by the concept of frozen external state as an alternative to the commonly used frozen external configuration.

  4. Dynamic relaxation of a liquid cavity under amorphous boundary conditions.

    PubMed

    Cavagna, Andrea; Grigera, Tomás S; Verrocchio, Paolo

    2012-05-28

    The growth of cooperatively rearranging regions was invoked long ago by Adam and Gibbs to explain the slowing down of glass-forming liquids. The lack of knowledge about the nature of the growing order, though, complicates the definition of an appropriate correlation function. One option is the point-to-set (PTS) correlation function, which measures the spatial span of the influence of amorphous boundary conditions on a confined system. By using a swap Monte Carlo algorithm we measure the equilibration time of a liquid droplet bounded by amorphous boundary conditions in a model glass-former at low temperature, and we show that the cavity relaxation time increases with the size of the droplet, saturating to the bulk value when the droplet outgrows the point-to-set correlation length. This fact supports the idea that the point-to-set correlation length is the natural size of the cooperatively rearranging regions. On the other hand, the cavity relaxation time computed by a standard, nonswap dynamics, has the opposite behavior, showing a very steep increase when the cavity size is decreased. We try to reconcile this difference by discussing the possible hybridization between mode-coupling theory and activated processes, and by introducing a new kind of amorphous boundary conditions, inspired by the concept of frozen external state as an alternative to the commonly used frozen external configuration. PMID:22667566

  5. Unpacking of a Crumpled Wire from Two-Dimensional Cavities

    PubMed Central

    Sobral, Thiago A.; Gomes, Marcelo A. F.; Machado, Núbia R.; Brito, Valdemiro P.

    2015-01-01

    The physics of tightly packed structures of a wire and other threadlike materials confined in cavities has been explored in recent years in connection with crumpled systems and a number of topics ranging from applications to DNA packing in viral capsids and surgical interventions with catheter to analogies with the electron gas at finite temperature and with theories of two-dimensional quantum gravity. When a long piece of wire is injected into two-dimensional cavities, it bends and originates in the jammed limit a series of closed structures that we call loops. In this work we study the extraction of a crumpled tightly packed wire from a circular cavity aiming to remove loops individually. The size of each removed loop, the maximum value of the force needed to unpack each loop, and the total length of the extracted wire were measured and related to an exponential growth and a mean field model consistent with the literature of crumpled wires. Scaling laws for this process are reported and the relationship between the processes of packing and unpacking of wire is commented upon. PMID:26047315

  6. Low beta spoke cavity multipacting analysis

    NASA Astrophysics Data System (ADS)

    Xu, Bo; Li, Han; Zhang, Juan; Sha, Peng; Wang, Qun-Yao; Lin, Hai-Ying; Huang, Hong; Dai, Jian-Ping; Sun, Yi; Wang, Guang-Wei; Pan, Wei-Min

    2013-12-01

    The simulation and analysis for electron multipacting phenomenon in a low ? spoke superconducting cavity in ADS proton accelerator are proposed. Using both CST and Track3P codes, the electron multipacting calculation for ?=0.12 spoke superconducting cavity is implemented. The methods of multipacting calculation on both codes are studied and described. With the comparison between the calculation results and the cavity vertical test result, the accuracy and reliability of different codes on calculating multipacting are analyzed. Multipacting calculation can help to understand the results of vertical test and also can help to do the optimization in cavity design.

  7. Mechanical Properties of Ingot Nb Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

    2014-07-01

    This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

  8. Design of the ILC Crab Cavity System

    SciTech Connect

    Adolphsen, C.; Beard, C.; Bellantoni, L.; Burt, G.; Carter, R.; Chase, B.; Church, M.; Dexter, A.; Dykes, M.; Edwards, H.; Goudket, P; Jenkins, R.; Jones, R.M.; Kalinin,; Khabiboulline, T.; Ko, K.; Latina, A.; Li, Z.; Ma, L.; McIntosh, P.; Ng, C.; /SLAC /Daresbury /Fermilab /Cockcroft Inst. Accel. Sci. Tech. /CERN

    2007-08-15

    The International Linear Collider (ILC) has a 14 mrad crossing angle in order to aid extraction of spent bunches. As a result of the bunch shape at the interaction point, this crossing angle at the collision causes a large luminosity loss which can be recovered by rotating the bunches prior to collision using a crab cavity. The ILC baseline crab cavity is a 9-cell superconducting dipole cavity operating at a frequency of 3.9 GHz. In this paper the design of the ILC crab cavity and its phase control system, as selected for the RDR in February 2007 is described in fuller detail.

  9. Cavity-locked ring down spectroscopy

    SciTech Connect

    Zare, Richard N. (Stanford, CA); Paldus, Barbara A. (Stanford, CA); Harb, Charles C. (Palo Alto, CA); Spence, Thomas (Union City, CA)

    2000-01-01

    Distinct locking and sampling light beams are used in a cavity ring-down spectroscopy (CRDS) system to perform multiple ring-down measurements while the laser and ring-down cavity are continuously locked. The sampling and locking light beams have different frequencies, to ensure that the sampling and locking light are decoupled within the cavity. Preferably, the ring-down cavity is ring-shaped, the sampling light is s-polarized, and the locking light is p-polarized. Transmitted sampling light is used for ring-down measurements, while reflected locking light is used for locking in a Pound-Drever scheme.

  10. Large Scale Shape Optimization for Accelerator Cavities

    SciTech Connect

    Akcelik, Volkan; Lee, Lie-Quan; Li, Zenghai; Ng, Cho; Xiao, Li-Ling; Ko, Kwok; /SLAC

    2011-12-06

    We present a shape optimization method for designing accelerator cavities with large scale computations. The objective is to find the best accelerator cavity shape with the desired spectral response, such as with the specified frequencies of resonant modes, field profiles, and external Q values. The forward problem is the large scale Maxwell equation in the frequency domain. The design parameters are the CAD parameters defining the cavity shape. We develop scalable algorithms with a discrete adjoint approach and use the quasi-Newton method to solve the nonlinear optimization problem. Two realistic accelerator cavity design examples are presented.

  11. [Dirofilaria in the abdominal cavity].

    PubMed

    Révész, Erzsébet; Markovics, Gabriella; Darabos, Zoltán; Tóth, Ildikó; Fok, Eva

    2008-10-01

    Number of cases of filariasis have been recently reported in the Hungarian medical literature, most of them caused by Dirofilaria repens . Dirofilaria repens is a mosquito-transmitted filarioid worm in the subcutaneous tissue of dogs and cats. Human infection manifests as either subcutaneous nodules or lung parenchymal disease, which may even be asymptomatic. The authors report a human Dirofilaria repens infection of the abdominal cavity in a 61-year-old man,who underwent laparotomy for acute abdomen. Intraoperatively, local peritonitis was detected caused by a white nemathhelminth, measured 8 cm in size. Histocytology confirmed that the infection was caused by Dirofilaria repens. PMID:19028661

  12. Mass renormalization in cavity QED

    SciTech Connect

    Matloob, Reza [Department of Physics, University of Kerman, Kerman (Iran, Islamic Republic of)

    2011-01-15

    We show that the presence of a background medium and a boundary surface or surfaces in cavity QED produces no change in the energy shift of a free charged particle due to its coupling to the fluctuating electromagnetic field of the vacuum. This clarifies that the electromagnetic and the observed mass of the charged particle are not affected by the modification of the field of the vacuum. The calculations are nonrelativistic and restricted to the dipole approximation but are otherwise based on the general requirements of causality.

  13. A terahertz plasmon cavity detector

    SciTech Connect

    Dyer, G. C.; Vinh, N. Q.; Allen, S. J. [Institute for Terahertz Science and Technology, UC Santa Barbara, Santa Barbara, California 93106 (United States); Aizin, G. R.; Mikalopas, J. [Kingsborough College, City University of New York, Brooklyn, New York 11235 (United States); Reno, J. L.; Shaner, E. A. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)

    2010-11-08

    Sensitivity of a plasmonic detector is enhanced by integrating a broadband log-periodic antenna with a two-dimensional plasma cavity that is defined by source, drain, and multiple gates of a GaAs/AlGaAs high electron mobility transistor. Both narrow-band terahertz detection and a rich harmonic spectrum are evident. With a bolometric sensor in the channel, we report responsivity, on resonance at 235-240 GHz and at 20 K, of up to 7 kV/W and a noise equivalent power of 5x10{sup -10} W/Hz{sup 1/2}.

  14. Cavities

    MedlinePLUS

    ... around it. Silver amalgam (a combination of silver, mercury, copper, tin, and, occasionally, zinc, palladium, or indium) ... oral hygiene is good. The minute amount of mercury that escapes from silver amalgam is too small ...

  15. Asymptomatic Metastasis of Hepatocellular Carcinoma into the Right Ventricular Cavity Presenting with Electrocardiographic Changes

    Microsoft Academic Search

    Yu-Chun Liu; Chi-Sheng Hung; Shang-Yih Chan; Yung Wei Chen; Chia-Tung Shun; Ling-Ping Lai

    We report a 45-year-old woman with metastasis of hepatocellular carcinoma into the right ventricular cavity. She was asymptomatic when the metastasis was found and the clinical clue was an ECG with low voltage in limb leads and diffuse T-wave inversion. Echocardiography and magnetic resonance imaging were performed for the abnormal ECG finding and a right ventricular tumor was identified. Although

  16. Comprehensive numerical modeling of vertical-cavity surface-emitting lasers

    Microsoft Academic Search

    G. Ronald Hadley; K. L. Lear; M. E. Warren; K. D. Choquette; J. W. Scott; S. W. Corzine

    1996-01-01

    We present a comprehensive numerical model for vertical-cavity surface-emitting lasers that includes all major processes affecting cw operation of axisymmetric devices. In particular, our model includes a description of the 2-D transport of electrons and holes through the cladding layers to the quantum well(s), diffusion and recombination of these carriers within the wells, the 2-D transport of heat throughout the

  17. Wafer-bonded 1.3-um vertical cavity surface emitting lasers

    Microsoft Academic Search

    Yanyan Xiong; Jizhi Zhang; Yu-Hwa Lo

    1998-01-01

    Numerical analysis of the current spreading and carrier diffusion problem for four popular long wavelength vertical- cavity surface-emitting lasers (VCSELs) structures is presented. The results show that current confinement for p- mirror VCSELs is twice as effective as the corresponding n- mirror VCSELs. We also demonstrate the design, fabrication and device characterization for long wavelength 1.3 micrometers VCSELs, where oxygen-implanted

  18. First-wall protection in particle-beam fusion reactors by inert cavity gases

    NASA Astrophysics Data System (ADS)

    Moses, G. A.; Peterson, R. R.

    1980-07-01

    Results of hydrodynamics calculations, including radiation diffusion, are reported for spherical blast waves that will occur in light-ion-beam fusion reactor cavities filled with a noble gas to protect the first wall. Calculations for argon show that the radiant heat pulse on a 4 m-radius wall is likely to be excessively large for reactor applications. This is due to high transparency or argon (and other

  19. Cavity Ring-Down and Cavity-Enhanced Detection Techniques for the Measurement of Aerosol Extinction

    Microsoft Academic Search

    Hans Moosmüller; Ravi Varma; W. Patrick Arnott

    2005-01-01

    An instrument employing cavity ring-down (CRD) and cavity-enhanced detection (CED) for the local measurement of aerosol extinction is described and demonstrated. CRD measures the lifetime of photons in a high-quality optical cavity and thereby determines the sum of sample extinction between the cavity mirrors and that due to mirror losses. CRD systems can be calibrated with a single gas for

  20. Industrial Development of Cornell Superconducting Cavities for CEBAF

    SciTech Connect

    Palussek, A.; Heidt, Albert; Chargin, Anthony; Matheissen, Axel; Moss, Barry; Reece, Charles; Huppelsberg, D.; Morse, D.; Coulombe, Donald; Connor, E.; Palmer, F.; Biallas, George; Heinrichs, H.; Phillips, H.; Padamsee, Hasan; Piel, Helmut; Vogel, Helmut; Hager, J.; Parkinson, James; Brawley, John; Amato, Joseph; L. Kirchgessner, Joseph; Garner, June; Nakajima, K.; Schulz, K.; Peiniger, M.; Tigner, Maury; Weller, P.; Fleck, R.; Roth, R.; Sundelin, Ronald; Loer, S.; Herb, Steve; Grundey, T.; Klin, U.; Bensiek, W.

    1986-01-01

    Properties of the Cornell five-cell superconducting accelerating cavity and the suitability of this cavity for the CEBAF linac are discussed.The advanced technology required to produce these cavities was already known to some companies and is being transferred to others.The status of development of these cavities by industry, including test results on three of these cavities is discussed.

  1. Hydrodynamically induced fluid transfer and non-convective double-diffusion in microgravity sliding solvent diffusion cells

    NASA Technical Reports Server (NTRS)

    Pollmann, Konrad W.; Stodieck, Louis S.; Luttges, Marvin W.

    1994-01-01

    Microgravity can provide a diffusion-dominated environment for double-diffusion and diffusion-reaction experiments otherwise disrupted by buoyant convection or sedimentation. In sliding solvent diffusion cells, a diffusion interface between two liquid columns is achieved by aligning two offset sliding wells. Fluid in contact with the sliding lid of the cavities is subjected to an applied shear stress. The momentum change by the start/stop action of the well creates an additional hydrodynamical force. In microgravity, these viscous and inertial forces are sufficiently large to deform the diffusion interface and induce hydrodynamic transfer between the wells. A series of KC-135 parabolic flight experiments were conducted to characterize these effects and establish baseline data for microgravity diffusion experiments. Flow visualizations show the diffusion interface to be deformed in a sinusoidal fashion following well alignment. After the wells were separated again in a second sliding movement, the total induced liquid transfer was determined and normalized by the well aspect ratio. The normalized transfer decreased linearly with Reynolds number from 3.3 to 4.0% (w/v) for Re = 0.4 (Stokes flow) to a minimum of 1.0% for Re = 23 to 30. Reynolds numbers that provide minimum induced transfers are characterized by an interface that is highly deformed and unsuitable for diffusion measurements. Flat diffusion interfaces acceptable for diffusion measurements are obtained with Reynolds numbers on the order of 7 to 10. Microgravity experiments aboard a sounding rocket flight verified counterdiffusion of different solutes to be diffusion dominated. Ground control experiments showed enhanced mixing by double-diffusive convection. Careful selection of experimental parameters improves initial conditions and minimizes induced transfer rates.

  2. Diffusion Confusion 8 4 Problem set #4: Fun with diffusion

    E-print Network

    Spiegelman, Marc W.

    Diffusion Confusion 8 4 Problem set #4: Fun with diffusion Today's thrill packed exercise will be to deal with diffusion and advection-diffusion in one dimension. All exercises here will be in Matlab-nicolson diffusion of a gaussian initial condition with dirichlet boundary conditions (Diffusion/diffusion cn

  3. Measurement of linewidth variation within one external cavity mode of a grating-cavity laser

    Microsoft Academic Search

    G. Gentya; M. Kaivola; H. Ludvigsen

    2000-01-01

    We have investigated the dependence of the linewidth of a grating-cavity laser on the fine-tuning of the grating dispersion curve relative to the external cavity modes. Variations on the order of 100 kHz were observed experimentally when tuning the laser frequency within one external cavity mode

  4. Fermi-Compton scattering due to magnetopause surface fluctuations in Jupiter's magnetospheric cavity

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1981-01-01

    The effects of boundary surface fluctuations on a spectrum of electromagnetic radiation trapped in a high Q (quality) cavity are considered. Undulating walls introduce small frequency shifts at reflection to the radiation, and it is argued that the process is entirely analogous to both Fermi (particle) acceleration and inverse Compton scattering. A Fokker-Planck formalism is pursued; it yields a diffusion equation in frequency for which the Green's function and steady-state solutions are found. Applying this analysis to the Jovian continuum radiation discovered by Voyager spacecraft, it is suggested that characteristic diffusion times are greater than 1 year, and that in order to account for the steep frequency spectra observed, an unidentified loss mechanism must operate in the cavity with a decay time constant approximately equal to the characteristic diffusion time divided by 28. A radiator-reactor model of the cavity is investigated to provide an estimate for the intrinsic luminosity of the low frequency (approximately 100 Hz) continuum source whose power is approximately 7 x 10 to the 6th W.

  5. H 2O diffusion in rhyolitic melts and glasses

    Microsoft Academic Search

    Youxue Zhang; Harald Behrens

    2000-01-01

    H2O diffusion plays a major role in bubble growth and volcanic eruption. We report a comprehensive study of H2O diffusion in rhyolitic melts and glasses. This new study and previous investigations together cover a wide range of conditions: 400–1200°C, 0.1–810 MPa, and 0.1–7.7 wt.% total H2O content (H2Ot). In order to constrain how the diffusivity depends on H2Ot, both the

  6. Congenital diffuse infiltrating facial lipomatosis

    PubMed Central

    Balaji, S. M.

    2012-01-01

    Congenital diffuse infiltrating lipomatosis of the face (CDIL-F) is a rare pathological entity belonging to the subgroup of lipomatous tumors. Till date only a handful of cases has been documented and known to occur exclusively in infancy. On microscopical examination, it is characterized by diffuse infiltration of mature adipose tissue over normal muscle fibers, rapid growth, associated osseous hyperplasia, and a high recurrence rate after surgical intervention. An attempt has been made to identify and characterize all the 49 documented cases of CDIL-F in literature along with describing a report of a male child with CDIL-F. Follow-up of 8 years has been documented. The pathogenesis and spectrum of treatment modality are discussed with identified clinical features. PMID:23483013

  7. Breakthrough: Record-Setting Cavity

    SciTech Connect

    Ciovati, Gianluigi

    2012-03-01

    Gianluigi "Gigi" Ciovati, a superconducting radiofrequency scientist, discusses how scientists at the U.S. Department of Energy's Jefferson Lab in Newport News, VA, used ARRA funds to fabricate a niobium cavity for superconducting radiofrequency accelerators that has set a world record for energy efficiency. Jefferson Lab's scientists developed a new, super-hot treatment process that could soon make it possible to produce cavities more quickly and at less cost, benefitting research and healthcare around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.

  8. Multi-color Cavity Metrology

    E-print Network

    Kiwamu Izumi; Koji Arai; Bryan Barr; Joseph Betzwieser; Aidan Brooks; Katrin Dahl; Suresh Doravari; Jennifer C. Driggers; W. Zach Korth; Haixing Miao; Jameson Rollins; Stephen Vass; David Yeaton-Massey; Rana X. Adhikari

    2012-05-24

    Long baseline laser interferometers used for gravitational wave detection have proven to be very complicated to control. In order to have sufficient sensitivity to astrophysical gravitational waves, a set of multiple coupled optical cavities comprising the interferometer must be brought into resonance with the laser field. A set of multi-input, multi-output servos then lock these cavities into place via feedback control. This procedure, known as lock acquisition, has proven to be a vexing problem and has reduced greatly the reliability and duty factor of the past generation of laser interferometers. In this article, we describe a technique for bringing the interferometer from an uncontrolled state into resonance by using harmonically related external fields to provide a deterministic hierarchical control. This technique reduces the effect of the external seismic disturbances by four orders of magnitude and promises to greatly enhance the stability and reliability of the current generation of gravitational wave detector. The possibility for using multi-color techniques to overcome current quantum and thermal noise limits is also discussed.

  9. Local strain induced anisotropic diffusion )-Au(111) surface

    E-print Network

    Gong, Xingao

    by Elsevier Science B.V. Keywords: Surface diffusion; Surface stress; Surface structure, morphology, roughness surface-related phenomena, such as crystal growth, adsorption, corrosion, and surface reconstruction, etcLocal strain induced anisotropic diffusion on (23 Â ffiffiffi 3 p )-Au(111) surface Y.B. Liu a , D

  10. Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity,

    E-print Network

    Cambridge, University of

    of both substitutional niobium and interstitial carbon. Because these two types of solute diffuse at veryModelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity, and coarsening N. Fujita and H. K. D. H. Bhadeshia The growth of niobium carbide in austenite involves

  11. Advertising and the Diffusion of New Products

    Microsoft Academic Search

    Dan Horsky; Leonard S. Simon

    1983-01-01

    This paper examines the effects of advertising on the sales growth of new, infrequently purchased products. It is assumed that producer originated advertising serves to inform innovators of the existence and value of the new product while word-of-mouth communication by previous adopters affects imitators. Such a diffusion process is modeled and tested for the case of telephonic banking. It is

  12. Human Capital, International Trade and Technology Diffusion

    Microsoft Academic Search

    Thomas Bassetti

    2010-01-01

    This paper investigates the role played by trade openness in the process of international technology diffusion. Starting from the model provided by Benhabib and Spiegel (2005), here we show that the impact of trade openness on productivity growth is nonlinear. In particular, we will see how for low levels of trade openness a trade liberalization policy will reduce the rate

  13. Survival analysis of a critical resource for cavity-nesting communities: patterns of tree cavity longevity.

    PubMed

    Edworthy, Amanda B; Wiebe, Karen L; Martin, Kathy

    2012-09-01

    Tree cavities are a vital multi-annual resource used by cavity-nesting birds and mammals for nesting and shelter. The abundance of this resource will be influenced by the rates at which cavities are created and destroyed. We applied the demographic concepts of survival and longevity to populations of tree holes to investigate rates of loss for cavities in three tree species, as well as how characteristics of nest trees, habitat type, and species of excavator affected the persistence of tree cavities in trembling aspen, Populus tremuloides (95% of cavities were in aspen trees), in interior British Columbia, Canada. By modeling survival of 1635 nesting cavities in aspen over a time span of 16 years, we found that the decay stage of the nest tree was the most important factor determining cavity longevity. Cavities in trees with advanced decay had a relatively short median longevity of 7 years (95% CI 6-9 years), whereas those in living trees had a median longevity of more than 15 years. We found that cavity longevity was greater in continuous forest than in aspen grove habitat. Interestingly, cavities formed by weak excavators survived as long as those created by Northern Flickers (Colaptes auratus), despite occurring in more decayed tree stems. Thus, weak excavators may be selecting for characteristics that make a tree persistent, such as a broken top. Our results indicate that retention of cavities in large, live aspen trees is necessary to conserve persistent cavities, and that cavity longevity will have a large effect on the structure and function of cavity-using vertebrate communities. PMID:23092011

  14. Diffusion on spatial network

    NASA Astrophysics Data System (ADS)

    Hui, Zi; Tang, Xiaoyue; Li, Wei; Greneche, Jean-Marc; Wang, Qiuping A.

    2015-04-01

    In this work, we study the problem of diffusing a product (idea, opinion, disease etc.) among agents on spatial network. The network is constructed by random addition of nodes on the planar. The probability for a previous node to be connected to the new one is inversely proportional to their spatial distance to the power of ?. The diffusion rate between two connected nodes is inversely proportional to their spatial distance to the power of ? as well. Inspired from the Fick's first law, we introduce the diffusion coefficient to measure the diffusion ability of the spatial network. Using both theoretical analysis and Monte Carlo simulation, we get the fact that the diffusion coefficient always decreases with the increasing of parameter ? and ?, and the diffusion sub-coefficient follows the power-law of the spatial distance with exponent equals to -?-?+2. Since both short-range diffusion and long-range diffusion exist, we use anomalous diffusion method in diffusion process. We get the fact that the slope index ? in anomalous diffusion is always smaller that 1. The diffusion process in our model is sub-diffusion.

  15. Laser nozzle and optical cavity wall construction

    Microsoft Academic Search

    Kah; C. L. C

    1978-01-01

    A laser nozzle and optical cavity wall construction is formed of a plurality of stacked blocks bonded together to prevent inter-nozzle leakage and optical cavity sidewall mismatch in the flow area. The blocks are formed having end sections which are bonded together with contoured center sections forming the plurality of nozzles and with integral elongated projections extending downstream to form

  16. Dielectric detection by an electromagnetic cavity method

    Microsoft Academic Search

    James C. Weatherall; Howard F. Beckley; Joseph A. Gatto

    2004-01-01

    A method to screen for flammable and explosive materials in bottles by electromagnetic measurement is described. The technique makes use of an aluminum cavity having strong electromagnetic resonances in the radio wave band. An object inserted into the cavity changes the internal field configuration, and causes small, but measurable shifts in the resonant frequencies. The response depends on the electrical

  17. Cavity-enhanced detection of surface photovaporization

    Microsoft Academic Search

    E. C. Benck; Z. Rong; S. H. Chen; Z. C. Tang; H. A. Schuessler

    1991-01-01

    Cavity-enhanced detection is used to monitor minute vapor plumes produced by focusing a pulsed laser beam onto a surface placed inside a resonant optical cavity. The photovaporization signals from a variety of different materials are examined, with emphasis being placed on their amplitude and temporal structure.

  18. Cavity dumping for free electron lasers

    Microsoft Academic Search

    Antonello Cutolo; Stephen V. Benson; John F. Schultz; John M. Madey

    1989-01-01

    The application of the cavity dumping technique to free electron lasers (FEL) is described. Particular attention is given to the problem of the switching time of the dumper. Electrooptic and acoustooptic configurations are described and the change in the extraction efficiency is discussed. The basic design criteria are discussed with reference to the cavity dumping experiment in progress on the

  19. Cavity dumping for free electron lasers

    Microsoft Academic Search

    Antonello Cutolo; Stephen V. Benson; John F. Schultz; John M. Madey

    1989-01-01

    The cavity dumping technique, applied to free electron lasers (FEL), is described. Taking advantage of both numerical simulations and experimental results on the Mark III FEL, a fairly exhaustive analysis is reported. In particular, we show that the output peak power can be increased by a factor even higher than one hundred. The cavity dumping experiment, under way on the

  20. Cavity-based single-photon sources

    Microsoft Academic Search

    Axel Kuhn; Daniel Ljunggren

    2010-01-01

    We introduce the basic concepts and characteristic properties of single-photon emitters based on resonator effects in optical cavities, and provide a review of the most prominent implementations. First we discuss the elementary principles of cavity quantum electrodynamics, which determine how single quantum systems couple to the quantised field modes of optical resonators, and then show how to exploit these principles

  1. Atomic Layer Deposition for SRF Cavities

    Microsoft Academic Search

    J. Norem; J. W. Elam; M. J. Pellin; C. Z. Antoine; G. Ciovati; P. Kneisel; C. E. Reece; R. A. Rimmer; L. Cooley; A. V. Gurevich; Y. Ha; Th. Proslier; J. Zasadzinski

    2009-01-01

    We have begun using Atomic Layer Deposition (ALD) to synthesize a variety of surface coatings on coupons and cavities as part of an effort to produce rf structures with significantly better performance and yield than those obtained from bulk niobium, The ALD process offers the possibility of conformally coating complex cavity shapes with precise layered structures with tightly constrained morphology

  2. Large grain cavities from pure niobium ingot

    DOEpatents

    Myneni, Ganapati Rao (Yorktown, VA); Kneisel, Peter (Williamsburg, VA); Cameiro, Tadeu (McMurray, PA)

    2012-03-06

    Niobium cavities are fabricated by the drawing and ironing of as cast niobium ingot slices rather than from cold rolled niobium sheet. This method results in the production of niobium cavities having a minimum of grain boundaries at a significantly reduced cost as compared to the production of such structures from cold rolled sheet.

  3. Compact microwave cavity for hydrogen atomic clock

    NASA Technical Reports Server (NTRS)

    Zhang, Dejun; Zhang, Yan; Fu, Yigen; Zhang, Yanjun

    1992-01-01

    A summary is presented that introduces the compact microwave cavity used in the hydrogen atomic clock. Special emphasis is placed on derivation of theoretical calculating equations of main parameters of the microwave cavity. A brief description is given of several methods for discriminating the oscillating modes. Experimental data and respective calculated values are also presented.

  4. Geometric Model of a Coronal Cavity

    NASA Technical Reports Server (NTRS)

    Kucera, Therese A.; Gibson, S. E.; Ratawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Reeves, K. K.; Schmidt, D. J.; Sterling, A. C.; Tripathi, D. K.; Williams, D. R.; Zhang, M.

    2010-01-01

    We observed a coronal cavity from August 8-18 2007 during a multi-instrument observing campaign organized under the auspices of the International Heliophysical Year (IHY). Here we present initial efforts to model the cavity with a geometrical streamer-cavity model. The model is based the white-light streamer mode] of Gibson et a]. (2003 ), which has been enhanced by the addition of a cavity and the capability to model EUV and X-ray emission. The cavity is modeled with an elliptical cross-section and Gaussian fall-off in length and width inside the streamer. Density and temperature can be varied in the streamer and cavity and constrained via comparison with data. Although this model is purely morphological, it allows for three-dimensional, multi-temperature analysis and characterization of the data, which can then provide constraints for future physical modeling. Initial comparisons to STEREO/EUVI images of the cavity and streamer show that the model can provide a good fit to the data. This work is part of the effort of the International Space Science Institute International Team on Prominence Cavities

  5. Unstable confocal resonator cavity alignment system

    Microsoft Academic Search

    R. Guthrie; T. B. Mc Donald; D. Anafi

    1987-01-01

    An optical alignment system is described for controlling the relative orientation of a second mirror with respect to the orientation of a convex cavity surface of a first mirror in a high-power optical cavity. The system comprises: an alignment laser for generating an alignment beam; a controlled steering mirror for adjusting the direction of propagation of the alignment beam; first

  6. Performance Of Superconducting-Cavity Maser

    NASA Technical Reports Server (NTRS)

    Dick, G. John; Wang, Rabi T.

    1991-01-01

    Report describes experiments on operation of superconducting-cavity maser - all-cryogenic oscillator. Operates with degree of stability, at short measuring times, superior to that achievable by any other means. All components designed for cryogenic operation and stabilizing cavity very rigid, consisting of sapphire filling coated with lead.

  7. A CAVITY PROBLEM FOR MAXWELL'S EQUATIONS

    Microsoft Academic Search

    HABIB AMMARI; GANG BAO; AIHUA W. WOOD

    2002-01-01

    Consider a time-harmonic electromagnetic plane wave incident on a cavity in a ground plane. Inside the cavity, the medium may be nonhomogeneous. In this paper, a variational formulation is studied. Existence and uniqueness of the solutions for the model problem are estab- lished by a variational approach and the Hodge decomposition. The variational approach also forms a basis for numerical

  8. Hydrogen masers with cavity frequency switching servos

    NASA Technical Reports Server (NTRS)

    Peters, Harry E.; Owings, H. B.; Koppang, Paul A.

    1990-01-01

    The stability of the free-running hydrogen maser is limited by pulling of the unperturbed hydrogen transition frequency due to instability of the cavity resonance frequency. While automatic spin-exchange tuning is in principle the more basic and accurate method, the required beam intensity switching and the long servo time constant result in reduced stability for measuring intervals up to 10(exp 6) seconds. More importantly, the spin-exchange tuning method requires a second stable frequency source as a reference, ideally a second hydrogen maser, to get the best results. The cavity frequency switching servo, on the other hand, has very little effect on the maser short term stability, and is fast enough to correct for cavity drift while maintaining the cavity at the spin-exchange tuned offset required to minimize instability due to beam intensity fluctuations. Not only does the cavity frequency switching servo not require a second stable frequency source, but the frequency reference is the atomic hydrogen radiated beam signal, so that no extra RF connections need be made to the cavity, and externally generated signals that would perturb the hydrogen atom need not be transmitted through the cavity. The operation of the cavity frequency switching stabilization method is discussed and the transient response of the servo and certain other aspects of the technique that have potential for achieving improved basic accuracy are illustrated.

  9. Pulsating intensities in external cavity semiconductor lasers

    Microsoft Academic Search

    V. Kovanis; A. Gavrielides

    2000-01-01

    We have investigated the dynamics of external cavity diode lasers, (L?1 cm or shorter), in the context of the single mode single delay Lang-Kobayashi (LK) model. We find that the laser undergoes a sequence of three Hopf bifurcations from the same external cavity mode, as the feedback rate and the roundtrip time are varied. As we increase the feedback rate

  10. Performance experience with the CEBAF SRF cavities

    Microsoft Academic Search

    C. Reece; J. Benesch; M. Drury; C. Hovater; J. Mammosser; T. Powers; J. Preble

    1995-01-01

    The full complement of 169 pairs of niobium superconducting cavities has been installed in the CEBAF accelerator. This paper surveys the performance characteristics of these cavities in vertical tests, commissioning in the tunnel, and operational experience to date. Although installed performance exceeds specifications, and 3.2 GeV beam has been delivered on target, present systems do not consistently preserve the high

  11. Strategies for waveguide coupling for SRF cavities

    Microsoft Academic Search

    Lawrence R. Doolittle

    1998-01-01

    Despite widespread use of coaxial couplers in SRF cavities, a single, simple waveguide coupling can be used both to transmit generator power to a cavity, and to remove a large class of Higher Order Modes (HOMs, produced by the beam). There are balances and tradeoffs to be made, such as the coupling strength of the various frequencies, the transverse component

  12. Control of cavity resonance using oscillatory blowing

    Microsoft Academic Search

    Alison Lamp Scarfe

    2000-01-01

    The near-zero net mass oscillatory blowing control of a subsonic cavity flow has been experimentally investigated. An actuator was designed and fabricated to provide both steady and oscillatory blowing over a range of blowing amplitudes and forcing frequencies. The blowing was applied just upstream of the cavity front wall through interchangeable plate configurations. These configurations enabled the effects of hole

  13. Cavity Enhancement by Madtoms (Genus Noturus)

    Microsoft Academic Search

    Philip A. Cochran

    1996-01-01

    Three species of madtoms (Noturus flavus, N. funebris, and N. gyrinus) were observed enlarging cavities beneath rocks by moving gravel in their mouths. This behavioral trait is probably widespread within the genus Noturus and occurs in other ictalurids. An experiment with N. gyrinus failed to demonstrate creation of new cavities beneath tiles laid flat on the bottom.

  14. Fundamental Power Couplers for Superconducting Cavities

    Microsoft Academic Search

    Isidoro E. Campisi

    2001-01-01

    Fundamental power couplers (FPC's) for superconducting cavities must meet very strict requirements to perform at high power levels (hundreds of kilowatts) and in a variety of conditions (CS, pulsed, travelling wave, standing wave) without adversely affecting the performance of the cavities they are powering. Producing good coupler designs and achieving operational performances in accelerator environments are challenging tasks that have

  15. Mode suppression means for gyrotron cavities

    DOEpatents

    Chodorow, Marvin (Stanford, CA); Symons, Robert S. (Los Altos, CA)

    1983-08-09

    In a gyrotron electron tube of the gyro-klystron or gyro-monotron type, having a cavity supporting an electromagnetic mode with circular electric field, spurious resonances can occur in modes having noncircular electric field. These spurious resonances are damped and their frequencies shifted by a circular groove in the cavity parallel to the electric field.

  16. Experimental Investigations on Superconducting Niobium Cavities

    E-print Network

    . . . . . . . . . . . . . . . 16 1.4.1.2 Deep drawing and electron-beam welding . . . 17 1.4.2 Cavity treatmentExperimental Investigations on Superconducting Niobium Cavities at Highest Radiofrequency Fields.3.2.4 Microwave skin e#11;ect in normal metals . . . . 9 1.3.3 Radiofrequency critical magnetic #12;eld

  17. Cavity-QED-based quantum phase gate 

    E-print Network

    Zubairy, M. Suhail; Kim, M.; Scully, Marlan O.

    2003-01-01

    We describe a quantum phase gate in which the two qubits are represented by the photons in the two modes of the cavity field. The gate is implemented by passing a three-level atom in a cascade configuration through the cavity. The upper levels...

  18. Cavity-enhanced dual-comb spectroscopy

    Microsoft Academic Search

    Birgitta Bernhardt; Akira Ozawa; Patrick Jacquet; Marion Jacquey; Yohei Kobayashi; Thomas Udem; Ronald Holzwarth; Guy Guelachvili; Theodor W. Hänsch; Nathalie Picqué

    2010-01-01

    The sensitivity of molecular fingerprinting is dramatically improved when the absorbing sample is placed in a high-finesse optical cavity, because the effective path length is increased. When the equidistant lines from a laser frequency comb are simultaneously injected into the cavity over a large spectral range, multiple trace gases may be identified within a few milliseconds. However, efficient analysis of

  19. Computing Rates of Small Molecule Diffusion Through Protein Channels Using Markovian Milestoning

    NASA Astrophysics Data System (ADS)

    Abrams, Cameron

    2014-03-01

    Measuring diffusion rates of ligands plays a key role in understanding the kinetic processes inside proteins. For example, although many molecular simulation studies have reported free energy barriers to infer rates for CO diffusion in myoglobin (Mb), they typically do not include direct calculation of diffusion rates because of the long simulation times needed to infer these rates with statistical accuracy. We show in this talk how to apply Markovian milestoning along minimum free-energy pathways to calculate diffusion rates of CO inside Mb. In Markovian milestoning, one partitions a suitable reaction coordinate space into regions and performs restrained molecular dynamics in each region to accumulate kinetic statistics that, when assembled across regions, provides an estimate of the mean first-passage time between states. The mean escape time for CO directly from the so-called distal pocket (DP) through the histidine gate (HG) is estimated at about 24 ns, confirming the importance of this portal for CO. But Mb is known to contain several internal cavities, and cavity-to-cavity diffusion rates are also computed and used to build a complete kinetic network as a Markov state model. Within this framework, the effective mean time of escape to the solvent through HG increases to 30 ns. Our results suggest that carrier protein structure may have evolved under pressure to modulate dissolved gas release rates using a network of ligand-accessible cavities. Support: NIH R01GM100472.

  20. Stochastic models for tumoral growth

    NASA Astrophysics Data System (ADS)

    Escudero, Carlos

    2006-02-01

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

  1. Uncoupled achromatic condition of a dog-leg system with the presence of RF cavities

    NASA Astrophysics Data System (ADS)

    Geng, Hui-Ping; Guo, Zhen

    2014-06-01

    To merge the beam from either of the two injectors to the main linac, a dog-leg system will be employed in the second Medium Energy Beam Transport (MEBT2) line of the China ADS driving accelerator. The achromatic condition has to be guaranteed to avoid beam center excursion against energy jitter. RF cavities were found to be indispensable to control the bunch length growth in the dog-leg system of MEBT2. The full uncoupling between transverse and longitudinal plane is desired to minimize the growth of projected rms emittances. The uncoupled achromatic condition of this dogleg system with the presence of RF bunching cavities will be deduced using the transfer matrices method. It is found that, to fulfill the uncoupling condition, the distance between the bunching cavities is uniquely determined by the maximum energy gain of the RF cavities. The theoretical analysis is verified by the simulation code TraceWin. The space charge effect on the uncoupled achromatic condition and the beam emittance growth will also be discussed.

  2. Verruciform xanthoma of the oral cavity - a case report.

    PubMed

    Dorankula, Shyam Prasad Reddy; Ramani, Pratibha; Premkumar, Priya; Anuja; Sherlyn, Herald J

    2013-08-01

    Verruciform Xanthoma (VX) is a relatively rare benign mucocutaneous lesion of unknown aetiology. VX occurs predominantly in oral cavity which also occasionally affects skin and genital mucosa. It was first reported in the oral cavity in 1971. This rare harmless lesion usually presents as sessile or pedunculated, appear as a papule or single plaque showing verrucous or papillomatous mucosal growth with variable color from reddish pink to gray. In majority of oral cases, it affects gingiva and alveolar mucosa that may be mistaken for benign, premalignant and malignant conditions. VX is diagnosed with certainly only on histopathologic examination. Histologically VX is characterized by the presence of parakeratinized epithelium showing papillary or verrucous growth with thin rete ridges and connective tissue papillae extending up to the surface. The papillae characteristically consist of foam cells also called xanthoma cells. Here we describe a case report of verruciform xanthoma occurring on the buccal mucosa in a 42-years old male patient along with its clinical, pathogenesis, histological features and treatment modalities discussed. PMID:24086918

  3. Verruciform Xanthoma of the Oral Cavity – A Case Report

    PubMed Central

    Dorankula, Shyam Prasad Reddy; Ramani, Pratibha; Premkumar, Priya; Anuja; Sherlyn, Herald J

    2013-01-01

    Verruciform Xanthoma (VX) is a relatively rare benign mucocutaneous lesion of unknown aetiology. VX occurs predominantly in oral cavity which also occasionally affects skin and genital mucosa. It was first reported in the oral cavity in 1971. This rare harmless lesion usually presents as sessile or pedunculated, appear as a papule or single plaque showing verrucous or papillomatous mucosal growth with variable color from reddish pink to gray. In majority of oral cases, it affects gingiva and alveolar mucosa that may be mistaken for benign, premalignant and malignant conditions. VX is diagnosed with certainly only on histopathologic examination. Histologically VX is characterized by the presence of parakeratinized epithelium showing papillary or verrucous growth with thin rete ridges and connective tissue papillae extending up to the surface. The papillae characteristically consist of foam cells also called xanthoma cells. Here we describe a case report of verruciform xanthoma occurring on the buccal mucosa in a 42–years old male patient along with its clinical, pathogenesis, histological features and treatment modalities discussed. PMID:24086918

  4. On the accuracy of decay constant measurement by swept-cavity heterodyne cavity ringdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Silva, K. K. M. B. Dilusha; van der Walt, Aislinn; Dell, John M.; Faraone, Lorenzo

    2011-06-01

    Cavity ringdown spectroscopy (CRDS) measures the decay time, of a resonant optical cavity containing a measurand, as a function of optical frequency. The measurand is identified and quantified by the cavity decay time, which is modified by the measurand within. As coupling light into a high-finesse optical cavity is difficult, the throughput of the cavity is small. A recent variant, swept-cavity heterodyne CRDS, interferes backward escaping cavity light, with light reflected from the cavity input mirror, providing better signal sensitivity due to the heterodyne advantage. The measured interference signal is demodulated and log-amplified to produce a signal whose slope is representative of the cavity decay time. This paper, for the first time, examines the conditions required for high-fidelity measurements of the cavity decay time using swept-cavity heterodyne CRDS and log-amplification technique. We demonstrate that, due to the very large bandwidth and dynamic range of the log-amplifier, for realistic measurement conditions, the log-amplifier does not impose any significant restrictions on the measurement accuracy. We also demonstrate, however, the measurement accuracy is limited by two factors, the detector bandwidth, and segment of acquired data used to measure the slope.

  5. Fluid dynamics of spherical cavity reactors

    NASA Astrophysics Data System (ADS)

    Maya, Isaac; Christy, Craig; Dagher, Mohamad; Kim, Thomas; Williams, J. Richard

    This paper presents the results of fluid dynamic experiments of two-component flows in a spherical cavity. The experiment is directed at examining the required containment characteristics of the Spherical Gas Core Reactor. These characteristics include hydrodynamic containment of an inner fissile gas flow by the flow of an outer working fluid gas tangentially injected at the cavity wall and dispersal of the inner gas over a large fraction of the cavity volume. Favorable results have been obtained to date in air-air room temperature tests which show that the inner gas can be contained away from the cavity walls at flow rate ratios of outer to inner gas of 200/1 to 300/1. The inner gas was observed to occupy over 90 percent of the cavity volume. Tests with sulfur hexafluoride as the inner gas have yielded qualitatively similar results.

  6. Coupled Resonator Vertical Cavity Laser Diodes

    SciTech Connect

    Choquette, K.D.; Chow, W.W.; Fischer, A.J.; Allerman, A.A.; Hou, H.Q.; Geib, K.M.

    1999-07-22

    For many applications, the device performance of edge emitting semiconductor lasers can be significantly improved through the use of multiple section devices. For example, cleaved coupled cavity (C3) lasers have been shown to provide single mode operation, wavelength tuning, high speed switching, as well as the generation of short pulses via mode-locking and Q-switching [1]. Using composite resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the coupling between the monolithic cavities, incorporate passive or active resonators which are spectrally degenerate or detuned, and to fabricate these devices in 2-dimensional arrays. Composite resonator vertical cavity lasers (CRVCL) have been examined using optical pumping and electrical injection [2-5]. We report on CRVCL diodes and show that efficient modulation of the laser emission can be achieved by either forward or reverse biasing the passive cavity within a CRVCL.

  7. Large Grain Superconducting RF Cavities at DESY

    SciTech Connect

    Singer, W.; Brinkmann, A.; Ermakov, A.; Iversen, J.; Kreps, G.; Matheisen, A.; Proch, D.; Reschke, D.; Singer, X.; Spiwek, M.; Wen, H.; Brokmeier, H. G. [DESY, Notkestrasse 85, D-22607 Hamburg (Germany); GKSS, Max-Planck-Strasse, D-21502 Geesthacht (Germany)

    2007-08-09

    The DESY R and D program on cavities fabricated from large grain niobium explores the potential of this material for the production of approx. 1000 nine-cell cavities for the European XFEL. The program investigates basic material properties, comparing large grain material to standard sheet niobium, as well as fabrication and preparation aspects. Several single-cell cavities of TESLA shape have been fabricated from large grain niobium. A gradient up to 41 MV/m at Q0 = 1.4{center_dot}1010 (TB = 2K) was measured after electropolishing. The first three large grain nine-cell cavities worldwide have been produced under contract of DESY with ACCEL Instruments Co. The first tests have shown that all three cavities reach an accelerating gradient up to 30 MV/m after BCP (Buffered Chemical Polishing) treatment, what exceeds the XFEL requirements for RF test in the vertical cryostat.

  8. Automated Hydroforming of Seamless Superconducting RF Cavity

    SciTech Connect

    Nagata, Tomohiko [ULVAC, Inc.; Shinozawa, Seiichi [ULVAC, Inc.; Abe, Noriyuki [ULVAC, Inc.; Nagakubo, Junki [ULVAC, Inc.; Murakami, Hirohiko [ULVAC, Inc.; Tajima, Tsuyoshi [Los Alamos National Laboratory; Inoue, Hitoshi [High Energy Accelerator Research Organization, KEK; Yamanaka, Masashi [High Energy Accelerator Research Organization, KEK; Ueno, Kenji [High Energy Accelerator Research Organization, KEK

    2012-07-31

    We are studying the possibility of automated hydroforming process for seamless superconducting RF cavities. Preliminary hydroforming tests of three-cell cavities from seamless tubes made of C1020 copper have been performed. The key point of an automated forming is to monitor and strictly control some parameters such as operation time, internal pressure and material displacements. Especially, it is necessary for our studies to be able to control axial and radial deformation independently. We plan to perform the forming in two stages to increase the reliability of successful forming. In the first stage hydroforming by using intermediate constraint dies, three-cell cavities were successfully formed in less than 1 minute. In parallel, we did elongation tests on cavity-quality niobium and confirmed that it is possible to achieve an elongation of >64% in 2 stages that is required for our forming of 1.3 GHz cavities.

  9. Cavity cooling a single charged levitated nanosphere.

    PubMed

    Millen, J; Fonseca, P Z G; Mavrogordatos, T; Monteiro, T S; Barker, P F

    2015-03-27

    Optomechanical cavity cooling of levitated objects offers the possibility for laboratory investigation of the macroscopic quantum behavior of systems that are largely decoupled from their environment. However, experimental progress has been hindered by particle loss mechanisms, which have prevented levitation and cavity cooling in a vacuum. We overcome this problem with a new type of hybrid electro-optical trap formed from a Paul trap within a single-mode optical cavity. We demonstrate a factor of 100 cavity cooling of 400 nm diameter silica spheres trapped in vacuum. This paves the way for ground-state cooling in a smaller, higher finesse cavity, as we show that a novel feature of the hybrid trap is that the optomechanical cooling becomes actively driven by the Paul trap, even for singly charged nanospheres. PMID:25860743

  10. Cavity Cooling a Single Charged Levitated Nanosphere

    NASA Astrophysics Data System (ADS)

    Millen, J.; Fonseca, P. Z. G.; Mavrogordatos, T.; Monteiro, T. S.; Barker, P. F.

    2015-03-01

    Optomechanical cavity cooling of levitated objects offers the possibility for laboratory investigation of the macroscopic quantum behavior of systems that are largely decoupled from their environment. However, experimental progress has been hindered by particle loss mechanisms, which have prevented levitation and cavity cooling in a vacuum. We overcome this problem with a new type of hybrid electro-optical trap formed from a Paul trap within a single-mode optical cavity. We demonstrate a factor of 100 cavity cooling of 400 nm diameter silica spheres trapped in vacuum. This paves the way for ground-state cooling in a smaller, higher finesse cavity, as we show that a novel feature of the hybrid trap is that the optomechanical cooling becomes actively driven by the Paul trap, even for singly charged nanospheres.

  11. Performance of 3-cell Seamless Niobium cavities

    SciTech Connect

    Kneisel, Peter K. [JLAB; Ciovati, Gianluigi [JLBA; Jelezov, I. [DESY, Hamburg; Singer, W. [DESY, Hamburg; Singer, X. [DESY, Hamburg

    2009-11-01

    In the last several months we have surface treated and cryogenically tested three TESLA-type 3-cell cavities, which had been manufactured at DESY as seamless assemblies by hydroforming. The cavities were completed at JLab with beam tube/flange assemblies. All three cavities performed very well after they had been post-purified with titanium at 1250C for 3 hrs. The cavities, two of which consisted of an end cell and 2 center cells and one was a center cell assembly, achieved gradients of Eacc = 32 MV/m, 34 MV/m and 35 MV/m without quenches. The performance was limited by the appearance of the “Q-drop” in the absence of field emission. This contribution reports about the various measurements undertaken with these cavities.

  12. CAVITY-NEST WEBS IN A LONGLEAF PINE ECOSYSTEM

    Microsoft Academic Search

    LORI A. BLANC; JEFFREY R. WALTERS

    2008-01-01

    Cavity-nesting communities can be viewed as interconnected webs that interact through the creation of and competition for cavities as nest sites. Using a web approach, we depicted the flow of cavity creation and use in the cavity-nesting bird community of a Florida longleaf pine (Pinus palustris) ecosystem to examine the relationship between cavity-nesting bird abundance and cavity resources, and to

  13. Abstract--Hybrid diffusion imaging (HYDI) is a new diffusion MRI method for characterizing complex diffusion.

    E-print Network

    Bucci, David J.

    Abstract-- Hybrid diffusion imaging (HYDI) is a new diffusion MRI method for characterizing complex diffusion. Diffusion-weighted measurements are obtained on multiple `shells' of constant diffusion weighting. This diffusion encoding approach is amenable to multiple types of diffusion imaging analysis. The inner shells

  14. UPDATING APPLIED DIFFUSION MODELS

    EPA Science Inventory

    Most diffusion models currently used in air quality applications are substantially out of date with understanding of turbulence and diffusion in the planetary boundary layer. Under a Cooperative Agreement with the Environmental Protection Agency, the American Meteorological Socie...

  15. Memetic algorithms for ligand expulsion from protein cavities

    E-print Network

    Rydzewski, Jakub

    2015-01-01

    Ligand diffusion through a protein interior is a fundamental process governing biological signaling and enzymatic catalysis. A complex topology of channels in proteins leads often to difficulties in modeling ligand escape pathways by classical molecular dynamics simulations. In this paper two novel memetic methods for searching the exit paths and cavity space exploration are proposed: Memory Enhanced Random Acceleration (MERA) Molecular Dynamics and Immune Algorithm (IA). In MERA, a pheromone concept is introduced to optimize an expulsion force. In IA, hybrid learning protocols are exploited to predict ligand exit paths. They are tested on three protein channels with increasing complexity: M2 muscarinic GPCR receptor, enzyme nitrile hydratase and heme-protein cytochrome P450cam. In these cases, the memetic methods outperform Simulated Annealing and Random Acceleration Molecular Dynamics. The proposed algorithms are general and appropriate in all problems where an accelerated transport of an object through a n...

  16. Diffusion bonding aeroengine components

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, G. A.; Broughton, T.

    1988-10-01

    The use of diffusion bonding processes at Rolls-Royce for the manufacture of titanium-alloy aircraft engine components and structures is described. A liquid-phase diffusion bonding process called activated diffusion bonding has been developed for the manufacture of the hollow titanium wide chord fan blade. In addition, solid-state diffusion bonding is being used in the manufacture of hollow vane/blade airfoil constructions mainly in conjunction with superplastic forming and hot forming techniques.

  17. Pb diffusion in zircon

    Microsoft Academic Search

    D. J Cherniak; E. B Watson

    2001-01-01

    Diffusion of Pb was characterized in natural and synthetic zircon under a range of conditions. In most experiments, mixtures of Pb sulfate and ground zircon were used as the sources of diffusant, with Pb depth profiles measured with Rutherford Backscattering Spectrometry (RBS). As complement to these “in-diffusion” experiments, “out-diffusion” experiments were run on both synthetic Pb-doped and natural zircon with

  18. Cavity Optomechanics with Graphene Resonators

    NASA Astrophysics Data System (ADS)

    Barton, Robert; Storch, Isaac; Adiga, Vivekananda; Sakakibara, Reyu; Wang, Si Ping; Ong, Peijie; Ilic, B.; McEuen, Paul; Parpia, Jeevak; Craighead, Harold

    2012-02-01

    Optical manipulation of micromechanical and nanomechanical resonators promises control of quantum states of macroscopic systems, among other applications. Because the spring constant of a resonator scales with its mass, there are advantages associated with using the lightest possible membranes as the mechanical elements. Here, we demonstrate that graphene, a one-atom-thick membrane, can be used as the mechanically active part of an optomechanical system. We show that a laser coupled to a Fabry-Perot cavity between a graphene resonator and a reflective backplane can both enhance and damp graphene motion. The enhancement of resonator motion is sufficient to induce self-oscillation, which is useful for applications in sensing and signal processing. These experiments demonstrate that graphene resonators are useful for optomechanical applications and show promise for resonator cooling toward the quantum ground state.

  19. Mini-cavity-dumped laser

    NASA Technical Reports Server (NTRS)

    Reed, E.

    1981-01-01

    Lasers for use in high precision satellite ranging systems consist typically of an oscillator followed by several amplifier stages. While the shortest optical pulses are achieved by using a mode locked oscillator, such an oscillator is incompatible with the compact design needed in future, highly mobile systems. The laser oscillator achieves pulse lengths approaching those obtainable by mode locking, but in a much more compact and stable design. The oscillator uses two LiNbO3 Pockels cells inside the resonator. One Q-switches the oscillator, and the other is used in a pulse slicing scheme to cavity dump a portion of the circulating optical energy. The length of the optical output pulse measured at 425 + or - 50 picoseconds.

  20. FXR accelerator cavity impedance experiments

    SciTech Connect

    Avalle, C.A.

    1998-01-05

    One of the goals of the present Flash X-Ray (FXR) accelerator upgrade effort [1][2] at Lawrence Livermore National Laboratory (LLNL) is to reduce the cavity transverse impedance, since it has been shown that beam stability is significantly affected by this parameter [3]. Recently, we have evaluated various techniques and cell modifications to accomplish that, both through lab measurements and computer models. A spare cell, identical in every way to cells in the accelerator, was specially modified for the experiments. The impedance measurements were done without the beam, by applying twin-wire techniques. This report describes the results of these experiments and suggests possible cell modifications to improve their performance. The techniques and modifications which are suggested might also be applicable to AHF and DARHT-2 long-pulse accelerator development.

  1. Cavity approximation for graphical models.

    PubMed

    Rizzo, T; Wemmenhove, B; Kappen, H J

    2007-07-01

    We reformulate the cavity approximation (CA), a class of algorithms recently introduced for improving the Bethe approximation estimates of marginals in graphical models. In our formulation, which allows for the treatment of multivalued variables, a further generalization to factor graphs with arbitrary order of interaction factors is explicitly carried out, and a message passing algorithm that implements the first order correction to the Bethe approximation is described. Furthermore, we investigate an implementation of the CA for pairwise interactions. In all cases considered we could confirm that CA[k] with increasing k provides a sequence of approximations of markedly increasing precision. Furthermore, in some cases we could also confirm the general expectation that the approximation of order k , whose computational complexity is O(N(k+1)) has an error that scales as 1/N(k+1) with the size of the system. We discuss the relation between this approach and some recent developments in the field. PMID:17677405

  2. Handbook on atmospheric diffusion

    SciTech Connect

    Hanna, S.R.; Briggs, G.A.; Hosker, R.P. Jr.

    1982-01-01

    Basic meteorological concepts are covered as well as plume rise, source effects, and diffusion models. Chapters are included on cooling tower plumes and urban diffusion. Suggestions are given for calculating diffusion in special situations, such as for instantaneous releases over complex terrain, over long distances, and during times when chemical reactions or dry or wet deposition are important. (PSB)

  3. On streamline diffusion arising in Galerkin FEM with predictor/multi-corrector time integration

    NASA Astrophysics Data System (ADS)

    Eguchi, Yuzuru

    2002-08-01

    In the present paper, the author shows that the predictor/multi-corrector (PMC) time integration for the advection-diffusion equations induces numerical diffusivity acting only in the streamline direction, even though the equations are spatially discretized by the conventional Galerkin finite element method (GFEM). The transient 2-D and 3-D advection problems are solved with the PMC scheme using both the GFEM and the streamline upwind/Petrov Galerkin (SUPG) as the spatial discretization methods for comparison. The solutions of the SUPG-PMC turned out to be overly diffusive due to the additional PMC streamline diffusion, while the solutions of the GFEM-PMC were comparatively accurate without significant damping and phase error. A similar tendency was seen also in the quasi-steady solutions to the incompressible viscous flow problems: 2-D driven cavity flow and natural convection in a square cavity. Copyright

  4. Iron diffusion from first principles calculations

    NASA Astrophysics Data System (ADS)

    Wann, E.; Ammann, M. W.; Vocadlo, L.; Wood, I. G.; Lord, O. T.; Brodholt, J. P.; Dobson, D. P.

    2013-12-01

    The cores of Earth and other terrestrial planets are made up largely of iron1 and it is therefore very important to understand iron's physical properties. Chemical diffusion is one such property and is central to many processes, such as crystal growth, and viscosity. Debate still surrounds the explanation for the seismologically observed anisotropy of the inner core2, and hypotheses include convection3, anisotropic growth4 and dendritic growth5, all of which depend on diffusion. In addition to this, the main deformation mechanism at the inner-outer core boundary is believed to be diffusion creep6. It is clear, therefore, that to gain a comprehensive understanding of the core, a thorough understanding of diffusion is necessary. The extremely high pressures and temperatures of the Earth's core make experiments at these conditions a challenge. Low-temperature and low-pressure experimental data must be extrapolated across a very wide gap to reach the relevant conditions, resulting in very poorly constrained values for diffusivity and viscosity. In addition to these dangers of extrapolation, preliminary results show that magnetisation plays a major role in the activation energies for diffusion at low pressures therefore creating a break down in homologous scaling to high pressures. First principles calculations provide a means of investigating diffusivity at core conditions, have already been shown to be in very good agreement with experiments7, and will certainly provide a better estimate for diffusivity than extrapolation. Here, we present first principles simulations of self-diffusion in solid iron for the FCC, BCC and HCP structures at core conditions in addition to low-temperature and low-pressure calculations relevant to experimental data. 1. Birch, F. Density and composition of mantle and core. Journal of Geophysical Research 69, 4377-4388 (1964). 2. Irving, J. C. E. & Deuss, A. Hemispherical structure in inner core velocity anisotropy. Journal of Geophysical Research 116, B04307 (2011). 3. Buffett, B. A. Onset and orientation of convection in the inner core. Geophysical Journal International 179, 711-719 (2009). 4. Bergman, M. Measurements of electric anisotropy due to solidification texturing and the implications for the Earth's inner core. Nature 389, 60-63 (1997). 5. Deguen, R. & Cardin, P. Thermochemical convection in Earth's inner core. Geophysical Journal International 187, 1101-1118 (2011). 6. Reaman, D. M., Daehn, G. S. & Panero, W. R. Predictive mechanism for anisotropy development in the Earth's inner core. Earth and Planetary Science Letters 312, 437-442 (2011). 7. Ammann, M. W., Brodholt, J. P., Wookey, J. & Dobson, D. P. First-principles constraints on diffusion in lower-mantle minerals and a weak D'' layer. Nature 465, 462-5 (2010).

  5. The Diffusion Process

    NSDL National Science Digital Library

    This is a description for a learning module from Maricopa Advanced Technology Education Center. This PDF describes the module; access may be purchased by visiting the MATEC website. In an orderly and comprehensive set of lectures, lessons, and laboratory activities, MATEC explicates for your learners the complex process of diffusion. Beginning with an overview of diffusion's purpose in altering a wafer's electrical characteristics, the module then drills down to specifics: process parameters, different techniques of diffusion, the use of a hot probe to evaluate diffusion, and wafer handling. Your learners demonstrate their new knowledge by diffusing selected dopants into a silicon wafer.

  6. Diffusion in heterogeneous media

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Liu, L.

    2012-12-01

    Diffusion in heterogeneous media has been investigated for over forty years. However, the fundamental equations for bulk (effective) diffusivity in multi-phase systems were incorrect because of the use of an inappropriate similarity between diffusion and other physical properties such as thermal conductivity. The mistake has permeated through the literature and textbooks. Specifically, the role of concentration partitioning between different phases in diffusion was not considered in such similarity relations. In this work, we present the correct method to derive such relations in heterogeneous media. Barrer [1] used the similarity between diffusivity and thermal conductivity to derive the relation between the bulk (effective) diffusivity and the individual-phase diffusivities. The approach was followed by many others [2-4]. Unfortunately the similarity approach by Barrer [1] is incorrect because there is also dissimilarity. The key difference is that, even though heat conduction and mass diffusion are characterized by a similar flux equation, in heat conduction, T is continuous across phase boundaries, whereas in diffusion, C is usually not continuous across phase boundaries. The concentration in each phase plays a major role in controlling the contribution by the phase to the bulk diffusive flux and hence the bulk diffusivity. For example, if the concentration of a component in a phase is very low, even if the diffusivity in the phase is high, the contribution of diffusion in that phase to the bulk diffusion flux can still be negligible. Hence, previous models for diffusivity in composite materials or multi-mineral rocks, no matter how sophisticated, are fundamentally wrong because the foundation is a mistake. Correcting the mistake is straightforward. The mass flux can be written in terms of chemical potential and mobility [5,6]. Because chemical potential is continuous across phase boundaries, the relation between bulk mobility and individual-phase mobilities is the same as that between bulk heat conductivity and individual-phase heat conductivities. That is, all previous relations for diffusion cannot be directly applied to diffusivities, but can be applied to mobilities. Then, from the relation between diffusivity and mobility, the correct equations can be obtained, as will be shown in the presentation. [1] Barrer (1968) Diffusion in Polymers, Academic Press, 165. [2] Crank (1975) The Mathematics of Diffusion, Clarendon Press. [3] Brady (1983) Am. J. Sci. 283A, 181. [4] Torquato et al. (1999) J. Appl. Phys. 85, 1560. [5] Lesher (1994) J Geophys. Res. 99, 9585. [6] Zhang (1993) J Geophys. Res. 98, 11901.

  7. Titanium diffusion in olivine

    NASA Astrophysics Data System (ADS)

    Cherniak, Daniele J.; Liang, Yan

    2014-12-01

    Diffusion of Ti has been characterized in natural olivine and synthetic forsterite. Experiments on the natural olivines were run under buffered conditions (IW and NNO), and those on synthetic forsterite were run in air. Titanium diffusion appears relatively insensitive to crystallographic orientation and oxygen fugacity under the range of investigated conditions, and diffusivities are similar for Fe-bearing olivine and forsterite. For Ti diffusion in synthetic forsterite, we obtain the following Arrhenius relation for diffusion over the temperature range 900-1400 °C:

  8. Protein crystal growth in space

    NASA Technical Reports Server (NTRS)

    Bugg, C. E.; Clifford, D. W.

    1987-01-01

    The advantages of protein crystallization in space, and the applications of protein crystallography to drug design, protein engineering, and the design of synthetic vaccines are examined. The steps involved in using protein crystallography to determine the three-dimensional structure of a protein are discussed. The growth chamber design and the hand-held apparatus developed for protein crystal growth by vapor diffusion techniques (hanging-drop method) are described; the experimental data from the four Shuttle missions are utilized to develop hardware for protein crystal growth in space and to evaluate the effects of gravity on protein crystal growth.

  9. Theoretical examination of the effect of hydrogen on self-diffusion in iron

    Microsoft Academic Search

    A. M. Dobrotvorskii; Yu. I. Archakov

    1991-01-01

    Kinetic processes associated with the formation and breakdown of phases, grain growth, and segregation of impurities are caused by self-diffusion or diffusion of impurity atoms in solids. These processes change the strength of materials. Diffusion controls failure kinetics of metals under the long-term effect of low loads and higher temperatures with the main fraction in the life of the metal

  10. Michelson-Morley with a Birefringent Cavity

    NASA Astrophysics Data System (ADS)

    Monsalve, Francisco J.; Hohensee, Michael; Müller, Holger

    2012-06-01

    We report on the progress of a birefringent cavity test of the isotropy of the speed of light. Previous experimental tests have constrained anisotropies in the speed of light at the level of parts in 10^17 [1-2]. These experiments search for frame-dependent variations in the resonant frequencies of two orthogonally mounted optical cavities. Uncorrelated fluctuations in the cavity lengths are a significant challenge for such experiments. Our experiment uses a single dielectric-filled cavity, and measures the difference in the resonant frequency of two orthogonally polarized modes. Anisotropies in the speed of light will manifest as a frame-dependent strain on the dielectric [3-4], giving rise to a frame-dependent variation in the cavity birefringence. By making the length of each cavity mode identical, we expect that our experiment will be less sensitive to thermal cavity fluctuations. [4pt] [1] S. Herrmann, A. Senger, K. M"ohle, M. Nagel, E.V. Kovalchuk and A. Peters, PRD 80, 105011 (2009).[2] Ch. Eisel, A. Yu. Nevsky, and S. Schiller, PRL 103, 090401 (2009).[3] H. M"uller, PRD 71, 045004 (2005).[4] V.A. Kosteleck'y and M. Mewes, PRD 80, 015020 (2009).

  11. Polyhedral Superconducting Cavities for Linac Colliders

    NASA Astrophysics Data System (ADS)

    Pogue, Nathaniel; McIntyre, Peter; Sattarov, Dior

    2007-10-01

    The next priority for research facilities in high-energy physics is an electron-positron linac collider. The technological heart of the project is a ˜20 km string of superconducting cavities that must accelerate the two beams to a collision energy of about 1 TeV. The success of the project will depend upon efforts to push the performance and reduce the cost for manufacturing the cavities. A novel approach to cavity design is being developed at Texas A&M, in which the cavities are constructed as a polyhedron. The critical inner surface is accessible through the whole fabrication process. This approach has several interesting benefits: it makes it possible to kill deflecting modes that could limit luminosity, it makes possible a simpler means to refrigerate the cavities, and eliminates the `breathing' of cavities from the Lorentz pressure when they are energized. The open geometry allows for the use of advanced superconducting materials to push performance. The cavity design will be presented, and work to develop and test models will be described.

  12. Forward Modeling of a Coronal Cavity

    NASA Technical Reports Server (NTRS)

    Kucera, T. A.; Gibson, S. E.; Schmit, D. J.

    2011-01-01

    We apply a forward model of emission from a coronal cavity in an effort to determine the temperature and density distribution in the cavity. Coronal cavities are long, low-density structures located over filament neutral lines and are often seen as dark elliptical features at the solar limb in white light, EUV and X-rays. When these structures erupt they form the cavity portions of CMEs The model consists of a coronal streamer model with a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. Temperature and density can be varied as a function of altitude both in the cavity and streamer. We apply this model to a cavity observed in Aug. 2007 by a wide array of instruments including Hinode/EIS, STEREO/EUVI and SOHO/EIT. Studies such as these will ultimately help us understand the the original structures which erupt to become CMEs and ICMES, one of the prime Solar Orbiter objectives.

  13. Video System For Inspecting Walls Of Cavities

    NASA Technical Reports Server (NTRS)

    Gilbert, John A.; Matthys, Donald R.

    1996-01-01

    Endoscopic video-imaging system generates panoramic image of part of wall of cavity surrounding tip of probe inserted in cavity. Not necessary to rotate probe to obtain panoramic image. If simple inspection without measurement required, device called "cylindrical light ring" mounted on probe to illuminate scene. Different illumination device used when required to measure distance of wall of cavity from cylindrical axis of probe. System used, for example, to inspect inner surface of tube, passage, or manifold located deep within engine or other complex structure.

  14. Heat transfer in shrouded rectangular cavities

    NASA Technical Reports Server (NTRS)

    Chyu, M. K.; Metzger, D. E.; Hwan, C. L.

    1986-01-01

    Heat transfer with turbulent flow over shrouded rectangular cavities are numerically investigated. The geometry studied models flow through the clearance gap at the grooved tip of an axial turbine blade, where the blade rotates in close proximity to a stationary outer ring or shroud. The direction of relative shroud motion is always in opposition to the direction of the gas flow across the blade tip. Heat transfer characteristics and flow pattern in a cavity are found to be strongly influenced by the dimension of gap clearance, cavity geometry, and relative shroud movement.

  15. An axisymmetric method for analyzing cavity arrays

    SciTech Connect

    Fischer, F.J.

    1984-01-01

    Single, isolated cavities or small clusters of cavities far removed from the periphery of their host salt dome can usually be satisfactorily analyzed with two-dimensional methods. In some instances, three-dimensional effects of a cavity array and, perhaps, the sedimentary layers surrounding the host salt dome are important. In an attempt to capture essential three-dimensional effects within the constraints of a two-dimensional analysis capability, the concept of ''axisymmetric rings'' is introduced. This paper discusses the approach of axisymmetric rings and presents an example of its application, i.e., the analysis of the LOOP storage facility in the Clovelly salt dome.

  16. Atom-mirror entanglement via cavity dissipation

    NASA Astrophysics Data System (ADS)

    Li, Lingchao; Hu, Xiangming; Rao, Shi; Xu, Jun

    2015-05-01

    We present a cavity dissipation scheme to prepare a hybrid system of an atomic ensemble and a moving mirror in squeezed and entangled states. This scheme is based on four-wave mixing in the atoms and radiation pressure on the mirror, both of which combine to lead to Bogoliubov interactions of the atoms and the mirror with the cavity fields. Under adiabatic conditions, the cavity fields cause the hybrid Bogoliubov modes to evolve into the vacuum states, which correspond to the two-mode squeezed and entangled states. The dependence of the hybrid entanglement on the system parameters is also presented in and beyond the Bogoliubov interactions.

  17. Temperature dependence of cavity ionization chamber response

    NASA Astrophysics Data System (ADS)

    Yi, Chul-Young; Kim, Hyun-Moon

    2013-04-01

    The temperature dependence of the cavity ion chamber response was measured at room temperature in the range 17 °C to 27 °C. By analysing the variation of the ionization current with temperature produced in the cavity chamber, the temperature coefficient of the cavity chamber response was evaluated. The values were 4.1 × 10-4 °C-1, 4.3 × 10-4 °C-1 and 2 × 10-5 °C-1 for chambers made of C552 air equivalent plastic, polyoxymethylene and graphite, respectively.

  18. Materials Analysis of CED Nb Films Being Coated on Bulk Nb Single Cell SRF Cavities

    SciTech Connect

    Zhao, Xin; Reece, Charles; Palczewski, Ari; Ciovati, Gianluigi; Krishnan, Mahadevan; James, Colt; Irfan, Irfan

    2013-09-01

    This study is an on-going research on depositing a Nb film on the internal wall of bulk Nb single cell SRF cavities, via a cathodic arc Nb plasma ions source, an coaxial energetic condensation (CED) facility at AASC company. The motivation is to firstly create a homoepitaxy-like Nb/Nb film in a scale of a ~1.5GHz RF single cell cavity. Next, through SRF measurement and materials analysis, it might reveal the baseline properties of the CED-type homoepitaxy Nb films. Literally, a top-surface layer of Nb films which sustains SRF function, always grows up in homo-epitaxy mode, on top of a Nb nucleation layer. Homo-epitaxy growth of Nb must be the final stage (a crystal thickening process) of any coatings of Nb film on alternative cavity structure materials. Such knowledge of Nb-Nb homo-epitaxy is useful to create future realistic SRF cavity film coatings, such as hetero-epitaxy Nb/Cu Films, or template-layer-mitigated Nb films. One large-grain, and three fine grain bulk Nb cavities were coated. They went through cryogenic RF measurement. Preliminary results show that the Q0 of a Nb film could be as same as the pre-coated bulk Nb surface (which received a chemically-buffered polishing plus a light electro-polishing); but quality factor of two tested cavities dropped quickly. We are investigating if the severe Q-slope is caused by hydrogen incorporation before deposition, or is determined by some structural defects during Nb film growth.

  19. The growth of fission gas bubbles in irradiated uranium dioxide

    Microsoft Academic Search

    R. M. Cornell

    1969-01-01

    The growth of fission gas bubbles from supersaturated solution in irradiated uranium dioxide has been studied by electron microscopy under isothermal annealing conditions between 1300° and 1500°C. Measurements of the kinetics of bubble growth have enabled the diffusion coefficients of atomic xenon and krypton in irradiated uranium dioxide to be determined. The diffusion coefficients obtained may be expressed by the

  20. Dominant diffusing species during cobalt silicide formation

    NASA Astrophysics Data System (ADS)

    Comrie, C. M.; Newman, R. T.

    1996-01-01

    The dominant moving species during cobalt monosilicide and cobalt disilicide formation has been examined using a thin tantalum layer as a metal marker. The marker data obtained following the formation of CoSi from Co2Si showed that monosilicide growth was essentially due Si diffusion only. When used to study CoSi2 formation, the data indicated that silicon was also the dominant moving species during disilicide formation, although a noninsignificant amount of cobalt diffusion was also observed to take place.