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1

Coble Creep, Cavity Sintering, and Cavity Growth.  

National Technical Information Service (NTIS)

The close relationships between Coble creep, cavity sintering and cavity growth are discussed. The measurement of size distributions of crack-like cavities is useful for determining grain boundary and surface diffusivities. In nickel aluminide (Ni3Al) int...

J. H. Schneibel, L. Martinez

1988-01-01

2

Fabrication of whispering gallery mode cavity using crystal growth  

E-print Network

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

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

2013-01-01

3

Diffuse interface model of diffusion-limited crystal growth  

Microsoft Academic Search

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

Joseph B. Collins; Herbert Levine

1985-01-01

4

Diffuse glioma growth: a guerilla war  

PubMed Central

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

Idema, Albert J.; Wesseling, Pieter

2007-01-01

5

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

NASA Astrophysics Data System (ADS)

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) 10-5 and (1.427 0.009) 10-7 m2 s-1, respectively, in very good agreement with accepted literature values.

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

2013-12-01

6

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

SciTech Connect

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.

Shen, Jun, E-mail: jun.shen@nrc-cnrc.gc.ca; Zhou, Jianqin; Gu, Caikang [Energy, Mining and Environment Portfolio, National Research Council Canada, 4250 East Mall, Vancouver, British Columbia V6T 1W5 (Canada)] [Energy, Mining and Environment Portfolio, National Research Council Canada, 4250 East Mall, Vancouver, British Columbia V6T 1W5 (Canada); Neill, Stuart [Energy, Mining and Environment Portfolio, National Research Council Canada, 1200 Montreal Road, Building M-9, Ottawa, Ontario K1A 0R6 (Canada)] [Energy, Mining and Environment Portfolio, National Research Council Canada, 1200 Montreal Road, Building M-9, Ottawa, Ontario K1A 0R6 (Canada); Michaelian, Kirk H.; Fairbridge, Craig [CanmetENERGY, Natural Resources Canada, One Oil Drive Patch, Devon, Alberta T9G 1A8 (Canada)] [CanmetENERGY, Natural Resources Canada, One Oil Drive Patch, Devon, Alberta T9G 1A8 (Canada); Astrath, Nelson G. C.; Baesso, Mauro L. [Departamento de Fsica, Universidade Estadual de Maring, Av. Colombo 5790, Maring, Paran 87020-900 (Brazil)] [Departamento de Fsica, Universidade Estadual de Maring, Av. Colombo 5790, Maring, Paran 87020-900 (Brazil)

2013-12-15

7

In-Situ Microtomographic Characterization of Single-Cavity Growth During High-Temperature Creep of Leaded Brass  

NASA Astrophysics Data System (ADS)

Synchrotron microtomography was used for in-situ characterization of high-temperature creep damage in leaded brass. Applying image registration to subsequent tomographic reconstructions, the volumetric growth rate of single cavities with equivalent radii between 2 and 4.3 ?m was assessed. We conclude from the volume dependence of the growth rates that both the viscous flow and grain boundary (GB) diffusion mechanisms influence void growth. We show that void growth in leaded brass is retarded by negative stress triaxiality, which develops in the matrix during heating the specimen to the deformation temperature.

Isaac, A.; Dzieciol, K.; Sket, F.; Borbly, A.

2011-10-01

8

Diffusive relaxation of stress concentrations at grain boundary cavities in elevated temperature creep  

Microsoft Academic Search

Elevated temperature creep cavitation of grain boundaries under cyclic and rapidly applied loading was studied. The response of partially damaged materials (where damage is represented as crack line cavities on the grain boundaries) following load alterations at relatively low stress levels and at temperatures in the vicinity of 0.5 t sub m or higher. The interaction between grain boundary diffusion

A. A. Rubinstein

1982-01-01

9

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

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

10

Volume Diffusion Growth Kinetics and Step Geometry in Crystal Growth  

NASA Technical Reports Server (NTRS)

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.

Mazuruk, Konstantin; Ramachandran, Narayanan

1998-01-01

11

Variational analysis of the natural decay rates and eigenmodes of cavity-enclosed diffusive fields  

NASA Astrophysics Data System (ADS)

A variational approach to the analysis of the natural decay rates and eigenmodes of cavity-enclosed diffusive fields in general anisotropic and heterogeneous materials is presented. In the bulk material, diffusivity and volume relaxivity are accounted for. The interaction of the cavity's medium with the embedding material is modeled via a surface relaxivity on the boundary surface. The pertaining eigenmodes are proven to be orthogonal and to form a complete expansion of an initially excited diffusive field. In view of the variational approach, a finite-element type of computation presents itself as the natural tool for numerics. The resulting implementation on a simplicial mesh allows for the modeling of cavities of arbitrary shape. To investigate the feasibility of using the approach in the inverse problem of reconstructing the shape and size of cavities from measured values of the natural decay rates of the eigenmodes, we carry out a number of numerical experiments on the forward problem. They demonstrate the method to be simple and robust, both in 2D and 3D complex geometries. For a benchmark problem with a known analytic solution, error estimates are presented. Applications are found in, for example, nuclear magnetic resonance imaging of subsurface rock pore geometry, biological cell structure and the analysis of neurological defects in medical diagnostics.

de Hoop, Adrianus T.; Prange, Michael D.

2007-10-01

12

Generalized Thermoelastic Diffusion Problem for an Infinite Medium with a Spherical Cavity  

NASA Astrophysics Data System (ADS)

In this study, the problem of a thermoelastic infinite medium with a spherical cavity is considered in the context of 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 heating. Laplace transform techniques are used. The solution is obtained in the Laplace transform domain by using a direct approach. The solution of the problem in the physical domain in obtained numerically using a method based on Fourier expansion techniques. The temperature, displacement, stress, and concentration as well as the chemical potential are obtained. Numerical computations are carried out and represented graphically.

Elhagary, M. A.

2012-01-01

13

Radiant emission characteristics of isothermal diffuse cylindrical-inner-cone cavities  

NASA Astrophysics Data System (ADS)

A new calculation of the local hemispherical effective emissivities along an isothermal diffuse cylindrical-inner-cone cavity has been made. Results are presented for cylindrical inner cones with dimensions such that the effective emissivities along the inner cones and the surface nearby are very close to unity. Comparison is made between Bedford-Ma techniques and the present method for a cone half-angle of 90 deg. Results show that high accuracy can be obtained with the method, especially for cavities with high surface emissivity, long cylinder length, and small aperture radius.

Chu, Z.; Chen, S.; Chen, H.

1980-10-01

14

Partial heating and partial salting on double-diffusive convection in an open cavity  

NASA Astrophysics Data System (ADS)

Double-diffusive natural convection in an open top square cavity and partially heated from the side is studied numerically. Constant temperatures and concentration are imposed along the right and left walls while the heat balance at the surface is assumed to obey Newton's law of cooling. The finite difference method is used to solve the dimensionless governing equations. The numerical results are reported for the effects of Marangoni number and different heater locations on the contours of streamlines, temperature and concentration. The heat and mass transfer rate in the cavity are measured in terms of the average Nusselt and Sherwood numbers.

Arbin, N.; Hashim, I.

2014-09-01

15

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

SciTech Connect

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.

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

2010-03-09

16

Simulation study on cavity growth in ductile metal materials under dynamic loading  

NASA Astrophysics Data System (ADS)

Cavity growth in ductile metal materials under dynamic loading is investigated via the material point method. Two typical cavity effects in the region subjected to rarefaction wave are identified: (i) part of material particles flow away from the cavity in comparison to the initial loading velocity, (ii) local regions show weaker negative or even positive pressures. Neighboring cavities interact via coalescence of isobaric contours. The growth of cavity under tension shows staged behaviors. After the initial slow stage, the volume and the dimensions in both the tensile and transverse directions show linear growth rate with time until the global tensile wave arrives at the upper free surface. It is interesting that the growth rate in the transverse direction is faster than that in the tensile direction. The volume growth rate linearly increases with the initial tensile velocity. After the global tensile wave passed the cavity, both the maximum particle velocity in the tensile direction and the maximum particle velocity in the opposite direction increase logarithmically with the initial tensile speed. The shock wave reflected back from the cavity and compression wave from the free surface induce the initial behavior of interfacial instabilities such as the Richtmyer-Meshkov instability, which is mainly responsible for the irregularity in the morphology of deformed cavity. The local temperatures and distribution of hot spots are determined by the plastic work. Compared with the dynamical process, the heat conduction is much slower.

Xu, Ai-Guo; Zhang, Guang-Cai; Ying, Yang-Jun; Yu, Xi-Jun

2013-08-01

17

Simulation study on cavity growth in ductile metal materials under dynamic loading  

E-print Network

Cavity growth in ductile metal materials under dynamic loading is investigated via the material point method. Two typical cavity effects in the region subjected to rarefaction wave are identified: (i) part of material particles flow away from the cavity in comparison to the initial loading velocity, (ii) local regions show weaker negative or even positive pressures. Neighboring cavities interact via coalescence of isobaric contours. The growth of cavity under tension shows staged behaviors. After the initial slow stage, the volume and the dimensions in both the tensile and transverse directions show linear growth rate with time until the global tensile wave arrives at the upper free surface. It is interesting that the growth rate in the transverse direction is faster than that in the tensile direction. The volume growth rate linearly increases with the initial tensile velocity. After the global tensile wave passed the cavity, both the maximum particle velocity in the tensile direction and the maximum particle velocity in the opposite direction increase logarithmically with the initial tensile speed. The shock wave reflected back from the cavity and compression wave from the free surface induce the initial behavior of interfacial instabilities such as the Richtmyer-Meshkov instability, which is mainly responsible for the irregularity in the morphology of deformed cavity. The local temperatures and distribution of hot spots are determined by the plastic work. Compared with the dynamical process, the heat conduction is much slower.

Aiguo Xu; Guangcai Zhang; Yangjun Ying; Xijun Yu

2013-08-31

18

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

DOEpatents

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.

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

1995-03-14

19

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

NASA Astrophysics Data System (ADS)

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: (0.14450.0002)10-2 cm2/s (distilled water); (0.09220.0002)10-2 cm2/s (glycerol); (0.09180.0002)10-2 cm2/s (ethylene glycol); and (0.08810.0004)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.

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

2000-07-01

20

Transient Effects in Creep Cavity Nucleation and Early Growth in Ceramics.  

National Technical Information Service (NTIS)

Creep fracture of ceramic materials frequently occurs by the nucleation, growth, and coalescence of grain boundary cavities. Results of recent experimental studies of cavitation kinetics in compression crept ceramics are presented to illustrate the transi...

R. A. Page, K. S. Chan

1989-01-01

21

Sucrose Release into the Endosperm Cavity of Wheat Grains Apparently Occurs by Facilitated Diffusion across the Nucellar Cell Membranes  

Microsoft Academic Search

Nutrients required for the growth of the embryo and endosperm of developing wheat (Triticum aestivum L.) grains are released into the endosperm cavity from the maternal tissues across the nucellar cell plasma membranes. We followed the uptake and efflux of sugars into and out of the nucellus by slicing grains longitudinally through the endosperm cavity to expose the nucellar surface

Ning Wang; Donald B. Fisher

22

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

SciTech Connect

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

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

2010-06-15

23

Regulation of ramified electrochemical growth by a diffusive wave  

NASA Astrophysics Data System (ADS)

The role of ion transport during ramified growth in a dilute, binary electrolyte is investigated by obtaining a wave solution to effective equations derived by asymptotic analysis of the Nernst transport equations. The concentration profile exhibits a diffusion layer ahead of the growing tips, in agreement with experiment and theory. The non-Laplacian electric field is stronger in the diffusion layer than in the bulk, and cations are accelerated through the layer toward the tips. The well-known growth speed of the aggregate envelope, roughly equal to the speed of migrating anions in the bulk emerges as the characteristic wave speed of our equations. The ``copper ratio'' is also predicted and is linked to the regulation of growth by the diffusive wave. Finally, an estimate of the induction time for ramified growth is derived, based on the idea that a critical diffusion layer width must be attained.

Bazant, Martin Z.

1995-08-01

24

Anormal growth of cavities in MeV He implanted Si covered with a thin Al foil  

Microsoft Academic Search

Cavities were created by MeV He implantation in silicon through a 1.5?m Al foil. After a 800 C-annealing, unexpected growth mechanism was found: a non-uniform layer of cavities with a distribution where bigger cavities are surrounded by smaller ones. Neither Oswald ripening nor migration-coalescence mechanisms can be applied to describe the growth of these cavities. The role of dislocations seem

R. Delamare; E. Ntsoenzok; F. Labohm; A. van Veen; J. Grisolia; A. Claverie

2002-01-01

25

Anormal growth of cavities in MeV He implanted Si covered with a thin Al foil  

NASA Astrophysics Data System (ADS)

Cavities were created by MeV He implantation in silicon through a 1.5 ?m Al foil. After a 800 C-annealing, unexpected growth mechanism was found: a non-uniform layer of cavities with a distribution where bigger cavities are surrounded by smaller ones. Neither Oswald ripening nor migration-coalescence mechanisms can be applied to describe the growth of these cavities. The role of dislocations seem to be important in that distribution. Indeed some cavities seem to be trapped by dislocations. However the motion of the helium does not appear to be the origin of that anormal growth mechanism.

Delamare, R.; Ntsoenzok, E.; Labohm, F.; van Veen, A.; Grisolia, J.; Claverie, A.

2002-01-01

26

Onset of Double-Diffusive Convection in a Rectangular Cavity and Its Generation Mechanism  

NASA Astrophysics Data System (ADS)

Two-dimensional double diffusive convection in a binary fluid mixture filled in a container with a rectangular cross section is investigated by linear stability analyses, numerical simulations and numerical calculations of steady solutions in the present paper. We mainly consider an ethanol--water mixture as the binary fluid, in which heat and ethanol diffuse in different time scales affecting the fluid motion through buoyancy force and the Soret effect. The bottom of the cavity is kept at a higher temperature than the top, and the side boundary walls are assumed to be perfectly insulating. The impermeability condition of mass is applied on all the boundaries. We obtain the critical condition for the onset of double diffusive convection, and examine the flow field at the criticality. It is found that the most unstable mode of disturbance is oscillatory at the criticality for negative values of the separation number, though it is a steady mode of disturbance for positive or null values of the separation number. We discuss the driving mechanism of the steady and oscillatory convections by evaluating torques exerted on the fluid due to the buoyancy force, the pressure and the viscosity separately in each. We find in numerical simulations that the convection, even if it is oscillatory initially, always attains a steady state in due course in the case of a container with a square cross section. The bifurcation diagram of the steady convection is obtained numerically and the relation between the steady convection and the oscillatory mode of disturbance arising due to the linear instability is briefly discussed.

Mizushima, Jiro; Yasumizu, Yuto; Ohashi, Shunsuke

2013-08-01

27

Water diffusion, Viscosity and Bubble Growth in Silicate Melts  

NASA Astrophysics Data System (ADS)

For quantitative modeling of bubble growth and volcanic eruption dynamics, it is necessary to know H2O diffusivity in the melt. Over the years, we have been experimentally and systematically investigating H2O diffusion in rhyolite, dacite, andeside, basalt, and a per-alkaline rhyolite (1-7; as well as work in progress). We have also investigated viscosity of hydrous melts and developed a viscosity model for all natural silicate melts (8-10). In this report, we discuss the compositional dependence of H2O diffusivity and the relation between H2O diffusivity and viscosity. Furthermore, we explore how these parameters affect bubble growth rate in various melts. Experimental data show that in contrast to the large differences in viscosity of various melts, the variation of H2O diffusivity with melt composition is in general small, especially at super-liquidus temperatures. For example, when per-alkaline rhyolite is compared with calc-alkaline rhyolite, the viscosity difference is large but the diffusivity difference is small. Comparison between rhyolite and dacite is more complicated. At 1423 K (super-liquidus) and 1.0 wt percent total H2O, the viscosity decreases by a factor of 80 from rhyolite to dacite, but the diffusivity increases by less than a factor of 2. However, at 873 K (sub- liquidus) and 1.0 wt percent total H2O, the difference in the calculated viscosities of rhyolite and dacite is negligible, but the diffusivity decreases by a factor of 6 from rhyolite to dacite. Hence, there does not seem to be a consistent relation between viscosity and H2O diffusivity. When modeling bubble growth rate in different melts, the effect of viscosity variation can change bubble growth rate significantly, but the effect due to variation in diffusivity is small at super-liquidus temperatures. References: (1) Behrens et al. (2004) Geochim. Cosmochim. Acta, 68, 5139-5150. (2) Behrens et al. (2007) Earth Planet. Sci. Lett., 254, 69-76. (3) Liu et al. (2004) Chem. Geol., 209, 327-340. (4) Ni and Zhang (2008) Chem. Geol., 250, 68-78. (5) Zhang et al. (1991) Geochim. Cosmochim. Acta, 55, 441-456. (6) Zhang and Stolper (1991) Nature, 351, 306-309. (7) Zhang and Behrens (2000) Chem. Geol., 169, 243-262. (8) Zhang et al. (2003) Am. Mineral., 88, 1741-1752. (9) Zhang and Xu (2007) Geochim. Cosmochim. Acta, 71, 5226-5232. (10) Hui and Zhang (2007) Geochim. Cosmochim. Acta, 71, 403-416.

Zhang, Y.

2008-12-01

28

Spatial embedding of neuronal trees modeled by diffusive growth  

Microsoft Academic Search

The relative importance of the intrinsic and extrinsic factors determining the variety of geometric shapes exhibited by dendritic trees remains unclear. This question was addressed by developing a model of the growth of dendritic trees based on diffusion-limited aggregation process. The model reproduces diverse neuronal shapes (i.e., granule cells, Purkinje cells, the basal and apical dendrites of pyramidal cells, and

Artur Luczak

2006-01-01

29

ENDOGENOUS CYCLICAL GROWTH WITH A SIGMOIDAL DIFFUSION OF INNOVATIONS  

Microsoft Academic Search

The model we propose in this paper is an extension of the one described in Freeman et al. [Freeman, S., Hong, D. and Peled, D. (1999) Endogenous Cycles and Growth with Indivisible Technological Developments. Review of Economics Dynamics, 2, 403432]. In our model, we incorporate the process of diffusion of major innovations and analyze macroeconomic effects on consumption, capital and

Julio Sanchez-Choliz; Francisco Fatas-Villafranca; Gloria Jarne; Isabel Perez-Grasa

2008-01-01

30

Simulation of beam-beam induced emittance growth in the HL-LHC with crab cavities  

E-print Network

The emittance growth in the HL-LHC due to beam-beam effects is examined by virtue of strong-strong computer simulations. A model of the transverse damper and the noise level have been tuned to simulate the emittance growth in the present LHC. Simulations with projected HL-LHC beam parameters and crab cavities are discussed. It is shown that with the nominal working point, the large beam-beam tune shift moves the beam into a resonance that causes substantial emittance growth. Increasing the working point slightly is demonstrated to be very beneficial.

Paret, S

2014-01-01

31

Diffusing species and growth interfaces during cobalt disilicide formation  

NASA Astrophysics Data System (ADS)

The diffusing species and growth interface during CoSi 2 formation has been investigated using a thin Ta layer as well as implanted Xe atoms as markers. Analysis of the position of the markers before and following CoSi 2 formation was carried out using Rutherford backscattering spectrometry. The results showed that when Ta alone was used as a marker it moved deeper into the sample during disilicide formation, thereby suggesting that CoSi 2 growth was by-in-large the result of silicon diffusion to the {CoSi2}/{CoSi} interface. On the other hand, when implanted Xe atoms were used as a marker the results indicated that CoSi 2 growth took place by Co diffusion to the {Si<> }/{CoSi2} interface. In an attempt to try and reconcile these conflicting results a combination of metal marker and implanted Xe atoms was used. On CoSi 2 formation the Ta marker was once again observed to move deeper into the sample while the Xe marker again moved towards the sample's surface. It is argued that the most likely explanation of the cause for the conflicting results is that the implanted Xe atoms agglomerated into bubbles, and that these bubbles were then dragged by the moving phase boundary during silicide growth.

Comrie, C. M.

1996-09-01

32

Nanomechanical characterization of cavity growth and rupture in hydrogen-implanted single-crystal BaTiO3  

E-print Network

Nanomechanical characterization of cavity growth and rupture in hydrogen-implanted single formation is related to the measured mechanical properties to better understand hydrogen implantation- tions in capacitors and gate dielectrics for nonvolatile ran- dom access memory NVRAM devices, actuators

Atwater, Harry

33

Nanomechanical characterization of cavity growth and rupture in hydrogen-implanted single-crystal BaTiO3  

NASA Astrophysics Data System (ADS)

A thermodynamic model of cavity nucleation and growth in ion-implanted single-crystal BaTiO3 layer is proposed, and cavity formation is related to the measured mechanical properties to better understand hydrogen implantation-induced layer transfer processes for ferroelectric thin films. The critical radius for cavity nucleation was determined experimentally from blistering experiments performed under isochronal anneal conditions and was calculated using continuum mechanical models for deformation and fracture, together with thermodynamic models. Based on thermodynamic modeling, we suggest that cavities grow toward the cracking criteria at a critical blister size whereupon gas is emitted from ruptured cavities. The main driving force for layer splitting is the reduction of the overall elastic energy stored in the implanted region during the cavity nucleation and growth as the gaseous H2 entrapped within the cavities is released. Nanoindentation measurements reveal locally the mechanical property changes within the vicinity of a single cavity. Using the measured mechanical properties at the single-cavity level, we developed three-dimensional strain and stress profiles using finite element method.

Park, Young-Bae; Nardi, Patrick; Li, Xiaodong; Atwater, Harry A.

2005-04-01

34

Random ballistic growth and diffusion in symmetric spaces  

E-print Network

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

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

2011-10-16

35

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

E-print Network

because of their wide- spread use as refrigerants, lubricants, and heat exchangers. The utility frequency. The major advantages of cavity-length scans are the fixed noise bandwidth of the sys- tem, which improves the signal-to-noise ratio SNR , as well as disposing with the requirement for instrumental

Mandelis, Andreas

36

Three-dimensional double-diffusive Marangoni convection in a cubic cavity with horizontal temperature and concentration gradients  

NASA Astrophysics Data System (ADS)

Three-dimensional double-diffusive Marangoni convection in a cubic cavity is studied in the present paper. Both the temperature and solute concentration gradients are applied horizontally. Direct numerical simulations are carried out for surface-tension Reynolds number 10?Re?500 , surface-tension ratio -2?R??1 , and Lewis number 1diffusive Marangoni convection in three-dimensional confined cavities with horizontal temperature and concentration gradients.

Zhan, Jie-Min; Chen, Zhi-Wu; Li, Yok-Sheung; Nie, Yu-Hua

2010-12-01

37

Nonequilibrium Cluster Diffusion During Growth and Evaporation in Two Dimensions  

NASA Astrophysics Data System (ADS)

The diffusion of growing or evaporating two-dimensional clusters is investigated. At equilibrium, it is well known that the mean square displacement (MSD) of the cluster center of mass is linear in time. In nonequilibrium conditions, we find that the MSD exhibits a nonlinear time dependence, leading to three regimes: (i) during curvature-driven evaporation, the MSD shows a square-root singularity close to the collapse time; (ii) in slow growth or evaporation, the dynamics is in the Edwards-Wilkinson universality class, and the MSD shows a logarithmic behavior; (iii) far from equilibrium, the dynamics belongs to the Kardar-Parisi-Zhang universality class and the MSD shows a power-law behavior with a characteristic exponent 1/3. These results agree with kinetic Monte Carlo simulations, and can be generalized to other universality classes.

Saito, Yukio; Dufay, Matthieu; Pierre-Louis, Olivier

2012-06-01

38

Two-dimensional diffusion limited system for cell growth  

SciTech Connect

A new cell system, the ''sandwich'' system, was developed to supplement multicellular spheroids as tumor analogues. Sandwiches allow new experimental approaches to questions of diffusion, cell cycle effects and radiation resistance in tumors. In this thesis the method for setting up sandwiches is described both theoretically and experimentally followed by its use in x-ray irradiation studies. In the sandwich system, cells are grown in a narrow gap between two glass slides. Where nutrients and waste products can move into or out of the local environment of the cells only by diffusing through the narrow gap between the slides. Due to the competition between cells, self-created gradients of nutrients and metabolic products are set up resulting in a layer of cells which resembles a living spheroid cross section. Unlike the cells of the spheroid, however, cells in all regions of the sandwich are visible. Therefore, the relative sizes of the regions and their time-dependent growth can be monitored visually without fixation or sectioning. The oxygen and nutrient gradients can be ''turned off'' at any time without disrupting the spatial arrangement of the cells by removing the top slide of the assembly and subsequently turned back on if desired. Removal of the top slide also provides access to all the cells, including those near the necrotic center, of the sandwich. The cells can then be removed for analysis outside the sandwich system. 61 refs., 17 figs.

Hlatky, L.

1985-11-01

39

Reptation-Induced Coalescence of Tunnels and Cavities in Escherichia Coli XylE Transporter Conformers Accounts for Facilitated Diffusion.  

PubMed

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 4-20M), previously identified by crystallography and additionally consistently docks to lower affinity sites in the external and internal vestibules (K i 12-50M). 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 (4.50.4). 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

Cunningham, Philip; Naftalin, Richard J

2014-11-01

40

Diffusion in a generalized thermoelastic solid in an infinite body with a cylindrical cavity  

NASA Astrophysics Data System (ADS)

A dynamic problem of an infinite isotropic cylinder of radius r subjected to boundary conditions of the radial stress, temperature, or concentration of the diffusing substance is studied by using the equations of state of a elastothermodiffusive solid with one relaxation time and the Laplace transform technique. The distributions of the displacement, temperature, and concentration are displayed graphically and analytically.

Sharma, J. N.; Kumari, N.; Sharma, K. K.

2013-09-01

41

Ice crystal growth in a dynamic thermal diffusion chamber  

NASA Technical Reports Server (NTRS)

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.

Keller, V. W.

1980-01-01

42

A generalized diffusion model for growth of nanoparticles synthesized by colloidal methods.  

PubMed

A nanoparticle growth model is developed to predict and guide the syntheses of monodisperse colloidal nanoparticles in the liquid phase. The model, without any a priori assumptions, is based on the Fick's law of diffusion, conservation of mass and the Gibbs-Thomson equation for crystal growth. In the limiting case, this model reduces to the same expression as the currently accepted model that requires the assumption of a diffusion layer around each nanoparticle. The present growth model bridges the two limiting cases of the previous model i.e. complete diffusion controlled and adsorption controlled growth of nanoparticles. Specifically, the results show that a monodispersion of nanoparticles can be obtained both with fast monomer diffusion and with surface reaction under conditions of small diffusivity to surface reaction constant ratio that results is growth 'focusing'. This comprehensive description of nanoparticle growth provides new insights and establishes the required conditions for fabricating monodisperse nanoparticles critical for a wide range of applications. PMID:24491334

Wen, Tianlong; Brush, Lucien N; Krishnan, Kannan M

2014-04-01

43

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

USGS Publications Warehouse

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.

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

1999-01-01

44

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth  

Microsoft Academic Search

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

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

2004-01-01

45

Four-fold channels are involved in iron diffusion into the inner cavity of plant ferritin.  

PubMed

From an evolutionary point of view, plant and animal ferritins arose from a common ancestor, but plant ferritin exhibits different features as compared with the animal analogue. One major difference is that the 4-fold channels naturally occurring in plant ferritin are hydrophilic, whereas the 4-fold channels in animal ferritin are hydrophobic. Prior to this study, however, the function of the 4-fold channels in oxidative deposition of iron in phytoferritin remained unknown. To elucidate the role of the 4-fold channels in iron oxidative deposition in ferritin, three mutants of recombinant soybean seed H-2 ferritin (rH-2) were prepared by site-directed mutagenesis, which contained H193A/H197A, a 4-fold channel mutant, E165I/E167A/E171A, a 3-fold channel mutant, and E165I/E167A/E171A/H193A/H197A, where both 3- and 4-channels were mutated. Stopped-flow, electrode oximetry, and transmission electron microscopy (TEM) results showed that H193A/H197A and E165I/E167A/E171A exhibited a similar catalyzing activity of iron oxidation with each other, but a pronounced low activity compared to rH-2, demonstrating that both the 4-fold and 3-fold hydrophilic channels are necessary for iron diffusion in ferritin, followed by oxidation. Indeed, among all tested ferritin, the catalyzing activity of E165I/E167A/E171A/H193A/H197A was weakest because its 3- and 4- fold channels were blocked. These findings advance our understanding of the function of 4-fold channels of plant ferritin and the relationship of the structure and function of ferritin. PMID:24678690

Lv, Chenyan; Zhang, Shengli; Zang, Jiachen; Zhao, Guanghua; Xu, Chuanshan

2014-04-15

46

Assessment of the possibility of oriented growth of sulfides and carbides during reaction diffusion  

Microsoft Academic Search

1.The above calculation of the temperature range of oriented growth of carbides and Sulfides on the basis of the thermodynamics and kinetics of chemepitaxial nucleation and growth of a new phase during reaction diffusion makes it possible, with a certain accuracy, to determine the possibility of epitaxial growth of carbides and Sulfides on crystalline substrates.2.When comparatively large mismatches exist between

P. I. Ignatenko; K. Anderko; O. Kubaschewski; P. I. Baranskii; V. P. Klochkov; I. V. Potykevich; Naukova Dumka; W. Missol

1983-01-01

47

Predicting material parameters for intrinsic point defect diffusion in Silicon Crystal Growth  

E-print Network

Predicting material parameters for intrinsic point defect diffusion in Silicon Crystal Growth Bonn, Wegelerstr. 6, 53115 Bonn, Germany, jager@iam.uni-bonn.de 3 Crystal Growth group, research center growth and subsequent annealing of the crystal. In order to qualitatively describe the formation

Bebendorf, Mario

48

Economic environment, technology diffusion, and growth of regional total factor productivity in China  

Microsoft Academic Search

This paper examines the effects of the regional economic environment and technology diffusion on China's regional total factor productivity (TFP) growth. We build a model of TFP growth in which Chinese regions achieve growth in TFP by making use of technology spillovers from the world technology frontier. We hypothesize that given the world frontier level of TFP, China's regional TFP

Yanqing Jiang

2011-01-01

49

Anomalous Diffusion and Growth due to Long-Range Correlations.  

NASA Astrophysics Data System (ADS)

I consider two classes of problems which exhibit the influence of long-range correlations on the behavior of statistical systems. In these cases, the introduction of long-range correlations can be drastic, resulting either in the formation of a steady state, or in a change of the characteristic exponents that describe the dynamic and static properties of the system. First, I examine the two-dimensional motion of a particle in a unidirectional velocity field in which V_{x}(y) is a function of y only. The particle follows the direction of the velocity field in the x-direction and it diffuses randomly in the y-direction. I show that the correlations induced by the environment influence considerably the motion of the particle. The probability distribution deviates from a Gaussian behavior and the mean squared displacement grows with time as t ^{3/2}. In the second class of problems, I examine how correlations alter the shape of an interface grown by deposition of particles. The growth of independent columns (no correlations) produces a surface the width of which increases with the square root of time. The introduction of correlations, in this case interactions between the neighboring columns, results in the formation of a steady state. The roughness of the steady state depends on the detailed form of the correlations. For a restricted solid on solid model in (1 + 1) dimensions, I use exact enumeration techniques to show that the width of the interface scales with the square root of the length of the system in the steady state. I also examine the effects of surface rearrangement on morphology. For a process in which a newly-added particle can move laterally by up to one lattice spacing to maximize the number of saturated bonds, we show that a steady state is achieved. The introduction of a destabilizing factor, in our case antigravity, results in a formation of deep and abrupt valleys. The surface does not stabilize and its width grows linearly with time. Such formations do not appear to be described by a continuous Langevin equation.

Provata, Astero G.

50

An improved oxygen diffusion model to explain the effect of low-temperature baking on high field losses in niobium superconducting cavities  

SciTech Connect

Radio-frequency (RF) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve RF field values approaching the theoretical limit for niobium is represented by ''anomalous'' losses which degrade the quality factor of the cavities starting at peak surface magnetic fields of about 100 mT, in absence of field emission. These high field losses are often referred to as ''Q-drop''. It has been observed that the Q-drop is drastically reduced by baking the cavities at 120 C for about 48 h under ultrahigh vacuum. An improved oxygen diffusion model for the niobium-oxide system is proposed to explain the benefit of the low-temperature baking on the Q-drop in niobium superconducting rf cavities. The model shows that baking at 120 C for 48 h allows oxygen to diffuse away from the surface, and therefore increasing the lower critical field towards the value for pure niobium.

Gianluigi Ciovati

2006-07-01

51

On the suppression of the diffusion and the quantum nature of a cavity mode. Optical bistability: forces and friction in driven cavities  

Microsoft Academic Search

A new analytical method is presented here, offering a physical view of driven cavities where the external field cannot be neglected. We introduce a new dimensionless complex parameter, intrinsically linked to the cooperativity parameter of optical bistability, and analogous to the scaled Rabbi frequency for driven systems where the field is classical. Classes of steady states are iteratively constructed and

Karim Murr

2003-01-01

52

Two Parametric Models of Soot Growth Rates in Laminar Ethylene Diffusion Flames  

Microsoft Academic Search

This paper investigates which parameters can be used to model local soot mass growth rates in laminar diffusion flames. Measurements of soot concentrations and number densities are made in a range of ethylene diffusion flames. The data are combined with modelled flame field velocities and mixture fraction to extract local soot formation rates which are evaluated and presented in two

D. R. HONNERY; M. TAPPE; J. H. KENT

1992-01-01

53

Analysis of low-temperature intermetallic growth in copper-tin diffusion couples  

Microsoft Academic Search

A multiphase diffusion model was constructed and used to analyze the growth of the ?- and ?-phase intermetallic layers at a plane Cu-Sn interface in a semi-infinite diffusion couple. Experimental measurements\\u000a of intermetallic layer growth were used to compute the interdiffusivities in the? and? phases and the positions of the interfaces as a function of time. The results suggest that

Z. Mei; A. J. Sunwoo; J. W. Morris

1992-01-01

54

The significance of epidermal growth factor receptor and matrix metalloproteinase-3 in squamous cell carcinoma of the oral cavity  

Microsoft Academic Search

Surgical specimens from 65 patients with squamous cell carcinoma (SCC) of the oral cavity were examined immunohistochemically. The clinicopathological significance of the expression of epidermal growth factor receptor (EGFR) and matrix metalloproteinase-3 (MMP-3) was assessed. Among the 65 tumours, 20 (30.8%) and 37 (56.9%) tested positively for EGFR and MMP-3, respectively. A positive correlation between the expression of EGFR and

J. Kusukawa; H. Harada; I. Shima; Y. Sasaguri; T. Kameyama; M. Morimatsu

1996-01-01

55

Soft bounds on diffusion produce skewed distributions and Gompertz growth  

NASA Astrophysics Data System (ADS)

Constraints can affect dramatically the behavior of diffusion processes. Recently, we analyzed a natural and a technological system and reported that they perform diffusion-like discrete steps displaying a peculiar constraint, whereby the increments of the diffusing variable are subject to configuration-dependent bounds. This work explores theoretically some of the revealing landmarks of such phenomenology, termed "soft bound." At long times, the system reaches a steady state irreversibly (i.e., violating detailed balance), characterized by a skewed "shoulder" in the density distribution, and by a net local probability flux, which has entropic origin. The largest point in the support of the distribution follows a saturating dynamics, expressed by the Gompertz law, in line with empirical observations. Finally, we propose a generic allometric scaling for the origin of soft bounds. These findings shed light on the impact on a system of such "scaling" constraint and on its possible generating mechanisms.

Mandr, Salvatore; Lagomarsino, Marco Cosentino; Gherardi, Marco

2014-09-01

56

Soft bounds on diffusion produce skewed distributions and Gompertz growth  

E-print Network

Constraints can affect dramatically the behavior of diffusion processes. Recently, we analyzed a natural and a technological system and reported that they perform diffusion-like discrete steps displaying a peculiar constraint, whereby the increments of the diffusing variable are subject to configuration-dependent bounds. This work explores theoretically some of the revealing landmarks of such phenomenology, termed "soft bound". At long times, the system reaches a steady state irreversibly (i.e., violating detailed balance), characterized by a skewed "shoulder" in the density distribution, and by a net local probability flux, which has entropic origin. The largest point in the support of the distribution follows a saturating dynamics, expressed by the Gompertz law, in line with empirical observations. Finally, we propose a generic allometric scaling for the origin of soft bounds. These findings shed light on the impact on a system of such "scaling" constraint and on its possible generating mechanisms.

Mandr, Salvatore; Gherardi, Marco

2014-01-01

57

Nonlinear RF and space-charge induced emittance growth in a thermionic injector accelerating cavity  

Microsoft Academic Search

The performance of a high-power free-electron laser depends crucially on the attainment of low beam emittances and short pulse lengths from the injector. One potential injector design involves generating a beam from an rf-gated thermionic cathode that is located within a 700 MHz accelerating cavity. The proposed RF cavity design is modeled using the field-solver Poisson Superfish. Particle energies in

C. Mitchell; P. Sprangle; J. Penano; S. Gold; D. Gordon; A. Ting; B. Hafizi

2010-01-01

58

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

E-print Network

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

Hillen, Thomas

59

Image Guided Personalization of Reaction-Diffusion Type Tumor Growth Models Using Modified Anisotropic Eikonal Equations  

Microsoft Academic Search

Reaction-diffusion based tumor growth models have been widely used in the literature for modeling the growth of brain gliomas. Lately, recent models have started integrating medical images in their formulation. Including different tis sue types, geometry of the brain and the directions of white matter fiber tracts improved the spatial accuracy of reaction-diffusio n models. The adaptation of the general

Ender Konukoglu; Olivier Clatz; Bjoern H. Menze; Marc-Andre Weber; Bram Stieltjes; Emmanuel Mandonnet; Herve Delingette; Nicholas Ayache

2010-01-01

60

Competitive growth of Ta nanopillars during glancing angle deposition: Effect of surface diffusion  

E-print Network

Competitive growth of Ta nanopillars during glancing angle deposition: Effect of surface diffusion Periodic arrays of Ta nanopillars were grown onto patterned substrates by glancing angle sputter deposition at growth temperatures Ts ranging from 200 to 900 °C. The Si substrates were patterned using a colloidal

Gall, Daniel

61

Influence of stochastic domain growth on pattern nucleation for diffusive systems with internal noise  

NASA Astrophysics Data System (ADS)

Numerous mathematical models exploring the emergence of complexity within developmental biology incorporate diffusion as the dominant mechanism of transport. However, self-organizing paradigms can exhibit the biologically undesirable property of extensive sensitivity, as illustrated by the behavior of the French-flag model in response to intrinsic noise and Turings model when subjected to fluctuations in initial conditions. Domain growth is known to be a stabilizing factor for the latter, though the interaction of intrinsic noise and domain growth is underexplored, even in the simplest of biophysical settings. Previously, we developed analytical Fourier methods and a description of domain growth that allowed us to characterize the effects of deterministic domain growth on stochastically diffusing systems. In this paper we extend our analysis to encompass stochastically growing domains. This form of growth can be used only to link the meso- and macroscopic domains as the box-splitting form of growth on the microscopic scale has an ill-defined thermodynamic limit. The extension is achieved by allowing the simulated particles to undergo random walks on a discretized domain, while stochastically controlling the length of each discretized compartment. Due to the dependence of diffusion on the domain discretization, we find that the description of diffusion cannot be uniquely derived. We apply these analytical methods to two justified descriptions, where it is shown that, under certain conditions, diffusion is able to support a consistent inhomogeneous state that is far removed from the deterministic equilibrium, without additional kinetics. Finally, a logistically growing domain is considered. Not only does this show that we can deal with nonmonotonic descriptions of stochastic growth, but it is also seen that diffusion on a stationary domain produces different effects to diffusion on a domain that is stationary on average.

Woolley, Thomas E.; Baker, Ruth E.; Gaffney, Eamonn A.; Maini, Philip K.

2011-10-01

62

Influence of stochastic domain growth on pattern nucleation for diffusive systems with internal noise.  

PubMed

Numerous mathematical models exploring the emergence of complexity within developmental biology incorporate diffusion as the dominant mechanism of transport. However, self-organizing paradigms can exhibit the biologically undesirable property of extensive sensitivity, as illustrated by the behavior of the French-flag model in response to intrinsic noise and Turing's model when subjected to fluctuations in initial conditions. Domain growth is known to be a stabilizing factor for the latter, though the interaction of intrinsic noise and domain growth is underexplored, even in the simplest of biophysical settings. Previously, we developed analytical Fourier methods and a description of domain growth that allowed us to characterize the effects of deterministic domain growth on stochastically diffusing systems. In this paper we extend our analysis to encompass stochastically growing domains. This form of growth can be used only to link the meso- and macroscopic domains as the "box-splitting" form of growth on the microscopic scale has an ill-defined thermodynamic limit. The extension is achieved by allowing the simulated particles to undergo random walks on a discretized domain, while stochastically controlling the length of each discretized compartment. Due to the dependence of diffusion on the domain discretization, we find that the description of diffusion cannot be uniquely derived. We apply these analytical methods to two justified descriptions, where it is shown that, under certain conditions, diffusion is able to support a consistent inhomogeneous state that is far removed from the deterministic equilibrium, without additional kinetics. Finally, a logistically growing domain is considered. Not only does this show that we can deal with nonmonotonic descriptions of stochastic growth, but it is also seen that diffusion on a stationary domain produces different effects to diffusion on a domain that is stationary "on average." PMID:22181173

Woolley, Thomas E; Baker, Ruth E; Gaffney, Eamonn A; Maini, Philip K

2011-10-01

63

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

64

Exponential growth rates in a typed branching diffusion  

Microsoft Academic Search

We study the high temperature phase of a family of typed branching diffusions initially studied in [Astrisque 236 (1996) 133154] and [Lecture Notes in Math. 1729 (2000) 239256 Springer, Berlin]. The primary aim is to establish some almost-sure limit results for the long-term behavior of this particle system, namely the speed at which the population of particles colonizes both space

J. W. Harris; S. C. Harris

2007-01-01

65

Numerical Simulation of Double Diffusive Mixed Convection in a Lid-Driven Square Cavity Using Velocity-Vorticity Formulation  

Microsoft Academic Search

In this article, convection driven by combined thermal and solutal concentration buoyancy effects in a lid-driven square cavity is examined using velocity-vorticity form of Navier-Stokes equations. The governing equations consist of vorticity transport equation, velocity Poisson equations, energy equation, and concentration equation. Validation results are discussed for convection due to heat and mass transfer in a lid-driven square cavity at

D. Senthil Kumar; K. Murugesan; H. R. Thomas

2008-01-01

66

Reaction-diffusion controlled growth of complex structures  

NASA Astrophysics Data System (ADS)

Understanding how the emergence of complex forms and shapes in biominerals came about is both of fundamental and practical interest. Although biomineralization processes and organization strategies to give higher order architectures have been studied extensively, synthetic approaches to mimic these self-assembled structures are highly complex and have been difficult to emulate, let alone replicate. The emergence of solution patterns has been found in reaction-diffusion systems such as Turing patterns and the BZ reaction. Intrigued by this spontaneous formation of complexity we explored if similar processes can lead to patterns in the solid state. We here identify a reaction-diffusion system in which the shape of the solidified products is a direct readout of the environmental conditions. Based on insights in the underlying mechanism, we developed a toolbox of engineering strategies to deterministically sculpt patterns and shapes, and combine different morphologies to create a landscape of hierarchical multi scale-complex tectonic architectures with unprecedented levels of complexity. These findings may hold profound implications for understanding, mimicking and ultimately expanding upon nature's morphogenesis strategies, allowing the synthesis of advanced highly complex microscale materials and devices.

Noorduin, Willem; Mahadevan, L.; Aizenberg, Joanna

2013-03-01

67

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

SciTech Connect

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

Gerasimov, A.

1990-12-06

68

An evaluation of two diffusion culture techniques for estimating phytoplankton growth rates In situ  

Microsoft Academic Search

In comparative tests, acrylic diffusion chambers (voltume=42 ml) with polycarbonate filter membranes (1 m pore diameter) consistently supported higher cell yields and faster growth rates of summer phytoplankton populations and species from Narragansett Bay than did dialysis bags (volume=50 ml, 0.240.48 nm pore diameter) or bottle cultures (with or without added nutrients). Stirring of diffusion chambers or dialysis bags had

M. J. Furnas

1982-01-01

69

Elevated Vascular Endothelial Growth Factor (VEGF) levels in the blood serum of dogs with malignant neoplasms of the oral cavity.  

PubMed

Angiogenesis plays an essential role in the development of a neoplastic tumour by conditioning both its growth and the formation of metastases. The induction of blood vessel growth occurs under the influence of proangiogenic factors, among which Vascular Endothelial Growth Factor (VEGF) seems to be the most important. The aim of this research was to study the level of VEGF measured by ELISA in the serum of dogs with neoplasms of the oral cavity. The study material comprised samples of neoplastic tissue from 17 operated dogs and the serum of the examined animals as well as of dogs from the control group. The tissue samples were taken from dogs of different breeds, aged 6-14 years. The tumour type was determined in accordance with the applicable WHO classification. Blood samples taken from sick dogs and from animals of the control group were centrifuged, and immunoenzymatic labelling of VEGF was performed in the obtained serum using ELISA and R&D system reagents (Quantikine Canine VEGF). All stages of VEGF labelling were performed according to the recommendation of the test manufacturer. The median of VEGF in the serum of the dogs with neoplasms of the oral cavity was 40.64 pg/mL. The lowest value of 14.26 pg/mL was observed in the case of fibrosarcoma, and the highest value of 99.19 pg/mL in the case of squamous cell carcinoma. The VEGF median in the control group amounted to 11.14 pg/mL whereas the VEGF value in the groups of animals diagnosed with benign tumours ranged between 2.30 and 19.74 pg/mL. Elevated VEGF in the blood serum, in comparison with the benign tumour group and the control group, was observed in all examined neoplasms of the oral cavity. It was suggested that overexpression of VEGF can have a prognostic value and is useful in the early detection of neoplasms. PMID:24659713

Sobczy?ska-Rak, Aleksandra; Polkowska, Izabela; Silmanowicz, Piotr

2014-09-01

70

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

SciTech Connect

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 m. 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.

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

2012-09-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

72

Diffusion  

NSDL National Science Digital Library

Diffusion is the net movement of particles from areas of high concentration (number of particles per unit area) to low concentration. In this activity, students use a molecular dynamics model to view the behavior of diffusion in gases and liquids.

Consortium, The C.

2011-12-11

73

An Investigation into Zinc Diffusion and Tin Whisker Growth for Electroplated Tin Deposits on Brass  

NASA Astrophysics Data System (ADS)

It is widely documented that whisker growth is more rapid for tin deposits on brass compared with deposits produced on other substrate materials, such as copper. As a result, studies investigating the effect of process variables on tin whisker formation are often conducted on brass substrates to take advantage of the increased whisker growth rates. Although it has been understood since the 1960s that the increased whisker growth results from zinc diffusion, to date there has not been any detailed analysis of the zinc/zinc oxide distribution at the surface of the tin deposit. Using a commercial bright tin electroplating bath, the formation of zinc oxide at the surface of tin deposits on brass has been investigated. Analyses show that zinc oxide is present on the surface of the deposit within 1 day of electroplating. During storage at room temperature, a network of zinc oxide is formed at the surface grain boundaries, the extent of which increases with time. The critical role that zinc surface diffusion plays in whisker growth for tin deposits on brass has been demonstrated by electrochemical oxidation of the tin shortly after electroplating. This develops a tin oxide film that is thicker than the native air-formed oxide and subsequently serves as a diffusion barrier to zinc surface diffusion, thereby mitigating whisker growth.

Ashworth, Mark A.; Wilcox, Geoffrey D.; Higginson, Rebecca L.; Heath, Richard J.; Liu, Changqing

2014-04-01

74

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

NASA Technical Reports Server (NTRS)

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.

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

75

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

NASA Technical Reports Server (NTRS)

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.

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

76

Effects of grain growth on grain-boundary diffusion creep by molecular-dynamics simulation  

Microsoft Academic Search

Molecular-dynamics simulations are used to elucidate the effects of grain growth on grain-boundary diffusion creep and grain-boundary sliding during high-temperature deformation of a nanocrystalline Pd model microstructure. The initial microstructure consists of a 25-grain polycrystal with an average grain size of about 15 nm and a columnar grain shape. Prior to the onset of significant grain growth, the deformation proceeds

A. J. Haslam; V. Yamakov; D. Moldovan; D. Wolf; S. R. Phillpot; H. Gleiter; Forschungszentrum Karlsruhe

2004-01-01

77

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

NASA Astrophysics Data System (ADS)

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) 10-15 (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.

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

2014-10-01

78

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

SciTech Connect

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.

Wen, Z. X.; Lu, J.; Bai, B. F. [State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University (China)

2010-03-01

79

A study on technology acquisition and diffusion in Satellite Platform clusters at the growth stage  

Microsoft Academic Search

The mechanisms of technology acquisition and diffusion of different types of industry clusters at different stages vary widely, and Satellite Platform clusters at the growth stage become the focus of attention with the development of local embeddedness of outside large companies. Based on the case study of auto parts cluster in Liujiang County, Guangxi Zhuang Autonomous Region, this article argues

Long Kaiyuan; Bi Liangliang

2010-01-01

80

On the linearized gradient approximation for diffusion-limited growth of a spherical precipitate  

Microsoft Academic Search

An error in a published [J. Appl. Phys. 41, 4404 (1970)] linearized-gradient analysis of the diffusion-limited growth of a spherical precipitate is corrected. Comparison of the present and previous analyses as a function of supersaturation shows that the numerical effects of the error are small enough to warrant use of the incorrect but simpler analysis unless a high level of

M. Enomoto; H. I. Aaronson

1980-01-01

81

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

PubMed Central

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

2013-01-01

82

Metalorganic vapor phase epitaxial growth of red and infrared vertical-cavity surface-emitting laser diodes  

NASA Astrophysics Data System (ADS)

Metalorganic vapor phase epitaxy (MOVPE) is used for the growth of vertical-cavity surface-emitting laser (VCSEL) diodes. MOVPE exhibits a number of important advantages over the more commonly-used molecular-beam epitaxial (MBE) techniques, including ease of continuous compositional grading and carbon doping for low-resistance p-type distributed Bragg reflectors (DBRs), higher growth rates for rapid throughput and greater versatility in choice of materials and dopants. Planar gain-guided red VCSELs based on AlGaInP/AlGaAs heterostructures lase continuous-wave at room temperature, with voltage thresholds between 2.5 and 3 V and maximum power outputs of over 0.3 mW. Top-emitting infra-red (IR) VCSELs exhibit the highest power-conversion (wall-plug) efficiencies (21%), lowest threshold voltage (1.47 V), and highest single mode power (4.4 mW from an 8 ?m device) yet reported. These results establish MOVPE as a preferred growth technique for this important new family of photonic devices.

Schneider, R. P.; Lott, J. A.; Lear, K. L.; Choquette, K. D.; Crawford, M. H.; Kilcoyne, S. P.; Figiel, J. J.

1994-12-01

83

A pore-cavity-pore device to trap and investigate single nanoparticles and DNA molecules in a femtoliter compartment: confined diffusion and narrow escape.  

PubMed

Spatial confinement from the nano- to the microscale is ubiquitous in nature. Striving to understand the behavior of nanoscale objects in confined domains we present a nanofluidic silicon device which consists of two stacked nanopores forming the in/outlets to a pyramidal cavity of micrometer dimensions (10 fL volume). Being electrically addressable, charged objects can be actively loaded into, trapped inside, and unloaded from the "pore-cavity-pore" (PCP) device. When operated passively, confined Brownian motion and the entropy barriers of the nanopores govern the behavior of nano-objects within the PCP device. We present measurements with single fluorescent nanoparticles as well as particle-ensembles and analyze their trajectories and residence times. Experimental data are compared to random walk simulations and analytical theories on confined diffusion and the Brownian escape of nano-objects across entropy barriers. Single particle data corroborate analytical solutions of the narrow escape problem, but ensemble measurements indicate crowding effects even at low particle concentrations. The utilization of the device to trap biomolecules is demonstrated for single ?-DNA molecules. PMID:21388205

Pedone, Daniel; Langecker, Martin; Abstreiter, Gerhard; Rant, Ulrich

2011-04-13

84

Double-diffusive convection in a cubical lid-driven cavity with opposing temperature and concentration gradients  

NASA Astrophysics Data System (ADS)

A numerical study of three-dimensional incompressible viscous flow inside a cubical lid-driven cavity is presented. The flow is governed by two mechanisms: (1) the sliding of the upper surface of the cavity at a constant velocity and (2) the creation of an external gradient for temperature and solutal fields. Extensive numerical results of the three-dimensional flow field governed by the Navier-Stokes equations are obtained over a wide range of physical parameters, namely Reynolds number, Grashof number and the ratio of buoyancy forces. The preceding numerical results obtained have a good agreement with the available numerical results and the experimental observations. The deviation of the flow characteristics from its two-dimensional form is emphasized. The changes in main characteristics of the flow due to variation of Reynolds number are elaborated. The effective difference between the two-dimensional and three-dimensional results for average Nusselt number and Sherwood number at high Reynolds numbers along the heated wall is analyzed. It has been observed that the substantial transverse velocity that occurs at a higher range of Reynolds number disturbs the two-dimensional nature of the flow.

Nayak, A. K.; Bhattacharyya, S.

2012-12-01

85

The role of carbon surface diffusion on the growth of epitaxial graphene on SiC.  

SciTech Connect

Growth of high quality graphene films on SiC is regarded as one of the more viable pathways toward graphene-based electronics. Graphitic films form on SiC at elevated temperature because of preferential sublimation of Si. Little is known, however, about the atomistic processes of interrelated SiC decomposition and graphene growth. We have observed the formation of graphene on SiC by Si sublimation in an Ar atmosphere using low energy electron microscopy, scanning tunneling microcopy and atomic force microscopy. This work reveals that the growth mechanism depends strongly on the initial surface morphology, and that carbon diffusion governs the spatial relationship between SiC decomposition and graphene growth. Isolated bilayer SiC steps generate narrow ribbons of graphene, whereas triple bilayer steps allow large graphene sheets to grow by step flow. We demonstrate how graphene quality can be improved by controlling the initial surface morphology specifically by avoiding the instabilities inherent in diffusion-limited growth.

Thurmer, Konrad (Sandia National Laboratories, Livermore, CA); Ohta, Taisuke; Nie, Shu (Sandia National Laboratories, Livermore, CA); Bartelt, Norman Charles (Sandia National Laboratories, Livermore, CA); Kellogg, Gary Lee

2010-03-01

86

Effects of grain growth on grain-boundary diffusion creep by molecular-dynamics simulation.  

SciTech Connect

Molecular-dynamics simulations are used to elucidate the effects of grain growth on grain-boundary diffusion creep and grain-boundary sliding during high-temperature deformation of a nanocrystalline Pd model microstructure. The initial microstructure consists of a 25-grain polycrystal with an average grain size of about 15 nm and a columnar grain shape. Prior to the onset of significant grain growth, the deformation proceeds via the mechanism of Coble creep accompanied by grain-boundary sliding. While grain growth is generally known to decrease the creep rate due to the increase of the average grain size, the results obtained in this study reveal an enhanced creep rate at the onset of the grain growth, when rapid grain-boundary migration occurs. The enhanced creep rate is shown to arise from topological changes during the initial growth phases, which enhance both the stress-induced grain-boundary diffusive fluxes and grain-boundary sliding. Dislocations generated as a result of grain-rotation-induced grain coalescence and grain-boundary decomposition in the vicinity of certain triple junctions also contribute to the deformation.

Haslam, A. J.; Yamakov, V.; Moldovan, D.; Wolf, D.; Phillpot, S. R.; Gleiter, H.; Materials Science Division; Forschungszentrum Karlsruhe

2004-04-01

87

Effect of Lupinus seed diffusates on Bradyrhizobium sp. growth and nodulation of lupine  

Microsoft Academic Search

Seeds of three species of lupine (Lupinus termis, L. triticale andL. albus) were tested to determine if the seed contains diffusable substances toxic to bradyrhizobia.L. albus seeds were less toxic to bradyrhizobia, followed byL. triticale. Six strains ofBradyrhizobium were evaluated for their resistance to the toxic substances in lupine seeds. Zones of growth inhibition were determined on\\u000a yeast-mannitol-agar medium surrounding

M. H. Abd-Alla

1998-01-01

88

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth  

E-print Network

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

Eom, Chang Beom

89

A skeletal muscle model of extreme hypertrophic growth reveals the influence of diffusion on cellular design  

PubMed Central

Muscle fibers that power swimming in the blue crab Callinectes sapidus are <80 ?m in diameter in juveniles but grow hypertrophically, exceeding 600 ?m in adults. Therefore, intracellular diffusion distances become progressively greater as the animals grow and, in adults, vastly exceed those in most cells. This developmental trajectory makes C. sapidus an excellent model for characterization of the influence of diffusion on fiber structure. The anaerobic light fibers, which power burst swimming, undergo a prominent shift in organelle distribution with growth. Mitochondria, which require O2 and rely on the transport of small, rapidly diffusing metabolites, are evenly distributed throughout the small fibers of juveniles, but in the large fibers of adults they are located almost exclusively at the fiber periphery where O2 concentrations are high. Nuclei, which do not require O2, but rely on the transport of large, slow-moving macromolecules, have the inverse pattern: they are distributed peripherally in small fibers but are evenly distributed across the large fibers, thereby reducing diffusion path lengths for large macromolecules. The aerobic dark fibers, which power endurance swimming, have evolved an intricate network of cytoplasmically isolated, highly perfused subdivisions that create the short diffusion distances needed to meet the high aerobic ATP turnover demands of sustained contraction. However, fiber innervation patterns are the same in the dark and light fibers. Thus the dark fibers appear to have disparate functional units for metabolism (fiber subdivision) and contraction (entire fiber). Reaction-diffusion mathematical models demonstrate that diffusion would greatly constrain the rate of metabolic processes without these developmental changes in fiber structure. PMID:19321701

Hardy, Kristin M.; Dillaman, Richard M.; Locke, Bruce R.; Kinsey, Stephen T.

2009-01-01

90

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

91

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

SciTech Connect

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.

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

2012-09-20

92

Diffusion  

NSDL National Science Digital Library

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

Christopher Thomas (None;)

2006-11-09

93

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

PubMed Central

Matrix population models are widely used to study population dynamics but have been criticized because their outputs are sensitive to the dimension of the matrix (or, equivalently, to the class width). This sensitivity is concerning for the population growth rate () because this is an intrinsic characteristic of the population that should not depend on the model specification. It has been suggested that the sensitivity of to matrix dimension was linked to the existence of fast pathways (i.e. the fraction of individuals that systematically move up a class), whose proportion increases when class width increases. We showed that for matrix population models with growth transition only from class to class , was independent of the class width when the mortality and the recruitment rates were constant, irrespective of the growth rate. We also showed that if there were indeed fast pathways, there were also in about the same proportion slow pathways (i.e. the fraction of individuals that systematically remained in the same class), and that they jointly act as a diffusion process (where diffusion here is the movement in size of an individual whose size increments are random according to a normal distribution with mean zero). For 53 tree species from a tropical rain forest in the Central African Republic, the diffusion resulting from common matrix dimensions was much stronger than would be realistic. Yet, the sensitivity of to matrix dimension for a class width in the range 110 cm was small, much smaller than the sampling uncertainty on the value of . Moreover, could either increase or decrease when class width increased depending on the species. Overall, even if the class width should be kept small enough to limit diffusion, it had little impact on the estimate of for tree species. PMID:24905941

Picard, Nicolas; Liang, Jingjing

2014-01-01

94

Diffusion  

NSDL National Science Digital Library

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

95

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

SciTech Connect

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

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

2009-01-20

96

Modeling the Growth of Hyperthermophiles in Deep-sea Hydrothermal Diffuse Fluids and Sulfide Deposits  

NASA Astrophysics Data System (ADS)

In 2008 and 2009, 534 hydrothermal fluid samples and 5 actively-venting black smoker chimneys were collected using Alvin for correlative microbiological and chemical analyses as part of the Endeavour Segment and Axial Volcano Geochemistry and Ecology Research (EAGER) program. Hyperthermophilic, autotrophic Fe(III) oxide reducers, methanogens, and sulfur-reducing heterotrophs were enriched for at 85 and 95C using most-probable-number estimates from 28 diffuse fluid and 8 chimney samples. Heterotrophs were the most abundant of the three groups in both diffuse fluids and black-smoker chimneys. Iron reducers were more abundant than methanogens, and more abundant in sulfide-hosted vents than in basalt-hosted vents. Fluid chemistry suggests that there is net biogenic methanogenesis at the Marker 113/62 diffuse vent at Axial Volcano but nowhere else sampled. The growth of hyperthermophilic methanogens and heterotrophs was modeled in the lab using pure cultures. Methanocaldococcus jannaschii grew at 82C in a 2-liter reactor with continuous gas flow at H2 concentrations between 20 and 225 M with a H2 km of 100 M. Correlating H2 end-member mixing curves from vent fluids and seawater with our laboratory modeling study suggests that H2 concentrations are limiting for Methanocaldococcus growth at most Mothra, Main Field, and High Rise vent sites at Endeavour but sufficient to support growth at some Axial Volcano vents. Therefore, hyperthermophilic methanogens may depend on H2 syntrophy at low H2 sites. Twenty-one pure hyperthermophilic heterotroph strains each grew on ?-1,4 and ?-1,4 linked sugars and polypeptides with concomitant H2 production. The H2 production rate (cell-1 doubling-1) for Pyrococcus furiosus at 95C without sulfur was 29 fmol, 36 fmol, and 53 fmol for growth on ?-1,4 sugars, ?-1,4 sugars, and peptides, respectively. The CH4 production rate for M. jannaschii was 390 fmol cell-1 doubling-1; therefore, we estimate that it would take approximately 40 heterotroph cells to provide all of the H2 necessary to support the growth of a single methanogen. In contrast to methanogens, autotrophic Fe(III) oxide reducers consume far less H2 during growth and reach cell concentrations similar to methanogens in pure culture. Thermodynamic predictions suggest that they would grow at H2 concentrations lower than those needed by methanogens.

Ver Eecke, H. C.; Oslowski, D. M.; Butterfield, D. A.; Olson, E. J.; Lilley, M. D.; Holden, J. F.

2009-12-01

97

Microbial Growth and Coexistence on Diffusion-limited Unsaturated Rough Surfaces  

NASA Astrophysics Data System (ADS)

Microbial activity in unsaturated soils plays an important role in biochemical nutrient cycling, bioremediation, and dispersal of pathogenic microorganisms. Quantitative description of microbial activity in unsaturated soils is hindered by complexity of pore space and hydration dynamics. Microbes in unsaturated soils live in an environment dominated by presence of numerous solid- and gas-liquid interfaces, where nutrient distribution and flux pathways are dynamically shaped by liquid configuration. We propose a model for considering effects of nutrient diffusive fluxes under various hydrations and pore space conditions on microbial growth and coexistence of two competing bacterial species. Simulation results show that hydration limitation to nutrient diffusive fluxes enhance microbial coexistence and are in good agreement with available experimental results. Effective nutrient diffusion coefficients on rough surfaces is significantly affected by liquid configuration and by connectivity (expressed as percolation probability) of the surface roughness network. The aqueous network is dynamically controlled by matric potential where effective diffusion coefficient varied from 0.46 mm2/hr to 0 and percolation probability varied from 0.76 to 0.21 when matric potential varies from -0.01 to -5 kPa, respectively. For matric potential values of -2.0 kPa and lower, two competing microbial species coexisted indefinitely supported by limited nutrient flux and within fragmented liquid clusters with percolation probability 0.37. Coexistence was limited to 90 hrs at -1.2 kPa with increasing percolation probability to 0.52 (effective diffusion coefficient of 0.19 mm2/hr). No coexistence was observed at matric potential of -0.01 kPa, the stronger species rapidly expanded and dominated the entire domain. Pore scale and roughness microhydrology may play an important role in the large microbial diversity found in soil.

Wang, G.; Or, D.

2009-04-01

98

Growth of a diffusion flame in the field of a vortex  

NASA Technical Reports Server (NTRS)

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.

Marble, F. E.

1985-01-01

99

Nanoparticle diffusion on desorbing solids: The role of elementary excitations in buffer-layer-assisted growth  

NASA Astrophysics Data System (ADS)

Physical vapor deposition onto rare gas buffer layers leads to the spontaneous formation of clusters. During the thermal desorption of the buffer, these clusters diffuse and aggregate into larger structures, a process known as buffer-layer-assisted growth and desorption assisted coalescence. We studied the effect of buffer thickness and the rate of buffer desorption on the extent of this aggregation for Ag, Au, Cu, Pd, Co, and Ni particles on a solid Xe surface. On the basis of these experiments, results from Monte Carlo simulations and the existing theoretical models for cluster-cluster aggregation, we report for the first time the Arrhenius parameters for nanoparticle slip-diffusion. The effective activation energies range from 0.12 for small Ag clusters (few hundred atoms) to 0.60eV for ramified Ni islands (millions of atoms), and the giant pre-exponential factors were found to differ by many orders of magnitude. Significantly, the pre-exponential factors follow a Meyer-Neldel-type dependence on the corresponding effective activation energy, with a characteristic Meyer-Neldel energy of 6.9meV . This energy is associated with the phononic excitations in solid Xe that are responsible for nanostructure mobility. This dependence should be a characteristic feature of nanoparticle diffusion.

Antonov, V. N.; Palmer, J. S.; Waggoner, P. S.; Bhatti, A. S.; Weaver, J. H.

2004-07-01

100

Competitive growth of Ta nanopillars during glancing angle deposition: Effect of surface diffusion  

SciTech Connect

Periodic arrays of Ta nanopillars were grown onto patterned substrates by glancing angle sputter deposition at growth temperatures T{sub s} ranging from 200 to 900 deg. C. The Si substrates were patterned using a colloidal suspension of 260-nm-diameter silica spheres that was dispersed to form a two-dimensional close-packed monolayer. At low growth temperatures, T{sub s}{<=}500 deg. C, nanopillars exhibit regular hexagonal arrays. However, the arrays randomize with increasing T{sub s} and completely degrade at T{sub s}=900 deg. C. The transition to a less ordered film morphology is attributed to strong interpillar competition caused by the increasing adatom diffusion length with increasing T{sub s}. The competitive growth mode leads to a decrease in the pillar number density (by 48%) and pillar separation (from 65 nm to negligible), an increase in the average pillar width from 200 to 260 nm, the accelerated growth of some pillars at the cost of others which die out (25%), and an increased probability (20%) for the merging of neighboring pillars.

Zhou, C. M.; Gall, D. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2007-03-15

101

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

USGS Publications Warehouse

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.

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

2003-01-01

102

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

NASA Astrophysics Data System (ADS)

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) ?? 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 ?? 0.5 merwinite + 0.5 diopside + MgO, and at the rim-wollastonite interface, it is: 2 wollastonite + MgO ?? 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 1.5510-16 2.1810-17 m2/s, and at 900 C at 2.4610-16 3.4510-17 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

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

2009-04-01

103

Effects of microstructural inhomogeneity on dynamic grain growth during large-strain grain boundary diffusion-assisted plastic deformation  

Microsoft Academic Search

Mesoscale simulations of grain-boundary (GB) diffusion creep in which GB migration-induced static grain growth is suppressed were carried out based on the variational principle of dissipated power. Assuming that the boundaries exhibit no sliding resistance in response to shear stress, the variation of the normal-stress distribution and the diffusive fluxes along the grain boundaries during Coble creep were analysed. The

R. Ding; D. Moldovan; V. Yamakov; D. Wolf; S. R. Phillpot

2005-01-01

104

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

NASA Astrophysics Data System (ADS)

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 towards the generation of only D-loops 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 towards a biased generation of D- or L-loops.

Mnner, Jrg; Bayraktar, Meric

2014-04-01

105

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

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

Bayraktar, Meric; Manner, Jorg

2014-01-01

106

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

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

Bayraktar, Meri; Mnner, Jrg

2014-01-01

107

Diffusion-controlled and diffusionless crystal growth in liquid o-terphenyl near its glass transition temperature  

NASA Astrophysics Data System (ADS)

o-terphenyl is one of the organic liquids in which a fast mode of crystal growth is activated near the glass transition temperature Tg and continues deep in the glassy state. This growth mode, termed glass-crystal (GC), is not limited by molecular diffusion in the bulk liquid, in contrast to the diffusion-controlled growth at higher temperatures. The GC mode has been previously described as abruptly emerging near Tg and having a constant growth rate at a fixed temperature, two features important for testing its various explanations. We report here that the GC mode already exists in the equilibrium liquid of o-terphenyl up to 1.15Tg (Tg=246 K) in the form of loose, fast-growing fibers and that its growth rate is constant at Tg+2 K, but decreases by 30% in 10 h at Tg-13 K, during which time the glass' fictive temperature decreases by 6 K. The slow down of GC growth becomes less noticeable over time so that fast growth is still observable after long annealing. The fiber growth, similar to the fully activated GC growth that yields compact spherulites, is also not limited by bulk diffusion. Crystal growth in the GC mode has a comparable activation energy as liquid desorption but a much faster rate, properties in common with polymorphic conversions. The time dependence of GC growth is not readily explained by the effect of physical aging on the thermodynamic driving force of crystallization, the liquid desorption, the primary structural relaxation, or a secondary relaxation. The secondary dielectric relaxation observed by dielectric spectroscopy in glassy o-terphenyl disappears too quickly for its molecular motions to be responsible for GC growth.

Xi, Hanmi; Sun, Ye; Yu, Lian

2009-03-01

108

Body mass index and blood glucose: correlations with serum insulin, growth hormone, and insulin-like growth factor-1 levels in patients with diffuse idiopathic skeletal hyperostosis (DISH)  

Microsoft Academic Search

Obesity is a frequent co-morbid condition associated with diffuse idiopathic skeletal hyperostosis (DISH). Serum growth hormone (GH), insulin-like growth factor (IGF-1) and insulin are significantly elevated in patients with DISH. In this study, we examined the relationship between body mass index (BMI) and basal serum GH, IGF-1, and insulin concentration in a group of 36 DISH patients. Basal serum insulin

Charles W. Denko; Charles J. Malemud

2006-01-01

109

An improved oxygen diffusion model to explain the effect of low-temperature baking on high field losses in niobium superconducting cavities  

Microsoft Academic Search

Radio-frequency (RF) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve RF field values approaching the theoretical limit for niobium is represented by ''anomalous'' losses which degrade the quality factor of the cavities starting at peak surface magnetic fields of about 100 mT, in absence of

Gianluigi Ciovati

2005-01-01

110

Improved oxygen diffusion model to explain the effect of low-temperature baking on high field losses in niobium superconducting cavities  

Microsoft Academic Search

Radio-frequency (rf) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve rf field values approaching the theoretical limit for niobium is represented by ``anomalous'' losses which degrade the quality factor of the cavities starting at peak surface magnetic fields of about 100 mT, in the absence

Gianluigi Ciovati

2006-01-01

111

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

112

Expression of epidermal growth factor variant III (EGFRvIII) in pediatric diffuse intrinsic pontine gliomas  

PubMed Central

Despite numerous clinical trials over the past 2 decades, the overall survival for children diagnosed with diffuse intrinsic pontine glioma (DIPG) remains 910 months. Radiation therapy is the only treatment with proven effect and novel therapies are needed. Epidermal growth factor receptor variant III (EGFRvIII) is the most common variant of the epidermal growth factor receptor and is expressed in many tumor types but is rarely found in normal tissue. A peptide vaccine targeting EGFRvIII is currently undergoing investigation in phase 3 clinical trials for the treatment of newly diagnosed glioblastoma (GBM), the tumor in which this variant receptor was first discovered. In this study, we evaluated EGFRvIII expression in pediatric DIPG samples using immunohistochemistry with a double affinity purified antibody raised against the EGFRvIII peptide. Staining of pediatric DIPG histological samples revealed expression in 4 of 9 cases and the pattern of staining was consistent with what has been seen in EGFRvIII transfected cells as well as GBMs from adult trials. In addition, analysis of tumor samples collected immediately post mortem and of DIPG cells in culture by RT-PCR, western blot analysis, and flow cytometry confirmed EGFRvIII expression. We were therefore able to detect EGFRvIII expression in 6 of 11 DIPG cases. These data suggest that EGFRvIII warrants investigation as a target for these deadly pediatric tumors. PMID:22382786

Mitra, Siddhartha S.; Monje, Michelle; Henrich, Kristy N.; Bangs, C. Dana; Nitta, Ryan T.

2012-01-01

113

Travelling wave solutions of the reaction-diffusion mathematical model of glioblastoma growth: An Abel equation based approach  

E-print Network

We consider quasi-stationary (travelling wave type) solutions to a nonlinear reaction-diffusion equation with arbitrary, autonomous coefficients, describing the evolution of glioblastomas, aggressive primary brain tumors that are characterized by extensive infiltration into the brain and are highly resistant to treatment. The second order nonlinear equation describing the glioblastoma growth through travelling waves can be reduced to a first order Abel type equation. By using the integrability conditions for the Abel equation several classes of exact travelling wave solutions of the general reaction-diffusion equation that describes glioblastoma growth are obtained, corresponding to different forms of the product of the diffusion and reaction functions. The solutions are obtained by using the Chiellini lemma and the Lemke transformation, respectively, and the corresponding equations represent generalizations of the classical Fisher--Kolmogorov equation. The biological implications of two classes of solutions ...

Harko, Tiberiu

2014-01-01

114

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

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

115

Silicon and oxygen self diffusion in enstatite polycrystals: the Milke et al. (2001) rim growth experiments revisited  

NASA Astrophysics Data System (ADS)

Milke et al. (Contrib Mineral Petrol 142:15-26, 2001) studied the diffusion of Si, Mg and O in synthetic polycrystalline enstatite reaction rims. The reaction rims were grown at 1,000C and 1 GPa at the contacts between forsterite grains with normal isotopic compositions and a quartz matrix extremely enriched in 18O and 29Si. The enstatite reaction rim grew from the original quartz-forsterite interface in both directions producing an inner portion, which replaced forsterite and an outer portion, which replaced quartz. Here we present new support for this statement, as the two portions of the rim are clearly distinguished based on crystal orientation mapping using electron backscatter diffraction (EBSD). Milke et al. (Contrib Mineral Petrol 142:15-26, 2001) used the formalism of LeClaire (J Appl Phys 14:351-356, 1963) to derive the coefficient of silicon grain boundary diffusion from stable isotope profiles across the reaction rims. LeClaire's formalism is designed for grain boundary tracer diffusion into an infinite half space with fixed geometry. A fixed geometry is an undesired limitation in the context of rim growth. We suggest an alternative model, which accounts for simultaneous layer growth and superimposed silicon and oxygen self diffusion. The effective silicon bulk diffusivity obtained from our model is approximately equal within both portions of the enstatite reaction rim: DSi,Eneff=1.0-4.310-16 m2 s-1. The effective oxygen diffusion is relatively slow in the inner portion of the reaction rim, DO,Eneff=0.8-1.410-16 m2 s-1, and comparatively fast, DO,Eneff=5.9-11.610-16 m2 s-1, in its outer portion. Microstructural evidence suggests that transient porosity and small amounts of fluid were concentrated at the quartz-enstatite interface during rim growth. This leads us to suspect that the presence of an aqueous fluid accelerated oxygen diffusion in the outer portion of the reaction rim. In contrast, silica diffusion does not appear to have been affected by the spatial variation in the availability of an aqueous fluid.

Abart, R.; Kunze, K.; Milke, R.; Sperb, R.; Heinrich, W.

116

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)

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. Lgsgaard, 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. Lgsgaard 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.

Besenbacher, Flemming

1997-03-01

117

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)

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 ?V(t)/m=2.6910-1?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/?vi2, where Yt is the target material strength, as follows: ?=1.6910-1?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.

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

2012-11-01

118

Growth morphology of vicinal hillocks on the (101) face of KH{sub 2}PO{sub 4}: Evidence of surface diffusion  

SciTech Connect

The growth morphologies of vicinal hillocks on KH{sub 2}PO{sub 4} (101) surfaces have been investigated using atomic force microscopy. Both 2D and spiral dislocation growth hillocks are observed on the same crystal surface at supersaturations of {approximately}5%. Growth occurs on monomolecular 5 {Angstrom} steps both by step-flow and through layer-by-layer growth. The distribution of islands on the terraces demonstrate that surface diffusion is an important factor during growth. Terraces that are less than the diffusion length do not contain any islands. This, together with the length scale of the inter island spacing and the denuded zones provide an estimate of the diffusion length. In situ experiments at very low supersaturation ({approximately}0.l%) show that growth is a discontinuous process due to step pinning. In addition, in situ images allow for the direct determination of the fundamental growth parameters {alpha}, the step edge energy, and {beta}, the kinetic coefficient.

Land, T.A.; De Yoreo, J.J.; Lee, J.D.; Ferguson, J.R.

1995-01-10

119

Growth and testing of vertical external cavity surface emitting lasers (VECSELs) for intracavity cooling of Yb:YLF  

NASA Astrophysics Data System (ADS)

Optically-pumped vertical external cavity surface emitting lasers (VECSELs) have unique characteristics that make them attractive for use in intracavity optical cooling of rare earth doped crystals. We present the development of high power VECSELs at 1020 nm for cooling ytterbium-doped yttrium lithium fluoride (Yb:YLF). The VECSEL structures use AlAs/GaAs distributed Bragg reflectors and InGaAs/GaAsP resonant periodic gain epitaxially grown by metal-organic vapor phase epitaxy. To achieve the necessary output power, we investigated thinning the substrate to improve the thermal characteristics. We demonstrated a VECSEL structure that was grown inverted, bonded to the heat sink, and the substrate removed by chemical etching. The inverted structure allows us to demonstrate 15 W output with 27% slope efficiency. Wavelength tuning of 30 nm around 1020 nm was achieved by inserting a birefringent quartz window into the cavity. The window also narrows the VECSEL emission, going from a FWHM of 5 nm to below 0.5 nm at a pump power of 40 W.

Cederberg, J. G.; Albrecht, A. R.; Ghasemkhani, M.; Melgaard, S. D.; Sheik-Bahae, M.

2014-05-01

120

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

SciTech Connect

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.

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

2010-01-01

121

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

122

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

E-print Network

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

Annunziata, Onofrio

123

Cavity controlled spectral singularity  

E-print Network

We study theoretically a PT-symmetric saturable balanced gain-loss system in a ring cavity configuration. The saturable gain and loss are modeled by two-level medium with or without population inversion. We show that the specifics of the spectral singularity can be fully controlled by the cavity and the atomic detuning parameters. The theory is based on the mean-field approximation as in standard theory of optical bistability. Further, in the linear regime we demonstrate the regularization of the singularity in detuned systems, while larger input power levels are shown to be adequate to limit the infinite growth in absence of detuning

Reddy, K Nireekshan

2014-01-01

124

Discerning crystal growth from diffusion profiles in zoned olivine by in situ Mg-Fe isotopic analyses  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

125

Discerning crystal growth from diffusion profiles in zoned olivine by in situ MgFe isotopic analyses  

USGS Publications Warehouse

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 MgFe 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.

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

2013-01-01

126

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

SciTech Connect

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

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

2012-03-15

127

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)

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.

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

2014-09-01

128

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

SciTech Connect

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.

Gotschke, T.; Schumann, T.; Limbach, F.; Calarco, R. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Juelich GmbH and JARA-Fundamentals of Future Information Technology (FIT), 52425 Juelich (Germany); Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Stoica, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Juelich GmbH and JARA-Fundamentals of Future Information Technology (FIT), 52425 Juelich (Germany)

2011-03-07

129

Diffusion-controlled growth of hydrogen pores in aluminum-silicon castings: In situ observation and modeling  

SciTech Connect

In situ observations were made of the nucleation and growth kinetics of hydrogen porosity during the directional solidification of aluminium-7 wt% silicon (Al7Si) with TiB{sub 2} grain refiner added, using an X-ray temperature gradient stage (XTGS). The effect of altering the solidification velocity on the growth rate and morphology of the porosity formed was characterized by tracking individual pores with digital analysis of the micro-focal video images. It was found that increasing the solidification velocity caused the pore radius to decrease and pore density to increase. Insight gained from the experimental results was used to develop a computational model of the evolution of hydrogen pores during solidification of aluminum-silicon cast alloys. The model solves for the diffusion-limited growth of the pores in spherical coordinates, using a deterministic solution of the grain nucleation and growth as a sub-model to calculate the parameters that depend upon the fraction solid. Sensitivity analysis was carried out to assess the effects of equiaxed grain density, pore density, initial hydrogen content and cooling rate. The model agrees with the experimental results within the resolution limits of the XTGS experiments performed.

Atwood, R.C.; Sridhar, S.; Zhang, W.; Lee, P.D.

2000-01-24

130

Ion-bombardment-enhanced diffusion during the growth of sputtered superlattice thin films  

Microsoft Academic Search

A technique is presented for determining the enhancement in solid-state diffusion caused by low-energy ion bombardment. In this technique, superlattice films are grown under varying conditions of ion bombardment and the amplitude of the resulting composition modulation wave is determined by analyzing x-ray diffraction satellite peaks surrounding the central Bragg peaks. The amplitude is in turn related to the enhanced

A. H. Eltoukhy; J. E. Greene

1978-01-01

131

Longitudinal regression analysis of spatialtemporal growth patterns of geometrical diffusion measures in early postnatal brain development with diffusion tensor imaging  

Microsoft Academic Search

Although diffusion tensor imaging (DTI) has provided substantial insights into early brain development, most DTI studies based on fractional anisotropy (FA) and mean diffusivity (MD) may not capitalize on the information derived from the three principal diffusivities (e.g. eigenvalues). In this study, we explored the spatial and temporal evolution of white matter structures during early brain development using two geometrical

Yasheng Chen; Hongyu An; Hongtu Zhu; Valerie Jewells; Diane Armao; Dinggang Shen; John H. Gilmore; Weili Lin

2011-01-01

132

Influence of Ni Catalyst Layer and TiN Diffusion Barrier on Carbon Nanotube Growth Rate  

PubMed Central

Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 700C. This behavior is likely related to a transition in the growth mode from a predominantly base growth to that of a tip growth. For Ni layer greater than 9 nm the growth rate, as well as the CNT diameter, variations become insignificant. We have also observed that a TiN barrier layer appears to favor the growth of thinner CNTs compared to a SiO2 layer. PMID:20672089

2010-01-01

133

Growth and properties of W-B-N diffusion barriers deposited by chemical vapor deposition  

SciTech Connect

The authors have used chemical vapor deposition to grow ternary tungsten-based diffusion barriers to determine if they exhibit properties similar to those of sputter-deposited ternaries. A range of different W-B-N compositions in a band of compositions roughly between 20 and 40% W were produced. The deposition temperature was low, 350 C, and the precursors used are well accepted by the industry. Deposition rates are high for a diffusion barrier application. Resistivities range from 200 to 20,000 {micro}{Omega}-cm, the films with the best barrier properties having {approximately}1,000 {micro}{Omega}-cm resistivities. Adhesion to oxides is sufficient to allow these films to be used as the adhesion layer in a tungsten chemical mechanical polishing plug application. The films are x-ray amorphous as-deposited and have crystallization temperatures of up to 900 C. Barrier performance against Cu has been tested using diode test structures. A composition of W{sub .23}B{sub .49}N{sub .28} was able to prevent diode failure up to a 700 C, 30 minute anneal. These materials, deposited by CVD, display properties similar to those deposited by physical deposition techniques.

Fleming, J.G.; Roherty-Osmun, E.; Custer, J.; Smith, P.M. [Sandia National Labs., Albuquerque, NM (United States); Reid, J.S.; Nicolet, M.A. [California Inst. of Tech., Pasadena, CA (United States)

1995-10-01

134

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

E-print Network

. Albrighta, * a Department of Chemistry, Texas Christian University, Fort Worth, TX 76129, USA b Dipartimento Technologies, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551, USA Abstract the driving force for nucleation and crystal growth of lysozyme chloride. # 2001 Elsevier Science B.V. All

Annunziata, Onofrio

135

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

ERIC Educational Resources Information Center

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

Jolliffe, Lee

136

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

PubMed Central

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

Hogea, Cosmina; Davatzikos, Christos; Biros, George

2010-01-01

137

Microfabricated diffusion source  

DOEpatents

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.

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

2008-07-15

138

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

PubMed Central

Background Intrauterine growth restriction (IUGR) affects 510% 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 4050% 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

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

2012-01-01

139

Compositionally modulated sputtered InSb\\/GaSb superlattices: Crystal growth and interlayer diffusion  

Microsoft Academic Search

Compositionally modulated single-crystal InSb\\/GaSb superlattice structures have been grown by multitarget sputtering in order to investigate the effects of film growth parameters on the defect structure, abruptness, and coherence of sputtered heterojunctions. The layer thicknesses studied ranged from 12 to 70 A?. The polycrystallinetosingle-crystal transition temperature Tc was found to decrease with decreasing average film-substrate lattice mismatch and modulation period,

A. H. Eltoukhy; J. E. Greene

1979-01-01

140

Compositionally modulated sputtered InSb\\/GaSb superlattices: Crystal growth and interlayer diffusion  

Microsoft Academic Search

Compositionally modulated single-crystal InSb\\/GaSb superlattice structures have been grown by multitarget sputtering in order to investigate the effects of film growth parameters on the defect structure, abruptness, and coherence of sputtered heterojunctions. The layer thicknesses studied ranged from 12 to 70 A˚. The polycrystalline-to-single-crystal ''transition temperature'' Tc was found to decrease with decreasing average film-substrate lattice mismatch and modulation period,

A. H. Eltoukhy; J. E. Greene

1979-01-01

141

Pattern transition between periodic Liesegang pattern and crystal growth regime in reaction-diffusion systems  

NASA Astrophysics Data System (ADS)

The pattern transition between periodic precipitation pattern formation (Liesegang phenomenon) and pure crystal growth regimes is investigated in silver nitrate and potassium dichromate system in mixed agarose-gelatin gel. Morphologically different patterns were found depending on the quality of the gel, and transition between these typical patterns can be controlled by the concentration of gelatin in mixed gel. Effect of temperature and hydrodynamic force on precipitation pattern structure was also investigated.

Lagzi, Istvn; Ueyama, Daishin

2009-01-01

142

Incorporation of diffusion-weighted magnetic resonance imaging data into a simple mathematical model of tumor growth  

NASA Astrophysics Data System (ADS)

We build on previous work to show how serial diffusion-weighted MRI (DW-MRI) data can be used to estimate proliferation rates in a rat model of brain cancer. Thirteen rats were inoculated intracranially with 9L tumor cells; eight rats were treated with the chemotherapeutic drug 1,3-bis(2-chloroethyl)-1-nitrosourea and five rats were untreated controls. All animals underwent DW-MRI immediately before, one day and three days after treatment. Values of the apparent diffusion coefficient (ADC) were calculated from the DW-MRI data and then used to estimate the number of cells in each voxel and also for whole tumor regions of interest. The data from the first two imaging time points were then used to estimate the proliferation rate of each tumor. The proliferation rates were used to predict the number of tumor cells at day three, and this was correlated with the corresponding experimental data. The voxel-by-voxel analysis yielded Pearson's correlation coefficients ranging from -0.06 to 0.65, whereas the region of interest analysis provided Pearson's and concordance correlation coefficients of 0.88 and 0.80, respectively. Additionally, the ratio of positive to negative proliferation values was used to separate the treated and control animals (p <0.05) at an earlier point than the mean ADC values. These results further illustrate how quantitative measurements of tumor state obtained non-invasively by imaging can be incorporated into mathematical models that predict tumor growth.

Atuegwu, N. C.; Colvin, D. C.; Loveless, M. E.; Xu, L.; Gore, J. C.; Yankeelov, T. E.

2012-01-01

143

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

PubMed

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

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

2012-07-17

144

COMPARISON OF GKS CALCULATED CRITICAL ION TEMPERATURE GRADIENTS AND ITG GROWTH RATES TO DIII-D MEASURED GRADIENTS AND DIFFUSIVITIES  

SciTech Connect

OAK-B135 The gyrokinetic equations predict that various drift type waves or modes can be unstable in a tokamak. For some of these modes, such as the ion temperature gradient (ITG) mode and the electron temperature gradient mode, there exists a critical gradient, above which the mode is unstable. Since the existence of unstable modes can cause increased transport, plasmas which are centrally heated tend to increase in temperature gradient until the modes become unstable. Under some conditions the increased transport can fix the gradient at the critical value. here they present a comparison between the measured ion temperature gradients and the critical gradient as calculated by a gyrokinetic linear stability (GKS) code. They also present the maximum linear growth rate as calculated by this code for comparison to experimentally derived transport coefficients. The results show that for low confinement mode (L-mode) discharges, the measured ion temperature gradient is significantly greater than the GKS calculated critical gradient over a large region of the plasma. This is the same region of the plasma where the ion thermal diffusivity is large. For high confinement mode (H-mode) discharges the ion temperature gradient is closer to the critical gradient, but often still greater than the critical gradient over some region. For the best H-mode discharges, the ion temperature is less than or equal to the critical gradient over the whole plasma. In general they find that the position in the plasma where the ion thermal diffusivity starts to increase rapidly is where the maximum linear growth rate is greater than the E x B shearing rate.

BAKER,DR; STAEBLER,GM; PETTY,CC; GREENFIELD,CM; LUCE,TC

2003-04-01

145

Synchronization in an Optomechanical Cavity  

E-print Network

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.

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

2014-10-01

146

Synchronization in an Optomechanical Cavity  

E-print Network

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.

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

2014-01-01

147

Morphological diagram of diffusion driven aggregate growth in plane: Competition of anisotropy and adhesion  

NASA Astrophysics Data System (ADS)

Two-dimensional structures grown with Witten and Sander algorithm are investigated. We analyze clusters grown off-lattice and clusters grown with antenna method with N=3,4,5,6,7 and 8 allowed growth directions. With the help of variable probe particles technique we measure fractal dimension of such clusters D(N) as a function of their size N. We propose that in the thermodynamic limit of infinite cluster size the aggregates grown with high degree of anisotropy ( N=3,4,5) tend to have fractal dimension D equal to 3/2, while off-lattice aggregates and aggregates with lower anisotropy ( N>6) have D?1.710. Noise-reduction procedure results in the change of universality class for DLA. For high enough noise-reduction value clusters with N?6 have fractal dimension going to 3/2 when N??.

Menshutin, A. Yu.; Shchur, L. N.

2011-09-01

148

Nucleation and diffusion during growth of ternary Co1-xNixSi2 thin films studied by complementary techniques in real time  

NASA Astrophysics Data System (ADS)

The growth kinetics of ternary Co1-xNixSi2 thin films was studied in real time. The "Kissinger" method was applied to the results of ramped sheet resistance measurements to extract the apparent activation energy for the growth process. By simultaneously acquiring sheet resistance, x-ray diffraction and laser light scattering data on one hand and combining resistance measurements and Rutherford backscattering spectrometry on the other hand, we could distinguish between the initial, nucleation controlled thin film growth, and the subsequent diffusion controlled growth. The apparent activation energy for the initial growth decreases with increasing Ni concentration as a result of a lower nucleation barrier for the ternary disilicide. The markedly different microstructure of the ternary Co1-xNixSi2 films with respect to pure CoSi2 layers lies at the origin of a lower activation energy for the diffusion controlled growth of the ternary films. Despite the low activation energy, these films grow at a much slower rate than CoSi2 films due to the large grain size and consequently lower density of grain boundary diffusion paths. These results explain the unexpected high thermal budget required for the formation of low resistivity Co1-xNixSi2 thin films.

Smeets, D.; Demeulemeester, J.; De Keyser, K.; Deduytsche, D.; Detavernier, C.; Comrie, C. M.; Theron, C. C.; Lavoie, C.; Vantomme, A.

2008-11-01

149

Suppression of cavity formation in ceramics: prospects for superplasticity  

Microsoft Academic Search

Ceramics exhibit macroscopic stress\\/strain rate relations that should lead to superplastic extension. However, premature fracture is normally encountered, due to the formation and growth of grain-boundary cavities. Thus, cavity nucleation and growth were analyzed in an attempt to identify microstructures and\\/or strain-rate regimes that would suppress cavity evolution and hence allow superplasticity. Analysis of cavity nucleation indicates that fine-grained materials

A. G. Evans; J. R. Rice; J. P. Hirth

1980-01-01

150

Regulation of lipid composition in Acholeplasma laidlawii and Escherichia coli membranes: NMR studies of lipid lateral diffusion at different growth temperatures.  

PubMed

Lipid lateral diffusion coefficients have been directly determined by pulsed field gradient NMR spectroscopy on macroscopically aligned, fully hydrated lamellar phases containing dimyristoylphosphatidylcholine and total lipid extracts from Acholeplasma laidlawii and Escherichia coli. The temperature dependence of the diffusion coefficient was of the Arrhenius type in the temperature interval studied. The sharp increase in the diffusion coefficient at the growth temperature of E. coli obtained by FRAP measurements, using a fluorescent probe molecule (Jin, A. J., Edidin, M., Nossal, R., and Gershfeld, N. L. (1999) Biochemistry 38, 13275-13278), was not observed. Thus, we conclude that the lipid structural properties (i.e., those affecting the lipid phase behavior), rather than the lipid dynamics, are involved in the adjustment of the membrane lipid composition. Further support for this conclusion is given by the finding that lipid extracts from A. laidlawii grown at different temperatures have about the same diffusion coefficients. Finally, the lipid lateral diffusion in bilayers of phospholipids was found to be much faster than that in bilayers of mainly glucolipids, which can be understood in terms of a free volume theory for the diffusion process. PMID:12234195

Lindblom, Gran; Ordd, Greger; Rilfors, Leif; Morein, Sven

2002-09-24

151

Flow above natural and ventilated cavities  

SciTech Connect

This paper presents an experimental study of velocities and turbulent fluctuations, around two-dimensional vapor cavities in water. A Laser-Doppler Velocimeter was used above and in the wake of natural or ventilated cavities, attached to a ridge of the water tunnel. On the first half of the cavity, the boundary layer developing before the cavity, is convected above the interface and diffused. On the second half and in the wake, a large velocity defect and high level of fluctuations, created by the cavity itself, are observed. The effect of velocity and cavity length are investigated, whereas the suppression of mass transfer (ventilated cavity) only influence the results in the wake. The cavity deduced from an image processing technique show that the lowest measurement points are located in a two-phase flow medium, so that streamlines deduced from the velocities are not representative of the mass flow rate distribution. Further measurements are expected to give the mass flow rate towards the cavity.

Merle, L. [Institute National Polytechnique de Grenoble, St. Martin d`Heres (France). Centre de Recherches et d`Essais de Machines Hydrauliques de Grenoble; Delannoy, Y. [Societe Europeenne de Propulsion, Vernon (France)

1994-12-31

152

D:PAC03 WPAB011.tex ERL 03-09 Emittance Growth Study Using 3DE Code for the ERL Injector Cavities with  

E-print Network

beam pipe dimension of the #2;rst structure is slightly different than the pipe dimensions of the other : Two cells cavity - NO couplers #15; Structure II : Two cells + ONE vertical coupler at the bottom vertical symmet- ric couplers at the bottom and top of the output pipe located at z = 0:281 m from

153

Theory of long-range diffusion of proteins on a spherical biological membrane: application to protein cluster formation and actin-comet tail growth.  

PubMed

Breaking of symmetry is often required in biology in order to produce a specific function. In this work we address the problem of protein diffusion over a spherical vesicle surface towards one pole of the vesicle in order to produce ultimately an active protein cluster performing a specific biological function. Such a process is, for example, prerequisite for the assembling of proteins which then cooperatively catalyze the polymerization of actin monomers to sustain the growth of actin tails as occurs in natural vesicles such as those contained in Xenopus eggs. By this process such vesicles may propel themselves within the cell by the principle of action-reaction. In this work the physicochemical treatment of diffusion of large biomolecules within a cellular membrane is extended to encompass the case when proteins may be transiently poised by corral-like structures partitioning the membrane as has been recently documented in the literature. In such case the exchange of proteins between adjacent corrals occurs by energy-gated transitions instead of classical Brownian motion, yet the present analysis shows that long-range movements of the biomolecules may still be described by a classical diffusion law though the diffusion coefficient has then a different physical meaning. Such a model explains why otherwise classical diffusion of proteins may give rise to too small diffusion coefficients compared to predictions based on the protein dimension. This model is implemented to examine the rate of proteins clustering at one pole of a spherical vesicle and its outcome is discussed in relevance to the mechanism of actin comet tails growth. PMID:19475636

Amatore, Christian; Oleinick, Alexander I; Klymenko, Oleksiy V; Svir, Irina

2009-07-13

154

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

PubMed

The ability to integrate carbon nanotubes, especially single-walled carbon nanotubes, seamlessly onto silicon would expand their range of applications considerably. Though direct integration using chemical vapor deposition is the simplest method, the growth of single-walled carbon nanotubes on bare silicon and on ultrathin oxides is greatly inhibited due to the formation of a noncatalytic silicide. Using X-ray photoelectron spectroscopy, we show that silicide formation occurs on ultrathin oxides due to thermally activated metal diffusion through the oxide. Silicides affect the growth of single-walled nanotubes more than multi-walled nanotubes due to the increased kinetics at the higher single-walled nanotube growth temperature. We demonstrate that nickel and iron catalysts, when deposited on clean silicon or ultrathin silicon dioxide layers, begin to form silicides at relatively low temperatures, and that by 900 degrees C, all of the catalyst has been incorporated into the silicide, rendering it inactive for subsequent single-walled nanotube growth. We further show that a 4-nm silicon dioxide layer is the minimum diffusion barrier thickness that allows for efficient single-walled nanotube growth. PMID:17193143

Simmons, Jason M; Nichols, Beth M; Marcus, Matthew S; Castellini, Olivia M; Hamers, Robert J; Eriksson, Mark A

2006-07-01

155

Diffusion Geometry Diffusion Geometry  

E-print Network

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

Hirn, Matthew

156

Theory for intermetallic phase growth between cu and liquid Sn-Pb solder based on grain boundary diffusion control  

Microsoft Academic Search

Kinetics of phase formation during interdiffusion in solid-liquid diffusion couples are influenced by the morphology of the\\u000a intermediate compound layer. In some cases, an intermediate compound layer is formed which has very fine grain size. This\\u000a condition favors grain boundary diffusion as the predominant mechanism for transport through the layer. In systems where grain\\u000a coarsening occurs, the coarsening kinetics will

Matt Schaefer; Raymond A. Fournelle; Jin Liang

1998-01-01

157

Flow through porous media from a pressurized spherical cavity  

Microsoft Academic Search

The saturated-unsaturated flow generated by injecting water into a soil from a pressurized spherical cavity is modeled mathematically. Approximate solutions are obtained analytically for arbitrary pressure head when the soil water diffusivity varies rapidly with water content. In particular, the relationship between the cavity pressure and cumulative absorption is established, and formulae for the position of the saturation and wetting

D. Lockington; M. Hara; W. Hogarth; J.-Y. Parlange

1989-01-01

158

Fast Turnover of L1 Adhesions in Neuronal Growth Cones Involving Both Surface Diffusion and Exo/Endocytosis of L1 Molecules  

PubMed Central

We investigated the interplay between surface trafficking and binding dynamics of the immunoglobulin cell adhesion molecule L1 at neuronal growth cones. Primary neurons were transfected with L1 constructs bearing thrombin-cleavable green fluorescent protein (GFP), allowing visualization of newly exocytosed L1 or labeling of membrane L1 molecules by Quantum dots. Intracellular L1GFP vesicles showed preferential centrifugal motion, whereas surface L1GFP diffused randomly, revealing two pathways to address L1 to adhesive sites. We triggered L1 adhesions using microspheres coated with L1Fc protein or anti-L1 antibodies, manipulated by optical tweezers. Microspheres coupled to the actin retrograde flow at the growth cone periphery while recruiting L1GFP molecules, of which 50% relied on exocytosis. Fluorescence recovery after photobleaching experiments revealed a rapid recycling of L1GFP molecules at L1Fc (but not anti-L1) bead contacts, attributed to a high lability of L1L1 bonds at equilibrium. L1GFP molecules truncated in the intracellular tail as well as neuronal cell adhesion molecules (NrCAMs) missing the clathrin adaptor binding sequence showed both little internalization and reduced turnover rates, indicating a role of endocytosis in the recycling of mature L1 contacts at the base of the growth cone. Thus, unlike for other molecules such as NrCAM or N-cadherin, diffusion/trapping and exo/endocytosis events cooperate to allow the fast renewal of L1 adhesions. PMID:17538021

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

2007-01-01

159

Hydrofracture from a growing cavity  

SciTech Connect

The Los Alamos KRAK code has been used to calculate fracturing away from the growing cavity formed by a nuclear detonation. In the 55 ms before rebound, the stress in the surrounding rock is decreasing, and conditions for fracture propagation are good. During this interval, hydrofractures driven by the high-temperature, high-pressure gases within the cavity grow readily. Fracture growth slows when the stress increases as the residual hoop is formed during rebound. However, cracks are found to escape through the residual stress field. The effects of initial conditions and zoning on the numerical calculations are discussed, and the roles of the media saturation and roughness are briefly considered. The largest uncertainty in these calculations is the manner in which the effective pressure used in computing crack widths is extended into the cavity region. Because the present calculations have been done using a very conservative scheme, actual fractures should grow even more readily. We conclude that hydrofracture is an important, if not dominant, process in transporting mass and energy out of a cavity formed by a nuclear detonation.

Kunkle, T.D.; Travis, B.J.

1981-01-01

160

Growth behavior and field-induced diffusion of Ni clusters/particles on SrTiO3 (001) observed by UHV-TEM/STM  

NASA Astrophysics Data System (ADS)

The fundamental and technological importance of metal clusters and particles on oxide surfaces is growing. Here, room temperature deposited Ni clusters and particles on clean SrTiO3 (001) surfaces were analyzed with a UHV-TEM/STM combined system to investigate reaction, growth, morphology, and crystal structure consistently. STM observation revealed their growth process from isolated clusters almost of the size of the nuclei to bigger particles. From TEM observation, it was found that small clusters have a semi-commensurate epitaxial orientation relationship, but that bigger ones grow into an incommensurate cube-on-cube epitaxial orientation relationship. STS measurement on Ni particles caused field-induced diffusion of Ni atoms, in which piling up of Ni was recognized at the positions of the STM tips. This is assumed to be related with interfacial reaction.

Tanaka, Miyoko

2013-09-01

161

Cavity turnover and equilibrium cavity densities in a cottonwood bottomland  

USGS Publications Warehouse

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.

Sedgwick, James A.; Knopf, Fritz L.

1992-01-01

162

Cavity-controlled spectral singularity.  

PubMed

We study theoretically a parity-time (PT)-symmetric, saturable, balanced gain-loss system in a ring-cavity configuration. The saturable gain and loss are modeled by a two-level medium with or without population inversion. We show that the specifics of the spectral singularity can be fully controlled by the cavity and the atomic detuning parameters. The theory is based on the mean-field approximation, as in the standard theory of optical bistability. Further, in the linear regime we demonstrate the regularization of the singularity in detuned systems, while larger input power levels are shown to be adequate to limit the infinite growth in absence of detunings. PMID:25078237

Nireekshan Reddy, K; Dutta Gupta, S

2014-08-01

163

Cancer of the oral cavity and oropharynx  

PubMed Central

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

Zbaeren, Peter; Thoeny, Harriet C.

2010-01-01

164

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

Microsoft Academic Search

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

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

2006-01-01

165

The importance of microclimate variation in determining size, growth and survival of avian offspring: experimental evidence from a cavity nesting passerine.  

PubMed

Organisms are expected to balance energy allocation in such a way that fitness is maximized. While much research has focussed on allocation strategies of reproducing parents, in particular birds, relatively little attention has been paid to how nestlings allocate energy while in the nest. Nestling birds are faced with a trade-off between devoting energy to growth or to thermoregulation, and in altricial species it is likely that the thermal environment of the nest site influences the nature of this trade-off. Here, we experimentally investigate how altering the microclimate of nests affects the growth, size and survival, as well as cell-mediated immune (CMI) response, of nestling tree swallows (Tachycineta bicolor) in a temperate environment. We place air-activated heating pads in nests of swallows when young were between 4 days and 16 days of age, and compared performance of offspring to control nests. Our manipulation raised temperatures of heated nests by approximately 5 degrees C compared to control nests. Offspring in heated nests had enhanced survival while in the nest, and we also found that they were heavier and had longer ninth primary feathers at 16 days of age. In addition, heating nest boxes resulted in significantly faster growth of primaries, and there was a trend for growth rates of mass to also be higher in heated nests. There were no significant differences between heated and control nests in growth rate or size of tarsus at age 16 days, and we speculate that this lack of response to elevated nest temperatures may be due to growth of skeletal structures being limited by other factors such as calcium availability. We also found no difference between heated and control nests in CMI response. Nonetheless, our results show overall that increasing temperatures of nests has significant benefits that enhance the fitness of offspring. As provisioning rates to offspring did not differ between heated and control nests, we suspect that the beneficial effects of heating were not the consequence of changes in parental behaviour. Our results provide insight into factors, other than food supply, that have important consequences in determining reproductive success of birds breeding in temperate environments. PMID:15891832

Dawson, Russell D; Lawrie, Cheyenne C; O'Brien, Erin L

2005-07-01

166

Electromagnetic SCRF Cavity Tuner  

SciTech Connect

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.

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

2009-05-01

167

Characterization of cavity wakes  

NASA Astrophysics Data System (ADS)

Scope and Method of Study. This research focused on flow over deep cavities at subsonic speeds with emphasis on the wake downstream of the cavity. Cavity wake behaviors have not been studied in detail and are a major concern for air vehicles with cavities and in particular for optical sensor systems installed in cavities. Other key behaviors for sensor survival and performance are cavity resonance and turbulence scales in the shear layer. A wind tunnel test apparatus was developed to explore cavity and wake characteristics. It consisted of a test section insert for the OSU Indraft Wind Tunnel with an additional contraction cone for significantly increased speed. The test section included a variable depth cavity in a boundary layer splitter plate/fairing assembly, a Y-Z traverse and pitot rake with in-situ pressure transducers for high frequency response. Flows were measured over clean cavities with length to depth (L/D) ratios of 4 to 1/2 and on cavities with a porous fence for resonance suppression. Measurements were taken in streamwise and cross-stream sections to three cavity lengths downstream of the cavity trailing edge. Flow visualization using laser sheet and smoke injection was also used. Findings and Conclusions. The high speed insert demonstrated a significant new capability for the OSU wind tunnel, reaching speeds of 0.35 Mach (390 feet/second) in a 14"x14" test section. Inlet room flow was found to be quite unsteady and recommendations are made for improved flow and quantitative visualization. Key findings for cavity wake flow include its highly three dimensional nature with asymmetric peaks in cross section with boundary layer thicknesses and integral length scales several times that of a normal flat plate turbulent boundary layer (TBL). Turbulent intensities (TI) of 35% to 55% of freestream speeds were measured for the clean configuration. Fence configuration TI's were 20% to 35% of free stream and, in both configurations, TI's decayed to approximately that of a flat plate TBL by 3 cavity lengths downstream from the cavity trailing edge. Fence flow visualization showed edge vortices and jets through the perforations that suggest the potential for minimizing turbulence intensity and scales while still suppressing cavity resonance.

Kidd, James A.

168

Optically measuring interior cavities  

DOEpatents

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.

Stone, Gary Franklin (Livermore, CA)

2008-12-21

169

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

E-print Network

,19] is the ideal tool to characterize the growth process in situ in a noninvasive way. While the intensity of organic thin films followed by time-resolved specular and off-specular scattering C. Frank,1 J. Nov�ak,1-dependent collective rearrangement of DIP molecules from a transient surface induced to the thin-film phase, which can

Schreiber, Frank

170

Growth  

NSDL National Science Digital Library

Introduction to models of economic growth with a great deal of focus on the Solow Growth Model both its theory and testing it with data. Also contains a discussion of the effects of the Greenspan Put. From a macroeconomics course at the the Massachusetts Institute of Technology.

Technology, Massachusetts I.

171

Computation of cavity-by-cavity flow development in generic labyrinth seals  

E-print Network

presented, providing additional insight into the character of the flow, Results are presented for straight-through seals of both teeth-on-stator and teeth-on-rotor types. Previously unavailable predictions of swirl velocity development are provided... for the development of simple models. These indicate significantly higher cavity-by-cavity swirl growth rates for teeth-on-rotor as opposed to teeth-on-stator generic seals. Dedicated to our Lord and Saviour Jesus Christ NOMENCLATURE point coefficien( neighbor...

Nail, Gregory Howard

2012-06-07

172

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

Background Intrauterine growth restriction (IUGR) affects 510% 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

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

2013-01-01

173

Explosives with Lined Cavities  

Microsoft Academic Search

Explosives detonated in contact with thick steel plates produce much deeper holes in the steel when there is a cavity in the explosive in contact with the plate. While this phenomenon has been known for more than 150 years, the enormous increase in penetrating power that can be produced by lining the explosive cavity with thin metal has been discovered

Garrett Birkhoff; Duncan P. MacDougall; Emerson M. Pugh; Geoffrey Taylor

1948-01-01

174

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)

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.

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

175

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

SciTech Connect

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.

Kuranova, I. P., E-mail: inna@ns.crys.ras.ru; Smirnova, E. A.; Abramchik, Yu. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Chupova, L. A.; Esipov, R. S. [Russian Academy of Sciences, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry (Russian Federation); Akparov, V. Kh. [Research Institute for Genetics and Selection of Industrial Microorganisms, Scientific Center of Russian Federation (Russian Federation); Timofeev, V. I.; Kovalchuk, M. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2011-09-15

176

Passivated niobium cavities  

DOEpatents

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.

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

2006-12-19

177

Emittance control in rf cavities and solenoids  

NASA Astrophysics Data System (ADS)

We study emittance growth for transport of uniform and Gaussian beams of particles in rf cavities and solenoids and show analytically its dependence on initial beam parameters. Analytical results are confirmed with simulation studies over a broad range of different initial beams.

Eshraqi, Mohammad; Franchetti, Giuliano; Lombardi, Alessandra M.

2009-02-01

178

Effects of growth temperature and oxidant feeding time on residual C- and N-related impurities and Si diffusion behavior in atomic-layer-deposited La2O3 thin films  

NASA Astrophysics Data System (ADS)

The effects of oxidant (H2O) feeding time and growth temperature on the C- and N-related impurities and Si diffusion behavior in the atomic-layer-deposition (ALD) of La2O3 films were examined using in situ X-ray photoelectron spectroscopy analysis. Longer H2O pulse time assisted in a complete ligand exchange reaction during ALD, which suppressed the accumulation in the film of residual C- and N-related byproducts/impurities with low bonding energy that originated from incompletely reacted ligands and carboxyl compound intermediate phases. In addition, this phenomenon slightly increased the growth rate of the La2O3 film even under the nominal growth-saturated ALD conditions because the concentration of residual C- and N-related byproducts/impurities, which disturb the formation of the active sites, was reduced. The band gap energy of the films increased slightly with H2O feeding time due to the reduction of C impurities. The residual C- and N-related byproducts/impurities and carboxyl compound intermediate phases in the La2O3 films were effectively reduced by increased growth temperature. However, increased growth temperature enhanced the Si out-diffusion from the substrate into the films and decreased the film growth rate because the surface functional groups for sequential film growth during ALD were reduced. The enhanced Si out-diffusion increased the band gap of the film and the valence band off-set with respect to the Si substrate.

Park, Tae Joo; Sivasubramani, Prasanna; Wallace, Robert M.; Kim, Jiyoung

2014-02-01

179

A two-dimensional model for stress driven diffusion in bone tissue.  

PubMed

The growth and resorption of bone are governed by interaction between several cells such as bone-forming osteoblasts, osteocytes, lining cells and bone-resorbing osteoclasts. The cells considered in this study reside in the periosteum. Furthermore, they are believed to be activated by certain substances to initiate bone growth. This study focuses on the role that stress driven diffusion plays in the transport of these substances from the medullary cavity to the periosteum. Calculations of stress driven diffusion are performed under steady state conditions using a finite element method with the concentration of nutrients in the cambium layer of the periosteum obtained for different choices of load frequencies. The results are compared with experimental findings, suggesting that increased bone growth occurs in the neighbourhood of relatively high nutrient concentration. PMID:23865643

Lindberg, Gustav; Banks-Sills, Leslie; Sthle, Per; Svensson, Ingrid

2015-04-01

180

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

PubMed

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

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

2013-06-15

181

Superconducting TESLA cavities  

Microsoft Academic Search

The conceptional design of the proposed linear electron-positron collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with an accelerating gradient of Eacc>=25 MV\\/m at a quality factor Q0>=5109. The design goal for the cavities of the TESLA Test Facility (TTF) linac was set to the more moderate value of Eacc>=15 MV\\/m. In a first series of 27

B. Aune; R. Bandelmann; D. Bloess; B. Bonin; A. Bosotti; M. Champion; C. Crawford; G. Deppe; B. Dwersteg; D. A. Edwards; H. T. Edwards; M. Ferrario; M. Fouaidy; P.-D. Gall; A. Gamp; A. Gssel; J. Graber; D. Hubert; M. Hning; M. Juillard; T. Junquera; H. Kaiser; G. Kreps; M. Kuchnir; R. Lange; M. Leenen; M. Liepe; L. Lilje; A. Matheisen; W.-D. Mller; A. Mosnier; H. Padamsee; C. Pagani; M. Pekeler; H.-B. Peters; O. Peters; D. Proch; K. Rehlich; D. Reschke; H. Safa; T. Schilcher; P. Schmser; J. Sekutowicz; S. Simrock; W. Singer; M. Tigner; D. Trines; K. Twarowski; G. Weichert; J. Weisend; J. Wojtkiewicz; S. Wolff; K. Zapfe

2000-01-01

182

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

NASA Technical Reports Server (NTRS)

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.

Wendt, Bruce J.

2000-01-01

183

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 ...

184

Growth  

NASA Astrophysics Data System (ADS)

This chapter is devoted to the growth of ZnO. It starts with various techniques to grow bulk samples and presents in some detail the growth of epitaxial layers by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and pulsed laser deposition (PLD). The last section is devoted to the growth of nanorods. Some properties of the resulting samples are also presented. If a comparison between GaN and ZnO is made, very often the huge variety of different growth techniques available to fabricate ZnO is said to be an advantage of this material system. Indeed, growth techniques range from low cost wet chemical growth at almost room temperature to high quality MOCVD growth at temperatures above 1, 000?C. In most cases, there is a very strong tendency of c-axis oriented growth, with a much higher growth rate in c-direction as compared to other crystal directions. This often leads to columnar structures, even at relatively low temperatures. However, it is, in general, not straight forward to fabricate smooth ZnO thin films with flat surfaces. Another advantage of a potential ZnO technology is said to be the possibility to grow thin films homoepitaxially on ZnO substrates. ZnO substrates are mostly fabricated by vapor phase transport (VPT) or hydrothermal growth. These techniques are enabling high volume manufacturing at reasonable cost, at least in principle. The availability of homoepitaxial substrates should be beneficial to the development of ZnO technology and devices and is in contrast to the situation of GaN. However, even though a number of companies are developing ZnO substrates, only recently good quality substrates have been demonstrated. However, these substrates are not yet widely available. Still, the situation concerning ZnO substrates seems to be far from low-cost, high-volume production. The fabrication of dense, single crystal thin films is, in general, surprisingly difficult, even when ZnO is grown on a ZnO substrate. However, molecular beam epitaxy (MBE) delivers high quality ZnMgO-ZnO quantum well structures. Other thin film techniques such as PLD or MOCVD are also widely used. The main problem at present is to consistently achieve reliable p-type doping. For this topic, see also Chap. 5. In the past years, there have been numerous publications on p-type doping of ZnO, as well as ZnO p-n junctions and light emitting diodes (LEDs). However, a lot of these reports are in one way or the other inconsistent or at least incomplete. It is quite clear from optical data that once a reliable hole injection can be achieved, high brightness ZnO LEDs should be possible. In contrast to that expectation, none of the LEDs reported so far shows efficient light emission, as would be expected from a reasonable quality ZnO-based LED. See also Chap. 13. As a matter of fact, there seems to be no generally accepted and reliable technique for p-type doping available at present. The reason for this is the unfavorable position of the band structure of ZnO relative to the vacuum level, with a very low lying valence band. See also Fig. 5.1. This makes the incorporation of electrically active acceptors difficult. Another difficulty is the huge defect density in ZnO. There are many indications that defects play a major role in transport and doping. In order to solve the doping problem, it is generally accepted that the quality of the ZnO material grown by the various techniques needs to be improved. Therefore, the optimization of ZnO epitaxy is thought to play a key role in the further development of this material system. Besides being used as an active material in optoelectronic devices, ZnO plays a major role as transparent contact material in thin film solar cells. Polycrystalline, heavily n-type doped ZnO is used for this, combining a high electrical conductivity with a good optical transparency. In this case, ZnO thin films are fabricated by large area growth techniques such as sputtering. For this and other applications, see also Chap. 13.

Waag, Andreas

185

Ring resonant cavities for spectroscopy  

DOEpatents

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).

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

1999-01-01

186

Ring resonant cavities for spectroscopy  

DOEpatents

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.

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

1999-06-15

187

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)

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.

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

2014-04-01

188

Erbium diffusion in silicon dioxide  

SciTech Connect

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.

Lu Yingwei; Julsgaard, B.; Petersen, M. Christian [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Jensen, R. V. Skougaard [Department of Physics and Nanotechnology, Aalborg University, DK-9220 Aalborg O (Denmark); Pedersen, T. Garm; Pedersen, K. [Department of Physics and Nanotechnology, Aalborg University, DK-9220 Aalborg O (Denmark); Interdisciplinary Nanoscience Center-iNANO, DK-8000 Aarhus C (Denmark); Larsen, A. Nylandsted [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Interdisciplinary Nanoscience Center-iNANO, DK-8000 Aarhus C (Denmark)

2010-10-04

189

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

SciTech Connect

Accurate models of protein diffusion are important in a number of applications, including liquid-liquid phase separation and growth of protein crystals for X-ray diffraction studies. In concentrated multicomponent protein systems, significant deviations from pseudobinary behavior can be expected. Rayleigh interferometry is used to measure the four elements (D{sub if}){sub v} of the ternary diffusion coefficient matrix for the extensively investigated protein, hen egg-white lysozyme (component 1) in aqueous NaCl (component 2) at pH 4.5 and 25 C. These are the first multicomponent diffusion coefficients measured for any protein system at concentrations high enough to be relevant to modeling and prediction of crystal growth or other phase transitions, and the first for a system involving lysozyme at any concentration. The four ternary diffusion coefficients for the system lysozyme chloride/NaCl/water are reported for lysozyme chloride at 0.60 mM (8.6 mg/mL) and NaCl at concentrations of 0.25, 0.50, 0.65, 0.90, and 1.30 M (1.4, 2.8, 3.7, 5.1, and 7.2 wt %), with the latter two compositions being supersaturated. One cross-term, (D{sub 21}){sub v}, is 80--259 times larger than the main term (D{sub 11}){sub v} and 7--18 times larger than (D{sub 22}){sub v}. Standard interferometric diagnostic tests indicate that aggregation is unimportant in the experiments. The authors also present binary diffusion coefficients D{sub v} for lysozyme chloride/water at concentrations from 0.43 to 3.08 mM (6.2--44.1 mg/mL), at the same pH and temperature. The precision of the results is about 0.1% for the binary diffusion coefficients and diagonal ternary diffusion coefficients, and about 1--2% for the cross-terms. For the ternary systems investigated, they show that a single pseudobinary diffusion coefficient does not accurately describe diffusive transport, and predictions by simple models such as the Nernst-Hartley equations are inaccurate at the higher concentrations considered here. Finally, dynamic light-scattering diffusion coefficients, differing form both the interferometrically measured (D{sub ij}){sub v} and a theoretical prediction of light-scattering diffusion coefficients in multicomponent systems, are reported for the same solutions used for the ternary experiments at 1.30 M.

Albright, J.G.; Annunziata, O. [Texas Christian Univ., Fort Worth, TX (United States). Chemistry Dept.] [Texas Christian Univ., Fort Worth, TX (United States). Chemistry Dept.; Miller, D.G. [Texas Christian Univ., Fort Worth, TX (United States). Chemistry Dept.] [Texas Christian Univ., Fort Worth, TX (United States). Chemistry Dept.; [Lawrence Livermore National Lab., CA (United States); Paduano, L. [Texas Christian Univ., Fort Worth, TX (United States). Chemistry Dept.] [Texas Christian Univ., Fort Worth, TX (United States). Chemistry Dept.; [Univ. di Napoli, Naples (Italy). Dipt. di Chimica; Pearlstein, A.J. [Univ. of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering] [Univ. of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering

1999-04-14

190

Primary platelet-derived growth factor-producing, spindle-shaped diffuse large B-cell lymphoma of the skull: a case report and literature review  

PubMed Central

A 39-year-old woman with a right frontal mass underwent a cranial bone tumor biopsy. Histopathologic examination of hematoxylin and eosinstained slides showed spindle-shaped tumor cells in a storiform pattern, appearing somewhat like a sarcoma. However, the tumor cells were CD20-positive by immunohistochemical staining. Therefore, a diagnosis of spindle-shaped diffuse large B-cell lymphoma (Sp-DLBCL) was made. There have been at least 35 cases of Sp-DLBCL documented in the literature, and most were of the germinal center type, while the present case is the first report of a vimentin-positive primary Sp-DLBCL of the skull. The DLBCL in this case was immunohistochemically stained for six representative cytokines that might give rise to fibrosis, due to the evidence of fibroblastic proliferation. The DLBCL cells were positive for platelet-derived growth factor (PDGF), and some cells were also positive for tumor necrosis factor (TNF) ?. Based on these findings, it was inferred that the PDGF and TNF? produced by DLBCL cells induced fibroblastic proliferation. The resultant conspicuous fibrosis caused interfibrous impingement on the DLBCL cells, which deformed them into a spindle shape. The present case is the first reported case of a PDGF-producing Sp-DLBCL. PMID:25120823

Sugimoto, Kei-Ji; Shimada, Asami; Ichikawa, Kunimoto; Wakabayashi, Mutsumi; Sekiguchi, Yasunobu; Izumi, Hiroshi; Ota, Yasunori; Komatsu, Norio; Noguchi, Masaaki

2014-01-01

191

ISABELLE cavity gap assemblies  

SciTech Connect

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

Plotkin, M

1981-01-01

192

Video Toroid Cavity Imager  

DOEpatents

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.

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

2004-08-10

193

Third-generation cylindrical diffusers for medical use  

Microsoft Academic Search

Cylindrical light diffusion is a key element in a variety of medical applications which require the controlled administration of light to a treatment site within the body. Applications such as photodynamic therapy (PDT), laser induced hyperthermia (LHT), and photoatherolytic (PAL) therapy may all require that light be diffused in this manner. Cylindrical diffusers are typically used in tubular cavities, such

A. Charles Lytle; Hugh L. Narciso; David V. Spain; Daniel R. Doiron

1993-01-01

194

The auroral plasma cavity  

NASA Technical Reports Server (NTRS)

A region of diminished plasma density has been found to occur at the source of auroral kilometric radiation (AKR). The density within this auroral plasma cavity, determined from limited Hawkeye wave data, was less than 1/cu cm from 1.8 to 3 earth radii geocentric, at 70 deg + or - 3 deg invariant magnetic latitude. The altitude variation of the magnetic field produces a minimum in the ratio of plasma frequency to cyclotron frequency within the cavity which accounts for the observed spectrum of AKR.

Calvert, W.

1981-01-01

195

Coupled Geomechanical Simulations of UCG Cavity Evolution  

SciTech Connect

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.

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

2009-07-13

196

Precision tunable resonant microwave cavity  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

197

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

E-print Network

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.

Mathews, W G

2007-01-01

198

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

E-print Network

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.

W. G. Mathews; F. Brighenti

2007-01-24

199

Creation of X-Ray Cavities in Galaxy Clusters with Cosmic Rays  

NASA Astrophysics Data System (ADS)

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 gas dynamics 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 ?~1028 cm2 s-1 in the hot gas, very similar to values required in models of cosmic ray diffusion in the Milky Way. When ?<~1028 cm2 s-1, 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 ?0-decays can result in enhanced gamma-ray emission from the cavity walls.

Mathews, William G.; Brighenti, Fabrizio

2007-05-01

200

Quench Localization in Superconducting Radio-frequency (SRF) Cavities  

E-print Network

Fernandes, Lee Teng Intern 2009 Ramesh Adhikari Quench Localization in SRF Cavities #12;Second Sound Phenomenon in which heat is transferred as a wave rather than by diffusion. Only observed in superfluid i.e. in this case, for Helium at the temperature below 2.17K (He II) This wave is analogous to sound wave, and can

Baltisberger, Jay H.

201

Validation of Ultrasonography to Evaluate Murine Orthotopic Oral Cavity Tumors  

Microsoft Academic Search

Background: The murine orthotopic oral cavity tumor model allows evaluation of tumor growth and invasion. Currently, serial measurements of tissue growth are difficult to obtain since invasive procedures or animal sacrifice is necessary to evaluate tumor size. High-resolution ultrasound was evaluated as a noninvasive method to monitor tumor size in vivo. Methods: Sixteen immunodeficient mice, age 9 weeks, were injected

John C. Pezold; Kurt Zinn; Melissa A. Talbert; Renee Desmond; Eben L. Rosenthal

2006-01-01

202

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

SciTech Connect

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.

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

2014-01-01

203

Histone acetyltransferase-deficient p300 mutants in diffuse large B cell lymphoma have altered transcriptional regulatory activities and are required for optimal cell growth  

PubMed Central

Background Recent genome-wide studies have shown that approximately 30% of diffuse large B-cell lymphoma (DLBCL) cases harbor mutations in the histone acetyltransferase (HAT) coactivators p300 or CBP. The majority of these mutations reduce or eliminate the catalytic HAT activity. We previously demonstrated that the human DLBCL cell line RC-K8 expresses a C-terminally truncated, HAT-defective p300 protein (p300?C-1087), whose expression is essential for cell proliferation. Methods Using results from large-scale DLBCL studies, we have identified and characterized a second C-terminally truncated, HAT-defective p300 mutant, p300?C-820, expressed in the SUDHL2 DLBCL cell line. Properties of p300?C-820 were characterized in the SUDHL2 DLBCL cell line by Western blotting, co-immunoprecipitation, and shRNA gene knockdown, as well by using cDNA expression vectors for p300?C-820 in pull-down assays, transcriptional reporter assays, and immunofluorescence experiments. A mass spectrometry-based method was used to compare the histone acetylation profile of DLBCL cell lines expressing various levels of wild-type p300. Results We show that the SUDHL2 cell line expresses a C-terminally truncated, HAT-defective form of p300 (p300?C-820), but no wild-type p300. The p300?C-820 protein has a wild-type ability to localize to subnuclear speckles, but has a reduced ability to enhance transactivation by transcription factor REL. Knockdown of p300?C-820 in SUDHL2 cells reduced their proliferation and soft agar colony-forming ability. In RC-K8 cells, knockdown of p300?C-1087 resulted in increased expression of mRNA and protein for REL target genes A20 and I?B?, two genes that have been shown to limit the growth of RC-K8 cells when overexpressed. Among a panel of B-lymphoma cell lines, low-level expression of full-length p300 protein, which is characteristic of the SUDHL2 and RC-K8 cells, was associated with decreased acetylation of histone H3 at lysines 14 and 18. Conclusions The high prevalence of p300 mutations in DLBCL suggests that HAT-deficient p300 activity defines a subtype of DLBCL, which we have investigated using human DLBCL cell lines RC-K8 and SUDHL2. Our results suggest that truncated p300 proteins contribute to DLBCL cell growth by affecting the expression of specific genes, perhaps through a mechanism that involves alterations in global histone acetylation. PMID:24529102

2014-01-01

204

Progress towards cavity induced transparency  

E-print Network

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

Li, Tracy (Tracy Yang)

2010-01-01

205

Broadband cavity electromagnetically induced transparency  

SciTech Connect

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.

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

2011-10-15

206

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)

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.

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

2013-12-01

207

Polychromatic Photonic Quasicrystal Cavities  

NASA Astrophysics Data System (ADS)

Photonic crystal slabs provide unique opportunities for the manipulation of light on semiconductor chips. The patterns of holes in the slabs are typically designed to maximize the width, depth and symmetry of a single photonic band gap. Quasicrystalline patterns are ideal from this point of view; here, we show that, owing to the presence of multiple Bragg scattering length scales, they also have the desirable property of supporting multiple photonic band gaps in the same slab. This opens up the possibility of creating polychromatic cavities that could be used to extend the possibilities for single photons on optical chips, including on-chip frequency conversion in III-V semiconductors. We study several quasicrystalline structures which support high quality cavity modes at multiple resonant frequencies using 2D and 3D FDTD simulations.

Thon, Susanna M.; Irvine, William T. M.; Kleckner, Dustin; Bouwmeester, Dirk

2010-06-01

208

Polychromatic photonic quasicrystal cavities.  

PubMed

Photonic crystal slabs provide unique opportunities for the manipulation of light on semiconductor chips. The patterns of holes in the slabs are typically designed to maximize the width, depth and symmetry of a single photonic band gap. Quasicrystalline patterns are ideal from this point of view; here, we show that, owing to the presence of multiple Bragg scattering length scales, they also have the desirable property of supporting multiple photonic band gaps in the same slab. This opens up the possibility of creating polychromatic cavities that could be used to extend the possibilities for single photons on optical chips, including on-chip frequency conversion in III-V semiconductors. We study several quasicrystalline structures which support high quality cavity modes at multiple resonant frequencies using 2D and 3DFDTD simulations. PMID:20867302

Thon, Susanna M; Irvine, William T M; Kleckner, Dustin; Bouwmeester, Dirk

2010-06-18

209

Water clusters in nonpolar cavities  

PubMed Central

We explore the structure and thermodynamics of water clusters confined in nonpolar cavities. By calculating the grand-canonical partition function term by term, we show that small nonpolar cavities can be filled at equilibrium with highly structured water clusters. The structural and thermodynamic properties of these encapsulated water clusters are similar to those observed experimentally in the gas phase. Water filling is highly sensitive to the size of the cavity and the strength of the interactions with the cavity wall. Water penetration into pores can thus be modulated by small changes in the polarity and structure of the cavity. Implications on water penetration into proteins are discussed. PMID:15572444

Vaitheeswaran, Subramanian; Yin, Hao; Rasaiah, Jayendran C.; Hummer, Gerhard

2004-01-01

210

Oral Cavity Surgery Codes  

Cancer.gov

Oral Cavity Lip C000C009, Base of Tongue C019, Other Parts of Tongue C020C029, Gum C030C039, Floor of Mouth C040C049, Palate C050C059, Other Parts of Mouth C060C069 (Except for M9727, 9733, 9741-9742, 9764-9809, 9832, 9840-9931, 9945-9946, 9950-9967,

211

Crab Cavities for Linear Colliders  

SciTech Connect

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

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

2011-11-08

212

Interaction of cavities with misfit dislocations in SiGe/Si heterostructures  

SciTech Connect

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.

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

1996-09-01

213

Diffusion Limited Aggregation  

NSDL National Science Digital Library

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

Joiner, David; The Shodor Education Foundation, Inc.

214

Effect of substrate dislocations on the Hg in-diffusion in CdZnTe substrates used for HgCdTe epilayer growth  

Microsoft Academic Search

Chemical-etched HgCdTe epilayers grown onto CdZnTe substrates have been studied using defect etching and EDS on cleaved (110) face. Formation of etch pits and mercury (Hg) in-diffusion into CZT substrate has been correlated with the substrate quality i.e. the presence of dislocations around second phase inclusions. That the Hg in-diffusion takes place through these dislocations is authenticated by the presence

Shiv Kumar; A. K. Kapoor; A. Nagpal; S. Sharma; D. Verma; A. Kumar; R. Raman; P. K. Basu

2006-01-01

215

Effect of H and He Irradiation on Cavity Formation and Blistering in Ceramics  

SciTech Connect

Single- or poly-crystalline specimens of SiC, Si{sub 3}N{sub 4}, MgO, Al{sub 2}O{sub 3} and MgAl{sub 2}O{sub 4} were implanted with 0.4-1 MeV H{sup +} or He{sup +} ion beams at room temperature and 650 C up to fluences of {approx}1 x 10{sup 22}/m{sup 2}. This produced peak implanted gas and displacement damage levels as high as {approx}50 at.% and 34 displacements per atom (dpa). The specimens were subsequently examined optically, and in cross-section using transmission electron microscopy. Subsurface blistering occurred for specimens irradiated to H or He fluences greater than about 3 x 10{sup 21}/m{sup 2} ({approx}15 at.% peak implanted gas concentration), and surface exfoliation occurred for fluences above {approx}1 x 10{sup 22}/m{sup 2} ({approx}40 at.% implanted gas). Both helium and hydrogen had comparable effectiveness for inducing blistering and exfoliation on an atomic basis. The threshold blistering and exfoliation fluences for both ions were weakly dependent on temperature between 25 and 650 C. Both H and He were found to be very effective in inducing matrix cavity formation, due to their low solubility in these ceramics. The implanted gas concentrations that resulted in visible cavity formation generally ranged from 1 to 5 at.%. Visible cavity formation was readily induced during room temperature irradiation despite the limited vacancy mobility in these ceramics at room temperature. Three general types of cavity morphologies were observed: isolated cavities, clusters of small cavities (typically associated with dislocation loops), and two-dimensional platelets. Cavity formation was observed to initiate at the periphery of dislocation loops in some cases. During elevated temperature irradiation, cavity formation was often observed to be preferentially associated with certain low-index habit planes, particularly if the habit plane was oriented nearly parallel to the irradiated surface: (0001) and {l_brace}1{bar 1}00{r_brace} for Al{sub 2}O{sub 3}, (0001) for a-SiC, {l_brace}001{r_brace} and {l_brace}110{r_brace} for MgO, and {l_brace}110{r_brace} and {l_brace}111{r_brace} for MgAl{sub 2}O{sub 4}. The bubble formation and blistering behavior of the ceramics was similar to that observed in other studies of metals irradiated at comparable homologous temperatures. Ionization-induced diffusion effects associated with dual-beam light ion irradiation appeared to exert only a weak effect on cavity and dislocation loop growth compared to the single ion irradiation conditions.

Zinkle, Steven J [ORNL] [ORNL

2012-01-01

216

Superconducting Radio-Frequency Cavities  

NASA Astrophysics Data System (ADS)

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

Padamsee, Hasan S.

2014-10-01

217

Nasal Cavity and Paranasal Sinuses  

Microsoft Academic Search

\\u000a Included in this chapter are nasal cavities, frontal sinus, ethmoid complex, sphenoid sinus, and maxillary sinuses. These\\u000a cavities and sinuses are lined by Schneiderian mucosa, consisting of pseudostratified columnar ciliated epithelium with interspersed\\u000a goblet cells. The roof of the nasal cavity is the cribriform plate, specific location for olfactory neuroblastoma. The sinonasal\\u000a Schneiderian (inverted type) papilloma appears to be a

Qihui Jim Zhai

218

Multicolor cavity metrology.  

PubMed

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

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

219

Applications of cavity optomechanics  

NASA Astrophysics Data System (ADS)

"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.

Metcalfe, Michael

2014-09-01

220

Anomalous Diffusion Near Resonances  

SciTech Connect

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.

Sen, Tanaji; /Fermilab

2010-05-01

221

A Casimir cannot cavity fly  

E-print Network

A recent theoretical analysis shows that is it impossible for a Casimir cavity to be of such a small mass, that the negative energy of the electromagnetic vacuum would give it a zero or negative total mass. We present a simple gedanken experiment with a plane parallel cavity with metallic plates, kept in mechanical equilibrium by a spring, and placed in a weak gravitational field. We assume only Special Relativity, Equivalence Principle and conservation of local energy. We show that indeed such a cavity cannot fly on first principles, giving sort of experimental demonstration of the theory of ref. A brief discussion is given about Casimir cavities weighing the vacuum.

Massimo Cerdonio; Carlo Rovelli

2014-06-04

222

Dewetting Transitions in Protein Cavities *  

PubMed Central

In a previous analysis of the solvation of protein active sites, a drying transition was observed in the narrow hydrophobic binding cavity of Cox-2. With the use of a crude metric that often seems able to discriminate those protein cavities that dry from those that do not, we made an extensive search of the pdb, and identified five other proteins that, in molecular dynamics simulations, undergo drying transitions in their active sites. Because such cavities need not desolvate before binding hydrophobic ligands they often exhibit very large binding affinities. This paper gives evidence that drying in protein cavities is not unique to Cox-2. PMID:20225258

Young, Tom; Hua, Lan; Huang, Xuhui; Abel, Robert; Friesner, Richard; Berne, B. J.

2010-01-01

223

Impact of mesophyll diffusion on estimated global land CO2 fertilization.  

PubMed

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

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

2014-11-01

224

Between Scylla and Charybdis: Hydrophobic Graphene-Guided Water Diffusion on Hydrophilic Substrates  

PubMed Central

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

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

225

Cavity-actuated supersonic mixing and combustion control  

SciTech Connect

Compressible shear layers in supersonic jets are quite stable and spread very slowly compared with incompressible shear layers. In this paper, a novel use of a cavity-actuated forcing technique is demonstrated for increasing the spreading rate of compressible shear layers. Periodic modulations were applied to Mach 2.0 reacting and nonreacting jets using the cavities that were attached at the exit of a circular supersonic nozzle. The effect of cavity-actuated forcing was studied as a function of the cavity geometry, in particular, the length and the depth of the cavity. When the cavities were tuned to certain frequencies, large-scale highly coherent structures were produced in the shear layers substantially increasing the growth rate. The cavity excitation was successfully applied to both cold and hot supersonic jets. When applied to cold Mach 2.0 air jets. the cavity-actuated forcing increased the spreading rate of the initial shear layers with the convective Mach number (M[sub C]) of 0.85 by a factor of three. For high-temperature Mach 2.0 jets with M[sub C] of 1.4, a 50% increase in the spreading rate was observed with the forcing. Finally, the cavity-actuated forcing was applied to reacting supersonic jets with ethylene-oxygen afterburning. For this case, the forcing caused a 20%--30% reduction in the afterburning flame length and modified the afterburning intensity significantly. The direction of the modification depended on the characteristics of the afterburning flames. The intensity was reduced with forcing for unstable flames with weak afterburning while it was increased for stable flames with strong afterburning.

Yu, K.H.; Schadow, K.C. (Naval Air Warfare Center, China Lake, CA (United States). Research Dept.)

1994-11-01

226

Hillslope diffusion  

NSDL National Science Digital Library

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

Mcdermott, Jeni

227

FORWARD MODELING CAVITY DENSITY: A MULTI-INSTRUMENT DIAGNOSTIC  

SciTech Connect

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

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

2011-05-20

228

A Rare Tumor of Nasal Cavity: Glomangiopericytoma  

PubMed Central

Glomangiopericytoma is a rare vascular neoplasm characterized by a pattern of prominent perivascular growth. A 72-year-old woman was admitted to our clinic complaining of nasal obstruction, frequent epistaxis, and facial pain. A reddish tumor filling the left nasal cavity was observed on endoscopy and treated with endoscopic excision. Microscopically, closely packed cells interspersed with numerous thin-walled, branching staghorn vessels were seen. Glomangiopericytoma is categorized as a borderline low malignancy tumor by WHO classification. Long-term follow-up with systemic examination is necessary due to high risk of recurrence. PMID:25143851

Verim, Aysegul; Karaca, Cigdem Tepe; Gunes, Pembegul; Sheidaei, Shahrouz; Oysu, Cagatay

2014-01-01

229

A rare tumor of nasal cavity: glomangiopericytoma.  

PubMed

Glomangiopericytoma is a rare vascular neoplasm characterized by a pattern of prominent perivascular growth. A 72-year-old woman was admitted to our clinic complaining of nasal obstruction, frequent epistaxis, and facial pain. A reddish tumor filling the left nasal cavity was observed on endoscopy and treated with endoscopic excision. Microscopically, closely packed cells interspersed with numerous thin-walled, branching staghorn vessels were seen. Glomangiopericytoma is categorized as a borderline low malignancy tumor by WHO classification. Long-term follow-up with systemic examination is necessary due to high risk of recurrence. PMID:25143851

Verim, Aysegul; Kalaycik Ertugay, Cigdem; Karaca, Cigdem Tepe; Gunes, Pembegul; Sheidaei, Shahrouz; Oysu, Cagatay

2014-01-01

230

Quench studies of ILC cavities  

SciTech Connect

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.

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

2011-07-01

231

Effect of magnetopause leakage on the lifetime of magnetospheric cavity modes  

Microsoft Academic Search

Magnetospheric cavity modes can decay through various loss processes. Energy leakage across the magnetopause is one such process that is commonly neglected. Here we consider what the actual effect of the neglected magnetopause leakage might be on cavity mode lifetime and hence on coupled transverse mode wave growth. First, we review the linear theory of fast mode wave reflection at

M. P. Freeman

2000-01-01

232

Small cell carcinoma of the oral cavity: report of a rare case.  

PubMed

Small cell carcinoma is primarily a lung malignancy occurring rarely in extra pulmonary sites such as the larynx, nasal cavity, paranasal sinuses, and oral cavity. The authors report a rare case of primary small cell carcinoma of the maxillary sinus presenting as a growth of the alveolus extending into the hard palate and the buccal vestibule. PMID:19831016

Shenoy, Nandita; Sholapurkar, Amar A; Pai, Keerthilatha M; Pal, Kanthilatha

2009-06-01

233

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

234

Diffusion of spherical particles in microcavities  

E-print Network

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.

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

2011-03-25

235

Transition to a superconductor with insulating cavities  

NASA Astrophysics Data System (ADS)

An extreme type-II superconductor with internal insulating regions, namely cavities, is studied here. We find that the cavity-bearing superconductor has lower energy than the defect-free superconductor above a critical magnetic induction B* for insulating cavities but not for metallic ones. Using a numerical approach for the Ginzburg-Landau theory, we compute and compare free energy densities for several cavity radii and at least for two cavity densities, assuming a cubic lattice of spherical cavities.

Doria, M. M.; Romaguera, A. R. de C.

2004-08-01

236

Growth of InGaAs\\/AlAsSb single quantum wells with various AlAs diffusion-stopping layers  

Microsoft Academic Search

We have grown InGaAs\\/AlAsSb single quantum wells (SQWs) with AlAs diffusion-stopping layers of various thicknesses by molecular beam epitaxy. X-ray diffraction rocking curve measurements as well as optical microscope observations indicated good structural quality of the samples having less than 4-monolayer (ML) AlAs layers, which were inserted between InGaAs wells and AlAsSb barriers. Near-infrared absorption measurements revealed that when only

J. Kasai; T. Mozume

2005-01-01

237

Combined Diffusion and Perfusion MRI With Correlation to Single-Photon Emission CT in Acute Ischemic Stroke Ischemic Penumbra Predicts Infarct Growth  

Microsoft Academic Search

Background and PurposeMore effective imaging methods are needed to overcome the limitations of CT in the investigation of treatments for acute ischemic stroke. Diffusion-weighted MRI (DWI) is sensitive in detecting infarcted brain tissue, whereas perfusion-weighted MRI (PWI) can detect brain perfusion in the same imaging session. Combining these methods may help in identifying the ischemic penumbra, which is an important

Jari O. Karonen; Ritva L. Vanninen; Yawu Liu; Leif stergaard; Jyrki T. Kuikka; Juho Nuutinen; Esko J. Vanninen; P. L. Kaarina Partanen; Pauli A. Vainio; Katja Korhonen; Jussi Perkio; Reina Roivainen; Juhani Sivenius; Hannu J. Aronen

238

Enhanced diffusion welding  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

239

Hopf bifurcation in the driven cavity  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

240

Observing quantum phenomena in cavity optomechanics  

NASA Astrophysics Data System (ADS)

Recent efforts have produced optomechanical systems whose mechanical elements are prepared at or near their quantum ground state. But what manifestly quantum effects can be measured with these new systems? Here we present results from our experiment, using the collective motion of an ultracold atom ensemble as a mechanical oscillator. The motion is driven by shot noise in the light's radiation pressure, allowing us to observe the production of nonclassical states of light by optomechanics -- here, quadrature-squeezed light. Notably, this nonlinear optical effect occurs with only 40 pW of pump power. We also measure the quantization of the oscillator, by observing a 3:1 asymmetry in the light it scatters to low- and high-energy optical sidebands. Analyzing the light emitted from the cavity moreover provides a spectroscopic record of the energy exchanged between light and motion, allowing us to directly quantify the necessary diffusive heating of a quantum backaction-limited position measurement.

Brahms, Nathaniel; Brooks, Dan W. C.; Schreppler, Sydney; Botter, Thierry; Stamper-Kurn, Dan M.

2012-02-01

241

Modeling of oxide-confined vertical-cavity surface-emitting lasers  

Microsoft Academic Search

We present a quasi-three-dimensional (quasi-3-D) model of vertical-cavity surface-emitting lasers (VCSELs) using a finite difference beam propagation method (BPM) scheme. The electrical model is based on the carrier rate equation including carrier diffusion. This model, which gives an accurate optical description of the cavity, calculates the threshold current, laser wavelength, output power and secondary-mode rejection of any index or gain-guided

Hans K. Bissessur; Fumio Koyama; Kenichi Iga

1997-01-01

242

Microwave cavity search for paraphotons  

SciTech Connect

In this proceeding we report the first results of a microwave cavity search for hidden sector photons. Using a pair of isolated resonant cavities we look for 'light shining through a wall' from photon--hidden sector photon oscillations. Our prototype experiment consists of two cylindrical, copper cavities stacked axially inside a single vacuum chamber. At a hidden sector photon mass of 39.58 mueV we place an upper limit on the kinetic mixing parameter chi at 7.8x10{sup -6}. Whilst this result is inside already established limits our experiment has great scope for improvement.

Povey, Rhys; Hartnett, John; Tobar, Michael [School of Physics, University of Western Australia, 35 Stirling Hwy, Crawley 6009 WA (Australia)

2010-06-15

243

Novel Crab Cavity RF Design  

SciTech Connect

A 20-50 MV integrated transverse voltage is required for the Electron-Ion Collider. The most promising of the crab cavity designs that have been proposed in the last five years are the TEM type crab cavities because of the higher transverse impedance. The TEM design approach is extended here to a hybrid crab cavity that includes the input power coupler as an integral part of the design. A prototype was built with Phase I monies and tested at JLAB. The results reported on, and a system for achieving 20-50 MV is proposed.

Dudas, A. [Muons, Inc., Batavia, IL (United States); Neubauer, M. L. [Muons, Inc., Batavia, IL (United States); Sah, R. [Muons, Inc., Batavia, IL (United States); Rimmer, B. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Wang, H. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

2011-03-01

244

Call for Papers: Cavity QED  

NASA Astrophysics Data System (ADS)

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.

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

2003-06-01

245

Shape Determination for Deformed Cavities  

SciTech Connect

A realistic superconducting RF cavity has its shape deformed comparing to its designed shape due to the loose tolerance in the fabrication process and the frequency tuning for its accelerating mode. A PDE-constrained optimization problem is proposed to determine the deformation of the cavity. A reduce space method is used to solve the PDE-constrained optimization problem where design sensitivities were computed using a continuous adjoint approach. A proof-of-concept example is given in which the deformation parameters of a single cavity-cell with two different types of deformation were computed.

Lee, Lie-Quan; Akcelik, Volkan; Chen, Sheng; Ge, Lixin; Li, Zenghai; Ng, Cho; Xiao, Liling; Ko, Kwok; /SLAC; Ghattas, Omar; /Texas U.

2006-10-04

246

Nonlocal Intracranial Cavity Extraction  

PubMed Central

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

Manjon, Jose V.; Eskildsen, Simon F.; Coupe, Pierrick; Romero, Jose E.; Collins, D. Louis; Robles, Montserrat

2014-01-01

247

Catellibacterium nectariphilum gen. nov., sp. nov., which requires a diffusible compound from a strain related to the genus Sphingomonas for vigorous growth.  

PubMed

A bacterial strain, designated AST4(T), was isolated from activated sludge. The bacterium did not show significant growth on nutrient broth, but growth was clearly stimulated by addition of supernatant from other bacterial cultures. Culture filtrate of a strain related to the genus Sphingomonas in particular increased the cell yield and growth rate of strain AST4(T). Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain AST4(T) is located within the 'Rhodobacter group' in the alpha-3 subclass of Proteobacteria, but is clearly distant from related genera in this group such as Paracoccus, Rhodobacter and Rhodovulum. Strain AST4(T) is a Gram-negative, non-motile, rod-shaped (0.6-0.8x1.3-2.0 micro m) and aerobic bacterium. It was not able to reduce nitrate to nitrite or N(2). No phototrophic growth was observed. Optimal growth occurred at 30 degrees C and pH 6.5-7.5. The dominant cellular fatty acid in the isolate was C(18 : 1)cis11. Ubiquinone-10 was the major respiratory quinone. The G+C content was 64.5 mol% (by HPLC). Based on the phylogenetic and phenotypic traits, the name Catellibacterium nectariphilum gen. nov., sp. nov. is proposed for this isolate; the type strain is AST4(T) (=NBRC 100046(T)=JCM 11959(T)=DSM 15620(T)). PMID:15143049

Tanaka, Yasuhiro; Hanada, Satoshi; Manome, Akira; Tsuchida, Takayasu; Kurane, Ryuichiro; Nakamura, Kazunori; Kamagata, Yoichi

2004-05-01

248

Auroral kilometric radiation from a nonstationary thin plasma cavity  

NASA Astrophysics Data System (ADS)

Results obtained using a waveguide model of the AKR generation in thin plasma cavities are presented. Taking into account the occurrence of low frequency plasma motion in the regions of the AKR generation, we have considered a wave escape from a thin plasma cavity with adiabatically slowly varying width, and show that there can exist localized regions of instability from which the extraordinary X-mode waves, growing in time, can be radiated outwards. It has been found that waves, propagating quasi-tangentially to the source frontiers, have the maximum growth rate and escape outward most efficiently, which is in accordance with experimental observations.

Burinskaya, T. M.; Rauch, J.-L.

2012-07-01

249

Cooling of a $\\Lambda$-type three-level atom in a high finesse optical cavity  

E-print Network

A theoretical study is carried out for the cavity cooling of a $\\Lambda$-type three level atom in a high-finesse optical cavity with a weakly driven field. Analytical expressions for the friction, diffusion coefficients and the equilibrium temperatures are obtained by using the Heisenberg equations, then they are calculated numerically and shown graphically as a function of controlling parameters. For a suitable choice of these parameters, the dynamics of the cavity field interaction with the $\\Lambda$-type three-level atom introduces a sisyphus cooling mechanism yielding lower temperatures below the Doppler limit and allowing larger cooling rate, avoiding the problems induced by spontaneous emission.

Tan, Lei; Sun, Yan-Fen

2010-01-01

250

Design of rf conditioner cavities  

SciTech Connect

Theoretical studies are made of radio frequency structures which can be used to condition electron beams so as to greatly reduce the stringent emittance requirements for successful lasing in a free-electron laser. The basic strategy of conditioning calls for modulating an electron beam in the transverse dimension, by a periodic focusing channel, while it traverses a series of rf cavities, each operating in a TM{sub 210} mode. In this paper, we analyze the cavities both analytically and numerically (using MAFIA simulations). We find that when cylindrical symmetry is broken the coupling impedance can be greatly enhanced. We present results showing various performance characteristics as a function of cavity parameters, as well as possible designs for conditioning cavities.

Govil, R.; Rimmer, R.A.; Sessler, A.; Kirk, H.G.

1992-06-01

251

Diffuser Test  

NASA Technical Reports Server (NTRS)

Tests begun at Stennis Space Center's E Complex Sept. 13 evaluated a liquid oxygen lead for engine start performance, part of the A-3 Test Facility Subscale Diffuser Risk Mitigation Project at SSC's E-3 Test Facility. Phase 1 of the subscale diffuser project, completed Sept. 24, was a series of 18 hot-fire tests using a 1,000-pound liquid oxygen and gaseous hydrogen thruster to verify maximum duration and repeatability for steam generation supporting the A-3 Test Stand project. The thruster is a stand-in for NASA's developing J-2X engine, to validate a 6 percent scale version of A-3's exhaust diffuser. Testing the J-2X at altitude conditions requires an enormous diffuser. Engineers will generate nearly 4,600 pounds per second of steam to reduce pressure inside A-3's test cell to simulate altitude conditions. A-3's exhaust diffuser has to be able to withstand regulated pressure, temperatures and the safe discharge of the steam produced during those tests. Before the real thing is built, engineers hope to work out any issues on the miniature version. Phase 2 testing is scheduled to begin this month.

2007-01-01

252

Human capital and technology diffusion  

Microsoft Academic Search

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

Jess Benhabib; Mark M. Spiegel

2002-01-01

253

Theory of Bloch cavity solitons  

SciTech Connect

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.

Egorov, O. A.; Lederer, F. [Institute of Condensed Matter Theory and Solid State Optics, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany); Staliunas, K. [Instituci Catalana de Recerca i Estudis Avanats (ICREA), Departament de Fisica i Enginyeria Nuclear, Universitat Politcnica de Catalunya, Colom 11, E-08222 Terrassa (Spain)

2010-10-15

254

Diffusion on Cu surfaces  

NASA Technical Reports Server (NTRS)

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.

Karimi, Majid

1993-01-01

255

Sequential cavity use in a cottonwood bottomland  

USGS Publications Warehouse

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.

Sedgwick, J. A.

1997-01-01

256

Tem observations of crack tip Cavity interactions  

NASA Astrophysics Data System (ADS)

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

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

257

Insight of Iron Whisker Sticking Mechanism from Iron Atom Diffusion and Calculation of Solid Bridge Radius  

NASA Astrophysics Data System (ADS)

The sticking temperatures of three kinds of iron particles with different morphologies were examined at an inert atmosphere in a fluidized bed, indicating that the sticking temperature of a fresh reduction iron particle was lower than that of reagent iron particles, and that the sticking temperature of an iron particle with a whisker was lower than that of an iron particle without a whisker. Cavity defects on the surface of an iron particle with different morphologies were examined by positron annihilation spectroscopy. The results indicated that cavity defects on the surface of an iron particle with an iron whisker were higher than with others, which resulted in an easier surface diffusion of Fe atoms. From the calculation of a critical solid bridge radius, the critical solid bridge radius lowered with the decreasing of gas velocity and particle size. And when an instantaneous solid bridge radius was bigger than a critical solid bridge radius, sticking of the iron particle happened. The iron whisker made the surface diffusion rate of Fe atoms occur more quickly, which resulted in a faster growth rate of the instantaneous solid bridge radius. Therefore, the iron whisker supported the sticking.

Gong, Xuzhong; Zhang, Ben; Wang, Zhi; Guo, Zhancheng

2014-07-01

258

Demonstrating Diffusion  

ERIC Educational Resources Information Center

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)

Foy, Barry G.

1977-01-01

259

Diffusion Models  

NSDL National Science Digital Library

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

Sharov, Alexei

260

The relationship between transplacental O2 diffusion and placental expression of PlGF, VEGF and their receptors in a placental insufficiency model of fetal growth restriction  

PubMed Central

Placental growth factor (PlGF) and vascular endothelial growth factor (VEGF) are involved in placental angiogenesis through interactions with the VEGFR-1 and VEGFR-2 receptors. The placenta of pregnancies whose outcome is fetal growth restriction (FGR) are characterized by abnormal angiogenic development, classically associated with hypoxia. The present study evaluated the near-term expression of this growth factor family in an ovine model of placental insufficiencyFGR, in relationship to uteroplacental oxygenation. Compared to controls, FGR pregnancies demonstrated a 37 % increase in uterine blood flow (FGR vs. control, 610.86 48.48 vs. 443.17 37.39 ml min?1 (kg fetus)?1; P < 0.04), which was associated with an increased maternal uterine venous PO2 (58.13 1.00 vs. 52.89 1.26 mmHg; P < 0.02), increased umbilical artery systolic/diastolic ratio (3.90 0.33 vs. 2.12 0.26, P < 0.05), and fetal hypoxia (arterial PO2; 12.79 0.97 vs. 18.65 1.6 mmHg, P < 0.005). Maternal caruncle PlGF mRNA was increased in FGR (P < 0.02), while fetal cotyledon VEGF mRNA was reduced (P < 0.02). VEGFR-1 mRNA was also reduced in FGR fetal cotyledon (P < 0.001) but was not altered in caruncle tissue. Immunoblot analysis of PlGF and VEGF demonstrated single bands at 19 000 and 18 600 Mr, respectively. Caruncle PlGF concentration was increased (P < 0.04), while cotyledon VEGF was decreased (P < 0.05) in FGR placentae. The data establish that uterine blood flow is not reduced in relationship to metabolic demands in this FGR model and that the transplacental PO2 gradient is increased, maintaining umbilical oxygen uptake per unit of tissue. Furthermore, these data suggest that an increased transplacental gradient of oxygen generates changes in angiogenic growth factors, which may underline the pathophysiology of the post-placental hypoxic FGR. PMID:12740423

Regnault, Timothy R H; de Vrijer, Barbra; Galan, Henry L; Davidsen, Meredith L; Trembler, Karen A; Battaglia, Frederick C; Wilkening, Randall B; Anthony, Russell V

2003-01-01

261

The ESS elliptical cavity cryomodules  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

262

The ESS spoke cavity cryomodules  

NASA Astrophysics Data System (ADS)

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.

Bousson, Sebastien; Darve, Christine; Duthil, Patxi; Elias, Nuno; Molloy, Steve; Reynet, Denis; Thermeau, Jean-Pierre

2014-01-01

263

The Superconducting Cavity Stabilized Oscillator  

NASA Technical Reports Server (NTRS)

Superconducting Cavity Stabilized Oscillators (SCSOs) have produced the most stable clocks to date for integration times between 10(exp 2) and 10(exp 3) seconds, achieving a fractional frequency stability of 2 x 10(exp -16) for a sampling time of 100 s. The principal contributors to cavity frequency variations are: (1) acceleration effects due to gravity and vibrations; (2) temperature variations; (3) variations in the energy stored in the cavity; and (4) noise introduced by the frequency stabilization circuit. We discuss the prospects for improvements in all these areas for both ground-based and space-based SCSOs, which may lead to SCSOs with fractional frequency stabilities below 10(exp -17). SCSOs of this frequency stability will be useful for testing fundamental physical principles.

Turneaure, J. P.; Buchman, Saps; Lipa, John

1997-01-01

264

Holographic Graphene in a Cavity  

E-print Network

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

Evans, Nick

2014-01-01

265

Holographic Graphene in a Cavity  

E-print Network

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

Nick Evans; Peter A. R. Jones

2014-07-11

266

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

PubMed Central

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

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

2013-01-01

267

Diffusive Dynamics of Interacting Particles in Equilibrium and under Hydrodynamic Sedimentation.  

National Technical Information Service (NTIS)

Diffusive motion of particles plays an important role in phenomena in surface physics, for example in chemical reactions, surface growth, and spreading. Diffusive motion can be observed in many different systems. In this thesis the authors study diffusion...

J. M. Lahtinen

2002-01-01

268

Dissipative structures in optomechanical cavities  

E-print Network

We analyze the possibility of pattern formation in an optical cavity in which one of its mirrors can be deformed by radiation pressure. Our model treats the deformable mirror as tense membrane that can oscillate, not only back and forth around its axial equilibrium position (center of mass motion), but also in its transverse degrees of freedom, vibrating like a drum in combinations of modes. We demonstrate the existence of periodic patterns and localized structures (cavity solitons) in this model, which should be realizable with current technology.

Joaqun Ruiz-Rivas; Carlos Navarrete-Benlloch; Giuseppe Patera; Eugenio Roldn; Germn J. de Valcrcel

2012-12-06

269

Cavity-QED enhancement of fluorescence yields in microdroplets  

SciTech Connect

Measurements of the integrated fluorescence yield of Rhodamine 6G (R6G) in levitated microdroplets (4 to 16 {mu}m diameter) display a size dependence which is attributed to a decreased probability per excitation cycle of photochemical bleaching as a result of cavity-enhanced spontaneous emission rates. The average number of fluorescence photons detected per molecule in 4 {mu}m droplets (where emission rate enhancement has been previously demonstrated) is shown to be approximately a factor of 2 larger than the yield measured for larger droplets where emission rate enhancement does not occur. Within some simple approximations, these results suggest that essentially no emission rate inhibition occurs in this system. A mechanism based on spectral diffusion is postulated for the apparent absence of cavity-inhibited emission and is illustrated by Monte Carlo calculations using time-dependent lineshape functions.

Barnes, M.D.; Whitten, W.B.; Ramsey, J.M. [Oak Ridge National Lab., TN (United States). Analytical Chemistry Div.

1993-12-31

270

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

PubMed

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 160kHz due to the slow light effect. The linewidth of the SLC fiber laser was measured to be less than 600Hz. PMID:25361093

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

2014-10-15

271

Progress on a Be Cavity Design  

SciTech Connect

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.

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

2010-12-24

272

Analog detection for cavity lifetime spectroscopy  

DOEpatents

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.

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

273

Analog detection for cavity lifetime spectroscopy  

DOEpatents

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.

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

274

Diffusion via space discretization method to study the concentration dependence of self-diffusivity under confinement.  

PubMed

The concentration dependence of self-diffusivity is investigated by means of a novel method, extending our previously developed second-order Markov process model to periodic media. Introducing the concept of minimum-crossing surface, we obtain a unique decomposition of the self-diffusion coefficient into two parameters with specific physical meanings. Two case studies showing a maximum in self-diffusivity as a function of concentration are investigated, along with two cases where such a maximum cannot be present. Subsequently, the method is applied to the large cavity pore network of the ITQ-1 (Mobil tWenty tWo, MWW) zeolite for methane (displaying a maximum in self-diffusivity) and carbon dioxide (no maximum), explaining the diffusivity trend on the basis of the evolution of the model parameters as a function of concentration. PMID:20387922

Sant, Marco; Papadopoulos, George K; Theodorou, Doros N

2010-04-01

275

Diffusion via space discretization method to study the concentration dependence of self-diffusivity under confinement  

NASA Astrophysics Data System (ADS)

The concentration dependence of self-diffusivity is investigated by means of a novel method, extending our previously developed second-order Markov process model to periodic media. Introducing the concept of minimum-crossing surface, we obtain a unique decomposition of the self-diffusion coefficient into two parameters with specific physical meanings. Two case studies showing a maximum in self-diffusivity as a function of concentration are investigated, along with two cases where such a maximum cannot be present. Subsequently, the method is applied to the large cavity pore network of the ITQ-1 (Mobil tWenty tWo, MWW) zeolite for methane (displaying a maximum in self-diffusivity) and carbon dioxide (no maximum), explaining the diffusivity trend on the basis of the evolution of the model parameters as a function of concentration.

Sant, Marco; Papadopoulos, George K.; Theodorou, Doros N.

2010-04-01

276

Water vapor permeabilities through polymers: diffusivities from experiments and simulations  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

277

Diffuse interstellar bands in reflection nebulae  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

278

Cavity-QED assisted attraction between a cavity mode and an exciton mode in a planar photonic-crystal cavity.  

PubMed

The photoluminescence spectra from a quantum-dot exciton weakly-coupled to a planar photonic-crystal cavity is experimentally investigated by temperature tuning. Significant resonance shifts of the cavity mode are observed as the cavity mode spectrally approaches that of the exciton mode, showing the appearance of cavity-to-exciton attraction or mode pulling. Cavity-mode spectral shifts are also found theoretically using a master equation model that includes incoherent pump processes for the coupled exciton and cavity, pure dephasing, and allows for photon emission via radiation modes and the leaky cavity mode. Both experiments and theory show clear cavity mode spectral shifts in the photoluminescence spectra, when certain coupling parameters are met. However, discrepancies between the experimental data and theory, including more pronounced spectral shifts in the measurements, indicate that other unknown mode-pulling effects may also be occurring. PMID:20174101

Tawara, T; Kamada, H; Tanabe, T; Sogawa, T; Okamoto, H; Yao, P; Pathak, P K; Hughes, S

2010-02-01

279

Efficiently loading a single photon into a single-sided fabry-perot cavity.  

PubMed

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 shaped by an electro-optical amplitude modulator, whose time constant matches the photon lifetime in the cavity, we demonstrate a loading efficiency of (872)% from free space to a single-sided Fabry-Perot cavity. We further demonstrate directly loading heralded single Stokes photons into the cavity with an efficiency of (605)% without the electro-optical amplitude modulator and verify the time reversal between the frequency-entangled paired photons. Our result and approach may enable promising applications in realizing large-scale quantum networks based on cavity quantum electrodynamics. PMID:25302886

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

2014-09-26

280

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

Microsoft Academic Search

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

Heinrich J. Voelk; Peter L. Biermann

1988-01-01

281

Monte Carlo Modeling of a Cavity Ion Source  

NASA Astrophysics Data System (ADS)

Mass spectrometry is a powerful analytical tool, but is limited by sensitivity and precision, which are crucial for samples that contain low concentrations of the elements of interest. One way to increase this sensitivity and precision is with more efficient ion sources. Thermal ionization mass spectrometry (TIMS), which yields some of the most sensitive and precise isotope ratio data, uses Re or Ta ribbon filaments as ion sources. These generally ionize material with <1% efficiency (percent of ions counted). The cavity ion source (CIS) has recently been explored as an alternative to filaments. In contrast to flat filaments, the CIS is a hollowed Re or W rod. The CIS ionizes refractory elements with much higher efficiency than TIMS filaments. For example, filaments ionize U with ~0.1% efficiency, whereas CIS studies have reported efficiencies up to 39%. The filament and the CIS use the same mechanism to ionize material (i.e., thermal ionization), but the CIS forces the sample to interact with the ionizing surface many times by confining the evaporated sample to a cavity. The CIS is heated by electron bombardment, evaporating the sample just as it would on a filament. However, before being lost to the environment, the sample diffuses to the cavity's opening. While diffusing, the sample collides with the walls of the hot cavity hundreds or thousands of times. Each collision is an opportunity to ionize the evaporated sample atoms. Typical probabilities for ionization (per collision) for actinides are <1%, but having thousands of collisions greatly raises the final ionization efficiency. However, each ionized atom has the potential to recombine (i.e., gain an electron and become neutral) with additional collisions in the CIS. The probability of recombination is much higher than the probability of ionization for a single collision. Therefore, a critical design feature of a CIS is to ensure that ions are extracted after they form. The subject of this study is how to design a CIS to maximize ionization and minimize recombination. This work models a CIS using SIMION 7.0 to determine how the ionization efficiency (and thus ionization and recombination rate) depends on the cavity's length, radius and extraction potential. The model assumes a Re cavity held at a steady-state temperature of 2750 K, with a circular extraction electrode. The study predicts that ionization efficiency is not strongly dependent on cavity dimensions or extraction potential (as long as it is >1kV), but wider cavities and higher extraction potentials increase the cavity's efficiency, while longer cavities do not. The most efficient CIS modeled had a length of ~3cm and an inner radius ~5mm. As such, a CIS can be fitted to a commercially available mass spectrometer with relative ease. Once operational, an instrument fitted with a CIS could dramatically change the field of mass spectrometry by facilitating analysis of pictogram quantities of elements using high precision Faraday cup detectors in place of secondary electron multipliers.

Lewis, L. A.; Borg, L. E.; Hutcheon, I. D.

2011-12-01

282

Cavity Radar Cross Section Prediction  

Microsoft Academic Search

Alternative models are discussed for the determination of the interior irradiation contribution to the radar cross section (RCS) of open-ended cavities. Typical applications of practical interest include radiation field prediction of open-ended waveguides and signature prediction of jet engine air intakes and exhaust outlets. It is shown and explained why the classic perfectly conducting (PEC) ground plane (GP) model sometimes

Adam Zdunek; Waldemar Rachowicz

2008-01-01

283

IMRT in oral cavity cancer  

Microsoft Academic Search

BACKGROUND: Except for early T1,2 N0 stages, the prognosis for patients with oral cavity cancer (OCC) is reported to be worse than for carcinoma in other sites of the head and neck (HNC). The aim of this work was to assess disease outcome in OCC following IMRT. Between January 2002 and January 2007, 346 HNC patients have been treated with

Gabriela Studer; Roger A Zwahlen; Klaus W Graetz; Bernard J Davis; Christoph Glanzmann

2007-01-01

284

ADPF spoke cavity cryomodule concept  

SciTech Connect

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

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

2001-01-01

285

CW cavity ring down spectroscopy  

Microsoft Academic Search

Until now, applications of cavity ring down spectroscopy (CRDS) employed pulsed laser sources. Here, we demonstrate that a commercial single-frequency CW laser can also be conveniently employed, allowing to gain in spectral resolution, signal intensity and data acquisition rate. As a demonstration, we measured a section of the weak HCCH overtone transition near 570 nm, and compare to existing photoacoustic

D. Romanini; A. A. Kachanov; N. Sadeghi; F. Stoeckel

1997-01-01

286

Facing rim cavities fluctuation modes  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

287

Technological diffusion: European experience to 1850  

Microsoft Academic Search

This paper considers the diffusion of British technology to the Continent, especially France and Prussia, during the industrial revolution. Particular attention is paid to the various transmission mechanisms and to differences in the speed of diffusion. It is shown that the economic growth of a country and its absorption of foreign technology tends to follow a logistic curve. This suggests

Charles P. Kindleberger

1995-01-01

288

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

NASA Astrophysics Data System (ADS)

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

De Lucas, Javier

2014-10-01

289

Experimental Cavity Pressure Distributions at Supersonic Speeds.  

National Technical Information Service (NTIS)

An investigation was conducted to define pressure distributions for rectangular cavities over a range of free-stream Mach numbers and cavity dimensions. These pressure distributions together with schlieren photographs are used to define the critical value...

R. L. Stallings, F. J. Wilcox

1987-01-01

290

A metamaterial surface for compact cavity resonators  

Microsoft Academic Search

We suggest an idea for miniaturization of cavities by utilizing a properly designed metamaterial thin surface inserted inside the cavities. This metamaterial surface is constituted by a thin dielectric slab on both sides of which \\

Marco Caiazzo; Stefano Maci; Nader Engheta

2004-01-01

291

Operational experience with crab cavities at KEKB  

E-print Network

KEKB was in operation from December 1988 to June 2010. The crab cavities were installed at KEKB in February 2007 and worked very stably until the end of KEKB operation. Operational experience of the crab cavities with beams is described.

Funakoshi, Y

2014-01-01

292

Introduction Diffusion Tensor Imaging  

E-print Network

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

Zhang, Shuzhong

293

Potassium ions in the cavity of a KcsA channel model.  

PubMed

The high rate of ion flux and selectivity of potassium channels has been attributed to the conformation and dynamics of the ions in the filter which connects the channel cavity and the extracellular environment. The cavity serves as the reservoir for potassium ions diffusing from the intracellular medium. The cavity is believed to decrease the dielectric barrier for the ions to enter the filter. We study here the equilibrium and dynamic properties of potassium ions entering the water-filled cavity of a KcsA channel model. Atomistic molecular dynamics simulations that are supplemented by electrostatic calculations reveal the important role of water molecules and the partially charged protein helices at the bottom of the cavity in overcoming the energy barrier and stabilizing the potassium ion in the cavity. We further show that the average time for a potassium ion to enter the cavity is much shorter than the conduction rate of a potassium passing through the filter, and this time duration is insensitive over a wide range of the membrane potential. The conclusions drawn from the study of the channel model are applicable in generalized contexts, including the entry of ions in artificial ion channels and other confined geometries. PMID:24483491

Yao, Zhenwei; Qiao, Baofu; Olvera de la Cruz, Monica

2013-12-01

294

An economical wireless cavity-nest viewer  

Microsoft Academic Search

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

Daniel P. Huebner; Sarah R. Hurteau

2007-01-01

295

Collagenous fibroma (desmoplastic fibroblastoma) of the oral cavity  

PubMed Central

Collagenous fibroma (desmoplastic fibroblastoma) is a distinctive yet uncommon fibrous soft tissue tumor. These tumors are rather nondescript in their morphological appearance and have been diagnosed as fibromas or some other benign mesenchymal lesions for years. The most common sites are the upper extremities, followed by the lower extremities. Rare lesions arise in the head and neck region. We report a rare case in the oral cavity and present its unique histopathological features (central fat entrapment) besides others, and diffusely strong vimentin immunopositivity. PMID:22923904

Bhagalia, Sanjay; Jain, Manish; Pardhe, Nilesh; Sireesha, Sundaragiri Krishna

2012-01-01

296

Discrete wavelength-locked external cavity laser  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

297

Power coupler for the ILC crab cavity  

SciTech Connect

The ILC crab cavity will require the design of an appropriate power coupler. The beam-loading in dipole mode cavities is considerably more variable than accelerating cavities, hence simulations have been performed to establish the required external Q. Simulations of a suitable coupler were then performed and were verified using a normal conducting prototype with variable coupler tips.

Burt, G.; Dexter, A.; Jenkins, R.; /Lancaster U.; Beard, C.; Goudket, P.; McIntosh, P.A.; /Daresbury; Bellantoni, Leo; /Fermilab

2007-06-01

298

The nasal cavity microbiota of healthy adults  

PubMed Central

Background The microbiota of the nares has been widely studied. However, relatively few studies have investigated the microbiota of the nasal cavity posterior to the nares. This distinct environment has the potential to contain a distinct microbiota and play an important role in health. Results We obtained 35,142 high-quality bacterial 16S rRNA-encoding gene sequence reads from the nasal cavity and oral cavity (the dorsum of the tongue and the buccal mucosa) of 12 healthy adult humans and deposited these data in the Sequence Read Archive (SRA) of the National Center for Biotechnology Information (NCBI) (Bioproject: PRJNA248297). In our initial analysis, we compared the bacterial communities of the nasal cavity and the oral cavity from ten of these subjects. The nasal cavity bacterial communities were dominated by Actinobacteria, Firmicutes, and Proteobacteria and were statistically distinct from those on the tongue and buccal mucosa. For example, the same Staphylococcaceae operational taxonomic unit (OTU) was present in all of the nasal cavity samples, comprising up to 55% of the community, but Staphylococcaceae was comparatively uncommon in the oral cavity. Conclusions There are clear differences between nasal cavity microbiota and oral cavity microbiota in healthy adults. This study expands our knowledge of the nasal cavity microbiota and the relationship between the microbiota of the nasal and oral cavities. PMID:25143824

2014-01-01

299

Does the availability of artificial cavities affect cavity excavation rates in Red-cockaded Woodpeckers?  

Microsoft Academic Search

ABSI'RACT. Rates of caviry cxcavarion by Red-cockaded Woodpeckers (Picoides borealis) were examined from 1383 co 1999 on the Angelina National Forest in east Texas. We compared the rare of natural cavity excavarion herween 1983 and 1990 (before artificial cavities were available) with the rate of cavity excavation between 1992 and 1993, a period when artificial cavities were regularly installed within

Richard N. Conner; Daniel Saenz; D. Craig Rudolph; Richard R Schaefer

300

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

PubMed

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

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

2014-07-01

301

Cavity Enhanced Velocity Modulation Spectroscopy  

NASA Astrophysics Data System (ADS)

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.

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

2010-11-01

302

Status of the ILC Crab Cavity Development  

SciTech Connect

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.

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

2011-10-20

303

Effects of cavities in the bacterial reaction center  

SciTech Connect

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

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

1995-12-31

304

Spontaneous Photon Emission in Cavities  

NASA Astrophysics Data System (ADS)

We investigate spontaneous photon emission processes of two-level atoms in parabolic and ellipsoidal cavities thereby taking into account the full multimode scenario. In particular, we calculate the excitation probabilities of the atoms and the energy density of the resulting few-photon electromagnetic radiation field by using semiclassical methods for the description of the multimode scenario. Based on this approach photon path representations are developed for relevant transition probability amplitudes which are valid in the optical frequency regime where the dipole and the rotating-wave approximations apply. Comparisons with numerical results demonstrate the quality of these semiclassical results even in cases in which the wave length of a spontaneously emitted photon becomes comparable or even larger than characteristic length scales of the cavity. This is the dynamical regime in which diffraction effects become important so that geometric optical considerations are typically not applicable.

Alber, G.; Griebe, N.

2014-09-01

305

Vented Cavity Radiant Barrier Assembly And Method  

DOEpatents

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.

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

2000-05-16

306

Acoustic cavity technology for high performance injectors  

NASA Technical Reports Server (NTRS)

The feasibility of damping more than one mode of rocket engine combustion instability by means of differently tuned acoustic cavities sharing a common entrance was shown. Analytical procedures and acoustic modeling techniques for predicting the stability behavior of acoustic cavity designs in hot firings were developed. Full scale testing of various common entrance, dual cavity configurations, and subscale testing for the purpose of obtaining motion pictures of the cavity entrance region, to aid in determining the mechanism of cavity damping were the two major aspects of the program.

1976-01-01

307

LHC crab-cavity aspects and strategy  

SciTech Connect

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.

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

2010-05-23

308

Microwave energy storage in resonant cavities  

SciTech Connect

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

Alvarez, R.A.

1983-02-01

309

Controlled directional scattering cavity for tubular absorbers  

DOEpatents

A specular cavity is provided in which an optical receiver is emplaced. The cavity is provided with a series of V groove-like indentations (or pyramidal-type indentations) which redirect energy entering between the receiver and cavity structure onto the receiver. The aperture opening of each V groove is less than half the cavity opening and in most preferred embodiments, much less than half. This enables the optical receiver to be emplaced a distance g from the cavity wherein 0.414r

Winston, Roland (Chicago, IL)

1982-01-01

310

Effective mass in cavity QED  

E-print Network

We consider propagation of a two-level atom coupled to one electro-magnetic mode of a high-Q cavity. The atomic center-of-mass motion is treated quantum mechanically and we use a standing wave shape for the mode. The periodicity of the Hamiltonian leads to a spectrum consisting of bands and gaps, which is studied from a Floquet point of view. Based on the band theory we introduce a set of effective mass parameters that approximately describe the effect of the cavity on the atomic motion, with the emphasis on one associated with the group velocity and on another one that coincides with the conventional effective mass. Propagation of initially Gaussian wave packets is also studied using numerical simulations and the mass parameters extracted thereof are compared with those predicted by the Floquet theory. Scattering and transmission of the wave packet against the cavity are further analyzed, and the constraints for the effective mass approach to be valid are discussed in detail.

Jonas Larson; Janne Salo; Stig Stenholm

2005-05-24

311

Novel Geometries for the LHC Crab Cavity  

SciTech Connect

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.

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

2009-05-01

312

3-D Modeling of Double-Diffusive Convection During Directional Solidification of a Non-Dilute Alloy with Application to the HgCdTe Growth Under Microgravity Conditions  

NASA Technical Reports Server (NTRS)

A numerical calculation for a non-dilute alloy solidification was performed using the FIDAP finite element code. For low growth velocities plane front solidification occurs. The location and the shape of the interface was determined using melting temperatures from the HgCdTe liquidus curve. The low thermal conductivity of the solid HgCdTe causes thermal short circuit through the ampoule walls, resulting in curved isotherms in the vicinity of the interface. Double-diffusive convection in the melt is caused by radial temperature gradients and by material density inversion with temperature. Cooling from below and the rejection at the solid-melt interface of the heavier HgTe-rich solute each tend to reduce convection. Because of these complicating factors dimensional rather then non-dimensional modeling was performed. Estimates of convection contributions for various gravity conditions was performed parametrically. For gravity levels higher then 1 0 -7 of earth's gravity it was found that the maximum convection velocity is extremely sensitive to gravity vector orientation and can be reduced at least by factor of 50% for precise orientation of the ampoule in the microgravity environment. The predicted interface shape is in agreement with one obtained experimentally by quenching. The results of 3-D modeling are compared with previous 2-D finding. A video film featuring melt convection will be presented.

Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

1998-01-01

313

Selective advantage of diffusing faster.  

PubMed

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

Pigolotti, Simone; Benzi, Roberto

2014-05-01

314

Shape Determination for Deformed Electromagnetic Cavities  

SciTech Connect

The measured physical parameters of a superconducting cavity differ from those of the designed ideal cavity. This is due to shape deviations caused by both loose machine tolerances during fabrication and by the tuning process for the accelerating mode. We present a shape determination algorithm to solve for the unknown deviations from the ideal cavity using experimentally measured cavity data. The objective is to match the results of the deformed cavity model to experimental data through least-squares minimization. The inversion variables are unknown shape deformation parameters that describe perturbations of the ideal cavity. The constraint is the Maxwell eigenvalue problem. We solve the nonlinear optimization problem using a line-search based reduced space Gauss-Newton method where we compute shape sensitivities with a discrete adjoint approach. We present two shape determination examples, one from synthetic and the other from experimental data. The results demonstrate that the proposed algorithm is very effective in determining the deformed cavity shape.

Akcelik, Volkan; Ko, Kwok; Lee, Lie-Quan; Li, Zhenghai; Ng, Cho-Kuen; Xiao, Liling; /SLAC

2007-12-10

315

Novel Geometries for the LHC Crab Cavity  

SciTech Connect

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.

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

2010-05-23

316

Novel Geometries for the LHC Crab Cavity  

SciTech Connect

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.

B. Hall,G. Burt,C. Lingwood,Robert Rimmer,Haipeng Wang; Hall, B. [CI Lancaster University (Great Britain); Burt, G. [CI Lancaster University (Great Britain); Lingwood, C. [CI Lancaster University (Great Britain); Rimmer, Robert [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Wang, Haipeng [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

2010-05-01

317

DISCREPANCY IN AEROSOL FORCING OF DIFFUSE DOWNWELLING SHORTWAVE IRRADIANCE  

E-print Network

components Direct Normal Solar Irradiance DNSI Diffuse Downwelling Irradiance DDI SHADED PYRANOMETER #12;DNSI CLOSURE EXPERIMENT Direct Normal Solar Irradiance (DNSI): Measure: Normal incidence pyrheliometer, Active cavity radiometer Model: DNSI = - E d0( )exp( ) E0( ) = solar spectral irradiance at top of atmosphere

Schwartz, Stephen E.

318

Low-lying bifurcations in cavity quantum electrodynamics  

E-print Network

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/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 Schrodinger 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.

Michael A. Armen; Hideo Mabuchi

2006-02-21

319

Physics of Crystal Growth  

NASA Astrophysics Data System (ADS)

Preface; List of symbols; 1. Morphology of a crystal surface; 2. Surface free energy, step free energy, and chemical potential; 3. The equilibrium crystal shape; 4. Growth and dissolution crystal shapes: Frank's model; 5. Crystal growth: the abc; 6. Growth and evaporation of a stepped surface; 7. Diffusion; 8. Thermal smoothing of a surface; 9. Silicon and other semiconducting materials; 10. Growth instabilities of a planar front; 11. Nucleation and the adatom diffusion length; 12. Growth roughness at long lengthscales in the linear approximation; 13. The Kardar-Parisi-Zhang equation; 14. Growth without evaporation; 15. Elastic interactions between defects on a crystal surface; 16. General equations of an elastic solid; 17. Technology, crystal growth and surface science; Appendices; References; Index.

Pimpinelli, Alberto; Villain, Jacques

1998-12-01

320

Microfluidic Perfusion for Regulating Diffusible Signaling in Stem Cells  

E-print Network

Microfluidic Perfusion for Regulating Diffusible Signaling in Stem Cells Katarina Blagovic1 , Lily overall diffusible signaling through the physical removal of cell-secreted ligands. Methodology\\paracrine) factors to downregulate diffusible signaling. By comparing cell growth and differentiation in side

Voldman, Joel

321

NONLINEAR DIFFUSION Erkut Erdem  

E-print Network

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

Erdem, Erkut

322

LINEAR DIFFUSION Erkut Erdem  

E-print Network

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

Erdem, Erkut

323

Cavities  

MedlinePLUS

... way to eliminate pain is to remove the pulp by root canal (endodontic) treatment or tooth removal (extraction). If a tooth is ... of extracted teeth (see Dental Appliances ). ... of a front tooth. Fine instruments are passed through the hole into the pulp canal space, and all the remaining pulp is ...

324

Wind power technology diffusion analysis in selected states of India  

Microsoft Academic Search

The theory of diffusion of innovation is used to study the growth of wind power technology in different states of India. Though the policies of the central government of India encouraged growth of the wind power sectors, individual states had varying policy measures which influenced the rates of diffusion in wind energy in different states. The state level data of

K. Usha Rao; V. V. N. Kishore

2009-01-01

325

Temperature Structure of a Coronal Cavity  

NASA Technical Reports Server (NTRS)

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).

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

2011-01-01

326

Auroral Kilometric Radiation from a nonstationary thin plasma cavity  

NASA Astrophysics Data System (ADS)

Results obtained using a waveguide model of the AKR generation in thin plasma cavities are presented. It has been shown that extraordinary X mode waves excited due to the electron cyclotron maser instability cannot be radiated outwards from a cavity when a stationary model is used. Taking into account the low frequency plasma motion we propose a nonstationary waveguide model of the AKR generation, and show that there can exist localized regions of instability from which X mode waves, growing in time, can be radiated outwards. It has been found that waves propagating quasi-tangentially to the source frontiers have the maximum growth rate and escape outward most efficiently, that is in accordance with experimental observations.

Burinskaya, T.; Rauch, J.-L.

2012-04-01

327

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

328

Parallel flow diffusion battery  

DOEpatents

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.

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

1984-08-07

329

Parallel flow diffusion battery  

DOEpatents

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.

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

1984-01-01

330

A terahertz plasmon cavity detector  

NASA Astrophysics Data System (ADS)

Sensitivity of a plasmonic detector is enhanced by integrating a broadband log-periodic antenna with a two-dimensional plasma cavity that is defined by source, drain, and multiple gates of a GaAs/AlGaAs high electron mobility transistor. Both narrow-band terahertz detection and a rich harmonic spectrum are evident. With a bolometric sensor in the channel, we report responsivity, on resonance at 235-240 GHz and at 20 K, of up to 7 kV/W and a noise equivalent power of 510-10 W/Hz1/2.

Dyer, G. C.; Vinh, N. Q.; Allen, S. J.; Aizin, G. R.; Mikalopas, J.; Reno, J. L.; Shaner, E. A.

2010-11-01

331

A terahertz plasmon cavity detector  

SciTech Connect

Sensitivity of a plasmonic detector is enhanced by integrating a broadband log-periodic antenna with a two-dimensional plasma cavity that is defined by source, drain, and multiple gates of a GaAs/AlGaAs high electron mobility transistor. Both narrow-band terahertz detection and a rich harmonic spectrum are evident. With a bolometric sensor in the channel, we report responsivity, on resonance at 235-240 GHz and at 20 K, of up to 7 kV/W and a noise equivalent power of 5x10{sup -10} W/Hz{sup 1/2}.

Dyer, G. C.; Vinh, N. Q.; Allen, S. J. [Institute for Terahertz Science and Technology, UC Santa Barbara, Santa Barbara, California 93106 (United States); Aizin, G. R.; Mikalopas, J. [Kingsborough College, City University of New York, Brooklyn, New York 11235 (United States); Reno, J. L.; Shaner, E. A. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States)

2010-11-08

332

Cavity quantum electro-optics  

E-print Network

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.

Mankei Tsang

2010-02-27

333

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

USGS Publications Warehouse

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.

Kile, D. E.

2005-01-01

334

Natural cavities used by wood ducks in north-central Minnesota  

USGS Publications Warehouse

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.

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

1978-01-01

335

Comparing the antibacterial activity of gaseous ozone and chlorhexidine solution on a tooth cavity model  

PubMed Central

Objective: To evaluate the antibacterial activity of gaseous ozone and chlorhexidine solution on a tooth cavity model. Study Design: Twenty-one human molars were divided into 3 groups. Cavities were then cut into the teeth (4 per tooth, 28 cavities per group). After sterilization, the teeth were left in broth cultures of 106 colony-forming units (CFU) ml-1 of Streptococcus mutans (S. mutans) at 36C for 48 h. The appropriate treatment followed (group A, control; group B, 2% chlorhexidine solution; and group C, 80s of treatment with ozone, and the cavities were then filled with composite resin. After 72h, the restorations were removed, dentin chips were collected with an excavator, and the total number of microorganisms was determined. Results: Both of the treatments significantly reduced the number of S. mutans present compared with the control group and there was a significant difference between the all groups in terms of the amount of the microorganisms grown (p < 0.05). Group B was beter than group C; and group C was better than group A. Moreover, it was found that the amount of the growth in the group of chlorhexidine was significantly less than that of the ozone group (p < 0.05). Conclusion: Chlorhexidine solution was the antibacterial treatment most efficacious on S. mutans; however, ozone application could be an anlternative cavity disinfection method because of ozones cavity disinfection activity. Key words:Antibacterial activity, chlorhexidine, ozone, streptococcus mutans, tooth cavity. PMID:24455068

Oztas, Nurhan; Sumer, Zeynep

2013-01-01

336

Mounting system for optical frequency reference cavities  

NASA Technical Reports Server (NTRS)

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.

Notcutt, Mark (Inventor); Hall, John L. (Inventor); Ma, Long-Sheng (Inventor)

2008-01-01

337

Coupled-cavity drift-tube linac  

DOEpatents

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.

Billen, J.H.

1996-11-26

338

Cavity-enhanced direct frequency comb spectroscopy  

E-print Network

Cavity-enhanced direct frequency comb spectroscopy combines broad spectral bandwidth, high spectral resolution, precise frequency calibration, and ultrahigh detection sensitivity, all in one experimental platform based on an optical frequency comb interacting with a high-finesse optical cavity. Precise control of the optical frequency comb allows highly efficient, coherent coupling of individual comb components with corresponding resonant modes of the high-finesse cavity. The long cavity lifetime dramatically enhances the effective interaction between the light field and intracavity matter, increasing the sensitivity for measurement of optical losses by a factor that is on the order of the cavity finesse. The use of low-dispersion mirrors permits almost the entire spectral bandwidth of the frequency comb to be employed for detection, covering a range of ~10% of the actual optical frequency. The light transmitted from the cavity is spectrally resolved to provide a multitude of detection channels with spectral ...

Thorpe, Michael J

2008-01-01

339

Coupled-cavity drift-tube linac  

DOEpatents

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.

Billen, James H. (Los Alamos, NM)

1996-01-01

340

Cavity-Dumped Communication Laser Design  

NASA Technical Reports Server (NTRS)

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.

Roberts, W. T.

2003-01-01

341

SINAP surface preparation processing for superconducting cavities  

E-print Network

Surface preparation is an important processing in the superconducting niobium cavities production procedures, deciding whether the performance of the niobium cavities could meet the specifications. A series of surface preparation methods and relevant apparatuses have been constructed at SINAP and successfully applied to different types of cavities. With proper surface preparation on the 500 MHz 5-cell niobium cavity, the cavity accelerating voltage at T =4.2 K reached as high as 7.5 MV while its quality factor was still higher than 1E+9. In the meantime, the accelerating gradient of the IMP-HWR010 cavity, which has completed the surface preparation at SINAP, reached 4.9 MV/m with the quality factor better than 3E+8 at 4.2 K.

Ma, Zhen-Yu; Hou, Hong-Tao; Wang, Yan; Shi, Jing; Luo, Chen; Feng, Zi-Qiang; Mao, Dong-Qing; Tang, Zheng-Bo; Li, Zheng; Zhao, Shen-Jie; Zhang, Zi-Gang; Zheng, Xiang; Zhao, Yu-Bin

2014-01-01

342

NEW CAVITY SHAPE DEVELOPMENTS FOR CRABBING APPLICATIONS  

E-print Network

Deflecting mode cavities are required in several accelerators for use as crab cavities in colliders and light sources and as separators. The space requirements for these applications are extremely tight due to two or more beamlines being close together. In addition the dipole mode cavities have lower and same order modes as well as higher order modes which require damping to very low Q values. A number of designs are proposed for compact and/or strongly damped SRF crab cavities. This paper will discuss various coaxial type crab cavities which allow the design of compact crab cavities operating at frequencies below 500 MHz. In addition a number of novel damping schemes will be shown and evaluation of these designs including multipacting will be discussed.

Burt, G

2009-01-01

343

Manifestations and pathological features of solitary thin-walled cavity lung cancer observed by CT and PET/CT imaging  

PubMed Central

The aim of the present study was to analyze and improve the understanding of computed tomography (CT) and positron emission tomography (PET)/CT imaging and the pathological features of solitary thin-walled cavity lung cancer. A total of 16 patients with pathologically confirmed solitary thin-walled cavity lung cancer were included in the present study. All of the patients received CT scans. Among these, two patients underwent an additional PET/CT examination. The CT and PET/CT images were analyzed and a cross-check analysis of the pathological results was conducted. In total, 16 cases of lesions demonstrated thin-walled cavities on the CT images. Among these cases, three presented with an uneven thickening of the cavity walls, 10 cases exhibited wall nodules and three cases presented with compartments in the cavity. The standard uptake value (SUV) of the cavity wall increased in two patients who underwent PET/CT examinations. The 16 cases of lesions were pathologically confirmed as adenocarcinomas. Light microscopy revealed that the tumor cells, which were observed in 12 cases of lesions, had diffused along the inner cavity wall and the tumor cells of four cases had invaded the bronchial wall. Images of the chest that demonstrated a single thin-walled cavity accompanied by uneven thickening of the cavity wall or wall nodules, in addition to an increase in the SUV and compartments in the cavity, indicated potential lung cancer. Valves formed as a result of bronchial wall damage may have led to the cavity. PMID:24959262

QI, YUANGANG; ZHANG, QING; HUANG, YONG; WANG, DAOQING

2014-01-01

344

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

E-print Network

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 ...

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

2014-01-01

345

Scattering model description of cascaded cavity configurations  

E-print Network

Cascaded optical cavities appear in various quantum information processing schemes in which atomic qubits are sitting in separate cavities interconnected by photons as flying qubits. The usual theoretical description relies on a coupled-mode Hamiltonian approach. Here we investigate the system of cascaded cavities without modal decomposition by using a scattering model approach and determine the validity regime of the coupled-mode models.

Andrs Dombi; Peter Domokos

2014-04-30

346

Resonant-cavity antenna for plasma heating  

DOEpatents

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.

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

347

Cavity QED-based quantum walk  

SciTech Connect

We discuss a possible experimental scheme for the implementation of a quantum walk. The scheme is based on the passage of an atom inside a high-Q cavity. The chirality is characterized by the atomic states and the displacement is characterized by the photon number inside the cavity. The quantum steps are described by appropriate interactions with a sequence of classical and quantized cavity fields.

Di Tiegang [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843 (United States); Hillery, Mark [Department of Physics, Hunter College of CUNY, 695 Park Avenue, New York, New York 10021 (United States); Zubairy, M. Suhail [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843 (United States); Department of Electronics, Quaid-i-Azam University, Islamabad (Pakistan)

2004-09-01

348

Temperature stabilization of optofluidic photonic crystal cavities  

Microsoft Academic Search

We present a principle for the temperature stabilization of photonic crystal (PhC) cavities based on optofluidics. We introduce an analytic method enabling a specific mode of a cavity to be made wavelength insensitive to changes in ambient temperature. Using this analysis, we experimentally demonstrate a PhC cavity with a quality factor of Q~15 000 that exhibits a temperature-independent resonance. Temperature-stable

Christian Karnutsch; Cameron L. C. Smith; Alexandra Graham; Snjezana Tomljenovic-Hanic; Ross McPhedran; Benjamin J. Eggleton; Liam O'Faolain; Thomas F. Krauss; Sanshui Xiao; N. Asger Mortensen

2009-01-01

349

A single ion inside a miniature cavity  

E-print Network

A Single Ion Inside a Miniature Cavity Matthias Steiner Robinson College University of Cambridge A thesis submitted for the degree of Doctor of Philosophy Jan 2014 This dissertation is my own work and contains nothing which is the outcome of work... particle level. Compared to the aforementioned experiments with neutral atoms, the dimensions of the cavities employed so far have been much larger leading to lower single-photon-intensities and thereby to weaker ion-cavity couplings. The problem...

Steiner, Matthias

2014-04-08

350

Signal processing system in cavity enhanced spectroscopy  

Microsoft Academic Search

The paper presents a signal processing system used for nitrogen dioxide detection employing cavity enhanced absorption spectroscopy.\\u000a In this system, the absorbing gas concentration is determined by the measurement of a decay time of a light pulse trapped\\u000a in a cavity.\\u000a \\u000a The setup includes a resonance optical cavity, which was equipped with spherical and high reflectance mirrors, the pulsed\\u000a diode

J. Wojtas; Z. Bielecki

2008-01-01

351

Breakthrough: Record-Setting Cavity  

ScienceCinema

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.

Ciovati, Gianluigi

2014-05-21

352

SPINNING MOTIONS IN CORONAL CAVITIES  

SciTech Connect

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{sup -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.

Wang, Y.-M. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Stenborg, G., E-mail: yi.wang@nrl.navy.mi, E-mail: guillermo.stenborg.ctr.ar@nrl.navy.mi [Also at Interferometrics, Inc., Herndon, VA 20171, USA. (United States)

2010-08-20

353

Multi-color Cavity Metrology  

E-print Network

Long baseline laser interferometers used for gravitational wave detection have proven to be very complicated to control. In order to have sufficient sensitivity to astrophysical gravitational waves, a set of multiple coupled optical cavities comprising the interferometer must be brought into resonance with the laser field. A set of multi-input, multi-output servos then lock these cavities into place via feedback control. This procedure, known as lock acquisition, has proven to be a vexing problem and has reduced greatly the reliability and duty factor of the past generation of laser interferometers. In this article, we describe a technique for bringing the interferometer from an uncontrolled state into resonance by using harmonically related external fields to provide a deterministic hierarchical control. This technique reduces the effect of the external seismic disturbances by four orders of magnitude and promises to greatly enhance the stability and reliability of the current generation of gravitational wave detector. The possibility for using multi-color techniques to overcome current quantum and thermal noise limits is also discussed.

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

2012-05-07

354

Breakthrough: Record-Setting Cavity  

SciTech Connect

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.

Ciovati, Gianluigi

2012-03-01

355

Fastrac Rocket Engine Combustion Chamber Acoustic Cavities  

NASA Technical Reports Server (NTRS)

A three dimensional modal analysis was performed using finite fluid elements. The analysis shows four distinct modes of the Fastrac chamber plus cavities near the frequency of the chamber first tangential mode. The mode shapes illustrate the complexity of fluid oscillations in a three dimensional chamber and acoustic cavity. In addition, a first tangential forcing function was applied to the chamber with three different acoustic cavity fluid temperatures. It was observed that the acoustic cavity fluid temperature has a significant effect on the response of the chamber to first tangential mode oscillations.

Christensen, Eric; Nesman, Tom

1998-01-01

356

Large Scale Shape Optimization for Accelerator Cavities  

SciTech Connect

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.

Akcelik, Volkan; Lee, Lie-Quan; Li, Zenghai; Ng, Cho; Xiao, Li-Ling; Ko, Kwok; /SLAC

2011-12-06

357

Cavity-water interface is polar  

E-print Network

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 fluctuations produced by the interfacial waters do not follow the predictions of continuum electrostatics and the continuum limit is not reached for hydrated nano-size solutes.

Friesen, Allan D

2010-01-01

358

Modes of a rotating astigmatic optical cavity  

NASA Astrophysics Data System (ADS)

We generalize the concept of an optical cavity mode to the case of an astigmatic cavity that rotates about its optical axis. We show that the modes of such a cavity are both spatially and spectrally confined and use an algebraic method to study their spatial and spectral structure. Our method involves ladder operators in the spirit of the quantum-mechanical harmonic oscillator. It hinges upon their algebraic properties as well as on the group-theoretical properties of the ray (ABCD) matrix that describes the time-dependent ray dynamics of the rotating cavity.

Habraken, Steven J. M.; Nienhuis, Gerard

2008-05-01

359

Design of the ILC Crab Cavity System  

SciTech Connect

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.

Adolphsen, C.; Beard, C.; Bellantoni, L.; Burt, G.; Carter, R.; Chase, B.; Church, M.; Dexter, A.; Dykes, M.; Edwards, H.; Goudket, P; Jenkins, R.; Jones, R.M.; Kalinin,; Khabiboulline, T.; Ko, K.; Latina, A.; Li, Z.; Ma, L.; McIntosh, P.; Ng, C.; /SLAC /Daresbury /Fermilab /Cockcroft Inst. Accel. Sci. Tech. /CERN

2007-08-15

360

Cavity-locked ring down spectroscopy  

DOEpatents

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.

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

2000-01-01

361

Low beta spoke cavity multipacting analysis  

NASA Astrophysics Data System (ADS)

The simulation and analysis for electron multipacting phenomenon in a low ? spoke superconducting cavity in ADS proton accelerator are proposed. Using both CST and Track3P codes, the electron multipacting calculation for ?=0.12 spoke superconducting cavity is implemented. The methods of multipacting calculation on both codes are studied and described. With the comparison between the calculation results and the cavity vertical test result, the accuracy and reliability of different codes on calculating multipacting are analyzed. Multipacting calculation can help to understand the results of vertical test and also can help to do the optimization in cavity design.

Xu, Bo; Li, Han; Zhang, Juan; Sha, Peng; Wang, Qun-Yao; Lin, Hai-Ying; Huang, Hong; Dai, Jian-Ping; Sun, Yi; Wang, Guang-Wei; Pan, Wei-Min

2013-12-01

362

Cavity-QED-based quantum phase gate  

SciTech Connect

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 of the atom are resonant with one of the cavity modes whereas the lower levels are appropriately detuned from the other mode of the cavity. A {pi} phase shift is introduced when there is one photon each in the two modes and the atom is initially in the ground state. We also discuss the one-bit unitary gate in such a system and discuss potential applications.

Zubairy, M. Suhail [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843-4242, USA (United States); Department of Electronics, Quaid-i-Azam University, Islamabad, (Pakistan); Kim, Moochan [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843-4242, USA (United States); Scully, Marlan O. [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843-4242, USA (United States); Max-Planck-Institut fuer Quantenoptik, D-85748 Garching, (Germany)

2003-09-01

363

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

NASA Astrophysics Data System (ADS)

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

Chubynsky, Mykyta V.; Slater, Gary W.

2014-08-01

364

Outbursts and cavities in comets  

NASA Astrophysics Data System (ADS)

Based on analysis of the images made during the first 13 minutes after the collision of the impact module of the Deep Impact (DI) spacecraft with Comet 9P/Tempel 1, Ipatov & A'Hearn [1] studied time variations of ejection of material after this impact. They showed that, besides the normal ejection, at time t_{e} after the DI collision between 8 s and 60 s there was a considerable additional ejection (a triggered outburst) of small (micron size) particles. It increased the mean velocities of observed small ejected particles (compared with the normal ejection). The outburst could be caused by excavation of a large cavity with dust and gas under pressure. The largest cavity excavated after the collision could be relatively deep because a considerable excess ejection lasted during about 50 s. Schultz et al. [2] concluded that the diameter d_{tc} of the DI transient crater was about 200 m. Some authors support smaller values of d_{tc}. The depth of the DI crater at t_{e}=8 s was estimated in [3] to be about 6 m for d_{tc}=200 m and 4 m for d_{tc}=100 m. The distance between the pre-impact surface of Comet 9P/Tempel 1 and the upper border of the largest excavated cavity equal to about 4-6 m, and sizes of particles inside the cavities of a few microns are in good agreement with the results obtained by Kossacki & Szutowicz [4]. In their models of the explosion of Comet 17P/Holmes, the initial sublimation front of the CO ice was located at a depth of 4 m, 10 m, or 20 m, and calculations were finished when the CO pressure exceeded the threshold value 10 kPa. It was shown that the pressure of CO vapor can rise to this value only when the nucleus is composed of very fine grains, a few microns in radius. The porous structure of comets provides enough space for sublimation. The projection of the velocity of the leading edge of the DI cloud (onto the plane perpendicular to the line of sight) was about 100-200 m/s and is typical for outburst particles ejected from comets (references to the papers devoted to natural outbursts can be found in [5]). Similarity of velocities of particles ejected at triggered and natural outbursts shows that these outbursts could be caused by similar internal processes in comets. It is possible that cavities with dust and gas under pressure can be located a few meters below many places of surfaces of comets. [1] Ipatov S.I. & A'Hearn M.F., MNRAS, 2011, 414, 76-107. [2] Schultz P.H., Hermalyn B., & Veverka J., Icarus, 2013, 222, 502-515. [3] Ipatov S.I., MNRAS, 2012, 423, 3474-3477. [4] Kossacki K.J. & Szutowicz S., Icarus, 2011, 212, 847-857. [5] Ipatov S.I. in: P.G. Melark (ed.), Comets: Characteristics, Composition and Orbits, 2012, 101-112, (http://arxiv.org/abs/1103.0330).

Ipatov, Sergei

365

Generation of a dual-functioning antitumor immune response in the peritoneal cavity.  

PubMed

Tumor cell metastasis to the peritoneal cavity is observed in patients with tumors of peritoneal organs, particularly colon and ovarian tumors. Following release into the peritoneal cavity, tumor cells rapidly attach to the omentum, a tissue consisting of immune aggregates embedded in adipose tissue. Despite their proximity to potential immune effector cells, tumor cells grow aggressively on these immune aggregates. We hypothesized that activation of the immune aggregates would generate a productive antitumor immune response in the peritoneal cavity. We immunized mice i.p. with lethally irradiated cells of the colon adenocarcinoma line Colon38. Immunization resulted in temporary enlargement of immune aggregates, and after challenge with viable Colon38 cells, we did not detect tumor growth on the omentum. When Colon38-immunized mice were challenged with cells from the unrelated breast adenocarcinoma line E0771 or the melanoma line B16, these tumors also did not grow. The nonspecific response was long-lived and not present systemically, highlighting the uniqueness of the peritoneal cavity. Cellular depletions of immune subsets revealed that NK1.1(+) cells were essential in preventing growth of unrelated tumors, whereas NK1.1(+) cells and T cells were essential in preventing Colon38 tumor growth. Collectively, these data demonstrate that the peritoneal cavity has a unique environment capable of eliciting potent specific and nonspecific antitumor immune responses. PMID:23933065

Sedlacek, Abigail L; Gerber, Scott A; Randall, Troy D; van Rooijen, Nico; Frelinger, John G; Lord, Edith M

2013-10-01

366

Collapsing cavities, toroidal bubbles and jet impact  

NASA Astrophysics Data System (ADS)

The present study is aimed at clarifying some of the factors which affect the formation and direction of a liquid jet in a collapsing cavity and the pressures induced on a nearby rigid boundary. The flow can be accurately represented by a velocity potential leading to the use of boundary integral methods to compute bubble collapse. For configurations with axial symmetry, the jet motion and that of the bubble centroid are along the axis of symmetry. Examples are presented for bubbles close to a rigid surface and to a free surface. These are followed through to the toroidal stage after jet penetration. When there is no axis of symmetry, fully three-dimensional computations show that the buoyancy force can cause the jet to move parallel to a vertical rigid boundary, thus negating its damaging effect. The computational study is extended to model cavitation bubble growth and collapse phases in a forward stagnation point flow as a model of reattachment of a boundary layer; a region where severe cavitation damage is often observed. The Kelvin impulse is introduced to aid a better understanding of the mechanics of bubble migration and jet direction in the examples presented. Finally a comparison between the spherical and axisymmetric theories is made for an oscillating bubble in a periodic pressure field; this being of particular interest to current studies in acoustic cavitation and sonoluminescence.

Blake, J. R.; Hooton, M. C.; Robinson, P. B.; Tong, R. P.

367

40 CFR 798.5500 - Differential growth inhibition of repair proficient and repair deficient bacteria: Bacterial DNA...  

Code of Federal Regulations, 2012 CFR

...i) Tests performed on solid medium (diffusion tests). (ii) Tests performed in...of zones of growth inhibition in the diffusion test, it is most important that the... (e) Test performance (1) Diffusion assay (i) Disc diffusion...

2012-07-01

368

40 CFR 798.5500 - Differential growth inhibition of repair proficient and repair deficient bacteria: Bacterial DNA...  

...i) Tests performed on solid medium (diffusion tests). (ii) Tests performed in...of zones of growth inhibition in the diffusion test, it is most important that the... (e) Test performance (1) Diffusion assay (i) Disc diffusion...

2014-07-01

369

40 CFR 798.5500 - Differential growth inhibition of repair proficient and repair deficient bacteria: Bacterial DNA...  

Code of Federal Regulations, 2013 CFR

...i) Tests performed on solid medium (diffusion tests). (ii) Tests performed in...of zones of growth inhibition in the diffusion test, it is most important that the... (e) Test performance (1) Diffusion assay (i) Disc diffusion...

2013-07-01

370

Escape Kinetics of Self-Propelled Janus Particles from a Cavity: Numerical Simulations  

E-print Network

We numerically investigate the escape kinetics of elliptic Janus particles from narrow two-dimensional cavities with reflecting walls. The self-propulsion velocity of the Janus particle is directed along either their major (prolate) or minor axis (oblate). We show that the mean exit time is very sensitive to the cavity geometry, particle shape and self-propulsion strength. The mean exit time is found to be a minimum when the self-propulsion length is equal to the cavity size. We also find the optimum mean escape time as a function of the self-propulsion velocity, translational diffusion, and particle shape. Thus, effective transport control mechanisms for Janus particles in a channel can be implemented.

Ghosh, Pulak Kumar

2014-01-01

371

Escape Kinetics of Self-Propelled Janus Particles from a Cavity: Numerical Simulations  

E-print Network

We numerically investigate the escape kinetics of elliptic Janus particles from narrow two-dimensional cavities with reflecting walls. The self-propulsion velocity of the Janus particle is directed along either their major (prolate) or minor axis (oblate). We show that the mean exit time is very sensitive to the cavity geometry, particle shape and self-propulsion strength. The mean exit time is found to be a minimum when the self-propulsion length is equal to the cavity size. We also find the optimum mean escape time as a function of the self-propulsion velocity, translational diffusion, and particle shape. Thus, effective transport control mechanisms for Janus particles in a channel can be implemented.

Pulak Kumar Ghosh

2014-08-09

372

Communication: Escape kinetics of self-propelled Janus particles from a cavity: Numerical simulations  

NASA Astrophysics Data System (ADS)

We numerically investigate the escape kinetics of elliptic Janus particles from narrow two-dimensional cavities with reflecting walls. The self-propulsion velocity of the Janus particle is directed along either their major (prolate) or minor (oblate) axis. We show that the mean exit time is very sensitive to the cavity geometry, particle shape, and self-propulsion strength. The mean exit time is found to be a minimum when the self-propulsion length is equal to the cavity size. We also find the optimum mean escape time as a function of the self-propulsion velocity, translational diffusion, and particle shape. Thus, effective transport control mechanisms for Janus particles in a channel can be implemented.

Ghosh, Pulak Kumar

2014-08-01

373

TESLA Report 2003-21 Cavity Control System Optimization Methods  

E-print Network

stabilization in the cavity, during flattop period. The introductory analysis of the cavity operational modes accelerators, control theory, free electron laser 1. INTRODUCTION The LLRF (Low Level Radio Frequency) cavityTESLA Report 2003-21 Cavity Control System ­ Optimization Methods For Single Cavity Driving

374

Handheld Diffusion Test Cells  

NASA Technical Reports Server (NTRS)

This photo shows an individual cell from the Handheld Diffusion Test Cell (HH-DTC) apparatus flown on the Space Shuttle. Similar cells will be used in the Observable Protein Crystal Growth Apparatus (OPCGA) to be operated aboard the International Space Station (ISS). The principal investigator is Dr. Alex McPherson of the University of California, Irvine. Each individual cell comprises two sample chambers with a rotating center section that isolates the two from each other until the start of the experiment and after it is completed. The cells are made from optical-quality quartz glass to allow photography and interferometric observations. Each cell has a small light-emitting diode and lens to back-light the solution. In protein crystal growth experiments, a precipitating agent such as a salt solution is used to absorb and hold water but repel the protein molecules. This increases the concentration of protein until the molecules nucleate to form crystals. This cell is one of 96 that make up the experiment module portion of the OPCGA.

2001-01-01

375

Handheld Diffusion Test Cells  

NASA Technical Reports Server (NTRS)

This photo shows the Handheld Diffusion Test Cell (HH-DTC) apparatus flown on the Space Shuttle. Similar cells (inside the plastic box) will be used in the Observable Protein Crystal Growth Apparatus (OPCGA) to be operated aboard the International Space Station (ISS). The principal investigator is Dr. Alex McPherson of the University of California, Irvine. Each individual cell comprises two sample chambers with a rotating center section that isolates the two from each other until the start of the experiment and after it is completed. The cells are made from optical-quality quartz glass to allow photography and interferometric observations. Each cell has a small light-emitting diode and lens to back-light the solution. In protein crystal growth experiments, a precipitating agent such as a salt solution is used to absorb and hold water but repel the protein molecules. This increases the concentration of protein until the molecules nucleate to form crystals. This cell is one of 96 that make up the experiment module portion of the OPCGA.

2001-01-01

376

Grain Growth in Niobium for Superconducting Radio Frequency Cavities  

E-print Network

were changed to reflect this offset. 11 Mounting Samples were mounted according to ASTM E3-01 [8]. Here, four samples went into a pressurized cylinder with bakelite powder and placed under 4 kpsi pressure and heated up to about 135 degrees... Celsius for 15 minutes until the bakelite hardened. Once the mounting hardened, the heater and mounted samples were removed from the cylinder. The sample ID numbers were etched into the backside of the bakelite. Polishing All polishing procedures...

Vernon, Joshua A.

2009-06-09

377

Convection and diffusion effects during dendritic solidification  

NASA Technical Reports Server (NTRS)

A report is presented of the first quantitative measurements of dendritic growth at supercooling levels where convection instead of diffusion is the controlling heat transfer mechanism. Precautions similar to that used in an investigation conducted by Glicksman et al. (1976) were taken to insure 'free' dendritic growth conditions. Dendritic growth velocity was measured as a function of growth orientation at seventeen supercoolings which ranged from 0.043 C to 2 C. Selected but representative measurements of velocity versus orientation angle are shown in a graph. The relative growth velocity of a downward growing dendrite is found to be greater than that of a diffusion-limited dendrite. This result is consistent with that expected from the enhanced heat transfer arising from natural convection.

Glicksman, M. E.; Huang, S.-C.

1979-01-01

378

Computer simulation of phase locking multi-cavity relativistic gyrotrons  

NASA Astrophysics Data System (ADS)

A particle-in-cell model has been employed to investigate the phase-locking phenomenon of multi-cavity relativistic gyrotron oscillators. Simulation results show that a prebunched beam causes the output wave to overshoot, which in turn prolongs the time for establishing phase locking. The beam axial velocity spread is observed to reduce the locking bandwidth. The phenomenon of priming or injection seeding is simulated. The phase locked time depends on the growth rate of the oscillator and the amount of inject frequency deviation from the locking boundary.

Lin, A. T.; Yang, Z. H.; Lin, Chih-Chien

1989-07-01

379

Survival analysis of a critical resource for cavity-nesting communities: patterns of tree cavity longevity.  

PubMed

Tree cavities are a vital multi-annual resource used by cavity-nesting birds and mammals for nesting and shelter. The abundance of this resource will be influenced by the rates at which cavities are created and destroyed. We applied the demographic concepts of survival and longevity to populations of tree holes to investigate rates of loss for cavities in three tree species, as well as how characteristics of nest trees, habitat type, and species of excavator affected the persistence of tree cavities in trembling aspen, Populus tremuloides (95% of cavities were in aspen trees), in interior British Columbia, Canada. By modeling survival of 1635 nesting cavities in aspen over a time span of 16 years, we found that the decay stage of the nest tree was the most important factor determining cavity longevity. Cavities in trees with advanced decay had a relatively short median longevity of 7 years (95% CI 6-9 years), whereas those in living trees had a median longevity of more than 15 years. We found that cavity longevity was greater in continuous forest than in aspen grove habitat. Interestingly, cavities formed by weak excavators survived as long as those created by Northern Flickers (Colaptes auratus), despite occurring in more decayed tree stems. Thus, weak excavators may be selecting for characteristics that make a tree persistent, such as a broken top. Our results indicate that retention of cavities in large, live aspen trees is necessary to conserve persistent cavities, and that cavity longevity will have a large effect on the structure and function of cavity-using vertebrate communities. PMID:23092011

Edworthy, Amanda B; Wiebe, Karen L; Martin, Kathy

2012-09-01

380

Passively controlled supersonic cavity flow using a spanwise cylinder  

NASA Astrophysics Data System (ADS)

An experimental investigation of a passively controlled open cavity with a length to depth ratio of six and freestream Mach number of 1.4 was conducted to investigate the mechanisms responsible for the observed surface pressure reductions. The passive control comes from placing a spanwise aligned cylinder in the boundary layer near the leading edge of the cavity. The two control configurations were isolated from previous experiments of the fluctuating surface pressure and correspond to a larger diameter rod near the top of the boundary layer and a smaller diameter rod placed near the wall. These were further analyzed using particle image velocimetry in an attempt to elicit the responsible mechanism for the flow control. The use of two-point statistics revealed the wall normal turbulent velocity correlation's evolution became elongated in the wall normal direction. This suggests that the shear layer may be less-organized and consists of smaller-scale structures. The disturbance of the feedback receptivity loop is clearly demonstrated for the controlled configurations evidenced by weakened correlation signals between the aft wall sensor and positions on the cavity floor. The presence of the rod is shown to decrease the mean shear gradient, more effectively for the large rod placed at the top of the boundary layer, throughout the shear layer. The efficacy of the control leads to an initially thicker shear layer which spreads more rapidly and is clearly demonstrated by vorticity growth rates, mean, and turbulent flowfield statistics.

Dudley, Jonathan G.; Ukeiley, Lawrence

2014-09-01

381

Epithelial Dysplasia in Oral Cavity  

PubMed Central

Among oral lesions, we encounter a series of malignant epithelial lesions that go through clinical and histopathologic processes in order to be diagnosed. Identifying these processes along with the etiology knowledge of these lesions is very important in prevention and early treatments. Dysplasia is the step preceding the formation of squamous cell carcinoma in lesions which have the potential to undergo dysplasia. Identification of etiological factors, clinical and histopathologic methods has been the topic of many articles. This article, reviews various articles presenting oral cavity dysplasia, new clinical methods of identifying lesions, and the immunohistochemical research which proposes various markers for providing more precise identification of such lesions. This article also briefly analyzes new treatment methods such as tissue engineering. PMID:25242838

Shirani, Samaneh; Kargahi, Neda; Razavi, Sayed Mohammad; Homayoni, Solmaz

2014-01-01

382

Mini-cavity-dumped laser  

NASA Technical Reports Server (NTRS)

Lasers for use in high precision satellite ranging systems consist typically of an oscillator followed by several amplifier stages. While the shortest optical pulses are achieved by using a mode locked oscillator, such an oscillator is incompatible with the compact design needed in future, highly mobile systems. The laser oscillator achieves pulse lengths approaching those obtainable by mode locking, but in a much more compact and stable design. The oscillator uses two LiNbO3 Pockels cells inside the resonator. One Q-switches the oscillator, and the other is used in a pulse slicing scheme to cavity dump a portion of the circulating optical energy. The length of the optical output pulse measured at 425 + or - 50 picoseconds.

Reed, E.

1981-01-01

383

Reaction-diffusion textures  

Microsoft Academic Search

We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

Andrew P. Witkin; Michael Kass

1991-01-01

384

Geometric Model of a Coronal Cavity  

NASA Technical Reports Server (NTRS)

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

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

385

A micro-cavity fluidic dye laser  

Microsoft Academic Search

We have successfully fabricated and characterized a micro-cavity fluidic dye laser with metallic mirrors, which can be integrated with other microfluidic systems without adding further process steps. A laser dye solution is pumped through a microfluidic channel containing the laser cavity. The microfluidic channel structure, which is formed in SU-8 photoresist, is sandwiched between Pyrex glass wafers, bonded together at

Bjarne Helbo; Anders Kristensen; Aric Menon

2003-01-01

386

Coupled mode theory of optical resonant cavities  

Microsoft Academic Search

This paper presents a theory describing coupled optical resonant cavities by means of systems of time-dependent coupled equations for the field amplitudes of standing waves in each resonator. The coupling coefficients entering the theory are derived from first principles. The coupling coefficients can approximately be related to the amplitude transmission coefficients of traveling waves passing between the two resonant cavities.

D. Marcuse

1985-01-01

387

The Coupling of Cavity Modes to Spins  

Microsoft Academic Search

The interaction energy between two spins in a cavity is derived. It is assumed that each spin interacts with all the magnetic fields which exist at the point in the cavity where it resides. One spin is then made aware of the presence of the other by the changes in the mode excitations which are produced. This approach is thought

I N Court; K W H Stevens

1963-01-01

388

Compact microwave cavity for hydrogen atomic clock  

NASA Technical Reports Server (NTRS)

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.

Zhang, Dejun; Zhang, Yan; Fu, Yigen; Zhang, Yanjun

1992-01-01

389

Cooling in a Bistable Optical Cavity  

SciTech Connect

We propose a generic approach to nonresonant laser cooling of atoms and molecules in a bistable optical cavity. The method exemplifies a photonic version of Sisyphus cooling, in which the matter-dressed cavity extracts energy from the particles and discharges it to the external field as a result of sudden transitions between two stable states.

Vilensky, Mark Y.; Prior, Yehiam; Averbukh, Ilya Sh. [Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100 (Israel)

2007-09-07

390

Sonic crystal with open resonant cavities  

Microsoft Academic Search

An improved scattering matrix method is developed to study a two-dimensional air-rigid sonic crystal with open resonant cavity, and the band structure and transmission properties are investigated. Numerical results show that both the band structure and the transmission coefficient are sensitive to the shape of the resonant cavity. The relationship between the resonant band gap and the shape of the

Zhilin Hou; Jingtao Liu; Weimin Kuang; Youyan Liu; Shuizhu Wu

2007-01-01

391

Large grain cavities from pure niobium ingot  

DOEpatents

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.

Myneni, Ganapati Rao (Yorktown, VA); Kneisel, Peter (Williamsburg, VA); Cameiro, Tadeu (McMurray, PA)

2012-03-06

392

Mode suppression means for gyrotron cavities  

DOEpatents

In a gyrotron electron tube of the gyro-klystron or gyro-monotron type, having a cavity supporting an electromagnetic mode with circular electric field, spurious resonances can occur in modes having noncircular electric field. These spurious resonances are damped and their frequencies shifted by a circular groove in the cavity parallel to the electric field.

Chodorow, Marvin (Stanford, CA); Symons, Robert S. (Los Altos, CA)

1983-08-09

393

THE BRIDGE COUPLING CAVITIES IN THE SEPARATED  

Microsoft Academic Search

The Separated Drift Tube Linac (SDTL) structure was pro- posed for medium energy range of proton linacs. The ac- celerating cavity consists of several SDTL units with fo- cusing lenses between sections. To drive several SDTL sections from single RF source, application of both RF power dividers and coupling bridge cavities seems feasible. Through bridge couplers, the field distribution, in

V. V. Paramonov; L. V. Kravchuk; A. S. Levchenko

394

Tunable-cavity QED with phase qubits  

NASA Astrophysics Data System (ADS)

We describe a tunable-cavity quantum electrodynamics (QED) architecture with an rf SQUID phase qubit inductively coupled to a single-mode, resonant cavity with a tunable frequency that allows for both microwave readout of tunneling and dispersive measurements of the qubit. Dispersive measurement is well characterized by a three-level model, strongly dependent on qubit anharmonicity, qubit-cavity coupling, and detuning. A tunable-cavity frequency provides a way to strongly vary both the qubit-cavity detuning and coupling strength, which can reduce Purcell losses, cavity-induced dephasing of the qubit, and residual bus coupling for a system with multiple qubits. With our qubit-cavity system, we show that dynamic control over the cavity frequency enables one to avoid Purcell losses during coherent qubit evolutions and optimize state readout during qubit measurements. The maximum qubit decay time T1=1.5?s is found to be limited by surface dielectric losses from a design geometry similar to planar transmon qubits.

Whittaker, J. D.; da Silva, F. C. S.; Allman, M. S.; Lecocq, F.; Cicak, K.; Sirois, A. J.; Teufel, J. D.; Aumentado, J.; Simmonds, R. W.

2014-07-01

395

Generation of entangled photon pairs in optical cavity-QED: Operating in the bad cavity limit  

E-print Network

We propose an optical cavity-QED scheme for the deterministic generation of polarization entangled photon pairs that operates with high fidelity even in the bad cavity limit. The scheme is based on the interaction of an excited four-level atom with two empty optical cavity modes via an adiabatic passage process. Monte-Carlo wave function simulations are used to evaluate the fidelity of the cavity-QED source and its entanglement capability in the presence of decoherence. In the bad cavity limit, fidelities close to one are predicted for state-of-the-art experimental parameter values.

R. Garca-Maraver; K. Eckert; R. Corbaln; J. Mompart

2008-12-28

396

Surveying Diffusion in Complex Geometries. An Essay  

E-print Network

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...

Grebenkov, Denis

2009-01-01

397

Optomechanical photon shuttling between photonic cavities.  

PubMed

Mechanical motion of photonic devices driven by optical forces provides a profound means of coupling between optical fields. The current focus of these optomechanical effects has been on cavity optomechanics systems in which co-localized optical and mechanical modes interact strongly to enable wave mixing between photons and phonons, and backaction cooling of mechanical modes. Alternatively, extended mechanical modes can also induce strong non-local effects on propagating optical fields or multiple localized optical modes at distances. Here, we demonstrate a multicavity optomechanical device in which torsional optomechanical motion can shuttle photons between two photonic crystal nanocavities. The resonance frequencies of the two cavities, one on each side of this 'photon see-saw', are modulated antisymmetrically by the device's rotation. Pumping photons into one cavity excites optomechanical self-oscillation, which strongly modulates the inter-cavity coupling and shuttles photons to the other empty cavity during every oscillation cycle in a well-regulated fashion. PMID:25240675

Li, Huan; Li, Mo

2014-11-01

398

Optical nanofiber-based photonic crystal cavity.  

PubMed

We demonstrate the fabrication of photonic crystal (PhC) cavities on optical nanofibers using femtosecond laser ablation. PhC cavities with cavity lengths varying from 0.54 to 3.43 mm are fabricated by controlling the profile of the nanocrater array formed on the nanofiber. Such PhC cavities show high transmission of 87% for a finesse of 39. For higher finesse values from 150 to 500, the transmission can still be maintained at 20%-25%. Due to the strong confinement of the field and the efficient coupling to single-mode optical fibers, such nanofiber-based PhC cavities may become an interface between quantum and classical networks. PMID:24562114

Nayak, K P; Zhang, Pengfei; Hakuta, K

2014-01-15

399

Optomechanical photon shuttling between photonic cavities  

E-print Network

Mechanical motion of photonic devices driven by optical forces provides a profound means of coupling between optical fields. The current focus of these optomechanical effects has been on cavity optomechanics systems in which co-localized optical and mechanical modes interact strongly to enable wave-mixing between photons and phonons and backaction cooling of mechanical modes. Alternatively, extended mechanical modes can also induce strong nonlocal effects on propagating optical fields or multiple localized optical modes at distances. Here, we demonstrate a novel multi-cavity optomechanical device: a "photon see-saw", in which torsional optomechanical motion can shuttle photons between two photonic crystal nanocavities. The resonance frequencies of the two cavities, one on each side of the see-saw, are modulated anti-symmetrically by the device's rotation. Pumping photons into one cavity excites optomechanical self-oscillation which strongly modulates the inter-cavity coupling and shuttles photons to the other...

Li, Huan

2014-01-01

400

Performance of 3-cell Seamless Niobium cavities  

SciTech Connect

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.

Kneisel, Peter K. [JLAB; Ciovati, Gianluigi [JLBA; Jelezov, I. [DESY, Hamburg; Singer, W. [DESY, Hamburg; Singer, X. [DESY, Hamburg

2009-11-01

401

Magnetospheric cavity modes - Some nonlinear effects  

NASA Astrophysics Data System (ADS)

A two-dimensional, nonlinear hydromagnetic computer code is applied here to the problem of pure fast mode cavity resonances in the simplest possible box model of the magnetosphere in order to determine basic nonlinear effects of magnetospheric cavity modes. The results show that significant nonlinear effects can occur at maximum velocity v(0). The initial impulse develops into a relatively weak shock as it propagates into the magnetosphere. After cavity modes are set up, their temporal development is very different from the corresponding linear modes. In particular, the cavity mode frequencies are reduced and the temporal structure of the modes is apparently not well represented by sinusoidal functions. Much of the change in behavior can be attributed to a large distortion of the background plasma mass density. Expressions for the ponderomotive force as it applies to small but finite amplitude cavity modes are developed, and it is shown that these expressions are consistent with the simulation results.

Allan, W.; Poulter, E. M.; Manuel, J. R.

1991-07-01

402

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

SciTech Connect

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.

Narushima, Takayuki; Glaeser, Andreas M.

2000-12-01

403

Superconducting cavity tuner performance at CEBAF  

SciTech Connect

At the Continuous Electron Beam Accelerator Facility (CEBAF), a 4 GeV, multipass CW electron beam is to be accelerated by 338 SRF, 5-cell niobium cavities operating at a resonant frequency of 1497 MHz. Eight cavities arranged as four pairs comprise a cyromodule, a croygenically isolated linac subdivision. The frequency is controlled by a mechanical tune attached to the first and fifth cell of the cavity which elastically deforms the cavity and thereby alters its resonant frequency. The tuner is driven by a stepper motor mounted external to the cryomodule that transfers torque through two rotary feedthroughs. A linear variable differential transducer (LVDT) mounted on the tuner monitors the displacement, and two limit switches interlock the movement beyond a 400 kHz bandwidth. Since the cavity has a loaded Q of 6.6 {center_dot} 10{sup 6}, the control system must maintain the frequency of the cavity to within {plus_minus} 50 Hz of the drive frequency for efficient coupling. This requirement is somewhat difficult to achieve since the difference in thermal contractions of the cavity and the tuner creates a frequency hystersis of approximately 10 kHz. The cavity is also subject to frequency shifts due to pressure fluctuations of the helium bath as well as radiation pressure. This requires that each cavity be characterized in terms of frequency change as a function of applied motor steps to allow proper tuning operations. This paper describes the electrical and mechanical performance of the cavity tuner during the commissioning and operation of the cryomodulus manufactured to date.

Marshall, J.; Preble, J.; Schneider, W.

1993-06-01

404

Wakefields in Photonic Crystal Accelerator Cavities  

NASA Astrophysics Data System (ADS)

The RF properties of photonic crystals (PhCs) can be exploited to avoid the parasitic higher order modes (HOMs) that degrade beam quality in accelerator cavities and reduce efficiency and power in RF generators. For example, an accelerator cavity can be designed using a PhC structure that traps only modes within a narrow frequency range, so that the cavity has only a single mode. Although the lack of HOMs is perhaps the most drastic difference between PhC cavities and traditional metal cavities, PhC cavities should allow a much wider range of materials and shapes, which could potentially lead to cavities that operate at higher electric fields and at higher frequencies (with lower losses). However, this greater flexibility introduces many challenges for building actual structures. A hybrid cavity that uses a dielectric 2D PhC along with metal plates to trap fields in the third dimension may offer the advantages of a PhC cavity while being relatively easy to construct. Although the 2D photonic structure may allow only a single mode, the 3D structure can in principle trap HOMs, such as guided modes in the dielectric rods that form the PhC; however, computer simulations show that long-range wake fields can be significantly reduced in such hybrid structures. For a 3D cavity based on a triangular lattice of dielectric rods, the rod positions can be optimized (breaking the lattice symmetry) to reduce radiation leakage using a fixed number of rods; moreover, the optimized structure can further reduce the wake fields.

Werner, Gregory

2009-11-01

405

Basic Electropolishing Process Research and Development in Support of Improved Reliable Performance SRF Cavities for the Future Accelerator  

SciTech Connect

Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nanosmoothness. Electropolishing is the technique of choice to be developed for high-field superconducting radiofrequency cavities. Electrochemical impedance spectroscopy (EIS) and related techniques point to the electropolishing mechanism of Nb in a sulfuric and hydrofluoric acid electrolyte of controlled by a compact surface salt film under F- diffusion-limited mass transport control. These and other findings are currently guiding a systematic characterization to form the basis for cavity process optimization, such as flowrate, electrolyte composition and temperature. This integrated analysis is expected to provide optimum EP parameter sets for a controlled, reproducible and uniform surface leveling for Nb SRF cavities.

H. Tian, C.E. Reece,M.J. Kelley

2009-05-01

406

Natural convection in a vertical porous cavity: A numerical study for Brinkman-extended Darcy formulation  

Microsoft Academic Search

A dimensional analysis of the Brinkman-extended Darcy formulation, which includes the transport and viscous terms, leads to four governing parameters for steady-state natural convection in a vertical porous cavity. They are: Rayleigh number, Darcy number, diffusion parameter Ω, and aspect ratio. Numerical results for 0 Da 10⁻¹, 10 Ra* 5 10³, and A = 1

G. Lauriat; V. Prasad

1987-01-01

407

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

DOEpatents

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.

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

1995-12-26

408

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

DOEpatents

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.

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

1995-01-01

409

21 CFR 872.6030 - Oral cavity abrasive polishing agent.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Oral cavity abrasive polishing agent. 872.6030 Section...Devices 872.6030 Oral cavity abrasive polishing agent. (a) Identification. An oral cavity abrasive polishing agent is a device in...

2010-04-01

410

Photomodulated reflectance study of InxGa1-xAs\\/GaAs\\/AlAs microcavity vertical-cavity surface emitting laser structures in the weak-coupling regime: The cavity\\/ground-state-exciton resonance  

Microsoft Academic Search

Two InGaAs\\/GaAs\\/AlAs vertical-cavity surface emitting laser (VCSEL) structures have been studied by conventional reflectance (R) and photomodulated reflectance (PR) spectroscopies at ~300 K and ~80 K. Growth variations across the samples (<2%) give rise to smooth changes in the cavity mode energy so that it can be tuned through the position of resonance with the quantum well (QW) ground-state exciton,

P. J. Klar; G. Rowland; P. J. S. Thomas; A. Onischenko; T. E. Sale; T. J. C. Hosea; R. Grey

1999-01-01

411

The diffusion of water in haploanesite  

NASA Astrophysics Data System (ADS)

Diffusive transport of water in silicate melts is a key process in magma dynamics and volcanic eruptions, including bubble growth. Previous studies demonstrate that in additional to temperature, water content and pressure, melt composition also plays an important role in determining water diffusivity. We carried out high temperature (1311-1512C) diffusion-couple experiments and intermediate temperature (470- 600C) dehydration experiments to investigate H2O diffusion in a melt of haploandesitic composition. The diffusion couple is composed of an anhydrous (with <0.1 wt.% H2O) and a hydrous (with 2 wt.% H2O) haploandesitic glass. A platinum capsule is used to contain the couple and then it is welded shut. Diffusion runs are carried out in a 12.7-mm piston-cylinder apparatus at 1 GPa and superliquidus temperatures of 1584-1785 K. Infrared microscopy is applied on quenched glass to measure the profile of total H2O concentration (H2Ot). The profile shape is best fit by an error function, indicating an H2O diffusivity virtually independent of H2O concentration, consistent with the results of Behrens et al. (2004) on an Fe-bearing andesite. Dehydration experiments are performed at 743-873 K in a rapid-quench cold-seal vessel, with a heated hydrous glass losing water to 0.1 GPa Ar atmosphere. Measured diffusion profiles, however, show that water diffusivity is dependent on water content. Experimental data can be explained by H2Om being the dominating diffusant or a total H2O diffusivity proportional to total H2O content. The distinction between the high-temperature experiments where H2Ot diffusivity is apparently independent of H2Ot content, and the intermediate-temperature experiments where H2Ot diffusivity depends on H2Ot can be rationalized if OH diffusion has a higher activation energy than molecular H2O diffusion, and their comparable diffusivities at high T gradually diverge as temperature is lowered. At below 1 wt.% H2O, water diffusivity increases from rhyolite to dacite to andesite at >1300C, and this sequence is reversed at <600C.

Ni, H.; Zhang, Y.

2008-12-01

412

Cavity solitons in vertical-cavity surface-emitting lasers  

E-print Network

We investigate a control of the motion of localized structures 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 localized structure 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). In the absence of the delay feedback we present experimental evidence of stationary localized structures in a 80 $\\mu$m aperture VCSEL. The spontaneous formation of localized structures takes place above the lasing threshold and under optical injection. Then, we consider the effect of the time-delayed optical feedback and investigate analytically the role of the phase of the feedback and the carrier lifetime on the self-mobility properties of the localized structures. We show that these two parameters affect strongly the space time dynamics of two-dimensional localized structures...

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

2014-01-01

413

Cavity solitons in vertical-cavity surface-emitting lasers.  

PubMed

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

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

2014-10-28

414

CAVITY-NEST WEBS IN A LONGLEAF PINE ECOSYSTEM  

Microsoft Academic Search

Cavity-nesting communities can be viewed as interconnected webs that interact through the creation of and competition for cavities as nest sites. Using a web approach, we depicted the flow of cavity creation and use in the cavity-nesting bird community of a Florida longleaf pine (Pinus palustris) ecosystem to examine the relationship between cavity-nesting bird abundance and cavity resources, and to

LORI A. BLANC; JEFFREY R. WALTERS

2008-01-01

415

Molecular diffusion into horse spleen ferritin: a nitroxide radical spin probe study.  

PubMed Central

Electron paramagnetic resonance spectroscopy and gel permeation chromatography were employed to study the molecular diffusion of a number of small nitroxide spin probes (approximately 7-9 A diameter) into the central cavity of the iron-storage protein ferritin. Charge and polarity of these radicals play a critical role in the diffusion process. The negatively charged radical 4-carboxy-2,2,6,6-tetramethylpiperidine-N-oxyl (4-carboxy-TEMPO) does not penetrate the cavity whereas the positively charged 4-amino-TEMPO and 3-(aminomethyl)-proxyl radical and polar 4-hydroxy-TEMPO radical do. Unlike the others, the apolar TEMPO radical does not enter the cavity but instead binds to ferritin, presumably at a hydrophobic region of the protein. The kinetic data indicate that diffusion is not purely passive, the driving force coming not only from the concentration gradient between the inside and outside of the protein but also from charge interactions between the diffusant and the protein. A model for diffusion is derived that describes the observed kinetics. First-order half-lives for diffusion into the protein of 21-26 min are observed, suggesting that reductant molecules with diameters considerably larger than approximately 9 A would probably enter the protein cavity too slowly to mobilize iron efficiently by direct interaction with the mineral core. PMID:8874032

Yang, X; Chasteen, N D

1996-01-01

416

Method of varying a characteristic of an optical vertical cavity structure formed by metalorganic vapor phase epitaxy  

DOEpatents

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.

Hou, Hong Q. (Albuquerque, NM); Coltrin, Michael E. (Albuquerque, NM); Choquette, Kent D. (Albuquerque, NM)

2001-01-01

417

Diffusion Confusion 8 4 Problem set #4: Fun with diffusion  

E-print Network

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

Spiegelman, Marc W.

418

Diffusion Dynamics in a Tevatron Store  

SciTech Connect

A separator failure during a store in 2002 led to a drop in luminosity, to increased emittance growth and to a drop in beam lifetimes. We show that a simple diffusion model can be used to explain the changes in beam lifetimes. Emittance growth of beams when they are in collision occurs due to many sources: beam-beam interactions, magnetic nonlinearities, intra-beam scattering, scattering off the residual gas and possibly others. The dynamics of the emittance growth is complicated and it depends strongly on the tunes. It is not always clear that the dynamics can be described by a diffusion process at all particle amplitudes in each beam. However in one store early in Run II, there was a sudden drop in a separator voltage in the Tevatron and the subsequent enhanced emittance growth and intensity lifetime drop could be described by a simple diffusion model. In this report we analyze the luminosity drop, compare the measured value with the expected drop and analyze the change in beam lifetimes. We show how a simple model of diffusive emittance growth and a change in physical aperture provides a quantitative explanation for the change in lifetimes.

Sen, Tanaji; /Fermilab

2011-09-01

419

Forward Modeling of a Coronal Cavity  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

420

Microwave cavities for vapor cell frequency standards.  

PubMed

In this paper, we report an analysis of the design criteria of microwave cavities for vapor cell frequency standards. Two main geometries exploited in those devices are considered: the cylindrical cavity, used, for example, in the coherent population trapping maser and in the pulsed optically pumped (POP) clock, and the spherical cavity used in the isotropically laser cooled clock. The cavity behavior is described through a lumped equivalent circuit in which the input coupling loop, the dielectric cell containing the atoms and the diodes for frequency tuning or Q control are taken into account. In particular, the effect of the cell on the cavity resonance frequency is analytically evaluated via a first-order perturbation approach. The theory is found in good agreement with the experiments performed with two different cylindrical cavities used for the POP clock; the model here developed can then be helpful in the design of the cavity system. The general principles here reported can be adapted to other standards, such as atomic fountains and hydrogen masers, and to other modes and/or geometries. PMID:21806210

Godone, Aldo; Micalizio, Salvatore; Levi, Filippo; Calosso, Claudio

2011-07-01

421

Localized spoof plasmons in closed textured cavities  

NASA Astrophysics Data System (ADS)

Localized spoof plasmons arising with textured closed surfaces have been theoretically studied and experimentally verified, which resemble the localized surface plasmons (LSPs) in the optical regime. In this work, we go one step further and demonstrate that part of the resonance modes in closed textured cavities pertain to spoof localized surface plasmons (spoof-LSPs) modes. We show the existence of spoof LSPs in periodically textured perfect electric conductor circular cavities and make an analogy between these spoof LSPs and the real LSPs in closed metallic cavities with the Drude model in the optical regime. Also, a metamaterial approach is presented to capture the resonant features of these modes.

Li, Zhuo; Xu, Bingzheng; Gu, Changqing; Ning, Pingping; Liu, Liangliang; Niu, Zhenyi; Zhao, Yongjiu

2014-06-01

422

Sonic crystal with open resonant cavities.  

PubMed

An improved scattering matrix method is developed to study a two-dimensional air-rigid sonic crystal with open resonant cavity, and the band structure and transmission properties are investigated. Numerical results show that both the band structure and the transmission coefficient are sensitive to the shape of the resonant cavity. The relationship between the resonant band gap and the shape of the resonant cavity is given. The high effective refractive index and the transmission ratio in the long wave range make such a system a good material for a sound lens. PMID:17358437

Hou, Zhilin; Liu, Jingtao; Kuang, Weimin; Liu, Youyan; Wu, Shuizhu

2007-02-01

423

Piezoelectric voltage coupled reentrant cavity resonator  

NASA Astrophysics Data System (ADS)

A piezoelectric voltage coupled microwave reentrant cavity has been developed. The central cavity post is bonded to a piezoelectric actuator allowing the voltage control of small post displacements over a high dynamic range. We show that such a cavity can be implemented as a voltage tunable resonator, a transducer for exciting and measuring mechanical modes of the structure, and a transducer for measuring comparative sensitivity of the piezoelectric material. Experiments were conducted at room and cryogenic temperatures with results verified using Finite Element software.

Carvalho, N. C.; Fan, Y.; Le Floch, J.-M.; Tobar, M. E.

2014-10-01

424

Strongly Coupled Magnons and Cavity Microwave Photons  

NASA Astrophysics Data System (ADS)

We realize a cavity magnon-microwave photon system in which a magnetic dipole interaction mediates strong coupling between the collective motion of a large number of spins in a ferrimagnet and the microwave field in a three-dimensional cavity. By scaling down the cavity size and increasing the number of spins, an ultrastrong coupling regime is achieved with a cooperativity reaching 12 600. Interesting dynamic features including classical Rabi-like oscillation, magnetically induced transparency, and the Purcell effect are demonstrated in this highly versatile platform, highlighting its great potential for coherent information processing.

Zhang, Xufeng; Zou, Chang-Ling; Jiang, Liang; Tang, Hong X.

2014-10-01

425

Cavity cooling of an optically trapped nanoparticle  

SciTech Connect

We study the cooling of a dielectric nanoscale particle trapped in an optical cavity. We derive the frictional force for motion in the cavity field and show that the cooling rate is proportional to the square of oscillation amplitude and frequency. Both the radial and axial components of the center-of-mass motion of the trapped particle, which are coupled by the cavity field, are cooled. This motion is analogous to two coupled but damped pendulums. Our simulations show that the nanosphere can be cooled to e{sup -1} of its initial momentum over time scales of hundredths of milliseconds.

Barker, P. F.; Shneider, M. N. [Department of Physics and Astronomy, University College London, WC1E 6BT (United Kingdom); Applied Physics Group, Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

2010-02-15

426

Multicolor quadripartite entanglement from an optomechanical cavity  

NASA Astrophysics Data System (ADS)

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 50K. 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.

Tan, Hua-Tang; Li, Gao-Xiang

2011-08-01

427

Piezoelectric voltage coupled reentrant cavity resonator.  

PubMed

A piezoelectric voltage coupled microwave reentrant cavity has been developed. The central cavity post is bonded to a piezoelectric actuator allowing the voltage control of small post displacements over a high dynamic range. We show that such a cavity can be implemented as a voltage tunable resonator, a transducer for exciting and measuring mechanical modes of the structure, and a transducer for measuring comparative sensitivity of the piezoelectric material. Experiments were conducted at room and cryogenic temperatures with results verified using Finite Element software. PMID:25362432

Carvalho, N C; Fan, Y; Le Floch, J-M; Tobar, M E

2014-10-01

428

Natural convection in a semielliptic cavity  

SciTech Connect

Natural convective steady-state motion inside a bidimensional semielliptic cavity is investigated numerically by means of a finite-element algorithm. The ceiling of the cavity is kept at a known temperature with a sinusoidal spatial distribution and the floor is assumed thermally insulated. A parametric study is carried out by varying the aspect ratio and the Grashof number. The convective motion is found to be composed of a main cell plus two small corner cells, one of which disappears at high Grashof numbers or aspects ratios. Heat is transferred mainly across the upper part of the cavity, the lower portion remaining essentially isothermal.

Del Campo, E.M.; Sen, M.; Ramos, E.

1987-01-01

429

Video System For Inspecting Walls Of Cavities  

NASA Technical Reports Server (NTRS)

Endoscopic video-imaging system generates panoramic image of part of wall of cavity surrounding tip of probe inserted in cavity. Not necessary to rotate probe to obtain panoramic image. If simple inspection without measurement required, device called "cylindrical light ring" mounted on probe to illuminate scene. Different illumination device used when required to measure distance of wall of cavity from cylindrical axis of probe. System used, for example, to inspect inner surface of tube, passage, or manifold located deep within engine or other complex structure.

Gilbert, John A.; Matthys, Donald R.

1996-01-01

430

Heat transfer in shrouded rectangular cavities  

NASA Technical Reports Server (NTRS)

Heat transfer with turbulent flow over shrouded rectangular cavities are numerically investigated. The geometry studied models flow through the clearance gap at the grooved tip of an axial turbine blade, where the blade rotates in close proximity to a stationary outer ring or shroud. The direction of relative shroud motion is always in opposition to the direction of the gas flow across the blade tip. Heat transfer characteristics and flow pattern in a cavity are found to be strongly influenced by the dimension of gap clearance, cavity geometry, and relative shroud movement.

Chyu, M. K.; Metzger, D. E.; Hwan, C. L.

1986-01-01

431

Numerical modeling of vertical cavity semiconductor lasers  

SciTech Connect

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.

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

1996-08-01

432

Population trapping due to cavity losses  

E-print Network

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.

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

2007-10-19

433

Vertical cavity surface emitting terahertz laser.  

PubMed

Vertical cavity surface emitting terahertz lasers can be realized in conventional semiconductor microcavities with embedded quantum wells in the strong coupling regime. The cavity is to be pumped optically at half the frequency of the 2p exciton state. Once a threshold population of 2p excitons is achieved, a stimulated terahertz transition populates the lower exciton-polariton branch, and the cavity starts emitting laser light both in the optical and terahertz ranges. The lasing threshold is sensitive to the statistics of photons of the pumping light. PMID:23003086

Kavokin, A V; Shelykh, I A; Taylor, T; Glazov, M M

2012-05-11

434

Properties of Cusp Diamagnetic Cavities  

NASA Technical Reports Server (NTRS)

Progress can be reported in two areas related to characterizing the properties of cusp diamagnetic cavities. Laboratory terrella experiments have been conducted for the purpose of using neutral gas excitation as a tracer of trapped electron populations in the presence of two dipoles that are used to develop a magnetic cusp topology. Figure 1 and 2 show top and side views of two configurations. Dipole trapped electron populations appear as the two luminous annular rings. Other populations are the most intense regions are shown. Interspersed between these regions are narrow regions that represent the topological cusps in these configurations. That they contain luminous gas is evidence for cusp trapping similar to what we believe exists in the terrestrial magnetosphere. The asymmetry of these cusp regions as seen in Figure 1 is the result of a relative tilt between the two dipoles suggestive of what would be expected in space. It is in these regions that particle observations were sought, so as to validate the realization of proposed and laboratory achieved trapping in a diamagnetic cusp. Figure 3 shows particle trajectories in a modeled cusp magnetic topology for three particle energies. Blue, green, and red traces correspond to increasing energies. Due to factors discussed outside of this final report, a thorough exploration of relevant satellite observations have not been achieved.

Sheldon, Robert B.

2003-01-01

435

Quantifying water diffusion in secondary organic material  

NASA Astrophysics Data System (ADS)

Recent research suggests that some secondary organic aerosol (SOA) is highly viscous under certain atmospheric conditions. This may have important consequences for equilibration timescales, SOA growth, heterogeneous chemistry and ice nucleation. In order to quantify these effects, knowledge of the diffusion coefficients of relevant gas species within aerosol particles is vital. In this work, a Raman isotope tracer method is used to quantify water diffusion coefficients over a range of atmospherically relevant humidity and temperature conditions. D2O is observed as it diffuses from the gas phase into a disk of aqueous solution, without the disk changing in size or viscosity. An analytical solution of Fick's second law is then used with a fitting procedure to determine water diffusion coefficients in reference materials for method validation. The technique is then extended to compounds of atmospheric relevance and ?-pinene secondary organic material. We produce water diffusion coefficients from 20 to 80 % RH at 23.5 C for sucrose, levoglucosan, M5AS and MgSO4. For levoglucosan we show that under conditions where a particle bounces, water diffusion in aqueous solutions can be fast (a fraction of a second for a 100 nm radius). For sucrose solutions, we also show that the Stokes-Einstein relation breaks down at high viscosity and cannot be used to predict water