Science.gov

Sample records for diffusive cavity growth

  1. Models for coupled diffusive/strain controlled growth of creep cavities

    SciTech Connect

    Lu, H.M.; Delph, T.J. )

    1993-08-01

    The importance of intergranular creep cavitation to high-temperature failure processes in metals and ceramics has been well-recognized for some time now. In general, creep cavity growth at elevated temperature is thought to occur by one of two processes. The first of these is diffusive growth, whereby matter is transported from the cavity surface and is deposited on the grain boundary. The second is strain-controlled growth, in which the cavity grows entirely as a consequence of creep deformation of the surrounding material under the action of an applied stress. Several models of cavity growth have been proposed in which these processes are coupled to each other and occur simultaneously. These models have attained some currency and have been used in several studies involving the growth of creep cavitation. The purpose of the present note is to investigate in some detail one particular class of these models.

  2. Cavity growth in soft adhesives

    NASA Astrophysics Data System (ADS)

    Chiche, A.; Dollhofer, J.; Creton, C.

    2005-08-01

    The growth process of cavities nucleated at the interface between a rigid surface and a soft adhesive layer has been investigated with a probe method. A tensile stress was applied to the highly confined layer resulting in a negative hydrostatic pressure in the layer. The statistics of appearance and rate of growth of cavities as a function of applied negative stress were monitored with a CCD camera. If large germs of cavities were initially present, most of the cavities became optically visible above a critical level of stress independent of layer thickness. Cavities grew simultaneously and at the same expansion rate as a function of applied stress. In the absence of large germs, cavities became optically visible one after another, reaching a limiting size controlled by the thickness of the layer independently and very rapidly. Although, for each sample, we observed a statistical distribution of critical stress levels where a cavity expanded, the mean cavitation stress depended both on surface topography and more surprisingly on layer thickness. We believe that this new and somewhat surprising result can be interpreted with a model for the growth of small germs in finite size layers (J. Dollhofer, A. Chiche, V. Muralidharan et al., Int. J. Solids Struct. 41, 6111 (2004)). This model is mainly based on the dual notion of an energy activated transition from an unexpanded metastable state to an expanded stable state and to the proportionality of the activation energy with the elastic energy stored in the adhesive layer.

  3. Superhydrophobicity: cavity growth and wetting transition.

    PubMed

    Wåhlander, Martin; Hansson-Mille, Petra M; Swerin, Agne

    2015-06-15

    We show by using AFM colloidal probe microscopy (combinations of hydrophobic/superhydrophobic as probe/surface) that superhydrophobicity displays a set of specific events when compared with hydrophobicity. Both attraction (due to capillary and wetting forces) and repulsion (most likely due to repelling air/vapor layers or micro-/nanobubbles) occur upon approach and when surfaces are pulled apart both shorter range (50-100 nm or more) and longer range (several micrometers) attractive forces are displayed. The interaction is explained by forces generated through the formation of air and water vapor cavities, in the shorter-range (>50 nm) case maintaining a constant volume of the cavity, in agreement with calculation of capillary forces, and in the longer-range (>1 ?m) case through access of air to the cavity, in agreement with thermodynamics of cavity growth. An added sodium dodecyl sulphate surfactant gave a partially reversible wetting transition and reduced the longer-range interaction to shorter-range, suggesting a transfer from the Cassie-Baxter to the Wenzel wetting regime. The findings would be of interest in development of practical applications, such as for anti-soiling, anti-icing, protection of electrical components and for extreme water-repellency in paper and textiles. PMID:25771290

  4. 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.

  5. Diffuse glioma growth: a guerilla war

    PubMed Central

    Idema, Albert J.; Wesseling, Pieter

    2007-01-01

    In contrast to almost all other brain tumors, diffuse gliomas infiltrate extensively in the neuropil. This growth pattern is a major factor in therapeutic failure. Diffuse infiltrative glioma cells show some similarities with guerilla warriors. Histopathologically, the tumor cells tend to invade individually or in small groups in between the dense network of neuronal and glial cell processes. Meanwhile, in large areas of diffuse gliomas the tumor cells abuse pre-existent “supply lines” for oxygen and nutrients rather than constructing their own. Radiological visualization of the invasive front of diffuse gliomas is difficult. Although the knowledge about migration of (tumor)cells is rapidly increasing, the exact molecular mechanisms underlying infiltration of glioma cells in the neuropil have not yet been elucidated. As the efficacy of conventional methods to fight diffuse infiltrative glioma cells is limited, a more targeted (“search & destroy”) tactic may be needed for these tumors. Hopefully, the study of original human glioma tissue and of genotypically and phenotypically relevant glioma models will soon provide information about the Achilles heel of diffuse infiltrative glioma cells that can be used for more effective therapeutic strategies. PMID:17805551

  6. Volume Diffusion Growth Kinetics and Step Geometry in Crystal Growth

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Ramachandran, Narayanan

    1998-01-01

    The role of step geometry in two-dimensional stationary volume diff4sion process used in crystal growth kinetics models is investigated. Three different interface shapes: a) a planar interface, b) an equidistant hemispherical bumps train tAx interface, and c) a train of right angled steps, are used in this comparative study. The ratio of the super-saturation to the diffusive flux at the step position is used as a control parameter. The value of this parameter can vary as much as 50% for different geometries. An approximate analytical formula is derived for the right angled steps geometry. In addition to the kinetic models, this formula can be utilized in macrostep growth models. Finally, numerical modeling of the diffusive and convective transport for equidistant steps is conducted. In particular, the role of fluid flow resulting from the advancement of steps and its contribution to the transport of species to the steps is investigated.

  7. Enhancement in Quality Factor of SRF Niobium Cavities by Material Diffusion

    SciTech Connect

    Dhakal, Pashupati; Ciovati, Gianluigi; Kneisel, Peter K.; Myneni, Ganapati Rao

    2015-06-01

    An increase in the quality factor of superconducting radiofrequency cavities is achieved by minimizing the surface resistance during processing steps. The surface resistance is the sum of temperature independent residual resistance and temperature/material dependent Bardeen-Cooper-Schrieffer (BCS) resistance. High temperature heat treatment usually reduces the impurities concentration from the bulk niobium, lowering the residual resistance. The BCS part can be reduced by selectively doping non-magnetic impurities. The increase in quality factor, termed as Q-rise, was observed in cavities when titanium or nitrogen thermally diffused in the inner cavity surface.

  8. Enhancement in Quality Factor of SRF Niobium Cavities by Material Diffusion

    E-print Network

    Dhakal, Pashupati; Kneisel, Peter; Myneni, Ganapati Rao

    2014-01-01

    An increase in the quality factor of superconducting radiofrequency cavities is achieved by minimizing the surface resistance during processing steps. The surface resistance is the sum of temperature independent residual resistance and temperature/material dependent Bardeen-Cooper-Schrieffer (BCS) resistance. High temperature heat treatment usually reduces the impurities concentration from the bulk niobium, lowering the residual resistance. The BCS part can be reduced by selectively doping non-magnetic impurities. The increase in quality factor, termed as Q-rise, was observed in cavities when titanium or nitrogen thermally diffused in the inner cavity surface.

  9. A simplified model for thermal-wave cavity self-consistent measurement of thermal diffusivity

    SciTech Connect

    Shen, Jun Zhou, Jianqin; Gu, Caikang; Neill, Stuart; Michaelian, Kirk H.; Fairbridge, Craig; Astrath, Nelson G. C.; Baesso, Mauro L.

    2013-12-15

    A simplified theoretical model was developed for the thermal-wave cavity (TWC) technique in this study. This model takes thermal radiation into account and can be employed for absolute measurements of the thermal diffusivity of gas and liquid samples without any knowledge of geometrical and thermal parameters of the components of the TWC. Using this model and cavity-length scans, thermal diffusivities of air and distilled water were accurately and precisely measured as (2.191 ± 0.004) × 10{sup ?5} and (1.427 ± 0.009) × 10{sup ?7} m{sup 2}?s{sup ?1}, respectively, in very good agreement with accepted literature values.

  10. Comparisons of hybrid radiosity-diffusion model and diffusion equation for bioluminescence tomography in cavity cancer detection

    NASA Astrophysics Data System (ADS)

    Chen, Xueli; Yang, Defu; Qu, Xiaochao; Hu, Hao; Liang, Jimin; Gao, Xinbo; Tian, Jie

    2012-06-01

    Bioluminescence tomography (BLT) has been successfully applied to the detection and therapeutic evaluation of solid cancers. However, the existing BLT reconstruction algorithms are not accurate enough for cavity cancer detection because of neglecting the void problem. Motivated by the ability of the hybrid radiosity-diffusion model (HRDM) in describing the light propagation in cavity organs, an HRDM-based BLT reconstruction algorithm was provided for the specific problem of cavity cancer detection. HRDM has been applied to optical tomography but is limited to simple and regular geometries because of the complexity in coupling the boundary between the scattering and void region. In the provided algorithm, HRDM was first applied to three-dimensional complicated and irregular geometries and then employed as the forward light transport model to describe the bioluminescent light propagation in tissues. Combining HRDM with the sparse reconstruction strategy, the cavity cancer cells labeled with bioluminescent probes can be more accurately reconstructed. Compared with the diffusion equation based reconstruction algorithm, the essentiality and superiority of the HRDM-based algorithm were demonstrated with simulation, phantom and animal studies. An in vivo gastric cancer-bearing nude mouse experiment was conducted, whose results revealed the ability and feasibility of the HRDM-based algorithm in the biomedical application of gastric cancer detection.

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

    E-print Network

    Manga, Michael

    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

  12. Commissioning results of Nb3Sn cavity vapor diffusion deposition system at Jlab

    SciTech Connect

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

    2015-09-01

    Nb3Sn as a BCS superconductor with a superconducting critical temperature higher than that of niobium offers potential benefit for SRF cavities via a lower-than-niobium surface resistance at the same temperature and frequency. A Nb3Sn vapor diffusion deposition system designed for coating of 1.5 and 1.3 GHz single-cell cavities was built and commissioned at JLab. As the part of the commissioning, RF performance at 2.0 K of a single-cell 1.5 GHz CEBAF-shaped cavity was measured before and after coating in the system. Before Nb3Sn coating the cavity had a Q0 of about 10E10 and was limited by the high field Q-slope at Eacc about 27 MV/m. Coated cavity exhibited the superconducting transition at about 17.9 K. The low-field quality factor was about 5 10E9 at 4.3 K and 7 10E9 at 2.0 K decreasing with field to about 1 10E9 at Eacc about 8 MV/m at both temperatures. The highest field was limited by the available RF power.

  13. Germanium nanowire growth controlled by surface diffusion effects

    SciTech Connect

    Schmidtbauer, Jan; Bansen, Roman; Heimburger, Robert; Teubner, Thomas; Boeck, Torsten; Fornari, Roberto

    2012-07-23

    Germanium nanowires (NWs) were grown onto Ge(111) substrates by the vapor-liquid-solid process using gold droplets. The growth was carried out in a molecular beam epitaxy chamber at substrate temperatures between 370 Degree-Sign C and 510 Degree-Sign C. The resulting nanowire growth rate turns out to be highly dependent on the substrate temperature exhibiting the maximum at T = 430 Degree-Sign C. The temperature dependence of growth rate can be attributed to surface diffusion both along the substrate and nanowire sidewalls. Analyzing the diffusive material transport yields a diffusion length of 126 nm at a substrate temperature of 430 Degree-Sign C.

  14. Growth with surface diffusion in d = 1 + 1

    NASA Astrophysics Data System (ADS)

    Hontinfinde, Felix; Krug, Joachim; Touzani, M'hamed

    1997-02-01

    A restricted solid-on-solid model where surface relaxation occurs by atom desorption and by surface diffusion is introduced and studied in 1+1 dimensions. The interface profile is mapped onto a four-vertex model and the kinetic equation describing the moving surface is solved exactly for small samples. In the presence of desorption we classify different growth regimes using the Wilson-Frenkel law. In the presence of surface diffusion with step edge barriers we find evidence for a sharp transition from stable to unstable growth which occurs with increasing diffusion length. Growth modes during the thermal evaporation of the crystal are also discussed.

  15. Method for accurate growth of vertical-cavity surface-emitting lasers

    DOEpatents

    Chalmers, Scott A. (Albuquerque, NM); Killeen, Kevin P. (Albuquerque, NM); Lear, Kevin L. (Albuquerque, NM)

    1995-01-01

    We report a method for accurate growth of vertical-cavity surface-emitting lasers (VCSELs). The method uses a single reflectivity spectrum measurement to determine the structure of the partially completed VCSEL at a critical point of growth. This information, along with the extracted growth rates, allows imprecisions in growth parameters to be compensated for during growth of the remaining structure, which can then be completed with very accurate critical dimensions. Using this method, we can now routinely grow lasing VCSELs with Fabry-Perot cavity resonance wavelengths controlled to within 0.5%.

  16. Method for accurate growth of vertical-cavity surface-emitting lasers

    SciTech Connect

    Chalmers, S.A.; Killeen, K.P. )

    1993-03-15

    We report a method for accurate growth of vertical-cavity surface-emitting lasers (VCSELs). The method uses a single reflectivity spectrum measurement to determine the structure of the partially completed VCSEL at a critical point of growth. This information, along with the extracted growth rates, allows imprecisions in growth parameters to be compensated for during growth of the remaining structure, which can then be completed with very accurate critical dimensions. Using this method, we can now routinely grow lasing VCSELs with Fabry--Perot cavity resonance wavelengths controlled to within 0.5%.

  17. Method for accurate growth of vertical-cavity surface-emitting lasers

    DOEpatents

    Chalmers, S.A.; Killeen, K.P.; Lear, K.L.

    1995-03-14

    The authors report a method for accurate growth of vertical-cavity surface-emitting lasers (VCSELs). The method uses a single reflectivity spectrum measurement to determine the structure of the partially completed VCSEL at a critical point of growth. This information, along with the extracted growth rates, allows imprecisions in growth parameters to be compensated for during growth of the remaining structure, which can then be completed with very accurate critical dimensions. Using this method, they can now routinely grow lasing VCSELs with Fabry-Perot cavity resonance wavelengths controlled to within 0.5%. 4 figs.

  18. 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. ...

  19. Freezing a Coherent Field Growth in a Cavity by Quantum Zeno Effect

    E-print Network

    Julien Bernu; Samuel Deléglise; Clément Sayrin; Stefan Kuhr; Igor Dotsenko; Michel Brune; Jean-Michel Raimond; Serge Haroche

    2008-09-25

    We have frozen the coherent evolution of a field in a cavity by repeated measurements of its photon number. We use circular Rydberg atoms dispersively coupled to the cavity mode for an absorption-free photon counting. These measurements inhibit the growth of a Field injected in the cavity by a classical source. This manifestation of the Quantum Zeno effect illustrates the back action of the photon number determination onto the Field phase. The residual growth of the Field can be seen as a random walk of its amplitude in the two-dimensional phase space. This experiment sheds light onto the measurement process and opens perspectives for active quantum feedback.

  20. Freezing Coherent Field Growth in a Cavity by the Quantum Zeno Effect

    NASA Astrophysics Data System (ADS)

    Bernu, J.; Deléglise, S.; Sayrin, C.; Kuhr, S.; Dotsenko, I.; Brune, M.; Raimond, J. M.; Haroche, S.

    2008-10-01

    We have frozen the coherent evolution of a field in a cavity by repeated measurements of its photon number. We use circular Rydberg atoms dispersively coupled to the cavity mode for an absorption-free photon counting. These measurements inhibit the growth of a field injected in the cavity by a classical source. This manifestation of the quantum Zeno effect illustrates the backaction of the photon number determination onto the field phase. The residual growth of the field can be seen as a random walk of its amplitude in the two-dimensional phase space. This experiment sheds light onto the measurement process and opens perspectives for active quantum feedback.

  1. 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.

  2. Analogies between optical propagation and heat diffusion: Applications to micro-cavities, gratings and cloaks

    E-print Network

    Amra, Claude; Zerrad, Myriam; Guenneau, Sébastien; Soriano, Gabriel; Gralak, Boris; Bellieud, Michel; Veynante, Denis; Rolland, Nathalie

    2015-01-01

    A new analogy between optical propagation and heat diffusion in heterogeneous anisotropic media has been proposed recently [S. Guenneau, C. Amra, and D. Veynante, Optics Express Vol. 20, 8207-8218 (2012)]. A detailed derivation of this unconventional correspondence is presented and developed. In time harmonic regime, all thermal parameters are related to optical ones in artificial metallic media, thus making possible to use numerical codes developed for optics. Then the optical admittance formalism is extended to heat conduction in multilayered structures. The concepts of planar micro-cavities, diffraction gratings, and planar transformation optics for heat conduction are addressed. Results and limitations of the analogy are emphasized.

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

    NASA Astrophysics Data System (ADS)

    Balderas-López, J. A.; Mandelis, A.; Garcia, J. A.

    2000-07-01

    A liquid-ambient-compatible thermal wave resonant cavity (TWRC) has been constructed for the measurement of the thermal diffusivity of liquids. The thermal diffusivities of distilled water, glycerol, ethylene glycol, and olive oil were determined at room temperature (25 °C), with four-significant-figure precision as follows: (0.1445±0.0002)×10-2 cm2/s (distilled water); (0.0922±0.0002)×10-2 cm2/s (glycerol); (0.0918±0.0002)×10-2 cm2/s (ethylene glycol); and (0.0881±0.0004)×10-2 cm2/s (olive oil). The liquid-state TWRC sensor was found to be highly sensitive to various mixtures of methanol and salt in distilled water with sensitivity limits 0.5% (v/v) and 0.03% (w/v), respectively. The use of the TWRC to measure gas evolution from liquids and its potential for environmental applications has also been demonstrated.

  4. A new scheme of compact cold atom clock based on diffuse laser cooling in a cylindrical cavity

    E-print Network

    Liu, Peng; Wan, Jinyin; Wang, Xiumei; Wang, Yaning; Xiao, Ling; Cheng, Huadong; Liu, Liang

    2015-01-01

    We present a new scheme of compact Rubidium cold-atom clock which performs the diffuse light cooling, the microwave interrogation and the detection of the clock signal in a cylindrical microwave cavity. The diffuse light is produced by the reflection of the laser light at the inner surface of the microwave cavity. The pattern of injected laser beams is specially designed to make most of the cold atoms accumulate in the center of the microwave cavity. The microwave interrogation of cold atoms in the cavity leads to Ramsey fringes whose line-width is 24.5 Hz and the contrast of 95.6% when the free evolution time is 20 ms. The frequency stability of $7.3\\times10^{-13}\\tau^{-1/2}$ has been achieved recently. The scheme of this physical package can largely reduce the complexity of the cold atom clock, and increase the performance of the clock.

  5. Nucleation and growth of precipitates in transformations driven by diffusion

    SciTech Connect

    Clavaguera, N.; Clavaguera-Mora, M.T.

    1998-12-31

    A theoretical analysis of the transformation kinetics which accounts for nuclei, either prequenched or created homogeneously, and whose growth are controlled by diffusion is presented. The change in growth habit intervening during the transformation is analyzed in terms of the evolution of the free energy difference between the precipitate and the matrix at the interface, {Delta}G{sup 1}. In the Avrami formalism, this quantity accounts for the competition between interface and diffusion controlled growth whereas the nucleation events are driven by the free energy difference between the precipitate and the bulk matrix. Competition and selection of precipitate phases in highly undercooled melts using the CALPHAD approach for the evaluation of the free energies and the changes in diffusivity with concentration are analyzed. Experimental vs. calculated data are discussed in some rapidly solidified metallic systems.

  6. 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.

  7. [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

  8. Diffusion-controlled growth and degree of disequilibrium of garnet porphyroblasts: is diffusion-controlled growth of porphyroblasts common?

    NASA Astrophysics Data System (ADS)

    Miyazaki, Kazuhiro

    2015-12-01

    Rate-limiting processes and the degree of disequilibrium during metamorphic mineral growth are key controls on the rate of dehydration and hydration in the Earth's crust. This paper examines diffusion-controlled growth and the degree of disequilibrium of garnet porphyroblasts in the Tsukuba metamorphic rocks of central Japan. The analyzed porphyroblasts have irregular and branching morphologies with clear diffusional haloes, indicating that they grew in a diffusion-controlled regime. Mathematical analysis shows that the dominant wavelength of the interface of a garnet porphyroblast is dependent on the extent of supersaturation (? ?), which is an index for the degree of disequilibrium. Using the calculated upper and lower limits of the dominant wavelength, the value of ? ? is estimated to be 0.05 × 10-1-0.16, which corresponds to a Gibbs free energy (? G r ) overstep of 0.9-27 kJ per mole of garnet (12 oxygen atoms) and a temperature overstep (? T) of 1.7-50 °C. Using the average value of the dominant wavelength, the following results are obtained: ? ? = 0.15 × 10-1, ? G r = 2.7 kJ per mole of garnet, and ? T = 5 °C. These values bring into question the importance of diffusion-controlled growth of garnet porphyroblasts, as highly irregular and branching garnet porphyroblasts are rare in most metamorphic belts. After significant overstepping for the nucleation of garnet, the garnet porphyroblasts grow at a high degree of disequilibrium. However, a high degree of disequilibrium under diffusion-controlled growth would be characterized by diffusional instability. The results indicate that garnet porphyroblasts that lack an irregular and branching morphology may grow at a high degree of disequilibrium under interface-controlled growth, provided they are set in a medium where the diffusion and supply of constituent elements are sufficient, such as a sufficient volume of metamorphic fluid.

  9. Shape Selection in Diffusive Growth of Colloids and Nanoparticles

    E-print Network

    Vyacheslav Gorshkov; Alexandr Zavalov; Vladimir Privman

    2009-05-23

    We report numerical investigations of a three-dimensional model of diffusive growth of fine particles, the internal structure of which corresponds to different crystal lattices. A growing cluster (particle) is immersed in, and exchanges monomer building blocks with a surrounding medium of diffusing (off-lattice) monomers. On-surface dynamics of the latter is accounted for by allowing, in addition to detachment, monomer motion to the neighboring vacant crystal sites, according to probabilistic rules mimicking local thermalization. The key new feature of our model is the focus on the growth of a single cluster, emerging as a crystalline core, without development of defects that can control large-scale growth modes. This single, defect-free core growth is imposed by the specific dynamical rules assumed. Our results offer a possible explanation of the experimentally observed shape uniformity, i.e., fixed, approximately even-sized proportions, in synthesis of uniform colloids and nanoparticles. We demonstrate the basic principles of well-defined particle shape emergence in such growth. Specifically, several shapes are possible for a given crystal structure. Formation of shapes that follow the crystal symmetry and are uniform, can be a result of the nonequilibrium nature of the growth process. The shape of a growing particle can be controlled by varying the relative rates of kinetic processes, as well as by adjusting the concentration of monomers in the surrounding medium.

  10. Growth of Silicon Nanosheets Under Diffusion-Limited Aggregation Environments.

    PubMed

    Lee, Jaejun; Kim, Sung Wook; Kim, Ilsoo; Seo, Dongjea; Choi, Heon-Jin

    2015-12-01

    The two-dimensional (2D) growth of cubic-structured (silicon) Si nanosheets (SiNSs) was investigated. Freestanding, single-crystalline SiNSs with a thickness of 5-20 nm were grown on various Si substrates under an atmospheric chemical vapor deposition process. Systematic investigation indicated that a diffusion-limited aggregation (DLA) environment that leads to dendritic growth in <110> directions at the initial stage is essential for 2D growth. The kinetic aspects under DLA environments that ascribe to the dendritic and 2D growth were discussed. Under the more dilute conditions made by addition of Ar to the flow of H2, the SiNSs grew epitaxially on the substrates with periodic arrangement at a specific angle depending on the orientation of the substrate. It reveals that SiNSs always grew two dimensionally with exposing (111) surfaces. That is thermodynamically favorable. PMID:26518028

  11. Growth of Silicon Nanosheets Under Diffusion-Limited Aggregation Environments

    NASA Astrophysics Data System (ADS)

    Lee, Jaejun; Kim, Sung Wook; Kim, Ilsoo; Seo, Dongjea; Choi, Heon-Jin

    2015-10-01

    The two-dimensional (2D) growth of cubic-structured (silicon) Si nanosheets (SiNSs) was investigated. Freestanding, single-crystalline SiNSs with a thickness of 5-20 nm were grown on various Si substrates under an atmospheric chemical vapor deposition process. Systematic investigation indicated that a diffusion-limited aggregation (DLA) environment that leads to dendritic growth in <110> directions at the initial stage is essential for 2D growth. The kinetic aspects under DLA environments that ascribe to the dendritic and 2D growth were discussed. Under the more dilute conditions made by addition of Ar to the flow of H2, the SiNSs grew epitaxially on the substrates with periodic arrangement at a specific angle depending on the orientation of the substrate. It reveals that SiNSs always grew two dimensionally with exposing (111) surfaces. That is thermodynamically favorable.

  12. Structure of S-shaped growth in innovation diffusion

    NASA Astrophysics Data System (ADS)

    Shimogawa, Shinsuke; Shinno, Miyuki; Saito, Hiroshi

    2012-05-01

    A basic question on innovation diffusion is why the growth curve of the adopter population in a large society is often S shaped. From macroscopic, microscopic, and mesoscopic viewpoints, the growth of the adopter population is observed as the growth curve, individual adoptions, and differences among individual adoptions, respectively. The S shape can be explained if an empirical model of the growth curve can be deduced from models of microscopic and mesoscopic structures. However, even the structure of growth curve has not been revealed yet because long-term extrapolations by proposed models of S-shaped curves are unstable and it has been very difficult to predict the long-term growth and final adopter population. This paper studies the S-shaped growth from the viewpoint of social regularities. Simple methods to analyze power laws enable us to extract the structure of the growth curve directly from the growth data of recent basic telecommunication services. This empirical model of growth curve is singular at the inflection point and a logarithmic function of time after this point, which explains the unstable extrapolations obtained using previously proposed models and the difficulty in predicting the final adopter population. Because the empirical S curve can be expressed in terms of two power laws of the regularity found in social performances of individuals, we propose the hypothesis that the S shape represents the heterogeneity of the adopter population, and the heterogeneity parameter is distributed under the regularity in social performances of individuals. This hypothesis is so powerful as to yield models of microscopic and mesoscopic structures. In the microscopic model, each potential adopter adopts the innovation when the information accumulated by the learning about the innovation exceeds a threshold. The accumulation rate of information is heterogeneous among the adopter population, whereas the threshold is a constant, which is the opposite of previously proposed models. In the mesoscopic model, flows of innovation information incoming to individuals are organized as dimorphic and partially clustered. These microscopic and mesoscopic models yield the empirical model of the S curve and explain the S shape as representing the regularities of information flows generated through a social self-organization. To demonstrate the validity and importance of the hypothesis, the models of three level structures are applied to reveal the mechanism determining and differentiating diffusion speeds. The empirical model of S curves implies that the coefficient of variation of the flow rates determines the diffusion speed for later adopters. Based on this property, a model describing the inside of information flow clusters can be given, which provides a formula interconnecting the diffusion speed, cluster populations, and a network topological parameter of the flow clusters. For two recent basic telecommunication services in Japan, the formula represents the variety of speeds in different areas and enables us to explain speed gaps between urban and rural areas and between the two services. Furthermore, the formula provides a method to estimate the final adopter population.

  13. Growth of vertical-cavity surface emitting lasers by metalorganic vapor phase epitaxy

    SciTech Connect

    Hou, H.Q.; Hammons, B.E.; Crawford, M.H.; Lear, K.L.; Choquette, K.D.

    1996-10-01

    We present growth and characterization of visible and near-infrared vertical-cavity surface emitting lasers (VCSELs) grown by metalorganic vapor phase epitaxy. Discussions on the growth issue of VCSEL materials include growth rate and composition control using an {ital in}{ital situ} normal-incidence reflectometer, comprehensive p- and n-type doping study in AlGaAs by CCl{sub 4} and Si{sub 2}H{sub 6} over the entire composition range, and optimization of ultra-high material uniformity. We also demonstrate our recent achievements of all-AlGaAs VCSELs which include the first room-temperature continuous- wave demonstration of 700-nm red VCSELs and high-efficiency and low- threshold voltage 850-nm VCSELs.

  14. Geometry and Dynamics of Diffusion-Limited Growth

    NASA Astrophysics Data System (ADS)

    Schwarzer, Stefan

    Diffusion-limited aggregation (DLA) is a simple discrete growth model, applicable to literally hundreds of natural phenomena. DLA growth takes place by addition of random walkers to the perimeter of the aggregate. The probability that a perimeter site is hit first by an incident walker is called the site's growth probability. Since these growth probabilities provide an almost complete description of the DLA growth dynamics, they have initiated considerable research activity. However, so far, our theoretical understanding of DLA is limited. In particular, the interplay between the geometrical properties of the pattern's shape and the dependence of the growth probabilities on the size of the cluster is poorly understood. I propose a geometric void-neck model for the structure of two dimensional (2D) DLA which pictures the aggregate as a sequence of voids of increasing sizes separated by narrow necks. The model predicts a breakdown of power -law behavior with system size for the smallest growth probability p_{rm min} of 2D DLA. This prediction is confirmed in a simulation of 2D aggregates. Additionally, I study the growth probability distribution (GPD) and find a functional form for its tail in agreement with the predicted behavior of p_ {rm min}. In 3D, constraints of topological nature inherent in the 2D void-neck model no longer apply. I confirm by simulation that power-law behavior of p_{rm min} and, in addition, of all moments of the GPD is restored. I propose different functional forms for the GPD and the density profile of the growing DLA cluster which are consistent with my simulation data. I analytically explore the consequences of these propositions for very large clusters and find interesting consequences of the interplay between cluster density and GPD. A direct geometrical test of the void-neck model motivates the development of a novel "glove algorithm." I describe sequences of "perimeters" and "accessible perimeters" (gloves) of DLA and related fractals by new scaling laws. I relate the quantities governing these scaling laws to already established properties of the investigated models. Moreover, I define a hierarchy of "lagoons" as regions that are inaccessible to particles of different sizes. A study of the lagoon size distribution supports the void-neck model and the fractal nature of DLA. Finally, I use the "skeleton" algorithm by Havlin and Nossal to determine the number of main branches of DLA, which is an important morphological characteristic of the cluster. In 2D the cluster displays ~ 9 main branches, whereas in 3D and 4D their number is seemingly not limited.

  15. Diffusion-controlled growth rate of stepped interfaces

    NASA Astrophysics Data System (ADS)

    Saidi, P.; Hoyt, J. J.

    2015-07-01

    For many materials, the structure of crystalline surfaces or solid-solid interphase boundaries is characterized by an array of mobile steps separated by immobile terraces. Despite the prevalence of step-terraced interfaces a theoretical description of the growth rate has not been completely solved. In this work the boundary element method (BEM) has been utilized to numerically compute the concentration profile in a fluid phase in contact with an infinite array of equally spaced surface steps and, under the assumption that step motion is controlled by diffusion through the fluid phase, the growth rate is computed. It is also assumed that a boundary layer exists between the growing surface and a point in the liquid where complete convective mixing occurs. The BEM results are presented for varying step spacing, supersaturation, and boundary layer width. BEM calculations were also used to study the phenomenon of step bunching during crystal growth, and it is found that, in the absence of elastic strain energy, a sufficiently large perturbation in the position of a step from its regular spacing will lead to a step bunching instability. Finally, an approximate analytic solution using a matched asymptotic expansion technique is presented for the case of a stagnant liquid or equivalently a solid-solid stepped interface.

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

    E-print Network

    Cone, Michael Thomas

    2014-04-16

    ever produced. The material is a high-purity fumed silica, or quartz powder. We demonstrate the application of this new material to several areas of integrating cavity enhanced spectroscopy, including absorption, Raman, and fluorescence spectroscopy...

  17. 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.

  18. 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.

  19. Influence of island diffusion on submonolayer epitaxial growth P. L. Krapivsky

    E-print Network

    Redner, Sidney

    Influence of island diffusion on submonolayer epitaxial growth P. L. Krapivsky Center for Polymer to irreversible aggregation of islands. We also account for the effective diffusion of islands, which originates from hopping processes of their constituent adatoms, on the kinetics. When the diffusivity of an island

  20. 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.

  1. Crystal growth mechanisms in miarolitic cavities in the Lake George ring complex and vicinity, Colorado

    USGS Publications Warehouse

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

    1999-01-01

    The Crystal Peak area of the Pikes Peak batholith, near Lake George in central Colorado, is world-renowned for its crystals of amazonite (the blue-green variety of microcline) and smoky quartz. Such crystals, collected from individual miarolitic pegmatites, have a remakably small variation in crystal size within each pegmatite, and the shapes of plots of their crystal size distributions (CSDs) are invariably lognormal or close to lognormal in all cases. These observations are explained by a crystal growth mechanism that was governed initially by surface-controlled kinetics, during which crystals tended to grow larger in proportion to their size, thereby establishing lognormal CSDs. Surface-controlled growth was followed by longer periods of supply controlled growth, during which growth rate was predominantly size-independent, consequently preserving the lognormal shapes of the CSDs and the small size variation. The change from surface- to supply controlled growth kinetics may have resulted from an increasing demand for nutrients that exceeded diffusion limitations of the system. The proposed model for crystal growth in this locality appears to be common in the geologic record, and can be used with other information, such as isotopic data, to deduce physico-chemical conditions during crystal formation.

  2. Transverse emittance growth due to rf noise in the high-luminosity LHC crab cavities

    NASA Astrophysics Data System (ADS)

    Baudrenghien, P.; Mastoridis, T.

    2015-10-01

    The high-luminosity LHC (HiLumi LHC) upgrade with planned operation from 2025 onward has a goal of achieving a tenfold increase in the number of recorded collisions thanks to a doubling of the intensity per bunch (2.2e11 protons) and a reduction of ?* to 15 cm. Such an increase would significantly expedite new discoveries and exploration. To avoid detrimental effects from long-range beam-beam interactions, the half crossing angle must be increased to 295 microrad. Without bunch crabbing, this large crossing angle and small transverse beam size would result in a luminosity reduction factor of 0.3 (Piwinski angle). Therefore, crab cavities are an important component of the LHC upgrade, and will contribute strongly to achieving an increase in the number of recorded collisions. The proposed crab cavities are electromagnetic devices with a resonance in the radio frequency (rf) region of the spectrum (400.789 MHz). They cause a kick perpendicular to the direction of motion (transverse kick) to restore an effective head-on collision between the particle beams, thereby restoring the geometric factor to 0.8 [K. Oide and K. Yokoya, Phys. Rev. A 40, 315 (1989).]. Noise injected through the rf/low level rf (llrf) system could cause significant transverse emittance growth and limit luminosity lifetime. In this work, a theoretical relationship between the phase and amplitude rf noise spectrum and the transverse emittance growth rate is derived, for a hadron machine assuming zero synchrotron radiation damping and broadband rf noise, excluding infinitely narrow spectral lines. This derivation is for a single beam. Both amplitude and phase noise are investigated. The potential improvement in the presence of the transverse damper is also investigated.

  3. Increased diffuse radiation fraction does not significantly accelerate plant growth

    NASA Astrophysics Data System (ADS)

    Angert, Alon; Krakauer, Nir

    2010-05-01

    A recent modelling study (Mercado et al., 2009) claims that increased numbers of scattering aerosols are responsible for a substantial fraction of the terrestrial carbon sink in recent decades because higher diffuse light fraction enhances plant net primary production (NPP). Here we show that observations of atmospheric CO2 seasonal cycle and tree ring data indicate that the relation between diffuse light and NPP is actually quite weak on annual timescales. The inconsistency of these data with the modelling results may arise because the relationships used to quantify the enhancement of NPP were calibrated with eddy covariance measurements of hourly carbon uptake. The effect of diffuse-light fraction on carbon uptake could depend on timescale, since this effect varies rapidly as sun angle and cloudiness change, and since plants can respond dynamically over various timescales to change in incoming radiation. Volcanic eruptions, such as the eruption of Mount Pinatubo in 1991, provide the best available tests for the effect of an annual-scale increase in the diffuse light fraction. Following the Pinatubo Eruption, in 1992 and 1993, a sharp decrease in the atmospheric CO2 growth rate was observed. This could have resulted from enhanced plant carbon uptake. Mercado et al. (2009) argue that largely as a result of the (volcanic aerosol driven) increase in diffuse light fraction, NPP was elevated in 1992, particularly between 25° N-45° N where annual NPP was modelled to be ~0.8 PgC (~10%) above average. In a previous study (Angert et al., 2004) a biogeochemical model (CASA) linked to an atmospheric tracer model (MATCH), was used to show that a diffuse-radiation driven increase in NPP in the extratropics will enhance carbon uptake mostly in summer, leading to a lower CO2 seasonal minimum. Here we use a 'toy model' to show that this conclusion is general and model-independent. The model shows that an enhanced sink of 0.8 PgC, similar to that modelled by Mercado et al. (2009), will result in a measurable decrease (~0.6ppm) in the seasonal CO2 minimum. This holds regardless of whether the sink is the result of 1) An increase in NPP, or 2) The combined effect of a temperature-driven decrease in heterotrophic respiration (Rh) and no change in NPP. This is since both NPP and Rh peak in summer. By contrast, observations from the NOAA global CO2 monitoring network show the opposite change in the seasonal minimum in 1992 and 1993 (~0.2ppm increase) both at Mauna Loa, and in the Marine Boundary Layer mean (>20° N), which is hard to reconcile with increased NPP in northern summer. Another indicator of annual NPP is tree wood increment. Previous work (Krakauer et al., 2003) showed that the average response in tree ring series after past Pinatubo-size volcanic eruptions implied lower NPP north of 45° N, presumably as a result of shorter growing season and lower total irradiance induced by scattering aerosols, and no significant change in NPP at lower latitudes. Here we show that In 1992, after the Pinatubo eruption, ring width in the 25° N-45° N band was 99.3±2.9% of average (n=351 sites), similar to the average of 100.4±2.2% over past eruptions (n=15 eruptions) (Uncertainty is given as 2 SE.). These results are also inconsistent with substantial NPP enhancement, although a limitation of the tree-ring approach is that available measurements do not uniformly sample the latitude band. The combined evidence of tree rings and the CO2 seasonal cycle shows that the enhancement of NPP by scattering aerosols on annual timescales is weak. This result suggests that reducing aerosols through stricter pollution controls may strengthen the land carbon sink, while geo-engineering schemes which aim to mitigate global warming by spreading scattering aerosols in the stratosphere may weaken it.

  4. Reptation-induced coalescence of tunnels and cavities in Escherichia Coli XylE transporter conformers accounts for facilitated diffusion.

    PubMed

    Cunningham, Philip; Naftalin, Richard J

    2014-11-01

    Structural changes and xylose docking to eight conformers of Escherichia Coli XylE, a xylose transporter similar to mammalian passive glucose transporters GLUTs, have been examined. Xylose docks to inward and outward facing conformers at a high affinity central site (K(i) 4-20 µM), previously identified by crystallography and additionally consistently docks to lower affinity sites in the external and internal vestibules (K(i) 12-50 µM). All these sites lie within intramolecular tunnels and cavities. Several local regions in the central transmembrane zone have large positional divergences of both skeleton carbon C? positions and side chains. One such in TM 10 is the destabilizing sequence G388-P389-V390-C391 with an average RMSD (4.5 ± 0.4 Å). Interchange between conformer poses results in coalescence of tunnels with adjacent cavities, thereby producing a transitory channel spanning the entire transporter. A fully open channel exists in one inward-facing apo-conformer, (PDB 4ja4c) as demonstrated by several different tunnel-finding algorithms. The conformer interchanges produce a gated network within a branched central channel that permits staged ligand diffusion across the transporter during the open gate periods. Simulation of this model demonstrates that small-scale conformational changes required for sequentially opening gate with frequencies in the ns-?s time domain accommodate diffusive ligand flow between adjacent sites with association-dissociation rates in the ?s-ms domain without imposing delays. This current model helps to unify the apparently opposing concepts of alternate access and multisite models of ligand transport. PMID:25163893

  5. Statistical-mechanical theory of diffusion-controlled particle growth on a surface: Kinetics of diffusion-limited currents

    NASA Astrophysics Data System (ADS)

    Tokuyama, Michio

    1990-11-01

    A new statistical-mechanical theory of diffusion-controlled three-dimensional growth of hemispherical nuclei on a two-dimensional surface is presented. Diffusive interactions among nuclei are rigorously studied. It is demonstrated that long-range interactions cause corrections to mean-field results obtained in the limit of the zero volume fraction of the nuclei. The importance of those corrections on the growth processes are stressed. Fluctuations around the average motion are also explicitly explored. It is shown that there are two kinds of macroscopic fluctuations in the present system: thermal fluctuations already existing at the beginning and non-thermal fluctuations generated by the long-range interactions. The kinetics of diffusion-limited currents are studied from new viewpoints thus obtained.

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

    SciTech Connect

    Nateghi, N. Ménard, D.; Masut, R. A.

    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.

  7. 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 diffusion of dopants in silicon. This phenomenon has mostly been studied using boron marker layers. We have performed an experiment using boron, phosphorus, and dislocation markers to compare TED effects

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

    E-print Network

    Watkins, Jim

    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 front. We compare these profiles to models of water diffusion in rhyolite to estimate timescales

  9. 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

  10. Slow Diffusion Underlies Alternation of Fast and Slow Growth Periods of Microtubule Assembly

    PubMed Central

    2014-01-01

    In vitro microtubule assembly exhibits a rhythmic phenomenon, that is, fast growth periods alternating with slow growth periods. Mechanism underlying this phenomenon is unknown. Here a simple diffusion mechanism coupled with small diffusion coefficients is proposed to underlie this phenomenon. Calculations based on previously published results demonstrate that such a mechanism can explain the differences in the average duration of the interval encompassing a fast growth period and a slow growth period in in vitro microtubule assembly experiments in different conditions. Because no parameter unique to the microtubule assembly process is involved in the analysis, the proposed mechanism is expected to be generally applicable to heterogeneous chemical reactions. Also because biological systems are characterized by heterogeneous chemical reactions, the diffusion-based rhythmic characteristic of heterogeneous reactions is postulated to be a fundamental element in generating rhythmic behaviors in biological systems. PMID:24605057

  11. Multiple cluster growth of ultra-thin films with anisotropic edge diffusion

    NASA Astrophysics Data System (ADS)

    Wang, Dai-mu; Wu, Zi-qin

    2001-01-01

    The multiple cluster growth of ultra-thin films on a hexagonal substrate with fractal, dendritic and compact morphology has been studied by computer simulation. The influence of the different diffusion processes along island edges on the island shape has been investigated. The results show that the anisotropic corner diffusion induces the dendritic growth and the anisotropic step diffusion can promote the anisotropic growth and cause the ramified islands to grow in three directions. In the case of compact growth, the island shape is mainly determined by the anisotropic corner crossing process. The non-uniform distribution of the multiple cluster formation can be described quantitatively by multifractal. With patterns changing from fractal to compact islands, the width and height of the bell-like or hook-like multifractal spectra increase, while the top f(?) decreases.

  12. Steady diffusion model for olivine-plagioclase corona growth

    NASA Astrophysics Data System (ADS)

    Nishiyama, Tadao

    1983-02-01

    This paper describes an application of a steady diffusion model ( JOESTEN, 1977) to an olivineplagioclase corona and some new results about a theoretical background on the steady diffusion equations. The olivine-plagioclase corona in a metanorite from Mt. Ikoma. Japan, has a layer sequence of olivinecummingtonite-hornblende + spinel-plagioclase. An analysis of a set of steady diffusion equations for the corona in the four-component system, MgO-AlO 3/2-SiO 2-Na 0.1Ca 0.9O 0.95 (NC) with excess H 2O. successfully gives the exchange cycle ( FISHER, 1973) in the layer sequence with specific values of the phenomenological coefficients' ratios; L MgMg/L SiSi, L MgMg/L AlAl and L MgMg/L NCNC. The factor which controls most strictly the stability of the layer sequence under isobaric-isothermal conditions is L MgMg/L AlAl. Theoretical considerations on the steady diffusion equations show that the L-ratios does not depend on concentrations even if the phenomenological coefficients themselves are functions of concentrations. Equivalence of the steady state condition and the minimum rate of entropy production law ( PRIGOGINE, 1967) is also proved for the system with fixed chemical potential gradients under isobaric-isothermal conditions, such as reaction bands. These results give a strong background for the model.

  13. Crystal Growth of Extended Solids by Nonaqueous Gel Diffusion

    E-print Network

    Yaghi, Omar M.

    -gel processing, nanocomposites, and bio- mineralization,2,3 their development as crystallization and diffusion of coordination solids is demonstrated by the assembly of Zn(HBTC)(NC5H5)2,C2H5OH (HBTC ) 1,3,5-C6H3(CO2)2- (CO2H on zinc) of pure Zn(HBTC)- (NC5H5)2,C2H5OH.10 Inspection of the microcrystalline product using an optical

  14. An early report of growth of an Aspergillus species on the wall of a lung cavity.

    PubMed Central

    Doyle, L

    1989-01-01

    A report by Bristowe in 1854 of a vegetable fungus growing in a lung cavity and identified as an Aspergillus was almost certainly one of the earliest reports of A fumigatus colonisation. Images PMID:2648644

  15. A creep cavity growth model for creep-fatigue life prediction of a unidirectional W/Cu composite

    NASA Technical Reports Server (NTRS)

    Kim, Young-Suk; Verrilli, Michael J.; Halford, Gary R.

    1992-01-01

    A microstructural model was developed to predict creep-fatigue life in a (0)(sub 4), 9 volume percent tungsten fiber-reinforced copper matrix composite at the temperature of 833 K. The mechanism of failure of the composite is assumed to be governed by the growth of quasi-equilibrium cavities in the copper matrix of the composite, based on the microscopically observed failure mechanisms. The methodology uses a cavity growth model developed for prediction of creep fracture. Instantaneous values of strain rate and stress in the copper matrix during fatigue cycles were calculated and incorporated in the model to predict cyclic life. The stress in the copper matrix was determined by use of a simple two-bar model for the fiber and matrix during cyclic loading. The model successfully predicted the composite creep-fatigue life under tension-tension cyclic loading through the use of this instantaneous matrix stress level. Inclusion of additional mechanisms such as cavity nucleation, grain boundary sliding, and the effect of fibers on matrix-stress level would result in more generalized predictions of creep-fatigue life.

  16. Diffusion growth of titanium carbide film on NiTi substrate

    SciTech Connect

    Lesokhin, S.; Levin, L.

    1996-10-01

    The formation of titanium carbide during hot filament assisted carburizing of NiTi alloy was investigated. Phase content and morphology of the diffusion zone were examined by X-ray diffraction, X-ray microanalysis, SEM, and Auger electron spectroscopy. The growth of stable and adherent TiC film was observed. A non-planarity of interphase boundary was noticed. The applicability of the chemical diffusion approach to the analysis of the experimentally observed interface instability is discussed. A criterion, taking into account the influence of growth stresses on the stability of the flat interface, is developed by means of linear perturbation analysis.

  17. Soot Surface Growth in Laminar Hydrocarbon/Air Diffusion Flames. Appendix B

    NASA Technical Reports Server (NTRS)

    El-Leathy, A. M.; Xu, F.; Kim, C. H.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2001-01-01

    The structure and soot surface growth properties of round laminar jet diffusion flames were studied experimentally. Measurements were made along the axes of ethylene-, propylene-propane- and acetylene-benzene-fueled flames burning in coflowing air at atmospheric pressure with the reactants at normal temperature. The measurements included soot structure, soot concentrations, soot temperatures, major gas species concentrations, some radial species (H, OH and O) concentrations, and gas velocities. These measurements yielded the local flame properties that are thought to affect soot surface growth as well as local soot surface growth rates. When present results were combined with similar earlier observations of acetylene-fueled laminar jet diffusion flames, the results suggested that soot surface growth involved decomposition of the original fuel to form acetylene and H, which were the main reactants for soot surface growth, and that the main effect of the parent fuel on soot surface growth involved its yield of acetylene and H for present test conditions. Thus, as the distance increased along the axes of the flames, soot formation (which was dominated by soot surface growth) began near the cool core of the flow once acetylene and H appeared together and ended near the flame sheet when acetylene disappeared. Species mainly responsible for soot oxidation - OH and O2 were present throughout the soot formation region so that soot surface growth and oxidation proceeded at the same time. Present measurements of soot surface growth rates (corrected for soot surface oxidation) in laminar jet diffusion flames were consistent with earlier measurements of soot surface growth rates in laminar premixed flames and exhibited good agreement with existing Hydrogen-Abstraction/Carbon-Addition (HACA) soot surface growth mechanisms in the literature with steric factors in these mechanisms having values on the order of unity, as anticipated.

  18. Soot Surface Growth in Laminar Hydrocarbon/Air Diffusion Flames. Appendix J

    NASA Technical Reports Server (NTRS)

    El-Leathy, A. M.; Xu, F.; Kim, C. H.; Faeth, G. M.; Yuan, Z.-G. (Technical Monitor); Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2003-01-01

    The structure and soot surface growth properties of round laminar jet diffusion flames were studied experimentally. Measurements were made along the axes of ethylene-, propylene-propane- and acetylene-benzene-fueled flames burning in coflowing air at atmospheric pressure with the reactants at normal temperature. The measurements included soot structure, soot concentrations, soot temperatures, major gas species concentrations, some radial species (H, OH and 0) concentrations, and gas velocities. These measurements yielded the local flame properties that are thought to affect soot surface growth as well as local soot surface growth rates. When present results were combined with similar earlier observations of acetylene-fueled laminar jet diffusion flames, the results suggested that soot surface growth involved decomposition of the original fuel to form acetylene and H, which were the main reactants for soot surface growth, and that the main effect of the parent fuel on soot surface growth involved its yield of acetylene and H for present test conditions. Thus, as the distance increased along the axes of the flames, soot formation (which was dominated by soot surface growth) began near the cool core of the flow once acetylene and H appeared together and ended near the flame sheet when acetylene disappeared. Species mainly responsible for soot oxidation - OH and 02 were present throughout the soot formation region so that soot surface growth and oxidation proceeded at the same time. Present measurements of soot surface growth rates (corrected for soot surface oxidation) in laminar jet diffusion flames were consistent with earlier measurements of soot surface growth rates in laminar premixed flames and exhibited good agreement with existing Hydrogen-Abstraction/Carbon-Addition (HACA) soot surface growth mechanisms in the literature with steric factors in these mechanisms having values on the order of unity, as anticipated.

  19. Multiple wavelength vertical-cavity surface-emitting laser arrays using surface-controlled MOCVD growth rate enhancement and reduction

    SciTech Connect

    Ortiz, G.G.; Hains, C.P.; Luong, S.; Cheng, J.; Hou, H.Q.; Vawter, G.A.

    1997-04-01

    Multiple-wavelength VCSEL and photodetector arrays are useful for wavelength-multiplexed fiberoptic networks, and for optical crosstalk isolation in parallel, free-space interconnects. Multiple wavelength VCSEL arrays have been obtained by varying the growth rate using thermal gradients caused by a backside-patterned substrate, by growth enhancement on a patterned substrate, and by varying the cavity length through anodic oxidation and selective etching of the wafer. We show here for the first time both the enhancement and the reduction of the growth rate of the entire VCSEL structure on a topographically patterned substrate, and demonstrate the controlled variation of the lasing wavelengths of a VCSEL array over an extended spectral range.

  20. Substrate-mediated diffusion-induced growth of single-crystal nanowires.

    PubMed

    Mohammad, S Noor

    2009-11-28

    Theoretical investigations of the growth and growth rates of single-crystal nanowires (NWs) by vapor phase mechanisms have been carried out. Substrate-induced processes are assumed to dominate this growth. The modeling for growth takes adsorption, desorption, surface scattering, and diffusion into account. It takes into consideration also the retarding electric field arising from the scattering of the NW vapor species by both the substrate and the NW sidewalls. Growth characteristics under the influence of the retarding electric field have been studied. Competitive roles of adatom diffusivity and the electric field in the NW growth are elucidated. Influence of the growing NW length and the adatom impingement rate on the NW growth rate has been described. The effect of adatom collection area around each NW has been examined. The NW tapering and kinking have been explained. The fundamentals of the substrate induction and details of the growth parameters have been analyzed. The influence of foreign element catalytic agents in the vapor-liquid-solid mechanism has been presented. All these have led to the understanding and resolution of problems, controversies, and contradictions involving substrate-induced NW growths. PMID:19947700

  1. Double-Diffusive Convection During Growth of Halides and Selenides

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Su, Ching-Hua; Duval, Walter M. B.

    2015-01-01

    Heavy metal halides and selenides have unique properties which make them excellent materials for chemical, biological and radiological sensors. Recently it has been shown that selenohalides are even better materials than halides or selenides for gamma-ray detection. These materials also meet the strong needs of a wide band imaging technology to cover ultra-violet (UV), midwave infrared wavelength (MWIR) to very long wavelength infrared (VLWIR) region for hyperspectral imager components such as etalon filters and acousto-optic tunable filters (AO). In fact AOTF based imagers based on these materials have some superiority than imagers based on liquid crystals, FTIR, Fabry-Perot, grating, etalon, electro-optic modulation, piezoelectric and several other concepts. For example, broadband spectral and imagers have problems of processing large amount of information during real-time observation. Acousto-Optic Tunable Filter (AOTF) imagers are being developed to fill the need of reducing processing time of data, low cost operation and key to achieving the goal of covering long-wave infrared (LWIR). At the present time spectral imaging systems are based on the use of diffraction gratings are typically used in a pushbroom or whiskbroom mode. They are mostly used in systems and acquire large amounts of hyperspectral data that is processed off-line later. In contrast, acousto-optic tunable filter spectral imagers require very little image processing, providing new strategies for object recognition and tracking. They are ideally suited for tactical situations requiring immediate real-time image processing. But the performance of these imagers depends on the quality and homogeneity of acousto-optic materials. In addition for many systems requirements are so demanding that crystals up to sizes of 10 cm length are desired. We have studied several selenides and halide crystals for laser and AO imagers for MWIR and LWIR wavelength regions. We have grown and fabricated crystals of several materials such as mercurous chloride, mercurous bromide, mercurous iodide, lead chloride lead bromide, lead iodide, thallium arsenic selenide, gallium selenide, zince sulfide zinc selenide and several crystals into devices. We have used both Bridgman and physical vapor transport (PVT) crystal growth methods. In the past have examined PVT growth numerically for conditions where the boundary of the enclosure is subjected to a nonlinear thermal profile. Since past few months we have been working on binary and ternary materials such as selenoiodides, doped zinc sulfides and mercurous chloro bromide and mercurous bromoiodides. In the doped and ternary materials thermal and solutal convection play extremely important role during the growth. Very commonly striations and banding is observed. Our experiments have indicated that even in highly purified source materials, homogeneity in 1-g environment is very difficult. Some of our previous numerical studies have indicated that gravity level less than 10-4 (?-g) helps in controlling the thermosolutal convection. We will discuss the ground based growth results of HgClxBr(1-x) and ZnSe growth results for the mm thick to large cm size crystals. These results will be compared with our microgravity experiments performed with this class of materials. For both HgCl-HgBr and ZnS-ZnSe the lattice parameters of the mixtures obey Vagard's law in the studied composition range. The study demonstrates that properties are very anisotropic with crystal orientation, and performance achievement requires extremely careful fabrication to utilize highest figure of merit. In addition, some parameters such as crystal growth fabrication, processing time, resolution, field of view and efficiency will be described based on novel solid solution materials. It was predicted that very similar to the pure compounds solid solutions also have very large anisotropy, and very precise oriented and homogeneous bulk and thin film crystals is required to achieve maximum performance of laser or imagers. Some of the parameters controlling the homogeneity su

  2. Experimental techniques for determination of the role of diffusion and convection in crystal growth from solution

    NASA Technical Reports Server (NTRS)

    Zefiro, L.

    1980-01-01

    Various studies of the concentration of the solution around a growing crystal using interferometric techniques are reviewed. A holographic interferometric technique used in laboratory experiments shows that a simple description of the solution based on the assumption of a purely diffusive mechanism appears inadequate since the convection, effective even in reduced columns, always affects the growth.

  3. Matrix rheology effects on reaction rim growth II: coupled diffusion and creep model

    E-print Network

    Podladchikov, Yuri

    Matrix rheology effects on reaction rim growth II: coupled diffusion and creep model D. W. SCHMID,1 of the matrix that surrounds the reaction sites where the volume change takes place. Consequently, mineral reactions and the mechanical response of the rock matrix are coupled. A companion paper in this issue

  4. Introducing Carbon Diffusion Barriers for Uniform, High-Quality Graphene Growth from Solid Sources

    PubMed Central

    2013-01-01

    Carbon diffusion barriers are introduced as a general and simple method to prevent premature carbon dissolution and thereby to significantly improve graphene formation from the catalytic transformation of solid carbon sources. A thin Al2O3 barrier inserted into an amorphous-C/Ni bilayer stack is demonstrated to enable growth of uniform monolayer graphene at 600 °C with domain sizes exceeding 50 ?m, and an average Raman D/G ratio of <0.07. A detailed growth rationale is established via in situ measurements, relevant to solid-state growth of a wide range of layered materials, as well as layer-by-layer control in these systems. PMID:24024736

  5. Growth kinetics of circular liquid domains on vesicles by diffusion-controlled coalescence.

    PubMed

    Seki, Kazuhiko; Komura, Shigeyuki; Ramachandran, Sanoop

    2013-05-15

    Motivated by recent experiments on multicomponent membranes, the growth kinetics of domains on vesicles are theoretically studied. It is known that the steady-state rate of coalescence cannot be obtained by taking the long-time limit of the coalescence rate when the membrane is regarded as an infinite two-dimensional (2D) system. The steady-state rate of coalescence is obtained by explicitly taking into account the spherical vesicle shape. Using the expression for the 2D diffusion coefficient obtained in the limit of small domain size, an analytical expression for domain growth kinetics is obtained when a circular shape is always maintained. For large domains, the growth kinetics are discussed by investigating the size dependence of the coalescence rate, using the expression for the diffusion coefficient of arbitrary domain size. PMID:23604048

  6. Hair-inspired crystal growth of HOA in cavities of cellulose matrix via hydrophobic-hydrophilic interface interaction.

    PubMed

    He, Meng; Kwok, Ryan T K; Wang, Zhenggang; Duan, Bo; Tang, Ben Zhong; Zhang, Lina

    2014-06-25

    As one of the most ordinary phenomena in nature, numerous pores on animal skins induce the growth of abundant hairs. In this study, cavities of a cellulose matrix were used as hard templates to lead the hair-inspired crystal growth of 12-hydroxyoctadecanoic acid (HOA) through hydrophobic-hydrophilic interface interaction, and short hair-like HOA crystals with a smooth surface were formed on cellulose films. In our findings, by using solvent evaporation induced crystallization, hydrophobic HOA grew along the hydrophilic cellulose pore wall to form regular vertical worm-like and pillar-like crystals with an average diameter of about 200 nm, depending on the experimental conditions and HOA concentration. The formation mechanism of the short hair-like HOA crystals as well as the structure and properties of the cellulose/HOA submicrometer composite films were studied. The pores of the cellulose matrix supplied not only cavities for the HOA crystals fixation but also hydrophilic shells to favor the vertical growth of the relatively hydrophobic HOA crystals. The cellulose/HOA submicrometer composite films exhibited high hydrophobicity, as a result of the formation of the solid/air composite surface. Furthermore, 4-(1,2,2-triphenylethenyl) benzoic acid, an aggregation-induced emission luminogen, was used to aggregate on the cellulose surface with HOA to emit and monitor the HOA crystal growth, showing bifunctional photoluminscence and self-cleaning properties. This work opens up a novel one-step pathway to design bio-inspired submicrometer materials by utilizing natural products, showing potential applications in self-cleaning optical devices. PMID:24865837

  7. Effect of diffusion from a lateral surface on the rate of GaN nanowire growth

    SciTech Connect

    Sibirev, N. V. Tchernycheva, M.; Cirlin, G. E.; Patriarche, G.; Harmand, J. C.; Dubrovskii, V. G.

    2012-06-15

    The kinetics of the growth of GaN crystalline nanowires on a Si (111) surface with no catalyst is studied experimentally and theoretically. Noncatalytic GaN nanowires were grown by molecular-beam epitaxy with AlN inserts, which makes it possible to determine the rate of the vertical growth of nanowires. A model for the formation of GaN nanowires is developed, and an expression for their rate of growth is derived. It is shown that, in the general case, the dependence of the rate of growth on the nanowire diameter has a minimum. The diameter corresponding to the experimentally observed minimum of the rate of growth steadily increases with increasing diffusion flux from the lateral surface.

  8. Non-linear resonance of fluids in a crystal growth cavity

    NASA Technical Reports Server (NTRS)

    Wang, Francis C.

    1996-01-01

    In the microgravity environment, the effect of gravity on fluid motion is much reduced. Hence, secondary effects such as vibrations, jitters, surface tension, capillary effects, and electromagnetic forces become the dominant mechanism of fluid convection. Numerous studies have been conducted to investigate fluid behavior in microgravity with the ultimate goal of developing processes with minimal influence from convection. Industrial applications such as crystal growth from solidification of melt and protein growth for pharmatheutical application are just a few examples of the vast potential benefit that can be reaped from material processing in space. However, a space laboratory is not immune from all undesirable disturbances and it is imperative that such disturbances be well understood, quantifiable, and controlled. Non-uniform and transient accelerations such as vibrations, jitters, and impulsive accelerations exist as a result of crew activities, space vehicle maneuvering, and the operations of on-board equipment. Measurements conducted on-board a U.S. Spacelab showed the existence of vibrations in the frequency range of 1 to 100 Hz with a dominant mode of 17 Hz and harmonics of 54 Hz. The observed vibration is not limited to any coordinate plane but exists in all directions. Similar situation exists on-board the Russian MIR space station. Due to the large structure of its design, the future International Space Station will have its own characteristic vibration spectrum. It is well known that vibration can exert substantial influence on heat and mass transfer processes, thus hindering any attempts to achieve a diffusion-limited process. Experiments on vibration convection for a liquid-filled enclosure under one-g environment showed the existence of different flow regimes as vibration frequency and intensity changes. Results showed the existence of a resonant frequency, near which the enhancement is the strongest, and the existence of a high frequency asymptote. Numerical simulations of vibration convection have been conducted by Yurkov, Fu and Shieh, and by Wang. These analyses considered a two-dimensional air-filled cell under weightlessness condition and showed results similar to those of the experiments. It is not yet known whether resonance convection can be triggered by jitter alone or whether it requires the interaction of jitter with other convective forces in low gravity. An order of magnitude analysis, however, can be used to show the dependence of the resonance frequency on the fluid Prandtl number. Even though the onset of resonance convection may depend on other factors, results indicates that fluids with low Prandtl numbers are more susceptible to resonance than those with high Prandtl numbers. The current study is aimed at gaining additional insights to this problem using germanium as working fluid. Germanium was chosen for this analysis because of its common usage in solidification process and its relatively low Prandtl number (Pr = 0.02).

  9. 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

    2015-09-14

    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.

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

    NASA Astrophysics Data System (ADS)

    Cerbino, Roberto; Sun, Yifei; Donev, Aleksandar; Vailati, Alberto

    2015-09-01

    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.

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

    PubMed

    Cerbino, Roberto; Sun, Yifei; Donev, Aleksandar; Vailati, Alberto

    2015-01-01

    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. PMID:26419420

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

    PubMed Central

    Cerbino, Roberto; Sun, Yifei; Donev, Aleksandar; Vailati, Alberto

    2015-01-01

    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. PMID:26419420

  13. 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.

  14. Time scales of polymetamorphism from diffusive alteration of garnet growth zoning (Wölz Complex, Eastern Alps)

    NASA Astrophysics Data System (ADS)

    Bestel, M.; Gawronski, T.; Abart, R.

    2009-04-01

    Garnet prophyroblasts in micaschists from the Wölz crystalline complex (Eastern Alps) typically show two distinct growth zones. The first growth zone is of Permian age and forms the garnet cores. The second growth zone is of Cretaceous age and forms the garnet rims. Both growth zones show pronounced compositional zoning. From garnet isopleth geo thermo-barometry garnet growth at temperatures of 550 to 570°C and pressures of 400 to 500 MPa is inferred for garnet cores and growth at similar temperatures and pressures of 700 to 800 MPa is inferred for garnet rims. In several samples the primary growth zoning of the garnet cores is modified by late stage diffusive alteration along cracks, around mineral inclusions, and at the interface between the first and second garnet growth zone. Two generations of alteration phenomena are discerned. A first generation of alteration phenomena extends over several 100 µm into the pre-existing garnet cores and is ascribed to diffusive exchange with the rock matrix during a long lasting high temperature anneal associated with Permian metamorphism. A second generation of alteration phenomena is restricted to an about 50 µm wide zone along the interface between the two garnet growth zones and around mineral inclusion in the second garnet growth zone. These alteration phenomena are ascribed to diffusion controlled exchange between the first and second garnet growth zones and to late stage exchange between garnet and the rock matrix during Eo-Alpine metamorphism in the Cretaceous. Whereas the time scale obtained for the high temperature stage of the Permian event is on the order of 10 Ma, the time scale obtained for the Cretaceous event is only on the order of 0.2 Ma. This reflects the long lived nature of a stage of elevated heat flux and high geothermal gradient associated with an extensional regime in the Austroalpine realm during the Permian and the lower Triassic. The comparatively short duration of the Cretaceous event reflects rapid exhumation of the Austroalpine lower plate subsequent to the intra continental subduction, which was associated with the Eo-Alpine continent-continent collision.

  15. Transition in the Fractal Properties from Diffusion Limited Aggregation to Laplacian Growth via their Generalization

    E-print Network

    H. George E. Hentschel; Anders Levermann; Itamar Procaccia

    2002-05-06

    We study the fractal and multifractal properties (i.e. the generalized dimensions of the harmonic measure) of a 2-parameter family of growth patterns that result from a growth model that interpolates between Diffusion Limited Aggregation (DLA) and Laplacian Growth Patterns in 2-dimensions. The two parameters are \\beta which determines the size of particles accreted to the interface, and C which measures the degree of coverage of the interface by each layer accreted to the growth pattern at every growth step. DLA and Laplacian Growth are obtained at \\beta=0, C=0 and \\beta=2, C=1, respectively. The main purpose of this paper is to show that there exists a line in the \\beta-C phase diagram that separates fractal (D0, and derive for them a scaling relation D=2 * D_3. We then propose that this family has growth patterns for which D=2 for some C>C_{cr}, where C_{cr} may be zero. Next we consider the whole \\beta-C phase diagram and define a line that separates 2-dimensional growth patterns from fractal patterns with Dviolet cut-off length.

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

    SciTech Connect

    Iwamatsu, Masao

    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.

  17. Traveling wave solutions of a reaction diffusion model for bacterial growth

    NASA Astrophysics Data System (ADS)

    Mansour, M. B. A.

    2007-09-01

    In this paper, we consider a reaction-diffusion model for the bacterial growth. Mathematical analysis on the traveling wave solutions of the model is performed. This includes traveling wave analysis and numerical simulations of wave front propagation for a special case. Specifically, we show that such solutions exist only for wave speeds greater than some minimum speed giving wave with a sharp front. The minimum speed is estimated and the wave profile is calculated and compared with different numerical methods.

  18. On Traveling Wave Fronts in a Bacterial Growth Model with Density-Dependent Diffusion and Chemotaxis

    NASA Astrophysics Data System (ADS)

    Mansour, M. B. A.

    2011-04-01

    Bacterial colonies often generate patterns that are characterized by fingerlike projections growing out of the propagating front. In this paper, we analyze the traveling wave fronts in bacterial growth model that accounts for chemotactic movement as well as random motion in density-dependent diffusion. Specifically, the existence of traveling wave solutions to model equations is examined by means of methods of local linear and nonlinear analysis, and numerical simulations. The occurrence is shown of both sharp and smooth traveling wave fronts.

  19. Solute Layers and Double-Diffusive Interfaces during the Solidification of NH{sub 4}Cl-H{sub 2}O in Rectangular Cavities

    SciTech Connect

    Wen, Z. X.; Lu, J.; Bai, B. F.

    2010-03-01

    Flow and temperature fields during the solidification of hypereutectic and hypoeutectic NH{sub 4}Cl-H{sub 2}O solution in rectangular cavities were measured by a particle image velocimetry(PIV) and a weak perturbation thermocouple network, respectively. Double-diffusive convections caused by the coupling effects of temperature and solute gradients were studied by the experiment. During the solidification of hypereutectic solution, the rejected water near the solidification interface will lead to dilute solute layers and double-diffusive interfaces. As the continued rejection of water, the layer and interface will evolve into instability and a multi-layer and multi-interface structure will be formed. To the hypoeutectic solution, the rejection of NH{sub 4}Cl near the solidification interface will form a dense solute layer. When the thickness of the dense solute layer is large enough, the coupling effects of stabilizing solute gradient and unstable temperature gradient will lead to new solute layers. The solute layers and double-diffusive interfaces will evolve stably and have no breakup of the double-diffusive interfaces during the solidification of hypoeutectic solution.

  20. Rotational diffusion of receptors for epidermal growth factor measured by time-resolved phosphorescence depolarization

    NASA Astrophysics Data System (ADS)

    Zidovetzki, Raphael; Johnson, David A.; Arndt-Jovin, Donna J.; Jovin, Thomas M.

    1991-06-01

    The cell surface receptor for epidermal growth factor (EGFR) is one of the most studied integral membrane proteins. The receptor is widely distributed in cells and tissues of mammalian and avian tissues and plays an important role in growth control. Binding of the epidermal growth factor (EGF) to EGFR initiates a complex biological response, which includes self-phosphorylation of the receptor due to an intrinsic tyrosine kinase activity, phosphorylation of other membrane proteins, increased intake of metabolites, and increased proliferation. Complete amino acid sequence of EGFR revealed a high degree of homology with viral oncogenes and allowed tentative identification of an external hormone binding domain, a transmembrane domain, and a cytoplasmic domain that includes tyrosine kinase activity. EGF binding induces rapid aggregation of EGFR, a process which was also observed on other receptor systems. These and other observations led to a hypothesis that microaggregation of EGFR is a necessary prerequisite for the biological response of EGF. A direct approach to study the processes of oligomerization of cell membrane proteins is to measure their mobility under various conditions. The lateral mobility of the EGFR was studied on mouse 3T3 fibroblasts and on A431 cells. However, an examination of the equations for the lateral and rotational diffusion in membranes shows that only rotational diffusion is strongly dependent on the size of the diffusing entity. A method of measuring protein rotational diffusion by time-resolved phosphorescence has proved to be very useful in the analysis of both in vivo and in vitro systems. The authors apply this method to study the mobility of EGFR on living A431 cells and membrane preparations.

  1. Mechanism of growth of Bi2+ x Sr2- y CuO6+ ? single crystals in gas cavities in a KCl melt

    NASA Astrophysics Data System (ADS)

    Gorina, Yu. I.; Kalyuzhnaya, G. A.; Rodin, V. V.; Sentyurina, N. N.; Stepanov, V. A.; Chernook, S. G.

    2007-07-01

    High-quality Bi2+ x Sr2- y CuO6+ ? single crystals in a wide range of superconducting properties, from optimally doped to strongly underdoped (including insulators), have been obtained by free growth in gas cavities formed in a KCl flux. A model of crystal growth is proposed, in which the decisive parameter is the chemical transport in a cavity at a low partial oxygen pressure and feeding of the gaseous medium from the charge heated to a higher temperature. In this case, layer-by-layer growth through the vapor-solid mechanism is implemented. This growth, as the most ordered process, makes it possible to obtain faceted plates and whiskers with specular faces, without segregation of other phases.

  2. Diffuse-Type Gastric Carcinoma: Progression, Angiogenesis, and Transforming Growth Factor ? Signaling

    PubMed Central

    Komuro, Akiyoshi; Yashiro, Masakazu; Iwata, Caname; Morishita, Yasuyuki; Johansson, Erik; Matsumoto, Yoshiko; Watanabe, Akira; Aburatani, Hiroyuki; Miyoshi, Hiroyuki; Kiyono, Kunihiko; Shirai, Yo-taro; Suzuki, Hiroshi I.; Hirakawa, Kosei; Kano, Mitsunobu R.

    2009-01-01

    Background Diffuse-type gastric carcinoma is a cancer with poor prognosis that has high levels of transforming growth factor ? (TGF-?) expression and thick stromal fibrosis. However, the association of TGF-? signaling with diffuse-type gastric carcinoma has not been investigated in detail. Methods We used a lentiviral infection system to express a dominant-negative TGF-? type II receptor (dnT?RII) or green fluorescent protein (GFP) as a control in the diffuse-type gastric carcinoma cell lines, OCUM-2MLN and OCUM-12. These infected cells and the corresponding parental control cells were subcutaneously or orthotopically injected into nude mice. Angiogenesis was inhibited by infecting cells with a lentivirus carrying the gene for angiogenic inhibitor thrombospondin-1 or by injecting mice intraperitoneally with the small-molecule angiogenic inhibitor sorafenib or with anti-vascular endothelial growth factor (VEGF) neutralizing antibody (six or eight mice per group). Expression of phospho-Smad2 and thrombospondin-1 was investigated immunologically in human gastric carcinoma tissues from 102 patients. All statistical tests were two-sided. Results Expression of dnT?RII into OCUM-2MLN cells did not affect their proliferation in vitro, but it accelerated the growth of subcutaneously or orthotopically transplanted tumors in vivo (eg, for mean volume of subcutaneous tumors on day 10 relative to that on day 0: dnT?RII tumors = 3.49 and GFP tumors = 2.46, difference = 1.02, 95% confidence interval [CI] = 0.21 to 1.84; P = .003). The tumors expressing dnT?RII had higher levels of angiogenesis than those expressing GFP because of decreased thrombospondin-1 production. Similar results were obtained with OCUM-12 cells. Expression of thrombospondin-1 in the dnT?RII tumor or treatment with sorafenib or anti-VEGF antibody reduced tumor growth, whereas knockdown of thrombospondin-1 expression resulted in more accelerated growth of OCUM-2MLN tumors than of GFP tumors (eg, mean tumor volumes on day 14 relative to those on day 0: thrombospondin-1–knockdown tumors = 4.91 and GFP tumors = 3.79, difference = 1.12, 95% CI = 0.80 to 1.44; P < .001). Positive association between phosphorylated Smad2 and thrombospondin-1 immunostaining was observed in human gastric carcinoma tissues. Conclusions Disruption of TGF-? signaling in diffuse-type gastric carcinoma models appeared to accelerate tumor growth, apparently through increased tumor angiogenesis that was induced by decreased expression of thrombospondin-1. PMID:19351925

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

    SciTech Connect

    Aschwanden, Markus J.

    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.

  4. 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.

  5. The effect of a material growth technique on ion-implanted Mn diffusion in GaAs

    NASA Astrophysics Data System (ADS)

    Koskelo, O.; Räisänen, J.; Tuomisto, F.; Sadowski, J.; ISOLDE Collaboration

    2009-04-01

    Diffusion of ion-implanted Mn in semi-insulating (SI) and liquid encapsulated Czochralski (LEC)-grown GaAs has been determined employing the modified radiotracer technique. The effect of the growth technique and conditions on Mn diffusion in low temperature molecular beam epitaxy (LT-MBE)-grown GaAs has also been studied. Two distinct diffusion components appear in ion-implanted Mn diffusion in GaAs: slow and fast. As the diffusivity for the SI material is slightly higher than that for the LT-grown material, it is observed that the diffusivity of the fast component retards with increasing initial concentrations of Ga sublattice defects. At the same time the Mn concentration in the tail part of the diffusion profile is higher in the LT-grown material. Ga vacancy-assisted clustering of Mn is proposed as a likely reason for the observed effects.

  6. A diffusive model for halo width growth during vertical displacement events

    NASA Astrophysics Data System (ADS)

    Eidietis, N. W.; Humphreys, D. A.

    2011-07-01

    The electromagnetic loads produced by halo currents during vertical displacement events (VDEs) impose stringent requirements on the strength of ITER in-vessel components. A predictive understanding of halo current evolution is essential for ensuring the robust design of these components. A significant factor determining that evolution is the plasma resistance, which is a function of three quantities: the resistivities of the core and halo regions, and the halo region width. A diffusive model of halo width growth during VDEs has been developed, which provides one part of a physics basis for predictive halo current simulations. The diffusive model was motivated by DIII-D observations that VDEs with cold post-thermal quench plasma and a current decay time much faster than the vertical motion (type I VDE) possess much wider halo region widths than warmer plasma VDEs, where the current decay is much slower than the vertical motion (type II). A 2D finite element code is used to model the diffusion of toroidal halo current during selected type I and type II DIII-D VDEs. The model assumes a core plasma region within the last closed flux surface (LCFS) diffusing current into a halo plasma filling the vessel outside the LCFS. LCFS motion and plasma temperature are prescribed from experimental observations. The halo width evolution produced by this model compares favourably with experimental measurements of type I and type II toroidal halo current width evolution.

  7. Paclitaxel induces apoptosis and reduces proliferation by targeting epidermal growth factor receptor signaling pathway in oral cavity squamous cell carcinoma

    PubMed Central

    HU, JING; ZHANG, NA; WANG, RONGLIN; HUANG, FEI; LI, GUANG

    2015-01-01

    Oral cavity cancer is common worldwide. Furthermore, the epidermal growth factor receptor (EGFR) signaling pathway is considered to be constitutively activated in oral cancers. Paclitaxel is widely accepted as an antitumor drug as it effectively inhibits the cell cycle. This study predominantly explores the possible molecule mechanism of paclitaxel on oral cancer treatment. Cell viability was first detected using an MTT assay. Cell apoptosis was examined by Hoechst staining and flow cytometry using an annexin-V and propidium iodide kit. Specific EGFR signaling pathways were further explored through western blot analysis. Abnormal protein expression levels were determined via immunofluoresence. Additionally, the protein levels of matrix metalloproteinase (MMP)-2 and 9 were determined using ELISA. Paclitaxel significantly inhibited oral cancer cell viability in a time- and dose-dependent manner. Paclitaxel also enhanced oral cancer cell apoptosis via increased Bim and Bid protein expression. Furthermore, paclitaxel was observed to inhibit oral cancer cell proliferation through increased MMP-2 and MMP-9 protein levels. Paclitaxel inhibited the growth of the oral cancer cell line, tea8113 malignant proliferation and enhanced tea8113 cell apoptosis through inhibiting the EGFR signaling pathway.

  8. Streptococcus pneumoniae PstS production is phosphate responsive and enhanced during growth in the murine peritoneal cavity

    NASA Technical Reports Server (NTRS)

    Orihuela, C. J.; Mills, J.; Robb, C. W.; Wilson, C. J.; Watson, D. A.; Niesel, D. W.

    2001-01-01

    Differential display-PCR (DDPCR) was used to identify a Streptococcus pneumoniae gene with enhanced transcription during growth in the murine peritoneal cavity. Northern dot blot analysis and comparative densitometry confirmed a 1.8-fold increase in expression of the encoded sequence following murine peritoneal culture (MPC) versus laboratory culture or control culture (CC). Sequencing and basic local alignment search tool analysis identified the DDPCR fragment as pstS, the phosphate-binding protein of a high-affinity phosphate uptake system. PCR amplification of the complete pstS gene followed by restriction analysis and sequencing suggests a high level of conservation between strains and serotypes. Quantitative immunodot blotting using antiserum to recombinant PstS (rPstS) demonstrated an approximately twofold increase in PstS production during MPC from that during CCs, a finding consistent with the low levels of phosphate observed in the peritoneum. Moreover, immunodot blot and Northern analysis demonstrated phosphate-dependent production of PstS in six of seven strains examined. These results identify pstS expression as responsive to the MPC environment and extracellular phosphate concentrations. Presently, it remains unclear if phosphate concentrations in vivo contribute to the regulation of pstS. Finally, polyclonal antiserum to rPstS did not inhibit growth of the pneumococcus in vitro, suggesting that antibodies do not block phosphate uptake; moreover, vaccination of mice with rPstS did not protect against intraperitoneal challenge as assessed by the 50% lethal dose.

  9. 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.

  10. Effect of Bacterial Memory Dependent Growth by Using Fractional Derivatives Reaction-Diffusion Chemotactic Model

    NASA Astrophysics Data System (ADS)

    Rida, S. Z.; El-Sayed, A. M. A.; Arafa, A. A. M.

    2010-08-01

    In this paper, numerical solutions of a reaction-diffusion chemotactic model of fractional orders for bacterial growth will be present. A new solution is constructed in power series. The fractional derivatives are described in the Caputo sense. We compare the experimental result obtained with those obtained by simulation of the chemotactic model without fractional derivatives. The results show that the solution continuously depends on the time-fractional derivative. The resulting solutions spread faster than the classical solutions and may exhibit asymmetry, depending on the fractional derivative used. We present results of numerical simulations to illustrate the method, and investigate properties of numerical solutions. The Adomian's decomposition method (ADM) is used to find the approximate solution of fractional `reaction-diffusion chemotactic model. Numerical results show that the approach is easy to implement and accurate when applied to partial differential equations of fractional order.

  11. Modeling tumor growth in a complex evolving confinement using a diffuse domain approach

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    Understanding the spatiotemporal evolution of tumor growth represents an essential step towards engineering effective treatment for cancer patients. At the macroscopic scale, various biophysical models describing tumors as continuum fluids have been constructed, particularly on a Cartesian grid, where efficient numerical schemes are available to analyze the model for general tumor behaviors in a relatively unconfined space. For practical problems, however, tumors are often found in a confined sub-domain, which can even be dilated and distorted by the growing tumor within. To study such tumors, we adopt a novel diffuse domain approach that enables us to adapt a model to an evolving sub-domain and formulate the modified problem on a Cartesian grid to utilize existing numerical schemes. To demonstrate this approach, we adapt a diffuse-interface model presented in Wise et al. [2008, Three-dimensional multispecies nonlinear tumor growth - I Model and numerical method, J. Theor. Biol. 253, 524-543] to simulate lymphoma growth in a lymph node structure. Supported by NIH-PSOC grant 1U54CA143907-01.

  12. Effects of cluster diffusion on the island density and size distribution in submonolayer island growth

    E-print Network

    Yevgen A. Kryukov; Jacques G. Amar

    2011-03-13

    The effects of cluster diffusion on the submonolayer island density and island-size distribution are studied for the case of irreversible growth of compact islands on a 2D substrate. In our model, we assume instantaneous coalescence of circular islands, while the cluster mobility is assumed to exhibit power-law decay as a function of island-size with exponent mu. Results are presented for mu = 1/2, 1, and 3/2 corresponding to cluster diffusion via Brownian motion, correlated evaporation-condensation, and edge-diffusion respectively, as well as for higher values including mu = 2,3, and 6. We also compare our results with those obtained in the limit of no cluster mobility corresponding to mu = infinity. In agreement with theoretical predictions of power-law behavior of the island-size distribution (ISD) for mu islands of size s at coverage {\\theta}) up to a cross-over island-size S_c. However, the value of {\\tau} obtained in our simulations is higher than the mean-field (MF) prediction {\\tau} = (3 - mu)/2. Similarly, the value of the exponent {\\zeta} corresponding to the dependence of S_c on the average island-size S (e.g. S_c ~ S^{\\zeta}) is also significantly higher than the MF prediction {\\zeta} = 2/(mu+1). A generalized scaling form for the ISD is also proposed for mu = 1 neither the generalized scaling form nor the standard scaling form Ns({\\theta}) = {\\theta} /S^2 f(s/S) lead to scaling of the entire ISD for finite values of the ratio R of the monomer diffusion rate to deposition flux. Instead, the scaled ISD becomes more sharply peaked with increasing R and coverage. This is in contrast to models of epitaxial growth with limited cluster mobility for which good scaling occurs over a wide range of coverages.

  13. Selective area metalorganic vapor phase epitaxy growth of prism-shaped GaAs resonators for folded cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Strupiñski, W.; Mal?g, A.; Ratajczak, J.

    1998-12-01

    Selective area (SA) metalorganic vapor phase epitaxy (MOVPE) proves to be an effective method of manufacturing nonplanar structures with precisely controlled sizes and orientations of their facets. Excellent flatness of the facets makes SA MOVPE especially useful for optoelectronic applications such as microcavities. In this work we use this technique to grow prism-shaped GaAs cavities for novel prismatic (folded) cavity surface emitting laser diodes. Design of these devices has been recently proposed. Critical points in growing the cavities are: (i) to ensure 90° angle at the top of the prism, (ii) to obtain flat walls of the GaAs prism (4 ?m wide at the base) with the sharp top, (iii) to avoid an excessive number of polycrystalline precipitates on the surface of a dielectric mask (SiO 2 100 nm thick) despite the very disadvantageous ratio of openings to whole substrate area. Growth-rate calculations have been performed using total area of mask openings as an active substrate surface. For proper prism growth the pulsing epitaxy technique using Aixtron MOVPE LP system was applied, where interruption growth periods which enabled efficient surface molecules migration into openings. Optimization of the growth/interruption time versus partial pressure of gallium was essential for laser application to obtain suitable shape of the prisms. The best results for 2 ?m high prisms were obtained for 272 pulses of 2 s growth/3 s interruption, when total pressure and temperature were 100 mbar and 700°C, respectively.

  14. Growth of a diffusion flame in the field of a vortex

    NASA Technical Reports Server (NTRS)

    Marble, F. E.

    1985-01-01

    In the present study of the growth of a diffusion flame in the field of a vortex, the motion in the core is converted into a solid body rotation. The flame extension and distortion kinematics are presented, and the effect of the local flow field on local flame structure is analyzed in detail. The combustion field is found to consist of a totally reacted core region whose radius is time-dependent, and an external flame region which consists of a pair of spiral arms that extend at large radii toward their original positions on the horizontal axis. Two similarity rules are formulated which are independent of kinematic viscosity.

  15. The Lindahl equilibrium in Schumpeterian growth models: Knowledge diffusion, social value of innovations and optimal R&D

    E-print Network

    of prices that sustains the first-best social optimum in an economy with non rival goods, appears in a standard endogenous growth model with vertical innovations that explicitly exhibits knowledge diffusion". The standard literature on growth with vertical innovations generally focuses on a decentralized economy

  16. Flat-surface, step-edge, facetfacet, and facetstep diffusion barriers in growth of a Pb mesa

    E-print Network

    Simons, Jack

    atom method a b s t r a c t We obtain important energy parameters for understanding growth kinetics University of Aeronautics and Astronautics, Beijing 100083, China c Department of Materials Science 16 May 2008 Keywords: Pb mesa growth Surface diffusion barrier Surface free energy Modified embedded

  17. 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.

  18. On the anomalous fast ion energy diffusion in toroidal plasmas due to cavity modes This article has been downloaded from IOPscience. Please scroll down to see the full text article.

    E-print Network

    On the anomalous fast ion energy diffusion in toroidal plasmas due to cavity modes This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2010 Plasma Phys: 173.61.96.82 The article was downloaded on 07/04/2010 at 15:10 Please note that terms and conditions

  19. Zn Diffusion and ?-Fe(Zn) Layer Growth During Annealing of Zn-Coated B Steel

    NASA Astrophysics Data System (ADS)

    Janik, Vit; Lan, Yongjun; Beentjes, Peter; Norman, David; Hensen, Guido; Sridhar, Seetharaman

    2015-10-01

    Direct hot press forming of Zn-coated 22MnB5 steels is impeded by micro-cracks that occur in the substrate due to the presence of Zn during the forming process. A study was therefore undertaken to quantify concentration of Zn across the ?-Fe(Zn) coating and on grain boundaries in the ?-Fe(Zn) layer and the underlying ?-Fe(Zn) substrate after isothermal annealing of Zn-coated 22MnB5 at 1173 K (900 °C) and to link the Zn distribution to the amount and type of micro-cracks observed in deformed samples. Finite difference model was developed to describe Zn diffusion and the growth of the ?-Fe(Zn) layer. The penetration of Zn into the ?-Fe(Zn) substrate after 600 seconds annealing at 1173 K (900 °C) through bulk diffusion is estimated to be 3 ?m, and the diffusion depth of Zn on the ?-Fe(Zn) grain boundaries is estimated to be 6 ?m, which is significantly shorter than the maximum length (15 to 50 ?m) of the micro-cracks formed in the severely stressed conditions, indicating that the Zn diffusion into the ?-Fe(Zn) from the ?-Fe(Zn) during annealing is not correlated to the depth of micro-cracks. On the other hand, the maximum amount of Zn present in ?-Fe(Zn) layer decreases with annealing time as the layer grows and Zn oxidizes, and the amount of Zn-enriched areas inside the ?-Fe(Zn) layer is reduced leading to reduced length of cracking. Solid-Metal-Induced Embrittlement mechanism is proposed to explain the benefit of extended annealing on reduced depth of micro-crack penetration into the ?-Fe(Zn) substrate.

  20. Diffusion-controlled growth of bimineralic merwinite - diopside reaction rims between wollastonite - monticellite interfaces

    NASA Astrophysics Data System (ADS)

    Joachim, B.; Gardes, E.; Heinrich, W.; Abart, R.

    2009-04-01

    At temperatures of 800 °C to 900 °C and 1.2 GPa, monticellite and wollastonite react to form merwinite and diopside after the reaction: 2 monticellite (CaMgSiO4) + 2 wollastonite (CaSiO3) â?? merwinite (Ca3MgSi2O8) + diopside (CaMgSi2O6) We synthesized bimineralic merwinite - diopside reaction rims along the interfaces of cylindric crystals of monticellite and wollastonite. The samples were loaded in a platinum capsule and annealed at 800 °C to 900 °C and 1.2 GPa in a piston cylinder apparatus for 5 to 65 hours. Natural CaF2 was used as pressure medium and the charges were nominally dry. In all experiments, a single layer consisting of bimineralic aggregates of merwinite and diopside was produced in about equal molar amounts. Time series revealed that rim growth is parabolic, indicating that the reaction kinetics is controlled by component diffusion. SEM analysis of the microstructure showed that the original monticellite-wollastonite interface is located in the centre of the reaction rim. This implies that rim growth primarily occurred by transfer of the mobile component MgO from the rim-monticellite interface to the rim-wollastonite interface. The bulk reaction is thus divided into two half reactions occurring at the two reaction fronts. At the rim-monticellite interface the reaction is: 2 monticellite â?? 0.5 merwinite + 0.5 diopside + MgO, and at the rim-wollastonite interface, it is: 2 wollastonite + MgO â?? 0.5 merwinite + 0.5 diopside Using the model of Abart et al. (2009), the effective diffusion coefficients DMgO at 800 °C are estimated at 1.55×10-16± 2.18×10-17 m2/s, and at 900 °C at 2.46×10-16± 3.45×10-17 m2/s. This yields an activation energy of Ea= 45.6 ± 16.4 kJ/mol and a pre-exponential factor log D0 = -13.59 ± 1.26 for the Arrhenius relations to describe the temperature-dependent effective diffusivity of the MgO component in the bimineralic aggregate. IR-spectra revealed distinctive OH-contents in the nominally dry phases monticellite and wollastonite after the experiments, which had not been present in the reactants. Obviously, some hydrogen released by the natural, water-containing CaF2 pressure medium diffused into the capsule, thus producing traces of water inside. The presence of minute amounts of water may strongly enhance the kinetics of the reaction. In fact, if completely waterfree Al2O3-powder is used as pressure medium, no significant reaction occurred, and accordingly, reactants remain OH-free. An Al2O3-layer of 3 mm thickness between the capsule and the CaF2 surrounding delays the onset of rim growth for about one hour. However, once initiated, the reaction progress is the same in instantaneous and delayed reactions. References: Abart R., Petrishcheva E., Fischer F.D., Svoboda J. (2009), Thermodynamic model for diffusion controlled reaction rim growth in a binary system: application to the forsterite-enstatite-quartz system, American Journal of Science, Vol. 309, pp. 114-131

  1. Numerical approximation of oscillating Turing patterns in a reaction-diffusion model for electrochemical material growth

    NASA Astrophysics Data System (ADS)

    Sgura, Ivonne; Bozzini, Benedetto; Lacitignola, Deborah

    2012-11-01

    In this paper a reaction-diffusion system for electrochemical material growth processes is considered, including an external sinusoidal forcing term for the PDE equation describing the morphology of the electrodeposit surface profile. The numerical approximation by the Alternating Direction Implicit (ADI) method based on Extended Central Difference Formulas (ECDF) of order p = 4 in space is applied to investigate the way the variation of the frequency of the superimposed voltage sinusoid affects Turing pattern scenarios corresponding to steady state solutions of the unforced model. The ADI-ECDF method, introduced in [20] for the approximation of Turing patterns in the unforced case, is shown to be efficient from the computational point of view also to track oscillating Turing patterns for long-time simulations. In particular, the proposed method allows to identify a critical frequency range where the ripple effect arises, that is spots & worms patterns, related to the buildup of roughness in the material growth process, are suppressed and spatially homogeneous steady state solutions are attained. Such results have been validated by comparison with original experimental results on the growth of silver chloride films.

  2. Brain glioma growth model using reaction-diffusion equation with viscous stress tensor on brain MR images.

    PubMed

    Yuan, Jianjun; Liu, Lipei

    2016-02-01

    In this paper, a new reaction-diffusion model with viscous stress tensor is proposed for modeling the diffusion and invasion of brain glioma cells, which is based on the model in Yuan J.J., Liu L., Hu Q.M. Mathematical modeling of brain glioma growth using modified reaction-diffusion equation on brain MR images. Comput Biol Med 2013;43:2007-2013. The corresponding parameters are computed. The viscous stress tensor is introduced into reaction-diffusion equation, and can describe more accurately the adhesion of gliomas and normal cells. The experimental results demonstrate the effectiveness and accuracy of the proposed reaction-diffusion equation with viscous stress tensor for real brain glioma MR images. PMID:26518060

  3. 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.

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

    SciTech Connect

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

    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.

  5. Imaging growth and isocitrate dehydrogenase 1 mutation are independent predictors for diffuse low-grade gliomas

    PubMed Central

    Gozé, Catherine; Blonski, Marie; Le Maistre, Guillaume; Bauchet, Luc; Dezamis, Edouard; Page, Philippe; Varlet, Pascale; Capelle, Laurent; Devaux, Bertrand; Taillandier, Luc; Duffau, Hugues; Pallud, Johan

    2014-01-01

    Background We explored whether spontaneous imaging tumor growth (estimated by the velocity of diametric expansion) and isocitrate dehydrogenase 1 (IDH1) mutation (estimated by IDH1 immunoexpression) were independent predictors of long-term outcomes of diffuse low-grade gliomas in adults. Methods One hundred thirty-one adult patients with newly diagnosed supratentorial diffuse low-grade gliomas were retrospectively studied. Results Isocitrate dehydrogenase 1 mutations were present in 107 patients. The mean spontaneous velocity of diametric expansion was 5.40 ± 5.46 mm/y. During follow-up (mean, 70 ± 54.7 mo), 56 patients presented a malignant transformation and 23 died. The median malignant progression-free survival and the overall survival were significantly longer in cases of slow velocity of diametric expansion (149 and 198 mo, respectively) than in cases of fast velocity of diametric expansion (46 and 82 mo; P < .001 and P < .001, respectively) and in cases with IDH1 mutation (100 and 198 mo, respectively) than in cases without IDH1 mutation (72 mo and not reached; P = .028 and P = .001, respectively). In multivariate analyses, spontaneous velocity of diametric expansion and IDH1 mutation were independent prognostic factors for malignant progression-free survival (P < .001; hazard ratio, 4.23; 95% CI, 1.81–9.40 and P = .019; hazard ratio, 2.39; 95% CI, 1.19–4.66, respectively) and for overall survival (P < .001; hazard ratio, 26.3; 95% CI, 5.42–185.2 and P = .007; hazard ratio, 17.89; 95% CI, 2.15–200.1, respectively). Conclusions The spontaneous velocity of diametric expansion and IDH1 mutation status are 2 independent prognostic values that should be obtained at the beginning of the management of diffuse low-grade gliomas in adults. PMID:24847087

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

    SciTech Connect

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

    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.

  7. 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

  8. Anaplastic lymphoma kinase-positive diffuse large B-cell lymphoma presenting in nasal cavity: a case report and review of literature

    PubMed Central

    Chen, Ji; Feng, Xiaoli; Dong, Mei

    2015-01-01

    Anaplastic lymphoma kinase (ALK)-positive diffuse large B-cell lymphoma (DLBCL) is a rare subtype of non-Hodgkin’s lymphoma (NHL) with distinct morphologic and immunohistochemical features. We reported a 57-year-old female with ALK-positive DLBCL in her left nasal cavity. Histologically, the tumor cells were characterized by plasmablastic morphology and tested positive for ALK in a cytoplasmic granular staining pattern. The neoplastic cells were positive for CD38, CD4, MUM1, CD138 and Vimentin. However, they failed to express CD56, CD30, as well as mature B cells markers, such as CD79a, CD20 and T cells markers such as CD2, CD3, CD5, CD7 and CD8. The patient achieved complete response after four cycles of CHOEP (cyclophosphamide, doxorubicin, vincristine, prednisone, and etoposide) treatment. Then she received radiotherapy of the originally involved area. This case represented a rare ALK-positive DLBCL in the nasal region. PMID:25973114

  9. Diffusion-controlled garnet growth in siliceous dolomites of the Adamello contact aureole, N-Italy

    NASA Astrophysics Data System (ADS)

    Muller, T.; Fiebich, E.; Foster, C. T.

    2012-12-01

    Texture forming processes are controlled by many factors, such as material transport through polycrystalline materials, surface kinetics, fluid flow, and many others. In metamorphic rocks, texture forming processes typically involve local reactions linked to net mass transfer which allows constraining the actual reaction path in more detail. In this study, we present geochemical data combined with textural modeling to constrain the conditions and reaction mechanism during contact metamorphic garnet growth in siliceous dolomites in the southern Adamello Massif, Italy. The metamorphic garnet porphyroblasts are poikiloblastic and idiomorphic in shape with a typical grain size ranging between 0.6-1 cm in diameter sitting in a matrix of calcite+diopside+anorthite+wollastonite. Inclusions in the grossular-rich garnets are almost uniquely diopside. On the hand specimen, garnets are surrounded by visible rims of about 0.6 mm indicating a diffusion-limited reaction mechanism to be responsible for the garnet formation. In the course of this study samples have been characterized by polarization microscopy, element x-ray maps using EMPA, cathodulominescence images and stable isotope analyses of carbon and oxygen of matrix carbonates. In addition, pseudosections have been calculated using the software package PerpleX (Connolly, 2005) based on the bulk chemistry of collected samples. Results indicate that the visible margin consists of a small rim (< 1 mm) purely consisting of recrystallized calcite adjacent to the garnet edge. The major part of the observed halo, however, is characterized by the absence of anorthite and wollastonite. The observed texture of garnet porphyroblasts growing and simultaneously forming an anorthite and wollastonite free margin can successfully be reproduced using the SEG program (Foster, 1993), which assumes diffusive mass transport. Therefore the model constrains the diffusive fluxes of Ca, Mg, Al and Si by mass balance and the local Gibbs-Duhem equations on the reaction site. Assuming that the pore fluid is not saturated in CO2, which is justified for the assumption of fluid-infiltration during contact metamorphism, the model predicts the wollastonite halo to be about the same size as the anorthite halo. Interestingly, the model also predicts the small diopside-free calcite margin surrounding the garnet interface, which is also observed in the thin section of the natural sample. Taken together, we interpret the garnet growth to be the consequence of the breakdown of anorthite + wollastonite + calcite at water-rich (XCO2 < 0.2) conditions around 600 °C. Preliminary modeling results suggest that the effective relative diffusion coefficients for Si, Mg and Al are not equal producing the diopside-free calcite rim surrounding the garnet edge. Connolly, J.A.D., 2005, Computation of phase equilibria by linear programming: A tool for geodynamic modeling and its application to subduction zone decarbonation. EPSL, 236 : p. 524-541. Foster, C.T., 1993, SEG93: A program to model metamorphic textures: Geological Society of America Abstracts with Programs, v. 25, no. 6, p. A264.

  10. 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.

  11. Evolution of Plasma-Exposed Tungsten Surfaces Due to Helium Diffusion and Bubble Growth

    NASA Astrophysics Data System (ADS)

    Hammond, Karl; Hu, Lin; Maroudas, Dimitrios; Wirth, Brian; PSI-SciDAC Team

    2013-10-01

    Helium from linear plasma devices and tokamak plasmas causes the formation of microscopic features, termed ``fuzz'' or ``coral,'' on the surface of plasma-exposed materials after only a few hours of plasma exposure. The details of such surface modifications are only beginning to be understood. This study examines the initial and intermediate stages of fuzz formation by large-length-scale molecular dynamics (MD) simulations of helium-implanted tungsten over time scales of up to microseconds using single-crystalline and polycrystalline supercell models of tungsten. The large-scale MD simulations employ state-of-the-art many-body interatomic potentials and implantation depth distributions for the insertion of helium atoms into the tungsten matrix constructed based on MD simulations of helium-atom impingement onto tungsten surfaces under prescribed thermal and implantation conditions. The large-scale MD simulations reveal surface features formed via the sequence of helium implantation, diffusion of helium atoms and their aggregation to form bubbles, growth of bubbles and consequent production of tungsten self-interstitial atoms, organization of those atoms into prismatic loops, glide of those loops to the surface, and bubble rupture.

  12. The Effect of Anisotropy on the Diffusion, Nucleation and Growth of Pt on Pt(100)-hex and Pt(110) Surfaces

    NASA Astrophysics Data System (ADS)

    Besenbacher, Flemming

    1997-03-01

    By means of variable-temperature scanning tunneling microscopy, we have studied the diffusivity and the initial nucleation and growth of Pt adatoms on the reconstructed Pt(100)-hex and Pt(110)-(1x2) surfaces. For the Pt(100)-hex surface, we have performed the traditional "evaporation-quench-look" experiments. It is found that a detailed autocorrelation analysis of island positions reveals direct evidence for strongly anisotropic diffusion, and from the Pt island size distribution, which obeys a simple scaling relation, it is concluded that the mobility of the dimers is negligible. From the scaling of the island densities with deposition rate and temperature, we find that the critical island size is 1 and that surface diffusion is described by an effective barrier Ed = 0.43 eV (T.R. Linderoth, J.J. Mortensen, K.W. Jacobsen, E. Lægsgaard, I. Stensgaard, and F. Besenbacher, PRL 77, 87 (1996)). For the Pt(110) surface, on the other hand, we have been able to follow the fundamental processes underlying diffusion, nucleation and growth in real time at the atomic level (T.R. Linderoth, S. Horch, E. Lægsgaard and F. Besenbacher, to be submitted to PRL.). The Pt adatoms are confined to the troughs of the missing row reconstructed Pt(1x2) surface. In the temperature range from 270K to 370 K, the mobility of the adatoms as well as the nucleation and growth of one-dimensional islands are monitored by STM movies. The data for the diffusivity of the Pt adatoms are analyzed within the framework of a simple one-dimensional random walk model. The activation barrier for Pt adatoms is determined from an Arrhenius dependence of the hopping rate. At the highest temperatures, deviations from the simple model are observed, which can be interpreted as the onset of long jumps, i.e. jumps over several lattice spacings.

  13. Ion-assisted precursor dissociation and surface diffusion: Enabling rapid, low-temperature growth of carbon nanofibers

    SciTech Connect

    Denysenko, I.; Ostrikov, K.

    2007-06-18

    Growth kinetics of carbon nanofibers in a hydrocarbon plasma is studied. In addition to gas-phase and surface processes common to chemical vapor deposition, the model includes (unique to plasma-exposed catalyst surfaces) ion-induced dissociation of hydrocarbons, interaction of adsorbed species with incoming hydrogen atoms, and dissociation of hydrocarbon ions. It is shown that at low, nanodevice-friendly process temperatures the nanofibers grow via surface diffusion of carbon adatoms produced on the catalyst particle via ion-induced dissociation of a hydrocarbon precursor. These results explain a lower activation energy of nanofiber growth in a plasma and can be used for the synthesis of other nanoassemblies.

  14. Decomposition, diffusion, and growth rate anisotropies in self-limited profiles during metalorganic vapor-phase epitaxy of seeded nanostructures

    NASA Astrophysics Data System (ADS)

    Pelucchi, E.; Dimastrodonato, V.; Rudra, A.; Leifer, K.; Kapon, E.; Bethke, L.; Zestanakis, P. A.; Vvedensky, D. D.

    2011-05-01

    We present a model for the interplay between the fundamental phenomena responsible for the formation of nanostructures by metalorganic vapor phase epitaxy on patterned (001)/(111)B GaAs substrates. Experiments have demonstrated that V-groove quantum wires and pyramidal quantum dots form as a consequence of a self-limiting profile that develops, respectively, at the bottom of V-grooves and inverted pyramids. Our model is based on a system of reaction-diffusion equations, one for each crystallographic facet that defines the pattern, and include the group III precursors, their decomposition and diffusion kinetics (for which we discuss the experimental evidence), and the subsequent diffusion and incorporation kinetics of the group-III atoms released by the precursors. This approach can be applied to any facet configuration, including pyramidal quantum dots, but we focus on the particular case of V-groove templates and offer an explanation for the self-limited profile and the Ga segregation observed in the V-groove. The explicit inclusion of the precursor decomposition kinetics and the diffusion of the atomic species revises and generalizes the earlier work of Biasiol [Biasiol , Phys. Rev. Lett.0031-900710.1103/PhysRevLett.81.2962 81, 2962 (1998); Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.65.205306 65, 205306 (2002)] and is shown to be essential for obtaining a complete description of self-limiting growth. The solution of the system of equations yields spatially resolved adatom concentrations, from which average facet growth rates are calculated. This provides the basis for determining the conditions that yield self-limiting growth. The foregoing scenario, previously used to account for the growth modes of vicinal GaAs(001) and the step-edge profiles on the ridges of vicinal surfaces patterned with V-grooves during metalorganic vapor-phase epitaxy, can be used to describe the morphological evolution of any template composed of distinct facets.

  15. Novel instrumentation for a scattering independent measurement of the absorption coefficient of natural waters, and a new diffuse reflector for spectroscopic instrumentation and close cavity coupling 

    E-print Network

    Musser, Joseph Alan

    2007-04-25

    that the average distance a photon travels between successive reflections in an integrating cavity of arbitrary shape is four times the volume divided by the surface area, 4 V/S. Further, for a cavity which is formed by planes tangent to an inscribed sphere...

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

    SciTech Connect

    Picraux, Samuel T; Dayeh, Shadi A

    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.

  17. Diffusion suppression in vapor-liquid-solid Si nanowire growth by a barrier layer between the Au catalyst and substrate

    NASA Astrophysics Data System (ADS)

    Koto, Makoto; Watanabe, Masatoshi; Sugawa, Etsuko; Shimizu, Tomohiro; Shingubara, Shoso

    2014-10-01

    Nanowires have attracted significant interest because of their unique characteristics. Vapor-liquid-solid (VLS) growth is the standard method for fabricating nanowires and Au is the most commonly used catalyst. However, Au catalyst droplets diffuse over the Si substrate surface with a high migration velocity and agglomerate at relatively low temperatures. In our previous work, we reported a significant improvement in the positioning and diameter distribution of VLS-grown Si nanowires by inserting a diffusion barrier layer and concluded that the barrier layer suppressed the formation of AuSi eutectic droplets and prevented the droplets diffusing on the substrate surface during nucleation. In the present study, we analyzed the nucleation of the Au catalyst and examined its behavior during nucleation. Detailed multidirectional analysis and in situ observations confirmed that the formation and agglomeration of AuSi eutectic droplets was suppressed by the formation of a silicide layer. This because of the higher reaction temperatures between the diffusion barrier and the substrate silicon, and between the catalyst and the diffusion barrier, compared with the reaction between the Au catalyst and substrate silicon.

  18. Morphological instability and dynamics of fronts in bacterial growth models with nonlinear diffusion

    E-print Network

    van Saarloos, Wim

    a reaction-diffusion system with a nonlinear diffusion coefficient and find that a unique planar traveling that influences the dif- fusion of the bacteria as well as of the nutrient, and the initial nutrient concentration. For instance, the building units are bacteria that are themselves micro-organisms and thus living systems

  19. Quantitative Evaluation of Growth Plates around the Knees of Adolescent Soccer Players by Diffusion-Weighted Magnetic Resonance Imaging

    PubMed Central

    Krajnc, Zmago; Rupreht, Mitja; Drobni?, Matej

    2015-01-01

    Purpose. To quantitatively evaluate growth plates around the knees in adolescent soccer players utilizing the diffusion-weighted MR imaging (DWI). Methods. The knees and adjacent growth plates of eleven 14-year-old male soccer players were evaluated by MRI before (end of season's summer break) and after two months of intense soccer training. MRI evaluation was conducted in coronal plane by PD-FSE and DWI. All images were screened for any major pathological changes. Later, central growth plate surface area (CGPSA) was measured and the apparent diffusion coefficient (ADC) values were calculated in two most central coronal slices divided into four regions: distal femur medial (DFM), distal femur lateral (DFL), proximal tibia medial (PTM), and proximal tibia lateral (PTL). Results. No gross pathology was diagnosed on MRI. CGPSA was not significantly reduced: DFM 278 versus 272, DFL 265 versus 261, PTM 193 versus 192, and PTL 214 versus 210. ADC decrease was statistically significant only for PTM: DFM 1.27 versus 1.22, DFL 1.37 versus 1.34, PTM 1.13 versus 1.03 (p = 0.003), and PTL 1.28 versus 1.22. Conclusions. DWI measurements indicate increased cellularity in growth plates around knees in footballers most prominent in PTM after intense training. No detectable differences on a standard PD-FSE sequence were observed. PMID:26693482

  20. In situ flash X-ray observation of projectile penetration processes and crater cavity growth in porous gypsum target analogous to low-density asteroids

    NASA Astrophysics Data System (ADS)

    Yasui, Minami; Arakawa, Masahiko; Hasegawa, Sunao; Fujita, Yukihiro; Kadono, Toshihiko

    2012-11-01

    Recent studies of impact craters formed on low-density asteroids led to the proposal of a new crater formation mechanism dominated by pore collapse and compaction. Thus, it is important to study the crater formation process associated with the projectile penetration on porous cohesive targets. Laboratory impact experiments were conducted for a porous gypsum target with porosity of 50%, and flash X-rays were used to visualize the interior of the target for in situ observation of crater formation and projectile penetration. Spherical projectiles made of three different materials, stainless steel, aluminum, and nylon were impacted at 1.9-2.4 km/s (low-velocity impact) and 5.6-6.4 km/s (high-velocity impact) by using a two-stage light-gas gun. Two imaging plates were used to take two X-ray images at a different delay time from the impact moment for one shot. Two types of crater cavity shape were found on the porous gypsum target, that is, penetration holes or hemispherical cavities, depending on the projectile size and density, and the impact velocity. The drag coefficient of a projectile was determined by measuring the penetration depth changing with time, and we found that it was closely related to the crater cavity shape: it was about 0.9 for a penetration hole, while it was 2.3-3.9 for a hemispherical cavity. This large value for a hemispherical cavity could have been caused by the deformation or the disruption of the projectile. The cratering efficiency, ?tVcr(t)/mp, was found to have a power law relationship to the scaling time for crater growth, ?t = vit/rp, where vi is the impact velocity, rp is the projectile radius, and t is the time after the impact, and all data for stainless steel and aluminum projectiles merged completely and could be fitted by a power-law equation of ?tVcr(t)/mp=2.69×10-1?t1.10. Furthermore, the scaled crater volume, ?V = Vcr_final?t/mp, where Vcr_final is the final crater cavity volume, ?t is the target density, and mp is the projectile mass, was successfully fitted by a power law equation when another scaling parameter was used for the crater formation in strength regime, ?Y=Yt/?tvi2, where Yt is the target material strength, as follows: ?V=1.69×10-1?Y-0.51. As a result, the crater formed on porous gypsum was revealed to be more than one order of magnitude smaller than that formed on basalt. Based on our experimental results, which visualize how crater cavities on porous cohesive materials grow with projectile penetration, we are able to discuss compression and excavation processes during crater formation quantitatively. This observation enables us to investigate and revise numerical models and crater scaling laws for high-velocity impacts into porous cohesive materials.

  1. 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.

  2. Colony morphology of Staphylococcus aureus in serum-soft agar following in vivo and in vitro growth.

    PubMed

    Opdebeeck, J P; Watson, D L; Frost, A J

    1988-01-01

    Staphylococcus aureus isolated from cases of mastitis in ruminants were grown in vitro and in vivo and subsequently examined for expression of diffuse colony morphology in serum-soft agar. Growth in the bovine mammary gland, but not in the ovine mammary gland or ovine peritoneal cavity, resulted in subsequent expression of diffuse colony morphology. PMID:3354194

  3. Curation-Based Network Marketing: Strategies for Network Growth and Electronic Word-of-Mouth Diffusion

    ERIC Educational Resources Information Center

    Church, Earnie Mitchell, Jr.

    2013-01-01

    In the last couple of years, a new aspect of online social networking has emerged, in which the strength of social network connections is based not on social ties but mutually shared interests. This dissertation studies these "curation-based" online social networks (CBN) and their suitability for the diffusion of electronic word-of-mouth…

  4. 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.

  5. A Cahn-Hilliard model of vascularized tumor growth in a complex evolving confinement using a diffuse domain approach

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    Understanding the spatiotemporal evolution of tumor growth is essential for developing effective strategies to treat cancers. Various studies have suggested that spatial heterogeneity during tumors growth is a key factor associated with subsequent tumor invasion and the effectiveness of chemotherapy. Spatial heterogeneity may arise due to morphological instability of the tumors and the complex tissue structure surrounding the tumors. In previous works, we have used a Cahn-Hilliard tumor growth model to study the morphological instability for tumors in non-resisting tissues. However, most tumors are surrounded by complex tissue structures and confined in the capsules of some organs or between certain basement membranes. The capsules and basement membranes may be distorted by interacting with the evolving tumors, affecting the morphological instability. Here we adopt a novel diffuse domain approach to adapt our previous Cahn-Hilliard model for tumor growth in such complex evolving environments. As an example, we apply the model to simulate the evolution of lymphoma in a lymph node, incorporating also the tumor-induced angiogenesis.

  6. On a nonlocal reaction-diffusion-advection system modelling the growth of phytoplankton with cell quota structure

    NASA Astrophysics Data System (ADS)

    Hsu, Sze-Bi; Mei, Linfeng; Wang, Feng-Bin

    2015-11-01

    Phytoplankton species in a water column compete for mineral nutrients and light, and the existing models usually neglect differences in the nutrient content and the amount of light absorbed of individuals. In this current paper, we examine a size-structured and nonlocal reaction-diffusion-advection system which describes the dynamics of a single phytoplankton species in a water column where the species depends simply on light for its growth. Our model is under the assumption that the amount of light absorbed by individuals is proportional to cell size, which varies for populations that reproduce by simple division into two equally-sized daughters. We first establish the existence of a critical death rate and our analysis indicates that the phytoplankton survives if and only if its death rate is less than the critical death rate. The critical death rate depends on a general reproductive rate, the characteristics of the water column (e.g., turbulent diffusion rate, sinking, depth), cell growth, cell division, and cell size.

  7. 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.

  8. Influence of the adatom diffusion on selective growth of GaN nanowire regular arrays

    SciTech Connect

    Gotschke, T.; Schumann, T.; Limbach, F.; Calarco, R.; Stoica, T.

    2011-03-07

    Molecular beam epitaxy (MBE) on patterned Si/AlN/Si(111) substrates was used to obtain regular arrays of uniform-size GaN nanowires (NWs). The silicon top layer has been patterned with e-beam lithography, resulting in uniform arrays of holes with different diameters (d{sub h}) and periods (P). While the NW length is almost insensitive to the array parameters, the diameter increases significantly with d{sub h} and P till it saturates at P values higher than 800 nm. A diffusion induced model was used to explain the experimental results with an effective diffusion length of the adatoms on the Si, estimated to be about 400 nm.

  9. Substrate diffusion in the epitaxial growth of Ag on Pb(111) surface

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Sansalone, F. J.

    1985-11-01

    Deposition of Ag onto a Pb(111) surface was found to be strongly affected by the constant Pb diffusion from the substrate.surface. Annealing of the system at 300°C resulted in the formation of an ordered monolayer of Pb on the Ag(111) surface. LEED studies showed that the oordered Pb monolayer consisted of two types of (111) domain twisted azimuthally ˜ ±4.5° from the Ag(111) orientation.

  10. Substrate diffusion in the epitaxial growth of Ag on Pb(111) surface

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Sansalone, F. J.

    Deposition of Ag onto a Pb(111) surface was found to be strongly affected by the constant Pb diffusion from the substrate surface. Annealing of the system at 300°C resulted in the formation of an ordered monolayer of Pb on the Ag(111) surface. LEED studies showed that the ordered Pb monolayer consisted of two types of (111) domain twisted azimuthally ˜±4.5° from the Ag(111) orientation.

  11. GaN Selective Area Metal-Organic Vapor Phase Epitaxy: Prediction of Growth Rate Enhancement by Vapor Phase Diffusion Model

    NASA Astrophysics Data System (ADS)

    Shioda, Tomonari; Tomita, Yuki; Sugiyama, Masakazu; Shimogaki, Yukihiro; Nakano, Yoshiaki

    2007-11-01

    Thickness profiles of GaN grown by selective area metal-organic vapor phase epitaxy (SA-MOVPE) were successfully reproduced by a vapor phase diffusion model that employs only one parameter—effective diffusion length D/ks. The value of D/ks of Ga-containing precursors changes from 10 to 50 ?m under growth temperature of 1000-1250 °C and reactor total pressure of 100 mbar. It was confirmed that, in the wide-stripe SA-MOVPE of GaN, the vapor phase diffusion of Ga-containing precursors govern the profile of growth rate. Numerical simulation using the vapor phase diffusion model is of great help for the design and control of thickness profiles in the SA-MOVPE of GaN.

  12. Roles of aromatic side chains and template effects of the hydrophobic cavity of a self-assembled peptide nanoarchitecture for anisotropic growth of gold nanocrystals.

    PubMed

    Tomizaki, Kin-Ya; Kishioka, Kohei; Kobayashi, Hiroki; Kobayashi, Akitsugu; Yamada, Naoki; Kataoka, Shunsuke; Imai, Takahito; Kasuno, Megumi

    2015-11-15

    Gold nanocrystals are promising as catalysts and for use in sensing/imaging systems, photonic/plasmonic devices, electronics, drug delivery systems, and for photothermal therapy due to their unique physical, chemical, and biocompatible properties. The use of various organic templates allows control of the size, shape, structure, surface modification and topology of gold nanocrystals; in particular, currently the synthesis of gold nanorods requires a cytotoxic surfactant to control morphology. To control the shape of gold nanocrystals, we previously demonstrated the de novo design and synthesis of a ?-sheet-forming nonapeptide (RU006: Ac-AIAKAXKIA-NH2, X=l-2-naphthylalanine, Nal) and the fabrication of gold nanocrystals by mixing RU006 and HAuCl4 in water. The reaction afforded ultrathin gold nanoribbons 50-100nm wide, several nanometers high, and microns long. To understand the mechanism underlying gold nanoribbon formation by the RU006 system, we here report (i) the effects of replacement of the Nal aromatic side chain in the RU006 sequence with other aromatic moieties, (ii) the electrochemical properties of aromatic side chains in the de novo designed template peptides to estimate the redox potential and number of electrons participating in the gold crystallization process, and (iii) the stoichiometry of the RU006 system for gold nanoribbon synthesis. Interestingly, RU006 bearing a naphthalene moiety (oxidation peak potential of 1.50V vs Ag/Ag(+)) and an analog [Ant(6)]-RU006 bearing a bulky anthracene moiety (oxidation peak potential of 1.05V vs Ag/Ag(+)) allowed the growth of anisotropic (ribbon-like) and isotropic (round) gold nanocrystals, respectively. This trend in morphology of gold nanocrystals was attributed to spatially-arranged hydrophobic cavities sufficiently large to accommodate the gold precursor and to allow directed crystal growth driven by cross-linking reactions among the naphthalene rings. Support for this mechanism was obtained by decreasing the mole fraction of [Ant(6)]-RU006 against the total concentration of [Ant(6)]-RU006 and [Phe(6)]-RU006: absorption spectra similar to that for RU006 were obtained. Differences in the redox properties of the anthracene and naphthalene moieties scarcely affected morphology. We propose that construction of an appropriate hydrophobic cavity is important for templating gold nanocrystal architectures by peptide self-assembly. This mechanism would be applicable for developing simple, low toxicity, mild synthetic methods for constructing metallic nanomaterials for therapeutic use. PMID:26521037

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

    NASA Astrophysics Data System (ADS)

    Ódor, Géza; Liedke, Bartosz; Heinig, Karl-Heinz

    2010-03-01

    We show that d+1 -dimensional surface growth models can be mapped onto driven lattice gases of d -mers. The continuous surface 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 with field theoretical predictions of the Kardar-Parisi-Zhang universality class and numerical results. We show that the (2+1) -dimensional exponents conciliate with the values suggested by Lässig within error margin, for the largest system sizes studied here, but we cannot support his predictions for (3+1)d numerically.

  14. 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

  15. 850-nm Zn-diffusion vertical-cavity surface-emitting lasers with with oxide-relief structure for high-speed and energy-efficient optical interconnects from very-short to medium (2km) reaches

    NASA Astrophysics Data System (ADS)

    Shi, Jin-Wei; Wei, Chia-Chien; Chen, Jason (Jyehong); Yang, Ying-Jay

    2015-03-01

    High-speed and "green" ~850 nm vertical-cavity surface-emitting lasers (VCSELs) have lately attracted lots of attention due to their suitability for applications in optical interconnects (OIs). To further enhance the speed and its maximum allowable linking distance of VCSELs are two major trends to meet the requirement of OI in next generation data centers. Recently, by use of the advanced 850 nm VCSEL technique, data rate as high as 64 Gbit/sec over 57m and 20 Gbit/sec over 2km MMF transmission have been demonstrated, respectively. Here, we will review our recent work about 850 nm Zn-diffusion VCSELs with oxide-relief apertures to further enhance the above-mentioned performances. By using Zn-diffusion, we can not only reduce the device resistance but also manipulate the number of optical modes to benefit transmission. Combing such device, which has excellent single-mode (SMSR >30 dB) and high-power (~7mW) performance, with advanced modulation format (OFDM), record-high bit-rate-distance-product through MMF (2.3 km×28 Gbit/sec) has been demonstrated. Furthermore, by selective etching away the oxide aperture inside Zn-diffusion VCSEL, significant enhancement of device speed, D-factor, and reliability can be observed. With such unique VCSEL structure, >40 Gbit/sec energy-efficient transmission over 100m MMF under extremely low-driving current density (<10kA/cm2) has been successfully demonstrated.

  16. 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.

  17. 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…

  18. A diffusion process to model generalized von Bertalanffy growth patterns: fitting to real data.

    PubMed

    Román-Román, Patricia; Romero, Desirée; Torres-Ruiz, Francisco

    2010-03-01

    The von Bertalanffy growth curve has been commonly used for modeling animal growth (particularly fish). Both deterministic and stochastic models exist in association with this curve, the latter allowing for the inclusion of fluctuations or disturbances that might exist in the system under consideration which are not always quantifiable or may even be unknown. This curve is mainly used for modeling the length variable whereas a generalized version, including a new parameter b > or = 1, allows for modeling both length and weight for some animal species in both isometric (b = 3) and allometric (b not = 3) situations. In this paper a stochastic model related to the generalized von Bertalanffy growth curve is proposed. This model allows to investigate the time evolution of growth variables associated both with individual behaviors and mean population behavior. Also, with the purpose of fitting the above-mentioned model to real data and so be able to forecast and analyze particular characteristics, we study the maximum likelihood estimation of the parameters of the model. In addition, and regarding the numerical problems posed by solving the likelihood equations, a strategy is developed for obtaining initial solutions for the usual numerical procedures. Such strategy is validated by means of simulated examples. Finally, an application to real data of mean weight of swordfish is presented. PMID:20018193

  19. Growth and properties of AlGaInP resonant cavity light emitting diodes on Ge/SiGe/Si substrates

    SciTech Connect

    Kwon, O.; Boeckl, J.; Lee, M.L.; Pitera, A.J.; Fitzgerald, E.A.; Ringel, S.A.

    2005-02-01

    Visible AlGaInP resonant cavity light emitting diodes (RCLEDs) were grown by molecular beam epitaxy and fabricated on low-dislocation density, SiGe/Si metamorphic substrates. A comparison with identical devices grown on GaAs and Ge substrates shows that not only did the RCLED device structure successfully transfer to the SiGe/Si substrate, but also a higher optical output power was obtained. This result is attributed to enhanced lateral current spreading by the low residual dislocation density ({approx}1x10{sup 6} cm{sup -2}) network within the virtual Ge substrate and the superior thermal conductivity of the underlying Si wafer. In addition, the growth of an AlGaAs current spreading layer and a modified top metal contact were incorporated in the RCLED on SiGe to optimize device performance. The measured electroluminescent output power was 166 {mu}W at a 665 nm peak wavelength under 500 mA current injection. Extremely narrow electroluminescence linewidths were achieved with a full width half maximum value of 3.63 nm under 50 mA current injection. These results demonstrate great promise for the monolithic integration of visible band optical sources with Si-based electronic circuitry.

  20. Neonatal Neurobehavior and Diffusion MRI Changes in Brain Reorganization Due to Intrauterine Growth Restriction in a Rabbit Model

    PubMed Central

    Eixarch, Elisenda; Batalle, Dafnis; Illa, Miriam; Muñoz-Moreno, Emma; Arbat-Plana, Ariadna; Amat-Roldan, Ivan; Figueras, Francesc; Gratacos, Eduard

    2012-01-01

    Background Intrauterine growth restriction (IUGR) affects 5–10% of all newborns and is associated with a high risk of abnormal neurodevelopment. The timing and patterns of brain reorganization underlying IUGR are poorly documented. We developed a rabbit model of IUGR allowing neonatal neurobehavioral assessment and high resolution brain diffusion magnetic resonance imaging (MRI). The aim of the study was to describe the pattern and functional correlates of fetal brain reorganization induced by IUGR. Methodology/Principal Findings IUGR was induced in 10 New Zealand fetal rabbits by ligation of 40–50% of uteroplacental vessels in one horn at 25 days of gestation. Ten contralateral horn fetuses were used as controls. Cesarean section was performed at 30 days (term 31 days). At postnatal day +1, neonates were assessed by validated neurobehavioral tests including evaluation of tone, spontaneous locomotion, reflex motor activity, motor responses to olfactory stimuli, and coordination of suck and swallow. Subsequently, brains were collected and fixed and MRI was performed using a high resolution acquisition scheme. Global and regional (manual delineation and voxel based analysis) diffusion tensor imaging parameters were analyzed. IUGR was associated with significantly poorer neurobehavioral performance in most domains. Voxel based analysis revealed fractional anisotropy (FA) differences in multiple brain regions of gray and white matter, including frontal, insular, occipital and temporal cortex, hippocampus, putamen, thalamus, claustrum, medial septal nucleus, anterior commissure, internal capsule, fimbria of hippocampus, medial lemniscus and olfactory tract. Regional FA changes were correlated with poorer outcome in neurobehavioral tests. Conclusions IUGR is associated with a complex pattern of brain reorganization already at birth, which may open opportunities for early intervention. Diffusion MRI can offer suitable imaging biomarkers to characterize and monitor brain reorganization due to fetal diseases. PMID:22347486

  1. Study of coupled double diffusive convection-radiation in a tilted cavity via a hybrid multi-relaxation time-lattice Boltzmann-finite difference and discrete ordinate methods

    NASA Astrophysics Data System (ADS)

    Moufekkir, Fayçal; Moussaoui, Mohammed Amine; Mezrhab, Ahmed; Naji, Hassan

    2014-09-01

    The coupled double diffusive natural convection and radiation in a tilted and differentially heated square cavity containing a non-gray air-CO2 (or air-H2O) mixtures was numerically investigated. The horizontal walls are insulated and impermeable and the vertical walls are maintained at different temperatures and concentrations. The hybrid lattice Boltzmann method with the multiple-relaxation time model is used to compute the hydrodynamics and the finite difference method to determine temperatures and concentrations. The discrete ordinates method combined to the spectral line-based weighted sum of gray gases model is used to compute the radiative term and its spectral aspect. The effects of the inclination angle on the flow, thermal and concentration fields are analyzed for both aiding and opposing cases. It was found that radiation gas modifies the structure of the velocity and thermal fields by generating inclined stratifications and promoting the instabilities in opposing flows.

  2. Study of coupled double diffusive convection-radiation in a tilted cavity via a hybrid multi-relaxation time-lattice Boltzmann-finite difference and discrete ordinate methods

    NASA Astrophysics Data System (ADS)

    Moufekkir, Fayçal; Moussaoui, Mohammed Amine; Mezrhab, Ahmed; Naji, Hassan

    2015-04-01

    The coupled double diffusive natural convection and radiation in a tilted and differentially heated square cavity containing a non-gray air-CO2 (or air-H2O) mixtures was numerically investigated. The horizontal walls are insulated and impermeable and the vertical walls are maintained at different temperatures and concentrations. The hybrid lattice Boltzmann method with the multiple-relaxation time model is used to compute the hydrodynamics and the finite difference method to determine temperatures and concentrations. The discrete ordinates method combined to the spectral line-based weighted sum of gray gases model is used to compute the radiative term and its spectral aspect. The effects of the inclination angle on the flow, thermal and concentration fields are analyzed for both aiding and opposing cases. It was found that radiation gas modifies the structure of the velocity and thermal fields by generating inclined stratifications and promoting the instabilities in opposing flows.

  3. Dental cavities

    MedlinePLUS

    ... Minimize snacking, which creates a constant supply of acid in the mouth. Avoid constant sipping of sugary drinks or frequent sucking on candy and mints. Dental sealants can prevent some cavities. ...

  4. A reaction-diffusion-advection model of harmful algae growth with toxin degradation

    NASA Astrophysics Data System (ADS)

    Wang, Feng-Bin; Hsu, Sze-Bi; Zhao, Xiao-Qiang

    2015-10-01

    This paper is devoted to the study of a reaction-diffusion-advection system modeling the dynamics of a single nutrient, harmful algae and algal toxin in a flowing water habitat with a hydraulic storage zone. We introduce the basic reproduction ratio R0 for algae and show that R0 serves as a threshold value for persistence and extinction of the algae. More precisely, we prove that the washout steady state is globally attractive if R0 < 1, while there exists a positive steady state and the algae is uniformly persistent if R0 > 1. With an additional assumption, we obtain the uniqueness and global attractivity of the positive steady state in the case where R0 > 1.

  5. Diffusion controlled autocatalytic growth of revert periodic precipitation of cadmium sulphide in lyophillic colloid

    NASA Astrophysics Data System (ADS)

    Palaniandavar, N.; Gnanam, F. D.; Ramasamy, P.

    1984-04-01

    The experimental conditions for revert and direct periodic precipitation of cadmium sulphide in lyophillic colloid have been investigated. The theoretically derived Mathur's spacing law, which suits both revert and direct types of precipitation has been experimentally verified. An attempt has been made to explain the formation of revert cadmium sulphide bands by considering preferential adsorption of sulphide ion, interpenetrating distribution of ions, and autocatalytic growth of cadmium sulphide particles within the electrical double layer. The flocculation is explained as being due to the specific adsorption of the hydrolyzed counter ion. The increase and decrease in the value of velocity constant is explained on the basis of the formation of autocomplex species.

  6. Inhibition of COP9-signalosome (CSN) deneddylating activity and tumor growth of diffuse large B-cell lymphomas by doxycycline

    PubMed Central

    Pulvino, Mary; Chen, Luojing; Oleksyn, David; Li, Jing; Compitello, George; Rossi, Randy; Spence, Stephen; Balakrishnan, Vijaya; Jordan, Craig; Poligone, Brian; Casulo, Carla; Burack, Richard; Shapiro, Joel L.; Bernstein, Steven; Friedberg, Jonathan W.; Deshaies, Raymond J.; Land, Hartmut; Zhao, Jiyong

    2015-01-01

    In searching for small-molecule compounds that inhibit proliferation and survival of diffuse large B-cell lymphoma (DLBCL) cells and may, therefore, be exploited as potential therapeutic agents for this disease, we identified the commonly used and well-tolerated antibiotic doxycycline as a strong candidate. Here, we demonstrate that doxycycline inhibits the growth of DLBCL cells both in vitro and in mouse xenograft models. In addition, we show that doxycycline accumulates in DLBCL cells to high concentrations and affects multiple signaling pathways that are crucial for lymphomagenesis. Our data reveal the deneddylating activity of COP-9 signalosome (CSN) as a novel target of doxycycline and suggest that doxycycline may exert its effects in DLBCL cells in part through a CSN5-HSP90 pathway. Consistently, knockdown of CSN5 exhibited similar effects as doxycycline treatment on DLBCL cell survival and HSP90 chaperone function. In addition to DLBCL cells, doxycycline inhibited growth of several other types of non-Hodgkin lymphoma cells in vitro. Together, our results suggest that doxycycline may represent a promising therapeutic agent for DLBCL and other non-Hodgkin lymphomas subtypes. PMID:26142707

  7. From Impurity Doping to Metallic Growth in Diffusion Doping: Properties and Structure of Silver-Doped InAs Nanocrystals.

    PubMed

    Amit, Yorai; Li, Yuanyuan; Frenkel, Anatoly I; Banin, Uri

    2015-11-24

    Tuning of the electronic properties of presynthesized colloidal semiconductor nanocrystals (NCs) by doping plays a key role in the prospect of implementing them in printed electronics devices such as transistors and photodetectors. While such impurity doping reactions have already been introduced, the understanding of the doping process, the nature of interaction between the impurity and host atoms, and the conditions affecting the solubility limit of impurities in nanocrystals are still unclear. Here, we used a postsynthesis diffusion-based doping reaction to introduce Ag impurities into InAs NCs. Optical absorption spectroscopy and analytical inductively coupled plasma mass spectroscopy (ICP-MS) were used to present a two-stage doping model consisting of a "doping region" and a "growth region", depending on the impurity to NC ratio in the reaction vessel. X-ray absorption fine-structure (XAFS) spectroscopy was employed to determine the impurity location and correlate between the structural and electronic properties for different sizes of InAs NCs and dopant concentrations. The resulting structural model describes a heterogeneous system where the impurities initially dope the NC, by substituting for In atoms near the surface of the NC, until the "solubility limit" is reached, after which the rapid growth and formation of metallic structures are identified. PMID:26390173

  8. Modeling growth and dissemination of lymphoma in a co-evolving lymph node: a diffuse-domain approach

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    While partial differential equation models of tumor growth have successfully described various spatiotemporal phenomena observed for in-vitro tumor spheroid experiments, one challenge towards taking these models to further study in-vivo tumors is that instead of relatively static tissue culture with regular boundary conditions, in-vivo tumors are often confined in organ tissues that co-evolve with the tumor growth. Here we adopt a recently developed diffuse-domain method to account for the co-evolving domain boundaries, adapting our previous in-vitro tumor model for the development of lymphoma encapsulated in a lymph node, which may swell or shrink due to proliferation and dissemination of lymphoma cells and treatment by chemotherapy. We use the model to study the induced spatial heterogeneity, which may arise as an emerging phenomenon in experimental observations and model analysis. Spatial heterogeneity is believed to lead to tumor infiltration patterns and reduce the efficacy of chemotherapy, leaving residuals that cause cancer relapse after the treatment. Understanding the spatiotemporal evolution of in-vivo tumors can be an essential step towards more effective strategies of curing cancer. Supported by NIH-PSOC grant 1U54CA143907-01.

  9. 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.

  10. Suppression of CD300A inhibits the growth of diffuse large B-cell lymphoma.

    PubMed

    Jiang, Lei; Xu, Yulian; Zeng, Xinli; Fang, Jianchen; Morse, Herbert C; Zhou, Jeff X

    2015-10-13

    CD300A is a type I transmembrane receptor protein which has shown inhibitory effects on B-cell receptor-mediated signals. In an analysis of public dataset, we found that CD300A mRNA levels were inversely correlated with the overall survival time of patients with diffuse large B-cell lymphoma (DLBCL). To decipher the role of CD300A in DLBCL, we knocked down the expression levels of CD300A in DLBCL cells and found that decreasing levels of CD300A significantly inhibited cell proliferation of OCI-Ly01, Farage, and SUDHL-4 cells, but not of VAL, OCI-Ly10, or SUDHL-8 cells. Mechanistically, reduced expression of CD300A resulted in a marked attenuation of AKT phosphorylation, a key molecular event in tumorigenesis, in OCI-Ly01, Farage, and SUDHL-4 cells. Pharmacologic inhibition of PI3K displayed a similar inhibitory effect on cell proliferation. Furthermore, using a xenograft animal model, we found that decreasing levels of CD300A in OCI-Ly01 and Farage cells significantly inhibited tumor formation in vivo. Collectively, our results suggested an oncogenic role of CD300A in DLBCL which could serve as a potential biomarker and therapeutic target for this malignant disease. PMID:26435477

  11. 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.

  12. Interface proliferation and the growth of labyrinths in a reaction-diffusion system

    SciTech Connect

    Goldstein, R.E.; Muraki, D.J.; Petrich, D.M.

    1996-04-01

    In the bistable regime of the FitzHugh-Nagumo model of reaction-diffusion systems, spatially homogeneous patterns may be nonlinearly unstable to the formation of compact {open_quote}{open_quote}localized states.{close_quote}{close_quote} The formation of space-filling patterns from instabilities of such structures in the context of a nonlocal contour dynamics model for the evolution of boundaries between high and low concentrations of the activator. An earlier heuristic derivation [D. M. Petrich and R. E. Goldstein, Phys. Rev. Lett. {bold 72}, 1120 (1994)] is made more systematic by an asymptotic analysis appropriate to the limits of fast inhibition, sharp activator interfaces, and small asymmetry in the bistable minima. The resulting contour dynamics is temporally local, with the normal component of the velocity involving a local contribution linear in the interface curvature and a nonlocal component having the form of a screened Biot-Savart interaction. The amplitude of the nonlocal interaction is set by the activator-inhibitor coupling and controls the {open_quote}{open_quote}lateral inhibition{close_quote}{close_quote} responsible for the destabilization of localized structures such as spots and stripes, and the repulsion of nearby interfaces in the later stages of those instabilities. The phenomenology of pattern formation exhibited by the contour dynamics is consistent with that seen by Lee, McCormick, Ouyang, and Swinney in experiments on the iodide-ferrocyanide-sulfite reaction in a gel reactor. Extensive numerical studies of the underlying partial differential equations are presented and compared in detail with the contour dynamics. The similarity of these phenomena (and their mathematical description) with those observed in amphiphilic monolayers, type I superconductors in the intermediate state, and magnetic fluids in Hele-Shaw geometry are emphasized. {copyright} {ital 1996 The American Physical Society.}

  13. Unified Heat Kernel Regression for Diffusion, Kernel Smoothing and Wavelets on Manifolds and Its Application to Mandible Growth Modeling in CT Images

    PubMed Central

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

    2014-01-01

    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 regression is mathematically equivalent to isotropic heat diffusion, kernel smoothing and recently popular diffusion wavelets. Unlike many previous partial differential equation based approaches involving diffusion, our approach represents the solution of diffusion analytically, reducing numerical inaccuracy and slow convergence. The numerical implementation is validated on a unit sphere using spherical harmonics. As an illustration, we have applied the method in characterizing the localized growth pattern of mandible surfaces obtained in CT images from subjects between ages 0 and 20 years by regressing the length of displacement vectors with respect to the template surface. PMID:25791435

  14. Neuroblastoma-targeted nanocarriers improve drug delivery and penetration, delay tumor growth and abrogate metastatic diffusion.

    PubMed

    Cossu, Irene; Bottoni, Gianluca; Loi, Monica; Emionite, Laura; Bartolini, Alice; Di Paolo, Daniela; Brignole, Chiara; Piaggio, Francesca; Perri, Patrizia; Sacchi, Angelina; Curnis, Flavio; Gagliani, Maria Cristina; Bruno, Silvia; Marini, Cecilia; Gori, Alessandro; Longhi, Renato; Murgia, Daniele; Sementa, Angela Rita; Cilli, Michele; Tacchetti, Carlo; Corti, Angelo; Sambuceti, Gianmario; Marchiò, Serena; Ponzoni, Mirco; Pastorino, Fabio

    2015-11-01

    Selective tumor targeting is expected to enhance drug delivery and to decrease toxicity, resulting in an improved therapeutic index. We have recently identified the HSYWLRS peptide sequence as a specific ligand for aggressive neuroblastoma, a childhood tumor mostly refractory to current therapies. Here we validated the specific binding of HSYWLRS to neuroblastoma cell suspensions obtained either from cell lines, animal models, or Schwannian-stroma poor, stage IV neuroblastoma patients. Binding of the biotinylated peptide and of HSYWLRS-functionalized fluorescent quantum dots or liposomal nanoparticles was dose-dependent and inhibited by an excess of free peptide. In animal models obtained by the orthotopic implant of either MYCN-amplified or MYCN single copy human neuroblastoma cell lines, treatment with HSYWLRS-targeted, doxorubicin-loaded Stealth Liposomes increased tumor vascular permeability and perfusion, enhancing tumor penetration of the drug. This formulation proved to exert a potent antitumor efficacy, as evaluated by bioluminescence imaging and micro-PET, leading to (i) delay of tumor growth paralleled by decreased tumor glucose consumption, and (ii) abrogation of metastatic spreading, accompanied by absence of systemic toxicity and significant increase in the animal life span. Our findings are functional to the design of targeted nanocarriers with potentiated therapeutic efficacy towards the clinical translation. PMID:26276694

  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. Pump cavities for compact pulsed Nd:YAG lasers: a comparative study

    SciTech Connect

    Docchio, F.; Pallaro, L.; Svelto, O.

    1985-11-15

    Two elliptical cavities of different dimensions and eccentricity, one close-coupled diffusive cavity and one close-coupled reflecting cavity of our design, have been studied as a function of the type and geometry of the pumping cavity. A high efficiency is obtained with the two elliptical cavities, while a more uniform beam distribution is obtained with the two close-coupled cavities. The close-coupled reflective cavity gives comparable efficiency with respect to the diffusive type but a superior beam quality.

  17. Synchronization in an optomechanical cavity

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

  18. CRAB Cavity in CERN SPS

    SciTech Connect

    Kim, H.J.; Sen, T.

    2010-05-01

    Beam collisions with a crossing angle at the interaction point are often necessary in colliders to reduce the effects of parasitic collisions which induce emittance growth and decrease beam lifetime. The crossing angle reduces the geometrical overlap of the beams and hence the luminosity. Crab cavity offer a promising way to compensate the crossing angle and to realize effective head-on collisions. Moreover, the crab crossing mitigates the synchro-betatron resonances due to the crossing angle. A crab cavity experiment in SPS is proposed as a proof of principle before deciding on a full crab-cavity implementation in the LHC. In this paper, we investigate the effects of a single crab cavity on beam dynamics in the SPS and life time.

  19. Speeding of spherulitic growth rate at the late stage of isothermal crystallization due to interfacial diffusion for double-layer semicrystalline polymer films.

    PubMed

    Zhang, Yaqiong; Jiang, Feng; Wang, Wentao; Wang, Zhigang

    2014-07-31

    In this study a unique phenomenon has been found for isothermal crystallization of double-layer semicrystalline polymer films. It is surprisingly found that there exists a speeding of poly(l-lactic acid) (PLA) spherulitic growth rate for poly(ethylene oxide)/poly(l-lactic acid) (PEO/PLA) double-layer films at the late stage of isothermal crystallization, which does not exist for PLA/PEO blend films and neat PLA films. The mutual diffusion between PEO and PLA layers plays the key factor to bring out the observed speeding of spherulitic growth rate. This type of study provides an avenue for understanding the interplay between polymer crystallization and interfacial diffusion in multilayer polymer films, which is not available when employing the polymer blend films. PMID:25052564

  20. Incorporating crystal growth, non-isothermal diffusion, and melt evolution in models for obtaining time scales of magmatic processes from chemical zoning in minerals

    NASA Astrophysics Data System (ADS)

    Costa, F.; Dohmen, R.; Chakraborty, S.

    2008-12-01

    Chemical zoning of crystals is a major archive of information that allows the reconstruction of processes that occur in magma reservoirs and conduits. Detailed analyses of such zoning and application of principles of chemical diffusion allows the determination of the durations and rates of many magmatic processes. Most determinations of timescales in igneous petrology have used relatively simple models where isothermal diffusion with constant boundary conditions was considered. Although these may apply in volcanic rocks and in some situations, petrological and geochemical studies of crystal zoning in many cases indicate more complex polythermal histories with changes in composition. Such changes are, for example, characteristic of plutonic environments. Changes of temperature with time affect the values of diffusion coefficient and crystal/melt equilibrium relations. Changes of liquid composition affect the equilibration times by modifying the driving forces at the crystal-liquid interface. It is not straightforward to quantify to what extent the simple models described above capture the essence of such complex processes in nature. To address this gap in knowledge, we have carried out a series of numerical calculations to explore the types of zoning patterns that develop, and the ranges of time scales that are retrieved, when models with more sophisticated and realistic conditions are considered. Our models include: (i) a thermal history with cooling and/or heating pulses, (ii) changes in the melt composition and crystal/melt equilibrium along given P-T- fO2-fH2O paths, as calculated by minimizing total free energy of a system (MELTS Software, Ghiorso and Sack, 1995), and (iii) crystal growth at various rates. We have calculated the major (Fe, Mg) as well as trace element (Ca, Ni, Mn) zoning profiles that develop in olivine crystals in a fractionating basaltic liquid subject to the above conditions. Diffusion is allowed to simultaneously modify the compositional gradients. We find that zoning patterns produced by growth + diffusion are distinct from those produced by diffusion alone in many cases. This distinction becomes more apparent when multiple elements with different diffusion rates and geochemical affinities are considered simultaneously. For growth rates between 10-8 to 10-10 cms-1, a diffusion-only model overestimates the duration of a thermal event by about a factor of two (for a crystal size of 500 mm radius), and inconsistent time scales are obtained when different elements from the same crystal are used to calculate timescales. For growth rates <10-10 cms-1, diffusion-only models yield realistic results. Timescales calculated from isothermal, diffusion-only, and constant boundary models are a good first order approximation for durations of magmatic processes in volcanic rocks. Modelling the zoning patterns of crystals from plutonic environments require more complex models. Aside from a protracted cooling history, the equilibration of the zoning involves significant changes in the evolution of crystal/melt or crystal/matrix equilibria and diffusion in the matrix. Ghiorso M. and Sack R. (1995). Contrib Mineral Petrol 119:197-212.

  1. Modelling non-homogeneous stochastic reaction-diffusion systems: the case study of gemcitabine-treated non-small cell lung cancer growth

    PubMed Central

    2012-01-01

    Background Reaction-diffusion based models have been widely used in the literature for modeling the growth of solid tumors. Many of the current models treat both diffusion/consumption of nutrients and cell proliferation. The majority of these models use classical transport/mass conservation equations for describing the distribution of molecular species in tumor spheroids, and the Fick's law for describing the flux of uncharged molecules (i.e oxygen, glucose). Commonly, the equations for the cell movement and proliferation are first order differential equations describing the rate of change of the velocity of the cells with respect to the spatial coordinates as a function of the nutrient's gradient. Several modifications of these equations have been developed in the last decade to explicitly indicate that the tumor includes cells, interstitial fluids and extracellular matrix: these variants provided a model of tumor as a multiphase material with these as the different phases. Most of the current reaction-diffusion tumor models are deterministic and do not model the diffusion as a local state-dependent process in a non-homogeneous medium at the micro- and meso-scale of the intra- and inter-cellular processes, respectively. Furthermore, a stochastic reaction-diffusion model in which diffusive transport of the molecular species of nutrients and chemotherapy drugs as well as the interactions of the tumor cells with these species is a novel approach. The application of this approach to he scase of non-small cell lung cancer treated with gemcitabine is also novel. Methods We present a stochastic reaction-diffusion model of non-small cell lung cancer growth in the specification formalism of the tool Redi, we recently developed for simulating reaction-diffusion systems. We also describe how a spatial gradient of nutrients and oncological drugs affects the tumor progression. Our model is based on a generalization of the Fick's first diffusion law that allows to model diffusive transport in non-homogeneous media. The diffusion coefficient is explicitly expressed as a function depending on the local conditions of the medium, such as the concentration of molecular species, the viscosity of the medium and the temperature. We incorporated this generalized law in a reaction-based stochastic simulation framework implementing an efficient version of Gillespie algorithm for modeling the dynamics of the interactions between tumor cell, nutrients and gemcitabine in a spatial domain expressing a nutrient and drug concentration gradient. Results Using the mathematical framework of model we simulated the spatial growth of a 2D spheroidal tumor model in response to a treatment with gemcitabine and a dynamic gradient of oxygen and glucose. The parameters of the model have been taken from recet literature and also inferred from real tumor shrinkage curves measured in patients suffering from non-small cell lung cancer. The simulations qualitatively reproduce the time evolution of the morphologies of these tumors as well as the morphological patterns follow the growth curves observed in patients. Conclusions s This model is able to reproduce the observed increment/decrement of tumor size in response to the pharmacological treatment with gemcitabine. The formal specification of the model in Redi can be easily extended in an incremental way to include other relevant biophysical processes, such as local extracellular matrix remodelling, active cell migration and traction, and reshaping of host tissue vasculature, in order to be even more relevant to support the experimental investigation of cancer. PMID:23095709

  2. What's a Cavity?

    MedlinePLUS

    ... How the Body Works Main Page What's a Cavity? KidsHealth > Kids > Q&A > Q&A > What's a ... while you're getting your new filling. Continue Cavity Prevention Tips Though cavities can be repaired, try ...

  3. 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

    as the interfacial silicon oxide growth rates were examined as a function of time, temperature, film stoichiometry of work that addresses issues pertaining to interface preparation and characterization.7,8,11­13 Although during growth. The deposition of high- oxides on silicon are often accompanied by the growth

  4. Spectroscopic evaluation of photodynamic therapy of the intraperitoneal cavity

    NASA Astrophysics Data System (ADS)

    Finlay, Jarod C.; Sandell, Julia L.; Zhu, Timothy C.; Lewis, Robert; Cengel, Keith A.; Hahn, Stephen M.

    2010-02-01

    We present the results of spectroscopic measurements of diffuse reflectance and fluorescence before and after photodynamic therapy of healthy canine peritoneal cavity. Animals were treated intra-operatively after iv injection of the benzoporphyrin derivative (BPD). The small bowel was treated using a uniform light field projected by a microlens-tipped fiber. The cavity was then filled with scattering medium and the remaining organs were treated using a moving diffuser. Diffuse reflectance and fluorescence measurements were made using a multi-fiber optical probe positioned on the surface of various tissues within the cavity before and after illumination. The measured data were analyzed to quantify hemoglobin concentration and oxygenation and sensitizer concentration.

  5. Nitrogen doping study in ingot niobium cavities

    SciTech Connect

    Dhakal, Pashupati; Ciovati, Gianluigi; Kneisel, Peter; Myneni, Ganapati Rao; Makita, Junki

    2015-09-01

    Thermal diffusion of nitrogen in niobium superconducting radio frequency cavities at temperature ~800 C has resulted in the increase in quality factor with a low-field Q-rise extending to Bp > 90 mT. However, the maximum accelerating gradient of these doped cavities often deteriorates below the values achieved by standard treatments prior to doping. Here, we present the results of the measurements on ingot niobium cavities doped with nitrogen at 800 C. The rf measurements were carried out after the successive electropolishing to remove small amount of material from the inner surface layer. The result showed higher breakdown field with lower quality factor as material removal increases.

  6. High density protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rouleau, Robyn (Inventor); Delucas, Lawrence (Inventor); Hedden, Douglas Keith (Inventor)

    2004-01-01

    A protein crystal growth assembly including a crystal growth cell and further including a cell body having a top side and a bottom side and a first aperture defined therethrough, the cell body having opposing first and second sides and a second aperture defined therethrough. A cell barrel is disposed within the cell body, the cell barrel defining a cavity alignable with the first aperture of the cell body, the cell barrel being rotatable within the second aperture. A reservoir is coupled to the bottom side of the cell body and a cap having a top side is disposed on the top side of the cell body. The protein crystal growth assembly may be employed in methods including vapor diffusion crystallization, liquid to liquid crystallization, batch crystallization, and temperature induction batch mode crystallization.

  7. Dual frequency optical cavity

    DOEpatents

    George, E. Victor (Livermore, CA); Schipper, John F. (Palo Alto, CA)

    1985-01-01

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a "T" configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  8. 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.

  9. 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.

  10. 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

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

    SciTech Connect

    Han, Jun-feng; Liao, Cheng; Jiang, Tao; Xie, Hua-mu; Zhao, Kui

    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.

  12. Saracatinib impairs the peritoneal dissemination of diffuse-type gastric carcinoma cells resistant to Met and fibroblast growth factor receptor inhibitors

    PubMed Central

    Yamaguchi, Hideki; Takanashi, Miho; Yoshida, Nachi; Ito, Yuumi; Kamata, Reiko; Fukami, Kiyoko; Yanagihara, Kazuyoshi; Sakai, Ryuichi

    2014-01-01

    Diffuse-type gastric carcinomas (DGC) exhibit more aggressive progression and poorer prognosis than intestinal-type and other gastric carcinomas. To identify potential therapeutic targets, we examined protein tyrosine phosphorylation in a panel of DGC and other gastric cancer cell lines. Protein tyrosine phosphorylation was significantly enhanced or altered in DGC cell lines compared with that in other gastric cancer cell lines. Affinity purification and mass spectrometry analysis of tyrosine-phosphorylated proteins identified Met as a protein that is preferentially expressed and phosphorylated in DGC cell lines. Unexpectedly, Met inhibitors blocked cell growth, Met downstream signaling and peritoneal dissemination in vivo in only a subset of cell lines that exhibited remarkable overexpression of Met. Likewise, only cell lines with overexpression of fibroblast growth factor receptor 2 (FGFR2) or phosphorylation of FRS2 were sensitive to an FGFR2 inhibitor. A Src inhibitor saracatinib impaired growth in cell lines that are insensitive to both Met and FGFR2 inhibitors. Saracatinib also effectively impaired peritoneal dissemination of Met-independent and FGFR2-independent SGC cells. Moreover, DGC cell lines exhibited nearly mutually exclusive susceptibility to Met, FGFR and Src inhibitors. These results suggest that DGC have distinct sensitivities to molecular target drugs and that targeting Src is beneficial in the treatment of DGC insensitive to Met and FGFR inhibition. PMID:24612061

  13. Exo-endocytic trafficking and the septin-based diffusion barrier are required for the maintenance of Cdc42p polarization during budding yeast asymmetric growth

    PubMed Central

    Orlando, Kelly; Sun, Xiaoli; Zhang, Jian; Lu, Tu; Yokomizo, Lauren; Wang, Puyue; Guo, Wei

    2011-01-01

    Cdc42p plays a central role in asymmetric cell growth in yeast by controlling actin organization and vesicular trafficking. However, how Cdc42p is maintained specifically at the daughter cell plasma membrane during asymmetric cell growth is unclear. We have analyzed Cdc42p localization in yeast mutants defective in various stages of membrane trafficking by fluorescence microscopy and biochemical fractionation. We found that two separate exocytic pathways mediate Cdc42p delivery to the daughter cell. Defects in one of these pathways result in Cdc42p being rerouted through the other. In particular, the pathway involving trafficking through endosomes may couple Cdc42p endocytosis from, and subsequent redelivery to, the plasma membrane to maintain Cdc42p polarization at the daughter cell. Although the endo-exocytotic coupling is necessary for Cdc42p polarization, it is not sufficient to prevent the lateral diffusion of Cdc42p along the cell cortex. A barrier function conferred by septins is required to counteract the dispersal of Cdc42p and maintain its localization in the daughter cell but has no effect on the initial polarization of Cdc42p at the presumptive budding site before symmetry breaking. Collectively, membrane trafficking and septins function synergistically to maintain the dynamic polarization of Cdc42p during asymmetric growth in yeast. PMID:21209323

  14. Saracatinib impairs the peritoneal dissemination of diffuse-type gastric carcinoma cells resistant to Met and fibroblast growth factor receptor inhibitors.

    PubMed

    Yamaguchi, Hideki; Takanashi, Miho; Yoshida, Nachi; Ito, Yuumi; Kamata, Reiko; Fukami, Kiyoko; Yanagihara, Kazuyoshi; Sakai, Ryuichi

    2014-05-01

    Diffuse-type gastric carcinomas (DGC) exhibit more aggressive progression and poorer prognosis than intestinal-type and other gastric carcinomas. To identify potential therapeutic targets, we examined protein tyrosine phosphorylation in a panel of DGC and other gastric cancer cell lines. Protein tyrosine phosphorylation was significantly enhanced or altered in DGC cell lines compared with that in other gastric cancer cell lines. Affinity purification and mass spectrometry analysis of tyrosine-phosphorylated proteins identified Met as a protein that is preferentially expressed and phosphorylated in DGC cell lines. Unexpectedly, Met inhibitors blocked cell growth, Met downstream signaling and peritoneal dissemination in vivo in only a subset of cell lines that exhibited remarkable overexpression of Met. Likewise, only cell lines with overexpression of fibroblast growth factor receptor 2 (FGFR2) or phosphorylation of FRS2 were sensitive to an FGFR2 inhibitor. A Src inhibitor saracatinib impaired growth in cell lines that are insensitive to both Met and FGFR2 inhibitors. Saracatinib also effectively impaired peritoneal dissemination of Met-independent and FGFR2-independent SGC cells. Moreover, DGC cell lines exhibited nearly mutually exclusive susceptibility to Met, FGFR and Src inhibitors. These results suggest that DGC have distinct sensitivities to molecular target drugs and that targeting Src is beneficial in the treatment of DGC insensitive to Met and FGFR inhibition. PMID:24612061

  15. Effect of the anisotropic surface tension, crystallization kinetics, and heat diffusion on nonequilibrium growth of liquid crystals

    NASA Astrophysics Data System (ADS)

    Börzsönyi, T.; Buka, Á.; Kramer, L.

    1998-11-01

    The morphologies of a homeotropic smectic-B germ growing into an undercooled homeotropic or planar nematic melt were studied. The two sets of growth shapes observed in the experiment were reproduced by computer simulations using a phase-field model. From the comparison of the experiment and numerical simulations we give an estimate for the anisotropy of the surface tension and the kinetic coefficient for the case of the homeotropic nematic melt. In the case of the planarly aligned melt the twofold anisotropy of the nematic superimposes onto the hexagonal symmetry of the smectic B. An explanation of the phenomenon of the ``inverted growth'' is given.

  16. Effects of electron-phonon coupling and electron diffusion on ripples growth on ultrafast-laser-irradiated metals

    SciTech Connect

    Colombier, J. P.; Garrelie, F.; Faure, N.; Reynaud, S.; Bounhalli, M.; Audouard, E.; Stoian, R.; Pigeon, F.

    2012-01-15

    Metals exposed to ultrafast laser irradiation close to ablative regimes show often a submicron-scale (near 0.5 {mu}m) periodic organization of the surface as ripples. Using two classes of metallic materials (transition and noble), we have determined that the ripples amplitude is strongly correlated to the material transport properties, namely electron-phonon relaxation strength, electronic diffusion, and to the energy band characteristics of the electronic laser excitation. This particularly depends on the topology of the electronic structure, including d-band effects on electronic excitation. Comparing the effects of electron-phonon nonequilibrium lifetimes for the different metals under similar irradiation conditions, we indicate how the electron-phonon coupling strength affects the electronic thermal diffusion, the speed of phase transformation and impacts on the ripples contrast. The highest contrast is observed for ruthenium, where the electron-phonon coupling is the strongest, followed by tungsten, nickel, and copper, the latter with the least visible contrast. The dependence of surface patterns contrast with fluence is linked to the dependence of the relaxation characteristics with the electronic temperature.

  17. Simulations of Overexpanding CME Cavities

    NASA Astrophysics Data System (ADS)

    Kliem, B.; Forbes, T.; Vourlidas, A.; Patsourakos, S.

    2010-12-01

    Coronal mass ejection (CME) cavities seen in white-light coronagraphs expand nearly self similarly in the outer corona and inner solar wind. Little is known about their initial expansion in the inner corona. A two-phase evolution, consisting of an initial overexpansion up to a heliocentric front height of about 1.5 solar radii, followed by nearly self-similar expansion, was recently discovered in STEREO/SECCHI observations of a fast CME (Patsourakos et al. 2010). The overexpansion is expressed as a decrease of the cavity aspect ratio (center height by radius) by at least a factor of 2 during the rise phase of the main CME acceleration. We present MHD simulations of erupting flux ropes that show the initial overexpansion of a cavity in line with the observed evolution. The contributions of ideal-MHD expansion and of magnetic reconnection to the growth of the flux rope and cavity in the simulations will be quantified to identify the primary cause of the overexpansion. This assesses the diagnostic potential of the overexpansion for the change of flux rope current and the role of magnetic reconnection in the early evolution of CMEs.

  18. Crystal growth of phosphopantetheine adenylyltransferase, carboxypeptidase t, and thymidine phosphorylase on the international space station by the capillary counter-diffusion method

    SciTech Connect

    Kuranova, I. P. Smirnova, E. A.; Abramchik, Yu. A.; Chupova, L. A.; Esipov, R. S.; Akparov, V. Kh.; Timofeev, V. I.; Kovalchuk, M. V.

    2011-09-15

    Crystals of phosphopantetheine adenylyltransferase from Mycobacterium tuberculosis, thymidine phosphorylase from Escherichia coli, carboxypeptidase T from Thermoactinomyces vulgaris and its mutant forms, and crystals of complexes of these proteins with functional ligands and inhibitors were grown by the capillary counter-diffusion method in the Japanese Experimental Module Kibo on the International Space Station. The high-resolution X-ray diffraction data sets suitable for the determination of high-resolution three-dimensional structures of these proteins were collected from the grown crystals on the SPring-8 synchrotron radiation facility. The conditions of crystal growth for the proteins and the data-collection statistics are reported. The crystals grown in microgravity diffracted to a higher resolution than crystals of the same proteins grown on Earth.

  19. Crystal growth of phosphopantetheine adenylyltransferase, carboxypeptidase t, and thymidine phosphorylase on the international space station by the capillary counter-diffusion method

    NASA Astrophysics Data System (ADS)

    Kuranova, I. P.; Smirnova, E. A.; Abramchik, Yu. A.; Chupova, L. A.; Esipov, R. S.; Akparov, V. Kh.; Timofeev, V. I.; Kovalchuk, M. V.

    2011-09-01

    Crystals of phosphopantetheine adenylyltransferase from Mycobacterium tuberculosis, thymidine phosphorylase from Escherichia coli, carboxypeptidase T from Thermoactinomyces vulgaris and its mutant forms, and crystals of complexes of these proteins with functional ligands and inhibitors were grown by the capillary counter-diffusion method in the Japanese Experimental Module Kibo on the International Space Station. The high-resolution X-ray diffraction data sets suitable for the determination of high-resolution three-dimensional structures of these proteins were collected from the grown crystals on the SPring-8 synchrotron radiation facility. The conditions of crystal growth for the proteins and the data-collection statistics are reported. The crystals grown in microgravity diffracted to a higher resolution than crystals of the same proteins grown on Earth.

  20. Long-Term Functional Outcomes and Correlation with Regional Brain Connectivity by MRI Diffusion Tractography Metrics in a Near-Term Rabbit Model of Intrauterine Growth Restriction

    PubMed Central

    Illa, Miriam; Eixarch, Elisenda; Batalle, Dafnis; Arbat-Plana, Ariadna; Muñoz-Moreno, Emma; Figueras, Francesc; Gratacos, Eduard

    2013-01-01

    Background Intrauterine growth restriction (IUGR) affects 5–10% of all newborns and is associated with increased risk of memory, attention and anxiety problems in late childhood and adolescence. The neurostructural correlates of long-term abnormal neurodevelopment associated with IUGR are unknown. Thus, the aim of this study was to provide a comprehensive description of the long-term functional and neurostructural correlates of abnormal neurodevelopment associated with IUGR in a near-term rabbit model (delivered at 30 days of gestation) and evaluate the development of quantitative imaging biomarkers of abnormal neurodevelopment based on diffusion magnetic resonance imaging (MRI) parameters and connectivity. Methodology At +70 postnatal days, 10 cases and 11 controls were functionally evaluated with the Open Field Behavioral Test which evaluates anxiety and attention and the Object Recognition Task that evaluates short-term memory and attention. Subsequently, brains were collected, fixed and a high resolution MRI was performed. Differences in diffusion parameters were analyzed by means of voxel-based and connectivity analysis measuring the number of fibers reconstructed within anxiety, attention and short-term memory networks over the total fibers. Principal Findings The results of the neurobehavioral and cognitive assessment showed a significant higher degree of anxiety, attention and memory problems in cases compared to controls in most of the variables explored. Voxel-based analysis (VBA) revealed significant differences between groups in multiple brain regions mainly in grey matter structures, whereas connectivity analysis demonstrated lower ratios of fibers within the networks in cases, reaching the statistical significance only in the left hemisphere for both networks. Finally, VBA and connectivity results were also correlated with functional outcome. Conclusions The rabbit model used reproduced long-term functional impairments and their neurostructural correlates of abnormal neurodevelopment associated with IUGR. The description of the pattern of microstructural changes underlying functional defects may help to develop biomarkers based in diffusion MRI and connectivity analysis. PMID:24143189

  1. NOON states in cavities

    E-print Network

    D. Rodríguez-Méndez; H. M. Moya-Cessa

    2013-04-24

    We show how NOON states may be generated entangling two cavities by passing atoms through them. The atoms interact with each cavity via two-photon resonant transitions. We take advantage of the fact that depending on the state the atom enter (excite or ground), it leaves or takes two photons per interaction and leaves the cavities in a pure state.

  2. 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.

  3. Carbon dioxide diffusion across stomata and mesophyll and photo-biochemical processes as affected by growth CO2 and phosphorus nutrition in cotton.

    PubMed

    Singh, Shardendu K; Badgujar, Girish; Reddy, Vangimalla R; Fleisher, David H; Bunce, James A

    2013-06-15

    Nutrients such as phosphorus may exert a major control over plant response to rising atmospheric carbon dioxide concentration (CO2), which is projected to double by the end of the 21st century. Elevated CO2 may overcome the diffusional limitations to photosynthesis posed by stomata and mesophyll and alter the photo-biochemical limitations resulting from phosphorus deficiency. To evaluate these ideas, cotton (Gossypium hirsutum) was grown in controlled environment growth chambers with three levels of phosphate (Pi) supply (0.2, 0.05 and 0.01mM) and two levels of CO2 concentration (ambient 400 and elevated 800?molmol(-1)) under optimum temperature and irrigation. Phosphate deficiency drastically inhibited photosynthetic characteristics and decreased cotton growth for both CO2 treatments. Under Pi stress, an apparent limitation to the photosynthetic potential was evident by CO2 diffusion through stomata and mesophyll, impairment of photosystem functioning and inhibition of biochemical process including the carboxylation efficiency of ribulose-1,5-bisphosphate carboxylase/oxyganase and the rate of ribulose-1,5-bisphosphate regeneration. The diffusional limitation posed by mesophyll was up to 58% greater than the limitation due to stomatal conductance (gs) under Pi stress. As expected, elevated CO2 reduced these diffusional limitations to photosynthesis across Pi levels; however, it failed to reduce the photo-biochemical limitations to photosynthesis in phosphorus deficient plants. Acclimation/down regulation of photosynthetic capacity was evident under elevated CO2 across Pi treatments. Despite a decrease in phosphorus, nitrogen and chlorophyll concentrations in leaf tissue and reduced stomatal conductance at elevated CO2, the rate of photosynthesis per unit leaf area when measured at the growth CO2 concentration tended to be higher for all except the lowest Pi treatment. Nevertheless, plant biomass increased at elevated CO2 across Pi nutrition with taller plants, increased leaf number and larger leaf area. PMID:23384758

  4. VOLUME 87, NUMBER 13 P H Y S I C A L R E V I E W L E T T E R S 24 SEPTEMBER 2001 Laplacian Growth and Diffusion Limited Aggregation: Different Universality Classes

    E-print Network

    Levermann, Anders

    VOLUME 87, NUMBER 13 P H Y S I C A L R E V I E W L E T T E R S 24 SEPTEMBER 2001 Laplacian Growth and Diffusion Limited Aggregation: Different Universality Classes Felipe Barra, Benny Davidovitch, Anders

  5. 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.

  6. Optically measuring interior cavities

    DOEpatents

    Stone, Gary Franklin (Livermore, CA)

    2009-11-03

    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.

  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. Growth kinetics and microstructural evolution during hot isostatic pressing of U-10 wt.% Mo monolithic fuel plate in AA6061 cladding with Zr diffusion barrier

    NASA Astrophysics Data System (ADS)

    Park, Y.; Yoo, J.; Huang, K.; Keiser, D. D.; Jue, J. F.; Rabin, B.; Moore, G.; Sohn, Y. H.

    2014-04-01

    Phase constituents and microstructure changes in RERTR fuel plate assemblies as functions of temperature and duration of hot-isostatic pressing (HIP) during fabrication were examined. The HIP process was carried out as functions of temperature (520, 540, 560 and 580 °C for 90 min) and time (45-345 min at 560 °C) to bond 6061 Al-alloy to the Zr diffusion barrier that had been co-rolled with U-10 wt.% Mo (U10Mo) fuel monolith prior to the HIP process. Scanning and transmission electron microscopies were employed to examine the phase constituents, microstructure and layer thickness of interaction products from interdiffusion. At the interface between the U10Mo and Zr, following the co-rolling, the UZr2 phase was observed to develop adjacent to Zr, and the ?-U phase was found between the UZr2 and U10Mo, while the Mo2Zr was found as precipitates mostly within the ?-U phase. The phase constituents and thickness of the interaction layer at the U10Mo-Zr interface remained unchanged regardless of HIP processing variation. Observable growth due to HIP was only observed for the (Al,Si)3Zr phase found at the Zr/AA6061 interface, however, with a large activation energy of 457 ± 28 kJ/mole. Thus, HIP can be carried to improve the adhesion quality of fuel plate without concern for the excessive growth of the interaction layer, particularly at the U10Mo-Zr interface with the ?-U, Mo2Zr, and UZr2 phases.

  9. Growth kinetics and microstructural evolution during hot isostatic pressing of U-10 wt.% Mo monolithic fuel plate in AA6061 cladding with Zr diffusion barrier

    SciTech Connect

    Y. Park; J. Yoo; K. Huang; D. D. Keiser, Jr.; J. F. Jue; B. Rabin; G. Moore; Y. H. Sohn

    2014-04-01

    Phase constituents and microstructure changes in RERTR fuel plate assemblies as functions of temperature and duration of hot-isostatic pressing (HIP) during fabrication were examined. The HIP process was carried out as functions of temperature (520, 540, 560 and 580 °C for 90 min) and time (45–345 min at 560 °C) to bond 6061 Al-alloy to the Zr diffusion barrier that had been co-rolled with U-10 wt.% Mo (U10Mo) fuel monolith prior to the HIP process. Scanning and transmission electron microscopies were employed to examine the phase constituents, microstructure and layer thickness of interaction products from interdiffusion. At the interface between the U10Mo and Zr, following the co-rolling, the UZr2 phase was observed to develop adjacent to Zr, and the a-U phase was found between the UZr2 and U10Mo, while the Mo2Zr was found as precipitates mostly within the a-U phase. The phase constituents and thickness of the interaction layer at the U10Mo-Zr interface remained unchanged regardless of HIP processing variation. Observable growth due to HIP was only observed for the (Al,Si)3Zr phase found at the Zr/AA6061 interface, however, with a large activation energy of 457 ± 28 kJ/mole. Thus, HIP can be carried to improve the adhesion quality of fuel plate without concern for the excessive growth of the interaction layer, particularly at the U10Mo-Zr interface with the a-U, Mo2Zr, and UZr2 phases.

  10. Tungsten diffusion in silicon

    SciTech Connect

    De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B.; Portavoce, A.; Grosjean, C.

    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.

  11. Cavity design programs

    SciTech Connect

    Nelson, E.M.

    1996-09-09

    Numerous computer programs are available to help accelerator physicists and engineers model and design accelerator cavities and other microwave components. This article discusses the problems these programs solve and the principles upon which these programs are based. Some examples of how these programs are used in the design of accelerator cavities are also given.

  12. Liquid laser cavities

    NASA Technical Reports Server (NTRS)

    Bjorklund, S.; Filipescu, N.; Kellermeyer, G. L.; Mc Avoy, N.

    1969-01-01

    Liquid laser cavities have plenum chambers at the ends of the capillary cell which are terminated in transparent optical flats. By use of these cavities, several new europium chelates and a terbium chelate can provide laser action in solution at room temperature.

  13. Superconducting-Cavity Accelerometer

    NASA Technical Reports Server (NTRS)

    Reinhardt, V. S.; Von Bun, F.

    1985-01-01

    Resonant frequency of microwave superconducting cavity sensitive to gravitation and acceleration. Sensitive accelerometer assembled by combining superconducting microwave cavity and conventional microwave semiconductor oscillator circuit. Device measures acelerations as small as 10-10 cm/S2 (10-13 g's). Also configured to measure small gradients in gravitational field of Earth.

  14. 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.

  15. Temperature Mapping of Nitrogen-doped Niobium Superconducting Radiofrequency Cavities

    SciTech Connect

    Makita, Junki; Ciovati, Gianluigi; Dhakal, Pashupati

    2015-09-01

    It was recently shown that diffusing nitrogen on the inner surface of superconducting radiofrequency (SRF) cavities at high temperature can improve the quality factor of the niobium cavity. However, a reduction of the quench field is also typically found. To better understand the location of rf losses and quench, we used a thermometry system to map the temperature of the outer surface of ingot Nb cavities after nitrogen doping and electropolishing. Surface temperature of the cavities was recorded while increasing the rf power and also during the quenching. The results of thermal mapping showed no precursor heating on the cavities and quenching to be ignited near the equator where the surface magnetic field is maximum. Hot-spots at the equator area during multipacting were also detected by thermal mapping.

  16. 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.

  17. Erbium diffusion in silicon dioxide

    SciTech Connect

    Lu Yingwei; Julsgaard, B.; Petersen, M. Christian; Jensen, R. V. Skougaard; Pedersen, T. Garm; Pedersen, K.; Larsen, A. Nylandsted

    2010-10-04

    Erbium diffusion in silicon dioxide layers prepared by magnetron sputtering, chemical vapor deposition, and thermal growth has been investigated by secondary ion mass spectrometry, and diffusion coefficients have been extracted from simulations based on Fick's second law of diffusion. Erbium diffusion in magnetron sputtered silicon dioxide from buried erbium distributions has in particular been studied, and in this case a simple Arrhenius law can describe the diffusivity with an activation energy of 5.3{+-}0.1 eV. Within a factor of two, the erbium diffusion coefficients at a given temperature are identical for all investigated matrices.

  18. Hydroforming of elliptical cavities

    SciTech Connect

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

    2015-02-27

    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.

  19. Tuned optical cavity magnetometer

    DOEpatents

    Okandan, Murat (Edgewood, NM); Schwindt, Peter (Albuquerque, NM)

    2010-11-02

    An atomic magnetometer is disclosed which utilizes an optical cavity formed from a grating and a mirror, with a vapor cell containing an alkali metal vapor located inside the optical cavity. Lasers are used to magnetically polarize the alkali metal vapor and to probe the vapor and generate a diffracted laser beam which can be used to sense a magnetic field. Electrostatic actuators can be used in the magnetometer for positioning of the mirror, or for modulation thereof. Another optical cavity can also be formed from the mirror and a second grating for sensing, adjusting, or stabilizing the position of the mirror.

  20. Hydroforming of elliptical cavities

    DOE PAGESBeta

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

    2015-02-27

    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

  1. 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.

  2. 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.

  3. What Are Oral Cavity and Oropharyngeal Cancers?

    MedlinePLUS

    ... oral cavity and oropharyngeal cancers? What are oral cavity and oropharyngeal cancers? Oral cavity cancer, or just ... parts of the mouth and throat. The oral cavity (mouth) and oropharynx (throat) The oral cavity includes ...

  4. Moving Detectors in Cavities

    E-print Network

    Nathaniel Obadia

    2007-07-15

    We consider two-level detectors, coupled to a quantum scalar field, moving inside cavities. We highlight some pathological resonant effects due to abrupt boundaries, and decide to describe the cavity by switching smoothly the interaction by a time-dependent gate-like function. Considering uniformly accelerated trajectories, we show that some specific choices of non-adiabatic switching have led to hazardous interpretations about the enhancement of the Unruh effect in cavities. More specifically, we show that the emission/absorption ratio takes arbitrary high values according to the emitted quanta properties and to the transients undergone at the entrance and the exit of the cavity, {\\it independently of the acceleration}. An explicit example is provided where we show that inertial and uniformly accelerated world-lines can even lead to the same ``pseudo-temperature''.

  5. 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.

  6. Creep cavity observation using liquid metal embrittlement

    SciTech Connect

    Reiley, T.C.

    1981-01-01

    Grain boundary cavities, which form during high-temperature deformation and which may be considered incipient intergranular cracks, have been difficult to observe at the early growth stages. To examine grain boundaries in unfailed specimans one is normally limited to metallographic or transmission electron microscopy (TEM) techniques, the first having resolution limitations (r/sub cavity/approx.l..mu..m) and the second having limitations in the probability of seeing a cavity (especially for large-grained, low-density specimens) or of seeing a cavity which is undisturbed by the thinning process required for TEM. Other observational techniques involving hydrogen attack or low-temperature impact loading have been used to create brittle intergranular failures to observe grain boundary features, such as creep cavities on pre-crept specimens. These techniques are not, however, applicable to most metals, and as such, the need remains for a more general observational technique. Such a new technique employing liquid metal embrittlement (LME) is described below, and, given that most metals are severely embrittled by at least one liquid metal, this approach may satisfy requirements of general applicability.

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

    SciTech Connect

    Odbadrakh, Khorgolkhuu; McNutt, Nichiolas William; Nicholson, Donald M.; Rios, Orlando; Keffer, David J.

    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.

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

    SciTech Connect

    Odbadrakh, Khorgolkhuu; McNutt, N. W.; Nicholson, D. M.; Rios, O.; Keffer, D. J.

    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.

  9. 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).

  10. 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.

  11. Creation of X-ray cavities in galaxy clusters with cosmic rays

    E-print Network

    W. G. Mathews; F. Brighenti

    2007-01-24

    We describe how AGN-produced cosmic rays form large X-ray cavities and radio lobes in the hot diffuse gas in galaxy groups and clusters. Cosmic rays are assumed to be produced in a small shocked region near the cavity center, such as at the working surface of a radio jet. The coupled equations for gasdynamics and cosmic ray diffusion are solved with various assumptions about the diffusion coefficient. To form large, long-lived cavities similar to those observed, the diffusion coefficient must not exceed kappa = 10^28 cm^2/s in the hot gas, very similar to values required in models of cosmic ray diffusion in the Milky Way. When kappa does not exceed 10^28, cosmic rays are confined within the cavities for times comparable to the cavity buoyancy time, as implied by observations of X-ray cavities and their radio synchrotron emission. Collisions of proton cosmic rays with thermal plasma nuclei followed by pion decay can result in enhanced gamma ray emission from the cavity walls.

  12. Energetics of X-ray Cavities and Radio Lobes in Galaxy Clusters

    E-print Network

    W. G. Mathews; F. Brighenti

    2008-05-16

    We describe the formation and evolution of X-ray cavities in the hot gas of galaxy clusters. The cavities are formed only with relativistic cosmic rays that eventually diffuse into the surrounding gas. We explore the evolution of cavities formed with a wide range of cosmic ray diffusion rates. In previous numerical simulations cavities are formed by injecting ultra-hot but non-relativistic gas which increases the global thermal energy, offsetting radiative losses in the gas and helping to solve the cooling flow problem. Contrary to these results, we find that X-ray cavities formed solely by cosmic rays have a global cooling effect. As the cluster gas is displaced by cosmic rays, a global expansion of the cluster gas occurs with associated cooling that exceeds the heating by shock waves as the cavity forms. Most cosmic rays in our cavity evolutions do not move beyond the cooling radius even after 1 Gyr. The gas density is depressed by cosmic rays, becomes buoyant, and undergoes a significant outward mass transfer within the cooling radius, carrying cosmic rays and relatively low entropy gas to distant regions in the cluster where it remains for times exceeding the local cooling time in the hot gas. This post-cavity mass outflow due to cosmic ray buoyancy may contribute toward solving the cooling flow problem. We describe the energetics, size, stability and buoyant rise of X-ray cavities in detail, showing how each depends on the rate of cosmic ray diffusion.

  13. 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.

  14. Cavity flow. Citations from the NTIS data base

    NASA Astrophysics Data System (ADS)

    Habercom, G. E., Jr.

    1980-05-01

    Reports are cited on shallow and deep configurations, holes, cutouts, hollows, notches, gaps, orifices, flaps, and steps. Applications include bomb bays, aerodynamic windows, microwave cavitites, resonators, diffusers, laser cavities, and jets. This updated bibliography contains 260 abstracts, 29 of which are new entries to the previous edition.

  15. 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.

  16. Analog cavity simulator

    NASA Astrophysics Data System (ADS)

    Orel, Peter; Mavri?, Uroš

    2013-11-01

    Most of the low-level radio frequency (LLRF) systems are being developed well before the machines are being set up and ready to be commissioned. Therefore it is imperative to be able to test and evaluate their functionality and performance in the laboratory, before the instrument is installed in the final configuration. Real accelerator cavities are very expensive and frequency-dependent, hence impractical for mass factory testing of instrumentation. As an alternative, we developed an analog cavity simulator. The article gives an explanation of the main design concept, some key considerations of its implementation in order to reach the required specifications, and presents the test results, showing the simulator performance.

  17. Axial flow laser cavity

    NASA Astrophysics Data System (ADS)

    Ortwerth, P. J.; Lampson, A. I.

    1984-11-01

    This patent discloses an improved gaseous laser device which comprises a generally tubular laser discharge tube having a laser window at each end. Each window disposed at an angle to the lasing axis of the device corresponding substantially to the Brewster's angle is characteristic of the material comprising the windows, and directs substantial uniform flow of gaseous laser medium into and out of the discharge tube at said angle. A choked gaseous exhaust exit for canceling cavity disturbances is provided within the device. Laser optics defining an optical resonant cavity of the laser device may be disposed external of the discharge tube and windows.

  18. Active cavity radiometer.

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1973-01-01

    The active cavity radiometer (ACR) is a pyrheliometer that accurately defines the absolute radiation scale. The physics of the pyrheliometric method and the ACR approach to this method are presented in detail. A mathematical abstraction of the method is generated through a quasi-equilibrium analysis of the power balance of the ACR's cavity detector. An error analysis is carried out on the quasi-equilibrium equation to determine the uncertainties of ACR measurements relative to the absolute radiation scale. The uncertainty of ACR measurements as a function of irradiance level is presented in graphical form.

  19. Active cavity radiometer.

    PubMed

    Willson, R C

    1973-04-01

    The active cavity radiometer (ACR) is a pyrheliometer that accurately defines the absolute radiation scale. The physics of the pyrheliometric method and the ACR approach to this method are presented in detail. A mathematical abstraction of the method is generated through a quasi-equilibrium analysis of the power balance of the ACR's cavity detector. An error analysis is carried out on the quasi-equilibrium equation to determine the uncertainties of ACR measurements relative to the absolute radiation scale. The uncertainty of ACR measurements as a function of irradiance level is presented in graphical form. PMID:20125394

  20. Interaction of cavities with misfit dislocations in SiGe/Si heterostructures

    SciTech Connect

    Follstaedt, D.M.; Myers, S.M.; Floro, J.A.; Lee, S.R.

    1996-09-01

    Consequences of the strong, short-range attractive interaction between cavities and misfit dislocations are examined in SiGe/Si heterostructures. When He is implanted at the SiGe/Si interface, either in situ during epitaxial growth or by post-growth treatment, cavities form and locate on the misfit dislocation cores. The misfit dislocations are no longer straight lines extending over several microns, but form a network with jogs and intersections at the cavities. The He-implanted cavity layer enhances thermal relaxation of the strained alloy and may increase the achievable degree of relaxation by lowering dislocation energies.

  1. 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.

  2. Broadband cavity electromagnetically induced transparency

    SciTech Connect

    Wei Xiaogang; Wang Yanhua; Zhang Jiepeng; Zhu Yifu

    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. Principal Component Analysis reveals correlation of cavities evolution and functional motions in proteins.

    PubMed

    Desdouits, Nathan; Nilges, Michael; Blondel, Arnaud

    2015-02-01

    Protein conformation has been recognized as the key feature determining biological function, as it determines the position of the essential groups specifically interacting with substrates. Hence, the shape of the cavities or grooves at the protein surface appears to drive those functions. However, only a few studies describe the geometrical evolution of protein cavities during molecular dynamics simulations (MD), usually with a crude representation. To unveil the dynamics of cavity geometry evolution, we developed an approach combining cavity detection and Principal Component Analysis (PCA). This approach was applied to four systems subjected to MD (lysozyme, sperm whale myoglobin, Dengue envelope protein and EF-CaM complex). PCA on cavities allows us to perform efficient analysis and classification of the geometry diversity explored by a cavity. Additionally, it reveals correlations between the evolutions of the cavities and structures, and can even suggest how to modify the protein conformation to induce a given cavity geometry. It also helps to perform fast and consensual clustering of conformations according to cavity geometry. Finally, using this approach, we show that both carbon monoxide (CO) location and transfer among the different xenon sites of myoglobin are correlated with few cavity evolution modes of high amplitude. This correlation illustrates the link between ligand diffusion and the dynamic network of internal cavities. PMID:25424655

  4. 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.

  5. Impact of Mesophyll Diffusion on Estimated Global Land CO2 Fertilization

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Gu, L.; Dickinson, R. E.

    2014-12-01

    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 so 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 PgC to 1057 PgC for the period of 1901 to 2010. This increase represents a 16% correction 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 yr-1ppm-1. This finding implies that the contemporary terrestrial biosphere is more CO2-limited than previously thought.

  6. 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

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

    SciTech Connect

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

    2005-09-20

    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 is available directly, precision frequency measurements require additional instrumentation, a Cavity Resonance Monitor (CRM). The analog version of such a device has been successfully used for several cavity tests [1]. In this paper we present a prototype of a Digital Cavity Resonance Monitor designed and built in the last year. The hardware of this instrument consists of an RF downconverter, digital quadrature demodulator and digital processor motherboard (Altera FPGA). The motherboard processes received data and computes frequency changes with a resolution of 0.2 Hz, with a 3 kHz output bandwidth.

  8. Quantum diffusion

    E-print Network

    Roumen Tsekov

    2011-04-20

    Quantum diffusion is studied via dissipative Madelung hydrodynamics. Initially the wave packet spreads ballistically, than passes for an instant through normal diffusion and later tends asymptotically to a sub-diffusive law. It is shown that the apparent quantum diffusion coefficient is not a universal physical parameter since it depends on the initial wave packet preparation. The overdamped quantum diffusion of an electron in the field of a periodic potential is also investigated; in this case the wave packet spreads logarithmically in time. Thermo-quantum diffusion of heavier particles as hydrogen, deuterium and tritium atoms in periodic potentials is studied and a simple estimate of the tunneling effect is obtained in the frames of a quasi-equilibrium semiclassical approach. The effective thermo-quantum temperature is also discussed in relation to the known temperature dependence of muon diffusivity in solids.

  9. Anomalous Diffusion Near Resonances

    SciTech Connect

    Sen, Tanaji; /Fermilab

    2010-05-01

    Synchro-betatron resonances can lead to emittance growth and the loss of luminosity. We consider the detailed dynamics of a bunch near such a low order resonance driven by crossing angles at the collision points. We characterize the nature of diffusion and find that it is anomalous and sub-diffusive. This affects both the shape of the beam distribution and the time scales for growth. Predictions of a simplified anomalous diffusion model are compared with direct simulations. Transport of particles near resonances is still not a well understood phenomenon. Often, without justification, phase space motion is assumed to be a normal diffusion process although at least one case of anomalous diffusion in beam dynamics has been reported [1]. Here we will focus on the motion near synchro-betatron resonances which can be excited by several means, including beams crossing at an angle at the collision points as in the LHC. We will consider low order resonances which couple the horizontal and longitudinal planes, both for simplicity and to observe large effects over short time scales. While the tunes we consider are not practical for a collider, nonetheless the transport mechanisms we uncover are also likely to operate at higher order resonances.

  10. Rotational cavity optomechanics

    E-print Network

    Bhattacharya, M

    2015-01-01

    We theoretically examine the optomechanical interaction between a rotating nanoparticle and an orbital angular momentum-carrying optical cavity mode. Specifically, we consider a dielectric nanosphere rotating uniformly in a ring-shaped optical potential inside a Fabry-Perot resonator. The motion of the particle is probed by a weak angular lattice, created by introducing two additional degenerate Laguerre-Gaussian cavity modes carrying equal and opposite orbital angular momenta. We demonstrate that the rotation frequency of the nanoparticle is imprinted on the probe optical mode, via the Doppler shift, and thus may be sensed experimentally using homodyne detection. We show analytically that the effect of the optical probe on the particle rotation vanishes in the regime of linear response, resulting in an accurate frequency measurement. We also numerically characterize the degradation of the measurement accuracy when the system is driven in the nonlinear regime. Our results are relevant to rotational Doppler ve...

  11. 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.

  12. Cavity enhanced atomic magnetometry

    NASA Astrophysics Data System (ADS)

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-10-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations.

  13. Cavity enhanced atomic magnetometry

    E-print Network

    Crepaz, Herbert; Dumke, Rainer

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations.

  14. Cavity enhanced atomic magnetometry.

    PubMed

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations. PMID:26481853

  15. Cavity enhanced atomic magnetometry

    PubMed Central

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations. PMID:26481853

  16. Loading a single photon into an optical cavity

    NASA Astrophysics Data System (ADS)

    Du, Shengwang; Liu, Chang; Sun, Yuan; Zhao, Luwei; Zhang, Shanchao; Loy, M. M. T.

    2015-05-01

    Confining and manipulating single photons inside a reflective optical cavity is an essential task of cavity quantum electrodynamics (CQED) for probing the quantum nature of light quanta. Such systems are also elementary building blocks for many protocols of quantum network, where remote cavity quantum nodes are coupled through flying photons. The connectivity and scalability of such a quantum network strongly depends on the efficiency of loading a single photon into cavity. In this work we demonstrate that a single photon with an optimal temporal waveform can be efficiently loaded into a cavity. Using heralded narrow-band single photons with exponential growth wave packet whose time constant matches the photon lifetime in the cavity, we demonstrate a loading efficiency of more than 87 percent from free space to a single-sided Fabry-Perot cavity. Our result and approach may enable promising applications in realizing large-scale CQED-based quantum networks. The work was supported by the Hong Kong RGC (Project No. 601411).

  17. Oral Cavity Surgery Codes

    Cancer.gov

    Oral Cavity Lip C000–C009, Base of Tongue C019, Other Parts of Tongue C020–C029, Gum C030–C039, Floor of Mouth C040–C049, Palate C050–C059, Other Parts of Mouth C060–C069 (Except for M9727, 9733, 9741-9742, 9764-9809, 9832, 9840-9931, 9945-9946, 9950-9967,

  18. Gyromultiplier with sectioned cavity

    SciTech Connect

    Bandurkin, I. V.; Mishakin, S. V.

    2010-11-15

    A novel scheme of a self-exciting single-cavity terahertz gyromultiplier is proposed and theoretically investigated. Simulations predict a possibility to obtain a power of 75 W at the frequency of 1.3 THz from the 80 kV/0.7 A electron beam when operating at the fourth cyclotron harmonic at the relatively low magnetic field of 14 T.

  19. 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.

  20. Unveiling hidden complex cavities formed during nanocrystalline self-assembly.

    PubMed

    Kim, Iltai; Kihm, Kenneth D

    2009-02-17

    The existence of hidden complex cavities formed inside a self-assembled nanocrystalline structure is discovered in real-time by using surface plasmon resonance near-field refractive index fingerprinting. Furthermore, computer analysis of the naturally occurring R-G-B interference fringes allowed us to reconstruct the 3D cavity formation and crystallization processes quantitatively. For the case of an aqueous droplet containing 10% by volume of 47 nm Al2O3 nanoparticles, the submicrometer-scale inner cavity peak grows up to 0.5% of the entire crystallized crust height of over 150 microm. The formation of the complex inner structure was found to be attributable to multiple cavity inceptions and their competing growth during the aquatic evaporation. This outcome provides a better understanding and feasible control of the formation of nanocrystalline inner structures. PMID:18759414

  1. LED lamp or bulb with remote phosphor and diffuser configuration with enhanced scattering properties

    DOEpatents

    Tong, Tao; Le Toquin, Ronan; Keller, Bernd; Tarsa, Eric; Youmans, Mark; Lowes, Theodore; Medendorp, Jr., Nicholas W; Van De Ven, Antony; Negley, Gerald

    2014-11-11

    An LED lamp or bulb is disclosed that comprises a light source, a heat sink structure and an optical cavity. The optical cavity comprises a phosphor carrier having a conversions material and arranged over an opening to the cavity. The phosphor carrier comprises a thermally conductive transparent material and is thermally coupled to the heat sink structure. An LED based light source is mounted in the optical cavity remote to the phosphor carrier with light from the light source passing through the phosphor carrier. A diffuser dome is included that is mounted over the optical cavity, with light from the optical cavity passing through the diffuser dome. The properties of the diffuser, such as geometry, scattering properties of the scattering layer, surface roughness or smoothness, and spatial distribution of the scattering layer properties may be used to control various lamp properties such as color uniformity and light intensity distribution as a function of viewing angle.

  2. 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.

  3. Convection-Enhanced Transport into Open Cavities : Effect of Cavity Aspect Ratio.

    PubMed

    Horner, Marc; Metcalfe, Guy; Ottino, J M

    2015-09-01

    Recirculating fluid regions occur in the human body both naturally and pathologically. Diffusion is commonly considered the predominant mechanism for mass transport into a recirculating flow region. While this may be true for steady flows, one must also consider the possibility of convective fluid exchange when the outer (free stream) flow is transient. In the case of an open cavity, convective exchange occurs via the formation of lobes at the downstream attachment point of the separating streamline. Previous studies revealed the effect of forcing amplitude and frequency on material transport rates into a square cavity (Horner in J Fluid Mech 452:199-229, 2002). This paper summarizes the effect of cavity aspect ratio on exchange rates. The transport process is characterized using both computational fluid dynamics modeling and dye-advection experiments. Lagrangian analysis of the computed flow field reveals the existence of turnstile lobe transport for this class of flows. Experiments show that material exchange rates do not vary linearly as a function of the cavity aspect ratio (A = W/H). Rather, optima are predicted for A ? 2 and A ? 2.73, with a minimum occurring at A ? 2.5. The minimum occurs at the point where the cavity flow structure bifurcates from a single recirculating flow cell into two corner eddies. These results have significant implications for mass transport environments where the geometry of the flow domain evolves with time, such as coronary stents and growing aneurysms. Indeed, device designers may be able to take advantage of the turnstile-lobe transport mechanism to tailor deposition rates near newly implanted medical devices. PMID:26577366

  4. Active cavity radiometer type V

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1980-01-01

    The paper deals with a new type of cavity sensor geometry used in the most recent of a series of solar flux pyrheliometers, known as the active cavity radiometer (ACR). The new Type V sensor design incorporates a modification of its predecessor, the ACR IV sensor. This modification decreases the uncertainty within which cavity absorptance can be predicted by more than a factor of 10.

  5. 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.

  6. Substrate Adhesion of a Nongrafted Flexible Polymer in a Cavity

    E-print Network

    Michael Bachmann; Wolfhard Janke

    2007-10-23

    In a contact density chain-growth study we investigate the solubility-temperature pseudo-phase diagram of a lattice polymer in a cavity with an attractive surface. In addition to the main phases of adsorbed and desorbed conformations we find numerous subphases of collapsed and expanded structures.

  7. Cavity soliton billiards

    SciTech Connect

    Prati, F.; Lugiato, L. A.; Tissoni, G.; Brambilla, M.

    2011-11-15

    The motion of a self-propelled cavity soliton in a laser where the pump profile acts as a square billiard is investigated. In the long-term dynamics, only closed trajectories are possible, exhibiting nonspecular reflections with striking similarities to walking droplets in a vibrated liquid bath. Open orbits can be achieved either by introducing scattering defects in the pump profile or in the presence of more than two solitons, due to their interaction. Such dynamical properties can be exploited for applications such as a compact soliton-force microscope.

  8. 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.

  9. 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

  10. A Casimir cannot cavity fly

    E-print Network

    Massimo Cerdonio; Carlo Rovelli

    2015-02-08

    The field inside a Casimir cavity has an effective negative mass, which acts as a buoyancy force in a gravitational field. Can this render the total mass of the cavity negative, making it "float" in the vacuum ? Recent theoretical arguments indicate that this is impossible. We provide support to this conclusion discussing a concrete simple model of cavity, with plane parallel metallic plates kept in mechanical equilibrium by a spring and placed in a weak gravitational field. We show that basic facts about the structure of matter imply that the total mass of the cavity is always positive. This has implications for the hypothetical relation between vacuum energy and cosmological constant.

  11. Observation of Cavity Rydberg Polaritons

    E-print Network

    Jia Ningyuan; Alexandros Georgakopoulos; Albert Ryou; Nathan Schine; Ariel Sommer; Jonathan Simon

    2015-11-12

    We demonstrate hybridization of optical cavity photons with atomic Rydberg excitations using electromagnetically induced transparency (EIT). The resulting dark state Rydberg polaritons exhibit a compressed frequency spectrum and enhanced lifetime indicating strong light-matter mixing. We study the coherence properties of cavity Rydberg polaritons and identify the generalized EIT linewidth for optical cavities. Strong collective coupling suppresses polariton losses due to inhomogeneous broadening, which we demonstrate by using different Rydberg levels with a range of polarizabilities. Our results point the way towards using cavity Rydberg polaritons as a platform for creating photonic quantum materials.

  12. Nanofriction in Cavity Quantum Electrodynamics.

    PubMed

    Fogarty, T; Cormick, C; Landa, H; Stojanovi?, Vladimir M; Demler, E; Morigi, Giovanna

    2015-12-01

    The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics. PMID:26684118

  13. Enhanced diffusion welding

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J. (inventors)

    1973-01-01

    Surfaces of unrecrystallized alloys are sanded and polished. This is followed by a two-step welding process by which the strength of the parent metal is retained at the weld joint. The first step forces the surfaces into intimate contact at a temperature where the metal still has good ductility. The second step causes diffusion, recrystallization, and grain growth across the original weld interface.

  14. Multicolor cavity metrology.

    PubMed

    Izumi, Kiwamu; Arai, Koji; Barr, Bryan; Betzwieser, Joseph; Brooks, Aidan; Dahl, Katrin; Doravari, Suresh; Driggers, Jennifer C; Korth, W Zach; Miao, Haixing; Rollins, Jameson; Vass, Stephen; Yeaton-Massey, David; Adhikari, Rana X

    2012-10-01

    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 4 orders of magnitude and promises to greatly enhance the stability and reliability of the current generation of gravitational-wave detectors. The possibility for using multicolor techniques to overcome current quantum and thermal noise limits is also discussed. PMID:23201656

  15. Applications of cavity optomechanics

    SciTech Connect

    Metcalfe, Michael

    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.

  16. Applications of cavity optomechanics

    NASA Astrophysics Data System (ADS)

    Metcalfe, Michael

    2014-09-01

    "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.

  17. 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.

  18. 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 ...

  19. In-situ imaging of creep cavities by synchrotron microradiography

    SciTech Connect

    Dobbyn, R.C.; Fields, R.J. ); Farris, J.; Harlow, D.G.; Delph, T.J. )

    1989-05-01

    The long term, high temperature failure mechanism for most polycrystalline metals and ceramics is creep cavitation. Small voids or cavities have been observed to nucleate and grow on stressed grain boundaries. Eventually, so many of the boundaries are covered by cavities that fracture occurs. Many theories have been proposed to predict the details of cavity nucleation and growth and this is still an area of current theoretical interest. Experiments designed to evaluate these theories have mainly compared predicted times-to-fracture with those observed in traditional polycrystalline creep specimens. One interesting approach compared the density change in specimens from interrupted tests with that predicted from theory. There have often been large discrepancies among the various theories and the above observations. More recently cryogenic fracturing followed by scanning electron microscopy, small angle neutron scattering (SANS), and quantitative metallographic image analysis coupled with appropriate stereology have been used to follow the size distribution development in time. There are more direct means of evaluating the theories of cavity nucleation and growth than comparison with time-to-fracture. Most of the experiments have been performed on polycrystals while the theories can most readily be applied to a single boundary. The stress acting on a particular grain boundary in a polycrystal is, in general, not known due to grain boundary sliding and load shedding. To address this problem, copper bicrysatl experiments have been performed in the presented research. While this approach permits evaluation of the stress dependence of the times-to-fracture, it has now proven to be easy to study the cavity growth rate or spacial distribution on the boundary. The authors have now overcome this drawback by imaging individual cavities in-situ using monochromatic synchrotron radiation (SR) microradiography.

  20. 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.

  1. Effects of heterogeneous structure and diffusion permeability of body tissues on decompression gas bubble dynamics.

    PubMed

    Nikolaev, V P

    2000-07-01

    To gain insight into the special nature of gas bubbles that may form in astronauts, aviators and divers, we developed a mathematical model which describes the following: 1) the dynamics of extravascular bubbles formed in intercellular cavities of a hypothetical tissue undergoing decompression; and 2) the dynamics of nitrogen tension in a thin layer of intercellular fluid and in a thick layer of cells surrounding the bubbles. This model is based on the assumption that, due to limited cellular membrane permeability for gas, a value of effective nitrogen diffusivity in the massive layer of cells in the radial direction is essentially lower compared to conventionally accepted values of nitrogen diffusivity in water and body tissues. Due to rather high nitrogen diffusivity in intercellular fluid, a bubble formed just at completion of fast one-stage reduction of ambient pressure almost instantly grows to the size determined by the initial volume of the intercellular cavity, surface tension of the fluid, the initial nitrogen tension in the tissue, and the level of final pressure. The rate of further bubble growth and maximum bubble size depend on comparatively low effective nitrogen diffusivity in the cell layer, the tissue perfusion rate, the initial nitrogen tension in the tissue, and the final ambient pressure. The tissue deformation pressure performs its conservative action on bubble dynamics only in a limited volume of tissue (at a high density of formed bubbles). Our model is completely consistent with the available data concerning the random latency times to the onset of decompression sickness (DCS) symptoms associated with hypobaric decompressions simulating extravehicular activity. We believe that this model could be used as a theoretical basis for development of more adequate methods for the DCS risk prediction. PMID:10902936

  2. Mechanical Properties of Niobium Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; Myneni, Ganapati Rao

    2015-09-01

    The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

  3. 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

  4. Active cavity radiometer

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1981-01-01

    The active cavity radiometer (ACR) experiment on the Spacelab 1 mission to measure the total solar irradiance is discussed. Short and long term variations in the total solar output of optical energy are studied. Solar total irradiance observation provides 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. The interaction of solar radiation with the Earth's atmosphere, oceans, and land masses provides the primary driving forces for the formation of weather systems and the determination of climate. Astrophysical measurements determine the total energy flux. The principal role of the ACR observations support extended solar irradiance experiments on free flying satellites. Solar irradiance measurements are important in the establishment of the radiation scale at the solar total flux level in the international system of units (SI).

  5. 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...

  6. Frequency-feedback cavity enhanced spectrometer

    DOEpatents

    Hovde, David Christian; Gomez, Anthony

    2015-08-18

    A spectrometer comprising an optical cavity, a light source capable of producing light at one or more wavelengths transmitted by the cavity and with the light directed at the cavity, a detector and optics positioned to collect light transmitted by the cavity, feedback electronics causing oscillation of amplitude of the optical signal on the detector at a frequency that depends on cavity losses, and a sensor measuring the oscillation frequency to determine the cavity losses.

  7. Laser Scanner for Tile-Cavity Measurement

    NASA Technical Reports Server (NTRS)

    Yoshino, Stanley Y.; Wykes, Donald H.; Hagen, George R.; Lotgering, Gene E.; Gaynor, Michael B.; Westerlund, Paul G.; Baal, Thomas A.

    1987-01-01

    Irregular surfaces mapped and digitized for numerical-control machinery. Fast, accurate laser scanning system measures size and shape of cavity without making any physical contact with cavity and walls. Measurements processed into control signals for numerically controlled machining of tile or block to fit cavity. System generates map of grid points representing cavity and portion of outer surface surrounding cavity. Map data used to control milling machine, which cuts tile or block to fit in cavity.

  8. Master Equation for the Motion of a Polarizable Particle in a Multimode Cavity

    E-print Network

    Stefan Nimmrichter; Klemens Hammerer; Peter Asenbaum; Helmut Ritsch; Markus Arndt

    2010-06-16

    We derive a master equation for the motion of a polarizable particle weakly interacting with one or several strongly pumped cavity modes. We focus here on massive particles with complex internal structure such as large molecules and clusters, for which we assume a linear scalar polarizability mediating the particle-light interaction. The predicted friction and diffusion coefficients are in good agreement with former semiclassical calculations for atoms and small molecules in weakly pumped cavities, while the current rigorous quantum treatment and numerical assessment sheds a light on the feasibility of experiments that aim at optically manipulating beams of massive molecules with multimode cavities.

  9. Diffusion on Cu surfaces

    NASA Technical Reports Server (NTRS)

    Karimi, Majid

    1993-01-01

    Understanding surface diffusion is essential in understanding surface phenomena, such as crystal growth, thin film growth, corrosion, physisorption, and chemisorption. Because of its importance, various experimental and theoretical efforts have been directed to understand this phenomena. The Field Ion Microscope (FIM) has been the major experimental tool for studying surface diffusion. FIM have been employed by various research groups to study surface diffusion of adatoms. Because of limitations of the FIM, such studies are only limited to a few surfaces: nickel, platinum, aluminum, iridium, tungsten, and rhodium. From the theoretical standpoint, various atomistic simulations are performed to study surface diffusion. In most of these calculations the Embedded Atom Method (EAM) along with the molecular static (MS) simulation are utilized. The EAM is a semi-empirical approach for modeling the interatomic interactions. The MS simulation is a technique for minimizing the total energy of a system of particles with respect to the positions of its particles. One of the objectives of this work is to develop the EAM functions for Cu and use them in conjunction with the molecular static (MS) simulation to study diffusion of a Cu atom on a perfect as well as stepped Cu(100) surfaces. This will provide a test of the validity of the EAM functions on Cu(100) surface and near the stepped environments. In particular, we construct a terrace-ledge-kink (TLK) model and calculate the migration energies of an atom on a terrace, near a ledge site, near a kink site, and going over a descending step. We have also calculated formation energies of an atom on the bare surface, a vacancy in the surface, a stepped surface, and a stepped-kink surface. Our results are compared with the available experimental and theoretical results.

  10. Numerical and experimental study on flame structure characteristics in a supersonic combustor with dual-cavity

    NASA Astrophysics Data System (ADS)

    Yang, Yixin; Wang, Zhenguo; Sun, Mingbo; Wang, Hongbo; Li, Li

    2015-12-01

    Combined numerical and experimental approaches have been implemented to investigate the quasi-steady flame characteristics of supersonic combustion in tandem and parallel dual-cavity. In simulation, a hybrid Large Eddy Simulation (LES)/assumed sub-grid Probability Density Function (PDF) closure model was carried out. Comparison of calculation and experiment as well as comparison of the two configurations are qualitatively and quantitatively performed regarding the flame structure and other flowfield features. Simulation shows a good level of agreement with experimental observation and measurement in terms of instantaneous and time-averaged results. Given the same fuel equivalence ratio, the parallel dual-cavity with the two opposite injections gathers the major combustion around the cavities, thus leading to the concentrated heat release, the greatly extended recirculation zones and the converging-diverging core flow path. Only intermittent stray flame packets can be found in the downstream region. Flame in the combustor with tandem dual-cavity appears to be stabilized by the upstream cavity shear layer and grows gradually to the second cavity, peaking its most intensity in the middle section between the two cavities. For both dual-cavity configurations, the strongest reaction takes place in near chemistry stoichiometric region around the flame edge, and is mainly confined in the supersonic region supported by the inner subsonic combustion. The coexistence of three parts plays a vital role in flame stabilization in the parallel and tandem dual-cavity: a reacting reservoir transferring hot products and activated radicals within the cavity recirculation zone, the hydrogen-rich premixed flame in the jet mixing region, and the downstream diffusion flames supported by the upstream premixed combustion region. In addition, for the parallel dual-cavity under the given condition, significant reaction are present near jet exit upstream the cavity leading edge.

  11. Call for Papers: Cavity QED

    NASA Astrophysics Data System (ADS)

    Lange, W.; Gerard, J.-M.

    2003-06-01

    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 comprehensive account of the current state of the art of cavity QED by uniting contributions from researchers active across this field. As Guest Editors of this topical issue, we invite manuscripts on current theoretical and experimental work on any aspects of cavity QED. The topics to be covered will include, but are not limited to: bulletCavity QED in optical microcavities bulletSemiconductor cavity QED bulletQuantum dot cavity QED bulletRydberg atoms in microwave cavities bulletPhotonic crystal cavity QED bulletMicrosphere resonators bulletMicrolasers and micromasers bulletMicrodroplets bulletDielectric cavity QED bulletCavity QED-based quantum information processing bulletQuantum state engineering in cavities The DEADLINE for submission of contributions is 31 July 2003 to allow the topical issue to appear in about February 2004. All papers will be peer-reviewed in accordance with the normal refereeing procedures and standards of Journal of Optics B: Quantum and Semiclassical Optics. Advice on publishing your work in the journal may be found at www.iop.org/journals/authors/jopb. Submissions should ideally be in either standard LaTeX form or Microsoft Word. There are no page charges for publication. In addition to the usual 50 free reprints, the corresponding author of each paper published will receive a complimentary copy of the topical issue. Contributions to the topical issue should if possible be submitted electronically at www.iop.org/journals/jopb. or by e-mail to jopb@iop.org. Authors unable to submit online or by e-mail may send hard copy contributions (enclosing the electronic code) to: Dr Claire Bedrock (Publisher), Journal of Optics B: Quantum and Semiclassical Optics, Institute of Physics Publishing, Dirac House, Temple Back, Bristol BS1 6BE, UK. All contributions should be accompanied by a readme file or covering letter, quoting `JOPB topical issue - Cavity QED', giving the postal and e-mail addresses for correspondence. Any subsequent change of address should be notified to the publishing office. We look forward to receiving your contribution to this topical issue.

  12. 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

  13. 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...

  14. Sequential cavity use in a cottonwood bottomland

    USGS Publications Warehouse

    Sedgwick, J.A.

    1997-01-01

    I studied the patterns and frequency of cavity reuse in a community of cavity-nesting birds in a cottonwood bottomland along the South Platte River in northeastern Colorado from 1985-1987. Of 100 cavities occupied in 1985, 56% were mused in 1986; 38.5% of 122 cavities occupied in 1986 were mused in 1987. Of 81 old cavities monitored in both 1986 and 1987, 65.4% were reused at least once. Similar proportions of secondary cavity-nesting bird (SCNB) and primary cavity-nesting bird (PCNB) cavities were reused in both years. Reoccupancy by the same species was 27% and 20.5% in 1986 and 1987, respectively, and was greater for SCNB than for PCNB cavities in both years. Conversely, reoccupancy by different species was greater for PCNB than for SCNB cavities in both years, Thus, old cavities of PCNB were more available to other species of cavity-nesting birds, whereas old SCNB cavities tended to be reused by the same species that previously occupied the cavity. SCNB used a greater proportion of old cavities than did PCNB in both 1986 and 1987. House Wrens (Troglodytes aedon) and Northern Flickers (Colaptes auratus) reoccupied most of the old cavities.

  15. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and... DENTAL DEVICES Prosthetic Devices § 872.3260 Cavity varnish. (a) Identification. Cavity varnish is a device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  16. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and... DENTAL DEVICES Prosthetic Devices § 872.3260 Cavity varnish. (a) Identification. Cavity varnish is a device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  17. Electromagnetic Scattering from Large Cavities: Iterative Methods

    E-print Network

    New York at Stoney Brook, State University of

    Electromagnetic Scattering from Large Cavities: Iterative Methods J. S. Asvestas 27 Summit Street for the solution of electromagnetic scattering from a cavity, and show convergence using coarse grids which are two of monochromatic scattering by electrically large cavities in a perfectly conducting plane. Scattering by cavities

  18. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and... DENTAL DEVICES Prosthetic Devices § 872.3260 Cavity varnish. (a) Identification. Cavity varnish is a device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  19. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and... DENTAL DEVICES Prosthetic Devices § 872.3260 Cavity varnish. (a) Identification. Cavity varnish is a device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  20. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and... DENTAL DEVICES Prosthetic Devices § 872.3260 Cavity varnish. (a) Identification. Cavity varnish is a device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  1. Demonstrating Diffusion

    ERIC Educational Resources Information Center

    Foy, Barry G.

    1977-01-01

    Two demonstrations are described. Materials and instructions for demonstrating movement of molecules into cytoplasm using agar blocks, phenolphthalein, and sodium hydroxide are given. A simple method for demonstrating that the rate of diffusion of a gas is inversely proportional to its molecular weight is also presented. (AJ)

  2. Defusing Diffusion

    ERIC Educational Resources Information Center

    Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

    2013-01-01

    Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

  3. Theory of Bloch cavity solitons

    SciTech Connect

    Egorov, O. A.; Lederer, F.; Staliunas, K.

    2010-10-15

    We present a detailed study of light dynamics in passive nonlinear resonators with shallow intracavity periodic modulation of the refractive index in both longitudinal and transverse directions of the resonator. Specifically, we concentrate on the nonlinear envelopes of dissipative Bloch modes, localized in the transverse plane of the resonator, the so-called Bloch cavity solitons, predicted recently in K. Staliunas et al. [Phys. Rev. Lett. 101, 153903 (2008)]. Bloch cavity solitons, being dissipative structures, are attractors, therefore they can be excited from a wide range of initial conditions (the attractor basin) depending on the system's parameters. A unique property of Bloch cavity solitons is that they are envelopes of waves with tailored diffraction. Using the round-trip model for forward- and backward-propagating waves we reveal different types of Bloch cavity solitons supported by both focusing (at normal diffraction) and defocusing (at anomalous diffraction) nonlinearities. We show also the coexistence of solitons bifurcating from different Bloch wave dispersion branches. In order to analyze the properties of Bloch cavity solitons and to obtain an analytical access we develop a modified mean-field model and prove its validity. In particular, we demonstrate substantial narrowing of Bloch cavity solitons near the zero-diffraction regime.

  4. Water vapor permeabilities through polymers: diffusivities from experiments and simulations

    NASA Astrophysics Data System (ADS)

    Seethamraju, Sindhu; Chandrashekarapura Ramamurthy, Praveen; Madras, Giridhar

    2014-09-01

    This study experimentally determines water vapor permeabilities, which are subsequently correlated with the diffusivities obtained from simulations. Molecular dynamics (MD) simulations were used for determining the diffusion of water vapor in various polymeric systems such as polyethylene, polypropylene, poly (vinyl alcohol), poly (vinyl acetate), poly (vinyl butyral), poly (vinylidene chloride), poly (vinyl chloride) and poly (methyl methacrylate). Cavity ring down spectroscopy (CRDS) based methodology has been used to determine the water vapor transmission rates. These values were then used to calculate the diffusion coefficients for water vapor through these polymers. A comparative analysis is provided for diffusivities calculated from CRDS and MD based results by correlating the free volumes.

  5. Nonlinear Diffusion. Porous Medium and Fast Diffusion.

    E-print Network

    Moroz, Vitaly

    Nonlinear Diffusion. Porous Medium and Fast Diffusion. From Analysis to Physics and Geometry Juan Swansea, July 2008 Juan L. V´azquez - Nonlinear Diffusion. Porous Medium and Fast Diffusion Equations ­ p. 1/?? #12;Introduction Main topic after 1981: Nonlinear Diffusion Juan L. V´azquez - Nonlinear

  6. An inductively heated hot cavity catcher laser ion source.

    PubMed

    Reponen, M; Moore, I D; Pohjalainen, I; Rothe, S; Savonen, M; Sonnenschein, V; Voss, A

    2015-12-01

    An inductively heated hot cavity catcher has been constructed for the production of low-energy ion beams of exotic, neutron-deficient Ag isotopes. A proof-of-principle experiment has been realized by implanting primary (107)Ag(21+) ions from a heavy-ion cyclotron into a graphite catcher. A variable-thickness nickel foil was used to degrade the energy of the primary beam in order to mimic the implantation depth expected from the heavy-ion fusion-evaporation recoils of N = Z (94)Ag. Following implantation, the silver atoms diffused out of the graphite and effused into the catcher cavity and transfer tube, where they were resonantly laser ionized using a three-step excitation and ionization scheme. Following mass separation, the ions were identified by scanning the frequency of the first resonant excitation step while recording the ion count rate. Ion release time profiles were measured for different implantation depths and cavity temperatures with the mean delay time varying from 10 to 600 ms. In addition, the diffusion coefficients for silver in graphite were measured for temperatures of 1470 K, 1630 K, and 1720 K, from which an activation energy of 3.2 ± 0.3 eV could be determined. PMID:26724021

  7. 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.

  8. Normal Conducting RF Cavity for MICE

    SciTech Connect

    Li, D.; DeMello, A.; Virostek, S.; Zisman, M.; Summers, D.

    2010-05-23

    Normal conducting RF cavities must be used for the cooling section of the international Muon Ionization Cooling Experiment (MICE), currently under construction at Rutherford Appleton Laboratory (RAL) in the UK. Eight 201-MHz cavities are needed for the MICE cooling section; fabrication of the first five cavities is complete. We report the cavity fabrication status including cavity design, fabrication techniques and preliminary low power RF measurements.

  9. Diffuse interstellar bands in reflection nebulae

    NASA Technical Reports Server (NTRS)

    Fischer, O.; Henning, Thomas; Pfau, Werner; Stognienko, R.

    1994-01-01

    A Monte Carlo code for radiation transport calculations is used to compare the profiles of the lambda lambda 5780 and 6613 Angstrom diffuse interstellar bands in the transmitted and the reflected light of a star embedded within an optically thin dust cloud. In addition, the behavior of polarization across the bands were calculated. The wavelength dependent complex indices of refraction across the bands were derived from the embedded cavity model. In view of the existence of different families of diffuse interstellar bands the question of other parameters of influence is addressed in short.

  10. III-nitride tunable cup-cavities supporting quasi whispering gallery modes from ultraviolet to infrared.

    PubMed

    Shubina, T V; Pozina, G; Jmerik, V N; Davydov, V Yu; Hemmingsson, C; Andrianov, A V; Kazanov, D R; Ivanov, S V

    2015-01-01

    Rapidly developing nanophotonics needs microresonators for different spectral ranges, formed by chip-compatible technologies. In addition, the tunable ones are much in demand. Here, we present site-controlled III-nitride monocrystal cup-cavities grown by molecular beam epitaxy. The cup-cavities can operate from ultraviolet to near-infrared, supporting quasi whispering gallery modes up to room temperature. Besides, their energies are identical in large 'ripened' crystals. In these cavities, the refractive index variation near an absorption edge causes the remarkable effect of mode switching, which is accompanied by the spatial redistribution of electric field intensity with concentration of light into a subwavelength volume. Our results shed light on the mode behavior in semiconductor cavities and open the way for single-growth-run manufacturing the devices comprising an active region and a cavity with tunable mode frequencies. PMID:26656267

  11. 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.; Napoly, O.; Paparella, R.; 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.

  12. III-nitride tunable cup-cavities supporting quasi whispering gallery modes from ultraviolet to infrared

    PubMed Central

    Shubina, T. V.; Pozina, G.; Jmerik, V. N.; Davydov, V. Yu.; Hemmingsson, C.; Andrianov, A. V.; Kazanov, D. R.; Ivanov, S. V.

    2015-01-01

    Rapidly developing nanophotonics needs microresonators for different spectral ranges, formed by chip-compatible technologies. In addition, the tunable ones are much in demand. Here, we present site-controlled III-nitride monocrystal cup-cavities grown by molecular beam epitaxy. The cup-cavities can operate from ultraviolet to near-infrared, supporting quasi whispering gallery modes up to room temperature. Besides, their energies are identical in large ’ripened’ crystals. In these cavities, the refractive index variation near an absorption edge causes the remarkable effect of mode switching, which is accompanied by the spatial redistribution of electric field intensity with concentration of light into a subwavelength volume. Our results shed light on the mode behavior in semiconductor cavities and open the way for single-growth-run manufacturing the devices comprising an active region and a cavity with tunable mode frequencies. PMID:26656267

  13. Extended cavity surface-emitting semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Tropper, A. C.; Hoogland, S.

    We review progress in the development of an unconventional type of semiconductor laser that has become the focus of much attention in recent years. The vertical-external-cavity surface-emitting laser is a diode-pumped solid-state laser with a semiconductor quantum well gain medium. It overcomes the limitation of conventional edge- and surface-emitting semiconductor lasers, which can offer either diffraction-limited beam quality, or high power, but not both in the same device. In this paper, we describe the physical principles of these lasers, emphasising those aspects that are unique to this hybrid. Optical characterisation of gain wafers is discussed, with particular attention to photoluminescence measurement; a powerful tool for the analysis of growth errors, the quantum efficiency of the active region, and the effect of multilayer interference effects on laser performance. Key achievements in the field to date, in high-power performance, ultrashort-pulse generation, and spectral coverage are summarised.

  14. Electrostatic interactions in the channel cavity as an important determinant of potassium

    E-print Network

    Grabe, Michael

    Electrostatic interactions in the channel cavity as an important determinant of potassium channel by Lily Yeh Jan, August 2, 2006 Potassium channels are membrane proteins that allow the passage of potassium ions at near diffusion rates while severely limiting the flux of the slightly smaller sodium ions

  15. 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

  16. The ESS elliptical cavity cryomodules

    SciTech Connect

    Darve, Christine; Bosland, Pierre; Devanz, Guillaume; Renard, Bertrand; Olivier, Gilles; Thermeau, Jean-Pierre

    2014-01-29

    The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today’s leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. The superconducting section of the Linac accelerates the beam from 80 MeV to 2.0 GeV. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. These cryomodules contain four elliptical Niobium cavities operating at 2 K and at a frequency of 704.42 MHz. This paper introduces the thermo-mechanical design, the prototyping and the expected operation of the ESS elliptical cavity cryomodules. An Elliptical Cavity Cryomodule Technology Demonstrator (ECCTD) will be built and tested in order to validate the ESS series production.

  17. The ESS spoke cavity cryomodules

    SciTech Connect

    Bousson, Sebastien; Duthil, Patxi; Reynet, Denis; Thermeau, Jean-Pierre

    2014-01-29

    The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today’s leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. This paper introduces the thermo-mechanical design and expected operation of the ESS spoke cavity cryomodules. These cryomodules contain two double spoke bulk Niobium cavities operating at 2 K and at a frequency of 352.21 MHz. The superconducting section of the Spoke Linac accelerates the beam from 90 MeV to 220 MeV. A Spoke Cavity Cryomodule Technology Demonstrator will be built and tested in order to validate the ESS series production.

  18. Hidden Sector Photon Coupling of Resonant Cavities

    E-print Network

    Stephen R. Parker; Gray Rybka; Michael E. Tobar

    2013-04-25

    Many beyond the standard model theories introduce light paraphotons, a hypothetical spin-1 field that kinetically mixes with photons. Microwave cavity experiments have traditionally searched for paraphotons via transmission of power from an actively driven cavity to a passive receiver cavity, with the two cavities separated by a barrier that is impenetrable to photons. We extend this measurement technique to account for two-way coupling between the cavities and show that the presence of a paraphoton field can alter the resonant frequencies of the coupled cavity pair. We propose an experiment that exploits this effect and uses measurements of a cavities resonant frequency to constrain the paraphoton-photon mixing parameter, chi. We show that such an experiment can improve sensitivity to chi over existing experiments for paraphoton masses less than the resonant frequency of the cavity, and eliminate some of the most common systematics for resonant cavity experiments.

  19. Ion Channels and Amino Acid Transporters Support the Growth and Invasion of Primary Brain Tumors

    PubMed Central

    Sontheimer, Harald

    2008-01-01

    The malignant growth of glial support cells causes gliomas, highly invasive, primary brain tumors that are largely resistant to therapy. Individual tumor cells spread by active cell migration, invading diffusely into the normal brain. This process is facilitated by Cl- channels that endow glioma cells with an enhanced ability to quickly adjust their shape and cell volume to fit the narrow and tortuous extracellular brain spaces. Once satellite tumors enlarge, their growth is limited by the spatial constraints imposed by the bony cavity of the skull and spinal column. Glioma cells circumvent this limitation by active destruction of peritumoral neural tissue through the release of glutamate, inducing peritumoral seizures and ultimately excitotoxic neuronal cell death. Hence, primary brain tumors support their unusual biology by taking advantage of ion channels and transporters that are designed to support ion homeostatic functions in normal brain. PMID:15034223

  20. 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.

  1. Vacuum effects in a vibrating cavity: time refraction, dynamical Casimir effect, and effective Unruh acceleration

    E-print Network

    J. T. Mendonca; G. Brodin; M. Marklund

    2008-06-04

    Two different quantum processes are considered in a perturbed vacuum cavity: time refraction and dynamical Casimir effect. They are shown to be physically equivalent, and are predicted to be unstable, leading to an exponential growth in the number of photons created in the cavity. The concept of an effective Unruh acceleration for these processes is also introduced, in order to make a comparison in terms of radiation efficiency, with the Unruh radiation associated with an accelerated frame in unbounded vacuum.

  2. Juvenile Nasopharyngeal Angiofibroma Extending into the Oral Cavity: A Rare Entity.

    PubMed

    Pardhe, Nilesh; Chhibber, Neha; Agarwal, Deshant; Jain, Manish; Vijay, Pradkhshana

    2015-06-01

    Juvenile nasopharyngeal angiofibroma (JNA) is a rare vascular tumour which is benign but locally aggressive and occurs invariably in young and adolescent males. It seldom involves the oral cavity but has the tendency to invade the adjacent structures. Its characteristic features include slow progression, aggressive growth & an increased rate of persistence and recurrence due to its location in inaccessible areas. In literature, very few cases of JNA have been reported with extension into the oral cavity. Here, a case of JNA with extension into the oral cavity has been discussed who reported to our institute. PMID:26266232

  3. Juvenile Nasopharyngeal Angiofibroma Extending into the Oral Cavity: A Rare Entity

    PubMed Central

    Chhibber, Neha; Agarwal, Deshant; Jain, Manish; Vijay, Pradkhshana

    2015-01-01

    Juvenile nasopharyngeal angiofibroma (JNA) is a rare vascular tumour which is benign but locally aggressive and occurs invariably in young and adolescent males. It seldom involves the oral cavity but has the tendency to invade the adjacent structures. Its characteristic features include slow progression, aggressive growth & an increased rate of persistence and recurrence due to its location in inaccessible areas. In literature, very few cases of JNA have been reported with extension into the oral cavity. Here, a case of JNA with extension into the oral cavity has been discussed who reported to our institute. PMID:26266232

  4. RRR Characteristics for SRF Cavities

    E-print Network

    Jung, Yoochul; Joung, Mijoung

    2015-01-01

    The first heavy ion accelerator is being constructed by the rare isotope science project (RISP) launched by the Institute of Basic Science (IBS) in South Korea. Four different types of superconducting cavities were designed, and prototypes were fabricated such as a quarter wave resonator (QWR), a half wave resonator (HWR) and a single spoke resonator (SSR). One of the critical factors determining performances of the superconducting cavities is a residual resistance ratio (RRR). The RRR values essentially represent how much niobium is pure and how fast niobium can transmit heat as well. In general, the RRR degrades during electron beam welding due to the impurity incorporation. Thus it is important to maintain RRR above a certain value at which a niobium cavity shows target performance. In this study, RRR degradation related with electron beam welding conditions, for example, welding power, welding speed, and vacuum level will be discussed.

  5. RRR Characteristics for SRF cavities

    NASA Astrophysics Data System (ADS)

    Jung, Yoochul; Hyun, Myungook; Joung, Mijoung

    2015-10-01

    The first heavy ion accelerator is being constructed by the rare isotope science project (RISP) launched by the Institute of Basic Science (IBS) in South Korea. Four different types of superconducting cavities were designed, and prototypes such as a quarter-wave resonator (QWR), a half-wave resonator (HWR) and a single-spoke resonator (SSR) were fabricated. One of the critical factors determining the performances of superconducting cavities is the residual resistance ratio (RRR). The RRR values essentially represent how pure niobium is and how fast niobium can transmit heat. In general, the RRR degrades during electron beam welding due to impurity incorporation. Thus, it is important to maintain the RRR above a certain value at which a niobium cavity shows target performance. In this study, RRR degradation related with electron beam welding conditions, for example, the welding power, welding speed, and vacuum level, will be discussed.

  6. Cavity enhanced transport of excitons

    E-print Network

    Johannes Schachenmayer; Claudiu Genes; Edoardo Tignone; Guido Pupillo

    2015-05-20

    We show that exciton-type transport in certain materials can be dramatically modified by their inclusion in an optical cavity: the modification of the electromagnetic vacuum mode structure introduced by the cavity leads to transport via delocalized polariton modes rather than through tunneling processes in the material itself. This can help overcome exponential suppression of transmission properties as a function of the system size in the case of disorder and other imperfections. We exemplify massive improvement of transmission for excitonic wave-packets through a cavity, as well as enhancement of steady-state exciton currents under incoherent pumping. These results may have implications for experiments of exciton transport in disordered organic materials. We propose that the basic phenomena can be observed in quantum simulators made of Rydberg atoms, cold molecules in optical lattices, as well as in experiments with trapped ions.

  7. 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.

  8. Cavity-water interface is polar

    E-print Network

    Allan D. Friesen; Dmitry V. Matyushov

    2010-05-20

    We present the results of numerical simulations of the electrostatics and dynamics of water hydration shells surrounding Kihara cavities given by a Lennard-Jones (LJ) layer at the surface of a hard-sphere cavity. The local dielectric response of the hydration layer substantially exceeds that of bulk water, with the magnitude of the dielectric constant peak in the shell increasing with the growing cavity size. The polar shell propagates into bulk water to approximately the cavity radius. The statistics of the electrostatic field produced by water inside the cavity follow linear response and approach the prediction of continuum electrostatics with increasing cavity size.

  9. 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.

  10. 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.

  11. Progress on a Be Cavity Design

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    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.

  12. Optical modeling of certical-cavity surface-emitting lasers

    SciTech Connect

    Hadley, G.R.

    1996-12-31

    Vertical-cavity surface-emitting lasers (VCSELs) are presently the subject of intense research due to their potential as compact, efficient, astigmatic laser sources for a number of important applications. Of special interest are the selectively-oxidized VCSELs that have recently set records for threshold current and wall-plug efficiency. The onset of higher-order modes at powers of a few milliWatts, however, presently limits the wide utilization of these devices and indicates the need for improvements in design. Unfortunately, their complexity precludes optimization based solely upon empirical methods, and points instead to the need for better numerical models. Modeling the optical field in a vertical-cavity laser, however, is especially difficult due to both the high Q of the optical cavity and the distributed reflectivity of the mirrors. Our approach to this dilemma has been the development of modeling techniques on two complexity scales. We first derived an effective- index model that is numerically efficient and thus can be included together with carrier transport and thermal models to make up a self-consistent modeling package. In addition to its use in the overall VCSEL model, this simplified optical model has been extremely valuable in elucidating the basic principles of waveguiding in VCSELs that in turn have led to new ideas in device design. More specifically, the derived expression for the effective index shows clearly that index guiding in a VCSEL depends only on variations in optical cavity length, and thus can be engineered without the need to alter the material index of refraction. Also, we have designed index- guided and antiguided devices whose cavity lengths are modified in certain regions by etching of the cavity material prior to growth of the second mirror. Fabrication of these new device designs is presently in progress.

  13. Diffusion bonding

    NASA Astrophysics Data System (ADS)

    Brown, L. E.

    1993-03-01

    A temperature between 400 and 500 and a pressure between 40 MPa and 160 MPa were indicated by a two-factor, three-level factorial experiment for diffusion bonding of molybdenum sheet substrates. These substrates were sputter ion plated with palladium (0.5 microns) and silver (10 microns) films on the mating surfaces, with the silver used as a bonding interlayer. The palladium acted as an adhesive layer between the silver film and molybdenum substrate. The silver diffusion bonds that resulted were qualitatively characterized at the interfacial regions, and bonds with no visible interface were obtained at 7500X magnification. Correlations were obtained for voids found optically at the silver/silver bonding interface and colored image maps, illustrating bond quality, produced by nondestructive ultrasonic imaging. Above 160 MPa, the bonding process produces samples with a nonuniform load distribution. These samples contained regions with gaps and well-bonded regions at the silver/silver interface, and all had macroscopic deformation of the silver films.

  14. Generalized magneto-thermoviscoelasticity in a perfectly conducting thermodiffusive medium with a spherical cavity

    NASA Astrophysics Data System (ADS)

    Zenkour, Ashraf M.; Alzahrani, Ebraheem O.; Abouelregal, Ahmed E.

    2015-11-01

    In this work, the effects of viscosity and diffusion on thermoelastic interactions in an infinite medium with a spherical cavity are studied. The formulation is applied to the generalized thermoelasticity based on the theory of generalized thermoelastic diffusion with one relaxation time. The surface of the spherical cavity is taken to be traction free and subjected to both heating and external constant magnetic field. The solution is obtained in the Laplace transform domain by using a direct approach. The solution of the problem in the physical domain obtained numerically using a method based on Fourier expansion techniques. The temperature, displacement, stress, concentration as well as the chemical potential are obtained and represented graphically. Comparisons are made within the theory in the presence and absence of viscosity and diffusion.

  15. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3260 Cavity varnish. (a) Identification. Cavity varnish is a device that consists of a...

  16. Optical cavity furnace for semiconductor wafer processing

    DOEpatents

    Sopori, Bhushan L.

    2014-08-05

    An optical cavity furnace 10 having multiple optical energy sources 12 associated with an optical cavity 18 of the furnace. The multiple optical energy sources 12 may be lamps or other devices suitable for producing an appropriate level of optical energy. The optical cavity furnace 10 may also include one or more reflectors 14 and one or more walls 16 associated with the optical energy sources 12 such that the reflectors 14 and walls 16 define the optical cavity 18. The walls 16 may have any desired configuration or shape to enhance operation of the furnace as an optical cavity 18. The optical energy sources 12 may be positioned at any location with respect to the reflectors 14 and walls defining the optical cavity. The optical cavity furnace 10 may further include a semiconductor wafer transport system 22 for transporting one or more semiconductor wafers 20 through the optical cavity.

  17. Facing rim cavities fluctuation modes

    NASA Astrophysics Data System (ADS)

    Casalino, Damiano; Ribeiro, André F. P.; Fares, Ehab

    2014-06-01

    Cavity modes taking place in the rims of two opposite wheels are investigated through Lattice-Boltzmann CFD simulations. Based on previous observations carried out by the authors during the BANC-II/LAGOON landing gear aeroacoustic study, a resonance mode can take place in the volume between the wheels of a two-wheel landing gear, involving a coupling between shear-layer vortical fluctuations and acoustic modes resulting from the combination of round cavity modes and wheel-to-wheel transversal acoustic modes. As a result, side force fluctuations and tonal noise side radiation take place. A parametric study of the cavity mode properties is carried out in the present work by varying the distance between the wheels. Moreover, the effects due to the presence of the axle are investigated by removing the axle from the two-wheel assembly. The azimuthal properties of the modes are scrutinized by filtering the unsteady flow in narrow bands around the tonal frequencies and investigating the azimuthal structure of the filtered fluctuation modes. Estimation of the tone frequencies with an ad hoc proposed analytical formula confirms the observed modal properties of the filtered unsteady flow solutions. The present study constitutes a primary step in the description of facing rim cavity modes as a possible source of landing gear tonal noise.

  18. Fibre ring cavity semiconductor laser

    SciTech Connect

    Duraev, V P; Medvedev, S V

    2013-10-31

    This paper presents a study of semiconductor lasers having a polarisation maintaining fibre ring cavity. We examine the operating principle and report main characteristics of a semiconductor ring laser, in particular in single- and multiple-frequency regimes, and discuss its application areas. (lasers)

  19. Cavity pattern formation with incoherent light.

    PubMed

    Buljan, Hrvoje; Soljaci?, Marin; Carmon, Tal; Segev, Mordechai

    2003-07-01

    We study the propagation dynamics of an incoherent light beam circulating in a passive cavity containing noninstantaneous nonlinear media. It is shown that patterns form in this cavity in spite of spatial incoherence of the light. We show that the pattern formation process is always associated with two consecutive thresholds. The first (instability) threshold is unaffected by the cavity boundary conditions, whereas the second threshold is induced by the feedback through the interplay of nonlinear gain and cavity loss. PMID:12935279

  20. Electrostatic modeling of cavities inside linear actuators

    NASA Astrophysics Data System (ADS)

    van Beek, T. A.; Jansen, J. W.; van Duivenbode, J.; Lomonova, E. A.

    2015-10-01

    This paper describes the modeling of two-dimensional electric fields inside linear actuators where cavities in the cooling environment are present. A semi-analytical model based on Fourier series is extended for cavities and incorporates the curvature of corners. The model shows good agreement with finite element analysis. The effect of position and sizes of the cavity are investigated as well as the curvature of the corners of the cavity.

  1. 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.

  2. Many-atom-cavity QED system with homogeneous atom-cavity coupling.

    PubMed

    Lee, Jongmin; Vrijsen, Geert; Teper, Igor; Hosten, Onur; Kasevich, Mark A

    2014-07-01

    We demonstrate a many-atom-cavity system with a high-finesse dual-wavelength standing wave cavity in which all participating rubidium atoms are nearly identically coupled to a 780-nm cavity mode. This homogeneous coupling is enforced by a one-dimensional optical lattice formed by the field of a 1560-nm cavity mode. PMID:24978793

  3. Discrete Vapour Cavity Model with Improved Timing of Opening and Collapse of Cavities

    E-print Network

    Eindhoven, Technische Universiteit

    1 Discrete Vapour Cavity Model with Improved Timing of Opening and Collapse of Cavities Anton to the vapour pressure. Cavitation may occur as a localized vapour cavity (large void fraction) or as distributed vaporous cavitation (small void fraction). The discrete vapour cavity model (DVCM) with steady

  4. 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.

  5. Fabrication of Niobium sheet for RF cavities 

    E-print Network

    Balachandran, Shreyas

    2009-05-15

    on the particle inside the cavity[28]. b. A five cell cavity, Courtesy:Cornell-LEPP [28].............................................................. 19 Figure 10 Variation of surface resistance with frequency of various... . superconducting materials at frequencies typical to that of RF cavities in comparison with Cu at 77 and 300K. Nb has low surface resistance in the operating range of 1GHz among...

  6. Active-cavity radiometer/pyroheliometer

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1977-01-01

    Device, using specular black cavity heater, temperature sensors, and electronics and electrodeposited cavity/thermal impedance structures, can achieve + or - 0.1 percent long-term absolute uncertainty at solar constant level. Dual-cavity configuration helps decrease sensitivity for heat-sink temperature drift.

  7. Photonic crystal cavities and integrated optical devices

    NASA Astrophysics Data System (ADS)

    Gan, Lin; Li, ZhiYuan

    2015-11-01

    This paper gives a brief introduction to our recent works on photonic crystal (PhC) cavities and related integrated optical structures and devices. Theoretical background and numerical methods for simulation of PhC cavities are first presented. Based on the theoretical basis, two relevant quantities, the cavity mode volume and the quality factor are discussed. Then the methods of fabrication and characterization of silicon PhC slab cavities are introduced. Several types of PhC cavities are presented, such as the usual L3 missing-hole cavity, the new concept waveguide-like parallel-hetero cavity, and the low-index nanobeam cavity. The advantages and disadvantages of each type of cavity are discussed. This will help the readers to decide which type of PhC cavities to use in particular applications. Furthermore, several integrated optical devices based on PhC cavities, such as optical filters, channel-drop filters, optical switches, and optical logic gates are described in both the working principle and operation characteristics. These devices designed and realized in our group demonstrate the wide range of applications of PhC cavities and offer possible solutions to some integrated optical problems.

  8. Stent hypersensitivity and infection in sinus cavities

    PubMed Central

    Soufras, George D.; Hahalis, George

    2013-01-01

    Persistent mucosal inflammation, granulation tissue formation, hypersensitivity, and multifactorial infection are newly described complications of retained drug-eluting stents from endoscopic sinus surgery for refractory rhinosinusitis. In an important report published in Allergy and Rhinology, a 45-year-old male patient suffering from recalcitrant chronic rhinosinusitis underwent functional endoscopic sinus surgery and was found, for the first time, to have steroid-eluting catheters that were inadvertently left in the ethmoid and frontal sinuses. The retained catheters had caused persistent mucosal inflammation and formation of granulation tissue denoting hypersensitivity reaction. These consequences had induced perpetuation of symptoms of chronic rhinosinusitis. Meticulous removal of the retained stents with the nitinol wings from inflamed tissues of the frontal, ethmoidal, and sphenoethmoidal recesses in which they were completely imbedded was successfully performed without polypoid regrowth. Cultures of specimens taken from both left and right stents showed heavy growth of Stenotrophomonas maltophilia and moderate growth of Klebsiella oxytoca, coagulase negative Staphylococcus, and beta-hemolytic Streptococcus anginosus. Fungal infection was not detected. The current knowledge and experience regarding stent hypersensitivity and infection in relation with the use of stents in sinus cavities is reviewed. PMID:24498522

  9. Dynamics of an oscillating turbulent jet in a confined cavity

    NASA Astrophysics Data System (ADS)

    Righolt, B. W.; Kenjereš, S.; Kalter, R.; Tummers, M. J.; Kleijn, C. R.

    2015-09-01

    We demonstrate how the self-sustained oscillation of a confined jet in a thin cavity can be quantitatively described by a zero-dimensional model of the delay differential equation type with two a priori predicted model constants. This model describes the three phases in self-sustained oscillations: (i) pressure driven growth of the oscillation, (ii) amplitude limitation by geometry, and (iii) delayed destruction of the recirculation zone. The two parameters of the model are the growth rate of the jet angle by a pressure imbalance and the delay time for the destruction of this pressure imbalance. We present closed relations for both model constants as a function of the jet Reynolds number Re, the inlet velocity vin, the cavity width W, and the cavity width over inlet diameter W/d and we demonstrate that these model constants do not depend on other geometric ratios. The model and the obtained model constants have been successfully validated against three dimensional large eddy simulations, and planar particle image velocimetry measurements, for 1600 < Re ? 7100 and 20 ? W/d < 50. The presented model inherently contains the transition to a non-oscillating mode for decreasing Reynolds numbers or increasing W/d-ratios and allows for the quantitative prediction of the corresponding critical Reynolds number and critical W/d.

  10. Cavity varnish and cavity liner appearance on enamel and dentin.

    PubMed

    Tveit, A B; Riordan, P J; Olsen, H C

    1985-02-01

    To study the appearance of a cavity varnish and a cavity liner on prepared enamel and dentin surfaces, longitudinal tooth sections were coated once or twice with Copalite or Tubulitec. Some test specimens were immersed in saline solution for 24 hours, while others were kept in air. They were observed in SEM, and the degree of coverage of the test surfaces, and the smoothness of the materials were evaluated. Neither material provided complete coverage whether one or two layers were applied. Tubulitec seemed to be partially dissolved after immersion in saline solution. Generally, Copalite covered the surfaces better and was smoother than Tubulitec. These findings have implications in regard to the ability of the materials to protect the underlying tissues and to prevent microleakage, which were discussed. PMID:3856658

  11. Status of the ILC Crab Cavity Development

    SciTech Connect

    Burt, G.; Dexter, A.; Beard, C.; Goudket, P.; McIntosh, P.; Bellantoni, L.; 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.

  12. Primary Diffuse Large B-cell Lymphoma involving the Mandible.

    PubMed

    Alshahrani, Faleh Ali A; Aljabab, Abdulsalam S; Motabi, Ibraheem Hm; Alrashed, Abdullah; Anil, Sukumaran

    2015-01-01

    Lymphomas of the oral cavity are rare and typically present as intraosseous lesions that are most commonly diffuse large B-cell type. Diffuse large B-cell lymphoma (DLBCL) is an aggressive B-cell lymphoma histologically characterized by diffuse proliferation of large neoplastic B-lymphoid cells with a nuclear size equal to or exceeding normal histiocytic nuclei. A case of DLBCL of the mandible in an 18 years old male patient is presented. This report discusses this rare malignancy, including clinical presentation, histopathologic features, immunologic profile, treatment and prognosis. Though lymphoma of mandible is rare, it must be considered in differential diagnosis of swellings arising in the region. PMID:26581467

  13. 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

  14. 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

  15. Protein crystal growth - Growth kinetics for tetragonal lysozyme crystals

    NASA Technical Reports Server (NTRS)

    Pusey, M. L.; Snyder, R. S.; Naumann, R.

    1986-01-01

    Results are reported from theoretical and experimental studies of the growth rate of lysozyme as a function of diffusion in earth-gravity conditions. The investigations were carried out to form a comparison database for future studies of protein crystal growth in the microgravity environment of space. A diffusion-convection model is presented for predicting crystal growth rates in the presence of solutal concentration gradients. Techniques used to grow and monitor the growth of hen egg white lysozyme are detailed. The model calculations and experiment data are employed to discuss the effects of transport and interfacial kinetics in the growth of the crystals, which gradually diminished the free energy in the growth solution. Density gradient-driven convection, caused by presence of the gravity field, was a limiting factor in the growth rate.

  16. Cavity Enhanced Velocity Modulation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Siller, Brian; Mills, Andrew; Porambo, Michael; McCall, Benjamin

    2010-11-01

    Over the past several decades, velocity modulation spectroscopy has been used to study dozens of molecular ions of astronomical importance. This technique has been so productive because it provides the advantage of ion-neutral discrimination, which is critically important when interfering neutral molecules are many orders of magnitude more abundant, and when combined with heterodyne techniques, its sensitivity can approach the shot noise limit. Traditionally, velocity modulation experiments have utilized unidirectional multipass White cells to achieve up to about 8 passes through a positive column discharge cell. But by positioning the cell within an optical cavity, it is possible to obtain an effective path length orders of magnitude longer than was previously possible. We have demonstrated this novel technique using a Ti:Sapp laser in the near-IR to observe rovibronic transitions of N2+. By demodulating at twice the modulation frequency, 2nd derivative-like lineshapes are observed for ions that are velocity-modulated, while Gaussian lineshapes are observed for excited neutral that are concentration-modulated. The signals for N2+ and N2+* have been observed to be 78° out of phase with one another, so ion-neutral discrimination is retained. And due to the laser power enhancement and geometry of the optical cavity, Doppler-free saturation spectroscopy is now possible. Observed Lamb dips have widths of 50 MHz, and when combined with calibration by an optical frequency comb, this allows for determination of line centers to within 1 MHz. In our original demonstration of this technique, our sensitivity was limited by noise in the laser-cavity lock. Since then, we have integrated Noise Immune Cavity Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS) by adding sidebands to the laser at an exact multiple of the cavity free spectral range, and demodulating at the sideband frequency before sending the signal to a lock-in amplifier for demodulating at twice the plasma frequency. This has greatly reduced the noise and increased the sensitivity of cavity enhanced velocity modulation spectroscopy.

  17. LHC crab-cavity aspects and strategy

    SciTech Connect

    Calaga, R.; Tomas, R.; Zimmermann, F.

    2010-05-23

    The 3rd LHC Crab Cavity workshop (LHC-CC09) took place at CERN in October 2009. It reviewed the current status and identified a clear strategy towards a future crab-cavity implementation. Following the success of crab cavities in KEK-B and the strong potential for luminosity gain and leveling, CERN will pursue crab crossing for the LHC upgrade. We present a summary and outcome of the variousworkshop sessions which have led to the LHC crab-cavity strategy, covering topics like layout, cavity design, integration, machine protection, and a potential validation test in the SPS.

  18. 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.

  19. Low-lying bifurcations in cavity quantum electrodynamics

    SciTech Connect

    Armen, M. A.; Mabuchi, H.

    2006-06-15

    The interplay of quantum fluctuations with nonlinear dynamics is a central topic in the study of open quantum systems, connected to fundamental issues (such as decoherence and the quantum-classical transition) and practical applications (such as coherent information processing and the development of mesoscopic sensors and amplifiers). With this context in mind, we here present a computational study of some elementary bifurcations that occur in a driven and damped cavity quantum electrodynamics (cavity QED) model at low intracavity photon number. In particular, we utilize the single-atom cavity QED master equation and associated stochastic Schroedinger equations to characterize the equilibrium distribution and dynamical behavior of the quantized intracavity optical field in parameter regimes near points in the semiclassical (mean-field, Maxwell-Bloch) bifurcation set. Our numerical results show that the semiclassical limit sets are qualitatively preserved in the quantum stationary states, although quantum fluctuations apparently induce phase diffusion within periodic orbits and stochastic transitions between attractors. We restrict our attention to an experimentally realistic parameter regime.

  20. Novel Geometries for the LHC Crab Cavity

    SciTech Connect

    B. Hall, G. Burt, J.D.A. Smith, R. Rimmer, H. Wang, J. Delayen, R. Calaga

    2009-05-01

    In 2017 the LHC is envisioned to increase its luminosity via an upgrade. This upgrade is likely to require a large crossing angle hence a crab cavity is required to align the bunches prior to collision. There are two possible schemes for crab cavity implementation, global and local. In a global crab cavity the crab cavity is far from the IP and the bunch rotates back and forward as it traverses around the accelerator in a closed orbit. For this scheme a two-cell elliptical squashed cavity at 800 MHz is preferred. To avoid any potential beam instabilities all the parasitic modes of the cavities must be damped strongly, however crab cavities have lower order and same order modes in addition to the usual higher order modes and hence a novel damping scheme must be used to provide sufficient damping of these modes. In the local scheme two crab cavities are placed at each side of the IP two start and stop rotation of the bunches. This would require crab cavities much smaller transversely than in the global scheme but the frequency cannot be increased any higher due to the long bunch length of the LHC beam. This will require a novel compact crab cavity design. A superconducting version of a two rod coaxial deflecting cavity as a suitable design is proposed in this paper.

  1. 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.

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

    SciTech Connect

    Thyrrestrup, Henri Yüce, Emre; Ctistis, Georgios; Vos, Willem L.; Claudon, Julien; Gérard, Jean-Michel

    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.

  3. Optical Devices Based on Limit Cycles and Amplification in Semiconductor Optical Cavities

    NASA Astrophysics Data System (ADS)

    Hamerly, Ryan; Mabuchi, Hideo

    2015-08-01

    At strong pump powers, a semiconductor optical cavity passes through a Hopf bifurcation and undergoes self-oscillation. We simulate this device using semiclassical Langevin equations and assess the effect of quantum fluctuations on the dynamics. Below threshold, the cavity acts as a phase-insensitive linear amplifier, with noise approximately 5 ×larger than the Caves bound. Above threshold, the limit cycle acts as an analog memory, and the phase diffusion is approximately 10 ×larger than the bound set by the standard quantum limit. We also simulate entrainment of this oscillator and propose an optical Ising machine and classical controlled not (cnot) gate based on the effect.

  4. 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.

  5. Novel Geometries for the LHC Crab Cavity

    SciTech Connect

    B. Hall,G. Burt,C. Lingwood,Robert Rimmer,Haipeng Wang; Hall, B.; Burt, G.; Lingwood, C.; Rimmer, Robert; Wang, Haipeng

    2010-05-01

    The planned luminosity upgrade to LHC is likely to necessitate a large crossing angle and a local crab crossing scheme. For this scheme crab cavities align bunches prior to collision. The scheme requires at least four such cavities, a pair on each beam line either side of the interaction point (IP). Upstream cavities initiate rotation and downstream cavities cancel rotation. Cancellation is usually done at a location where the optics has re-aligned the bunch. The beam line separation near the IP necessitates a more compact design than is possible with elliptical cavities such as those used at KEK. The reduction in size must be achieved without an increase in the operational frequency to maintain compatibility with the long bunch length of the LHC. This paper proposes a suitable superconducting variant of a four rod coaxial deflecting cavity (to be phased as a crab cavity), and presents analytical models and simulations of suitable designs.

  6. Novel Geometries for the LHC Crab Cavity

    SciTech Connect

    B. Hall, G. Burt, C. Lingwood, R. Rimmer, H. Wang

    2010-05-23

    The planned luminosity upgrade to LHC is likely to necessitate a large crossing angle and a local crab crossing scheme. For this scheme crab cavities align bunches prior to collision. The scheme requires at least four such cavities, a pair on each beam line either side of the interaction point (IP). Upstream cavities initiate rotation and downstream cavities cancel rotation. Cancellation is usually done at a location where the optics has re-aligned the bunch. The beam line separation near the IP necessitates a more compact design than is possible with elliptical cavities such as those used at KEK. The reduction in size must be achieved without an increase in the operational frequency to maintain compatibility with the long bunch length of the LHC. This paper proposes a suitable superconducting variant of a four rod coaxial deflecting cavity (to be phased as a crab cavity), and presents analytical models and simulations of suitable designs.

  7. A micropillar for cavity optomechanics

    SciTech Connect

    Kuhn, Aurélien; Neuhaus, Leonhard; Deléglise, Samuel; Briant, Tristan; Cohadon, Pierre-François; Heidmann, Antoine; Van Brackel, Emmanuel; Chartier, Claude; Ducloux, Olivier; Le Traon, Olivier; Michel, Christophe; Pinard, Laurent; Flaminio, Raffaele

    2014-12-04

    Demonstrating the quantum ground state of a macroscopic mechanical object is a major experimental challenge in physics, at the origin of the rapid emergence of cavity optomechanics. We have developed a new generation of optomechanical devices, based on a microgram quartz micropillar with a very high mechanical quality factor. The structure is used as end mirror in a Fabry-Perot cavity with a high optical finesse, leading to ultra-sensitive interferometric measurement of the resonator displacement. We expect to reach the ground state of this optomechanical resonator by combining cryogenic cooling in a dilution fridge at 30 mK and radiation-pressure cooling. We have already carried out a quantum-limited measurement of the micropillar thermal noise at low temperature.

  8. A micropillar for cavity optomechanics

    NASA Astrophysics Data System (ADS)

    Kuhn, Aurélien; Neuhaus, Leonhard; Van Brackel, Emmanuel; Chartier, Claude; Ducloux, Olivier; Le Traon, Olivier; Michel, Christophe; Pinard, Laurent; Flaminio, Raffaele; Deléglise, Samuel; Briant, Tristan; Cohadon, Pierre-François; Heidmann, Antoine

    2014-12-01

    Demonstrating the quantum ground state of a macroscopic mechanical object is a major experimental challenge in physics, at the origin of the rapid emergence of cavity optomechanics. We have developed a new generation of optomechanical devices, based on a microgram quartz micropillar with a very high mechanical quality factor. The structure is used as end mirror in a Fabry-Perot cavity with a high optical finesse, leading to ultra-sensitive interferometric measurement of the resonator displacement. We expect to reach the ground state of this optomechanical resonator by combining cryogenic cooling in a dilution fridge at 30 mK and radiation-pressure cooling. We have already carried out a quantum-limited measurement of the micropillar thermal noise at low temperature.

  9. Active cavity radiometer type IV.

    PubMed

    Willson, R C

    1979-01-15

    A new cavity pyrheliometer, the active cavity radiometer type IV (ACR IV), has been developed for the measurement of total solar optical irradiance. Analysis predicts its ability to measure at the solar constant level with 0.1% uncertainty in SI units. In comparison tests ACR IVs have consistently demonstrated 0.3% higher results than the World Radiometric Reference scale. A prototype has been tested, and a flight instrument has been developed and flown in a sounding rocket experiment to determine the solar constant. ACR IV instrumentation is being developed for flight experiments on the Spacelab I and Solar Maximum missions to monitor the total solar output of optical radiation as part of a long-term program to detect variations of climatological significance. PMID:20208684

  10. Dissipative structures in optomechanical cavities

    E-print Network

    Joaquín Ruiz-Rivas; Carlos Navarrete-Benlloch; Giuseppe Patera; Eugenio Roldán; Germán J. de Valcárcel

    2015-06-21

    Motivated by the increasing interest in the properties of multimode optomechanical devices, here we study a system in which a driven mode of a large-area optical cavity is despersively coupled to a deformable mechanical element. Two different models naturally appear in such scenario, for which we predict the formation of periodic patterns, localized structures (cavity solitons), and domain walls, among other complex nonlinear phenomena. Further, we propose a realistic design based on intracavity membranes where our models can be studied experimentally. Apart from its relevance to the field of nonlinear optics, the results put forward here are a necessary step towards understanding the quantum properties of optomechanical systems in the multimode regime of both the optical and mechanical degrees of freedom.

  11. Mineralogy and provenance of clays in miarolitic cavities of the Pikes Peak Batholith, Colorado

    USGS Publications Warehouse

    Kile, D.E.

    2005-01-01

    Clay samples from 105 cavities within miarolitic granitic pegmatites throughout the Pikes Peak batholith, in Colorado, were analyzed by powder X-ray diffraction (XRD). Smectite (beidellite), illite, and kaolinite were found within the cavities. Calculation of crystallite-thickness distribution (CTD), mean thickness of the crystallites, and variance in crystallite thickness, as deduced from XRD patterns, allowed a determination of provenance and mode of formation for illite and smectite. Authigenic miarolitic-cavity illite and smectite show lognormal CTDs and larger mean thicknesses of crystallites than do their soil-derived counterparts; non-lognormal illite in a cavity results from mixing of cavity and soil illite. Analysis of mean thickness and thickness variance shows that crystal growth of illite is initiated by a nucleation event of short duration, followed by surface-controlled kinetics. Crystallization of the miarolitic cavity clays is presumed to occur by neoformation from hydrothermal fluids. The assessment of provenance allows a determination of regional and local distributions of clay minerals in miarolitic cavities within the Pikes Peak batholith.

  12. Natural cavities used by wood ducks in north-central Minnesota

    USGS Publications Warehouse

    Gilmer, D.S.; Ball, I.J.; Cowardin, L.M.; Mathisen, J.

    1978-01-01

    Radio telemetry was used to locate 31 wood duck (Aix sponsa) nest cavity sites in 16 forest stands. Stands were of 2 types: (1) mature (mean = 107 years) northern hardwoods (10 nest sites), and (2) mature (mean = 68 years) quaking aspen (Populus tremuloides) (21 nest sites). Aspen was the most important cavity-producing tree used by wood ducks and accounted for 57 percent of 28 cavities inspected. In stands used by wood ducks, the average density of suitable cavities was about 4 per hectare. Trees containing nests were closer to water areas (P < 0.05) and the nearest forest canopy openings (P < 0.01) than was a random sample of trees from the same stands. A significant (P < 0.005) relationship existed between the orientation of the cavity entrance and the nearest canopy opening. Potential wood duck cavities usually were clustered within a stand rather than randomly distributed. Selection of trees by woodpeckers for nest hole construction probably influenced the availability of cavities used by wood ducks. A plan for managing forests to benefit wood ducks and other wildlife dependent on old-growth timber is discussed.

  13. 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.

  14. 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.

  15. 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.

  16. Growth hormone and growth?

    PubMed

    Harvey, Steve

    2013-09-01

    Pituitary GH is obligatory for normal growth in mammals, but the importance of pituitary GH in avian growth is less certain. In birds, pituitary GH is biologically active and has growth promoting actions in the tibia-test bioassay. Its importance in normal growth is indicated by the growth suppression following the surgical removal of the pituitary gland or after the immunoneutralization of endogenous pituitary GH. The partial restoration of growth in some studies with GH-treated hypophysectomized birds also suggests GH dependency in avian growth, as does the dwarfism that occurs in some strains with GHR dysfunctions. Circulating GH concentrations are also correlated with body weight gain, being high in young, rapidly growing birds and low in slower growing older birds. Nevertheless, despite these observations, there is an extensive literature that concludes pituitary GH is not important in avian growth. This is based on numerous studies with hypophysectomized and intact birds that show only slight, transitory or absent growth responses to exogenous GH-treatment. Moreover, while circulating GH levels correlate with weight gain in young birds, this may merely reflect changes in the control of pituitary GH secretion during aging, as numerous studies involving experimental alterations in growth rate fail to show positive correlations between plasma GH concentrations and the alterations in growth rate. Furthermore, growth is known to occur in the absence of pituitary GH, as most embryonic development occurs prior to the ontogenetic appearance of pituitary somatotrophs and the appearance of GH in embryonic circulation. Early embryonic growth is also independent of the endocrine actions of pituitary GH, since removal of the presumptive pituitary gland does not impair early growth. Embryonic growth does, however, occur in the presence of extrapituitary GH, which is produced by most tissues and has autocrine or paracrine roles that locally promote growth and development. The role of GH in avian growth is therefore still unclear. PMID:23376467

  17. Optomechanic interactions in phoxonic cavities

    SciTech Connect

    Djafari-Rouhani, Bahram; Oudich, Mourad; Pennec, Yan; El-Jallal, Said

    2014-12-15

    Phoxonic crystals are periodic structures exhibiting simultaneous phononic and photonic band gaps, thus allowing the confinement of both excitations in the same cavity. The phonon-photon interaction can be enhanced due to the overlap of both waves in the cavity. In this paper, we discuss some of our recent theoretical works on the strength of the optomechanic coupling, based on both photoelastic and moving interfaces mechanisms, in different (2D, slabs, strips) phoxonic crystals cavities. The cases of two-dimensional infinite and slab structures will enable us to mention the important role of the symmetry and degeneracy of the modes, as well as the role of the materials whose photoelastic constants can be wavelength dependent. Depending on the phonon-photon pair, the photoelastic and moving interface mechanisms can contribute in phase or out-of-phase. Then, the main part of the paper will be devoted to the optomechanic interaction in a corrugated nanobeam waveguide exhibiting dual phononic/photonic band gaps. Such structures can provide photonic modes with very high quality factor, high frequency phononic modes of a few GHz inside a gap and optomechanical coupling rate reaching a few MHz.

  18. 3D Multimode Cavity QED

    NASA Astrophysics Data System (ADS)

    Naik, Ravi; McKay, David C.; Schuster, David I.

    2015-03-01

    Scalable quantum computing architectures require many long-lived and highly coherent, yet easily addressable quantum states. Photonic qubits in 3D superconducting microwave cavities are a promising approach because they are highly insensitive to decoherence and single photon lifetimes exceeding 10 ms have been demonstrated. However, the plurality of current 3D cavity devices are engineered to address single photon modes. In this talk, we introduce our implementation of a multimode 3D cavity that can store greater than 20 distinct, long-lived photon modes. To perform single- and two-qubit gates between photons, each of the modes are coupled to a single flux-tunable superconducting transmon qubit. We will discuss our preliminary results towards a controlled phase gate between any pair of photons modes. This multimode circuit QED architecture may also be used as a many-body bosonic system for quantum simulation, to study multimode quantum optics, and for quantum memories as part of a larger quantum network.

  19. Superconducting cavities for particle accelerators

    NASA Astrophysics Data System (ADS)

    Padamsee, H.

    1992-02-01

    RF Superconductivity has become an important technology for particle accelerators for high energy physics, nuclear physics, and free electron lasers. More than 100 MVolts of Superconducting RF (SRF) cavities have been installed in accelerators for heavy ions and operated at gradients of 2-3 MV/m in excess of 105 hours. More than 500 MVolts are installed in electron accelerators and operated at gradients of 4-6 MV/m in excess of 104 hours. Encouraged by this success, another 500 meters of SRF cavities are in the production line. New applications for High Energy Physics are forthcoming for high current e+e- colliders in the B-quark energy range (B-factory). For the next linear collider in the TeV energy range, there are many compelling attractions to use SRF, if the gradients can be improved substantially and the costs lowered. Substantial progress has been made in understanding performance limitations and in inventing cures through better cavity geometries, materials, and processes. Techniques are now in hand to reach 15-20 MV/m accelerating. In light of this progress, the potential of high gradient SRF for a TeV Energy Superconducting Linear Accelerator (TESLA) will be explored.

  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. FRACTIONAL PEARSON DIFFUSIONS

    PubMed Central

    Leonenko, Nikolai N.; Meerschaert, Mark M.

    2013-01-01

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change. PMID:23626377

  2. Doublon Growth in Solidification

    E-print Network

    Brian Utter; E. Bodenschatz

    2004-08-13

    We present experiments on the doublon growth morphology in directional solidification. Samples used are succinonitrile with small amounts of poly(ethylene oxide), acetone, or camphor as the solute. Doublons, or symmetry-broken dendrites, are generic diffusion-limited growth structures expected at large undercooling and low anisotropy. Low anisotropy growth is achieved by selecting a grain near the $\\{111\\}$ plane leading to either seaweed (dense branching morphology) or doublon growth depending on experimental parameters. We find selection of doublons to be strongly dependent on solute concentration and sample orientation. Doublons are selected at low concentrations (low solutal undercooling) in contrast to the prediction of doublons at large thermal undercooling in pure materials. Doublons also exhibit preferred growth directions and changing the orientation of a specific doublonic grain changes the character and stability of the doublons. We observe transitions between seaweed and doublon growth with changes in concentration and sample orientation.

  3. Phonon-Assisted Stimulated Emission and Ultra - Active Layers in Cleaved Cavity and Vertical Cavity Surface Emitting Lasers.

    NASA Astrophysics Data System (ADS)

    Benjamin, Seldon David

    Unique lasing processes in III-V semiconductor lasers are examined. The dynamics of stimulated photon emission in thin AlGaAs/GaAs single quantum well lasers are observed experimentally and modeled by rate equations describing the electron and photon densities. Agreement between experiment and theory are achieved when the transition probability matrix, calculated with the spreading out of electron and hole wave functions taken into account, is used. The phonon assisted stimulated photon emission observed in this work is delayed with respect to the unassisted emission. This observation is modeled by using a weaker matrix element for the unassisted process which is expected from theory and thus supports our claim that this emission is phonon assisted. Rate equations developed to simulate doubly stimulated emission of photons and phonons do not describe the experimental data so the possibility of stimulated phonon emission is ruled out for the samples studied in this work. Vertical Cavity Surface Emitting Lasers are also studied since they can be designed to support unique lasing processes. The design and growth of vertical cavity surface emitting lasers are discussed and these concepts are applied to the realization of a vertical cavity surface emitting laser with the thinnest active layer of any laser yet reported. Stimulated emission supported across the sub-monolayer thick InAs single quantum well active region can be understood by considering the spreading of the electron and hole wavefunctions beyond the confines of the quantum well to increase the length of the effective gain region. The dynamics of laser action in vertical cavity surface emitting lasers are also studied and reveal that low threshold lasers may not be suitable for high speed operation due to their relatively long photon lifetimes. Finally a structure is proposed to implement a multi-wavelength vertical cavity surface emitting laser using an active region that encourages phonon assisted stimulated emission.

  4. 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.

  5. Galactic civilizations: Population dynamics and interstellar diffusion

    NASA Technical Reports Server (NTRS)

    Newman, W. I.; Sagan, C.

    1978-01-01

    The interstellar diffusion of galactic civilizations is reexamined by potential theory; both numerical and analytical solutions are derived for the nonlinear partial differential equations which specify a range of relevant models, drawn from blast wave physics, soil science, and, especially, population biology. An essential feature of these models is that, for all civilizations, population growth must be limited by the carrying capacity of the environment. Dispersal is fundamentally a diffusion process; a density-dependent diffusivity describes interstellar emigration. Two models are considered: the first describing zero population growth (ZPG), and the second which also includes local growth and saturation of a planetary population, and for which an asymptotic traveling wave solution is found.

  6. 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).

  7. 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.

  8. Grain Growth in Niobium for Superconducting Radio Frequency Cavities 

    E-print Network

    Vernon, Joshua A.

    2009-06-09

    effect of heat treatment for various times and different temperatures. Two different sample purities were tested to show how chemistry affects these heat treatment results. Initial samples The initial samples were sectioned from billets thermo... the microstructure to elongate along the shear plane of the process. Figure 2 shows how the grains change with route A ECAE processing. 3 Figure 2. Simple shear during ECAE. (a) one cycle processing, (b) route 2A [2] Route A means that the billet...

  9. Diffusion of light in semitransparent media

    E-print Network

    Pattelli, Lorenzo; Wiersma, Diederik; Toninelli, Costanza

    2015-01-01

    Light diffusion is usually associated with thick, opaque media. Indeed, multiple scattering is necessary for the onset of the diffusive regime and such condition is generally not met in almost transparent media. Nonetheless, at long enough times, transport in an infinite thin slab is still determined by a multiple scattering process whose complete characterization is lacking. In this paper we show that, after a short transient, the mean square width of the transmitted intensity still exhibits a simple linear increase with time as predicted by diffusion theory, even at optical thickness as low as one. Interestingly, such linear growth is predicted not to depend neither on the slab thickness nor on its refractive index contrast, yet the accuracy of this simple approximation in the ballistic-to-diffusive regime hasn't been investigated so far. By means of Monte Carlo simulations, we find clear evidence that boundary conditions play an active role in redefining the very asymptotic value of the diffusion coefficie...

  10. Surveying Diffusion in Complex Geometries. An Essay

    E-print Network

    Grebenkov, Denis

    2009-01-01

    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 whic...

  11. In vivo toxicity of arsenic trioxide for human cells in diffusion chambers

    SciTech Connect

    Ambrose, K.R.; Butler, T.A.; Callahan, A.P.; Ferren, L.A.

    1986-12-01

    The diffusion chamber system was used to monitor the toxicity of trivalnet arsenic for human target cells in vivo. Cell-impermeable diffusion chambers containing human embryonic lung cells were implanted into the peritoneal cavity of hamsters that one day later were injected i.v. or i.p. with arsenic trioxide (As/sub 2/O/sub 3/) as aqueous solution (AsO/sub 2//sup -/). /sup 74/AsO/sub 2//sup -/ was employed to quantitate the concentration of arsenic reaching the chambered target cells and to describe the toxicokinetics of arsenic in the hamster. Trivalent arsenic induced a growth inhibition in the target cells with the dosage level determining the extent of inhibition at 24 h and the recovery of cell proliferation at 48 h. The maximum concentration of arsenic in the chamber fluid was detected 2 h post i.p. injection, after which the elimination of /sup 74/As from the chamber fluid paralleled the decline of /sup 74/As activity in the plasma of the host animal. Limited tissue distribution studies showed that arsenic was retained primarily in the pelt. 22 refs., 2 figs., 3 tabs.

  12. Cantilever piezoelectric energy harvester with multiple cavities

    NASA Astrophysics Data System (ADS)

    Srinivasulu Raju, S.; Umapathy, M.; Uma, G.

    2015-11-01

    Energy harvesting employing piezoelectric materials in mechanical structures such as cantilever beams, plates, diaphragms, etc, has been an emerging area of research in recent years. The research in this area is also focused on structural tailoring to improve the harvested power from the energy harvesters. Towards this aim, this paper presents a method for improving the harvested power from a cantilever piezoelectric energy harvester by introducing multiple rectangular cavities. A generalized model for a piezoelectric energy harvester with multiple rectangular cavities at a single section and two sections is developed. A method is suggested to optimize the thickness of the cavities and the number of cavities required to generate a higher output voltage for a given cantilever beam structure. The performance of the optimized energy harvesters is evaluated analytically and through experimentation. The simulation and experimental results show that the performance of the energy harvester can be increased with multiple cavities compared to the harvester with a single cavity.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Diffusion and defect characterization studies of mercury cadmium telluride

    NASA Astrophysics Data System (ADS)

    Stevenson, D. A.

    1986-01-01

    During the last six month period, progress has continued on the two major areas of this program: diffusion studies in Mercury Cadmium Telluride (MCT); and growth studies in MCT. The diffusion studies have emphasized the question of multiple and distinct Hg profiles in self-diffusion and the Kirkendall effect for interdiffusion. The growth studies have concerned the relation between the surface morphology of epitaxial layers and the substrate orientation, the development of new Hg rich liquid phase epitaxial growth method, and a continuation of an electrochemical of thermodynamic properties of MCT and related binary compounds.

  19. 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.

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

    DOEpatents

    Tadir, Y.; Berns, M.W.; Svaasand, L.O.; Tromberg, B.J.

    1995-12-26

    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. 5 figs.

  1. Cavities

    MedlinePLUS

    ... passed to the child. A Brighter Smile Through Cosmetic Dentistry Cosmetic dentistry can dramatically improve a person’s appearance. The ... You Know... Table 4 A Brighter Smile Through Cosmetic Dentistry Table 5 Root Canal Treatment for a ...

  2. 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.

  3. Grating cavity dual wavelength dye laser.

    PubMed

    Zapata-Nava, Oscar Javier; Rodríguez-Montero, Ponciano; Iturbe-Castillo, M David; Treviño-Palacios, Carlos Gerardo

    2011-02-14

    We report simultaneous dual wavelength dye laser emission using Littman-Metcalf and Littrow cavity configurations with minimum cavity elements. Dual wavelength operation is obtained by laser operation in two optical paths inside the cavity, one of which uses reflection in the circulating dye cell. Styryl 14 laser dye operating in the 910 nm to 960 nm was used in a 15%:85% PC/EG solvent green pumped with a Q-switched doubled Nd3+:YAG laser. PMID:21369171

  4. Universal quantum cloning in cavity QED

    SciTech Connect

    Milman, P.; Ollivier, H.; Raimond, J.M.

    2003-01-01

    We propose an implementation of an universal quantum cloning machine [UQCM, V. Buzek and M. Hillery, Phys. Rev. A 54, 1844 (1996)] in a cavity quantum electrodynamics experiment. This UQCM acts on the electronic states of atoms that interact with the electromagnetic field of a high-Q cavity. We discuss here the specific case of the 1{yields}2 cloning process using either a one- or a two-cavity configuration.

  5. Highly uniform and reproducible vertical-cavity surface emitting lasers grown by metalorganic chemical vapor deposition

    SciTech Connect

    Hou, H.Q.; Chui, H.C.; Choquette, K.D.; Hammons, B.E.; Breiland, W.G.; Geib, K.M.

    1996-01-01

    We show that the uniformity of the lasing wavelength of vertical-cavity surface emitting lasers (VCSELs) can be as good as {plus_minus}0.3% across a entire 3 in. wafer in MOCVD growth with a similar run-to-run reproducibility.

  6. Basketballs as spherical acoustic cavities

    NASA Astrophysics Data System (ADS)

    Russell, Daniel A.

    2010-06-01

    The sound field resulting from striking a basketball is found to be rich in frequency content, with over 50 partials in the frequency range of 0-12 kHz. The frequencies are found to closely match theoretical expectations for standing wave patterns inside a spherical cavity. Because of the degenerate nature of the mode shapes, explicit identification of the modes is not possible without internal investigation with a microphone probe. A basketball proves to be an interesting application of a boundary value problem involving spherical coordinates.

  7. Cavity quantum electro-optics

    SciTech Connect

    Tsang, Mankei

    2010-06-15

    The quantum dynamics of the coupling between a cavity optical field and a resonator microwave field via the electro-optic effect is studied. This coupling has the same form as the optomechanical coupling via radiation pressure, so all previously considered optomechanical effects can in principle be observed in electro-optic systems as well. In particular, I point out the possibilities of laser cooling of the microwave mode, entanglement between the optical mode and the microwave mode via electro-optic parametric amplification, and back-action-evading optical measurements of a microwave quadrature.

  8. Cavity quantum electro-optics

    E-print Network

    Mankei Tsang

    2010-06-30

    The quantum dynamics of the coupling between a cavity optical field and a resonator microwave field via the electro-optic effect is studied. This coupling has the same form as the opto-mechanical coupling via radiation pressure, so all previously considered opto-mechanical effects can in principle be observed in electro-optic systems as well. In particular, I point out the possibilities of laser cooling of the microwave mode, entanglement between the optical mode and the microwave mode via electro-optic parametric amplification, and back-action-evading optical measurements of a microwave quadrature.

  9. [Aging and the oral cavity].

    PubMed

    Pinzón Tofiño, M E; Gaitán Cepeda, L A

    1989-03-01

    Like all tissues in the human body, those within the buccal cavity undergo changes with ageing, which are observable in clinical practice. Such changes include the appearance of lingual varicosities, glossitis, atrophy of the taste papillae and of the salivary glands, with variable degrees of xerostomia, periodontal disease and predisposal to develop malignancies. Dental units may also be affected, with occurrence, among other processes, of abrasion, attrition, caries and lowered dentarian sensibility, phenomena of interest for the odontologist in handling geriatric patients. PMID:2699526

  10. Pressurized melt ejection into scaled reactor cavities

    SciTech Connect

    Tarbell, W.W.; Pilch, M.; Brockmann, J.E.; Ross, J.W.; Gilbert, D.W.

    1986-10-01

    This report describes four tests performed in the High-Pressure Melt Streaming Program (HIPS) using linear-scaled cavities of the Zion Nuclear Power Plant. These experiments were conducted to study the phenomena involved in high-pressure ejection of core debris into the cavity beneath the reactor pressure vessel. One-tenth and one-twentieth linear scale models of reactor cavities were constructed and instrumented. The first test used an apparatus constructed of alumina firebrick to minimize the potential interaction between the ejected melt and cavity material. The remaining three experiments used scaled representations of the Zion nuclear plant geometry, constructed of prototypic concrete composition.

  11. 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.

  12. Secure Quantum Dialogue via Cavity QED

    NASA Astrophysics Data System (ADS)

    Ye, Tian-Yu

    2015-03-01

    In this paper, a secure quantum dialogue protocol via cavity QED is suggested by using the evolution law of atom in cavity QED. The present protocol employs both the two-step transmission and the unitary operation encoding. Two security checks are adopted to ensure its transmission security against the active attacks from an outside eavesdropper. The present protocol avoids the information leakage problem by using the entanglement swapping between any two Bell states via cavity QED together with the shared secret Bell state. Compared with the previous information leakage resistant quantum dialogue protocol via cavity QED, the present protocol takes advantage in quantum measurement.

  13. Cavity-locked ring down spectroscopy

    DOEpatents

    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.

  14. 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, A.; 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.

  15. 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.

  16. 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).

  17. 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

  18. Unpacking of a Crumpled Wire from Two-Dimensional Cavities.

    PubMed

    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

  19. 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.

  20. High-temperature morphological evolution of lithographically introduced cavities in silicon carbide

    SciTech Connect

    Narushima, Takayuki; Glaeser, Andreas M.

    2000-12-01

    Internal cavities of controlled geometry and crystallography were introduced in 6H silicon carbide single crystals by combining lithographic methods, ion beam etching, and solid-state diffusion bonding. The morphological evolution of these internal cavities (negative crystals) in response to anneals of up to 128 h duration at 1900 degrees C was examined using optical microscopy. Surface energy anisotropy and faceting have a strong influence on both the geometric and kinetic characteristics of evolution. Decomposition of 12{bar 1}0 cavity edges into 101{bar 0} facets was observed after 16 h anneals, indicating that 12{bar 1}0 faces are not components of the Wulff shape. The shape evolution kinetics of penny-shaped cavities were also investigated. Experimentally observed evolution rates decreased much more rapidly with those predicted by a model in which surface diffusion is assumed to be rate-limiting. This suggests that the development of facets, and the associated loss of ledges and terraces during the initial stages of evolution results in an evolution process limited by the nucleation rate of attachment/detachment sites (ledges) on the facets.

  1. Breakthrough: Record-Setting Cavity

    ScienceCinema

    Ciovati, Gianluigi

    2014-05-21

    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.

  2. Spinning Motions in Coronal Cavities

    NASA Astrophysics Data System (ADS)

    Wang, Y.-M.; Stenborg, G.

    2010-08-01

    In movies made from Fe XII 19.5 nm images, coronal cavities that graze or are detached from the solar limb appear as continually spinning structures, with sky-plane projected flow speeds in the range 5-10 km s-1. These whirling motions often persist in the same sense for up to several days and provide strong evidence that the cavities and the immediately surrounding streamer material have the form of helical flux ropes viewed along their axes. A pronounced bias toward spin in the equatorward direction is observed during 2008. We attribute this bias to the poleward concentration of the photospheric magnetic flux near sunspot minimum, which leads to asymmetric heating along large-scale coronal loops and tends to drive a flow from higher to lower latitudes; this flow is converted into an equatorward spinning motion when the loops pinch off to form a flux rope. As sunspot activity increases and the polar fields weaken, we expect the preferred direction of the spin to reverse.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Radiation characteristics of a high-emissivity cylindrical-spherical cavity with obscuration.

    PubMed

    Meier, Steven R; Joseph, Richard I; Antiochos, Spiro K

    2004-01-01

    We have calculated, to first order, the apparent emissivity of the bounding diffuse surfaces of a high-emissivity cylindrical-spherical cavity enclosure. Our calculations indicate that to achieve emissivities close to a perfectly absorbing blackbody cavity along the bounding surfaces of the spherical enclosure, the radius of the sphere must be equal to or greater than a factor of 4 times the cylinder radius R(S) > or = 4R(C). Furthermore, to achieve emissivities approaching a blackbody cavity along the lower bounding surfaces of the cylindrical enclosure, the length of the cylinder must be a factor of 4 times greater than the radius of the cylinder L > or = 4R(C). In addition, we present the mathematical framework necessary to calculate radiant transfer within a cavity enclosure that contains obscuration. These results can be applied to the design of high-emissivity blackbody calibration cavities and to the reduction of stray light in terrestrial and spaceborne optical systems. PMID:14725402

  10. Evolution of pH during in-situ leaching in small concrete cavities

    SciTech Connect

    Saguees, A.A.; Moreno, E.I.; Andrade, C.

    1997-11-01

    Small amounts (0.4 cc) of neutral water placed in small cylindrical cavities (5 mm diameter) in concrete exposed to 100% relative humidity first developed a pH comparable to that of a saturated Ca(OH){sub 2} solution. The pH then increased over a period of days-weeks toward a higher terminal value. A micro pH electrode arrangement was used. This behavior was observed in samples of 12 different concrete mix designs, including some with pozzolanic additions. The average terminal cavity pH closely approached that of expressed pore water from the same concretes. A simplified mathematical model reproduced the experimentally observed behavior. The model assumed inward diffusional transport of the pH-determining species in the surrounding concrete pore solution. The experimental results were consistent with the model predictions when using diffusion parameters on the order of those previously reported for alkali cations in concrete. The cavity size, cavity water content, and exposure to atmospheric CO{sub 2} should be minimized when attempting to obtain cavity pH values approaching those of the surrounding pore water.

  11. 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

  12. (VDA) Vapor Diffusion Apparatus Tray

    NASA Technical Reports Server (NTRS)

    1994-01-01

    These Vapor Diffusion Apparatus (VDA) trays were first flown in the Thermal Enclosure System (TES) during the USMP-2 (STS-62) mission. Each tray can hold 20 protein crystal growth chambers. Each chamber contains a double-barrel syringe; one barrel holds protein crystal solution and the other holds precipitant agent solution. During the microgravity mission, a torque device is used to simultaneously retract the plugs in all 20 syringes. The two solutions in each chamber are then mixed. After mixing, droplets of the combined solutions are moved onto the syringe tips so vapor diffusion can begin. During the length of the mission, protein crystals are grown in the droplets. Shortly before the Shuttle's return to Earth, the experiment is deactivated by retracting the droplets containing protein crystals, back into the syringes.

  13. Design of Plasmon Cavities for Solid-State Cavity QED Applications

    E-print Network

    Yiyang Gong; Jelena Vuckovic

    2006-11-25

    Research on photonic cavities with low mode volume and high quality factor garners much attention because of applications ranging from optoelectronics to cavity quantum electrodynamics (QED). We propose a cavity based on surface plasmon modes confined by metallic distributed Bragg reflectors. We analyze the structure with Finite Difference Time Domain simulations and obtain modes with quality factor 1000 (including losses from metals), reduced mode volume relative to photonic crystal cavities, Purcell enhancements of hundreds, and even the capability of enabling cavity QED strong coupling.

  14. 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

  15. 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.

  16. Fast tuning of superconducting microwave cavities

    SciTech Connect

    Sandberg, M.; Wilson, C. M.; Persson, F.; Johansson, G.; Shumeiko, V.; Bauch, T.; Duty, T.; Delsing, P.

    2008-11-07

    Photons are fundamental excitations of electromagnetic fields and can be captured in cavities. For a given cavity with a certain size, the fundamental mode has a fixed frequency f which gives the photons a specific 'color'. The cavity also has a typical lifetime {tau}, which results in a finite linewidth {delta}f. If the size of the cavity is changed fast compared to {tau}, and so that the frequency change {delta}f>>{delta}f, then it is possible to change the 'color' of the captured photons. Here we demonstrate superconducting microwave cavities, with tunable effective lengths. The tuning is obtained by varying a Josephson inductance at one end of the cavity. We show data on four different samples and demonstrate tuning by several hundred linewidths in a time {delta}t<<{tau}. Working in the few photon limit, we show that photons stored in the cavity at one frequency will leak out from the cavity with the new frequency after the detuning. The characteristics of the measured devices make them suitable for different applications such as dynamic coupling of qubits and parametric amplification.

  17. Folded cavity design for a ruby resonator

    NASA Technical Reports Server (NTRS)

    Arunkumar, K. A.; Trolinger, James D.

    1988-01-01

    A folded cavity laser resonator operating in the TEM(00) mode has been built and tested. The new oscillator configuration leads to an increase in efficiency and to better line narrowing due to the increased number of passes through the laser rod and tuning elements, respectively. The modification is shown to lead to cavity ruggedization.

  18. Developing of superconducting niobium cavities for accelerators

    NASA Astrophysics Data System (ADS)

    Pobol, I. L.; Yurevich, S. V.

    2015-11-01

    The results of a study of structure and mechanical properties of welding joints, superconducting characteristics of the material after joining of welded components of superconducting radio frequency cavities are presented. The paper also describes the results of testing of the RF 1.3 GHz single-cell niobium cavity manufactured in the PTI NAS Belarus.

  19. 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...

  20. 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.

  1. Cavity cooling below the recoil limit.

    PubMed

    Wolke, Matthias; Klinner, Julian; Keßler, Hans; Hemmerich, Andreas

    2012-07-01

    Conventional laser cooling relies on repeated electronic excitations by near-resonant light, which constrains its area of application to a selected number of atomic species prepared at moderate particle densities. Optical cavities with sufficiently large Purcell factors allow for laser cooling schemes, avoiding these limitations. Here, we report on an atom-cavity system, combining a Purcell factor above 40 with a cavity bandwidth below the recoil frequency associated with the kinetic energy transfer in a single photon scattering event. This lets us access a yet-unexplored regime of atom-cavity interactions, in which the atomic motion can be manipulated by targeted dissipation with sub-recoil resolution. We demonstrate cavity-induced heating of a Bose-Einstein condensate and subsequent cooling at particle densities and temperatures incompatible with conventional laser cooling. PMID:22767925

  2. Fast thermometry for superconducting rf cavity testing

    SciTech Connect

    Orris, Darryl; Bellantoni, Leo; Carcagno, Ruben H.; Edwards, Helen; Harms, Elvin Robert; Khabiboulline, Timergali N.; Kotelnikov, Sergey; Makulski, Andrzej; Nehring, Roger; Pischalnikov, Yuriy; /Fermilab

    2007-06-01

    Fast readout of strategically placed low heat capacity thermometry can provide valuable information of Superconducting RF (SRF) cavity performance. Such a system has proven very effective for the development and testing of new cavity designs. Recently, several resistance temperature detectors (RTDs) were installed in key regions of interest on a new 9 cell 3.9 GHz SRF cavity with integrated HOM design at FNAL. A data acquisition system was developed to read out these sensors with enough time and temperature resolution to measure temperature changes on the cavity due to heat generated from multipacting or quenching within power pulses. The design and performance of the fast thermometry system will be discussed along with results from tests of the 9 cell 3.9GHz SRF cavity.

  3. 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.

    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.

  4. Niobium Cavity Electropolishing Modelling and Optimisation

    E-print Network

    Ferreira, L M A; Forel, S; Shirra, J A

    2013-01-01

    It’s widely accepted that electropolishing (EP) is the most suitable surface finishing process to achieve high performance bulk Nb accelerating cavities. At CERN and in preparation for the processing of the 704 MHz high-beta Superconducting Proton Linac (SPL) cavities a new vertical electropolishing facility has been assembled and a study is on-going for the modelling of electropolishing on cavities with COMSOL® software. In a first phase, the electrochemical parameters were taken into account for a fixed process temperature and flow rate, and are presented in this poster as well as the results obtained on a real SPL single cell cavity. The procedure to acquire the data used as input for the simulation is presented. The modelling procedure adopted to optimise the cathode geometry, aimed at a uniform current density distribution in the cavity cell for the minimum working potential and total current is explained. Some preliminary results on fluid dynamics is also briefly described.

  5. Performance of 3-cell Seamless Niobium cavities

    SciTech Connect

    Kneisel, Peter K.; Ciovati, Gianluigi; Jelezov, I.; Singer, W.; Singer, X.

    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.

  6. 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

  7. Air flow in a collapsing cavity

    NASA Astrophysics Data System (ADS)

    Peters, Ivo R.; Gekle, Stephan; Lohse, Detlef; van der Meer, Devaraj

    2013-03-01

    We experimentally study the airflow in a collapsing cavity created by the impact of a circular disc on a water surface. We measure the air velocity in the collapsing neck in two ways: Directly, by means of employing particle image velocimetry of smoke injected into the cavity and indirectly, by determining the time rate of change of the volume of the cavity at pinch-off and deducing the air flow in the neck under the assumption that the air is incompressible. We compare our experiments to boundary integral simulations and show that close to the moment of pinch-off, compressibility of the air starts to play a crucial role in the behavior of the cavity. Finally, we measure how the air flow rate at pinch-off depends on the Froude number and explain the observed dependence using a theoretical model of the cavity collapse.

  8. Preconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda

    E-print Network

    Zhang, Jun

    the growth of the Krylov iterations. Key words ­ laminar diffusion flame, vorticity­velocity formulationPreconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda Samir Karaa of an elliptic flame sheet problem. By selecting the generalized minimum residual method as the linear smoother

  9. Income, Inequality, Market Potential, and Diffusion of Mobile Telephony

    ERIC Educational Resources Information Center

    Kim, Sungjoong

    2009-01-01

    The diffusion of many previous innovations eventually slowed down and reached an equilibrium level. Despite continued rapid growth, it is possible that the diffusion of mobile telephony will also begin to decelerate and reach a saturation level. Whether universal service can be achieved with the help of mobile telephony will therefore depend…

  10. The diffusive evaporation-deposition model and the voter model

    E-print Network

    Johansen, Adam

    The diffusive evaporation-deposition model and the voter model Benjamin Graham University Introduction The evaporation-deposition model [1], also known as the Takaysu model with desorption [4], is a model for monomers undergoing diffusion, coagulation, growth and evaporation. It is defined

  11. Growth Disorders

    MedlinePLUS

    ... their parents are. But some children have growth disorders. Growth disorders are problems that prevent children from developing normal ... growth can sometimes signal a gland problem or disease. The pituitary gland makes growth hormone, which stimulates ...

  12. Growth Hormone

    MedlinePLUS

    ... limited. Home Visit Global Sites Search Help? Growth Hormone Share this page: Was this page helpful? Also known as: GH; Human Growth Hormone; HGH; Somatotropin; Growth Hormone Stimulation Test; Growth Hormone ...

  13. Soot Formation in Hydrocarbon/Air Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, P. B.; Faeth, G. M.

    1994-01-01

    Soot processes within hydrocarbon/air diffusion flames are important because they affect the durability and performance of propulsion systems, the hazards of unwanted fires, the pollutant and particulate emissions from combustion processes, and the potential for developing computational combustion. Motivated by these observations, this investigation involved an experimental study of the structure and soot properties of round laminar jet diffusion flames, seeking an improved understanding of soot formation (growth and nucleation) within diffusion flames. The present study extends earlier work in this laboratory concerning laminar smoke points (l) and soot formation in acetylene/air laminar jet diffusion flames (2), emphasizing soot formation in hydrocarbon/air laminar jet diffusion flames for fuels other than acetylene. In the flame system, acetylene is the dominant gas species in the soot formation region and both nucleation and growth were successfully attributed to first-order reactions of acetylene, with nucleation exhibiting an activation energy of 32 kcal/gmol while growth involved negligible activation energy and a collision efficiency of O.53%. In addition, soot growth in the acetylene diffusion flames was comparable to new soot in premixed flame (which also has been attributed to first-order acetylene reactions). In view of this status, a major issue is the nature of soot formation processes in diffusion flame involving hydrocarbon fuels other than acetylene. In particular, information is needed about th dominant gas species in the soot formation region and the impact of gas species other than acetylene on soot nucleation and growth.

  14. Design and characterization of optically pumped vertical cavity surface emitting lasers. Master's thesis

    SciTech Connect

    Bagnell, R.J.

    1992-12-01

    Vertical Cavity Surface Emitting Lasers (VCSELs) are a form of semiconductor laser which have their cavity oriented orthogonally to the plane of the wafer. The orientation necessitates short cavities, highly reflective mirrors and a relatively high gain/loss ratio. Even so, the resultant superior exit beam characteristics and the tight packing density of the finished lasers provide strong motivation for pursuing the growth of these structures. This thesis details the design of an optically pumped InGaAs multiple quantum well periodic gain structure VCSEL with a 950 nm lasing wavelength. These growths were to be a first attempt at VCSEL construction, so part of this study included verification of the quality of the parts of the finished design. These measurements required the construction of a laboratory configuration to optically pump VCSELs and characterize them by spectral reflectivity, output beam polarization, mode, lasing wavelength, and optimal pump wavelength. Analysis of the characteristics for several VCSELs obtained from the University of Arizona, and the back mirror grown locally, illustrate tile ability to use measured data and theoretical spectral reflectivity calculations to determine the quality of the growths.... Semiconductor lasers, Gallium arsenide lasers, Semiconductor devices, Surface emitting lasers, Distributed Bragg reflector stack, Vertical cavity structure, InGaAs quantum wells.

  15. 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.

  16. Uncoupled achromatic condition of a dog-leg system with the presence of RF cavities

    E-print Network

    Geng, Huiping

    2013-01-01

    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 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 method of transfer matrixes. It is found that to fulfil 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 di...

  17. 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...

  18. Memetic algorithms for ligand expulsion from protein cavities.

    PubMed

    Rydzewski, J; Nowak, W

    2015-09-28

    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 (MD) 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 G-protein-coupled 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 network of channels is studied. PMID:26428990

  19. Memetic algorithms for ligand expulsion from protein cavities

    NASA Astrophysics Data System (ADS)

    Rydzewski, J.; Nowak, W.

    2015-09-01

    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 (MD) 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 G-protein-coupled 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 network of channels is studied.

  20. Fractal fronts of diffusion in microgravity.

    PubMed

    Vailati, Alberto; Cerbino, Roberto; Mazzoni, Stefano; Takacs, Christopher J; Cannell, David S; Giglio, Marzio

    2011-01-01

    Spatial scale invariance represents a remarkable feature of natural phenomena. A ubiquitous example is represented by miscible liquid phases undergoing diffusion. Theory and simulations predict that in the absence of gravity diffusion is characterized by long-ranged algebraic correlations. Experimental evidence of scale invariance generated by diffusion has been limited, because on Earth the development of long-range correlations is suppressed by gravity. Here we report experimental results obtained in microgravity during the flight of the FOTON M3 satellite. We find that during a diffusion process a dilute polymer solution exhibits scale-invariant concentration fluctuations with sizes ranging up to millimetres, and relaxation times as large as 1,000 s. The scale invariance is limited only by the finite size of the sample, in agreement with recent theoretical predictions. The presence of such fluctuations could possibly impact the growth of materials in microgravity. PMID:21505446

  1. 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.

  2. Reduce Confusion about Diffusion.

    ERIC Educational Resources Information Center

    Hebrank, Mary R.

    1997-01-01

    Presents activities that allow students to explore the fundamental but poorly understood concept of diffusion by appealing to their kinesthetic senses first, then challenging their analytical skills as they try to deduce the mathematical principle involved. Presents a computer simulation of diffusion and discusses diffusion's limitations and…

  3. Diffusion Strategy Guide.

    ERIC Educational Resources Information Center

    McCutcheon, James R.; Sanders, John R.

    A methodology is presented for planning and managing the spread of educational innovations. The first portion of the guide develops a theoretical framework for diffusion which summarizes and capitalizes on the latest marketing and on the latest marketing and diffusion research findings. Major stages in the diffusion paradigm discussed include…

  4. 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.

  5. Friction drag reduction by air cavities

    NASA Astrophysics Data System (ADS)

    Zverkhovskyi, Oleksandr; Delfos, René; van Terwisga, Tom; Westerweel, Jerry

    2012-11-01

    Air lubrication is investigated, as it is potentially one of the most efficient frictional drag reduction technologies for ships. Unlike bubbles in the boundary layer, which are explained to be effective while reducing the density of the liquid, artificial air cavities underneath a ship may reduce the amount of wetted surface, which presumable reduces more drag than the extra drag created by the devices required to create the cavities. The efficiency of such cavities has been studied experimentally on laboratory scale in a medium-speed water tunnel containing an optically accessible test section, equipped with a PIV system and cameras to obtain boundary layer- and cavity characteristics, and a force balance to measure the drag. The results of this study confirm that the drag reduction is proportional to the amount of non-wetted area. Based on experimental observations, a design criterion is presented for obtaining stable cavities with a low rate of air consumption. Furthermore, the experiments give insight into the formation and stability of air cavities, including the interaction between a series of cavities along the streamwise direction.

  6. [The solitary pulmonary tuberculous cavity and malignant cavity: comparison on multi-detector row CT].

    PubMed

    Ma, Ensen; Yang, Zhigang; Li, Yuan; Guo, Yingkun; Yu, Jianqun; Deng, Yuping

    2008-08-01

    The objective of this comparative study is to determine the MDCT features of solitary pulmonary tuberculous cavity and malignant cavity and to analyze the advantages there-of in differential diagnosis. The clinical data and MDCT findings of 51 cases of pulmonary tuberculous cavities and 39 cases of malignant cavities were reviewed retrospectively, which include the general aspects of patients, the manifestation of cavity and the changes of adjacent structures. The results revealed that the tuberculous cavity tends to locate in the upper lobe or the superior segment of lower lobe, and it is usually acompanied with cavity wall calcification, satellite lesions, peripheral inflammation, lymph node calcification, small diameter and thin wall thickness. The malignant cavities, showing no disposition to locate in a lobe or segment, are characterized by mural nodules, off-center cavity, lobulation, coarse speculation, lymph node enlargement, vascular clustering sign, big diameter and thick wall. In conclusion, with multiplanar reconstruction on multi-detector row CT, we could elaborate the cavities and the accompained lesions, thus contributing to a correct diagnosis in most cases. PMID:18788305

  7. Cavity solitons in vertical-cavity surface-emitting lasers.

    PubMed

    Vladimirov, A G; Pimenov, A; Gurevich, S V; Panajotov, K; Averlant, E; Tlidi, M

    2014-10-28

    We investigate a control of the motion of localized structures (LSs) of light by means of delay feedback in the transverse section of a broad area nonlinear optical system. The delayed feedback is found to induce a spontaneous motion of a solitary LS that is stationary and stable in the absence of feedback. We focus our analysis on an experimentally relevant system, namely the vertical-cavity surface-emitting laser (VCSEL). We first present an experimental demonstration of the appearance of LSs in a 80??m aperture VCSEL. Then, we theoretically investigate the self-mobility properties of the LSs in the presence of a time-delayed optical feedback and analyse the effect of the feedback phase and the carrier lifetime on the delay-induced spontaneous drift instability of these structures. We show that these two parameters affect strongly the space-time dynamics of two-dimensional LSs. We derive an analytical formula for the threshold associated with drift instability of LSs and a normal form equation describing the slow time evolution of the speed of the moving structure. PMID:25246674

  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. Cavity-controlled chemistry in molecular ensembles

    E-print Network

    Herrera, Felipe

    2015-01-01

    The demonstration of strong and ultrastrong coupling regimes of cavity QED with polyatomic molecules has opened new routes to control chemical dynamics at the nanoscale. We show that strong resonant coupling of a cavity field with an electronic transition can effectively decouple collective electronic and nuclear degrees of freedom in a disordered molecular ensemble, even for molecules with high-frequency quantum vibrational modes having strong electron-vibration interactions. This type of polaron decoupling can be used to control chemical reactions. We show that the rate of electron transfer reactions in a cavity can be orders of magnitude larger than in free space, for a wide class of organic molecular species.

  10. Analytical investigation of cavity blackbody lasers

    NASA Technical Reports Server (NTRS)

    Harries, W. L.

    1985-01-01

    The characteristics of an ideal blackbody cavity lasant were outlined. The choice of an ideal lasant is a complex process depending on a large number of factors, including the choice of a cooling medium and a buffer gas. Planck's radiation law limits the power input per unit area into a CO2 blackbody cavity laser making the surface area for high powered lasers excessively large. It is suggested that an alternative application might be small 1 W lasers for communication and surveillance, because it would be easy to maintain the cavity temperatures in synchronous orbits where 72 minutes each day are spent in the Earth's shadow.

  11. Multicolor quadripartite entanglement from an optomechanical cavity

    SciTech Connect

    Tan Huatang; Li Gaoxiang

    2011-08-15

    We investigate the generation of multicolor quadripartite entangled beams of light with continuous variables via optomechanical coupling in an optical cavity. It is found that the genuine quadripartite entanglement can be achieved among the Stokes and anti-Stokes sidebands of two driven cavity fields. This entanglement still exists for the environment temperature up to about 50 K. We also show that the obtained genuine quadripartite entanglement actually results from concurrent four-wave-mixing processes in the system, which can, in principle, be generalized to obtain a genuine 2N-partite entangled state of light from a generic N-mode cavity optomechanical system.

  12. Numerical modeling of vertical cavity semiconductor lasers

    SciTech Connect

    Chow, W.W.; Hadley, G.R.

    1996-08-01

    A vertical cavity surface emitting laser (VCSEL) is a diode laser whose optical cavity is formed by growing or depositing DBR mirror stacks that sandwich an active gain region. The resulting short cavity supports lasing into a single longitudinal mode normal to the wafer, making these devices ideal for a multitude of applications, ranging from high-speed communication to high-power sources (from 2D arrays). This report describes the development of a numerical VCSEL model, whose goal is to both further their understanding of these complex devices and provide a tool for accurate design and data analysis.

  13. Clamshell microwave cavities having a superconductive coating

    DOEpatents

    Cooke, D. Wayne (Los Alamos, NM); Arendt, Paul N. (Los Alamos, NM); Piel, Helmut (Wuppertal, DE)

    1994-01-01

    A microwave cavity including a pair of opposing clamshell halves, such halves comprised of a metal selected from the group consisting of silver, copper, or a silver-based alloy, wherein the cavity is further characterized as exhibiting a dominant TE.sub.011 mode is provided together with an embodiment wherein the interior concave surfaces of the clamshell halves are coated with a superconductive material. In the case of copper clamshell halves, the microwave cavity has a Q-value of about 1.2.times.10.sup.5 as measured at a temperature of 10K and a frequency of 10 GHz.

  14. Dispersion of coupled mode-gap cavities.

    PubMed

    Lian, Jin; Sokolov, Sergei; Yüce, Emre; Combrié, Sylvain; De Rossi, Alfredo; Mosk, Allard P

    2015-10-01

    The dispersion of a coupled resonator optical waveguide made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the inherent dispersive cavity mode profile; i.e., the mode wave function depends on the driving frequency, not the eigenfrequency. This occurs because the photonic crystal cavity resonances do not form a complete set. We formulate a dispersive mode coupling model that accurately describes the asymmetric dispersion without introducing any new free parameters. PMID:26421563

  15. Dispersion of coupled mode-gap cavities

    NASA Astrophysics Data System (ADS)

    Lian, Jin; Sokolov, Sergei; Yüce, Emre; Combrié, Sylvain; De Rossi, Alfredo; Mosk, Allard P.

    2015-10-01

    The dispersion of a CROW made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the fact that the cavity mode profile itself is dispersive, i.e., the mode wave function depends on the driving frequency, not the eigenfrequency. This occurs because the photonic crystal cavity resonances do not form a complete set. By taking into account the dispersive mode profile, we formulate a mode coupling model that accurately describes the asymmetric dispersion without introducing any new free parameters.

  16. Population trapping due to cavity losses

    E-print Network

    M. Scala; B. Militello; A. Messina; S. Maniscalco; J. Piilo; K. -A. Suominen

    2008-04-21

    In population trapping the occupation of a decaying quantum level keeps a constant non-zero value. We show that an atom-cavity system interacting with an environment characterized by a non-flat spectrum, in the non-Markovian limit, exhibits such a behavior, effectively realizing the preservation of nonclassical states against dissipation. Our results allow to understand the role of cavity losses in hybrid solid state systems and pave the way to the proper description of leakage in the recently developed cavity quantum electrodynamic systems.

  17. 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:

  18. A rare case of pulmonary cysticercosis manifesting as lung cavity with pleural effusion.

    PubMed

    Gupta, Neeraj; Meena, Manoj; Harish, Sabarigirivasan; Patil, Chetan B; Kewlani, Jai Prakash

    2015-01-01

    Isolated pulmonary cysticercosis is extremely rare manifestation of a rather common disease which is distributed worldwide. Most common sites which provide perfect nourishment for the growth of cysticercosis are muscle and brain followed by eye. Pulmonary involvement in cysticercosis is very rare and if at all present, then ill-defined nodular shadows distributed throughout the lung is the usual radiological presentation. No case of cysticercosis presenting as lung cavity with pleural effusion has been reported so far in literature. We came across a rarest presentation of cysticercosis as cavity in the lung with effusion. After nullifying all the differential diagnosis of cavitary lung lesions, a diagnosis of pulmonary cysticercosis was made by histopathological examination of the lung cavity aspirate and enzyme linked immunosorbent assay (ELISA) for cysticercosis. Case was successfully treated with albendazole (15mg/kg) with steroid cover. PMID:26628774

  19. A rare case of pulmonary cysticercosis manifesting as lung cavity with pleural effusion

    PubMed Central

    Gupta, Neeraj; Meena, Manoj; Harish, Sabarigirivasan; Patil, Chetan B; Kewlani, Jai Prakash

    2015-01-01

    Isolated pulmonary cysticercosis is extremely rare manifestation of a rather common disease which is distributed worldwide. Most common sites which provide perfect nourishment for the growth of cysticercosis are muscle and brain followed by eye. Pulmonary involvement in cysticercosis is very rare and if at all present, then ill-defined nodular shadows distributed throughout the lung is the usual radiological presentation. No case of cysticercosis presenting as lung cavity with pleural effusion has been reported so far in literature. We came across a rarest presentation of cysticercosis as cavity in the lung with effusion. After nullifying all the differential diagnosis of cavitary lung lesions, a diagnosis of pulmonary cysticercosis was made by histopathological examination of the lung cavity aspirate and enzyme linked immunosorbent assay (ELISA) for cysticercosis. Case was successfully treated with albendazole (15mg/kg) with steroid cover.

  20. 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).

  1. In situ growth rate measurements by normal-incidence reflectance during MOVPE growth

    SciTech Connect

    Hou, H.Q.; Breiland, W.G.; Hammons, B.E.; Chui, H.C.

    1996-05-01

    We present an in situ technique for monitoring metal-organic vapor phase epitaxy growth by normal-incidence reflectance. This technique is used to calibrate the growth rate periodically and to monitor the growth process routinely. It is not only a precise tool to measure the growth rate, but also very useful in identifying unusal problems during a growth run, such as depletion of source material, deterioration of surface morphology, and problems associated with an improper growht procedure. We will also present an excellent reproducibility ({+-}0.3% over a course of more than 100 runs) of the cavity wavelength of vertical-cavity surface emitting laser structures with periodic calibration by this in situ technique.

  2. Perturbing Open Cavities: Anomalous Resonance Frequency Shifts in a Hybrid Cavity-Nanoantenna System

    NASA Astrophysics Data System (ADS)

    Ruesink, Freek; Doeleman, Hugo M.; Hendrikx, Ruud; Koenderink, A. Femius; Verhagen, Ewold

    2015-11-01

    The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics, and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here, we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a nontrivial phase relation between cavity and nanoparticle radiation, allowing backaction via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems.

  3. Perturbing Open Cavities: Anomalous Resonance Frequency Shifts in a Hybrid Cavity-Nanoantenna System.

    PubMed

    Ruesink, Freek; Doeleman, Hugo M; Hendrikx, Ruud; Koenderink, A Femius; Verhagen, Ewold

    2015-11-13

    The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics, and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here, we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a nontrivial phase relation between cavity and nanoparticle radiation, allowing backaction via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems. PMID:26613442

  4. 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.

  5. Demonstration of superconducting micromachined cavities

    NASA Astrophysics Data System (ADS)

    Brecht, T.; Reagor, M.; Chu, Y.; Pfaff, W.; Wang, C.; Frunzio, L.; Devoret, M. H.; Schoelkopf, R. J.

    2015-11-01

    Superconducting enclosures will be key components of scalable quantum computing devices based on circuit quantum electrodynamics. Within a densely integrated device, they can protect qubits from noise and serve as quantum memory units. Whether constructed by machining bulk pieces of metal or microfabricating wafers, 3D enclosures are typically assembled from two or more parts. The resulting seams potentially dissipate crossing currents and limit performance. In this letter, we present measured quality factors of superconducting cavity resonators of several materials, dimensions, and seam locations. We observe that superconducting indium can be a low-loss RF conductor and form low-loss seams. Leveraging this, we create a superconducting micromachined resonator with indium that has a quality factor of two million, despite a greatly reduced mode volume. Inter-layer coupling to this type of resonator is achieved by an aperture located under a planar transmission line. The described techniques demonstrate a proof-of-principle for multilayer microwave integrated quantum circuits for scalable quantum computing.

  6. Single-longitudinal-mode linear-cavity fiber laser using multiple subring-cavities

    NASA Astrophysics Data System (ADS)

    Liaw, S. K.; Wang, S.; Shin, C. S.; Chen, N. K.; Hsu, K. C.; Manshina, A.; Tver'yanovich, Y.; Su, C.-F.; Wang, L. K.

    2010-07-01

    A single-longitudinal-mode selection is realized in a linear-cavity fiber laser construction using a loop-back optical circulator and a partial reflectance fiber Bragg grating as the cavity ends. At 1551 nm wavelength, the measured signal-to-noise-ratio is 56 dB and with a line width less than 1 MHz obtained using multiple subring cavities as mode filters. The pumping efficiency is 10% improved by recycling the residual pump power to gain medium.

  7. Cold cavity analysis for 35 GHz gyrotron interaction cavity using free space method

    SciTech Connect

    Kumar, Nitin; Saran, Sudeep; Singh, Udaybir; Yadav, Vivek; Sinha, Ashok K.; Jha, B.; Jain, P.K.; Singh, T.P.

    2011-07-01

    The interaction cavity simulated, designed and fabricated for the 35 GHz gyrotron is verified experimentally. Free space method for the Q value and resonant frequency measurement is used in the experiments. The WR22 waveguide based antenna system, Agilent Vector Network Analyzer are used as the experimental set-up in the cavity measurement. The simulation results for the same cavity are also obtained by using the electromagnetic simulator MAGIC for the comparison. (author)

  8. Nb3Sn for Radio Frequency Cavities

    SciTech Connect

    Godeke, A.

    2006-12-18

    In this article, the suitability of Nb3Sn to improve theperformance of superconducting Radio-Frequency (RF)cavities is discussed.The use of Nb3Sn in RF cavitiesis recognized as an enabling technology toretain a veryhigh cavity quality factor (Q0) at 4.2 K and tosignificantly improve the cavity accelerating efficiency per unitlength(Eacc). This potential arises through the fundamental properties ofNb3Sn. The properties that are extensively characterized in theliterature are, however, mainly related to improvements in currentcarrying capacity (Jc) in the vortex state. Much less is available forthe Meissner state, which is of key importance to cavities. Relevantdata, available for the Meissner state is summarized, and it is shown howthis already validates the use of Nb3Sn. In addition, missing knowledgeis highlighted and suggestions are given for further Meissner statespecific research.

  9. Stability of proteins inside a hydrophobic cavity

    NASA Astrophysics Data System (ADS)

    Radhakrishna, Mithun; Sharma, Sumit; Kumar, Sanat K.

    2011-03-01

    Previous studies have shown that enclosing a protein in an athermal cavity stabilizes the protein against reversible unfolding by virtue of eliminating many open chain conformations. Examples of such confined spaces include pores in chromatographic columns, Anfinsen's cage in Chaperonins, interiors of Ribosomes or regions of steric occlusion inside cells. However, the situation is more complex inside a hydrophobic cavity. The protein has a tendency to adsorb on the surface of the hydrophobic cavity, but at the same time it loses conformational entropy because of confinement. We study this system using a simple Hydrophobic Polar (HP) lattice protein model. Canonical Monte Carlo (MC) simulations at different temperatures and surface hydrophobicity show that proteins are stabilized at low and moderate hydrophobicity upon adsorption. The range of surface hydrophobicity over which a protein is stable increases with a decrease in radius of the cavity.

  10. Deflecting light into resonant cavities for spectroscopy

    DOEpatents

    Zare, Richard N. (Stanford, CA); Martin, Juergen (Harxheim, DE); Paldus, Barbara A. (Stanford, CA)

    1998-01-01

    Light is coupled into a cavity ring down spectroscopy (CRDS) resonant cavity using an acousto-optic modulator. The AOM allows in-coupling efficiencies in excess of 40%, which is two to three orders of magnitude higher than in conventional systems using a cavity mirror for in-coupling. The AOM shutoff time is shorter than the roundtrip time of the cavity. The higher light intensities lead to a reduction in shot noise, and allow the use of relatively insensitive but fast-responding detectors such as photovoltaic detectors. Other deflection devices such as electro-optic modulators or elements used in conventional Q-switching may be used instead of the AOM. The method is particularly useful in the mid-infrared, far-infrared, and ultraviolet wavelength ranges, for which moderately reflecting input mirrors are not widely available.

  11. Constant field gradient planar coupled cavity structure

    DOEpatents

    Kang, Yoon W. (Naperville, IL); Kustom, Robert L. (Oswego, IL)

    1999-01-01

    A cavity structure having at least two opposing planar housing members spaced apart to accommodate the passage of a particle beam through the structure between the members. Each of the housing members have a plurality of serially aligned hollows defined therein, and also passages, formed in the members, which interconnect serially adjacent hollows to provide communication between the hollows. The opposing planar housing members are spaced and aligned such that the hollows in one member cooperate with corresponding hollows in the other member to form a plurality of resonant cavities aligned along the particle beam within the cavity structure. To facilitate the obtaining of a constant field gradient within the cavity structure, the passages are configured so as to be incrementally narrower in the direction of travel of the particle beam. In addition, the spacing distance between the opposing housing members is configured to be incrementally smaller in the direction of travel of the beam.

  12. Atom Interferometry in an Optical Cavity

    NASA Astrophysics Data System (ADS)

    Hamilton, Paul; Jaffe, Matt; Brown, Justin M.; Maisenbacher, Lothar; Estey, Brian; Müller, Holger

    2015-03-01

    We propose and demonstrate a new scheme for atom interferometry, using light pulses inside an optical cavity as matter wave beam splitters. The cavity provides power enhancement, spatial filtering, and a precise beam geometry, enabling new techniques such as low power beam splitters (<100 ? W ), large momentum transfer beam splitters with modest power, or new self-aligned interferometer geometries utilizing the transverse modes of the optical cavity. As a first demonstration, we obtain Ramsey-Raman fringes with >75 % contrast and measure the acceleration due to gravity, g , to 60 ? g /?{Hz } resolution in a Mach-Zehnder geometry. We use >107 cesium atoms in the compact mode volume (600 ? m 1 /e2 waist) of the cavity and show trapping of atoms in higher transverse modes. This work paves the way toward compact, high sensitivity, multiaxis interferometry.

  13. Deflecting light into resonant cavities for spectroscopy

    DOEpatents

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

    1998-09-29

    Light is coupled into a cavity ring down spectroscopy (CRDS) resonant cavity using an acousto-optic modulator. The AOM allows in-coupling efficiencies in excess of 40%, which is two to three orders of magnitude higher than in conventional systems using a cavity mirror for in-coupling. The AOM shutoff time is shorter than the roundtrip time of the cavity. The higher light intensities lead to a reduction in shot noise, and allow the use of relatively insensitive but fast-responding detectors such as photovoltaic detectors. Other deflection devices such as electro-optic modulators or elements used in conventional Q-switching may be used instead of the AOM. The method is particularly useful in the mid-infrared, far-infrared, and ultraviolet wavelength ranges, for which moderately reflecting input mirrors are not widely available. 5 figs.

  14. Survival probability time distribution in dielectric cavities

    E-print Network

    Jung-Wan Ryu; Soo-Young Lee; Chil-Min Kim; Young-Jai Park

    2005-10-04

    We study the survival probability time distribution (SPTD) in dielectric cavities. In a circular dielectric cavity the SPTD has an algebraic long time behavior, $\\sim t^{-2}$ in both TM and TE cases, but shows different short time behaviors due to the existence of the Brewster angle in TE case where the short time behavior is exponential. The SPTD for a stadium-shaped cavity decays exponentially, and the exponent shows a relation of $\\gamma \\sim n^{-2}$, $n$ is the refractive index, and the proportional coefficient is obtained from a simple model of the steady probability distribution. We also discuss about the SPTD for a quadrupolar deformed cavity and show that the long time behavior can be algebraic or exponential depending on the location of islands.

  15. Rabi oscillation in a quantum cavity

    E-print Network

    Pierre-Olivier Guimond; Alexandre Roulet; Huy Nguyen Le; Valerio Scarani

    2015-05-29

    We investigate the Rabi oscillation of an atom placed inside a quantum cavity where each mirror is formed by a chain of atoms trapped near a one-dimensional waveguide. This proposal was studied previously with the use of Markov approximation, where the delay due to the finite travel time of light between the two cavity mirrors is neglected. We show that Rabi oscillation analogous to that obtained with high-finesse classical cavities is achieved only when this travel time is much larger than the time scale that characterizes the collective response of the atomic chain. Therefore, the delay must be taken into account and the dynamics of the problem is inherently non-Markovian. Parameters of interest such as the Rabi frequency and the cavity loss rate due to photon leakage through the mirrors are obtained.

  16. Nasal Cavity and Paranasal Sinus Cancer

    MedlinePLUS

    ... Cancer.Net Editorial Board , which is composed of medical, surgical, radiation, gynecologic, and pediatric oncologists, oncology nurses, physician assistants, social workers, and patient advocates. Cancer.Net Guide Nasal Cavity ...

  17. Cavity squeezing by a quantum conductor

    NASA Astrophysics Data System (ADS)

    Mendes, Udson C.; Mora, Christophe

    2015-11-01

    Hybrid architectures integrating mesoscopic electronic conductors with resonant microwave cavities have a great potential for investigating unexplored regimes of electron–photon coupling. In this context, producing nonclassical squeezed light is a key step towards quantum communication with scalable solid-state devices. Here we show that parametric driving of the electronic conductor induces a squeezed steady state in the cavity. We find that squeezing properties of the cavity are essentially determined by the electronic noise correlators of the quantum conductor. In the case of a tunnel junction, we predict that squeezing is optimized by applying a time-periodic series of quantized ?—peaks in the bias voltage. For an asymmetric quantum dot, we show that a sharp Leviton pulse is able to achieve perfect cavity squeezing.

  18. Photon filters in a microwave cavity

    E-print Network

    J. Larson; S. Stenholm

    2003-04-25

    In an earlier paper we have concluded that time-dependent parameters in atom-mode interaction can be utilized to modify the quantum field in a cavity. When an atom shoots through the cavity field, it is expected to experience a trigonometric time dependence of its coupling constant. We investigate the possibilities this offers to modify the field. As a point of comparison we use the solvable Rosen-Zener model, which has parameter dependencies roughly similar to the ones expected in a real cavity. We do confirm that by repeatedly sending atoms through the cavity, we can obtain filters on the photon states. Highly non-classical states can be obtained. We find that the Rosen-Zener model is more sensitive to the detuning than the case of a trigonometric coupling.

  19. Plasma Treatment of Niobium SRF Cavity Surfaces

    SciTech Connect

    J. Upadhyay, M. Raskovic, L. Vuskovic, S. Popovic, A.-M. Valente-Feliciano, L. Phillips

    2010-05-01

    Plasma based surface modification provides an excellent opportunity to eliminate non- superconductive pollutants in the penetration depth region of the SRF cavity surface and to remove mechanically damaged surface layer improving surface roughness. We have demonstrated on flat samples that plasma etching in Ar / Cl2 of bulk Nb is a viable alternative surface preparation technique to BCP and EP methods, with comparable etching rates. The geometry of SRF cavities made of bulk Nb defines the use of asymmetric RF discharge configuration for plasma etching. In a specially designed single cell cavity with sample holders, discharge parameters are combined with etched surface diagnostics to obtain optimum combination of etching rates, roughness and homogeneity in a variety of discharge types, conditions, and sequences. The optimized experimental conditions will ultimately be applied to single cell SRF cavities.

  20. High-harmonic gyrotron with sectioned cavity

    SciTech Connect

    Bandurkin, I. V.; Kalynov, Yu. K.; Savilov, A. V.

    2010-07-15

    High-harmonic large-orbit gyrotrons require long-length operating cavities because of both a weak electron-wave coupling and relatively low electron currents. Since diffraction Q factors of such cavities are very high, a large fraction of the radiated power is dissipated in Ohmic losses. A sectioned klystronlike cavity can be a way to combine a long electron-wave interaction region with a relatively low diffraction Q factor. In this paper, a design of a third-harmonic terahertz gyrotron is studied in detail and discussed. As compared to a regular cavity, the use of a sectioned microwave system provides an enhancement of the output rf power by several times along with the halving of the Ohmic losses.

  1. Progressive cavity pump for downhole inflatable packer

    SciTech Connect

    Clark, J.A.

    1992-03-24

    This patent describes a downhole inflatable packer pump. It comprises: case means for attaching to a lower testing string portion and having an inlet and an outlet, the outlet being communicable with an inflatable packer at a location below the pump; mandrel means, rotatably disposed within the case means, for connecting to an upper testing string portion for mutual rotation therewith and rotating within the case means; an elastomeric pump stator disposed in the case means, the stator having a convoluted inner surface; a rotor extending form the mandrel means and into the stator, the rotor having a convoluted outer surface, the stator and rotor defining a plurality of cavities therebetween, whereby rotation of the rotor within the stator moves fluid progressively from cavity to cavity and thereby from the inlet to the outlet; passageway means for providing fluid communication between the lower testing string portion and the upper testing string portion, the passageway means being sealing separated from the cavities.

  2. Constant field gradient planar coupled cavity structure

    DOEpatents

    Kang, Y.W.; Kustom, R.L.

    1999-07-27

    A cavity structure is disclosed having at least two opposing planar housing members spaced apart to accommodate the passage of a particle beam through the structure between the members. Each of the housing members have a plurality of serially aligned hollows defined therein, and also passages, formed in the members, which interconnect serially adjacent hollows to provide communication between the hollows. The opposing planar housing members are spaced and aligned such that the hollows in one member cooperate with corresponding hollows in the other member to form a plurality of resonant cavities aligned along the particle beam within the cavity structure. To facilitate the obtaining of a constant field gradient within the cavity structure, the passages are configured so as to be incrementally narrower in the direction of travel of the particle beam. In addition, the spacing distance between the opposing housing members is configured to be incrementally smaller in the direction of travel of the beam. 16 figs.

  3. Atom interferometry in an optical cavity.

    PubMed

    Hamilton, Paul; Jaffe, Matt; Brown, Justin M; Maisenbacher, Lothar; Estey, Brian; Müller, Holger

    2015-03-13

    We propose and demonstrate a new scheme for atom interferometry, using light pulses inside an optical cavity as matter wave beam splitters. The cavity provides power enhancement, spatial filtering, and a precise beam geometry, enabling new techniques such as low power beam splitters (<100???W), large momentum transfer beam splitters with modest power, or new self-aligned interferometer geometries utilizing the transverse modes of the optical cavity. As a first demonstration, we obtain Ramsey-Raman fringes with >75% contrast and measure the acceleration due to gravity, g, to 60???g/sqrt[Hz] resolution in a Mach-Zehnder geometry. We use >10(7) cesium atoms in the compact mode volume (600???m 1/e(2) waist) of the cavity and show trapping of atoms in higher transverse modes. This work paves the way toward compact, high sensitivity, multiaxis interferometry. PMID:25815912

  4. General recipe for designing photonic crystal cavities

    E-print Network

    Vuckovic, Jelena

    in the lowest-order whispering gallery mode," Appl. Phys. Lett. 80, 3883­3885 (2002). 7. P. Lalanne, S. Mias.-H. Lee, "High quality-factor whispering-gallery mode in the photonic crystal hexagonal disk cavity," Opt

  5. Wakefield Damping for the CLIC Crab Cavity

    SciTech Connect

    Ambattu, P.K.; Burt, G.; Dexter, A.C.; Carter, R.G.; Khan, V.; Jones, R.M.; Dolgashev, V.; /SLAC

    2011-12-01

    A crab cavity is required in the CLIC to allow effective head-on collision of bunches at the IP. A high operating frequency is preferred as the deflection voltage required for a given rotation angle and the RF phase tolerance for a crab cavity are inversely proportional to the operating frequency. The short bunch spacing of the CLIC scheme and the high sensitivity of the crab cavity to dipole kicks demand very high damping of the inter-bunch wakes, the major contributor to the luminosity loss of colliding bunches. This paper investigates the nature of the wakefields in the CLIC crab cavity and the possibility of using various damping schemes to suppress them effectively.

  6. Degreasing and cleaning superconducting RF Niobium cavities

    SciTech Connect

    Rauchmiller, Michael; Kellett, Ron; /Fermilab

    2011-09-01

    The purpose and scope of this report is to detail the steps necessary for degreasing and cleaning of superconducting RF Niobium cavities in the A0 clean room. It lists the required equipment and the cleaning procedure.

  7. Reentrant Klystron Cavity as an Electromechanical Transducer

    E-print Network

    cylindrical and conical inserts are examined to quantify the resonant frequency dependence on the gap spacing of the resonant frequency (in some cases the error may be larger than 40%) as its derivation lacks the cavity

  8. Cavity squeezing by a quantum conductor

    E-print Network

    Udson C. Mendes; Christophe Mora

    2015-11-06

    Hybrid architectures integrating mesoscopic electronic conductors with resonant microwave cavities have a great potential for investigating unexplored regimes of electron-photon coupling. In this context, producing nonclassical squeezed light is a key step towards quantum communication with scalable solid-state devices. Here we show that parametric driving of the electronic conductor induces a squeezed steady state in the cavity. We find that squeezing properties of the cavity are essentially determined by the electronic noise correlators of the quantum conductor. In the case of a tunnel junction, we predict that squeezing is optimized by applying a time-periodic series of quantized $\\delta-$peaks in the bias voltage. For an asymmetric quantum dot, we show that a sharp Leviton pulse is able to achieve perfect cavity squeezing.

  9. Diffusion-limited interaction of dislocation loops and interstitials during dry oxidation in silicon

    E-print Network

    Florida, University of

    Diffusion-limited interaction of dislocation loops and interstitials during dry oxidation reduction of OED (oxidation enhanced diffusion) of boron in a buried layer due to very efficient interstitial capturing action of dislocation loops, suggesting diffusion-limited dislocation loop growth

  10. STATISTICAL MODEL FOR SCATTERING MATRICES OF OPEN CAVITIES

    E-print Network

    Anlage, Steven

    STATISTICAL MODEL FOR SCATTERING MATRICES OF OPEN CAVITIES Thomas M. Antonsen, Xing Zheng, Edward electromagnetic cavities with several transmission lines or waveguides connected to the cavity. The model is based on assumed properties of chaotic eigenfunctions for the closed system. Statistical properties of the cavity

  11. Exploring Geometries of SRF Cavities for a Future Muon Collider

    E-print Network

    Geng, Rong-Li

    Exploring Geometries of SRF Cavities for a Future Muon Collider Rong-Li Geng LEPP, Cornell application of super- conducting RF cavities in a future muon collider. Such RF cavities are expected to work in the frequency range of about 100 MHz, which makes the cavity diameter to be about 3 meters for a \\typi- cal

  12. ELECTROMAGNETIC CAVITIES AS ELECTROMECHANICAL TRANSDUCERS: THEORY AND EXPERIMENT

    E-print Network

    ELECTROMAGNETIC CAVITIES AS ELECTROMECHANICAL TRANSDUCERS: THEORY AND EXPERIMENT Joaquim J. Barroso on the gap spacing between the end of the nical insert and the cavity plate in reentrant 1.0 GHz ystron cavities. Fabricated from aluminum, the cavities sted are 80 mm in diameter with the top plate 1-mm ck

  13. Kinetic aspects of foreshock cavities Steven J. Schwartz,1

    E-print Network

    California at Berkeley, University of

    Kinetic aspects of foreshock cavities Steven J. Schwartz,1 David Sibeck,2 Mark Wilber,3 Karim, a foreshock cavity. Such cavities are believed to be formed when an isolated collection of interplanetary to flow upstream and excavate a local cavity. Observations by the Cluster spacecraft show precisely

  14. Magnetic field mapping for HIE-ISOLDE cavities

    E-print Network

    Gagnon, Pauline

    Magnetic field mapping for HIE-ISOLDE cavities Antonio Bianchi University of Torino, Italy antonio of a new LINAC, composed of five superconducting cavities per cryomodule. 1.1 HIE-ISOLDE cavities The HIE-ISOLDE cavities are made up of two different parts in copper: a cylinder and an antenna inside. They are welded

  15. Cavity polaritons in an organic single-crystalline rubrene microcavity

    NASA Astrophysics Data System (ADS)

    Tsuchimoto, Yuta; Nagai, Hikaru; Amano, Masamitsu; Bando, Kazuki; Kondo, Hisao

    2014-06-01

    We fabricated a single-crystalline rubrene microcavity using a simple solution technique and observed cavity polaritons in the microcavity at room temperature (RT). Large Rabi splitting energies were obtained from dispersion of the cavity polaritons. Furthermore, photoluminescence from the cavity polaritons was observed at RT. The findings will be of importance for the application of cavity polaritons.

  16. Two cavity autoacceleration of an intense relativistic electron beam

    SciTech Connect

    Coleman, P.D.; Lockner, T.R.

    1985-01-01

    Two autoacceleration cavities have been used to accelerate an 11-kA electron beam from 2 MeV to approx. =2.8 MeV. The two 40-..cap omega.. cavities each accelerated the beam by approx. =400 kV with no observable interaction between the two cavities over several cavity transmit times. 6 figs.

  17. Liquid metal flow encasing a magnetic cavity

    SciTech Connect

    Hassam, A. B.; Drake, J. F.; Goel, Deepak; Lathrop, D. P.

    2000-04-01

    A stationary equilibrium of a liquid metal flowing past a cylindrical magnetic cavity is presented. The cavity has an azimuthal magnetic field and can also have an axial field. The liquid metal flow can be maintained by a sufficiently high pressure head. The scheme could be used to support a flowing liquid wall for systems producing high heat fluxes. (c) 2000 American Institute of Physics.

  18. Polarisation losses in a ring prism cavity

    SciTech Connect

    Kuryatov, V N; Sokolov, A L

    2000-02-28

    The polarisation losses in a ring cavity, formed by total-internal-reflection prisms, were analysed. All the sources of the polarisation losses are indicated and expressions for their calculation are presented. The limit to loss reduction in cavities of this kind, set by the difference between the radii of curvature of the radiation wavefront and of the refracting prism faces, was determined. (laser gyroscopes)

  19. Hybrid cavity mechanics with doped systems

    E-print Network

    Aurelien Dantan; Bhagya Nair; Guido Pupillo; Claudiu Genes

    2014-06-27

    We investigate the dynamics of a mechanical resonator in which is embedded an ensemble of two-level systems interacting with an optical cavity field. We show that this hybrid approach to optomechanics allows for enhanced effective interactions between the mechanics and the cavity field, leading for instance to ground state cooling of the mechanics, even in regimes, like the unresolved sideband regime, in which standard radiation pressure cooling would be inefficient.

  20. Exploration of very high gradient cavities

    SciTech Connect

    Grigory Eremeev

    2011-07-01

    Several of the 9-cell ILC cavities processed at Jlab within ongoing ILC R&D program have shown interesting behavior at high fields, such as mode mixing and sudden field emission turn-on during quench. Equipped with thermometry and oscillating superleak transducer (OST) system for quench detection, we couple our RF measurements with local dissipation measurements. In this contribution we report on our findings with high gradient SRF cavities.