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1

Thermomechanical cavity-growth modeling  

NASA Astrophysics Data System (ADS)

The results of recent field tests, laboratory studies, and modeling efforts in UCG have indicated that the thermal and mechanical properties of coal may be the controlling parameters in determining initial cavity shape. In examining this possibility, laboratory efforts have been directed at determining temperature and bedding plan dependent properties of coal. A thermomechanical model which uses these properties has indicated that the cavity shapes seen at both the Hanna and Hoe Creek test sites result from the temperature dependent properties of the coal such as the coefficients of thermal expansion and the elastic moduli. The model determines stress levels and uses a simple bedding plane dependent stress failure mechanism to determine cavity growth.

Glass, R. E.

1982-08-01

2

Momentum diffusion for coupled atom-cavity oscillators  

E-print Network

It is shown that the momentum diffusion of free-space laser cooling has a natural correspondence in optical cavities when the internal state of the atom is treated as a harmonic oscillator. We derive a general expression for the momentum diffusion which is valid for most configurations of interest: The atom or the cavity or both can be probed by lasers, with or without the presence of traps inducing local atomic frequency shifts. It is shown that, albeit the (possibly strong) coupling between atom and cavity, it is sufficient for deriving the momentum diffusion to consider that the atom couples to a mean cavity field, which gives a first contribution, and that the cavity mode couples to a mean atomic dipole, giving a second contribution. Both contributions have an intuitive form and present a clear symmetry. The total diffusion is the sum of these two contributions plus the diffusion originating from the fluctuations of the forces due to the coupling to the vacuum modes other than the cavity mode (the so called spontaneous emission term). Examples are given that help to evaluate the heating rates induced by an optical cavity for experiments operating at low atomic saturation. We also point out intriguing situations where the atom is heated although it cannot scatter light.

K. Murr; P. Maunz; P. W. H. Pinkse; T. Puppe; I. Schuster; D. Vitali; G. Rempe

2006-07-06

3

Superhydrophobicity: Cavity growth and wetting transition.  

PubMed

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

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

2015-06-15

4

Diffusion, Viscosity and Crystal Growth in Microgravity  

NASA Technical Reports Server (NTRS)

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

Myerson, Allan S.

1996-01-01

5

Calculation of the Effective Emissivities of Specular-Diffuse Cavities by the Monte Carlo Method  

Microsoft Academic Search

An algorithm of the Monte Carlo method is described which allows evaluation of the effective emissivities of isothermal and nonisothermal specular-diffuse black-body cavities for use in radiometry, photometry and optical pyrometry. The calculation provides estimates of normal spectral effective emissivity for black-body cavities, formed by cone surfaces and a cylinder. It does this for an isothermal cavity and for a

V. I. Sapritsky; A. V. Prokhorov

1992-01-01

6

Diffusion, precipitation, and cavity-wall reactions of ion-implanted gold in silicon  

SciTech Connect

The diffusion of Au in Si and its binding to cavities and precipitates of the equilibrium Au-Si phase were investigated in the temperature range 1023-1123 K using ion implantation and Rutherford backscattering spectrometry. The diffusivity-solubility product for interstitial Au was found to be about an order of magnitude greater than the extrapolation of previous, less direct determinations at higher temperatures. Chemisorption on cavity walls was shown to be more stable than Au-Si precipitation by 0.1-0.2 eV in the investigated temperature range, indicating that cavities are effective gettering centers for Au impurities.

Myers, S.M.; Petersen, G.A.

1995-12-31

7

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

8

Enhancement in Quality Factor of SRF Niobium Cavities by Material Diffusion  

E-print Network

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

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

2014-01-01

9

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 Física, Universidade Estadual de Maringá, Av. Colombo 5790, Maringá, Paraná 87020-900 (Brazil)] [Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, Maringá, Paraná 87020-900 (Brazil)

2013-12-15

10

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

11

ORIGINAL PAPER Diffusion-controlled spherulite growth in obsidian inferred  

E-print Network

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

Martin, Michael C.

12

Germanium nanowire growth controlled by surface diffusion effects  

SciTech Connect

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

Schmidtbauer, Jan; Bansen, Roman; Heimburger, Robert; Teubner, Thomas; Boeck, Torsten; Fornari, Roberto [Leibniz-Institut fuer Kristallzuechtung, Max-Born-Str. 2, 12489 Berlin (Germany)

2012-07-23

13

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

14

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

DOEpatents

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

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

1995-01-01

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

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. Based on thermodynamic modeling, we suggest that cavities grow toward the cracking criteria

Atwater, Harry

17

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

SciTech Connect

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

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

2014-02-01

18

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, 403–432]. 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

19

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

PubMed

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

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

1990-01-01

20

Grain Growth in Niobium for Superconducting Radio Frequency Cavities  

E-print Network

affecting grain growth and recrystallization: purity, temperature, and time. Several heavily cold worked samples of varying purities (99.9X% and 99.99X%) were heat treated at varying temperatures and times to reveal grain growth behavior. Results... effect of heat treatment for various times and different temperatures. Two different sample purities were tested to show how chemistry affects these heat treatment results. Initial samples The initial samples were sectioned from billets thermo...

Vernon, Joshua A.

2009-06-09

21

Formation of Cavities and Microjets in Liquids and Their Role in Initiation and Growth of Explosion  

Microsoft Academic Search

The role of discontinuities, such as bubbles of gas and cavities, in the initiation and growth of explosion in liquids has been studied experimentally by means of high speed framing photography. It is shown that micro Munroe jets can be formed at the surface of a gas bubble which has been trapped in the liquid explosive between two impacting surfaces

F. P. Bowden; M. P. McOnie

1967-01-01

22

Vertical-cavity surface-emitting lasers: Design, growth, fabrication, characterization  

Microsoft Academic Search

The authors have designed, fabricated, and tested vertical-cavity surface-emitting lasers (VCSEL) with diameters ranging from 0.5 ?m to>50 ?m. Design issues, molecular beam epitaxial growth, fabrication, and lasing characteristics are discussed. The topics considered in fabrication of VCSELs are microlaser geometries; ion implementation and masks; ion beam etching packaging and arrays, and ultrasmall devices

Jack L. Jewell; J. P. Harbison; A. Scherer; Y. H. Lee; L. T. Florez

1991-01-01

23

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

24

Signaling to the Cytoskeleton in Diffuse Cell Growth  

Microsoft Academic Search

\\u000a Non-mobile plant cells must expand to achieve its final shape. Polarized diffuse growth is a common mode of cell expansion\\u000a adopted by most plant cells, in which cell membrane expansion occurs throughout the entire cell surface while the direction\\u000a of cell expansion is spatially controlled by localized changes in cell wall extensibility. Although the mechanisms underlying\\u000a these changes are not

Ying Fu; Zhenbiao Yang

25

Applications of the theory of cavity growth to dual-ion swelling experiments  

SciTech Connect

The rate theory of cavity growth is applied to study the effects of helium gas on cavity swelling. The variation of swelling with temperature is emphasized: (1) expressions are derived showing that the primary effect of the helium is in pressurizing cavities and that a secondary effect is in altering the microstructural sink strengths. The expressions simplify in the parameter range of engineering interest such that the temperature regime of swelling is predicted to shift upward in approximately direct proportion to the cavity gas pressure; (2) recent experimental data on swelling of a pure stainless steel type alloy under dual-nickel and helium-ion bombardment is interpreted. Helium-free, helium-coimplanted, and helium-preimplanted swelling results can be explained by the theory. It is necessary to account for the partitioning of the helium to dislocations as well as to cavities in order to explain the experimental results for helium coimplantation; (3) model studies for physically reasonable parameters reveal the importance of the He/dpa ratio.

Hayns, M.R.; Mansur, L.K.

1980-01-01

26

Structure of S-shaped growth in innovation diffusion  

NASA Astrophysics Data System (ADS)

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

Shimogawa, Shinsuke; Shinno, Miyuki; Saito, Hiroshi

2012-05-01

27

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

2012-04-27

28

A molecular dynamics investigation of the diffusion characteristics of cavity-type zeolites with 8-ring windows  

SciTech Connect

Molecular dynamics (MD) simulations are used to investigate the diffusion characteristics in DDR, CHA, LTA, ITQ-29, and TSC zeolites that have cavities separated by 8-member ring windows of dimensions in the 3.4–4.6 Å range. These zeolites have potential usage for separation of a variety of mixtures, such as CO{sub 2}/CH{sub 4}, CO{sub 2}/H{sub 2}, H{sub 2}/CH{sub 4}, and propane/propene, relying on a combination of adsorption and diffusion selectivities. The magnitude of self-diffusivities, D{sub i,self}, of the CH{sub 4} is found to have a direct correlation with the size of the window opening, increasing by about two orders of magnitude for a 0.5 Å increase in the window aperture. The diffusion selectivities of CO{sub 2}/CH{sub 4}, and H{sub 2}/CH{sub 4} mixtures were also found to have direct, and strong, correlation, with the window aperture. This opens up the possibility of tuning diffusion selectivities by appropriate choice of the framework structure. Framework flexibility dynamics have also been investigated with the aid of two published force fields for all-silica zeolites. Due to the lattice vibrations there is a distribution of window sizes that varies with time. The diffusivity of CH4 for a flexible lattice was found to correlate with aperture size of the time-averaged window, in precisely the same manner as for fixed framework lattices. This leads to the conclusion that lattice flexibility, per se, has no influence on the magnitude of the diffusivity or diffusion selectivity.

Krishna, Rajamani; van Baten, Jasper M

2011-01-01

29

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

E-print Network

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

Cone, Michael Thomas

2014-04-16

30

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

31

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

SciTech Connect

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

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

2007-11-02

32

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

33

Measurement of Lateral Diffusion in Silicon and Stress Effects on Epitaxial Growth  

E-print Network

Measurement of Lateral Diffusion in Silicon and Stress Effects on Epitaxial Growth A thesis Author Michael J. Aziz Jennifer Nicole Fues Sage Measurement of Lateral Diffusion in Silicon and Stress was measured using Scanning Capacitance Microscopy (SCM). The observed diffusivity compares favor- ably

34

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

35

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

36

Rapid growth of congenital diffuse brain tumor considered to be teratoma: case report.  

PubMed

Prenatal ultrasonography of a 17-year-old pregnant female detected ventriculomegaly of the fetus at 31 weeks of gestation. Her medical and family histories were unremarkable. Fetal magnetic resonance imaging taken at 33 weeks of gestation showed a tumorous lesion with ventriculomegaly. A male baby was delivered by cesarean section at 36 weeks of gestation. The Apgar scores were 9 and 9 at 1 and 5 minutes after the delivery, respectively. The head circumference at birth was 41.5 cm with bulging anterior fontanel, but no other congenital anomaly. He showed relatively good activity with satisfactory feeding. Computed tomography performed on postnatal day 5 revealed a massive brain tumor of mixed density, with multiple lobulation and cystic and calcified components. The tumor had rapidly grown with diffuse appearance. The patient underwent endoscopic biopsy with installation of an Ommaya reservoir to control the hydrocephalus on postnatal day 6. The tumor appeared hypervascular and bled profusely on resection maneuver, so the endoscopic procedure for histological verification was abandoned. Cerebrospinal fluid taken intraoperatively revealed marked elevation of the alpha-fetoprotein level and mild increase of the human chorionic gonadotropin level, strongly suggestive of teratoma. Neuroimaging performed on postnatal day 11 indicated significant additional tumor growth which occupied nearly the whole cranial cavity. His activity began to deteriorate on postnatal day 13 and he died of respiratory distress on the 15th day of life. PMID:18654054

Tsutsumi, Satoshi; Kondo, Akihide; Yasumoto, Yukimasa; Ito, Masanori

2008-07-01

37

Interferometric measurements of a dendritic growth front solutal diffusion layer  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

38

Increased diffuse radiation fraction does not significantly accelerate plant growth  

NASA Astrophysics Data System (ADS)

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

Angert, Alon; Krakauer, Nir

2010-05-01

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

Cunningham, Philip; Naftalin, Richard J

2014-11-01

40

Size diffusion for the growth of newly nucleated aerosol  

Microsoft Academic Search

Size diffusion is often regarded as a problem encountered with the numerical solution of the general dynamic equation for aerosols. We investigate here the real size diffusion arising in the solution of the more fundamental discrete rate equations, which treat condensation and evaporation on a molecular basis. The spreading of the aerosol distribution in molecular number content is obtained from

Charles F. Clement; Kari E. J. Lehtinen; Markku Kulmala

2004-01-01

41

Increased diffuse radiation fraction does not significantly accelerate plant growth  

Microsoft Academic Search

A recent modelling study (Mercado et al., 2009) claims that increased numbers of scattering aerosols are responsible for a substantial fraction of the terrestrial carbon sink in recent decades because higher diffuse light fraction enhances plant net primary production (NPP). Here we show that observations of atmospheric CO2 seasonal cycle and tree ring data indicate that the relation between diffuse

Alon Angert; Nir Krakauer

2010-01-01

42

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

43

Diffusion in the titanium-nickel system: I. occurrence and growth of the various intermetallic compounds  

Microsoft Academic Search

Various types of diffusion couples have been prepared and the growth of the layers, formed in these couples, has been studied\\u000a in the temperature range between 550 and 940C. All phases which, on the basis of the equilibrium diagram, could be expected\\u000a under the circumstances, were found in the diffusion zone. The layer growth of ?-Ti(Ni), Ti2Ni and TiNi in

G. F. Bastin; G. D. Rieck

1974-01-01

44

Boundary-layer analysis for the convection/diffusion transition in dendritic growth  

NASA Technical Reports Server (NTRS)

The supercooling dependence of dendritic growth kinetics under the influence of convective heat transport is investigated theoretically and experimentally with emphasis on theoretical prediction of the supercooling level at which the transition from diffusion-controlled to convection-controlled dendritic growth occurs. It is shown that the crossover between diffusive and convective transport depends on the relative thickness of the Stefan length compared with the thermal boundary layer. These lengths become equal at a supercooling which may be calculated from diffusion theory and fluid mechanics. It is also shown that the crossover supercooling varies weakly with the gravitational acceleration, melt viscosity, and the volumetric expansion coefficient.

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

1981-01-01

45

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

46

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.

Mandrà, Salvatore; Lagomarsino, Marco Cosentino; Gherardi, Marco

2014-09-01

47

DETERMINATION OF DIFFUSION LENGTH AND THE AVERAGE ENERGY REQUIREMENT FOR THE FORMATION OF ELECTRON-CAVITY PAIRS BY X IRRADIATION OF PN BARRIER LAYERS  

Microsoft Academic Search

A measurement method is described, which is used to determine the x-ray-; induced p-n transitions and diffusion length as well as the average energy ; requirements for formation of electron-cavity pairs. It is necessary for ; irradiation with monochromatic x radiation at two different wavelengths to ; measure the ratio of the striking radiation to the short-circuit current of the

Pfister

1963-01-01

48

Number of growth sites for diffusion at the percolation threshold  

NASA Astrophysics Data System (ADS)

The effective exponent for d=2 describing how the number of growth sites depends on the cluster size is found to depend on the ``ensemble'' used, i.e., whether the number of visited sites or the number of time steps is kept constant. The constant-site ensemble supports the Leyvraz-Stanley prediction, while the constant-time ensemble supports the Aharony-Stauffer prediction for the growth-site fractal dimension.

Demme, E. Sebastian

1986-04-01

49

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

50

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

51

Morphological Instability and Dynamics of Fronts in Bacterial Growth Models with Nonlinear Diffusion  

E-print Network

It has been argued that there is biological and modeling evidence that a non-linear diffusion coefficient of the type D(b) = D_0 b^{k} underlies the formation of a number of growth patterns of bacterial colonies. We study a reaction-diffusion system with a non-linear diffusion coefficient introduced by Ben-Jacob et al. Due to the fact that the bacterial diffusion coefficient vanishes when the bacterial density b -> 0, the standard linear stability analysis for fronts cannot be used. We introduce an extension of the stability analysis which can be applied to such singular fronts, map out the region of stability in the D-k-plane and derive an interfacial approximation in some limits. Our linear stability analysis and sharp interface formulation will also be applicable to other examples of interface formation due to nonlinear diffusion, like in porous media or in the problem of vortex motion in superconductors.

J. Mueller; W. van Saarloos

2002-11-21

52

Measurement of the diffusivity of CdTe in liquid Te at crystal growth temperatures  

NASA Astrophysics Data System (ADS)

The diffusivity of CdTe in tellurium-rich liquid solution was measured by dissolving solid samples at temperatures applicable to THM crystal growth. We calculated the resulting diffusion coefficients to be 0.008mm2 / s at 850 °C and 0.009mm2 / s at 900 °C. The CdTe was dissolved under isothermal conditions in 7 mm diameter quartz tubes for 45 min, 90 min and 180 min. The diffusivity was calculated from the distance travelled by the dissolution interface using a 1D transport model. Measurement of the solution composition by EDS confirms that the experiments were diffusion-dominated, and the calculated diffusivities match those predicted elsewhere ab initio for similar conditions.

Roszmann, J.; Sekhon, M.; Dost, S.

2015-02-01

53

Application of diffusion growth chambers for the cultivation of marine sponge-associated bacteria.  

PubMed

Marine sponges contain dense and diverse microbial communities, which are renowned as a source of bioactive metabolites. The biological activities of sponge-microbe natural products span a broad spectrum, from antibacterial and antifungal to antitumor and antiviral applications. However, the potential of sponge-derived compounds has not been fully realized, due largely to the acknowledged "supply issue." Most bacteria from environmental samples have resisted cultivation on artificial growth media, and cultivation of sponge-associated bacteria has been a major focus in the search for novel marine natural products. One approach to isolate so-called "uncultivable" microorganisms from different environments is the diffusion growth chamber method. Here, we describe the first application of diffusion growth chambers for the isolation of cultivable and previously uncultivated bacteria from sponges. The study was conducted by implanting diffusion growth chambers in the tissue of Rhabdastrella globostellata reef sponges. In total, 255 16S rRNA gene sequences were obtained, with phylogenetic analyses revealing their affiliations with the Alpha- and Gammaproteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes. Fifteen sequences represented previously uncultivated bacteria belonging to the Bacteroidetes and Proteobacteria (Alpha and Gamma classes). Our results indicate that the diffusion growth chamber approach can be successfully applied in a natural, living marine environment such as sponges. PMID:24838766

Steinert, Georg; Whitfield, Susanna; Taylor, Michael W; Thoms, Carsten; Schupp, Peter J

2014-10-01

54

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

55

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

56

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

57

On the theory of dendritic growth: Soret and temperature-dependent diffusion effects  

NASA Astrophysics Data System (ADS)

An analytical solution is found for the problem of the growth of an isolated dendrite in a convective binary melt with allowance for the Soret and temperature-dependent diffusion effects. Nonlinear impurity transport is shown to radically change the impurity concentration in front of the growing crystal and, correspondingly, the concentration supercooling, which is responsible for the condition of choosing the dendrite tip growth rate.

Alexandrov, D. V.; Pinigin, D. A.

2013-02-01

58

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

Microsoft Academic Search

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

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

2001-01-01

59

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

SciTech Connect

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{sup ?15} (cm{sup 2}/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., E-mail: seyyed-nima.nateghi@polymtl.ca; Ménard, D.; Masut, R. A. [Regroupement québécoise sur les matériaux de pointe (RQMP), Département de Génie Physique, Polytechnique Montréal, C.P. 6079, succ. Centre-ville, Montréal, Québec H3C 3A7 (Canada)

2014-10-07

60

Compact or fractal patterns in diffusion limited growth  

NASA Astrophysics Data System (ADS)

Fractal viscous fingering patterns are observed in an infinite Hele-Shaw cell at long times when the capillary forces become negligible. On the contrary, growth of monocrystals from a punctual seed shows dendrites growing independently in 4 or 6 directions, according to the crystal symmetry. A close comparison of numerical and experimental data explains first the origin of the tip-splitting instability in radial growth and shows that it can be inhibited by the anisotropy of surface tension. Des structures fractales ont été observées en digitations visqueuses en cellule de Hele-Shaw et aux temps longs lorsque les forces capillaires deviennent négligeables. Par opposition, la croissance de monocristaux à partir d'un germe ponctuel fait apparaître des dendrites croissant dans 4 ou 6 directions selon la symétrie cristalline. Une comparaison entre des résultats numériques et des données expérimentales explique l'origine de l'instabilité de dédoublement des pointes en croissance radiale et montre qu'elle peut être supprimée par l'anisotropie cristalline.

Ben Amar, Martine

1993-02-01

61

An Innovative Method for Preparing Semiconductor Change Used in Crystal Growth and Shear Cell Diffusion Experiments  

NASA Technical Reports Server (NTRS)

An innovative technique for machining semiconductors has been developed. This technique was used to prepare semiconductor charges for crystal growth and shear cell diffusion experiments. The technique allows brittle semiconductor materials to be quickly and accurately machined. Lightly doping the semiconductor material increases the conductivity enough to allow the material to be shaped by an electrical discharge machine (EDM).

Anrold, William A.; Matthiesen, David; Benett, Robert J.; Jayne, Douglas T.

1997-01-01

62

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

NASA Technical Reports Server (NTRS)

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

Zefiro, L.

1980-01-01

63

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

64

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

SciTech Connect

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

Sibirev, N. V., E-mail: NickSibirev@yandex.ru; Tchernycheva, M.; Cirlin, G. E. [Russian Academy of Sciences, St. Petersburg Academic University, Nanotechnology Research and Education Center (Russian Federation); Patriarche, G.; Harmand, J. C. [CNRS-LPN (France); Dubrovskii, V. G. [Russian Academy of Sciences, St. Petersburg Academic University, Nanotechnology Research and Education Center (Russian Federation)

2012-06-15

65

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.

2012-07-19

66

Damage removal and boron diffusion during solid phase epitaxial growth of SiGe alloy layers  

NASA Astrophysics Data System (ADS)

SiGe/Si heterostructures have been fabricated using germanium ion implantation into silicon and subsequent solid phase epitaxy (SPE) growth. The damage removal and boron diffusion in the SiGe/Si heterostructures formed by high-dose Ge + preamorphized and BF 2+ implanted Si(0 0 1) during SPE growth have been investigated by double-crystal X-ray diffraction (DCXRD) and secondary ion mass spectrometry (SIMS). The results show that annealing at 600°C for 60 min can only remove a little damage induced by implantation and nearly no redistribution of Ge and B atoms has occurred during the annealing. Most damage induced by Ge + and BF 2+ ion implantation have been removed after annealing at 950°C for 60 min and accompanied by Ge diffusion, a boron diffusion has taken place. When annealing temperature rose to 1050°C, Ge diffusion has been slight while B diffusion has been deeper into the Si substrate with a very good distribution. The X-ray diffraction (0 0 4) rocking curves from the samples annealed at 1050°C for 60 min display two SiGe peaks, which may be related to the B and Ge concentration profiles.

Zou, L.-F.; Acosta-Ortiz, S. E.; Zou, LuXin; Luna, R. E.; Perez-Herrera, G. A.; Regalado, L. E.

1999-04-01

67

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 µm. Important differences were identified in the spectral features between specular reflection and diffuse scattering which will impact most practical testing scenarios and complicate material identification. We discuss some of the factors influencing the dependence of observed spectra on the experimental geometry.

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

2012-09-01

68

The diffusion model is not a deterministic growth model: comment on Jones and Dzhafarov (2014).  

PubMed

Jones and Dzhafarov (2014) claim that several current models of speeded decision making in cognitive tasks, including the diffusion model, can be viewed as special cases of other general models or model classes. The general models can be made to match any set of response time (RT) distribution and accuracy data exactly by a suitable choice of parameters and so are unfalsifiable. The implication of their claim is that models like the diffusion model are empirically testable only by artificially restricting them to exclude unfalsifiable instances of the general model. We show that Jones and Dzhafarov's argument depends on enlarging the class of "diffusion" models to include models in which there is little or no diffusion. The unfalsifiable models are deterministic or near-deterministic growth models, from which the effects of within-trial variability have been removed or in which they are constrained to be negligible. These models attribute most or all of the variability in RT and accuracy to across-trial variability in the rate of evidence growth, which is permitted to be distributed arbitrarily and to vary freely across experimental conditions. In contrast, in the standard diffusion model, within-trial variability in evidence is the primary determinant of variability in RT. Across-trial variability, which determines the relative speed of correct responses and errors, is theoretically and empirically constrained. Jones and Dzhafarov's attempt to include the diffusion model in a class of models that also includes deterministic growth models misrepresents and trivializes it and conveys a misleading picture of cognitive decision-making research. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:25347314

Smith, Philip L; Ratcliff, Roger; McKoon, Gail

2014-10-01

69

Non-linear resonance of fluids in a crystal growth cavity  

NASA Technical Reports Server (NTRS)

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

Wang, Francis C.

1996-01-01

70

Nucleation and growth by diffusion under Ostwald-Freundlich boundary condition  

SciTech Connect

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

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

2014-02-14

71

Inferring the effect of therapies on tumor growth by using diffusion processes.  

PubMed

Modeling the effect of therapies in cancer animal models remains a challenge. This point may be addressed by considering a diffusion process that models the tumor growth and a modified process that includes, in its infinitesimal mean, a time function modeling the effect of the therapy. In the case of a Gompertz diffusion process, where a control group and one or more treated groups are examined, a methodology to estimate this function has been proposed by Albano et al. (2011). This method has been applied to infer the effect of cisplatin and doxorubicin+cyclophosphamide on breast cancer xenografts. Although this methodology can be extended to other diffusion processes, it has an important restriction: it is necessary that a known diffusion process adequately fits the control group. Here, we propose the use of a stochastic process for a hypothetical control group, in such a way that both the control and the treated groups can be modeled by modified processes of the former. Thus, the comparison between models would allow estimating the real effect of the therapy. The new methodology has been validated by inferring the effects in breast cancer models, and we have checked the robustness of the procedure against the choice of stochastic model for the hypothetical control group. Finally, we have also applied the methodology to infer the effect of a therapeutic peptide and ovariectomy on the growth of a breast cancer xenograft, and its efficiency in modeling the effect of different treatments in the absence of control group data is shown. PMID:22906590

Román-Román, Patricia; Torres-Ruiz, Francisco

2012-12-01

72

Size distribution of islands according to 2D growth model with 2 kinds of diffusion atoms  

E-print Network

We simulated the growth of 2D islands with 2 kinds of diffusion atoms using the kinetic Monte- Carlo (kMC) method. As a result, we found that the slow atoms tend to create nuclei and determine the island volume distribution, along with additional properties such as island density. We also conducted a theoretical analysis using the rate equation of the point-island model to confirm these results.

Yamauchi, R; Koyama, M; Sasakura, H; Nakata, Y; Muto, S

2015-01-01

73

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

Microsoft Academic Search

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

Erin L. O’Brien; Russell D. Dawson

2008-01-01

74

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

PubMed Central

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 diffusion measures, namely, linear (Cl) and planar (Cp) diffusion anisotropies, from 71 longitudinal datasets acquired from 29 healthy, full-term pediatric subjects. The growth trajectories were estimated with generalized estimating equations (GEE) using linear fitting with logarithm of age (days). The presence of the white matter structures in Cl and Cp was observed in neonates, suggesting that both the cylindrical and fanning or crossing structures in various white matter regions may already have been formed at birth. Moreover, we found that both Cl and Cp evolved in a temporally nonlinear and spatially inhomogeneous manner. The growth velocities of Cl in central white matter were significantly higher when compared to peripheral, or more laterally located, white matter: central growth velocity Cl = 0.0465±0.0273/log(days), versus peripheral growth velocity Cl=0.0198±0.0127/log(days), p<10?6. In contrast, the growth velocities of Cp in central white matter were significantly lower than that in peripheral white matter: central growth velocity Cp= 0.0014±0.0058/log(days), versus peripheral growth velocity Cp = 0.0289±0.0101/log(days), p<10?6. Depending on the underlying white matter site which is analyzed, our findings suggest that ongoing physiologic and microstructural changes in the developing brain may exert different effects on the temporal evolution of these two geometrical diffusion measures. Thus, future studies utilizing DTI with correlative histological analysis in the study of early brain development are warranted. PMID:21784163

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

2011-01-01

75

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

PubMed

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

Matsuo, Isao; Kimura-Yoshida, Chiharu

2014-12-01

76

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 1–10 cm was small, much smaller than the sampling uncertainty on the value of . Moreover, could either increase or decrease when class width increased depending on the species. Overall, even if the class width should be kept small enough to limit diffusion, it had little impact on the estimate of for tree species. PMID:24905941

Picard, Nicolas; Liang, Jingjing

2014-01-01

77

Matrix models for size-structured populations: unrealistic fast growth or simply diffusion?  

PubMed

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 i to class i + 1, ? was independent of the class width when the mortality and the recruitment rates were constant, irrespective of the growth rate. We also showed that if there were indeed fast pathways, there were also in about the same proportion slow pathways (i.e. the fraction of individuals that systematically remained in the same class), and that they jointly act as a diffusion process (where diffusion here is the movement in size of an individual whose size increments are random according to a normal distribution with mean zero). For 53 tree species from a tropical rain forest in the Central African Republic, the diffusion resulting from common matrix dimensions was much stronger than would be realistic. Yet, the sensitivity of ? to matrix dimension for a class width in the range 1-10 cm was small, much smaller than the sampling uncertainty on the value of ?. Moreover, ? could either increase or decrease when class width increased depending on the species. Overall, even if the class width should be kept small enough to limit diffusion, it had little impact on the estimate of ? for tree species. PMID:24905941

Picard, Nicolas; Liang, Jingjing

2014-01-01

78

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

79

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

PubMed

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

O'Brien, Erin L; Dawson, Russell D

2008-01-01

80

Analysis of Oxidation Enhanced and Retarded Diffusions and Growth of Oxidation Stacking Fault in Silicon  

NASA Astrophysics Data System (ADS)

In order to determine the fractional components of the interstitialcy mechanism for Sb, P and self-diffusions, dISb, dIP and dIsd, and the supersaturation ratios of vacancies and self-interstitials, sV and sI, from the experimental results of the oxidation-enhanced diffusion (OED) of P, oxidation-retarded diffusion (ORD) of Sb and growth of the interstitial-type stacking fault by oxidation (OSF), the equations of OED, ORD and OSF and of the special relation between sV and sI were solved simultaneously. The effect of the stacking fault energy upon growth of the OSF was taken into account in the OSF equation. As the experimental results of OED, ORD and OSF did not satisfy their equations exactly, nine kinds of solutions were obtained and three of them were shown. The errors caused by the lack of exact satisfaction were shown. A dIsd much smaller than 0.5 was obtained.

Yoshida, Masayuki

1988-06-01

81

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

82

Diffusion-Controlled, Self-Organized Growth of Symmetric Wrinkling Patterns  

NASA Astrophysics Data System (ADS)

The formation of self-organized wrinkling patterns is a potential route for generating such tunable ordered patterns on surfaces across many length scales. Here, we demonstrate that surface wrinkling of ultraviolet/ozone (UVO) treated polymer films through osmotically driven swelling by solvent vapor sorption leads to unique and intriguing patterns, some of which have not been previously reported. The type of pattern and speed of its growth is coupled to the degree of UVO crosslinking and the rate of solvent diffusion into the film from a localized defect. This simple yet novel approach could serve as a test-bed for studying topography-driven phenomena such as wettability and adhesion and diffusion related processes, as well as facilitate a better understanding of dynamic self-assembly.

Stafford, Christopher M.; Chung, Jun Young; Nolte, Adam J.

2009-03-01

83

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

E-print Network

Diffusion processes are accompanied by the appearance of non-equilibrium fluctuations, whose size distribution on Earth is strongly affected by the gravity force. In microgravity and at steady state, these fluctuations exhibit generic scale invariance and their size is only limited by the finite dimension of the system. In this work, we investigate experimentally and computationally the development of non-equilibrium fluctuations during a thermophoretic process in microgravity. Both experiments and simulations show that during the onset of fluctuations the scale invariance is present at large wave vectors. In a broader range of wave vectors simulations predict a spinodal-like growth of fluctuations, where the amplitude and length scale of the dominant mode are determined by the thickness of the diffuse layer.

Roberto Cerbino; Yifei Sun; Aleksandar Donev; Alberto Vailati

2015-02-12

84

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

85

Fractal growth in uv-irradiated DNA: Evidence of nonuniversal diffusion limited aggregation  

NASA Astrophysics Data System (ADS)

Branched structures and fractals occur widely in nature (trees, corals, sand dunes, etc.) showing its preference for nonintegral dimensionality characteristic of nonequilibrium growth phenomena [B. B. Mandelbrot, The Fractal Geometry of Nature (Freeman, New York, 1982)]. Neural networks, blood platelets, some cancerous growth patterns, etc. are also known examples of fractals in physiological systems. Many theoretical models have been invoked to explain different fractal and ramified structures [T. Vicsek, Fractal Growth Phenomena (World Scientific, Singapore, 1989)]. The diffusion limited aggregation (DLA) of particles in a random walk that was computer simulated by Witten and Sander [T. A. Witten and L. M. Sander, Phys. Rev. Lett. 47, 1400 (1981)] is a more universal mechanism. Recently, a nonuniversal DLA has been theoretically proposed [P. Ossadnik, C. Lam, and L. M. Sander, Phys. Rev. E 49, 1788 (1994)] where particles in a random walk are not of the same size. This paper reports the significant observation that uv-photolyzed DNA in an alkaline solution aggregates, on drying, in a fractal-like structure. Furthermore, this observation provides experimental confirmation of nonuniversal diffusion limited aggregation [P. Ossadnik, C. Lam, and L. M. Sander, Phys. Rev. E 49, 1788 (1994)].

Chandra, Amita; Shukla, M. K.; Mishra, P. C.; Chandra, S.

1995-04-01

86

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

NASA Astrophysics Data System (ADS)

The effects of cluster diffusion on the submonolayer island density and island-size distribution are studied for the case of irreversible growth of compact islands on a 2D substrate. In our model we assume instantaneous coalescence of circular islands, while the cluster mobility is assumed to exhibit power-law decay as a function of island size with exponent ?. Results are presented for ?=1/2,1, and 3/2 corresponding to cluster diffusion via Brownian motion, correlated evaporation condensation, and edge diffusion respectively, as well as for higher values including ?=2,3, and 6. We also compare our results with those obtained in the limit of no cluster mobility (?=?). In agreement with theoretical predictions of power-law behavior of the island-size distribution (ISD) for ?<1, for ?=1/2 we find Ns(?)~s-? [where Ns(?) is the number of islands of size s at coverage ?] up to a crossover island-size Sc. However, the value of the exponent ? obtained in our simulations is higher than the mean-field (MF) prediction ?=(3-?)/2. Similarly, the measured value of the exponent ? corresponding to the dependence of Sc on the average island-size S (e.g., Sc~S?) is also significantly higher than the MF prediction ?=2/(?+1). A generalized scaling form for the ISD [Ns(?)=?/S1+??f(s/S?)] is also proposed for ?<1, and using this form excellent scaling is found for ?=1/2. However, for finite ??1 neither the generalized scaling form nor the standard scaling form Ns(?)=?/S2f(s/S) lead to scaling of the entire ISD for finite values of the ratio R of the monomer diffusion rate to deposition flux. Instead, the scaled ISD becomes more sharply peaked with increasing R and coverage. This is in contrast to models of epitaxial growth with limited cluster mobility for which good scaling occurs over a wide range of coverages.

Kryukov, Y. A.; Amar, Jacques G.

2011-04-01

87

Solid-phase diffusion mechanism for GaAs nanowire growth  

NASA Astrophysics Data System (ADS)

Controllable production of nanometre-sized structures is an important field of research, and synthesis of one-dimensional objects, such as nanowires, is a rapidly expanding area with numerous applications, for example, in electronics, photonics, biology and medicine. Nanoscale electronic devices created inside nanowires, such as p-n junctions, were reported ten years ago. More recently, hetero-structure devices with clear quantum-mechanical behaviour have been reported, for example the double-barrier resonant tunnelling diode and the single-electron transistor. The generally accepted theory of semiconductor nanowire growth is the vapour-liquid-solid (VLS) growth mechanism, based on growth from a liquid metal seed particle. In this letter we suggest the existence of a growth regime quite different from VLS. We show that this new growth regime is based on a solid-phase diffusion mechanism of a single component through a gold seed particle, as shown by in situ heating experiments of GaAs nanowires in a transmission electron microscope, and supported by highly resolved chemical analysis and finite element calculations of the mass transport and composition profiles.

Persson, Ann I.; Larsson, Magnus W.; Stenström, Stig; Ohlsson, B. Jonas; Samuelson, Lars; Wallenberg, L. Reine

2004-10-01

88

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

NASA Astrophysics Data System (ADS)

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

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

89

Quantifying the effect of turbulent magnetic diffusion on the growth rate of the magneto-rotational instability  

E-print Network

In astrophysics, turbulent diffusion is often used in place of microphysical diffusion to avoid resolving the small scales. However, we expect this approach to break down when time and length scales of the turbulence become comparable with other relevant time and length scales in the system. Turbulent diffusion has previously been applied to the magneto-rotational instability (MRI), but no quantitative comparison of growth rates at different turbulent intensities has been performed. We investigate to what extent turbulent diffusion can be used to model the effects of small-scale turbulence on the kinematic growth rates of the MRI, and how this depends on angular velocity and magnetic field strength. We use direct numerical simulations in three-dimensional shearing boxes with periodic boundary conditions in the spanwise direction and additional random plane-wave volume forcing to drive a turbulent flow at a given length scale. We estimate the turbulent diffusivity using a mixing length formula and compare with...

Väisälä, M S; Mitra, Dhrubaditya; Käpylä, P J; Mantere, M J

2013-01-01

90

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

91

North-south trade-related technology diffusion, brain drain and productivity growth : are small states different ?  

Microsoft Academic Search

The economies of small developing states tend to be more fragile than those of large ones. Thispaper examines this issue in a dynamic context by focusing on the impact of the brain drain on North-South trade-related technology diffusion and total factor productivity growth in small and large states in the South. There are three main findings. First, productivity growth increases

Maurice Schiff; Yanling Wang

2009-01-01

92

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

E-print Network

Growth of Ultralong ZnS/SiO2 Core-Shell Nanowires by Volume and Surface Diffusion VLS Process information regarding growth dynamics. After a systematic study on the structure, we propose that the core-shell at the tips of the nanowires and completely encased by a silica shell. Photoluminescence (PL) measurements

Wang, Zhong L.

93

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

94

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

95

Thermal diffusion dominated dendritic growth — an analysis of the wall proximity effect  

NASA Astrophysics Data System (ADS)

It is demonstrated that using a simple correction to the original Ivantsov solution to account for wall proximity effects is sufficient to describe the Peclet number microgravity data of Glicksman et al. [M.E. Glicksman, M.B. Koss and E.A. Winsa, Phys. Rev. Lett. 73 (1994) 573; M.E. Glicksman, M.B. Koss, L.T. Bushnell, J.C. LaCombe and E.A. Winsa, ISLJ International 35 (1995) 1216; MRS Fall Meeting, Symp. P, Boston MA, 1995, in press] at low supercooling. The analytical correction provides for the enhanced diffusive heat transfer when the thermal diffusion length becomes comparable to the physical chamber dimension. The wall proximity effect is also responsible for the existence of a lower supercooling limit below which the dendrite cannot grow in a steady-state manner. It is concluded that Glicksman's USMP-2 microgravity data is thermal diffusion dominated and thus entirely appropriate for comparison with dendritic growth theories.

Pines, Vladimir; Chait, Arnon; Zlatkowski, Marianne

1996-09-01

96

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

NASA Technical Reports Server (NTRS)

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

Izmailov, Alexander F.; Myerson, Allan S.

1995-01-01

97

A solid-liquid diffusion model for growth and dissolution of ternary alloys by liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

This paper presents a solid-liquid diffusion model for ternary alloys formed by liquid phase epitaxy (LPE). A fully numerical procedure is developed to simulate the growth and dissolution processes. The simulation results for the Al?Ga?As system show that the growth rate and the solid composition are functions of the growth temperature and the cooling rate. The computed solid composition and growth thickness are compared with available experimental data. The numerical and experimental results are in good agreement. The computational model developed in this study is suitable for simulations of solution growth of ternary alloys.

Kimura, M.; Qin, Z.; Dost, S.

1996-01-01

98

Transformation of stable glasses into supercooled liquids: growth fronts and anomalously fast liquid diffusion.  

PubMed

Physical vapor deposition onto substrates near 0.85T(g) can prepare organic glasses with low enthalpy, high density, and high thermal stability. Isotopically labeled multilayer films of tris(naphthyl)benzene and indomethacin stable glasses were prepared and secondary ion mass spectrometry was used to study the evolution of these materials upon heating above T(g). In contrast to ordinary glasses, when stable glasses are held above T(g) they transform to a liquid via a growth front mechanism. In these experiments, growth fronts are initiated at the free surface of the glass and in some cases at the glass/substrate interface or an internal interface in the glass. For tris(naphthyl)benzene, the velocity of this growth front is observed to be nearly independent of the stability of the glass. Diffusion in the liquid that results from the growth front is initially 2-5 times faster than for the equilibrium supercooled liquid at the same temperature; the nature of this liquid is unclear. Under some circumstances, the slow evolution of this unusually mobile liquid into the equilibrium supercooled liquid can be observed. PMID:20141127

Swallen, Stephen F; Windsor, Katherine; McMahon, Robert J; Ediger, M D; Mates, Thomas E

2010-03-01

99

Interlesion differences in the local photodynamic therapy response of oral cavity lesions assessed by diffuse optical spectroscopies.  

PubMed

Photodynamic therapy (PDT) efficacy depends on the local dose deposited in the lesion as well as oxygen availability in the lesion. We report significant interlesion differences between two patients with oral lesions treated with the same drug dose and similar light dose of 2-1[hexyloxyethyl]-2-devinylpyropheophorbide-a (HPPH)-mediated photodynamic therapy (PDT). Pre-PDT and PDT-induced changes in hemodynamic parameters and HPPH photosensitizer content, quantified by diffuse optical methods, demonstrated substantial differences between the two lesions. The differences in PDT action determined by the oxidative cross-linking of signal transducer and activator of transcription 3 (STAT3), a molecular measure of accumulated local PDT photoreaction, also showed >100-fold difference between the lesions, greatly exceeding what would be expected from the slight difference in light dose. Our results suggest diffuse optical spectroscopies can provide in vivo metrics that are indicative of local PDT dose in oral lesions. PMID:23024908

Rohrbach, Daniel J; Rigual, Nestor; Tracy, Erin; Kowalczewski, Andrew; Keymel, Kenneth L; Cooper, Michele T; Mo, Weirong; Baumann, Heinz; Henderson, Barbara W; Sunar, Ulas

2012-09-01

100

Quantifying the effect of turbulent magnetic diffusion on the growth rate of the magneto-rotational instability  

NASA Astrophysics Data System (ADS)

Context. In astrophysics, turbulent diffusion is often used in place of microphysical diffusion to avoid resolving the small scales. However, we expect this approach to break down when time and length scales of the turbulence become comparable with other relevant time and length scales in the system. Turbulent diffusion has previously been applied to the magneto-rotational instability (MRI), but no quantitative comparison of growth rates at different turbulent intensities has been performed. Aims: We investigate to what extent turbulent diffusion can be used to model the effects of small-scale turbulence on the kinematic growth rates of the MRI, and how this depends on angular velocity and magnetic field strength. Methods: We use direct numerical simulations in three-dimensional shearing boxes with periodic boundary conditions in the spanwise direction and additional random plane-wave volume forcing to drive a turbulent flow at a given length scale. We estimate the turbulent diffusivity using a mixing length formula and compare with results obtained with the test-field method. Results: It turns out that the concept of turbulent diffusion is remarkably accurate in describing the effect of turbulence on the growth rate of the MRI. No noticeable breakdown of turbulent diffusion has been found, even when time and length scales of the turbulence become comparable with those imposed by the MRI itself. On the other hand, quenching of turbulent magnetic diffusivity by the magnetic field is found to be absent. Conclusions: Turbulence reduces the growth rate of the MRI in the same way as microphysical magnetic diffusion does. Appendix A is available in electronic form at http://www.aanda.org

Väisälä, M. S.; Brandenburg, A.; Mitra, D.; Käpylä, P. J.; Mantere, M. J.

2014-07-01

101

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

102

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.

103

Graphene Growth and Carbon Diffusion Process during Vacuum Heating on Cu(111)/Al2O3 Substrates  

NASA Astrophysics Data System (ADS)

In this study, the behavior of carbon atoms in the annealing/cooling process of graphene/Cu(111) substrates is investigated using photoelectron spectroscopy and secondary ion mass spectroscopy. After the growth of graphene on Cu(111) surfaces, Cu2O was formed at the graphene/Cu interface during transportation through air atmosphere. The Cu2O layer completely disappeared by vacuum annealing at 500 °C. Graphene was decomposed and carbon atoms diffused into the Cu substrate by further elevation of annealing temperature to 950 °C. When the sample was cooled down, the carbon atoms did not segregate on the surface and remained in the Cu substrate. This result indicates the carbon atoms easily diffuse into Cu substrates in vacuum annealing while the amount of diffused carbon atoms in the thermal chemical vapor deposition (CVD) process is smaller, suggesting that the barrier layer, which prevents the diffusion of C atoms, exists on Cu surfaces in the graphene CVD growth.

Ogawa, Shuichi; Yamada, Takatoshi; Ishidzuka, Shinji; Yoshigoe, Akitaka; Hasegawa, Masataka; Teraoka, Yuden; Takakuwa, Yuji

2013-11-01

104

A dual-phase-lag diffusion model for predicting thin film growth  

NASA Astrophysics Data System (ADS)

A dual-phase-lag diffusion (DPLD) model, which extends Fick's law by including two lagging times, icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/> j for the mass flux vector and icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/> icons/Journals/Common/rho" ALT="rho" ALIGN="MIDDLE"/> for the density gradient, is developed to predict thin film growth. Depending upon the phase lag ratio icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/> icons/Journals/Common/rho" ALT="rho" ALIGN="MIDDLE"/> /icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/> j , the DPLD model uniquely characterizes four types of growth kinetics as reported in the literature. The model validation with experimental data of silicon oxidation and Hg1-x Cdx Te film deposition demonstrates that the present model captures the anomalous behaviour of thin film growth from the very beginning of the process to relatively long times very well.

Chen, J. K.; Beraun, J. E.; Tzou, D. Y.

2000-03-01

105

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

PubMed

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

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

2013-12-01

106

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2007-01-01

108

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

PubMed

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

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

2015-02-10

109

The effects of plasma diffusion and viscosity on turbulent instability growth  

SciTech Connect

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

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

2014-09-15

110

Numerical model of protein crystal growth in a diffusive field such as the microgravity environment  

PubMed Central

It is said that the microgravity environment positively affects the quality of protein crystal growth. The formation of a protein depletion zone and an impurity depletion zone due to the suppression of convection flow were thought to be the major reasons. In microgravity, the incorporation of molecules into a crystal largely depends on diffusive transport, so the incorporated molecules will be allocated in an orderly manner and the impurity uptake will be suppressed, resulting in highly ordered crystals. Previously, these effects were numerically studied in a steady state using a simplified model and it was determined that the combination of the diffusion coefficient of the protein molecule (D) and the kinetic constant for the protein molecule (?) could be used as an index of the extent of these depletion zones. In this report, numerical analysis of these depletion zones around a growing crystal in a non-steady (i.e. transient) state is introduced, suggesting that this model may be used for the quantitative analysis of these depletion zones in the microgravity environment. PMID:24121357

Tanaka, Hiroaki; Sasaki, Susumu; Takahashi, Sachiko; Inaka, Koji; Wada, Yoshio; Yamada, Mitsugu; Ohta, Kazunori; Miyoshi, Hiroshi; Kobayashi, Tomoyuki; Kamigaichi, Shigeki

2013-01-01

111

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

E-print Network

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 $r(t) \\propto \\kappa (t-t_1)^{\\beta/2}$, 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 GOES and AIA/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 ($\\beta=0.53\\pm0.27$), 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 $v=15\\pm12$ km s$^{-1}$, with maximum speeds of $v_{max}=80 \\pm 85$ km s$^{-1}$ per flare, which is substantially slower than the sonic ...

Aschwanden, Markus J

2012-01-01

112

Rate-equation approach to irreversible island growth with cluster diffusion  

NASA Astrophysics Data System (ADS)

A self-consistent rate-equation (RE) approach to irreversible island growth and nucleation is presented which takes into account the effects of cluster mobility. As a first application we consider the irreversible growth of compact islands on a 2D surface in the presence of monomer deposition (with rate F) and monomer diffusion (with rate D1) while the mobility of an island of size s is assumed to satisfy Ds= D1s^-? where ?>=0. For coverages up to the peak island-density, we find excellent agreement between our RE and simulation results for the dependence of the island-density N(?) on coverage ? for all values of ? considered, ranging from ?= 1/2 (Brownian motion) to ?= ? (immobile clusters). For ?<=2, excellent agreement is also found between our simulation and RE results for the island-size distribution (ISD), while for higher values of ? the effects of correlations become important. We also demonstrate that the discrepancies between recent theoretical predictions for the exponents ?(?) and ?(?) describing the size-dependence of the ISD for ?< 1 and simulations can be explained by the geometry of compact islands. Our self-consistent RE approach may also be generalized to higher dimensions as well as to an arbitrary dependence of the cluster mobility on island-size.

Hubartt, Bradley; Kryukov, Yevgen; Amar, Jacques

2011-03-01

113

Diagnostic accuracy of diffuse reflectance imaging for early detection of pre-malignant and malignant changes in the oral cavity: a feasibility study  

PubMed Central

Background Diffusely reflected light is influenced by cytologic and morphologic changes that take place during tissue transformation, such as, nuclear changes, extracellular matrix structure and composition as well as blood flow. Albeit with varying degree of sensitivity and specificity, the properties of diffusely reflected light in discriminating a variety of oral lesions have been demonstrated by our group in multiple studies using point monitoring systems. However, the point monitoring system could not identify the region with the most malignant potential in a single sitting. Methods In order to scan the entire lesion, we developed a multi-spectral imaging camera system that records diffuse reflectance (DR) images of the oral lesion at 545 and 575 nm with white light illumination. The diagnostic accuracy of the system for 2-dimensional DR imaging of pre-malignant and malignant changes in the oral cavity was evaluated through a clinical study in 55 patients and 23 healthy volunteers. The DR imaging data were compared with gold standard tissue biopsy and histopathology results. Results In total 106- normal/clinically healthy sites, 20- pre-malignant and 29- malignant (SCC) sites were compared. While the median pixel value of the R545/R575 image ratio for normal/clinically healthy tissue was 0.87 (IQR?=?0.82-0.94), they were 1.35 (IQR?=?1.13-1.67) and 2.44 (IQR?=?1.78-3.80) for pre-malignant and malignant lesions, respectively. Area under the ROC curve to differentiate malignant from normal/clinically healthy [AUC?=?0.99 (95% CI: 0.99-1.00)], pre-malignant from normal/clinically healthy [AUC?=?0.94 (95% CI: 0.86-1.00)], malignant from pre-malignant [AUC?=?0.84 (95% CI: 0.73-0.95)] and pre-malignant and malignant from normal/clinically healthy [AUC?=?0.97 (95% CI: 0.94-1.00)] lesions were desirable. Conclusion We find DR imaging to be very effective as a screening tool in locating the potentially malignant areas of oral lesions with relatively good diagnostic accuracy while comparing it to the gold standard histopathology. PMID:23738507

2013-01-01

114

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

Microsoft Academic Search

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 \\

Flemming Besenbacher

1997-01-01

115

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

116

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

117

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

NASA Astrophysics Data System (ADS)

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

Xiao, Lin; Wang, Ning

2015-01-01

118

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

NASA Astrophysics Data System (ADS)

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

Rempel, A. W.

2011-10-01

119

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

120

Critical Analysis of Dry Storage Temperature Limits for Zircaloy-Clad Spent Nuclear Fuel Based on Diffusion Controlled Cavity Growth  

SciTech Connect

Interim dry storage of spent nuclear fuel (SNF) rods is of critical concern because a shortage of existing SNF wet storage capacity combined with delays in the availability of a permanent disposal repository has led to an increasing number of SNF rods being placed into interim dry storage. Safe interim dry storage must be maintained for a minimum of twenty years according to the Standard Review Plan for Dry Cask Storage Systems [1] and the Code of Federal Regulations, 10 CFR Part 72 [2]. Interim dry storage licensees must meet certain safety conditions when storing SNF rods to ensure that there is a ''very low probability (e.g. 0.5%) of cladding breach during long-term storage'' [1]. Commercial SNF typically consists of uranium oxide pellets surrounded by a thin cladding. The cladding is usually an {alpha}-zirconium based alloy know as ''Zircaloy''. In dry storage, the SNF rods are confined in one of several types of cask systems approved by the Nuclear Regulatory Commission (NRC). ''The cask system must be designed to prevent degradation of fuel cladding that results in a type of cladding breach, such as axial-splits or ductile fracture, where irradiated UO{sub 2} particles may be released. In addition, the fuel cladding should not degrade to the point where more than one percent of the fuel rods suffer pinhole or hairline crack type failure under normal storage conditions [1].'' The NRC has approved two models [3,4] for use by proposed dry storage licensees to determine the maximum initial temperature limit for nuclear fuel rods in dry storage that supposedly meet the above criteria and yield consistent temperature limits. Though these two models are based on the same fundamental failure theory, different assumptions have been made including the choice of values for material constants in the failure equation. This report will examine and compare the similarities and inconsistencies of these two models. It will illustrate some of the shortcomings of the current models and suggest modifications as well as some experiments that should be started in the near future. This report will also discuss changes in the current NRC standards with regard to the adoption of a strain-based model to be used to determine maximum allowable temperatures of the SNF.

Hayes, T.A.; Rosen, R.S.; Kassner, M.E.

1999-12-01

121

Critical Analysis of Dry Storage Temperature Limits for Zircaloy-Clad Spent Nuclear Fuel Based on Diffusion Controlled Cavity Growth  

Microsoft Academic Search

Interim dry storage of spent nuclear fuel (SNF) rods is of critical concern because a shortage of existing SNF wet storage capacity combined with delays in the availability of a permanent disposal repository has led to an increasing number of SNF rods being placed into interim dry storage. Safe interim dry storage must be maintained for a minimum of twenty

T. A. Hayes; R. S. Rosen; M. E. Kassner

1999-01-01

122

The origins and development of the diffusion of innovations paradigm as an example of scientific growth.  

PubMed

Diffusion is the process by which an innovation is communicated through certain channels over time among members of a social system. The diffusion of innovations is a communication theory which has laid the groundwork for behavior change models across the social sciences, representing a widely applicable perspective. The diffusion of innovations paradigm began with the 1943 publication of the results of an hybrid seed corn study conducted by Bryce Ryan and Neal C. Gross, rural sociologists at Iowa State University. The diffusion paradigm spread among midwestern rural sociological researchers in the 1950s and 1960s, and then to a larger, interdisciplinary field of diffusion scholars. By the late 1960s, rural sociologists lost interest in diffusion studies, not because it was ineffective scientifically, but because of lack of support for such study as a consequence of farm overproduction and because most of the interesting research questions were thought to be answered. Since 1943, more than 4000 research publications have appeared and diffusion research became a widely practiced variety of scholarly study in sociology and other social sciences. This paper describes some of the history of rural sociological research on the diffusion of agricultural innovations with the goal of understanding how the research tradition emerged and to determine how it influenced the larger body of diffusion research conducted later by scholars in other disciplinary specialties. The authors describe how diffusion of innovations research followed and deviated from the Kuhnian concept of paradigm development. PMID:12319357

Valente, T W; Rogers, E M

1995-03-01

123

Diffusion length improvements in GaAs associated with Zn diffusion during Ga/1-x/Al/x/As growth  

NASA Technical Reports Server (NTRS)

Relatively good GaAs solar cells can be made from poor quality substrates by making the junction deep (more than 1 micron) instead of shallow and by leaching both the p and n GaAs regions during the growth process. Air-mass-zero efficiencies of 14.7% (19% AM1) have been obtained from substrates with starting substrate thickness of 0.6 micron.

Hovel, H. J.; Woodall, J. M.

1975-01-01

124

X-ray diffuse scattering study of the kinetics of stacking fault growth and annihilation in boron-implanted silicon  

NASA Astrophysics Data System (ADS)

Stacking faults in boron-implanted silicon give rise to streaks or rods of scattered x-ray intensity normal to the stacking fault plane. We have used the diffuse scattering rods to follow the growth of faults as a function of time when boron-implanted silicon is annealed in the range of 925 to 1025 degC. From the growth kinetics we obtain an activation energy for interstitial migration in silicon: EI=1.98plus-or-minus0.06 eV. Fault intensity and size versus time results indicate that faults do not shrink and disappear, but rather are annihilated by a dislocation reaction mechanism.

Luebbert, D.; Arthur, J.; Sztucki, M.; Metzger, T. H.; Griffin, P. B.; Patel, J. R.

2002-10-01

125

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

126

The effect of diffusive transport of bedload particles in selecting the wavelength of sand ripples during their initial growth  

NASA Astrophysics Data System (ADS)

We revisit the classic problem of wavelength selection of sand ripples during their initial growth from a planar bed. This involves reworking the analysis of [Smith, 1970] to incorporate the effects of a diffusive term in the Exner equation, as recently described by [Furbish et al., 2009], in order to determine whether a preferred wave number occurs for ripple growth in a flow with low Froude number. We hypothesize that, instead of a monotonically increasing rate of growth of ripples with respect to increasing wave number [Smith, 1970; Richards 1980], there is a finite preferred wave number for peak growth rate primarily due to the effect of the diffusive term, which is to suppress the growth of high wave numbers (small wavelengths). That is, our objective is to show that this curve reaches a maximum and then declines with increasing wave number. Following Smith's analysis, we work with a two-dimensional nonuniform flow field assuming sinusoidal ripple forms, and re-derive the Orr-Sommerfeld equation by linearizing and expanding the momentum equations. We then endeavor to solve the simplified Orr-Sommerfeld equation (which assumes constant eddy viscosity) to approximate the bed stress conditions in order to evaluate the terms of the modified Exner equation. Qualitative analysis suggests that a preferred wave number occurs, and we compare our hypothesis with experimental data.

Kahn, B. P.; Furbish, D. J.

2010-12-01

127

Realistic Simulation of the 3D Growth of Brain Tumors in MR Images Coupling Diffusion with Biomechanical Deformation  

PubMed Central

We propose a new model to simulate the 3D growth of glioblastomas multiforma (GBMs), the most aggressive glial tumors. The GBM speed of growth depends on the invaded tissue: faster in white than in gray matter, it is stopped by the dura or the ventricles. These different structures are introduced into the model using an atlas matching technique. The atlas includes both the segmentations of anatomical structures and diffusion information in white matter fibers. We use the finite element method (FEM) to simulate the invasion of the GBM in the brain parenchyma and its mechanical interaction with the invaded structures (mass effect). Depending on the considered tissue, the former effect is modeled with a reaction-diffusion or a Gompertz equation, while the latter is based on a linear elastic brain constitutive equation. In addition, we propose a new coupling equation taking into account the mechanical influence of the tumor cells on the invaded tissues. The tumor growth simulation is assessed by comparing the in-silico GBM growth with the real growth observed on two magnetic resonance images (MRIs) of a patient acquired with six months difference. Results show the feasibility of this new conceptual approach and justifies its further evaluation. PMID:16229419

Clatz, Olivier; Sermesant, Maxime; Bondiau, Pierre-Yves; Delingette, Hervé; Warfield, Simon K.; Malandain, Grégoire; Ayache, Nicholas

2006-01-01

128

Growth and diffusion of e-journal usage in universities of the western Himalayan region of India  

Microsoft Academic Search

Purpose – The purpose of this paper is to study and analyse the information communication technology-based growth and diffusion of research using e-journals for two universities belonging to different states in the western Himalayan region of India. Design\\/methodology\\/approach – The paper uses an assessment period for the analysis of usage of e-journals of 36 months from 2007-2009. It demonstrates a

Dhirendra Sharma; Hemant Sharma; Vikram Singh

2011-01-01

129

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

130

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

131

Sliding-cavity fluid contactors in low-gravity fluids, materials, and biotechnology research.  

PubMed

The well-known method of sliding-cavity fluid contactors used by Gosting for diffusion measurements and by Tiselius in electrophoresis has found considerable use in low-gravity research. To date, sliding-cavity contactors have been used in liquid diffusion experiments, interfacial transport experiments, biomolecular crystal growth, biphasic extraction, multistage extraction, microencapsulation, seed germination, invertebrate development, and thin-film casting. Sliding-cavity technology has several advantages for spaceflight: it is simple, it accommodates small samples, samples can be fully enclosed, phases can be combined, multiple samples can be processed at high sample density, real-time observations can be made, and mixed and diffused samples can be compared. An analysis of the transport phenomena that govern the sliding-cavity method is offered. During sliding of one liquid over another flow rates between 0.001 and 0.1m/sec are developed, giving Reynolds numbers in the range 0.1-100. Assuming no slip at liquid-solid boundaries shear rates are of the order 1sec(-1). The measured consequence is the transfer of 2-5% of the content of a cavity to the opposite cavity. In the absence of gravity, buoyancy-driven transport is assumed absent. Transport processes are limited to (1) molecular diffusion, in which reactants diffuse toward one another at rates that depend on their diffusion coefficient and concentration gradient (Fick's second law), (2) solutocapillary (Marangoni) flow driven by surface-tension gradients, (3) capillary flow (drop spreading) at liquid-solid three-phase lines leading to immiscible phase demixing, and (4) vapor-phase diffusive mass transfer in evaporative processes. Quantitative treatment of these phenomena has been accomplished over the past few years in low-gravity research in space and on aircraft. PMID:12446349

Todd, Paul; Vellinger, John C; Sengupta, Shramik; Sportiello, Michael G; Greenberg, Alan R; Krantz, William B

2002-10-01

132

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

E-print Network

Morphological instability and dynamics of fronts in bacterial growth models with nonlinear the growth of bacterial colonies under different growth conditions has been the focus of attention of several Leiden, The Netherlands Received 26 November 2001; published 28 June 2002 Depending on the growth

van Saarloos, Wim

133

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

134

Cavity QED in Quantum Dot - Micropillar Cavity Systems  

Microsoft Academic Search

\\u000a In this contribution we review our recent work on cavity quantum electrodynamics experiments (cQED) with single quantum dots\\u000a in high quality micropillar cavities. After a short introduction to the theoretical background of cQED with single two level\\u000a emitters, important aspects in the growth and patterning of quantum dot–micropillar cavities will be addressed in the second\\u000a part of this review. In

S. Reitzenstein; A. Forchel

2009-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

136

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 ?tVcr(t)/mp=2.69×10-1?t1.10. Furthermore, the scaled crater volume, ?V = Vcr_final?t/mp, where Vcr_final is the final crater cavity volume, ?t is the target density, and mp is the projectile mass, was successfully fitted by a power law equation when another scaling parameter was used for the crater formation in strength regime, ?Y=Yt/?tvi2, where Yt is the target material strength, as follows: ?V=1.69×10-1?Y-0.51. As a result, the crater formed on porous gypsum was revealed to be more than one order of magnitude smaller than that formed on basalt. Based on our experimental results, which visualize how crater cavities on porous cohesive materials grow with projectile penetration, we are able to discuss compression and excavation processes during crater formation quantitatively. This observation enables us to investigate and revise numerical models and crater scaling laws for high-velocity impacts into porous cohesive materials.

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

2012-11-01

137

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

138

Coordinated Development of Yeast Colonies: Quantitative Modeling of Diffusion-Limited Growth Part 2  

E-print Network

scaled to the growth of Yarrowia lipolytica and Candida boidinii colonies under carbon and nitrogen and the applied yeast species. In those cases for which the DLG hypothesis failed to explain the observed growth

Montresor, Alberto

139

Oxidation-enhanced or retarded diffusion and the growth or shrinkage of oxidation-induced stacking faults in silicon  

NASA Astrophysics Data System (ADS)

An analysis of the conditions for obtaining oxidation-enhanced or retarded dopant diffusions (OED or ORD), in accordance with the stacking fault growth/shrinkage phenomena, is carried out for the oxidation of Si by assuming that vacancy and Si self-interstitials coexist at high temperatures and that during oxidation a local equilibrium of point defects is attained. It is shown that the Sb ORD data can be explained quantitatively. Under most oxidation conditions the SiO2-Si interface acts as a source of Si self-interstitials, but at sufficiently high temperatures and long oxidation times the SiO2-Si interface behaves as a sink for Si self-interstitials (or equivalently as a source of vacancies). We suggest a model for this sink behavior in terms of the formation of SiO molecules at the interface and of their subsequent diffusion into the SiO2 film.

Tan, T. Y.; Gösele, U.

1982-04-01

140

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

141

Discerning crystal growth from diffusion profiles in zoned olivine by in situ Mg–Fe 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 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

2013-01-01

142

A short-time diffusion correlation for hydrogen-induced crack growth kinetics  

Microsoft Academic Search

Analysis of hydrogen-stress field interactions have led to kinetic criteria for slow crack growth. Using both elastic and\\u000a plastic stress fields under opening-mode loading, criteria for stage I, II, III growth are developed in terms of the pressure\\u000a tensor gradient at the crack tip. It is proposed that stage I (stress-intensity dependent) growth kinetics are predominantly\\u000a controlled by the elastic

W. W. Gerberich; Y. T. Chen; C. S. T. John

1975-01-01

143

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

E-print Network

to be independent of the flow rate and turbulence in the medium. In addition we report the development of a diffuse reflector which, to our best knowledge, has the highest measured diffuse reflectivity of 0.998 at 532 nm and 0.996 at 266 nm. We also show...

Musser, Joseph Alan

2007-04-25

144

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

E-print Network

in all components, heat radiation between surfaces, internal radiation as well as convection in the melt by a macroscopic heat transfer model in the entire crystal growth system, taking into account heat conduction

Bebendorf, Mario

145

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

146

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

NASA Astrophysics Data System (ADS)

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 700°C. 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.

Kpetsu, Jean-Baptiste A.; Jedrzejowski, Pawel; Côté, Claude; Sarkissian, Andranik; Mérel, Philippe; Laou, Philips; Paradis, Suzanne; Désilets, Sylvain; Liu, Hao; Sun, Xueliang

2010-03-01

147

Stabilized second-order convex splitting schemes for Cahn-Hilliard models with application to diffuse-interface tumor-growth models.  

PubMed

We present unconditionally energy-stable second-order time-accurate schemes for diffuse-interface (phase-field) models; in particular, we consider the Cahn-Hilliard equation and a diffuse-interface tumor-growth system consisting of a reactive Cahn-Hilliard equation and a reaction-diffusion equation. The schemes are of the Crank-Nicolson type with a new convex-concave splitting of the free energy and an artificial-diffusivity stabilization. The case of nonconstant mobility is treated using extrapolation. For the tumor-growth system, a semi-implicit treatment of the reactive terms and additional stabilization are discussed. For suitable free energies, all schemes are linear. We present numerical examples that verify the second-order accuracy, unconditional energy-stability, and superiority compared with their first-order accurate variants. PMID:24023005

Wu, X; van Zwieten, G J; van der Zee, K G

2014-02-01

148

Cavity optomechanics  

NASA Astrophysics Data System (ADS)

The field of cavity optomechanics is reviewed. This field explores the interaction between electromagnetic radiation and nanomechanical or micromechanical motion. This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation-pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity-quantum-optomechanics experiments. In addition, the perspectives for fundamental quantum physics and for possible applications of optomechanical devices are described.

Aspelmeyer, Markus; Kippenberg, Tobias J.; Marquardt, Florian

2014-10-01

149

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

2015-04-01

150

Formal asymptotic limit of a diffuse-interface tumor-growth  

E-print Network

Eindhoven, Multiscale Engineering Fluid Dynamics, Gem-Z 3.136, PO Box 513, 5600 MB Eindhoven, Netherlands (k.g.v is referred to as avas- cular growth, as the tumor has not yet acquired its own blood supply to nurture itself) and has a natural four- constituent interpretation: a tumorous phase u 1, a healthy cell phase u -1

Paris-Sud XI, Université de

151

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

E-print Network

for fabricating monodisperse nano- particles critical for a wide range of applications. Ã? 2013 Elsevier Inc. All launched by Samsung Electronics [3]. NPs and their com- posites [4] have also been widely investigated the nucleation and growth stages of NP formation. LaMer and Dinegar proposed that there is a minimum degree

Krishnan, Kannan M.

152

Direct growth of bilayer graphene on SiO? substrates by carbon diffusion through nickel.  

PubMed

Here we report a transfer-free method of synthesizing bilayer graphene directly on SiO(2) substrates by carbon diffusion through a layer of nickel. The 400 nm nickel layer was deposited on the top of SiO(2) substrates and used as the catalyst. Spin-coated polymer films such as poly(methyl methacrylate), high-impact polystyrene or acrylonitrile-butadiene-styrene, or gas-phase methane were used as carbon sources. During the annealing process at 1000 °C, the carbon sources on the top of the nickel decomposed and diffused into the nickel layer. When cooled to room temperature, bilayer graphene was formed between the nickel layer and the SiO(2) substrates. The nickel films were removed by etchants, and bilayer graphene was then directly obtained on SiO(2), eliminating any transfer process. The bilayer nature of the obtained graphene films on SiO(2) substrates was verified by Raman spectroscopy and transmission electron microscopy. The Raman spectroscopy mapping over a 100 × 100 ?m(2) area indicated that the obtained graphene is high-quality and bilayer coverage is approximately 70%. PMID:21888426

Peng, Zhiwei; Yan, Zheng; Sun, Zhengzong; Tour, James M

2011-10-25

153

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

154

Defect- and Strain-enhanced Cavity Formation and Au Precipitation at nano-crystalline ZrO2/SiO2/Si Interfaces  

SciTech Connect

Defect- and strain-enhanced cavity formation and Au precipitation at the interfaces of a nanocrystalline ZrO2/SiO2/Si multilayer structure resulting from 2 MeV Au+ irradiation at temperatures of 160 and 400 K have been studied. Under irradiation, loss of oxygen is observed, and the nanocrystalline grains in the ZrO2 layer increase in size. In addition, small cavities are observed at the ZrO2/SiO2 interface with the morphology of the cavities being dependent on the damage state of the underlying Si lattice. Elongated cavities are formed when crystallinity is still retained in the heavily-damaged Si substrate; however, the morphology of the cavities becomes spherical when the substrate is amorphized. With further irradiation, the cavities appear to become stabilized and begin to act as gettering sites for the Au. As the cavities become fully saturated with Au, the ZrO2/SiO2 interface then acts as a gettering site for the Au. Analysis of the results suggests that oxygen diffusion along the grain boundaries contributes to the growth of cavities and that oxygen within the cavities may affect the gettering of Au. Mechanisms of defect- and strain-enhanced cavity formation and Au precipitation at the interfaces will be discussed with focus on oxygen diffusion and vacancy accumulation, the role of the lattice strain on the morphology of the cavities, and the effect of the binding free energy of the cavities on the Au precipitation.

Edmondson, Philip D.; Zhang, Yanwen; Namavar, Fereydoon; Wang, Chong M.; Zhu, Zihua; Weber, William J.

2011-01-15

155

Defect- and strain-enhanced cavity formation and Au precipitation at nano-crystalline ZrO2/SiO2/Si interfaces  

SciTech Connect

Defect- and strain-enhanced cavity formation and Au precipitation at the interfaces of a nano-crystalline ZrO{sub 2}/SiO{sub 2}/Si multilayer structure resulting from 2 MeV Au{sup +} irradiation at temperatures of 160 and 400 K have been studied. Under irradiation, loss of oxygen is observed, and the nano-crystalline grains in the ZrO{sub 2} layer increase in size. In addition, small cavities are observed at the ZrO{sub 2}/SiO{sub 2} interface with the morphology of the cavities being dependent on the damage state of the underlying Si lattice. Elongated cavities are formed when crystallinity is still retained in the heavily-damaged Si substrate; however, the morphology of the cavities becomes spherical when the substrate is amorphized. With further irradiation, the cavities appear to become stabilized and begin to act as gettering sites for the Au. As the cavities become fully saturated with Au, the ZrO{sub 2}/SiO{sub 2} interface then acts as a gettering site for the Au. Analysis of the results suggests that oxygen diffusion along the grain boundaries contributes to the growth of cavities and that oxygen within the cavities may affect the gettering of Au. Mechanisms of defect- and strain-enhanced cavity formation and Au precipitation at the interfaces will be discussed with focus on oxygen diffusion and vacancy accumulation, the role of the lattice strain on the morphology of the cavities, and the effect of the binding free energy of the cavities on the Au precipitation.

Edmondson, Philip D [ORNL; Zhang, Yanwen [ORNL; Namavar, Fereydoon [University of Nebraska Medical Center; Wang, Chongmin [Pacific Northwest National Laboratory (PNNL); Zhu, Zihua [Pacific Northwest National Laboratory (PNNL); Weber, William J [ORNL

2011-01-01

156

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

157

Micropropagation of Potato: Evaluation of Closed, Diffusive and Forced Ventilation on Growth and Tuberization  

Microsoft Academic Search

Different types of ventilation of the culture vessel headspace, each with and without the ethylene inhibitor AgNO3(3.0?M) or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) (2.0?M) in the culture medium, were investigated in terms of their effects on the growth of potato cuttings (Solanum tuberosum L. ‘cara’). Concentrations of CO2, O2and ethylene in the culture vessel headspaces were monitored during the

S. M. A. Zobayed; J. Armstrong; W. Armstrong

2001-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

159

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

SciTech Connect

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

Fan, D.; Geng, C.; Chen, L.Q. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering] [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

1997-03-01

160

Annals of Biomedical Engineering, Vol. 32, No. 5, May 2004 (2004) pp. 645663 A Reaction-Diffusion Model of Basic Fibroblast Growth Factor  

E-print Network

-Diffusion Model of Basic Fibroblast Growth Factor Interactions with Cell Surface Receptors RENEE J. FILION and is expressed in many cultured cell types including fibroblasts, endothelial cells, smooth muscle cells such as cancer, atherosclerosis, and heart and limb ischemia, as well as normal wound healing and tissue

Popel, Aleksander S.

2004-01-01

161

Verification of a Model to Calculate Cooling Rates in Olivine by Consideration of Fe-Mg Diffusion and Olivine Crystal Growth  

Microsoft Academic Search

We developed a model to analyze chemical zoning in olivine based on Fe-Mg diffusion during olivine crystal growth to obtain the cooling rate. We verify this model by using Fe-Mg zoning in olivine produced by dynamic crystallization experiments.

M. Miyamoto; R. H. Jones; E. Koizumi; T. Mikouchi

2005-01-01

162

Verification of a Model to Calculate Cooling Rates in Olivine by Consideration of Fe-Mg Diffusion and Olivine Crystal Growth, II  

Microsoft Academic Search

We developed a model to calculate the olivine cooling rate by analyzing zoning on the basis of Fe-Mg diffusion during crystal growth. We verify this model by using zoning profiles produced by dynamic crystallization for Martian and lunar meteorites.

M. Miyamoto; E. Koizumi; T. Mikouchi

2006-01-01

163

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

164

Spatially Quantifying Microscopic Tumor Invasion and Proliferation Using a Voxel-Wise Solution to a Glioma Growth Model and Serial Diffusion MRI  

PubMed Central

The purpose of the current study was to develop a voxel-wise analytical solution to a glioma growth model using serial diffusion MRI. These cell invasion, motility, and proliferation level estimates (CIMPLE maps) provide quantitative estimates of microscopic tumor growth dynamics. After an analytical solution was found, noise simulations were performed to predict the effects that perturbations in apparent diffusion coefficient (ADC) values and the time between ADC map acquisitions would have on the accuracy of CIMPLE maps. CIMPLE maps were then created for 53 patients with gliomas with WHO grades of II–IV. MR spectroscopy estimates of the Cho/NAA ratio were compared to cell proliferation estimates in CIMPLE maps using Pearson’s correlation analysis. Median differences in cell proliferation and diffusion rates between WHO grades were compared. A strong correlation (R2 = 0.9714) and good spatial correspondence were observed between MR spectroscopy measurements of the Cho/NAA ratio and CIMPLE map cell proliferation rate estimates. Estimates of cell proliferation and diffusion rates appear to be significantly different between low (WHO II) and high-grade (WHO III–IV) gliomas. Cell diffusion rate (motility) estimates are highly dependent on the time interval between ADC map acquisitions, whereas cell proliferation rate estimates are additionally influenced by the level of noise present in ADC maps. PMID:21413079

Ellingson, Benjamin M.; LaViolette, Peter S.; Rand, Scott D.; Malkin, Mark G.; Connelly, Jennifer M.; Mueller, Wade M.; Prost, Robert W.; Schmainda, Kathleen M.

2010-01-01

165

Diffuse reflectance spectroscopy: diagnostic accuracy of a non-invasive screening technique for early detection of malignant changes in the oral cavity  

PubMed Central

Background Strong proof-of-principle for utilisation of diffuse reflectance spectroscopy, a non-invasive tool for early detection of malignant changes, has emerged recently. The potential of this technique in distinguishing normal tissue from hyperplastic and dysplastic tissues was explored. Methods Diffuse reflectance (DR) spectra in the 400–700?nm region were obtained from the buccal mucosa of 96 patients and 34 healthy volunteers. The DR spectral data were compared against the gold standard biopsy and histopathology results. A principal-component analysis was performed for dimensional reduction in the normalised spectral data with linear discriminant analysis as the classifying technique. The receiver operator characteristic curve technique was employed for evaluating the performance of the diagnostic test. Results DR spectral features for different lesions, such as normal/healthy, hyperplastic, dysplastic and squamous cell carcinoma (SCC), varied significantly according to the intensity of oxygenated haemoglobin absorption. While the classification based on discriminant scores provided an overall sensitivity of 98.5% and specificity of 96.0% for distinguishing SCC from dysplasia, they were 100.0% and 95.0%, respectively, for distinguishing dysplasia from hyperplasia. Similarly, the analysis yielded a sensitivity of 95.0% and specificity of 100.0% for distinguishing hyperplasia from healthy tissue. The areas under the receiver operator characteristic curves were 0.98 (95% CI 0.95 to 1.00) and 0.95 (95% CI 0.90 to 1.00) for distinguishing dysplasia from SCC and hyperplasia from dysplasia, respectively. Conclusion DR spectral data efficiently discriminate healthy tissue from oral malignant lesions. Diagnostic accuracies obtained in this study highlight the potential use of this method for routine clinical practice. PMID:22021749

Jayanthi, J L; Nisha, G U; Manju, S; Philip, E K; Jeemon, P; Baiju, K V; Beena, V T

2011-01-01

166

A thin interface asymptotic for a phase-field model of epitaxial growth with different adatom diffusivities  

NASA Astrophysics Data System (ADS)

Here we extend a phase-field model for epitaxial step-flow growth originally derived by Liu and Metiu to capture the case of different adatom diffusivities at neighboring terraces as well as an arbitrary Ehrlich-Schwoebel (ES) barrier. Our extended model approach bridges the atomic to continuum scale in the sense that it takes into account atomic attachment kinetics in full detail and likewise allows to simulate long range transport processes above the surface efficiently. To verify the model we present a matched asymptotic analysis of the derived model equations, which shows that in a special limit the presented model can be related to the Burton-Cabrera-Frank (BCF) model with different kinds of attachment coefficients at either side of a step edge. We demonstrate the capability of our approach by presenting numerical simulations with an Ehrlich-Schwoebel (ES) barrier, which reproduce the well-known step meandering instability. Thereby we show how mathematical analysis helps to specify and validate a phase-field model and thus contributes to the further development of this modeling approach at the nano- to microscale.

Kundin, J.; Hubert, J.; Emmerich, H.

2009-10-01

167

Void Nucleation, Growth and Coalescence in Irradiated Metals  

SciTech Connect

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

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

2008-01-11

168

Synchronization in an optomechanical cavity  

NASA Astrophysics Data System (ADS)

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

2015-03-01

169

In-pile Xe diffusion coefficient in UO 2 determined from the modeling of intragranular bubble growth and destruction under irradiation  

NASA Astrophysics Data System (ADS)

Intragranular bubbles grow in the nuclear fuel by diffusion and precipitation of fission gases, mainly xenon; and are ultimately destroyed, under irradiation, by fission fragments. This article will attempt to determine the in-pile bubble distributions taking into account the evolution of the concentration profile around a bubble during its growth and the destruction process by fission fragments. From these distributions a relation between the bubble mean radius and the diffusion coefficient of xenon can be established, allowing the determination, from experimental measurements of intragranular bubble sizes, of the in-pile Xe diffusion coefficient in UO 2. The estimated activation energy (0.9 eV) is about one order of magnitude lower than the widely used value of 3.9 eV determined from out-of-pile experiments. This effect can be attributed to the presence of point defects created by the irradiation.

Govers, K.; Lemehov, S.; Verwerft, M.

2008-03-01

170

Feedback instability of the ionospheric resonant cavity  

SciTech Connect

The exponential increase of the Alfven speed in the topside ionosphere leads to the formation of a resonant cavity (Lysak, 1988) which has been termed the ionospheric Alfven resonator by Trakhtengertz and Feldstein (1984). These authors primarily considered the situation where the ionospheric Pedersen conductivity is low, while Lysak (1988) considered the opposite limit of the infinite ionospheric conductivity. These results have been extended to arbitrary ionospheric conductivity by performing a numerical solution of the cavity dispersion relation, which involves Bessel functions of complex argument and order. These results indicate that the damping of excitations of this resonant cavity is strongest when the ionospheric Pedersen and Alfven conductivities are comparable and that growth is possible for incoming wave boundary conditions. The existence of this cavity leads to a modification of the Alfven wave reflection coefficient at the ionosphere. While this reflection coefficient is independent of frequency at low frequencies, it exhibits structure due to the resonant cavity modes at frequencies around 0.1-1 Hz. These cavity modes can also be excited by feedback instabilities (Sato, 1978; Lysak, 1986), leading to growth rates which are enhanced over the case without the cavity. These waves have maximum growth at short wavelengths, particularly when the background Pedersen conductivity is large. The perturbations associated with these instabilities can lead to structuring of auroral currents during substorms, and may help explain the westward traveling surge.

Lysak, R.L. (Univ. of Minnesota, Minneapolis (USA))

1991-02-01

171

Continuous cavity nucleation and creep fracture  

SciTech Connect

Intergranular creep fracture under the stress and temperature conditions experienced by components in service is generally acknowledged as resulting from nucleation and growth of intergranular cavities. Firstly, there seemed to be an approximately linear reciprocal relationship between time-to-fracture and minimum rate of creep deformation. Secondly, cavity growth by stress-directed flow of atoms was shown by Hull and Rimmer to lead to lifetime being inversely proportional to the maximum principal stress providing that all cavities initiated at the start of the test. Recently, it has been demonstrated that the boundary conditions imposed by Hull and Rimmer were unnecessarily restrictive and that more realistic ones result in cavity growth rates being proportional to strain rates. Nevertheless, there is an increasing body of experimental evidence on engineering alloys and also iron which indicates that cavities are not all nucleated in a short time interval, but are nucleated continuously. This paper collates the evidence for the continous nucleation of cavities, places this within the framework of creep fracture modelling and introduces a quantitative assessment of the likely errors of measurement. A model of cavity nucleation based on the stochastic nature of transgranular creep deformation is also discussed.

Dyson, B.F.

1983-01-01

172

Cell cycle and apoptosis regulatory protein (CARP)-1 is a novel, adriamycin-inducible, diffuse large B-cell lymphoma (DLBL) growth suppressor  

Microsoft Academic Search

\\u000a Abstract  Diffuse large B-cell lymphoma (DLCL) accounts for 30–40% of adult non-Hodgkin’s Lymphoma (NHL). Current anti-NHL therapies\\u000a often target cellular growth suppression pathways and include R-CHOP (cyclophosphamide, adriamycin, vincristine, and prednisone\\u000a plus monoclonal anti-CD20 antibody rituximab). However, since many patients relapse, resistant cells to these therapies remain\\u000a a significant problem and necessitate development of new intervention strategies. Cell cycle and apoptosis

Edi Levi; Liyue Zhang; Amro Aboukameel; Sunny Rishi; Ramzi M. Mohammad; Lisa Polin; James S. Hatfield; Arun K. Rishi

2011-01-01

173

Effect of grossular on garnet-biotite, Fe–Mg exchange reactions: evidence from garnet with mixed growth and diffusion zoning  

Microsoft Academic Search

Garnets that exhibit mixed growth and diffusion zoning are used to evaluate the effect of grossular content on garnet Fe–Mg\\u000a exchange reactions. These garnets from the uppermost amphibolite-facies to granulite-facies gneiss of the Wissahickon Group,\\u000a southeastern Pennsylvania, show variation in grossular content (0.035X\\u000a CaX\\u000a Mg\\/(X\\u000a Mg+X\\u000a Fe) and X\\u000a Mn through the interior indicating re-equilibration of garnet and matrix minerals

J. Alcock

1996-01-01

174

Suppression of Cavity Formation in Ceramics: Prospects for Superplasticity  

E-print Network

Suppression of Cavity Formation in Ceramics: Prospects for Superplasticity A. G. EVANS* Materials, Ohio State University, Columbus, Ohio 43210 Ceramics exhibit macroscopic stressistrain rate relations- tive surface diffusivities must be selected. I. Introduction HEN polycrystalline ceramic materials

175

Growth of carbon nanotubes (CNTs) on metallic underlayers by diffusion plasma-enhanced chemical vapour deposition (DPECVD)  

NASA Astrophysics Data System (ADS)

Here, we demonstrate the low-temperature (480-612 °C) synthesis of carbon nanotubes (CNTs) on different metallic underlayers (i.e., NiV, Ir, Ag, Pt, W, and Ta) using diffusion (dc) plasma-enhanced (~20 W, -600 V) chemical vapour deposition (DPECVD). The catalyst used is bi-layered Fe/Al and the feedstock used is a mixture of C 2H 2 and NH 3 (1:4). The crucial component is the diffusion of radical ions and hydrogen generated such as H 2/H +/H 2+/NH 3+/CH 2+/C 2H 2+ (which are confirmed by in-situ mass spectroscopy) from the nozzle, where it is inserted for most effective plasma diffusion between a substrate and a gas distributor.

Kim, S. M.; Gangloff, L.

2009-10-01

176

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

177

Segmented trapped vortex cavity  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

178

High density protein crystal growth  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

179

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

180

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.

Massachusetts Institute of Technology

181

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

182

Insulin-like growth factor-1 content and pattern of expression correlates with histopathologic grade in diffusely inéltrating astrocytomas  

Microsoft Academic Search

Studies of experimental tumorigenesis have strongly implicated signaling of the insulin-like growth factor 1 (IGF-1) as a key component in astrocytic neoplasia; how- ever, its role in the growth of low-grade and malignant human tumors is not well understood. Correlative analy- ses of IGF-1, p53, and Ki-67 (MIB-1) immunohistochem- istry and IGF-1 receptor (IGF-1R) mRNA expression were performed to examine

Hirofumi Hirano; M. Beatriz; S. Lopes; Edward R. Laws; Tetsuhiko Asakura; Masamichi Goto; Joan E. Carpenter; Larry R. Karns; Scott R. VandenBerg

183

LHC Beam Diffusion Dependence on RF Noise: Models And Measurements  

SciTech Connect

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

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

2010-09-14

184

Cavity quantum electrodynamics  

Microsoft Academic Search

This paper reviews the work on cavity quantum electrodynamics of free atoms. In recent years, cavity experiments have also been conducted on a variety of solid-state systems resulting in many interesting applications, of which microlasers, photon bandgap structures and quantum dot structures in cavities are outstanding examples. Although these phenomena and systems are very interesting, discussion is limited here to

Herbert Walther; Benjamin T. H. Varcoe; Berthold-Georg Englert; Thomas Becker

2006-01-01

185

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

SciTech Connect

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

Colombier, J. P.; Garrelie, F.; Faure, N.; Reynaud, S.; Bounhalli, M.; Audouard, E.; Stoian, R.; Pigeon, F. [Universite de Lyon, Laboratoire Hubert Curien, UMR 5516 CNRS, Universite Jean Monnet, 42000 Saint-Etienne (France)

2012-01-15

186

FORMATION OF HOLLOW CAVITIES ON {100} FACES OF LAP CRYSTALS INVESTIGATED BY AFM  

Microsoft Academic Search

Atomic force microscopy (AFM) has been used to study the hollow cavity formation mechanisms of the L-arginine phosphate monohydrate (LAP) crystals. Hollow cavities are formed through three modes. During 2D nucleation growth, initially formed 2D cavity prevents the growth around it layer-by-layer and causes the formation of 3D cavity with stepped-walls inside. Interaction of the steps advancing along different directions

Y. L. GENG; Z. H. H. SUN; D. XU

2007-01-01

187

Formation of Hollow Cavities on {100} Faces of Lap Crystals Investigated by Afm  

Microsoft Academic Search

Atomic force microscopy (AFM) has been used to study the hollow cavity formation mechanisms of the L-arginine phosphate monohydrate (LAP) crystals. Hollow cavities are formed through three modes. During 2D nucleation growth, initially formed 2D cavity prevents the growth around it layer-by-layer and causes the formation of 3D cavity with stepped-walls inside. Interaction of the steps advancing along different directions

Y. L. Geng; Zh. H. Sun; D. Xu

2007-01-01

188

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

189

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

190

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

191

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

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

2013-01-01

192

Apogossypolone, a nonpeptidic small molecule inhibitor targeting Bcl-2 family proteins, effectively inhibits growth of diffuse large cell lymphoma cells in vitro and in vivo.  

PubMed

Apogossypolone (ApoG2) is a semi-synthesized derivative of gossypol. The principal objective of this study was to compare stability and toxicity between ApoG2 and gossypol, and to evaluate anti-lymphoma activity of ApoG2 in vitro and in vivo. ApoG2 shows better stability when compared with a racemic gossypol and can be better tolerated by mice compared to gossypol. ApoG2 showed significant inhibition of cell proliferation of WSU-DLCL(2) and primary cells obtained from lymphoma patients, whereas it displayed no toxicity on normal peripheral blood lymphocytes. For a treatment of 72 h, the IC(50) of ApoG2 was determined to be 350 nM against WSU-DLCL2 cells. Treatment with ApoG2 at 600 mg/kg resulted in significant growth inhibition of WSU-DLCL(2) xenografts. When combined with CHOP, ApoG2 displayed even more complete inhibition of tumor growth. ApoG2 binds to purified recombinant Bcl-2, Mcl-1 and Bcl-X(L) proteins with high affinity and is shown to block the formation of heterodimers between Bcl-X(L) and Bim. For a treatment of 72 h, ApoG2 induced a maximum of 32% of apoptotic cell death. Western blot experiments showed that treatment with ApoG2 led to cleavage of caspase-3, caspase-9 and PARP. Moreover, pretreatment of DLCL(2) cells with caspase-3, -9 and broad spectrum caspase inhibitors significantly blocked growth inhibition induced by ApoG2. In conclusion, ApoG2 effectively inhibits growth of DLCL(2) cells at least partly by inducing apoptosis. It is an attractive small molecule inhibitor of the Bcl-2 family proteins to be developed further for the treatment of diffuse large cell lymphoma. PMID:18769131

Sun, Yuan; Wu, Jack; Aboukameel, Amro; Banerjee, Sanjeev; Arnold, Alan A; Chen, Jianyong; Nikolovska-Coleska, Zaneta; Lin, Yanqiong; Ling, Xiaolan; Yang, Dajun; Wang, Shaomeng; Al-Katib, Ayad; Mohammad, Ramzi M

2008-09-01

193

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

194

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; Ståhle, Per; Svensson, Ingrid

2015-01-01

195

Combining cellular automata and Lattice Boltzmann method to model multiscale avascular tumor growth coupled with nutrient diffusion and immune competition.  

PubMed

In the last decades the Lattice Boltzmann method (LB) has been successfully used to simulate a variety of processes. The LB model describes the microscopic processes occurring at the cellular level and the macroscopic processes occurring at the continuum level with a unique function, the probability distribution function. Recently, it has been tried to couple deterministic approaches with probabilistic cellular automata (probabilistic CA) methods with the aim to model temporal evolution of tumor growths and three dimensional spatial evolution, obtaining hybrid methodologies. Despite the good results attained by CA-PDE methods, there is one important issue which has not been completely solved: the intrinsic stochastic nature of the interactions at the interface between cellular (microscopic) and continuum (macroscopic) level. CA methods are able to cope with the stochastic phenomena because of their probabilistic nature, while PDE methods are fully deterministic. Even if the coupling is mathematically correct, there could be important statistical effects that could be missed by the PDE approach. For such a reason, to be able to develop and manage a model that takes into account all these three level of complexity (cellular, molecular and continuum), we believe that PDE should be replaced with a statistic and stochastic model based on the numerical discretization of the Boltzmann equation: The Lattice Boltzmann (LB) method. In this work we introduce a new hybrid method to simulate tumor growth and immune system, by applying Cellular Automata Lattice Boltzmann (CA-LB) approach. PMID:22154892

Alemani, Davide; Pappalardo, Francesco; Pennisi, Marzio; Motta, Santo; Brusic, Vladimir

2012-02-28

196

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

PubMed Central

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

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

2014-01-01

197

The LHC superconducting cavities  

E-print Network

The LHC RF system, which must handle high intensity (0.5 A d.c.) beams, makes use of superconducting single-cell cavities, best suited to minimizing the effects of periodic transient beam loading. There will be eight cavities per beam, each capable of delivering 2 MV (5 MV/m accelerating field) at 400 MHz. The cavities themselves are now being manufactured by industry, using niobium-on-copper technology which gives full satisfaction at LEP. A cavity unit includes a helium tank (4.5 K operating temperature) built around a cavity cell, RF and HOM couplers and a mechanical tuner, all housed in a modular cryostat. Four-unit modules are ultimately foreseen for the LHC (two per beam), while at present a prototype version with two complete units is being extensively tested. In addition to a detailed description of the cavity and its ancillary equipment, the first test results of the prototype will be reported.

Boussard, Daniel; Häbel, E; Kindermann, H P; Losito, R; Marque, S; Rödel, V; Stirbet, M

1999-01-01

198

Cavity enhanced terahertz modulation  

SciTech Connect

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

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

2014-03-10

199

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)

2009-11-03

200

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

201

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.

202

Tungsten diffusion in silicon  

SciTech Connect

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

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

2014-01-07

203

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

204

Liquid laser cavities  

NASA Technical Reports Server (NTRS)

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

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

1969-01-01

205

Cavity quantum electrodynamics  

Microsoft Academic Search

Cavity quantum electrodynamic (QED) phenomena appear to be applicable in the generation and precise measurement of electrodynamic fields which consist of only a few photons; cavity QED processes engender an intimate correlation between atomic states and field states, leading to new insights into light-matter interaction. Attention is given to such QED devices as a microlaser which uses an atomic beam

Serge Haroche; Jean-Michel Raimond

1993-01-01

206

Cavity QED photoelectric cell  

Microsoft Academic Search

The current status in the development program of a cavity QED photoelectric cell is reported. The cell comprises a pair of silicon chips interacting with each other by electromagnetic (EM) radiation through a gap of microscopic dimensions. The gap between the interacting surfaces is less than 100 nm and forms a 1D cavity QED confinement with a resonance in the

T. V. Prevenslik; F. G. Shin; C. L. Mak

1999-01-01

207

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

208

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

209

Growth of an initially sharp crack by grain boundary cavitation  

NASA Astrophysics Data System (ADS)

A new computational model is presented to analyze intergranular creep crack growth in a polycrystalline aggregate in a discrete manner and based directly on the underlying physical micromechanisms. A crack tip process zone is introduced in which grains and their grain boundaries are represented discretely, while the surrounding undamaged material is described as a continuum. Special-purpose finite elements are used to represent individual grains and grain boundary facets. The constitutive description of the grain boundary elements accounts for the relevant physical fracture mechanisms, i.e. viscous grain boundary sliding, the nucleation of grain boundary cavities, their growth by grain boundary diffusion and local creep, until coalescence of cavities leads to microcracks. Discrete propagation of the main crack occurs by linking up of neighbouring facet microcracks. Assuming small-scale damage conditions, the model is used to simulate the initial stages of growth of an initially sharp crack under C? controlled, mode I loading conditions. Material parameters are varied so as to lead to either ductile or brittle fracture, thus elucidating creep constrained cavitation near cracks. The role of the stress state dependence of cavity nucleation on the crack growth direction is emphasized.

Onck, Patrick; Giessen, Erik van der

1998-12-01

210

Hydroforming of elliptical cavities  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

211

Tuned optical cavity magnetometer  

DOEpatents

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

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

2010-11-02

212

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

PubMed

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

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

2013-12-01

213

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

214

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

2014-08-04

215

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

216

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>=5×109. 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. Gössel; J. Graber; D. Hubert; M. Hüning; M. Juillard; T. Junquera; H. Kaiser; G. Kreps; M. Kuchnir; R. Lange; M. Leenen; M. Liepe; L. Lilje; A. Matheisen; W.-D. Möller; A. Mosnier; H. Padamsee; C. Pagani; M. Pekeler; H.-B. Peters; O. Peters; D. Proch; K. Rehlich; D. Reschke; H. Safa; T. Schilcher; P. Schmüser; 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

217

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

218

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

219

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

E-print Network

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

W. G. Mathews; F. Brighenti

2008-05-16

220

Diffusion /Osmosis  

NSDL National Science Digital Library

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

Jensen

2007-11-26

221

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

222

VOLUME 82, NUMBER 18 P H Y S I C A L R E V I E W L E T T E R S 3 MAY 1999 Edge Diffusion during Growth: The Kink Ehrlich-Schwoebel Effect and Resulting Instabilities  

E-print Network

morphology during molecular-beam epitaxy (MBE) is of immense technological interest. One may want to produce, and, more gen- erally, to the consequences of diffusion along the steps in growth models. SESE

Einstein, Theodore L.

223

Cancer Stem Cells and Oral Cavity Cancer Metastasis  

Microsoft Academic Search

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

Mark Prince

224

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

225

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.

David Joiner

226

Effect of Cross-Interaction between Ni and Cu on Growth Kinetics of Intermetallic Compounds in Ni\\/Sn\\/Cu Diffusion Couples during Aging  

Microsoft Academic Search

The solid-state, cross-interaction between the Ni layer on the component side and the Cu pad on the printed circuit board (PCB) side in ball grid array (BGA) solder joints was investigated by employing Ni(15 mum)\\/Sn(65 mum)\\/Cu ternary diffusion couples. The ternary diffusion couples were prepared by sequentially electroplating Sn and Ni on a Cu foil and were aged isothermally at

K. K. Hong; J. B. Ryu; C. Y. Park; J. Y. Huh

2008-01-01

227

Effect of Cross-Interaction between Ni and Cu on Growth Kinetics of Intermetallic Compounds in Ni\\/Sn\\/Cu Diffusion Couples during Aging  

Microsoft Academic Search

The solid-state, cross-interaction between the Ni layer on the component side and the Cu pad on the printed circuit board\\u000a (PCB) side in ball grid array (BGA) solder joints was investigated by employing Ni(15 ?m)\\/Sn(65 ?m)\\/Cu ternary diffusion couples. The ternary diffusion couples were prepared by sequentially electroplating Sn and Ni on a\\u000a Cu foil and were aged isothermally at 150, 180,

K. K. Hong; J. B. Ryu; C. Y. Park; J. Y. Huh

2008-01-01

228

Effective Cavity Length of Gyrotrons  

NASA Astrophysics Data System (ADS)

Megawatt-class gyrotron oscillators for electron cyclotron heating and non-inductive current drive (ECH&CD) in magnetically confined thermonuclear fusion plasmas have relatively low cavity quality factors in the range of 1000 to 2000. The effective length of their cavities cannot be simply deduced from the cavity electric field profile, since this has by far not a Gaussian shape. The present paper presents a novel method to estimate the effective length of a gyrotron cavity just from the eigenvalue of the operating TEm,n mode, the cavity radius and the exact oscillation frequency which may be numerically computed or precisely measured. This effective cavity length then can be taken to calculate the Fresnel parameter in order to confirm that the cavity is not too short so that the transverse structure of any mode in the cavity is the same as that of the corresponding mode in a long circular waveguide with the same diameter.

Thumm, Manfred

2014-12-01

229

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

230

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

231

Triangle islands and cavities on the surface of evaporated Cu(In, Ga)Se2 absorber layer  

NASA Astrophysics Data System (ADS)

Cu(In, Ga)Se2 (CIGS) thin films are co-evaporated at a constant substrate temperature of 500 °C on the Mo/soda lime glass substrates. The structural properties and chemical composition of the CIGS films are studied by an X-ray diffractometer (XRD) and an X-ray fluorescent spectrometer (XRF), respectively. A scanning electron microscope (SEM) is used to study the surface morphology. Lots of uncommon triangle islands and cavities are found on some planes of the CIGS thin films. We investigate the formation mechanism of these triangle islands. It is found that the planes with the triangle islands are (1 1 2) planes terminated by Se atoms. Se ad-dimer as a nucleus, Cu diffusion from CIGS grains brings the epitaxial triangle islands which grow with a two-dimensional layered mode. The film with Cu/(Ga + In) = 0.94-0.98 is one key of the formation of these islands. The triangle cavities are formed due to the insufficient coalescence of triangle islands. The growth of triangle islands brings a compact surface with large layered grains and many jagged edges, but no triangle cavity. Finally, we compare the performance of solar cell with triangle islands and layered gains. It is found that the performance of solar cell with large layered gains is improved.

Han, Anjun; Zhang, Yi; Liu, Wei; Li, Boyan; Sun, Yun

2012-10-01

232

Breakdown in RF Cavities  

Microsoft Academic Search

We present a simple model of breakdown in rf cavities. For most events this involves tensile stress and tensile strength, however other effects can also contribute. We discuss the effects of different materials, fatigue, high pressure gas, primary and secondary emission sites, local field enhancements, dark currents, secondary emission, work functions, magnetic fields, macro and microscopic fracture mechanisms high current

J. Norem; A. Hassanein; Z. Insepov; I. Konkashbaev

2005-01-01

233

Melatonin and Oral Cavity  

PubMed Central

While initially the oral cavity was considered to be mainly a source of various bacteria, their toxins and antigens, recent studies showed that it may also be a location of oxidative stress and periodontal inflammation. Accordingly, this paper focuses on the involvement of melatonin in oxidative stress diseases of oral cavity as well as on potential therapeutic implications of melatonin in dental disorders. Melatonin has immunomodulatory and antioxidant activities, stimulates the proliferation of collagen and osseous tissue, and acts as a protector against cellular degeneration associated with aging and toxin exposure. Arising out of its antioxidant actions, melatonin protects against inflammatory processes and cellular damage caused by the toxic derivates of oxygen. As a result of these actions, melatonin may be useful as a coadjuvant in the treatment of certain conditions of the oral cavity. However, the most important effect of melatonin seems to result from its potent antioxidant, immunomodulatory, protective, and anticancer properties. Thus, melatonin could be used therapeutically for instance, locally, in the oral cavity damage of mechanical, bacterial, fungal, or viral origin, in postsurgical wounds caused by tooth extractions and other oral surgeries. Additionally, it can help bone formation in various autoimmunological disorders such as Sjorgen syndrome, in periodontal diseases, in toxic effects of dental materials, in dental implants, and in oral cancers. PMID:22792106

Cengiz, Murat ?nanç; Cengiz, Seda; Wang, Hom-Lay

2012-01-01

234

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

PubMed

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

Desdouits, Nathan; Nilges, Michael; Blondel, Arnaud

2015-02-01

235

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

236

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

237

Hollow waveguide cavity ringdown spectroscopy  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

238

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

SciTech Connect

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

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

2014-01-13

239

Lateral Diffusion in an Archipelago  

PubMed Central

Lateral diffusion of molecules in lipid bilayer membranes can be hindered by the presence of impermeable domains of gel-phase lipid or of proteins. Effective-medium theory and percolation theory are used to evaluate the effective lateral diffusion constant as a function of the area fraction of fluid-phase lipid and the permeability of the obstructions to the diffusing species. Applications include the estimation of the minimum fraction of fluid lipid needed for bacterial growth, and the enhancement of diffusion-controlled reactions by the channeling effect of solid patches of lipid. PMID:7052153

Saxton, Michael J.

1982-01-01

240

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

241

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

242

RF Cavity Characterization with VORPAL  

SciTech Connect

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

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

2011-03-01

243

Mathematical modelling of glioma growth: The use of Diffusion Tensor Imaging (DTI) data to predict the anisotropic pathways of cancer invasion  

E-print Network

of these diffusion tensors and, in the context of the brain, DTI can therefore map the pathways of neural fibre the anisotropic pathways of cancer invasion K.J. Painter a,n , T. Hillen b a Department of Mathematics and Maxwell model. c We show the impact of alignment on the invasion pathways using synthetic and real DTI datasets

Hillen, Thomas

244

Rotational cavity optomechanics  

E-print Network

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

Bhattacharya, M

2015-01-01

245

CAVITY CONTROL ALGORITHM  

SciTech Connect

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

Tomasz Plawski, J. Hovater

2010-09-01

246

Acoustic resonance in a cavity under a subsonic flow  

NASA Astrophysics Data System (ADS)

Acoustic resonances leading to high unsteady pressure levels may occur in flow past cavities. The resonance involves a coupling between the downstream-propagating instability wave on the shear layer spanning the open face of the cavity, and acoustic waves propagating within and external to the cavity. These elements of the disturbance field are coupled by the scattering processes that occur at the upstream and downstream ends of the cavity. We develop a theoretical prediction method that combines propagation models in the central region of the cavity with scattering models for the end regions. In our analyses of the scattering processes at the cavity ends, the square-corner geometry is treated exactly, by a method employing the Wiener-Hopf technique. The shear layer is approximated as a vortex sheet in the edge scattering analyses, but finite shear-layer thickness is accounted for in analyzing the propagation of the waves along the length of the cavity. The global analysis leads to a prediction for the resonant frequencies which has a form similar to the Rossiter formula, but contains no empirical constants. In addition to prediction of the frequency, our theory determines the temporal growth or decay rate of each mode. Finally, our theory also predicts the influence of secondary feedback loops involving other components of the unsteady field. Comparisons of the predictions with existing experimental data are made.

Alvarez Sierra, Jose Oliverio

247

Oral Cavity Surgery Codes  

Cancer.gov

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

248

Gyromultiplier with sectioned cavity  

SciTech Connect

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

Bandurkin, I. V.; Mishakin, S. V. [Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation)

2010-11-15

249

Erosion-induced whisker growth on aluminum  

SciTech Connect

An internal combustion phenomenon leading to the growth of amorphous, macroscopic whiskers with a unique growth morphology is induced on pure Al by solid-particle erosion. It can be concluded that the whisker growth reaction occurs because vented, subsurface cavities form during the erosion process and these cavities act as localized internal combustion sites for the reaction. The whiskers are hollow tubes that appear to grow from the cavity vents as reaction product chimneys. The subsurface cavities are a result of extensive material displacement and folding during erosion in bulk Al samples, and the cavities are associated with a characteristic erosion-surface ripple structure. Since both oxygen and water vapor are needed for whisker growth, it can also be concluded that the whiskers are composed of an amorphous aluminum hydrous oxide. Finally, it appears likely that the local temperature increases which can occur during erosion are necessary for the initiation of the whisker growth reaction.

Hovis, S.K.; Scattergood, R.O.; Talla, J.

1985-11-01

250

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

DOEpatents

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

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

2014-11-11

251

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

NASA Astrophysics Data System (ADS)

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

Yu, Jia; Gao, Qiang; Zhang, Zhiguo

2014-10-01

252

Oral melanoacanthoma: A rare case of diffuse oral pigmentation  

PubMed Central

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

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

2012-01-01

253

Investigation of Resonant Cavity-Enhanced Photodetectors and Avalanche Optoelectronic Switches  

Microsoft Academic Search

Application of compound semiconductors to electronic and optoelectronic devices offers numerous advantages over elementary semiconductors, such as the feasibility of high quality heterostructures prepared by modern crystal growth techniques. And optical resonant cavity formed by multilayer dielectric stacks is among the important applications of heterostructures in optoelectronic devices. This thesis deals with a theoretical and experimental investigation of resonant cavity

Feng-Yi. Huang

1994-01-01

254

Growth of superconducting NdFe0.88Co0.12AsO films by metal-organic chemical vapor deposition and post arsenic diffusion  

NASA Astrophysics Data System (ADS)

Metal-organic chemical vapor deposition (MOCVD) and post-deposition arsenic diffusion processes were successfully employed to grow superconducting NdFe0.88Co0.12AsO thin films. First, by employing iron, cobalt and neodymium metal-organic precursors, a precursor film is grown by MOCVD on (001)-oriented LaAlO3 substrates. Subsequently, the arsenic is incorporated during an annealing of these precursor films in the presence of a NdFe0.9Co0.1AsO pellet. The chemical composition and crystallographic results indicate the formation of the cobalt-doped NdFeAsO polycrystalline phase. The secondary ion mass spectroscopy indicates a homogeneous arsenic diffusion process. The resistance and magnetization measurements as a function of temperature indicate a superconducting transition ˜15 \\text{K} .

Corrales-Mendoza, I.; Bartolo-Pèrez, P.; Sánchez-Reséndiz, V. M.; Gallardo-Hernández, S.; Conde-Gallardo, A.

2015-01-01

255

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.

Jeni McDermott

256

Cavity-Loss Induced Plateau in Coupled Cavity QED Array  

NASA Astrophysics Data System (ADS)

Nonequilibrium steady states are investigated in a coupled cavity QED array system which is pumped by a thermal bath and dissipated through cavity loss. In the coherent (non-zero photon amplitude) phase, plateau regions appear, where the steady states become unchanged against the variation of the chemical potential of the thermal bath. The cavity loss plays a crucial role for the plateaus: the plateaus appear only if the cavity loss exists, and the photon leakage current, which is induced by the loss, is essential to the mechanism of the plateaus.

Yuge, Tatsuro; Kamide, Kenji; Yamaguchi, Makoto; Ogawa, Tetsuo

2014-12-01

257

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

258

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

259

Stress-diffusion interaction during oxidation at high temperature  

NASA Astrophysics Data System (ADS)

Superalloy or other thermal protective materials are often oxidized seriously at high temperature. For most materials diffusion is the controlling step of oxidation. During oxidation, stress would be induced by growth strain and it can affect the diffusion process through chemical potential and diffusivity. Governing equation for diffusion is derived considering chemo-mechanical potential and diffusivity affected by stress. Oxidation kinetics is obtained to interpret the stress-diffusion coupling effects. The stress and its gradient influences on oxidation are also discussed.

Dong, Xuelin; Feng, Xue; Hwang, Keh-Chih

2014-10-01

260

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

261

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

262

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

263

Cavity Optomechanical Magnetometer  

NASA Astrophysics Data System (ADS)

A cavity optomechanical magnetometer is demonstrated. The magnetic-field-induced expansion of a magnetostrictive material is resonantly transduced onto the physical structure of a highly compliant optical microresonator and read out optically with ultrahigh sensitivity. A peak magnetic field sensitivity of 400nTHz-1/2 is achieved, with theoretical modeling predicting the possibility of sensitivities below 1pTHz-1/2. This chip-based magnetometer combines high sensitivity and large dynamic range with small size and room temperature operation.

Forstner, S.; Prams, S.; Knittel, J.; van Ooijen, E. D.; Swaim, J. D.; Harris, G. I.; Szorkovszky, A.; Bowen, W. P.; Rubinsztein-Dunlop, H.

2012-03-01

264

Breakdown in rf cavities.  

SciTech Connect

We present a simple model of breakdown in rf cavities. For most events this involves tensile stress and tensile strength, however other effects can also contribute. We discuss the effects of different materials, fatigue, high pressure gas, primary and secondary emission sites, local field enhancements, dark currents, secondary emission, work functions, magnetic fields, macro and microscopic fracture mechanisms high current densities, surface and subsurface defects, and astronomical power densities. While primarily devoted to normal conductors, this work also has consequences for superconducting rf surfaces.

Norem, J.; Hassanein, A.; Insepov, Z.; Konkashbaev, I.

2005-01-01

265

Cavity optomechanical magnetometer.  

PubMed

A cavity optomechanical magnetometer is demonstrated. The magnetic-field-induced expansion of a magnetostrictive material is resonantly transduced onto the physical structure of a highly compliant optical microresonator and read out optically with ultrahigh sensitivity. A peak magnetic field sensitivity of 400??nT? Hz(-1/2) is achieved, with theoretical modeling predicting the possibility of sensitivities below 1??pT? Hz(-1/2). This chip-based magnetometer combines high sensitivity and large dynamic range with small size and room temperature operation. PMID:22540567

Forstner, S; Prams, S; Knittel, J; van Ooijen, E D; Swaim, J D; Harris, G I; Szorkovszky, A; Bowen, W P; Rubinsztein-Dunlop, H

2012-03-23

266

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

267

Characterization of circularly polarized square cavity backed antennas  

Microsoft Academic Search

The growth of personal wireless communications systems has generated significant interest in the development of small, broad bandwidth and broad radiation pattern antennas for mobile terminal applications. In addition to the desired circuit and radiation properties of the antennas, physically non-obtrusive antennas are required for mobile terminal applications. In this presentation, low profile cavity backed circularly polarized antennas are studied.

J. S. Colburn; Y. Rahmat-Samii

1997-01-01

268

Residence time and crystallization history of nickeliferous olivine phenocrysts from the northern Yatsugatake volcanoes, Central Japan: Application of a growth and diffusion model in the system Mg-Fe-Ni  

NASA Astrophysics Data System (ADS)

The chemical zoning of nickeliferous olivine phenocrysts in calc-alkaline andesites from the northern Yatsugatake volcanoes, Central Japan, is examined by a growth and diffusion model in the system Mg-Fe-Ni. Nickeliferous olivine phenocrysts are included in the high-alumina basaltic end-member magma which forms the mixed calc-alkaline andesites in the northern Yatsugatake volcanoes. The olivine phenocrysts can be divided into three types on the basis of chemical composition, zoning profile and occurrence. Type-1 olivine is rich in Ca and Mg, and the zoning profile of type-1 forms a slightly more Fe-rich trend than the maximum fractionation trend in the NiO versus forsterite content (Fo) diagram. The most Mg and Ni rich, and Mn poor core of type 1 (Fo 91.5 mol%, NiO 0.40 wt%, MnO 0.13 wt%) can be in equilibrium with peridotite in the upper mantle. By contrast, type-2 olivine is Ca poor, and rich in Fe and Ni compared to type-1. The zoning patterns of type-2 are more variable. The NiO content in Fe-rich type-2 phenocrysts decreases rapidly from core to rim within a narrow range of Fo. The maximum NiO content of type-2 is 0.53 wt%. The transitional-type olivine has an intermediate composition between type-1 and type-2 and a similar zoning profile as that of type-1. Type-1 olivine mainly occurs as isolated phenocrysts, while Fe-rich type-2 occurs as crystal clots. The growth and diffusion calculation in the system Mg-Fe-Ni revealed that the composition of normally zoned olivine is enriched in Fe by diffusion without a marked depression in the Ni content due to a larger Fe-Mg interdiffusion coefficient than the Ni tracer diffusion coefficient in olivine. The zoning patterns of both type-1 and type-2 can be reproduced by calculation. The residence time of type-1 olivine in the magma is estimated to be less than 10 -0.5-1 y at 1150 - 1050 °C, whereas the residence time of Fe-enriched type-2 olivine is from ten to one hundred times longer than that of type-1. The long residence time and occurrence as crystal clots suggest that the Fe-enriched type-2 olivine phenocrysts were captured and crystallized in the crystal mush at the roof and bottom of a magma chamber.

Nakamura, Michihiko

1995-07-01

269

Monochromatic radio frequency accelerator cavity  

SciTech Connect

In circular accelerators and storage rings it is important that any device placed in the beam line be relatively free of spurious resonances. Accelerating RF cavities inherently have an infinite number of spurious modes. The cavity to be described in this paper makes use of certain geometric construction configurations that eliminate all the spurious modes. A cavity was constructed with an accelerating TMolo mode of 90 MHz. Measurements showed that the TMolo mode was essentially unchanged from a conventional cavity but all modes up to 3 GHz were either completely eliminated or reduced by at least 30 db.

Giordano, S.

1983-01-01

270

Diffusion-controlled growth of a solid cylinder into its undercoded melt:Instabilities and pattern formation studied with the phase-field model  

NASA Astrophysics Data System (ADS)

Instabilities in the solidification of a cylinder in its undercooled melt are numerically studied within the phase-field model. This growth becomes morphologically unstable when its radius exceeds a critical value R, that is a decreasing function of the thermodynamic driving force:mthe circular growth regime should be hardly observable, in practice, except possibly at extremely low values of the dimensionless undercooling ?. However, the equation for the amplitude of the perturbing modes shows that the response of the growing front to a finite noise is drastically reduced when ? is increased, so that a more stable growth should be associated to larger undercoolings. This suggestion is confirmed by the numerical simulations, which allow us to fix the onset and the extent of the perturbations. To summarize the results, an effective critical radius is represented as a function of ?.

Conti, M.; Marinozzi, F.; Marini Bettolo Marconi, U.

1997-03-01

271

Diffusion tube  

NASA Technical Reports Server (NTRS)

The diffusion tube was designed to operate below about 0.25 percent of water supersaturation. It is simply a long tube lined on the inside with a damp chamois cloth, and heated isothermally to a few degrees centigrade above the incoming air. The diffusion coefficient for water vapor is slightly larger than that for heat, making it possible to supersaturate the airflow. This is the same principle by which transient supersaturations may occur in parallel plate cloud chambers. Only the diffusion of vapor and heat from the walls into the moving air are considered.

Leaitch, R.; Megaw, W. J.

1981-01-01

272

Cavity pattern formation and cavity solitons with incoherent light  

Microsoft Academic Search

We show that patterns and solitons can form when spatially and temporally incoherent light circulates in a passive nonlinear cavity with noninstantaneous medium. The pattern formation process is always associated with two consecutive thresholds. The first (instability) threshold is unaffected by the cavity boundary conditions, whereas the second threshold is induced by the feedback through the interplay of nonlinear gain

H. Buljan; M. Soljacic; T. Carmon; M. Segev

2003-01-01

273

Cavity enhanced absorption and cavity enhanced magnetic rotation spectroscopy  

Microsoft Academic Search

It is experimentally demonstrated that a narrow band continuous wave (cw) light source can be used in combination with a high-finesse optically stable cavity to perform sensitive, high-resolution direct absorption and optical rotation spectroscopy in an amazingly simple experimental setup, using ideas from the field of cavity ring down spectroscopy. Light from a scanning narrow band cw laser is coupled

Richard Engeln; Giel Berden; Rudy Peeters; Gerard Meijer

1998-01-01

274

Multicolor cavity metrology  

NASA Astrophysics Data System (ADS)

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.

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

275

Applications of cavity optomechanics  

SciTech Connect

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

2014-09-15

276

Gigahertz Modulation of a Photonic Crystal Cavity  

NASA Astrophysics Data System (ADS)

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

Ali, Aaron Karim Taylor

277

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

Microsoft Academic Search

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

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

1996-01-01

278

Quantum jump dynamics in cavity QED  

NASA Astrophysics Data System (ADS)

We study the stochastic dynamics of the electromagnetic field in a lossless cavity interacting with a beam of two-level atoms, given that the atomic states are measured after they have crossed the cavity. The atoms first interact at the exit of the cavity with a classical laser field E and then enter into a detector which measures their states. Each measurement disentangles the field and the atoms and changes in a random way the state |?(t)> of the cavity field. For weak atom-field coupling, the evolution of |?(t)> when many atoms cross the cavity and the detector is characterized by a succession of quantum jumps occurring at random times, separated by quasi-Hamiltonian evolutions, both of which depend on the laser field E. For E=0, the dynamics is the same as in the Monte Carlo wave function model of Dalibard et al. [Phys. Rev. Lett. 68, 580 (1992)] and Carmichael, An Open System Approach to Quantum Optics, Lecture Notes in Physics Vol. 18 (Springer, Berlin, 1991)]. The density matrix of the quantum field, obtained by averaging the projector |?(t)> evolves under the monitoring of the atoms and the measurements toward squeezed states |?,re2i?>, moving in the ?-complex plane but with almost constant squeezing parameters r and ?. The values of r and ? are determined analytically. On the other hand, for E=0, the dynamics transforms the initial state into Fock states |n> with fluctuating numbers of photons n, as shown in Kist et al. [J. Opt. B: Quantum Semiclassical Opt. 1, 251 (1999)]. In the last part, we derive the quantum jump dynamics from the linear quantum jump model proposed in Spehner and Bellissard [J. Stat. Phys. 104, 525 (2001)], for arbitrary open quantum systems having a Lindblad-type evolution. A careful derivation of the infinite jump rates limit, where the dynamics can be approximated by a diffusion process of the quantum state, is also presented.

Spehner, D.; Orszag, M.

2002-07-01

279

Diffuse radiation  

NASA Technical Reports Server (NTRS)

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

1981-01-01

280

Trislot-cavity microstrip antenna  

NASA Technical Reports Server (NTRS)

Flush-mountable assembly composed of disk radiator sandwiched between planes of metal-clad dielectric board has greater bandwidths and beamwidths than simple disk antenna. Conducting planes connect so that disk is enclosed in cavity with Y-shaped slot in top plane. Cavity is excited by microwave energy from disk and radiates from trislot aperature.

Ellis, H., Jr.

1981-01-01

281

Precise cavity enhanced absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A short review of recent achievements in high-precision cavity enhanced absorption spectroscopy is presented. Actual challenges and development paths in modern line shape study are indicated and discussed. The importance of identification and quantification of systematic instrumental errors affecting the measured line shape is highlighted. New, alternative measurement methods based on cavity enhanced spectroscopy are proposed.

Cygan, A.; Wcis?o, P.; Wójtewicz, S.; Mas?owski, P.; Domys?awska, J.; Trawi?ski, R. S.; Ciury?o, R.; Lisak, D.

2014-11-01

282

FPGA based ILC cavity simulator  

Microsoft Academic Search

This paper presents a FPGA based Real Time Simulator of ILC superconducting RF cavities. The system has been developed on a Lyrtech VHS-ADAC board, through the use of Xilinx System Generator and Simulink. This FPGA system is mainly being developed for allowing testing of the LLRF systems in the real time and for different cavities parameters.

Anna Grassellino; Justin K. Keung; Mitch Newcomer; Nigel Lockyer

2007-01-01

283

Quantum well vertical cavity laser  

SciTech Connect

This patent describes an apparatus which comprises: quantum well laser vertical cavity structure for lasing in a direction non-parallel to the major dimensions of a quantum well, such laser consisting essentially of an active element containing one or two quantum wells and a cavity dependent upon reflectance as between two distributed feedback mirrors.

Huang, R.F.; Jewell, J.L.; McCall, S.L. Jr.; Tai, K.

1991-03-12

284

Resonant cavity enhanced photonic devices  

Microsoft Academic Search

We review the family of optoelectronic devices whose performance is enhanced by placing the active device structure inside a Fabry-Perot resonant microcavity. Such resonant cavity enhanced (RCE) devices benefit from the wavelength selectivity and the large increase of the resonant optical field introduced by the cavity. The increased optical field allows RCE photodetector structures to be thinner and therefore faster,

M. Selim Ünlü; Samuel Strite

1995-01-01

285

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

286

Cavity ring-down spectroscopy  

Microsoft Academic Search

Cavity ring-down (CRD) spectroscopy is a direct absorption technique, which can be performed with pulsed or continuous light sources and has a significantly higher sensitivity than obtainable in conventional absorption spectroscopy. The CRD technique is based upon the measurement of the rate of absorption rather than the magnitude of absorption of a light pulse confined in a closed optical cavity

Giel Berden; Rudy Peeters; Gerard Meijer

2000-01-01

287

Stages of Lip and Oral Cavity Cancer  

MedlinePLUS

Stages of Lip and Oral Cavity Cancer Key Points for This Section After lip and oral cavity cancer has been diagnosed, ... I Stage II Stage III Stage IV After lip and oral cavity cancer has been diagnosed, tests ...

288

Grain boundary diffusion in enstatite  

NASA Astrophysics Data System (ADS)

We have investigated grain boundary diffusion rates in enstatite by heating single crystals of quartz packed in powdered San Carlos olivine (Mg0.90Fe0.10)2SiO4 at controlled oxygen fugacities in the range 10-5.7 to 10-8.7 atm and temperatures from 1350° to 1450 °C for times from 5 to 100 h at 1 atm total pressure. Following the experiments, the thickness of the coherent polycrystalline reaction rim of pyroxene that had formed between the quartz and olivine was measured using backscatter scanning imaging in the electron microprobe. Quantitative microprobe analysis indicated that the composition of this reaction phase is (Mg0.92Fe0.08)2Si2O6. The rate of growth of the pyroxene increases with increasing temperature, is independent of the oxygen fugacity, and is consistent with a parabolic rate law, indicating that the growth rate is controlled by ionic diffusion through the pyroxene rim. Microstructural observations and platinum marker experiments suggest that the reaction phase is formed at the olivine-pyroxene interface, and is therefore controlled by the diffusion of silicon and oxygen. The parabolic rate constants determined from the experiments were analyzed in terms of the oxide activity gradient across the rim to yield mean effective diffusivities for the rate-limiting ionic species, assuming bulk transport through the pyroxene layer. These effective diffusivities are faster than the lattice diffusivities for the slowest species (silicon) calculated from creep experiments, but slower than measured lattice diffusivities for oxygen in enstatite. Thus, silicon grain boundary diffusion is most likely to be the rate-limiting process in the growth of the pyroxene rims. Also, as oxygen transport through the pyroxene rims must be faster than silicon transport, diffusion of oxygen along the grain boundaries must be faster than through the lattice. The grain boundary diffusivity for silicon in orthopyroxenite is then given by DgbSi?=(3.3+/-3.0)×10-9f0.0O2e-400+/-65/RT m3s-1, where the activation energy for diffusion is in kJ/mol, and ? is the grain boundary width in m. Calculated growth rates for enstatite under these conditions are significantly slower than predicted by an extrapolation from similar experiments performed at 1000 °C under high pressure (hydrous) conditions by Yund and Tullis (1992), perhaps due to water-enhancement of diffusion in their experiments.

Fisler, D. K.; Mackwell, S. J.; Petsch, S.

289

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

290

Monochromatic radio frequency accelerating cavity  

DOEpatents

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

Giordano, Salvatore (Port Jefferson, NY)

1985-01-01

291

Monochromatic radio frequency accelerating cavity  

DOEpatents

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

Giordano, S.

1984-02-09

292

Superconducting Storage Cavity for RHIC  

SciTech Connect

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

Ben-Zvi,I.

2009-01-02

293

Evaluation of a closed system, diffusive and humidity-induced convective throughflow ventilation on the growth and physiology of cauliflower in vitro  

Microsoft Academic Search

The effects of ethylene inhibitors (silver nitrate – AgNO3 and silver thiosulphate – Ag2S2O3 as inhibitors of ethylene activity, cobalt chloride – CoCl2 as inhibitor of ethylene biosynthesis) and ethylene stimulator (aminocyclopropane-1-carboxylic acid – ACC) were studied on\\u000a the growth of cauliflower (Brassica oleracea L.) seedlings cultured in closed vessels (60 cm3). The addition of ethylene inhibitors have significant stimulatory

S. M. A. Zobayed; J. Armstrong; W. Armstrong

1999-01-01

294

Active cavity radiometer  

NASA Technical Reports Server (NTRS)

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

Willson, R. C.

1981-01-01

295

A Scanning Cavity Microscope  

E-print Network

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

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

2014-01-01

296

Two-Time Three-Equation Method for Analysis of Oxidation-Enhanced and -Retarded Diffusions and Growth of Oxidation Stacking Faults in Silicon  

NASA Astrophysics Data System (ADS)

For analysis of oxidation-enhanced and -retarded diffusion (OED and ORD) and oxidation stacking faults (OSF) in Si, two out of the three equations for OED, ORD and OSF were used. The equation for a local equilibrium between self-interstitials and vacancies was also used. Thus three equations were used. Two time values were taken in these three equations. In the previous paper (Jpn. J. Appl. Phys. 27 (1988) 967), the experimental results were modified in order to obtain physically reasonable solutions. But this is not good. In the present work, therefore, the equations were simultaneously solved without modifying experimental results. It was concluded that the equation of OSF should not be used.

Okino, Takahisa; Yoshida, Masayuki

1990-01-01

297

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

298

Cavity state preparation using adiabatic transfer  

E-print Network

We show how to prepare a variety of cavity field states for multiple cavities. The state preparation technique used is related to the method of stimulated adiabatic Raman passage or STIRAP. The cavity modes are coupled by atoms, making it possible to transfer an arbitrary cavity field state from one cavity to another, and also to prepare non-trivial cavity field states. In particular, we show how to prepare entangled states of two or more cavities, such as an EPR state and a W state, as well as various entangled superpositions of coherent states in different cavities, including Schrodinger cat states. The theoretical considerations are supported by numerical simulations.

Jonas Larson; Erika Andersson

2005-03-14

299

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

300

The Growth of Steroidobacter agariperforans sp. nov., a Novel Agar-Degrading Bacterium Isolated from Soil, is Enhanced by the Diffusible Metabolites Produced by Bacteria Belonging to Rhizobiales  

PubMed Central

An agar-degrading bacterium was isolated from soil collected in a vegetable cropping field. The growth of this isolate was enhanced by supplying culture supernatants of bacteria belonging to the order Rhizobiales. Phylogenetic analysis based on 16S rRNA gene sequences indicated the novel bacterium, strain KA5–BT, belonged to the genus Steroidobacter in Gammaproteobacteria, but differed from its closest relative, Steroidobacter denitrificans FST, at the species level with 96.5% similarity. Strain KA5–BT was strictly aerobic, Gram-negative, non-motile, non-spore forming, and had a straight to slightly curved rod shape. Cytochrome oxidase and catalase activities were positive. The strain grew on media containing culture supernatants in a temperature range of 15–37°C and between pH 4.5 and 9.0, with optimal growth occurring at 30°C and pH 6.0–8.0. No growth occurred at 10 or 42°C or at NaCl concentrations more than 3% (w/v). The main cellular fatty acids were iso–C15:0, C16:1?7c, and iso–C17:1?9c. The main quinone was ubiquinone-8 and DNA G+C content was 62.9 mol%. In contrast, strain FST was motile, did not grow on the agar plate, and its dominant cellular fatty acids were C15:0 and C17:1?8c. Based on its phylogenetic and phenotypic properties, strain KA5–BT (JCM 18477T = KCTC 32107T) represents a novel species in genus Steroidobacter, for which the name Steroidobacter agariperforans sp. nov. is proposed. PMID:24621511

Sakai, Masao; Hosoda, Akifumi; Ogura, Kenjiro; Ikenaga, Makoto

2014-01-01

301

Diffusion-controlled reactions: Mathematical formulation, variational principles, and rigorous bounds  

E-print Network

, cell metabolism, gaseous diffusion through solid, polymer chain growth kinetics, colloid or crystal growth, precipita- tion, fluorescence quenching, and combustion, to mention but a few examples. We

Torquato, Salvatore

302

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

303

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

304

Defusing Diffusion  

ERIC Educational Resources Information Center

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

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

2013-01-01

305

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.

Alexei Sharov

306

Improved integrating cavity absorption meter  

E-print Network

Improvements have been made in the Integrating Cavity Absorption Meter (ICAM). The ICAM is used to measure very small optical absorption coefficients (0.001m?¹), virtually independent of scattering effects. Optical absorption is measured...

Cui, Liqiu

2000-01-01

307

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

308

The superconducting accelerating cavities for the Tritron  

Microsoft Academic Search

The Tritron is a separated orbit cyclotron with superconducting magnets and rf-cavities. The six cavities operate at 170 MHz. They are designed to have a small field enhancement factor. The cavities are fabricated by electroplating copper onto fibreglass shells. The copper is electroplated with PbSn as superconductor. Test results for the first two cavities are given. The values for the

T. Grundey; J. Labedzki; P. Schütz; U. Trinks

1991-01-01

309

Polishing Difficult-To-Reach Cavities  

NASA Technical Reports Server (NTRS)

Springy abrasive tool used to finish surfaces of narrow cavities made by electrical-discharge machining. Robot arm moves vibrator around perimeters of cavities, polishing walls of cavities as it does so. Tool needed because such cavities inaccessible or at least difficult to reach with most surface-finishing tools.

Malinzak, R. Michael; Booth, Gary N.

1990-01-01

310

Imaging of the oral cavity.  

PubMed

The oral cavity is a challenging area in head and neck imaging because of its complex anatomy and the numerous pathophysiologies that involve its contents. This challenge is further compounded by the ubiquitous artifacts that arise from the dental amalgam, which compromise image quality. In this article, the anatomy of the oral cavity is discussed in brief, followed by a description of the imaging technique and some common pathologic abnormalities. PMID:25476175

Meesa, Indu Rekha; Srinivasan, Ashok

2015-01-01

311

Abdominal Cavity and Laparoscopic Surgery  

NSDL National Science Digital Library

For students interested in studying biomechanical engineering, especially in the field of surgery, this lesson serves as an anatomy and physiology primer of the abdominopelvic cavity. Students are introduced to the abdominopelvic cavity—a region of the body that is the focus of laparoscopic surgery—as well as the benefits and drawbacks of laparoscopic surgery. Understanding the abdominopelvic environment and laparoscopic surgery is critical for biomechanical engineers who design laparoscopic surgical tools.

Integrated Teaching and Learning Program,

312

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

313

Cross-country diffusion of the Internet  

Microsoft Academic Search

This paper investigates the factors which determine the diffusion of the Internet across countries. The Gompertz model of technology diffusion is estimated using data on Internet hosts per capita for the years 1995–2000. For a sample of the OECD countries, the basic finding is that GDP per capita and Internet access cost explain best the observed growth in computer hosts

Sampsa Kiiski; Matti Pohjola

2002-01-01

314

Efficiently Loading a Single Photon into a Single-Sided Fabry-Perot Cavity  

NASA Astrophysics Data System (ADS)

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 (87±2)% 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 (60±5)% 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.

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

2014-09-01

315

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

PubMed

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

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

2014-01-01

316

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

SciTech Connect

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

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

2005-07-06

317

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 (87±2)% 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 (60±5)% 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

318

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

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

2014-10-15

319

A Hot Cavity Laser Ion Source at IGISOL  

E-print Network

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

Reponen, M; Moore, I D; Rothe, S; Äystö, J

2008-01-01

320

A Hot Cavity Laser Ion Source at IGISOL  

E-print Network

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

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

2008-12-08

321

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

322

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

323

Hidden Sector Photon Coupling of Resonant Cavities  

E-print Network

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

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

2013-04-25

324

Thermal properties of dental materials--cavity liner and pulp capping agent.  

PubMed

We studied the thermal properties of cavity liners that included calcium phosphate as inorganic filler, in contrast to the conventional pulp capping agents. Therefore, thermal diffusivity, specific heat capacity, and thermal conductivity were measured. In addition, thermal conductivity results were compared with those of restorative materials and human dentin to examine thermal insulation effects. The thermal conductivity of cavity liners ranged from 0.23 to 0.28 W m(-1) K(-1), and that of pulp capping agents ranged from 0.44 to 0.48 W m(-1) K(-1). Test results indicated that the thermal conductivity of cavity liner was lower than those of human dentin, pulp capping agent, cast alloy, and composite resin for restoration, hence suggesting that cavity liner has a good thermal insulation effect. PMID:15510872

Saitoh, Masahiro; Masutani, Shigeyuki; Kojima, Taishi; Saigoh, Masataka; Hirose, Hideharu; Nishiyama, Minoru

2004-09-01

325

Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity,  

E-print Network

Modelling precipitation of niobium carbide in austenite: multicomponent diffusion, capillarity, and coarsening N. Fujita and H. K. D. H. Bhadeshia The growth of niobium carbide in austenite involves the diffusion of both niobium and carbon. These elements diffuse at very different rates. A model is presented

Cambridge, University of

326

Differential Diffusion in Breaking Kelvin–Helmholtz Billows  

Microsoft Academic Search

Direct numerical simulations are used to compare turbulent diffusivities of heat and salt during the growth and collapse of Kelvin-Helmholtz billows. The ratio of diffusivities is obtained as a function of buoyancy Reynolds number Reb and of the density ratio R (the ratio of the contributions of heat and salt to the density stratification). The diffusivity ratio is generally less

W. D. Smyth; J. D. Nash; J. N. Moum

2005-01-01

327

Dislocation-Free Formation of Artificial Cavities in Si Single Crystal  

Microsoft Academic Search

Cavities enclosed in silicon single crystals are formed by utilizing epitaxial growth on surfaces with microstructures consisting of parallel walls. The cavities accompany no dislocations and\\/or stacking faults in the surrounding crystal. Their as-formed cross-sectional shape is thin: the length being about 2 mum as compared with the width of 0.3 mum. The shape can be controllably changed by heat

Naotsugu Yoshihiro; Nobuyoshi Natsuaki

1990-01-01

328

Ambipolar Diffusion  

NASA Astrophysics Data System (ADS)

When magnetic forces are present in a partially ionized medium, the plasma drifts with respect to the neutrals. This plasma—neutral drift, which is known as ambipolar diffusion, occurs in all partially ionized astrophysical systems, including portions of the interstellar medium, protostellar accretion disks, and the chromosphere of the Sun and other cool stars. Ambipolar drift redistributes magnetic flux, which can trigger star formation. It affects short wavelength interstellar turbulence, the structure of interstellar shocks, flow driven instabilities, and the nature of magnetic reconnection. Energy dissipated by ion-neutral friction can be an important source of heat. This chapter reviews ambipolar drift as a process and discusses some of the implications.

Zweibel, Ellen G.

329

Quantum diffusion  

SciTech Connect

We consider a simple quantum system subjected to a classical random force. Under certain conditions it is shown that the noise-averaged Wigner function of the system follows an integro-differential stochastic Liouville equation. In the simple case of polynomial noise-couplings this equation reduces to a generalized Fokker-Planck form. With nonlinear noise injection new ``quantum diffusion`` terms rise that have no counterpart in the classical case. Two special examples that are not of a Fokker-Planck form are discussed: the first with a localized noise source and the other with a spatially modulated noise source.

Habib, S.

1994-10-01

330

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

331

Review of cavity optomechanical cooling  

NASA Astrophysics Data System (ADS)

Quantum manipulation of macroscopic mechanical systems is of great interest in both fundamental physics and applications ranging from high-precision metrology to quantum information processing. For these purposes, a crucial step is to cool the mechanical system to its quantum ground state. In this review, we focus on the cavity optomechanical cooling, which exploits the cavity enhanced interaction between optical field and mechanical motion to reduce the thermal noise. Recent remarkable theoretical and experimental efforts in this field have taken a major step forward in preparing the motional quantum ground state of mesoscopic mechanical systems. This review first describes the quantum theory of cavity optomechanical cooling, including quantum noise approach and covariance approach; then, the up-to-date experimental progresses are introduced. Finally, new cooling approaches are discussed along the directions of cooling in the strong coupling regime and cooling beyond the resolved sideband limit.

Liu, Yong-Chun; Hu, Yu-Wen; Wong Chee, Wei; Xiao, Yun-Feng

2013-11-01

332

Electron transport theory of cavity ionization  

SciTech Connect

An electron transport equation is applied to the study of the cavity ionization phenomenon. It has been proved that the effect of the cavity on the energy spectrum of electrons inside this cavity can be attributed to an equivalent electron source uniformly distributed in the cavity. A formula for the energy spectrum of the equivalent electron source is obtained. The deposited energy due to the equivalent electron source in the cavity of the plate chamber has been calculated. The new theory, compared with experimental results, is better than the Spencer-Attix theory for describing the phenomenon of cavity ionization.

Zheng-Ming, L.

1980-10-01

333

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

334

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

335

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

336

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

337

Matrix metalloproteinases in the formation of human synovial joint cavities.  

PubMed Central

Matrix metalloproteinases (MMPs) have been implicated in tissue remodelling in growth and development. A histochemical study of human fetal limbs was undertaken to assess the presence, and consequently the possible role, of MMPs and their inhibitor TIMP-1 (tissue inhibitor of metalloproteinases-1) in synovial joint cavity formation. Cryostat sections of fetal limbs from 7 to 14 wk gestation were stained with specific antibodies to collagenase (MMP-1), gelantinases A (MMP-2) and B (MMP-9), stromelysin (MMP-3) and TIMP-1. Immunoreactive (IR) MMP-1, MMP-2 and MMP-3 were seen chiefly in chondrocytes, but in all cases in zones distant from the joint line before cavity formation. IR-MMP-1 and MMP-2 were also localised both in synovium and on the articular surfaces of joints after cavity formation. In addition IR-MMP-2 was seen in a "collar' of perichondrium alongside the hypertrophic zone of chondrocytes and weakly in bone marrow spaces. IR-MMP-9 was seen in neutrophil leucocytes and in bone marrow spaces. IR-TIMP-1 was generally distributed in connective tissue cells. No IR-MMP (1, 2,3 or 9) was seen along potential joint lines before or at the time of cavity formation, nor was there aspecific decrease in IR-TIMP-1 at this site. These findings confirm a role for metalloproteinases in developmental processes such as cartilage remodelling and bone marrow space formation. MMP-1 and MMP-2 may be involved in the remodelling of developing synovial tissue and the articular surfaces subsequent to cavity formation. However, we have failed to find evidence to indicate that the loss of tissue strength at the joint line which allows synovial joint cavity formation relates to high local levels of MMPS. Images Fig. 1 Fig. 2 PMID:8621334

Edwards, J C; Wilkinson, L S; Soothill, P; Hembry, R M; Murphy, G; Reynolds, J J

1996-01-01

338

RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS  

SciTech Connect

Circumstellar disks are thought to experience a rapid 'transition' phase in their evolution that can have a considerable impact on the formation and early development of planetary systems. We present new and archival high angular resolution (0.''3 {approx} 40-75 AU) Submillimeter Array (SMA) observations of the 880 {mu}m (340 GHz) dust continuum emission from 12 such transition disks in nearby star-forming regions. In each case, we directly resolve a dust-depleted disk cavity around the central star. Using two-dimensional Monte Carlo radiative transfer calculations, we interpret these dust disk structures in a homogeneous, parametric model framework by reproducing their SMA continuum visibilities and spectral energy distributions. The cavities in these disks are large (R{sub cav} = 15-73 AU) and substantially depleted of small ({approx}{mu}m-sized) dust grains, although their mass contents are still uncertain. The structures of the remnant material at larger radii are comparable to normal disks. We demonstrate that these large cavities are relatively common among the millimeter-bright disk population, comprising at least 1 in 5 (20%) of the disks in the bright half (and {>=}26% of the upper quartile) of the millimeter luminosity (disk mass) distribution. Utilizing these results, we assess some of the physical mechanisms proposed to account for transition disk structures. As has been shown before, photoevaporation models do not produce the large cavity sizes, accretion rates, and disk masses representative of this sample. A sufficient decrease of the dust optical depths in these cavities by particle growth would be difficult to achieve: substantial growth (to meter sizes or beyond) must occur in large (tens of AU) regions of low turbulence without also producing an abundance of small particles. Given those challenges, we suggest instead that the observations are most commensurate with dynamical clearing due to tidal interactions with low-mass companions-very young ({approx}1 Myr) brown dwarfs or giant planets on long-period orbits.

Andrews, Sean M.; Wilner, David J.; Espaillat, Catherine; Qi Chunhua; Brown, J. M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hughes, A. M. [Department of Astronomy, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Dullemond, C. P. [Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, Albert-Ueberle-Str. 2, Heidelberg 69120 (Germany); McClure, M. K. [Department of Astronomy, University of Michigan, 830 Dennison Bldg, 500 Church Street, Ann Arbor, MI 48109 (United States)

2011-05-01

339

Selective Advantage of Diffusing Faster  

NASA Astrophysics Data System (ADS)

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.

Pigolotti, Simone; Benzi, Roberto

2014-05-01

340

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.

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

2012-12-06

341

All-fiber cavity dumping.  

PubMed

Cavity dumping of an all-fiber laser system is demonstrated. The active element is a pulse-picker with nanosecond rise time consisting of a microstructured fiber with electrically driven internal electrodes. The device is used for intracavity polarization rotation and dumping through a polarization splitter. The optical flux is removed from the cavity within one roundtrip and most of the amplified spontaneous emission, spiking and relaxation oscillation that follow during the gain recovery phase of the laser are blocked from the output signal. PMID:19907544

Malmström, M; Yu, Z; Margulis, W; Tarasenko, O; Laurell, F

2009-09-28

342

A micropillar for cavity optomechanics  

E-print Network

We present a new micromechanical resonator designed for cavity optomechanics. We have used a micropillar geometry to obtain a high-frequency mechanical resonance with a low effective mass and a very high quality factor. We have coated a 60-$\\mu$m diameter low-loss dielectric mirror on top of the pillar and are planning to use this micromirror as part of a high-finesse Fabry-Perot cavity, to laser cool the resonator down to its quantum ground state and to monitor its quantum position fluctuations by quantum-limited optical interferometry.

Kuhn, A G; Ducloux, O; Chartier, C; Traon, O Le; Briant, T; Cohadon, P -F; Heidmann, A; Michel, C; Pinard, L; Flaminio, R

2011-01-01

343

A micropillar for cavity optomechanics  

E-print Network

We present a new micromechanical resonator designed for cavity optomechanics. We have used a micropillar geometry to obtain a high-frequency mechanical resonance with a low effective mass and a very high quality factor. We have coated a 60-$\\mu$m diameter low-loss dielectric mirror on top of the pillar and are planning to use this micromirror as part of a high-finesse Fabry-Perot cavity, to laser cool the resonator down to its quantum ground state and to monitor its quantum position fluctuations by quantum-limited optical interferometry.

A. G. Kuhn; M. Bahriz; O. Ducloux; C. Chartier; O. Le Traon; T. Briant; P. -F. Cohadon; A. Heidmann; C. Michel; L. Pinard; R. Flaminio

2011-07-19

344

Neurofibrosarcoma in the nasal cavity.  

PubMed

A nine month old male child presented with a swelling protruding from the right nasal cavity for two months. Other symptoms were mild breathlessness during suckling and blood stained nasal discharge. CT Scan sshowed a mass arising from the lasteral wall of the right nasal cavity with mild erosion of the adjacent bones. The tumor was excised with wide margin through a lateral rhinotomy approach under general anaesthesia. In histopathological examination it was found to be a low grade neurofibrosarcoma. The child recovered well and is free from any recurrence till the time of reporting. PMID:23119773

Goswami, S; Kundu, I N; Majumdar, P K; Saha, A K; Haider, B

2001-04-01

345

21 CFR 872.3260 - Cavity varnish.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

346

Optical cavity furnace for semiconductor wafer processing  

DOEpatents

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

Sopori, Bhushan L.

2014-08-05

347

Boundary layer influence on cavity noise generation.  

E-print Network

.koschatzky@tudelft.nl 1 Introduction The generation of noise by flow over a rectangular cavity is an important benchmark]. Experiments were conducted in a open jet wind tunnel facility. The cavity took place in a flat plate

Lindken, Ralph

348

Cavity-Enhanced Direct Frequency Comb Spectroscopy  

E-print Network

Cavity-Enhanced Direct Frequency Comb Spectroscopy: Technology and Applications Florian Adler-molecule spectroscopy, ultrasensitive spectroscopy, frequency-domain ultrafast spectroscopy Abstract Cavity-enhanced direct frequency comb spectroscopy combines broad band- width, high spectral resolution, and ultrahigh

349

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, André F. P.; Fares, Ehab

2014-06-01

350

Large-mode enhancement cavities.  

PubMed

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

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

2013-05-01

351

Improving cooling of cavity blackbodies  

NASA Astrophysics Data System (ADS)

A cavity blackbody is the appropriate IR reference source for IR sensors which require high radiance levels. It combines high emissivity independent from wavelength and high speed warm up and high stability thanks to its light trap structure. However, the inconvenient of this structure is that it leads to a prohibitive cooling time. HGH developed a method to speed up the cooling time.

Barrat, Catherine; Chauvel, Gildas

2013-10-01

352

Cavity ring-down Spectroscopy  

E-print Network

Cavity ring-down Spectroscopy Before and after frequency combs Kater Murch April 6, 2006 #12;Example: Basic Absorption Spectroscopy Laser Detector #12;Absorption Spectroscopy Want to know: Absorption Frequency Gives information about what and how much #12;Other possible methods · Photothermal Spectroscopy

Budker, Dmitry

353

Laser cavity dumping using an antiresonant ring  

Microsoft Academic Search

A new method for laser cavity dumping using an antiresonant ring laser cavity and an electrooptic phase modulator has been demonstrated on a CO2laser at 10.6 ?m. Experimental results are summarized and the cavity and modulator design considerations for this type of cavity dumping are reviewed in this paper. Although the initial experiments were done at 10.6 ?m, the antiresonant

R. Trutna; A. E. Siegman

1977-01-01

354

Numerical analysis of coupled photonic crystal cavities  

NASA Astrophysics Data System (ADS)

We numerically investigate the interaction dynamics of coupled cavities in planar photonic crystal slabs in different configurations. The single cavity is optimized for a long lifetime of the fundamental mode, reaching a Q-factor of ?43, 000 using the method of gentle confinement. For pairs of cavities we consider several configurations and present a setup with strongest coupling observable as a line splitting of about 30 nm. Based on this configuration, setups with three cavities are investigated.

Declair, S.; Meier, T.; Zrenner, A.; Förstner, J.

2011-10-01

355

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

356

Solitary fibrous tumor of the oral cavity with a predominant leiomyomatous-like pattern: A potential diagnostic pitfall.  

PubMed

The diagnosis of solitary fibrous tumor (SFT) is usually straightforward if the typical morphologic features, including a wide variety of growth patterns, are identified. We report the clinical, radiologic, and pathologic findings of a rare case of intraoral SFT which exhibited a predominant leiomyomatous-like appearance, closely reminiscent of a leiomyoma, at both incisional and excisional biopsy. Histologically, the tumor was composed predominantly of intersecting fascicles of eosinophilic spindle-shaped cells, variably set in a fibrous stroma. A focal hemangiopericytoma-like growth pattern with alternating hypercellular and hypocellular areas, as well as the deposition of dense keloid-type collagen, raising the suspicion of SFT, could be identified only after a careful examination of the whole tumor. Immunohistochemistry was helpful in confirming the diagnosis of SFT, revealing a diffuse staining of neoplastic cells for vimentin, CD34, bcl-2 protein, and, focally, CD99. Myogenic markers (alpha-smooth muscle actin, desmin, h-caldesmon) were not expressed. The pathologist should be aware of this variant of intraoral leiomyomatous-like SFT to avoid a misdiagnosis of leiomyoma. The distinction of SFT from leiomyoma in the oral cavity is important to assure both correct treatment and prognostic information. PMID:20188491

Amico, Paolo; Colella, Giuseppe; Rossiello, Raffaele; Maria Vecchio, Giada; Leocata, Pietro; Magro, Gaetano

2010-07-15

357

Organized Oscillations of Initially-Turbulent Flow Past a Cavity  

SciTech Connect

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

J.C. Lin; D. Rockwell

2002-09-17

358

The formation of cavity clusters at sheet cavity \\/ re-entrant jet contact  

Microsoft Academic Search

The fast flow of water past a hydrofoil often results in the formation of a sheet cavity on the suction side of the foil, and from its trailing edge a re-entrant jet develops and moves upstream into the cavity. Eventually this jet gets into contact with the cavity surface and causes the formation of small clouds of cavities at the

K. A. Mørch; G. Bark; P. L. Nielsen; M. Grekula; P. Stendys

359

Neural network and CFD-based optimisation of square cavity and curved cavity static labyrinth seals  

Microsoft Academic Search

The pressure drop characteristics for leakage of water through circular grooved, square cavity and curved cavity static labyrinth seals are investigated. A semi-theoretical model employing two new terms named virtual cavity velocity and vortex loss coefficient, to determine the pressure drop across the seal is presented. Five different square cavity labyrinth seals (SCLS) were subjected to flow visualisation tests to

S. P. Asok; K. Sankaranarayanasamy; T. Sundararajan; K. Rajesh; G. Sankar Ganeshan

2007-01-01

360

Metallodielectric nanopatch cavity with extended metal shields  

Microsoft Academic Search

We report that the radial extension of parallel metal plates can significantly suppress the radiation losses from the cylindrical metallodielectric nanopatch cavities. The improved quality factor can be obtained analytically, and therefore systematically optimized. Metallodielectric cavity; Quality factor; Nanolaser; Metal optics I. INTRODUCTION Metallodielectric cavity structures have been widely investigated for miniaturization of the integrated optical devices. Although surface plasmon

Jong-Bum You; Wook-Jae Lee; Kyoungsik Yu

2011-01-01

361

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

362

Laser cavity dumping using optical bistability  

Microsoft Academic Search

A scheme for passive cavity dumping of a laser is proposed in which one of the mirrors of the laser cavity is replaced by an optically bistable element. The dynamic behavior of the system is studied with a rate-equation model for the coupled laser and bistable cavities. The mean-field approximation, where traveling wave effects and the spatial dependence of the

J. Gea-Banacloche; W. W. Chow; M. O. Scully

1983-01-01

363

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

364

Many-Body Cavity QED Jonas Larson  

E-print Network

& Raimond, Exploting the Quantum (OUP). Jaynes-Cummings physics #12;Cavity QED Jaynes-Cummings Hamiltonian). Jaynes-Cummings physics Field energy Atomic energy Interaction energy #12;Cavity QED Vacuum Rabi splitting, 0± = ± (= 0) 8 Jaynes-Cummings physics Schoelkopf & Girvin, Nature 451 (2008). #12;Cavity QED

365

Cavity Quantum Electrodynamics: Coherence in Context  

Microsoft Academic Search

Modern cavity quantum electrodynamics (cavity QED) illuminates the most fundamental aspects of coherence and decoherence in quantum mechanics. Experiments on atoms in cavities can be described by elementary models but reveal intriguing subtleties of the interplay of coherent dynamics with external couplings. Recent activity in this area has pioneered powerful new approaches to the study of quantum coherence and has

H. Mabuchi; A. C. Doherty

2002-01-01

366

Air flow in cavities of labyrinth seals  

Microsoft Academic Search

The leakage flow rate through a sequence of labyrinth seal cavities, and the associated pressure and the circumferential velocity distributions are calculated for seals used in turbomachinery. Computational Fluid Dynamics is used to justify the use of bulk cavity variables, and to analyze the details of the flow in a single cavity under steady state, axisymmetric conditions. Periodic, analytic solutions

Dursun Eser; Jacob Y. Kazakia

1995-01-01

367

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

368

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

369

Stent hypersensitivity and infection in sinus cavities  

PubMed Central

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

Soufras, George D.; Hahalis, George

2013-01-01

370

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

371

Optical Material Characterization Using Microdisk Cavities  

NASA Astrophysics Data System (ADS)

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

Michael, Christopher P.

372

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

373

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

374

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

375

Numerical Analysis of Coupled Photonic Crystal Cavities  

NASA Astrophysics Data System (ADS)

We present an analysis of the coupling between photonic crystal cavities in different geometries. Inline-, side- and angle-coupled L3-geometries are investigated numerically in three dimensions. Asymmetric mode splitting of the fundamental mode for the L3-cavity is shown for all geometrical setups evidencing for strong cavity-cavity interactions. The coupling efficiency for the fundamental mode is shown to be best for a 30° angle between the cavity-centers due to the direction of in-plane leackage out of the cavites.

Declair, S.; Meier, T.; Förstner, J.

2010-10-01

376

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

377

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

378

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

379

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

380

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

381

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

SciTech Connect

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

2014-09-15

382

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

2014-09-01

383

Control of Cavity Resonance Using Oscillatory Blowing  

NASA Technical Reports Server (NTRS)

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

Scarfe, Alison Lamp; Chokani, Ndaona

2000-01-01

384

Coronal Cavity Catalog from SDO Observations  

NASA Astrophysics Data System (ADS)

We present a catalog of coronal cavities and prominences associated with cavities since the launch of Solar Dynamics Observatory (SDO). Coronal cavities are dark, circular regions observed above the solar limb in white light and EUV coronal images. They are believed to be regions of lower density relative to the surrounding corona. We use synoptic maps made from EUV images from the Atmospheric Imager Assembly (AIA) instrument on board SDO to study coronal cavities. The synoptic maps, constructed from annuli above the solar limb, best show cavities in 211 A (Fe XIV, 2.0 MK) and 193 A (Fe XII, 1.6 MK) and 171 A (Fe IX, 0.6 MK) passbands. Moreover, 304 A (He II, 0.05 MK) synoptic maps best show the evolution of any prominences associated with a cavity. The catalog lists the number of cavities seen in each Carrington rotation starting from CR 2097, the cavity’s size, shape, and the heliographic longitudes and latitudes of the appearance and disappearance of the cavity. Our goal is to provide a consistent set of the cavity structures for broad scientific use.

Karna, Nishu; Zhang, Jie; Pesnell, William D; Hess Webber, Shea A.

2014-06-01

385

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

386

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

387

STRUCTURAL ANALYSIS OF SUPERCONDUCTING ACCELERATOR CAVITIES  

SciTech Connect

The static and dynamic structural behavior of superconducting cavities for various projects was determined by finite element structural analysis. The {beta} = 0.61 cavity shape for the Neutron Science Project was studied in detail and found to meet all design requirements if fabricated from five millimeter thick material with a single annular stiffener. This 600 MHz cavity will have a Lorentz coefficient of {minus}1.8 Hz/(Mv/meter){sup 2} and a lowest structural resonance of more than 100 Hz. Cavities at {beta} = 0.48, 0.61, and 0.77 were analyzed for a Neutron Science Project concept which would incorporate 7-cell cavities. The medium and high beta cavities were found to meet all criteria but it was not possible to generate a {beta} = 0.48 cavity with a Lorentz coefficient of less than {minus}3 Hz/(Mv/meter){sup 2}.

D. SCHRAGE

2000-08-01

388

Hom dampers for ALS storage ring RF cavities  

SciTech Connect

The main source of narrowband impedance in the Advanced Light Source (ALS) are higher order modes (HOMs) of the two main RF and three third harmonic cavities. These HOMs drive longitudinal and transverse coupled bunch instabilities, which are controlled using active beam feedback systems. The dominant longitudinal HOMs in both systems are TM011-like modes with the R/Q factor an order of magnitude higher than all other longitudinal modes. To reduce the growth rates within the range of the longitudinal feedback system (LFB), these modes were tuned away from beam resonances by means of cooling water temperature control (main rf system), and the combination of two tuners (third harmonic system). To improve the reliability of the longitudinal dampening system, we have built and installed E-type HOM dampers for the fundamental and harmonic cavities. We present the design, commissioning and performance of the HOM dampers in this paper.

Kwiatkowski, S.; Baptiste, K.; Byrd, J.; DeSantis, S.; Julian, J.; Low, R.; Lyn, L.; Plate, D.

2003-05-08

389

Spontaneous Photon Emission in Cavities  

E-print Network

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.

Gernot Alber; Nils Trautmann

2014-12-04

390

A micropillar for cavity optomechanics  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

391

Some Nuclear Calculations of U-235-D2O Gaseous-Core Cavity Reactors  

NASA Technical Reports Server (NTRS)

The results of a multigroup, diffusion theory study of spherical gaseous-core cavity reactors are presented in this report. The reactor cavity of gaseous U235 is enclosed by a region of hydrogen gas and is separated from an external D2O moderator-reflector by a zirconium structural shell. Some cylindrical reactors are also investigated. A parametric study of spherical reactors indicates that, for the range of variables studied, critical mass increases as: (1) Fuel region is compressed within the reactor cavity, (2) moderator thickness is decreased, (3) structural shell thickness is increased, and (4) moderator temperature is increased. A buckling analogy is used to estimate the critical mass of fully reflected cylindrical reactors from spherical results without fuel compression. For a reactor cavity of a 120-centimeter radius uniformly filled with fuel, no structural shell, a moderator temperature of 70 F, and a moderator thickness of 100 centimeters, the critical mass of a spherical reactor is 3.1 kilograms while that of a cylinder with a length-to-diameter ratio of 1.0 (L/D = 1) is approximately 3.8 kilograms and, with L/D = 2, 5.9 kilograms. For the range of variables considered for U235-D2O gaseous-core cavity reactors, the systems are characterized by 95 to 99 percent thermal absorptions, with the flux reaching a maximum in the moderator about 10 to 15 centimeters from the reactor cavity.

Ragsdale, Robert G.; Hyland, Robert E.

1961-01-01

392

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

393

Improving Radiometer-Cavity Absorptance  

NASA Technical Reports Server (NTRS)

In improved cavity radiometer, each sensor cone ends in small tube so that black paint cannot form truncating meniscus. Inner diameter of tube is 0.25 mm; its outer diameter is 0.5 mm. During painting process, excess paint is drawn out through tube, preventing formation of meniscus at apex. After paint is cured, end of tube is crimped shut to form effective light trap.

Wilson, R. C.

1982-01-01

394

Diseases of the nasal cavity.  

PubMed

Conditions of this portion of the respiratory tract are relatively uncommon. This article reviews these conditions and discusses the different modes of therapy. The conditions covered are redundant alar folds, diseases of the nasal septum, fungal infections, neoplasms, nasal polyps, and ethmoid hematomas. The different surgical approaches to the nasal cavity are reviewed, and surgery of removal of the nasal septum and the alar fold are described. PMID:8472195

Nickels, F A

1993-04-01

395

High reflectance laser resonator cavity  

SciTech Connect

A method for making an alumina ceramic body for use in a laser to provide a pump cavity is described wherein laser radiation at a lasing wavelength is produced, the method comprising the step of sintering alumina powder at a temperature of between about 1300/sup 0/-1425/sup 0/C for a sufficient time to form a sintered alumina ceramic body having grain sizes of between about 0.3 to 0.5 microns.

Gibson, J.O.; Gearhart, V.C.; Birrell, S.E.; Hawrylow, G.M.

1989-02-14

396

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

397

Relativistic Split-Cavity Oscillator  

E-print Network

Using the method of small signal analysis, we study the application potential of relativistic electron beams in split-cavity oscillators (SCO's). A beam-energy change in the SCO as a function of the initial energy of a relativistic beam is considered. It is shown that the small-signal analysis method enables adequate evaluation of SCO parameters needed for effective modulation of a relativistic beam in a split cavity and for HPM generation using SCO's. The range of energies is found for which the effect of self-modulation of the beam density in SCO structures is most pronounced. It is also shown that for beam currents at which the space charge has little effect on the motion of electrons in a beam, the beam in a split-cavity oscillator is effectively self-modulated at beam energies less than ~300-400 keV. The self-modulation drops sharply in the range of energies from 250 to 400 keV, but as the beam current is increased, the effective beam self-modulation becomes appreciable in this range too, as well as even...

Baryshevsky, V G

2014-01-01

398

Analysis of hydrodynamic phenomena in simulant experiments investigating cavity interactions following postulated vessel meltthrough  

SciTech Connect

An analysis of hydrodynamic phenomena in simulant experiments examining aspects of ex-vessel material interactions in a PWR reactor cavity following postulated core meltdown and localized breaching of the reactor vessel has been carried out. While previous analyses of the tests examined thresholds for the onset of sweepout of fluid from the cavity, the present analysis considers the progression of specific hydrodynamic phenomena involved in the dispersal process: crater formation due to gas jet impingement, radial wave motion and growth, entrainment and transport of liquid droplets, liquid layer formation due to droplet recombination, fluidization of liquid remaining in the cavity, removal of fluidized liquid droplets from the cavity, and the ultimate removal of the remaining liquid layer within the tunnel passageway. Phenomenological models which may be used to predict the phenomena are presented.

Sienicki, J.J.; Spencer, B.W.

1984-01-01

399

Supersonic diffuser for pressure recovery in SCOIL system  

NASA Astrophysics Data System (ADS)

Classical supersonic chemical oxygen iodine laser (SCOIL) systems operate under a low total pressure of nearly 18 Torr (2400 Pa) with cavity pressure being in the range 3 Torr (400 Pa) and Mach number of 1.7. These systems handle high flow rates and hence an efficient supersonic diffuser (SD) is a critical first step towards an open-cycle operation, which may be followed by a multi-stage ejector system. The present study discusses the various aspects in the design of a supersonic diffuser for a twin 10 kW COIL module source which employs flow rates of 100 gs -1 in each module. The results of computational studies based on 3-D, viscos compressible flow, k- ? turbulence formulation for the supersonic diffuser geometry have also been discussed. The experimental results from a single-module test of the supersonic diffuser show that a total recovered pressure of nearly 7 Torr is achieved at the diffuser exit.

Singhal, Gaurav; Mainuddin; Rajesh, R.; Tyagi, R. K.; Dawar, A. L.

2010-02-01

400

Knowledge diffusion in the collaboration hypernetwork  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

401

Generation of a Dual-Functioning Antitumor Immune Response in the Peritoneal Cavity  

PubMed Central

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.

2014-01-01

402

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

403

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

404

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

405

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

406

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

407

Diffusion tensor MRI phantom exhibits anomalous diffusion.  

PubMed

This paper reports diffusion weighted MRI measurements of cyclohexane in a novel diffusion tensor MRI phantom composed of hollow coaxial electrospun fibers (average diameter 10.2 ?m). Recent studies of the phantom demonstrated its potential as a calibration standard at low b values (less than 1000 s/mm<;sup>2<;/sup>) for mean diffusivity and fractional anisotropy. In this paper, we extend the characterization of cyclohexane diffusion in this heterogeneous, anisotropic material to high b values (up to 5000 s/mm<;sup>2<;/sup>), where the apparent diffusive motion of the cyclohexane exhibits anomalous behavior (i.e., the molecular mean squared displacement increases with time raised to the fractional power 2?/?). Diffusion tensor MRI was performed at 9.4 T using an Agilent imaging scanner and the data fit to a fractional order Mittag-Leffler (generalized exponential) decay model. Diffusion along the fibers was found to be Gaussian (2?/?=l), while diffusion across the fibers was sub-diffusive (2?/?<;l). Fiber tract reconstruction of the data was consistent with scanning electron micrograph images of the material. These studies suggest that this phantom material may be used to calibrate MR systems in both the normal (Gaussian) and anomalous diffusion regimes. PMID:25570066

Ye, Allen Q; Hubbard Cristinacce, Penny L; Feng-Lei Zhou; Ziying Yin; Parker, Geoff J M; Magin, Richard L

2014-08-01

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. 5 figs.

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

1995-12-26

409

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

410

Subwavelength Nanopatch Cavities for Semiconductor Plasmon Lasers  

NASA Astrophysics Data System (ADS)

We propose and analyze a family of nanoscale cavities for electrically-pumped surface-emitting semiconductor lasers that use surface plasmons to provide optical mode confinement in cavities which have dimensions in the 100-300 nm range. The proposed laser cavities are in many ways nanoscale optical versions of micropatch antennas that are commonly used at microwave/RF frequencies. Surface plasmons are not only used for mode confinement but also for output beam shaping to realize single-lobe far-field radiation patterns with narrow beam waists from subwavelength size cavities. We identify the cavity modes with the largest quality factors and modal gain, and show that in the near-IR wavelength range (1.0-1.6 microns) cavity losses (including surface plasmon losses) can be compensated by the strong mode confinement in the gain region provided by the surface plasmons themselves and the required material threshold gain values can be smaller than 700 1/cm.

Manolatou, Christina; Rana, Farhan

2008-05-01

411

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

412

Turbine disk cavity aerodynamics and heat transfer  

NASA Technical Reports Server (NTRS)

Experiments were conducted to define the nature of the aerodynamics and heat transfer for the flow within the disk cavities and blade attachments of a large-scale model, simulating the Space Shuttle Main Engine (SSME) turbopump drive turbines. These experiments of the aerodynamic driving mechanisms explored the following: (1) flow between the main gas path and the disk cavities; (2) coolant flow injected into the disk cavities; (3) coolant density; (4) leakage flows through the seal between blades; and (5) the role that each of these various flows has in determining the adiabatic recovery temperature at all of the critical locations within the cavities. The model and the test apparatus provide close geometrical and aerodynamic simulation of all the two-stage cavity flow regions for the SSME High Pressure Fuel Turbopump and the ability to simulate the sources and sinks for each cavity flow.

Johnson, B. V.; Daniels, W. A.

1992-01-01

413

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

414

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

415

Performance of Single Crystal Niobium Cavities  

SciTech Connect

We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other cavities of the scaled "Low Loss" (LL) shape (two) and "High Gradient" (HG) shape (one) resonated at 2.3 GHz and were fabricated from "as received" single crystals, both from Heraeus and CBMM niobium. After appropriate surface treatments by buffered chemical polishing and electropolishing most cavities performed quite nicely and peak surface magnetic fields of ~ 160 mT or above corresponding to accelerating gradients between 38 MV/m and 45 MV/m were reached. This paper reports about the performance of these cavities.

Kneisel, Peter; Ciovati, Gianluigi; Singer, Waldemar; Singer, Xenia; Reschke, Detlef; Brinkmann, A.

2008-07-01

416

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

417

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

418

Cavities  

MedlinePLUS

... decay. The most common decay-causing bacteria are Streptococcus mutans . Spotlight on Aging Only a generation ago, ... teeth. Whenever sugar comes in contact with plaque, Streptococcus mutans bacteria in the plaque produce acid. The ...

419

Superconducting cavity development at Legnaro  

SciTech Connect

10 years after the construction at LNL of its first superconducting resonator, the laboratory has become one of the leading centers in the development of low beta superconducting cavities, including superconducting rfqs. The technologies of bulk niobium, niobium sputtering and lead plating have been used and some of the innovations introduced in the field during the last decade have been developed at LNL. The present technology allows producing cavities that can reach more than 50 MV/m peak surface electric field, both in test cryostats and after installation in the linac. New techniques have been developed to minimize the resonators construction cost, like spinning of multicell cavities, modular design of quarter wave resonators and niobium sputtering on copper: these technologies have reached a high level of performance and reliability. A new technique of mechanical damping was developed for stabilization of large size quarter wave resonators. The lead plating technique was enriched by the stabilization of the lead surface against oxidation. The construction of the first superconducting rfq to be used in an accelerator facility, which required original solutions to the new kind of problems emerging from this project, is at an advanced stage. Recent results obtained at LNL show that the goal of operating superconducting low beta resonators at 8 MV/m in cw mode can be presently reached; future low beta linacs could be designed with an accelerating field which is about two times higher than the one required in the past, with a significant cost reduction that could make these machines affordable also for small laboratories.

Facco, A. [INFN-Laboratori Nazionali di Legnaro, Via Romea, 4, I-35020 Legnaro, Padova (Italy)

1999-04-26

420

Subwavelength Nanopatch Cavities for Semiconductor Plasmon Lasers  

Microsoft Academic Search

We propose and analyze a family of nanoscale cavities for electrically-pumped surface-emitting semiconductor lasers that use surface plasmons to provide optical mode confinement in cavities which have dimensions in the 100-300 nm range. The proposed laser cavities are in many ways nanoscale optical versions of micropatch antennas that are commonly used at microwave\\/RF frequencies. Surface plasmons are not only used

Christina Manolatou; Farhan Rana

2008-01-01

421

Vertical-external-cavity semiconductor lasers  

Microsoft Academic Search

Surface-emitting semiconductor lasers can make use of external cavities and optical pumping techniques to achieve a combination of high continuous-wave output power and near-diffraction-limited beam quality that is not matched by any other type of semiconductor source. The ready access to the laser mode that the external cavity provides has been exploited for applications such as intra-cavity frequency doubling and

A C Tropper; H D Foreman; A Garnache; K G Wilcox; S H Hoogland

2004-01-01

422

Unidirectional semiconductor ring lasers with racetrack cavities  

SciTech Connect

We report the development of racetrack-cavity semiconductor ring lasers that operate unidirectionally by means of an active crossover waveguide. These racetrack-cavity lasers show improved performance over previous circular-cavity unidirectional ring lasers with continuous-wave single-frequency output powers of [ge]10 mW, and with up to 99% of the lasing output emitted from the preferred ring direction.

Hohimer, J.P.; Vawter, G.A. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1993-11-01

423

Microphonics measurements in SRF cavities for RIA  

Microsoft Academic Search

Phase stabilization of the RIA drift tube cavities in the presence of microphonics will be a key issue for RIA. Due to the relatively low beam currents (?0.5 pmA) required for the RIA driver, microphonics will impact the rf power required to control the cavity fields. Microphonics measurements on the ANL ?=0.4 single spoke cavity and on the ANL ?=0.4

M. P. Kelly; K. W. Shepard; M. Kedzie; J. D. Fuerst; S. Sharamentov; Jean Delayen

2003-01-01

424

Soft X-ray laser cavities  

Microsoft Academic Search

We report progress in the development of multilayer components for use in multiple pass soft X-ray laser cavities operating in the 100A to 300A spectral range. Our work includes fabrication and characterization of multilayer components; simple resonant cavity design; damage threshold assessment for multilayers in the X-ray laser environment; and multipass cavity experiments for efficiency enhancement and transverse mode selection.

N. M. Ceglio; D. G. Stearns; A. M. Hawryluk; T. M. Barbee; K. Danzmann; M. Kuehne; P. Mueller; B. Wende; M. B. Stearns; A. K. Petford-Long; C.-H. CHANG

1986-01-01

425

Observing the unobservable? Modeling coronal cavity densities  

NASA Astrophysics Data System (ADS)

Prominence cavities in coronal helmet streamers are readily detectable in white light coronagraph images, yet their interpretation may be complicated by projection effects. In order to determine a cavity's density structure, it is essential to quantify the contribution of non-cavity features along the line of sight. We model the coronal cavity as an axisymmetric torus that encircles the Sun at constant latitude, and fit it to observations of a white light cavity observed by the Mauna Loa Solar Observatory (MLSO) MK4 coronagraph from January 25-30, 2006. We demonstrate that spurious non-cavity contributions (including departures from axisymmetry) are minimal enough to be incorporated in a density analysis as conservatively estimated uncertainties in the data. We calculate a radial density profile for cavity material and for the surrounding helmet streamer (which we refer to as the "cavity rim"), and find that the cavity density is depleted by a maximum of 40 percent compared to the surrounding helmet streamer at low altitudes (1.18 solar radii), but is consistently higher (double or more) than in coronal holes. We also find that the relative density depletion between cavity and surrounding helmet decreases as a function of height. We show that both increased temperature in the cavity relative to the surrounding helmet streamer and a magnetic flux rope configuration might lead to such a flattened density profile. Finally, our model provides general observational guidelines that can be used to determine when a cavity is sufficiently unobstructed to be a good candidate for plasma diagnostics.

Fuller, J.; Gibson, S. E.; Detoma, G.; Fan, Y.

2008-05-01

426

FDTD simulation of hexagonal micropillar cavities  

Microsoft Academic Search

Hexagonal micropillar (µ-pillar) cavities have been studied using 2-D finite-difference time-domain (FDTD) method. Singlemode resonances have been observed from a 2-µm sized hexagonal µ-pillar cavity that is selectively input-coupled. The simulated resonance wavelengths are consistent with the wavefront-matching condition based on ray-optics. The resonant field distribution has an integer number of field maxima along the cavity rim similar to whispering-gallery

Frankie K. L. Tung; Ning Ma; Andrew W. Poon

2003-01-01

427

Compact Superconducting Crabbing and Deflecting Cavities  

SciTech Connect

Recently, new geometries for superconducting crabbing and deflecting cavities have been developed that have significantly improved properties over those the standard TM{sub 110} cavities. They are smaller, have low surface fields, high shunt impedance and, more importantly for some of them, no lower-order-mode with a well-separated fundamental mode. This talk will present the status of the development of these cavities.

De Silva, Payagalage Subashini Uddika [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States) and Old Dominion University, Norfolk, VA (United States)

2012-09-01

428

Transonic separated flow around a cavity  

Microsoft Academic Search

Unsteady flow over shallow cavities (L\\/D = 4 and L\\/D = 8) at Mach = 0.8 is investigated experimentally. Data acquisition in and above two-dimensional rectangular cavities is accomplished optically via a multiple exposed Shack Hartman sensor. This technique provides a time-accurate picture of the density behavior in and above the cavity without the need to insert any type of

John Dominique Martel

2001-01-01

429

Basketballs as spherical acoustic cavities  

NASA Astrophysics Data System (ADS)

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

Russell, Daniel A.

2010-06-01

430

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

2010-06-30

431

Mass renormalization in cavity QED  

SciTech Connect

We show that the presence of a background medium and a boundary surface or surfaces in cavity QED produces no change in the energy shift of a free charged particle due to its coupling to the fluctuating electromagnetic field of the vacuum. This clarifies that the electromagnetic and the observed mass of the charged particle are not affected by the modification of the field of the vacuum. The calculations are nonrelativistic and restricted to the dipole approximation but are otherwise based on the general requirements of causality.

Matloob, Reza [Department of Physics, University of Kerman, Kerman (Iran, Islamic Republic of)

2011-01-15

432

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

433

A selective medium for Rothia mucilaginosa and its distribution in oral cavities.  

PubMed

A selective medium for Rothia mucilaginosa (RMSM) was developed to examine the population of R. mucilaginosa in oral cavities. The growth recovery of R. mucilaginosa on RMSM was 85.1% relative to HI medium. R. mucilaginosa was detected at 3.4% of total bacteria from stimulated saliva of 8 subjects. PMID:22995714

Kobayashi, Taira; Uchibori, Satoshi; Tsuzukibashi, Osamu; Goto, Haruhiko; Aida, Masahiro

2012-12-01

434

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

435

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

436

Frequency doubled, cavity dumped feedback laser  

SciTech Connect

This patent describes an apparatus for efficient frequency doubling while cavity dumping a pumped laser in a resonator cavity in order to produce modulated output light pulses. The apparatus consists of: a laser having a pumped gain medium in the resonator cavity for emitting light at a first frequency on a fixed axis between two mirrors, modulating means placed between one of the two mirrors and the gain medium for deflecting light in the resonant cavity along a path at a fixed angle with respect to the fixed axis between the two mirrors in response to a cavity-dumping control signal, a third mirror placed to receive resonant cavity light deflected by the modulating means, and to redirect it back on the same path, frequency doubling means placed in the deflected light path between the modulating means and the third mirror, and beamsplitting means placed between the frequency doubling means and the modulating means for separating out frequency doubled light as a modulated output pulse, and passing undoubled frequency light through the modulating means and the gain medium, whereby light in the resonator cavity between the two mirrors experiences cavity dumping and frequency doubling while transmitting a modulated pulse of light reflected from the third mirror and redirection of undoubled frequency light into the resonator cavity while transmitting the modulated pulse of light for greater efficiency.

Sipes, D.L. Jr.; Robinson, D.L.

1989-06-20

437

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

438

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

439

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

440

Secure Quantum Dialogue via Cavity QED  

NASA Astrophysics Data System (ADS)

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

Ye, Tian-Yu

2015-03-01

441

Interaction of cavities and dislocations in semiconductors  

SciTech Connect

TEM of He-implanted Si-Ge and InGaAs indicates an attractive interaction between cavities and dislocations. Calculation indicates that cavities are attracted to dislocations through surrounding strain fields, and strong binding (100s of eV) occurs when a cavity intersects the core. In a strained SiGe/Si heterostructure, He implantation enhances relaxation rates and cavities bound to misfit dislocations show evidence of increasing relaxation at equilibrium by lowering dislocation energies. The interaction is expected for all crystalline solids and gives insight into voids in GaN/sapphire and bubbles in He-implanted metals.

Follstaedt, D.M.; Myers, S.M.; Lee, S.R.; Reno, J.L.; Dawson, R.L.; Han, J.

1996-12-31

442

Mechanical Properties of Ingot Nb Cavities  

SciTech Connect

This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

2014-07-01

443

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

444

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

445

Cavity-controlled radiative recombination of excitons in thin-film solar cells  

NASA Astrophysics Data System (ADS)

We study the performance of photovoltaic devices when controlling the exciton radiative recombination time. We demonstrate that when high-quantum-yield fluorescent photovoltaic materials are placed within an optical cavity, the spontaneous emission of the radiative exciton is partially inhibited. The corresponding increase of the exciton lifetime results in an increase of the effective diffusion length and diffusion current. This performance maximizes when the thickness of the cell is comparable to the absorption length. We show that when typical parameter values of thin solar-cell devices are used, the efficiency may improve by as much as three times.

Vuong, Luat T.; Kozyreff, Gregory; Betancur, Rafael; Martorell, Jordi

2009-12-01

446

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

447

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 which occurs in three dimensions. We present our recent results on restricted diffusion. We look into the role of geometrical complexity at different levels, from boundary microroughness to hierarchical structure and connectivity of the whole diffusion-confining domain. We develop a new approach which consists in combining fast random walk algorithms with spectral tools. The main focus is on studying diffusion in model complex geometries (von Koch boundaries, Kitaoka acinus, etc.), as well as on developing and testing spectral methods. We aim at extending this knowledge and at applying the accomplished arsenal of theoretical and numerical tools to structures found in nature and industry.

Denis Grebenkov

2009-09-08

448

Nd3+ ion diffusion during sintering of Nd:YAG transparent ceramics  

SciTech Connect

Using an electron microprobe, we measured and characterized the Nd{sup 3+} ion diffusion across a boundary between Nd doped and undoped ceramic yttrium aluminum garnet (YAG) for different temperature ramps and hold times and temperatures. The results show significant Nd ion diffusion on the order of micrometers to tens of micrometers depending on the time and temperature of sintering. The data fit well a model including bulk diffusion, grain boundary diffusion and grain growth. Grain boundary diffusion dominates and grain growth limits grain boundary diffusion by reducing the total cross sectional area of grain boundaries.

Hollingsworth, J P; Kuntz, J D; Soules, T F

2008-10-24

449

Contributions to the mathematical biophysics of organic form I. Formation of cavities in cellular aggregates  

Microsoft Academic Search

The action of diffusion forces in aggregates of metabolising cells is studied mathematically, and it is shown that under definite\\u000a conditions these forces may lead to the formation of inner cavities inside of the cellular aggregate. Different quantitative\\u000a relations are derived and the possible bearing of these results on some embryological phenomena is discussed. A possible application\\u000a of these considerations

N. Rashevsky

1940-01-01

450

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.

451

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

452

Silicon Integrated Cavity Optomechanical Transducer  

NASA Astrophysics Data System (ADS)

Cavity optomechanics enables measurements of mechanical motion at the fundamental limits of precision imposed by quantum mechanics. However, the need to