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1

Cavity growth in soft adhesives  

NASA Astrophysics Data System (ADS)

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

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

2005-08-01

2

Thermomechanical cavity-growth modeling  

SciTech Connect

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 plane 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.

1982-01-01

3

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

4

The effects of segregation on the kinetics of irrtergranular cavity growth under creep conditions  

NASA Astrophysics Data System (ADS)

Intergranular cavity growth under creep conditions is examined with particular reference to the potential effects of segregation on cavity growth. When cavities are present on all of the boundaries in a polycrystalline solid, they are able to grow in an unconstrained manner. Under these conditions the rate of cavity growth may be controlled by grain boundary diffusion ( D GB), surface diffusion ( D S), or power law creep, which in turn is controlled by lattice diffusion ( D L). When only isolated boundaries are cavitated, cavity growth is constrained and may be completely limited by creep flow of the surrounding grains. The segregation of solute to the grain boundary and the cavity surface can influence the kinetics of cavity growth in several different ways. The reduction in surface energy associated with segregation can increase the rate of cavity growth when the cavities are crack-like. The effects of segregation on grain boundary and surface diffusion can also influence the rate of cavity growth. A phenomenological relation proposed by Borisov et al indicates that D GB /DL decreases with segregation, thus causing grain boundary diffusion controlled cavity growth to be slowed by segregation. In some cases solute additions increase D L, thus increasing the rate of creep controlled cavity growth. When these effects are sufficiently large, D GB can increase with solute additions, in spite of the effect of segregation. In some alloys D S increases with segregation by several orders of magnitude. Similar effects on cavity growth are not expected even for surface diffusion controlled cavity growth because the rate of cavity growth is limited by other factors when D S is very large.

Nix, W. D.; Yu, K. S.; Wang, J. S.

1983-03-01

5

The effects of segregation on the kinetics of intergranular cavity growth under creep conditions  

SciTech Connect

Intergranular cavity growth under creep conditions is examined with particular reference to the potential effects of segregation on cavity growth. When cavities are present on all of the boundaries in a polycrystalline solid, they are able to grow in an unconstrained manner. Under these conditions the rate of cavity growth may be controlled by grain boundary diffusion (D /SUB GB/ ), surface diffusio (D /SUB S/ ), or power law creep, which in turn is controlled by lattice diffusion (D /SUB L/ ). When only isolated boundaries are cavitated, cavity growth is constrained and may be completely limited by creep flow of th surrounding grains. The segregation of solute to the grain boundary and the cavity surface can influence the kinetics of cavity growth in several different ways. The reduction in surface energy associated with segregation can increase the rate of cavity growth when the cavities are crack-like. The effects of segregation on grain boundary and surface diffusion can also influence the rate of cavity growth. A phenomenological relation proposed by Borisov et al indicates that D /SUB GB/ /D /SUB L/ decrease with segregation, thus causing grain boundary diffusion controlled cavity growth to be slowed by segregation. In some cases solute additions increase D /SUB L/ , thus increasing the rate of creep controlled cavity growth. When these effects are sufficiently large, D /SUB GB/ can increase with solute additions, in spite of the effect of segregation. In some alloys D /SUB S/ increases with segregation by several orders of magnitude. Similar effects on cavity growth are not expected even for surface diffusion controlled cavity growth because the rate of cavity growth is limited by other factors when D /SUB S/ is very large.

Nix, W.D.; Wang, J.S.; Yu, K.S.

1983-04-01

6

ICT DIFFUSION AND GROWTH  

Microsoft Academic Search

The ICT revolution has been regarded as one of the determinants of the late 1990's spectacular growth performance of the U.S. Capital deepening and increase in TFP are the main roads through which the diffusion of ICT has affected the supply side of the economy. Only recently, official data on investment and capital stock that distinguish between ICT and non

Federico Biagi

7

Gas Diffusion Studies in Steady and Nonsteady Cavities.  

National Technical Information Service (NTIS)

These pages present a study of gaseous diffusion into and turbulent entrainment from steady as well as nonsteady fully cavitating flows and characterize the nonsteady cavity as a dynamic element in a water tunnel test section. An approximate theoretical a...

B. R. Parkin K. Ravindra

1987-01-01

8

Thermomechanical cavity-growth modeling  

Microsoft Academic Search

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

R. E. Glass

1982-01-01

9

Cavity growth patterns on the partial seam crip test  

Microsoft Academic Search

The Partial Seam CRIP (PSC) test conducted by Lawrence Livermore National Laboratories was characterized by two distinctly different types of cavity growth. Portions of the thermal data from the test have been analyzed using conduction models to infer the dynamics of the cavity growth. Growth during the first phase of the test was characterized by rapid movement of the process

Hommert

1984-01-01

10

Effective optical path length investigation for cubic diffuse cavity as gas absorption cell  

NASA Astrophysics Data System (ADS)

A simple cubic-shaped cavity with a high-diffuse-reflectivity inner coating as a novel gas detection cell was developed. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy. The law for a spherical cavity was applied and modified to a cubic cavity as a function of reflectivity ?, port fraction f, and the side length. Single-pass average path length of the cubic cavity was 0.723(7) times the side length. EOPL can be modified conveniently by adjusting the parameters of the cavity.

Yu, Jia; Zheng, Fu; Gao, Qiang; Li, Yinjie; Zhang, Yungang; Zhang, Zhiguo; Wu, Shaohua

2013-10-01

11

Grain boundary cavity growth under applied stress and internal pressure  

SciTech Connect

The growth of grain boundary cavities under applied stress and internal gas pressure was investigated. Methane gas filled cavities were produced by the C + 4H reversible CH4 reaction in the grain boundaries of type 270 nickel by hydrogen charging in an autoclave at 500/sup 0/C with a hydrogen pressure of either 3.4 or 14.5 MPa. Intergranular fracture of nickel was achieved at a charging temperature of 300/sup 0/C and 10.3 MPa hydrogen pressure. Cavities on the grain boundaries were observed in the scanning electron microscope after fracture. Photomicrographs of the cavities were produced in stereo pairs which were analyzed so as to correct for perspective distortion and also to determine the orientational dependence of cavity growth under an applied tensile stress.

Mancuso, J.F.

1977-08-01

12

Cavity growth patterns on the partial seam crip test  

SciTech Connect

The Partial Seam CRIP (PSC) test conducted by Lawrence Livermore National Laboratories was characterized by two distinctly different types of cavity growth. Portions of the thermal data from the test have been analyzed using conduction models to infer the dynamics of the cavity growth. Growth during the first phase of the test was characterized by rapid movement of the process to the top of the seam. The growth patterns during this time were remarkably similar to those observed on the Hoe Creek III test. Cavity growth observed later in the test, after the CRIP maneuver and when the horizontal production was in use, showed more lateral extent within the seam similar to patterns that were observed on the Hanna UCG tests. This type of growth resulted in improved process efficiency, at least for the early post-CRIP period. Calculations using a thermal-mechanical growth model are consistent with both types of growth observed. In particular, when stringers that were present in the seam are included in the model calculations, the more favorable growth patterns observed in the test are predicted. It is concluded that non-coal layers within the seam have the potential to significantly affect cavity growth and thus their presence should be accounted for when designing a process. 11 references, 10 figures, 1 table.

Hommert, P.J.

1984-01-01

13

The central cavity in trimeric glutamate transporters restricts ligand diffusion  

PubMed Central

A prominent aqueous cavity is formed by the junction of three identical subunits in the excitatory amino acid transporter (EAAT) family. To investigate the effect of this structure on the interaction of ligands with the transporter, we recorded currents in voltage-clamped Xenopus oocytes expressing EAATs and used concentration jumps to measure binding and unbinding rates of a high-affinity aspartate analog that competitively blocks transport (?-2-fluorenyl-aspartylamide; 2-FAA). The binding rates of the blocker were approximately one order of magnitude slower than l-Glu and were not significantly different for EAAT1, EAAT2, or EAAT3, but 2-FAA exhibited higher affinity for the neuronal transporter EAAT3 as a result of a slower dissociation rate. Unexpectedly, the rate of recovery from block was increased by l-Glu in a saturable and concentration-dependent manner, ruling out a first-order mechanism and suggesting that following unbinding, there is a significant probability of ligand rebinding to the same or neighboring subunits within a trimer. Consistent with such a mechanism, coexpression of wild-type subunits with mutant (R447C) subunits that do not bind glutamate or 2-FAA also increased the unblocking rate. The data suggest that electrostatic and steric factors result in an effective dissociation rate that is approximately sevenfold slower than the microscopic subunit unbinding rate. The quaternary structure, which has been conserved through evolution, is expected to increase the transporters' capture efficiency by increasing the probability that following unbinding, a ligand will rebind as opposed to being lost to diffusion.

Leary, Greg P.; Holley, David C.; Stone, Emily F.; Lyda, Brent R.; Kalachev, Leonid V.; Kavanaugh, Michael P.

2011-01-01

14

Diffuse interface model of diffusion-limited crystal growth  

Microsoft Academic Search

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

Joseph B. Collins; Herbert Levine

1985-01-01

15

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

16

Simulation of cavity growth in ceramic materials during superplastic deformation  

SciTech Connect

It is well established that superplastic deformation is accompanied by cavitation in a wide range of materials. The growth, coalescence and interlinkage of cavities leads to premature failure, which in tensile specimens may involve a pseudo-brittle fracture. While cavitation in metallic systems has received much attention, there have been few studies of cavitation in ceramic materials. In the present work, artificial pores have been introduced into Y-TZP (yttria stabilized tetragonal zirconia polycrystals) and doped alumina specimens to simulate cavities and changes in the sizes and shapes of these pores have been studied during either tensile or compressive superplastic flow. A comparison has been made of measured cavity growth/shrinkage rates with those of predictive models.

Wang, Z.C.; Ridley, N.; Davies, T.J. [Univ. of Manchester and UMIST (United Kingdom). Materials Science Centre

1997-03-01

17

Study of small-scale cavity growth mechanisms for UCG  

Microsoft Academic Search

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

D. L. Yeary; J. B. Riggs

1987-01-01

18

Modelling Early Tumor Growth with Diffusion Equation  

Microsoft Academic Search

Abstract This essay is aimed at forming a lecture series on the modelling of early tumor growth using diffusion equations. We present basic models for tumor growth and discuss the linear stability of their steady states. The models discussed predict the size of the proliferating layer, the size of the tumor, and the effects of the immune system response, on

Asha Saidi Kalula; Jacek Banasiak

19

Reactive diffusion produced niobium nitride films for superconducting cavity applications  

Microsoft Academic Search

In view of their potential interest for the construction of radiofrequency (RF) superconducting accelerating cavities, films of NbN have been produced by annealing Nb samples in a nitrogen atmosphere. These films have been characterized by critical temperature measurements performed with the magnetic permeation method, by metallographic examination and by X-ray diffraction. They exhibit critical temperatures up to 16.6 K, and

C. Benvenuti; P. Chiggiato; L. Parrini; R. Russo

1993-01-01

20

Particle longitudinal diffusion produced by a High Frequency Cavity  

SciTech Connect

A High Frequency Cavity (HFC) can be a powerful tool for the reduction of particle losses during the energy passage through the ..gamma..-transition in proton synchrotrons, via bunch dilution. In this paper we consider some aspects of bunch dilution. With an appropriately chosen frequency of phase modulation, the HFC can produce parametric resonance for particles near the bunch center. As a result, the process of dilution can be accelerated.

Kats, J.M.

1987-01-01

21

Reactive diffusion produced niobium nitride films for superconducting cavity applications  

NASA Astrophysics Data System (ADS)

In view of their potential interest for the construction of radiofrequency (RF) superconducting accelerating cavities, films of NbN have been produced by annealing Nb samples in a nitrogen atmosphere. These films have been characterized by critical temperature measurements performed with the magnetic permeation method, by metallographic examination and by X-ray diffraction. They exhibit critical temperatures up to 16.6 K, and transition widths of about 0.4 K. The influence of nitriding conditions (temperature, nitrogen pressure and time) on the superconducting properties has been investigated, in order to obtain the optimal nitriding parameters.

Benvenuti, C.; Chiggiato, P.; Parrini, L.; Russo, R.

1993-11-01

22

Study of small-scale cavity growth mechanisms for UCG  

SciTech Connect

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

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

1987-01-01

23

Creep crack growth by diffusive cavitation  

Microsoft Academic Search

The model by Raj and Baik in which a macroscopic crack advances by the growth and coalescence of microvoids is reanalyzed and extended to include the effect of surface diffusion and small scale power-law creep. Using a boundary integral method, the analysis is valid when the stress intensity factor is the load parameter which determines the crack tip stress field.

Jin

2008-01-01

24

A mass transfer study of the diffusion controlled dissolution of cubical cavities under natural convection conditions  

SciTech Connect

The role of mass transfer in the rate of diffusion controlled dissolution of cubical cavities was studied using an electrochemical technique involving the measurement of the limiting current of the anodic dissolution of copper cavities in H{sub 3}PO{sub 4}. Cavity side length and H{sub 3}PO{sub 4} concentration were varied to provide (Sc.Gr) range of 8.7 {times} 10{sup 9}--3.9 {times} 10{sup 11}. Under these conditions the mass transfer coefficients of cavity dissolution were correlated to other parameters by the equation Sh = 2.742 (Sc.Gr){sup 0.22}. The equation can be used in practice to predict the rate of diffusion controlled processes which might take place inside the cavity such as electropolishing and electrochemical machining. By comparing the experimental rate of mass transfer with the value calculated by adding the rates of mass transfer at different surfaces of the cavity a remarkable agreement was found denoting little convective interaction under the experimental conditions studied.

Nirdosh, I.; Sedahmed, G.H. [Lakehead Univ., Thunder Bay, Ontario (Canada)

1996-09-01

25

Onset of double-diffusive convection in a rectangular porous cavity subject to mixed boundary conditions  

Microsoft Academic Search

The onset of double-diffusive convection in a horizontal porous cavity is studied numerically using linear stability analysis. In the formulation of the problem, use is made of the Darcy model with the Boussinesq approximation. Mixed boundary conditions for heat and solute are specified on the horizontal walls of the enclosure while the two vertical ones are impermeable and adiabatic. The

A. Mahidjiba; M. Mamou; P. Vasseur

2000-01-01

26

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

Microsoft Academic Search

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

A. A. Rubinstein

1982-01-01

27

Role of cavity growth mechanisms in determining creep-rupture under multiaxial stresses  

Microsoft Academic Search

The effect of stress state on the time and strain to failure has been considered in terms of currently accepted models of cavity growth. It is shown that the increasing contributions of compressive stress cause changes in cavity growth mechanisms which lead to increases in ductility. A tensile component of stress is necessary to provide the driving force for cavity

R. Hales

1994-01-01

28

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

PubMed

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. PMID:22734771

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

2012-06-01

29

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

30

Double-diffusive natural convection in a fluid saturated porous cavity with a freely convecting wall  

SciTech Connect

Double-diffusive natural convection in fluid saturated porous medium has been investigated using a generalized porous medium model. One of the vertical walls of the porous cavity considered is subjected to convective heat and mass transfer conditions. The results show that the flow, heat and mass transfer become sensitive to applied mass transfer coefficient in both the Darcy and non-Darcy flow regimes. It is also observed that the Sherwood number approaches a constant value as the solutal Biot number increases. Double-diffusive natural convection in fluid saturated porous medium is encountered in applications such as food processing, contaminant transport in ground water, and others.

Nithiarasu, P. [University College of Swansea (United Kingdom). Inst. for Numerical Methods in Engineering; Sundararajan, T. [Indian Inst. of Tech., Madras (India). Dept. of Mechanical Engineering; Seetharamu, K.N. [Universiti Sains Malaysia, Tronoh (Malaysia). School of Mechanical Engineering

1997-12-01

31

Effect of thermal and structural properties on the growth of an underground coal-gasification cavity  

Microsoft Academic Search

In field and laboratory studies of underground coal gasification, the growth of the cavity about the initial link has varied from the approximately circular cross section observed in the Hanna Basin coals, to cavities with 2:1 ratios of vertical to horizontal growth as has been observed in the Powder River Basin coals. A model based on the thermal and structural

1983-01-01

32

On the anomalous fast ion energy diffusion in toroidal plasmas due to cavity modes  

NASA Astrophysics Data System (ADS)

An enormous wave-particle diffusion coefficient along paths suitable for alpha channeling had been deduced in mode-converted ion Bernstein wave experiments on the 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 Alfvén 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 frequency 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 conjecture 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.

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

2010-05-01

33

Primary Diffuse Large B-Cell Lymphoma of the Oral Cavity: Germinal Center Classification  

Microsoft Academic Search

Primary lymphomas of the oral cavity are rare and the most frequent type is diffuse large B-cell lymphoma (DLBCL). Recently,\\u000a several reports have highlighted the value of classifying DLBCL into prognostically important subgroups, namely germinal center\\u000a B-cell like (GCB) and non-germinal center B-cell like (non-GCB) lymphomas based on gene expression profiles and by immunohistochemical\\u000a expression of CD10, BCL6 and MUM-1.

Indraneel BhattacharyyaHardeep; Hardeep K. Chehal; Donald M. Cohen; Samer Z. Al-Quran

2010-01-01

34

Nucleation and early-stage growth of creep cavities in hot-pressed silicon carbide  

SciTech Connect

Fine-grained silicon carbide with a continuous second phase grain boundary film was crept under compressive loading at 1600/sup 0/ C. The resultant nucleation and growth of creep cavities was characterized using small angle neutron scattering. It was found that nucleation occurred within approximately the first 5% of the lifetime, so that the modeling of failure essentially involves the treatment of cavity growth and ultimate coalescence. The results suggested that cavity nucleation and growth occurred entirely within the viscous grain boundary film. However, the cavities do not grow, crack-like across the grain boundary facets, but rather nucleate as lens shaped pores which gradually transform as the film thickens, to very slowly growing spheroidal cavities. The results are shown to contrast with similar experiments on an alumina with clean grain boundaries, in which pore nucleation, rather than pore growth, controlled creep life.

Paye, R.A.; Lankford, J.; Spooner, S.

1984-09-01

35

Effect of Thermal and Structural Properties on the Growth of an Underground Coal-Gasification Cavity.  

National Technical Information Service (NTIS)

In field and laboratory studies of underground coal gasification, the growth of the cavity about the initial link has varied from the approximately circular cross section observed in the Hanna Basin coals, to cavities with 2:1 ratios of vertical to horizo...

R. E. Glass

1983-01-01

36

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

Microsoft Academic Search

Numerous UCG field tests have been performed during the past ten years. Due to the high cost of obtaining sweep efficiency data, limited field data on cavity shape in the coal seam have been obtained. Because of the importance of resource recovery on the economic viability of the UCG process, laboratory studies on cavity growth have been undertaken for Texas

1984-01-01

37

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

Microsoft Academic Search

A model describing cavity growth and gas production during underground coal gasification (UCG) has been developed. It is applicable to UCG of shrinking coals in which oxidant injection is maintained at a fixed point low in the coal seam. It is based on a few fundamental assumptions; namely that the cavity is axisymmetric about the injection point, all resistance to

J. A. Britten; C. B. Thorsness

1989-01-01

38

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

Microsoft Academic Search

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

Ning Wang; Donald B. Fisher

39

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

SciTech Connect

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

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

2010-06-15

40

Technological diffusion, the diffusion of skill and the growth of outsourcing in US manufacturing  

Microsoft Academic Search

What drives the observed rapid growth of outsourcing in US manufacturing? This article approaches this question by asking whether technological diffusion driven by R&D spillovers is in part responsible for the growth of atypical work arrangements in the USA. Relying on data of technological diffusion since the early 1970s, this study provides some evidence that technological factors may have contributed

Elisabetta Magnani

2006-01-01

41

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

42

Resource Recovery and Cavity Growth During the Rocky Mountain 1 Field Test.  

National Technical Information Service (NTIS)

Resource recovery and cavity growth remain important issues affecting performance, scale-up and overall process efficiency for underground coal gasification (UCG). Results from the recently completed dual-module Rocky Mountain I (RM I) UCG experiment give...

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

1988-01-01

43

Freezing coherent field growth in a cavity by the quantum zeno effect.  

PubMed

We have frozen the coherent evolution of a field in a cavity by repeated measurements of its photon number. We use circular Rydberg atoms dispersively coupled to the cavity mode for an absorption-free photon counting. These measurements inhibit the growth of a field injected in the cavity by a classical source. This manifestation of the quantum Zeno effect illustrates the backaction of the photon number determination onto the field phase. The residual growth of the field can be seen as a random walk of its amplitude in the two-dimensional phase space. This experiment sheds light onto the measurement process and opens perspectives for active quantum feedback. PMID:18999798

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

2008-10-28

44

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

45

Effect of Cavity Growth Rate and Cr on High Temperature Crack Growth in P92 and P122 Steels  

NASA Astrophysics Data System (ADS)

In this work, the velocity of crack propagation at high temperature was investigated with da/dt-Ct relationship using recently developed P92 and P122 steels. Role of cavity in crack growth rate and load line displacement rate was studied by measuring the cavity size and density, which will influence crack nucleation and growth. Since temperature and stress changes are particularly important at high temperature, crack growth behavior was evaluated under various temperature and Ki(initial stress intensity factor). Effect of Cr content was evaluated by measuring crack growth activation energy in thesis.

Lim, Byeongsoo; Jeong, Chanseo

46

Flow transitions in three-dimensional double-diffusive fingering convection in a porous cavity  

NASA Astrophysics Data System (ADS)

In the present study the existence of multiple three-dimensional double-diffusive flow patterns in a horizontal rectangular porous cavity of a square cross-section, having horizontal aspect ratios Ax = Ay = 2 is investigated numerically. Opposing vertical gradients of temperature and concentration are applied between the two horizontal walls of the cavity, where the solute gradient is destabilizing against a stabilizing temperature gradient. All vertical walls are considered to be impermeable and adiabatic. The Brinkman and Forchheimer terms are included in the momentum equations where the convective terms are retained. The effect of the buoyancy ratio, N, thermal Rayleigh number, RaT and Lewis number, Le, on the formation of multiple flow patterns is investigated over a wide range of parameters. Altogether 36 symmetric flow structures have been identified when each of the parameters N, RaT, and Le is varied independently, keeping the others as constants. The results of the calculations are presented in terms of the average Sherwood number curves consisting of different solution branches, where transitions between the branches are indicated. The flow patterns are classified according to their symmetry properties and the type of symmetries broken or preserved are identified during the bifurcation processes.

Sezai, I.

2002-08-01

47

Multinational Enterprises, Technology Diffusion, and Host Country Productivity Growth  

Microsoft Academic Search

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

Bin Xu

1999-01-01

48

Multinational enterprises, technology diffusion, and host country productivity growth  

Microsoft Academic Search

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

Bin Xu

2000-01-01

49

ICT Diffusion and Economic Growth in New Zealand  

Microsoft Academic Search

Two different theoretical treatments of technology diffusion in an economy are examined. The traditional model based on the aggregate production function approach first introduced by Solow (1957) assumes technology is unstructured and arrives as a continuous exogenous flow. This model predicts that the diffusion of new technologies will be contemporaneously correlated with growth in economic performance indicators. An alternative view

Les T. Oxley; Kenneth I. Carlaw

2004-01-01

50

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

51

Formation of gaseous cavity defect during growth of Nd:YAG single crystals  

NASA Astrophysics Data System (ADS)

In this research, formation of gaseous cavity defect in 1 at%Nd:YAG single crystal grown by the Czochralski technique has been studied. Growth atmosphere pressure and crystal rotation rate were optimized in order to prevent the defect formation. The microstructure of the defect was characterized using scanning electron microscopy (SEM) and wavelength dispersive spectroscopy (WDS) analyses. The stresses induced by the gaseous cavity were also investigated by parallel plane polariscope. The results show that the growth atmosphere pressure has a more significant influence on defect formation compared to the crystal rotation rate. In addition, decreasing the growth atmosphere pressure leads to growth of the crystals with no gaseous cavity defect. The results also show that Nd concentration varies around the defect making these areas useless for solid-state lasers application.

Yadegari, M.; Asadian, M.; Saeedi, H.; Khodaei, Y.; Mirzaei, N.

2013-03-01

52

A mechanistic model for axisymmetric cavity growth during underground coal gasification  

SciTech Connect

A model for cavity growth and gas production during UCG, based on the assumption of cylindrical cavity symmetry and applicable for gasification of shrinking coals when injection low in the coal seam can be maintained, has been developed. The model is highly idealized, but treats includes all important factors impacting cavity growth such as water influx, porous media flow, heterogeneous and homogeneous chemical reactions, radiative and convective heat transfer, and rock mechanics. Model predictions have been shown to agree very well with available field data, and while detailed produced gas compositions cannot be estimated, it is felt quite adequate to describe in a semiquantitative fashion cavity evolution, energy recovery, aquifer response, and effects of process parameter changes, and therefore is a useful tool for UCG site characterization and module optimization.

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

1988-01-01

53

Super-diffusive Bacterial Growth in Highly Advective Random Environments  

NASA Astrophysics Data System (ADS)

Bacterial growth may be modeled using a reaction-diffusion equation with Fisher-like growth terms. This includes a growth term proportional to the bacterial concentration in addition to a non-linear term to prevent unbounded growth. An additional random growth term may be added to simulate the spatial fluctuation of nutrients in the environment. Recent calculations for such a model with only linear terms has predicted that in the highly advective regime bacterial growth is super-diffusive in directions orthogonal to the convection velocity(D. R. Nelson and N. M. Shnerb, Phys. Rev. E 58), 1383 (1998).. We test these predictions via numerical simulations of the corresponding growth equation in two dimensions. The full non-linear equation is also numerically simulated and compared with the linear case.

Carpenter, John H.; Dahmen, Karin A.; Nelson, David R.

2003-03-01

54

Statistical Theory of Diffusion-Limited Growth in Two Dimensions  

Microsoft Academic Search

A formalism of irreversible aggregation processes is presented in terms of statistical mechanics. Thermodynamical variables that include the degeneracy of the histories, which we call ``history entropy,'' are introduced by taking into account all possible growth histories. By considering the thermodynamic properties of the growth history and harmonic measure, we find the condition of the most probable history for diffusion-limited

Yoshinori Hayakawa; Shinichi Sato

1997-01-01

55

Diffusive energy growth in classical and quantum driven oscillators  

Microsoft Academic Search

We study the long-time stability of oscillators driven by time-dependent forces originating from dynamical systems with varying degrees of randomness. The asymptotic energy growth is related to ergodic properties of the dynamical system: when the autocorrelation of the force decays sufficiently fast one typically obtains linear diffusive growth of the energy. For a system with good mixing properties we obtain

L. Bunimovich; H. R. Jauslin; J. L. Lebowitz; A. Pellegrinotti; P. Nielaba

1991-01-01

56

Diffusion-limited polymerization and surface growth  

NASA Astrophysics Data System (ADS)

Simulations have been carried out to investigate the structures generated by a nonequilibrium Laplacian-random-walk model for the growth of polymer chains which was recently developed by Lyklema et al. Instead of solving the Laplace equation numerically to obtain the growth probabilities at the active end of the growing polymer chain, random walkers are used to simulate a random growth process controlled by a harmonic field. The results from two-dimensional simulations are in good agreement with those of Lyklema et al., Bradley and Kung, and Debierre and Turban. The growth of single chains on square lattices or cubic lattices leads to structures which can be described in terms of a single geometric scaling exponent (fractal dimensionality) for both absorbing and reflecting boundary conditions at the inactive (nongrowing chain sites). The main objective of this work was the investigation of models in which many chains grow from a line or plane of active sites to represent growth from a surface. For these models at least two effective exponents are needed to describe the structure of the system. The distribution of chain length can be described in terms of a power law (with an exponential cutoff) and the total density profile can also be described by a power law. The two-point density-density correlation function Ch(r) for those sites located at a distance h from the original surface of active sites can be described in terms of the scaling form Ch(r)~h-?f(r/h?), where f(x) is a scaling function. These results indicate that the structure of the surface deposits grown by the models should be described in terms of a non-self-similar (possibly self-affine) fractal geometry.

Meakin, Paul

1988-04-01

57

Longitudinal diffusion as inflicted by arbitrary band-width random-modulated currents in feeders of detuned cavities  

Microsoft Academic Search

The diffusion coefficient for a bunched p-beam in a synchrotron is presented with two technically imposed items included into the scheme. (1) The role of basic external noise is attributed to random envelopes i(a,?)(t) carried by two modulated time-quadrature RF-currents. These represent amplitude, (a) or (small) phase, (?) noises of a forward current in cavity feeders. (Commonly, the (a, ?)-noise

Sergei Ivanov

1993-01-01

58

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

Microsoft Academic Search

Resource recovery and cavity growth remain important issues affecting performance, scale-up and overall process efficiency for underground coal gasification (UCG). Results from the recently completed dual-module Rocky Mountain I (RM I) UCG experiment give us firsthand information concerning these important parameters. During the RM I test, two gasifiers, the Controlled Retracting Injection Point (CRIP) and the Extended Linked Well (ELW)

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

1988-01-01

59

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

60

Cavity growth in ductile particles bridging a brittle matrix crack  

Microsoft Academic Search

The addition of a dispersed ductile phase in a brittle ceramic can result in an increased fracture toughness, mainly due to plastic dissipation during crack bridging. The large elastic-plastic deformations of a ductile particle intercepted by a brittle matrix crack are here analysed numerically with main focus on the effect of the growth of a single void in the particle

Viggo Tvergaard

1995-01-01

61

Non-Darcy double-diffusive natural convection in axisymmetric fluid saturated porous cavities  

NASA Astrophysics Data System (ADS)

Double-diffusive natural convection in a fluid saturated porous medium has been investigated using the finite element method. A generalised porous medium model is used to study both Darcy and non-Darcy flow regimes in an axisymmetric cavity. Results indicate that the Darcy number should be a separate parameter to understand flow characteristics in non-Darcy regime. The influence of porosity on heat and mass transfer is significant and the transport rates may differ by 25% or more, at higher Darcy and Rayleigh numbers. When compared with the Darcy and other specialised models of Brinkman and Forchheimer, the present generalised model predicts the least heat and mass transfer rates. It is also observed that an increase in radius ratio leads to higher Nusselt and Sherwood numbers along the inner wall. Zusammenfassung Mit Hilfe der Finitelement-Methode wurde die Doppeldiffusion bei natürlicher Konvektion in einem fluidgetränktem porösen Medium untersucht, wobei ein verallgemeinertes Modell für poröse Medien Verwendung fand, das sich sowohl für Darcysches, wie für nicht-Darcysches Fluidverhalten in einem achsialsymmetrischen Ringraum eignet. Aus den Ergebnissen geht hervor, daß die Darcy-Zahl als zusätzlicher Parameter eingeführt werden muß, um das Strömungsverhalten im nicht-Darcyschen Regime verstehen zu können. Die Porosität hat großen Einfluß auf den Wärme- und Stoffaustausch, so daß bei höheren Darcy- und Rayleigh-Zahlen diesbezüglich Unterschiede bis über 25% auftreten können. Im Vergleich mit den speziellen Modellen nach Darcy, Brinkman und Forchheimer liefert das hier untersuchte verallgemeinerte Modell die geringsten Wärme- und Stoffflüsse. Es zeigt sich ferner, daß die Vergrößerung des Radienverhältnisses höhere Nusselt- und Sherwood- Zahlen entlang der Innenwand zur Folge hat.

Nithiarasu, P.; Seetharamu, K. N.; Sundararajan, T.

62

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

SciTech Connect

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

Park, K.Y.

1984-01-01

63

Biocomputing: numerical simulation of glioblastoma growth using diffusion tensor imaging  

NASA Astrophysics Data System (ADS)

Glioblastoma multiforma (GBM) is one of the most aggressive tumors of the central nervous system. It can be represented by two components: a proliferative component with a mass effect on brain structures and an invasive component. GBM has a distinct pattern of spread showing a preferential growth in the white fiber direction for the invasive component. By using the architecture of white matter fibers, we propose a new model to simulate the growth of GBM. This architecture is estimated by diffusion tensor imaging in order to determine the preferred direction for the diffusion component. It is then coupled with a mechanical component. To set up our growth model, we make a brain atlas including brain structures with a distinct response to tumor aggressiveness, white fiber diffusion tensor information and elasticity. In this atlas, we introduce a virtual GBM with a mechanical component coupled with a diffusion component. These two components are complementary, and can be tuned independently. Then, we tune the parameter set of our model with an MRI patient. We have compared simulated growth (initialized with the MRI patient) with observed growth six months later. The average and the odd ratio of image difference between observed and simulated images are computed. Displacements of reference points are compared to those simulated by the model. The results of our simulation have shown a good correlation with tumor growth, as observed on an MRI patient. Different tumor aggressiveness can also be simulated by tuning additional parameters. This work has demonstrated that modeling the complex behavior of brain tumors is feasible and will account for further validation of this new conceptual approach.

Bondiau, Pierre-Yves; Clatz, Olivier; Sermesant, Maxime; Marcy, Pierre-Yves; Delingette, Herve; Frenay, Marc; Ayache, Nicholas

2008-02-01

64

Effect of thermal and structural properties on the growth of an underground coal-gasification cavity  

SciTech Connect

In field and laboratory studies of underground coal gasification, the growth of the cavity about the initial link has varied from the approximately circular cross section observed in the Hanna Basin coals, to cavities with 2:1 ratios of vertical to horizontal growth as has been observed in the Powder River Basin coals. A model based on the thermal and structural behavior of coal has indicated that these shapes are dependent on the site specific properties of the coal. In this study, the properties of coal samples taken from the Big Seam near Centralia, Washington, are used in the model to examine the cavity growth in that seam. Due to the high variability of these properties, sensitivity studies are included to determine a range of probable shapes. The results obtained from the model are then compared with field data. The result of the study is a prediction that the vertical-to-horizontal growth ratios will vary from 1:1 to 1.4:1 in underground tests in the Big Seam. 3 tables.

Glass, R.E.

1983-01-01

65

Cavity growth and filament formation of superplastically deformed Al 7475 Alloy  

Microsoft Academic Search

Superplastic deformation induced cavitation of aluminium alloys usually results in the material performance degradation. In this study the cavitation behaviour of Al 7475 was characterised, using samples deformed at temperature ranging from 480 to 530°C and at an initial strain rate of 10?3s?1. The results showed that the cavity growth rate parameter increased slightly as the test temperature increased. The

C. L Chen; M. J Tan

2001-01-01

66

Selective cavity-enhanced trace gas detection via diffusion time-of-fight  

NASA Astrophysics Data System (ADS)

A novel approach to optical detection of airborne explosive vapor using a combination of cavity enhanced ab- sorption spectroscopy (CEAS) and diusion time of ight (DiTOF) is reported. The direct optical detection of explosive vapors by absorption presents a number of unique challenges due to low vapor pressures of explosive compounds, a lack of resolved spectral features, and the presence of interfering species with overlapping absorp- tion spectra. By recording the changing optical absorption as sampled atmosphere diuses into an explosive-free buer gas, the concentration of explosive molecules may be determined using a Bayesian statistical signal process- ing technique. This technique avoids the need for laser wavelength scans while simultaneously providing robust background rejection. The use of xed laser wavelengths allows for the use of cavity-locked cavity ring-down or cavity-locked direct cavity transmission absorption measurements with high data acquisition rates and signi- cantly reduces the complexity of the laser system by eliminating the need for precision wavelength monitoring. This allows for the development of compact, eld deployable sensors based on this technique. Experimental demonstration of the simultaneous detection of multiple species of hydrocarbon tracer molecules at 4295 cm-1 will be reported. The results of the current work will be applied to the detection of TNT vapor to show a projected sensitivity of 2 pptv in a diesel exhaust background.

Miller, Anthony; Richman, Bruce; Viteri, C. Ricardo; McKeever, Jason

2012-05-01

67

Diffusion-controlled growth of albite and pyroxene reaction rims  

NASA Astrophysics Data System (ADS)

The growth rates of albite and pyroxene (enstatite + diopside + spinel) reaction rims were measured at 1000°C and 700 MPa and found to be parabolic indicating diffusion-controlled growth. The parabolic rate constants for the pyroxene (+ spinel) rims in samples with 0.5 wt% H2O added or initially vacuum dried at 25°C and 250°C are 1.68 +/- 0.09, 0.54 +/- 0.05 and 0.25 +/- 0.06 ?m2/h, respectively. The values for albite rim growth in samples initially dried at 60°C and with 0.1 wt% H2O added are 0.25 +/- 0.04 and 0.33 +/- 0.03 ?m2/h, respectively. The latter values were used to derive the product of the grain boundary diffusion coefficient D'A, where A = SiO2, NaAlO2, or NaAlSi-1, and the grain boundary thickness ? in albite. The calculated D'SIO2? in the albite aggregate for the situations of two different water contents are about 9.9 × 10-23 and 1.4 × 10-22 m3 s-1, respectively. Both the rate constants and the calculated D'A? demonstrate that the effect of water content on the grain boundary diffusion rate in monomineralic albite and polymineralic pyroxene (+ spinel) aggregates is small, consistent with recent studies of monomineralic enstatite and forsterite rims.

Liu, M.; Peterson, J. C.; Yund, Richard A.

68

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

SciTech Connect

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

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

1989-01-01

69

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

SciTech Connect

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

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

1987-07-15

70

Nanomechanical characterization of cavity growth and rupture in hydrogen-implanted single-crystal BaTiO{sub 3}  

SciTech Connect

A thermodynamic model of cavity nucleation and growth in ion-implanted single-crystal BaTiO{sub 3} layer is proposed, and cavity formation is related to the measured mechanical properties to better understand hydrogen implantation-induced layer transfer processes for ferroelectric thin films. The critical radius for cavity nucleation was determined experimentally from blistering experiments performed under isochronal anneal conditions and was calculated using continuum mechanical models for deformation and fracture, together with thermodynamic models. Based on thermodynamic modeling, we suggest that cavities grow toward the cracking criteria at a critical blister size whereupon gas is emitted from ruptured cavities. The main driving force for layer splitting is the reduction of the overall elastic energy stored in the implanted region during the cavity nucleation and growth as the gaseous H{sub 2} entrapped within the cavities is released. Nanoindentation measurements reveal locally the mechanical property changes within the vicinity of a single cavity. Using the measured mechanical properties at the single-cavity level, we developed three-dimensional strain and stress profiles using finite element method.

Park, Young-Bae; Nardi, Patrick; Li, Xiaodong; Atwater, Harry A. [Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125 (United States); Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, South Carolina 29208 (United States); Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125 (United States)

2005-04-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

72

Single crystalline Si substrate growth by lateral diffusion epitaxy  

NASA Astrophysics Data System (ADS)

A novel crystal growth method named lateral diffusion epitaxy (LDE) as well as the necessary growth apparatus are described in detail. Single crystalline Si strips are grown on (111) Si substrates by LDE. The thickness of the LDE Si strips is around 100?m, and the aspect ratio of width to thickness is around 2 which is an improvement compared with Si strips grown by conventional liquid phase epitaxy (LPE). The LDE Si strip can be peeled off from the substrate for further device processing since the 100?m thickness provides reasonable mechanical strength. Due to the low cost of LDE technology it is potentially a good candidate for PV application if the LDE can achieve continuous growth and therefore grow Si strips in sizes for practical application.

Li, Bo; Yu, Hao Ling; Shen, Huaxiang; Kitai, Adrian

2013-03-01

73

Production of niobium-titanium nitride coatings by reactive diffusion for superconducting cavity applications  

Microsoft Academic Search

In view of their potential interest for the construction of radiofrequency superconducting cavities for particle accelerators, surface coatings of (Nb1?xTix)N have been produced by heating Nb1?xTix sheets in a nitrogen atmosphere. Samples of two different compositions, namely Nb0.37Ti0.63 and Nb0.55Ti0.45, have been treated to optimise the process parameters. The results have been evaluated by critical temperature measurements, metallographic examinations and

C. Benvenuti; P. Chiggiato; L. Parrini; R. Russo

1997-01-01

74

Production of niobium-titanium nitride coatings by reactive diffusion for superconducting cavity applications  

NASA Astrophysics Data System (ADS)

In view of their potential interest for the construction of radiofrequency superconducting cavities for particle accelerators, surface coatings of (Nb1-xTix)N have been produced by heating Nb1-xTix sheets in a nitrogen atmosphere. Samples of two different compositions, namely Nb0.37Ti0.63 and Nb0.55Ti0.45, have been treated to optimise the process parameters. The results have been evaluated by critical temperature measurements, metallographic examinations and X-ray diffraction. In the best cases a homogeneous ternary phase of sufficient thickness (up to 2 ?m), providing a critical temperature up to 17.2 K and a transition width of 0.2 K, may be obtained.

Benvenuti, C.; Chiggiato, P.; Russo, R.; Parrini, L.

1997-04-01

75

Nonequilibrium Cluster Diffusion During Growth and Evaporation in Two Dimensions  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

76

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

77

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

SciTech Connect

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

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

1988-08-01

78

Growth of Mycobacterium lepraemurium in Cell-Impermeable Diffusion Chambers  

PubMed Central

Successful growth of Mycobacterium lepraemurium has been achieved by use of a specialized diffusion chamber technique. The cell-impermeable porous chambers were maintained in animals for periods up to 50 days with and without macrophages and LM cells. A generation time of 6 to 8 days was found for the acid-fast bacilli in chambers containing macrophages when maintained in the mouse. Also, cell-free chambers maintained in the mouse gave a generation time of 11 days for M. lepraemurium. There was no doubt that chambers maintained in a susceptible host provided greater yields of bacilli than chambers maintained in a nonsusceptible host such as the guinea pig. In fact, better yields were obtained when the chambers were maintained in monolayer petri plate cultures of mouse peritoneal macrophages than when held in the guinea pig. The most pertinent observation was that living cells are not essential for growth of M. lepraemurium, and the results suggest that multiplication can occur in a cell-free environment within a susceptible host. These studies give evidence that the use of porous chambers has promising possibilities for further investigations on the cultivation of other fastidious mycobacteria.

Rightsel, Wilton A.; Wiygul, William C.

1971-01-01

79

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

80

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

81

Growth and characterization of novel multilayer heterostructures for the monolithic integration of resonant-cavity photodiodes and heterojunction bipolar transistors  

SciTech Connect

We describe the layer structures, crystal-growth conditions, and characteristics of novel multilayers in the InGaAlAs/InGaAs/InAlAs materials system for the monolithic integration of heterojunction bipolar transistors (HBTs) and resonant-cavity photodiodes. The photodiodes are formed of the base and collector regions of the HBT layer. The use of a resonant cavity improves the quantum efficiency for an absorbing layer of given thickness. The HBTs had high current gains and well-behaved Gummel plots. The absorption and photocurrent characteristics of the resonant photodiodes show a {approximately} 100% enhancement at resonance. 11 refs., 3 figs.

Dodabalapur, A.; Chang, T.Y.; Chandrasekhar, S. [AT& T Bell Lab., Holmdel, NJ (United States)

1993-05-01

82

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

83

Advection-diffusion model for the stagnation of normal grain growth in thin films  

Microsoft Academic Search

This paper presents an advection-diffusion model to describe the stagnation of normal grain growth in thin films. The underlying advection-diffusion model describes grain growth in a two-dimensional topological-class\\/size space. Grain boundary grooving and the correlation between neighbouring grains are introduced into the model to represent stagnation. Grain boundary grooving causes the stagnation of grain growth, and the correlation between neighbouring

C. Lou; M. A. Player

2002-01-01

84

Double-diffusive natural convection in inclined porous cavities with various aspect ratios and temperature-dependent heat source or sink  

NASA Astrophysics Data System (ADS)

Laminar double-diffusive natural convective flow of a binary fluid mixture in inclined square and rectangular cavities filled with a uniform porous medium in the presence of temperature-difference dependent heat generation (source) or absorption (sink) is considered. Transverse gradients of heat and mass are applied on two opposing walls of the cavity while the other two walls are kept adiabatic and impermeable to mass transfer. The problem is put in terms of the stream function-vorticity formulation. A numerical solution based on the finite-difference methodology is obtained for relatively high Lewis numbers. Representative results illustrating the effects of the inclination angle of the cavity, buoyancy ratio, Darcy number, heat generation or absorption coefficient and the cavity aspect ratio on the contour maps of the streamline, temperature, and concentration as well as the profiles of velocity, temperature and concentration at mid-section of the cavity are reported. In addition, numerical results for the average Nusselt and Sherwood numbers are presented for various parametric conditions and discussed.

Chamkha, Ali J.; Al-Mudhaf, Ali

2008-04-01

85

Late growth stages and post-growth diffusion in organic epitaxy: PTCDA on Ag(1 1 1)  

Microsoft Academic Search

The late growth stages and the post-growth diffusion of crystalline organic thin films have been investigated for 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111), a model system in organic epitaxy. In situ X-ray measurements at the anti-Bragg point during the growth show intensity oscillations followed by a time-independent intensity which is independent of the growth temperature. At T?350K, the intensity increases after

B. Krause; A. C. Dürr; F. Schreiber; H. Dosch; O. H. Seeck

2004-01-01

86

Morphological stabilization, destabilization, and open-end closure during carbon nanotube growth mediated by surface diffusion  

NASA Astrophysics Data System (ADS)

In this paper, the growth stability of open-ended carbon nanotubes mediated by surface diffusion on the lateral surface of the nanotube is considered in detail. Nanotube growth and destabilization is viewed as a competition of two processes at the open growth edge: (i) hexagon formation sustaining the continuous growth of the regular hexagonal network, and (ii) thermally activated pentagon formation, which causes inward bending of the nanotube wall resulting in end closure, i.e., growth termination. The edge of the open-ended nanotube, if it is fed by a sufficiently large surface diffusion flux, may remain stable even without extrinsic stabilizing effects. The closure of the open end of the growing nanotube is shown to happen whenever a change in the growth conditions (temperature, carbon vapor pressure, or surface area from which the open end is fed) decreases the surface diffusion flux, and the characteristic time for new atom arrival on the edge becomes larger than the characteristic time for pentagon defect formation. These kinetic effects are also shown to define the transition from single wall to multiwall nanotube growth. Additionally, the effect of surface diffusion feeding nanotube growth from behind the growth interface is shown to stabilize open edge morphology, effectively smoothing the growth perturbations which may be caused by diffusion-limited aggregation at the edge.

Louchev, Oleg A.; Sato, Yoichiro; Kanda, Hisao

2002-07-01

87

Thermodynamic modelling of diffusion-controlled garnet growth  

Microsoft Academic Search

Numerical thermodynamic modelling of mineral composition and modes for specified pressure-temperature paths reveals the strong influence of fractional garnet crystallisation, as well as water fractionation, on garnet growth histories in high pressure rocks. Disequilibrium element incorporation in garnet due to the development of chemical inhomogeneities around porphyroblasts leads to pronounced episodic growth and may even cause growth interruptions. Discontinuous growth,

Matthias Konrad-Schmolke; Mark R. Handy; Jochen Babist; Patrick J. O’Brien

2005-01-01

88

Numerical Study on Double Diffusive Mixed Convection with a Soret Effect in a Two-Sided Lid-Driven Cavity  

Microsoft Academic Search

In the present study, a numerical analysis is performed to understand the mixed convection flow, and heat and mass transfer with Soret effect in a two-sided lid-driven square cavity. The horizontal walls of the cavity are adiabatic and impermeable, while vertical walls are kept at constant but different temperatures and concentrations. The vertical walls move in a constant velocity. According

M. Bhuvaneswari; S. Sivasankaran; Y. J. Kim

2011-01-01

89

Cellular Automata Diffusion-Kinetic Model of Dendritic Growth  

Microsoft Academic Search

\\u000a A mathematical crystallization model in the meso scale (the intermediate dimension scale between interatomic distance in solids\\u000a and grain size in metals and alloys) is presented with the use of a kinetic-diffusion cellular automaton model. The proposed\\u000a model differs from other models by including the diffusion of elements and heat conductivity effects on the physical phenomena\\u000a at the solid-liquid interface.

Andriy Burbelko; Edward Fras; Wojciech Kapturkiewicz; Ewa Olejnik

2004-01-01

90

Diffusion rate for the emittance growth due to periodic crossings of nonlinear coupled resonances  

SciTech Connect

Assuming that many betatron oscillations occur between crossings so that the betatron phase is uncorrelated from one crossing to the next, we estimate the diffusion rate for the emittance growth due to periodic crossing of coupled nonlinear resonances. It was shown that the diffusion rate is more or less independent of the frequency, but it is inversely proportional to the modulation amplitude.

Shi, J. (Texas Univ., Houston, TX (United States). Dept. of Physics); Gluckstern, R.L.; Ohnuma, S. (Brookhaven National Lab., Upton, NY (United States))

1992-01-01

91

Diffusion rate for the emittance growth due to periodic crossings of nonlinear coupled resonances  

SciTech Connect

Assuming that many betatron oscillations occur between crossings so that the betatron phase is uncorrelated from one crossing to the next, we estimate the diffusion rate for the emittance growth due to periodic crossing of coupled nonlinear resonances. It was shown that the diffusion rate is more or less independent of the frequency, but it is inversely proportional to the modulation amplitude.

Shi, J. [Texas Univ., Houston, TX (United States). Dept. of Physics; Gluckstern, R.L.; Ohnuma, S. [Brookhaven National Lab., Upton, NY (United States)

1992-06-01

92

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

Microsoft Academic Search

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

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

2010-01-01

93

The Global Diffusion Patterns of Successive Technology Generations: Modeling Analog and Digital Wireless Phone Growth  

Microsoft Academic Search

IT is a proven driver of economic growth and social development. Recent large-scale adoption of digital wireless phones among developed and developing countries has driven the expectation that high penetration will eventually pay off in economic returns and social benefits. We examine growth models to discover diffusion patterns of analog and digital wireless phones in the global context. We ask:

Robert J. Kauffman; Angsana A. Techatassanasoontorn

2006-01-01

94

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

95

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

SciTech Connect

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

Ortiz, G.G.; Hains, C.P.; Luong, S.; Cheng, J. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Hou, H.Q.; Vawter, G.A. [Sandia National Labs., Albuquerque, NM (United States)

1997-04-01

96

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

SciTech Connect

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

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

2010-03-01

97

Reaction-diffusion controlled growth of complex structures  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

98

Low-Symmetry Diffusion Barriers in Homoepitaxial Growth of Al(111)  

Microsoft Academic Search

From fractals to compact islands, epitaxial growth offers an exotic variety of surface morphologies that emanate from a handful of elementary atomic diffusion processes. Adsorption calculations have hitherto been limited to high-symmetry configurations, or to semiquantitative methods. Using extensive density-functional calculations on parallel computers we map out barriers for self-diffusion at steps, kinks, and corners on Al(111). The results reveal

Alexander Bogicevic; Johan Strömquist; Bengt I. Lundqvist

1998-01-01

99

Diffusivity and growth rate of silicon in solid-phase epitaxy with an aluminum medium  

NASA Astrophysics Data System (ADS)

Using the classical diffusion equation for an amorphous (a)-Si-Al-Si sandwich structure, the diffusivity of a-Si in Al between 470-570 C has been measured, and the mass-transfer coefficient under the equilibrium solid-phase epitaxial growth condition has been derived. These data can be used to explain recent results of junction formation by solid-phase epitaxy. The activation energy of this process is found to be 0.80 eV.

Qingheng, H.; Yang, E. S.; Izmirliyan, H.

1982-12-01

100

Edge effects in crystal growth under intermediate diffusive-kinetic control  

NASA Astrophysics Data System (ADS)

Crystal growth on a semiinfinite surface is considered. The remaining semiinfinite part of the plane is covered with a mask on which no crystal growth can occur. The mass-transfer coefficient, which measures the rate at which the surface reaction proceeds, is considered to be finite. Together with the diffusion coefficient D this parameter defines a characteristic time tau and length lambda. A solution valid for large tau is derived. It is shown that crystal-growth conditions change markedly within a neighborhood of the mask edge whose length is of the order of lambda. Outside this region crystal growth is almost fully diffusion-controlled. Within the region surface control exerts its influence, but the grown layer is much thicker there than elsewhere. As long as the grown layer is much thinner than lambda, growth at the mask edge is kinetically controlled.

Kuiken, H. K.

1985-09-01

101

Diffusion-controlled crystal growth in deeply undercooled melt on approaching the glass transition  

NASA Astrophysics Data System (ADS)

Crystal-growth velocity in metallic melts has been reported by others to increase monotonically with undercooling. Nevertheless, such an observation is not predicted by conventional growth theory. In this work, the metallic melt of Zr50Cu50 is studied to address the problem by measuring the growth velocity over a wide range of undercooling up to 325 K. A maximum growth velocity is observed at an undercooling of 200 K instead of the monotonic increase reported in the literature. We find that the planar or dendrite growth theories can explain the value of the maximum growth velocity, but the predicted location of the maximum in undercooling is far less than that seen by experiment. With the assistance of current results, a general pattern of crystal growth is established for melts of a variety of substances, where all sluggish crystal-growth kinetics is explained by the diffusion-controlled mechanism at deep undercooling.

Wang, Q.; Wang, Li-Min; Ma, M. Z.; Binder, S.; Volkmann, T.; Herlach, D. M.; Wang, J. S.; Xue, Q. G.; Tian, Y. J.; Liu, R. P.

2011-01-01

102

Characterization of the diffusion of epidermal growth factor receptor clusters by single particle tracking.  

PubMed

A number of studies have shown that receptors of the epidermal growth factor receptor family (ErbBs) exist as higher-order oligomers (clusters) in cell membranes in addition to their monomeric and dimeric forms. Characterizing the lateral diffusion of such clusters may provide insights into their dynamics and help elucidate their functional relevance. To that end, we used single particle tracking to study the diffusion of clusters of the epidermal growth factor (EGF) receptor (EGFR; ErbB1) containing bound fluorescently-labeled ligand, EGF. EGFR clusters had a median diffusivity of 6.8×10(-11)cm(2)/s and were found to exhibit different modes of transport (immobile, simple, confined, and directed) similar to that previously reported for single EGFR molecules. Disruption of actin filaments increased the median diffusivity of EGFR clusters to 10.3×10(-11)cm(2)/s, while preserving the different modes of diffusion. Interestingly, disruption of microtubules rendered EGFR clusters nearly immobile. Our data suggests that microtubules may play an important role in the diffusion of EGFR clusters either directly or perhaps indirectly via other mechanisms. To our knowledge, this is the first report probing the effect of the cytoskeleton on the diffusion of EGFR clusters in the membranes of live cells. PMID:22974816

Boggara, Mohan; Athmakuri, Krishna; Srivastava, Sunit; Cole, Richard; Kane, Ravi S

2012-09-04

103

Reaction-diffusion model for the growth of avascular tumor.  

PubMed

A nutrient-limited model for avascular cancer growth including cell proliferation, motility, and death is presented. The model qualitatively reproduces commonly observed morphologies for primary tumors, and the simulated patterns are characterized by its gyration radius, total number of cancer cells, and number of cells on tumor periphery. These very distinct morphological patterns follow Gompertz growth curves, but exhibit different scaling laws for their surfaces. Also, the simulated tumors incorporate a spatial structure composed of a central necrotic core, an inner rim of quiescent cells and a narrow outer shell of proliferating cells in agreement with biological data. Finally, our results indicate that the competition for nutrients among normal and cancer cells may be a determining factor in generating papillary tumor morphology. PMID:11863563

Ferreira, S C; Martins, M L; Vilela, M J

2002-01-23

104

Role of sidewall diffusion in GaAs nanowire growth: A first-principles study  

NASA Astrophysics Data System (ADS)

The molecular processes during the growth of GaAs nanowires in molecular beam epitaxy (MBE) are studied from first principles. For the wurtzite crystal structure of GaAs, which is formed exclusively in nanowire growth, potential energy surfaces for sidewall diffusion of Ga, As, and GaAs surface species are calculated using density functional theory. We compare materials transport on type-I and -II nanowires (with {101¯0} and {112¯0} facets of wurtzite GaAs, respectively) and discuss its role for materials supply to the growth zone at the nanowire tip. On the sidewalls of type-II nanowires, the diffusion barrier for Ga along the growth direction is particularly low, only 0.30 eV compared to 0.60 eV on type-I nanowires. For As adatoms, the corresponding diffusion barriers are 0.64 eV and 1.20 eV, respectively, and hence higher than for Ga adatoms. The GaAs molecule formed by the chemical surface reaction of Ga and As finds very stable binding sites on type-II sidewalls where it inserts itself into a chemical bond between surface atoms, triggering radial growth. In contrast, on type-I nanowires the GaAs molecule adsorbed with the As end towards the surface has a low diffusion barrier of 0.50 eV. Together with our previous finding that the gold particle at the nanowire tip is efficient in promoting dissociative adsorption of As2 molecules, we conclude that the influx of Ga adatoms from sidewall diffusion is very important to maintain stoichiometric growth of GaAs nanowires, in particular when a large V-III ratio is used in MBE.

Pankoke, Volker; Sakong, Sung; Kratzer, Peter

2012-08-01

105

An innovative method for preparing semiconductor charges used in crystal growth and shear cell diffusion experiments  

Microsoft Academic Search

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).

William A. Arnold; David Matthiesen; Robert J. Bennett; Douglas T. Jayne

1997-01-01

106

Decomposing productivity growth in OECD countries: domestic R&D vs. international technology diffusion  

Microsoft Academic Search

This paper decomposes productivity growth across highly developed OECD coun- tries in the period 1972-2000 into components attributable to domestic R&D output, a catch- up effect, and international technology diffusion via imports of hi-tech products. Two alternative specifications of \\

Jakub GrowiecLukasz Marc; Dorota Pelle

107

Analysis on the growth of telecommunication services: a global comparison of diffusion patterns  

Microsoft Academic Search

With the development of the Internet, the telecommunication market has seen a rapid shift from voice-based services to data-based services. Relationships of substitutability and complementarity have emerged among communications technology services such as Internet service, mobile phone service and fixed telephone service. The article analyses the diffusion patterns of communication services in different continents. A modified logistic growth model is

Jongsu Lee; Minkyu Lee

2009-01-01

108

Modeling of cavity coalescence during tensile deformation  

Microsoft Academic Search

The effect of material properties such as the cavity growth rate and initial cavity population on cavity coalescence during uniaxial tensile deformation was determined. To this end, a two-dimensional model that treats the growth of a random array of spherical cavities inside a deforming tension specimen was developed. Simulation results included predictions of the conditions under which cavity coalescence occurs,

P. D. Nicolaou; S. L. Semiatin

1999-01-01

109

Analysis of cell growth kinetics and substrate diffusion in a polymer scaffold.  

PubMed

The cultivation of cartilage cells (chondrocytes) in polymer scaffolds leads to implants that may potentially be used to repair damaged joint cartilage or for reconstructive surgery. For this technique to be medically applicable, the physical parameters that govern cell growth in a polymer scaffold must be understood. This understanding of cell behavior under in vitro conditions, where diffusion is the primary mode of transport of nutrients, may aid in the scale-up of the cartilage generation process. A mathematical model of chondrocyte generation and nutrient consumption is developed here to analyze the behavior of cell growth in a biodegradable polymer matrix for a series of different thickness polymers. Recent literature has implied that the diffusion of nutrients is a major factor that limits cell growth (Freed et al., 1994). In the present paper, a mathematical model is developed to directly relate the effects of increasing cell mass in the polymer matrix on the transport of nutrients. Reaction and diffusion of nutrients in the cell-polymer system are described using the fundamental species continuity equations and the volume averaging method. The volume averaging method is utilized to derive a single averaged nutrient continuity equation that includes the effective transport properties. This approach allows for the derivation of effective diffusion and rate coefficients as functions of the cell volume fraction. The cell volume fraction as a function of time is determined by solution of a material balance on cell mass. Growth functions including the Moser, a modified Contois, and an nth-order heterogeneous growth kinetic model are evaluated through a parameter analysis, and the results are compared to experimental data found in the literature. The results indicate that cellular functions in conjunction with mass transfer processes can account partially for the general trends in the cell growth behavior for various thickness polymers. The Contois growth function appeared to describe the data more accurately in terms of the lag period at early times and the long time limits. However, all kinetic growth functions required variations in the kinetic parameters to fully describe the effects of polymer thickness. This result implies that restricted diffusion of nutrients is not the sole factor limiting cell growth when the thickness of the polymer is changed. Therefore, further experimental data and model improvements are needed to accurately describe the cell growth process. PMID:10458732

Galban, C J; Locke, B R

1999-10-20

110

Development of growth and fabrication technology for gallium nitride-based vertical cavity surface emitting lasers  

NASA Astrophysics Data System (ADS)

Since their introduction, the demand for GaN light emitting diodes (LEDs) has skyrocketed for applications in lighting and displays. For many of these applications, the directionality and low cost provided by resonant cavity LEDs (RCLEDs) and the yet unrealized GaN vertical cavity laser (VCSEL) are attractive. These devices however---VCSELs in particular---require an extreme degree of precision in their fabrication in order to avoid any show-stopping losses. Unfortunately, the lack of a lattice matched substrate, the extreme resistivity of the p-doped layers, and the resistance of GaN to conventional wet etching, preclude taking some of the more common approaches (such as incorporating an epitaxial DBR) to making these devices. This work discusses the research on development and optimization of technologies to overcome these inherent difficulties in device fabrication. We present a structure that incorporates two dielectric mirrors after flip-chip bonding and the removal of the original substrate. A transparent current spreading contact is used to overcome the resistivity of the p-GaN, although an alternative method of current confinement using ion implantation is also explored. The resulting RCLED allows us to more thoroughly analyze our design and make a prediction as to how much further the structures must be pushed before lasing threshold is realized.

Margalith, Tal

111

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

NASA Astrophysics Data System (ADS)

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

Nayak, A. K.; Bhattacharyya, S.

2012-12-01

112

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

NASA Astrophysics Data System (ADS)

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

Sarma, Biplab

113

Germanium diffusion during HfO{sub 2} growth on Ge by molecular beam epitaxy  

SciTech Connect

The authors study the Ge diffusion during HfO{sub 2} growth by molecular beam epitaxy on differently in situ prepared germanium substrates and at different growth temperatures. While HfO{sub 2} layers grown directly on Ge do not show any germanium contamination, oxygen rich interfacial layers such as GeO{sub x} or GeO{sub x}N{sub y} partly dissolve into the HfO{sub 2} layer, giving rise to high Ge contamination (from 1% to 10%). The use of nitridated interfacial layers does not prevent Ge diffusion into the HfO{sub 2} during the growth process because of the high oxygen content present in the nitridated germanium layer.

Ferrari, S.; Spiga, S.; Wiemer, C.; Fanciulli, M.; Dimoulas, A. [Laboratorio MDM-INFM-CNR, Via Olivetti, 2 Agrate Brianza, Milano 20041 (Italy); MBE Laboratory, Institute of Materials Science, DEMOKRITOS National Center for Scientific Research, 153 10 Athens (Greece)

2006-09-18

114

A method for turbidimetric measurement of bacterial growth in liquid cultures and agar plug diffusion cultures, using standard test tubes  

Microsoft Academic Search

A method has been developed for turbidimetric measurement of bacterial growth in standard inexpensive test tubes with closures in-place. Liquid cultures and agar plug diffusion cultures can be assayed using an unmodified spectrophotometer. Growth curves of replicate cultures grown in test tubes, are reproducible with respect to similarity of curve shape, onset of logarithmic growth phase, and maximum growth.

K. J. Brown

1980-01-01

115

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

116

A finite volume method for trace element diffusion and partitioning during crystal growth  

NASA Astrophysics Data System (ADS)

A finite volume method on a uniform grid is presented to compute the polythermal diffusion and partitioning of a trace element during the growth of a porphyroblast crystal in a uniform matrix and in linear, cylindrical and spherical geometry. The motion of the crystal-matrix interface and the thermal evolution are prescribed functions of time. The motion of the interface is discretized and it advances from one cell boundary to next as the prescribed interface position passes the cell center. The appropriate conditions for the flux across the crystal-matrix interface are derived from discrete mass conservation. Numerical results are benchmarked against steady and transient analytic solutions for isothermal diffusion with partitioning and growth. Two applications illustrate the ability of the model to reproduce observed rare-earth element patterns in garnets (Skora et al., 2006) and water concentration profiles around spherulites in obsidian (Watkins et al., 2009). Simulations with diffusion inside the growing crystal show complex concentration evolutions for trace elements with high diffusion coefficients, such as argon or hydrogen, but demonstrate that rare-earth element concentrations in typical metamorphic garnets are not affected by intracrystalline diffusion.

Hesse, Marc A.

2012-09-01

117

Image guided personalization of reaction-diffusion type tumor growth models using modified anisotropic eikonal equations.  

PubMed

Reaction-diffusion based tumor growth models have been widely used in the literature for modeling the growth of brain gliomas. Lately, recent models have started integrating medical images in their formulation. Including different tissue types, geometry of the brain and the directions of white matter fiber tracts improved the spatial accuracy of reaction-diffusion models. The adaptation of the general model to the specific patient cases on the other hand has not been studied thoroughly yet. In this paper, we address this adaptation. We propose a parameter estimation method for reaction-diffusion tumor growth models using time series of medical images. This method estimates the patient specific parameters of the model using the images of the patient taken at successive time instances. The proposed method formulates the evolution of the tumor delineation visible in the images based on the reaction-diffusion dynamics; therefore, it remains consistent with the information available. We perform thorough analysis of the method using synthetic tumors and show important couplings between parameters of the reaction-diffusion model. We show that several parameters can be uniquely identified in the case of fixing one parameter, namely the proliferation rate of tumor cells. Moreover, regardless of the value the proliferation rate is fixed to, the speed of growth of the tumor can be estimated in terms of the model parameters with accuracy. We also show that using the model-based speed, we can simulate the evolution of the tumor for the specific patient case. Finally, we apply our method to two real cases and show promising preliminary results. PMID:19605320

Konukoglu, Ender; Clatz, Olivier; Menze, Bjoern H; Stieltjes, Bram; Weber, Marc-André; Mandonnet, Emmanuel; Delingette, Hervé; Ayache, Nicholas

2009-07-14

118

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

119

Cavity growth and creep rate taking into account the change of net stress  

Microsoft Academic Search

An expression is derived for the rate of void growth on grain boundaries taking into account the fact that the voids cause a reduction of the load-bearing area and thus an increase of the stress. Constant-stress creep tests were performed on OFHC copper at 425° C and the data used to evaluate the proposed equation.

F. H. Vitovec

1972-01-01

120

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

SciTech Connect

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

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

2010-03-01

121

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

NASA Astrophysics Data System (ADS)

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

Carpenter, John Halsey

122

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

NASA Astrophysics Data System (ADS)

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

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

1991-06-01

123

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

PubMed Central

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

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

2009-01-01

124

Growth of bulk SiGe single crystals by liquid phase diffusion  

NASA Astrophysics Data System (ADS)

The article presents a study for liquid phase diffusion (LPD) growth of compositionally graded, germanium-rich SixGe1-x single crystals of 25 mm in diameter for use as lattice-matched substrates for the growth of SixGe1-x single crystals by liquid phase electropitaxy (LPEE), or traveling heater method (THM). Grown crystals were characterized by microscopic examination after chemical etching for delineation of the degree of single crystallinity and growth striations. Compositional mapping of selected crystals was performed by using electron probe micro analysis (EPMA) as well as energy dispersive X-ray analysis (EDX). It was shown that the LPD technique can be utilized to obtain SixGe1-x single crystals up to 6 8 at% Si with uniform radial composition distribution.

Yildiz, M.; Dost, S.; Lent, B.

2005-06-01

125

Complex morphogenesis of surfaces: theory and experiment on coupling of reaction-diffusion patterning to growth.  

PubMed

Reaction-diffusion theory for pattern formation is considered in relation to processes of biological development in which there is continuous growth and shape change as each new pattern forms. This is particularly common in the plant kingdom, for both unicellular and multicellular organisms. In addition to the feedbacks in the chemical dynamics, there is then another loop linking size and shape changes with the reaction-diffusion patterning of growth controllers in the growing region. In studies by computation, the codes must incorporate, alongside the usual solvers of the partial differential dynamic equations, a versatile growth code, to express any kind of shape change. We have found that regulation of shape change in particular ways (e.g. to make narrow-angle branchings) demands new features in our chemical mechanisms. Our growth algorithm is for a surface growing tangentially, but moving outward and changing shape to accommodate the extra area. This is potentially applicable both to the tunica layer of multicellular plant meristems and to the growing tip of the cell surface, e.g. in the morphogenesis of single-celled chlorophyte algae which display branching processes: whorl formation in Acetabularia (Dasycladales) and repeated dichotomous branching in Micrasterias (Desmidiaceae). For computational studies, a hemispherical shell is a reasonable idealization of the initial shape. We describe results of two types of study: (1) Pattern formation by three reaction-diffusion models, with contrasted nonlinearities, on the hemispherical shell, particularly to find conditions for robust formation of annular pattern or pattern for dichotomous branching, both of which are common in plants. (2) Sequential dichotomous branchings in a system growing and changing in shape from the hemispherical start. PMID:11901681

Harrison, L G; Wehner, S; Holloway, D M

2001-01-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

127

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

128

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

PubMed

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

Stephen, Manju M; Jayanthi, Jayaraj L; Unni, Nisha G; Kolady, Philip E; Beena, Valappil T; Jeemon, Panniyammakal; Subhash, Narayanan

2013-06-01

129

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

130

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

131

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

132

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

133

A recursive anisotropic fast marching approach to reaction diffusion equation: application to tumor growth modeling.  

PubMed

Bridging the gap between clinical applications and mathematical models is one of the new challenges of medical image analysis. In this paper, we propose an efficient and accurate algorithm to solve anisotropic Eikonal equations, in order to link biological models using reaction-diffusion equations to clinical observations, such as medical images. The example application we use to demonstrate our methodology is tumor growth modeling. We simulate the motion of the tumor front visible in images and give preliminary results by solving the derived anisotropic Eikonal equation with the recursive fast marching algorithm. PMID:17633740

Konukoglu, Ender; Sermesant, Maxime; Clatz, Olivier; Peyrat, Jean-Marc; Delingette, Hervé; Ayache, Nicholas

2007-01-01

134

Diffusion controlled ice growth with soft impingement inside biological cells during freezing.  

PubMed

An iterative method has been proposed to determine the relationship between the temperature depression of intracellular ice formation (IIF) and the equilibrium melting point depression for initial cryoprotective agent (CPA) concentrations larger than 1.5M. Using the iterative method coupling with a water transport model for freezing induced cell dehydration and intracellular ice growth, the temperature of IIF has been determined. The new model of temperature of IIF has been applied to predict nucleation parameters at various temperature and initial CPA concentrations according to Karlsson's approach. A geometrical model of soft impingement proposed by Bruna has been incorporated into Karlsson's diffusion limited crystal growth model to include the effect of soft impingement. The new crystal growth model has been verified by a comparison between the predicted critical cooling rates for vitrification with the reported values in literature. With the new crystal growth model, it has been found that the limiting value of the crystallized volume fraction increases as cooling progresses and decreases as the initial CPA concentration increases. A comparison of simulated crystallized volume fractions when soft impingement, hard impingement and no corrections are used has also been made and the result shows that soft impingement could not be omitted in the prediction of intracellular ice formation and growth, especially when the final crystallized volume fraction is larger than 0.1. PMID:18946551

Chen, Cong; Li, Weizhong

135

Phytoplankton growth rates estimated from depth profiles of cell concentration and turbulent diffusion  

NASA Astrophysics Data System (ADS)

We develop a theory for estimating the net population growth rate (reproductive rate minus mortality rate) of a phytoplankton population in situ from biological observations of cell concentrations and physical measurements of turbulance. High resolution vertical profiles of cell concentration and turbulent diffusion rates from the central North Atlantic measured on successive days were used to study depth-dependent growth rates for categories of ultraphytoplankton defined by flow cytometry. The four categories and their equivalent spherical diameters were cyanobacteria (?1 ?m), the abundant newly discovered very small red fluorescing bodies (prochlorophytes <1 ?m), small eukaryotes (<2 ?m) large eukaryotes (mean 2-4 ?m, mode 2-3 ?m). For all groups, the highest net population growth rates occurred in areas of peak cell concentration near the top of the nitracline and the bottom of the euphotic zone around the 1% light level. Cyanobacteria grew most rapidly between 85 and 95 m, whereas eukaryotes grew most rapidly between 100 and 115 m; the maximum population growth rates were 0.48 ± 0.07 d -1 for cyanobacteria, and 1.43 ± 0.32 d -1 and 0.20 ± 0.03 d -1 for small and large eukaryotes, respectively. Oriented motility toward the region of peak cell concentration may have contributed to the apparently high maximum growth rate of the small eukaryotes. The most negative rates of population growth occurred adjacent to the regions of peak cell concentration, consistent with previous observations of densest concentrations of zooplankton grazers around and above the deep chlorophyll maximum. Below about 150 m, at light intensities <0.1% of surface values, cell concentrations of all ultraphytoplankton groups decreased exponentially with depth, corresponding to net population growth rates ranging from -0.5 to -2.0 d -1 in this region.

Lande, Russell; Li, William K. W.; Horne, Edward P. W.; Wood, A. Michelle

1989-08-01

136

The Influence of Surface Tension on the Diffusion-Controlled Growth or Dissolution of Spherical Gas Bubbles  

Microsoft Academic Search

Surface tension can markedly affect the growth or dissolution of small gas bubbles but, even when spherical symmetry is maintained and the interfacial concentration assumed constant, generally valid analytical solutions for the change of size with time cannot be obtained; approximations of limited validity are therefore often used. However, accurate and efficient methods for computing the diffusion-controlled growth or dissolution

M. Cable; J. R. Frade

1988-01-01

137

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

138

Layered growth of the quasicrystalline decagonal Al3Pd phase in Al\\/Pd lateral diffusion couples  

Microsoft Academic Search

The solid-state reaction in an Al\\/Pd lateral diffusion couple starts with the growth of the crystalline Al3Pd2(delta) phase. When the growth of Al3Pd2 reaches its critical length, the quasicrystalline decagonal Al3Pd(gamma') phase starts to grow and both the Al3Pd2 and Al3Pd phases continue to grow afterwards. We have fitted this simultaneous growth with a recently proposed model of kinetic suppression

B. Blanpain; J. W. Mayer; Joyce C. Liu; K. N. Tu

1990-01-01

139

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

NASA Astrophysics Data System (ADS)

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

Sgura, Ivonne; Bozzini, Benedetto; Lacitignola, Deborah

2012-11-01

140

Lateral diffusion of nerve growth factor receptor: modulation by ligand-binding and cell-associated factors.  

PubMed Central

We compared the properties in human melanoma cell line A875 and rat pheochromocytoma cell line PC12 of nerve growth factor receptor (NGFr). We also analyzed NGFr and a truncated NGFR lacking the cytoplasmic domain, which were transiently expressed in COS cells. The full-length NGFR expressed in COS cells bound nerve growth factor (NGF) with positive cooperativity, but A875 NGFr and truncated NGFr in COS cells did not display positive cooperativity. The anti-human NGFr monoclonal antibody NGFR5 was characterized and found not to compete with NGF for binding to NGFr. Fabs were prepared from NGFR5 and 192, an anti-rat NGFR monoclonal antibody that was previously shown not to compete with NGF for binding. Fluorescein-labeled Fabs were used to measure the distribution and lateral diffusion of the NGFr. NGFr expressed on COS and A875 cells are diffusely distributed, but NGFr on the surface of PC12 cells appeared, for some cells, to be patched. In A875 cells, 51% of the NGFr was free to diffuse with diffusion coefficient (D) approximately 7 X 10(-10) cm2/s. In COS cells, 43% diffused with D approximately 5 X 10(-10) cm2/s. There was no significant difference in diffusibility between the full-length NGFr and the truncated NGFr. We compared NGFr diffusion on PC12 cells in suspension or adherent to collagen-coated coverslips. For suspension cells, we obtained 32% recovery with D approximately 2.5 X 10(-9) cm2/s. On adherent cells, we obtained 17% recovery with 6 X 10(-9) cm2/s. Binding of NGF enhanced lateral diffusion of NGFr in A875 cells and in PC12 cells in suspension but did not alter lateral diffusion of NGFr in COS cells or in adherent PC12 cells. NGF had no effect on the diffusing fraction or the distribution of NGFR for any cell line. Images

Venkatakrishnan, G; McKinnon, C A; Ross, A H; Wolf, D E

1990-01-01

141

Effect of ion irradiation on the interdiffusion growth of aluminide phases in Ti Al diffusion couple  

NASA Astrophysics Data System (ADS)

During annealing on the Ti surface coated by the Al film, different aluminide phases were formed as the result of reactions between Ti and Al. Preliminary irradiation of the Al film with the thickness of 7 ?m by Ti+ ions had a strong effect on the interdiffusion growth of aluminide phases on the Ti substrate. Preliminary ion irradiation resulted in the development of more homogeneous and fine-grain microstructure during subsequent annealing. During ion irradiation of the two-phase (TiAl + Ti3Al) overlayer the decomposition of the TiAl compound and the formation of Ti3Al happened. In the processing of subsequent annealing, diffusion cementation of the overlayer occurred faster on the surface of the irradiated samples. After irradiation by different ions (Ti+ and Al+), and during subsequent annealing the kinetics of structural formation developed in a different way.

Romankov, S. E.; Mamaeva, A.; Vdovichenko, E.; Ermakov, E.

2005-08-01

142

Unified moving-boundary model with fluctuations for unstable diffusive growth  

NASA Astrophysics Data System (ADS)

We study a moving-boundary model of nonconserved interface growth that implements the interplay between diffusive matter transport and aggregation kinetics at the interface. Conspicuous examples are found in thin-film production by chemical vapor deposition and electrochemical deposition. The model also incorporates noise terms that account for fluctuations in the diffusive and attachment processes. A small-slope approximation allows us to derive effective interface evolution equations (IEEs) in which parameters are related to those of the full moving-boundary problem. In particular, the form of the linear dispersion relation of the IEE changes drastically for slow or for instantaneous attachment kinetics. In the former case the IEE takes the form of the well-known (noisy) Kuramoto-Sivashinsky equation, showing a morphological instability at short times that evolves into kinetic roughening of the Kardar-Parisi-Zhang (KPZ) class. In the instantaneous kinetics limit, the IEE combines the Mullins-Sekerka linear dispersion relation with a KPZ nonlinearity, and we provide a numerical study of the ensuing dynamics. In all cases, the long preasymptotic transients can account for the experimental difficulties in observing KPZ scaling. We also compare our results with relevant data from experiments and discrete models.

Nicoli, Matteo; Castro, Mario; Cuerno, Rodolfo

2008-08-01

143

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.

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

2013-01-01

144

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

PubMed

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

2013-10-01

145

Unified moving-boundary model with fluctuations for unstable diffusive growth.  

PubMed

We study a moving-boundary model of nonconserved interface growth that implements the interplay between diffusive matter transport and aggregation kinetics at the interface. Conspicuous examples are found in thin-film production by chemical vapor deposition and electrochemical deposition. The model also incorporates noise terms that account for fluctuations in the diffusive and attachment processes. A small-slope approximation allows us to derive effective interface evolution equations (IEEs) in which parameters are related to those of the full moving-boundary problem. In particular, the form of the linear dispersion relation of the IEE changes drastically for slow or for instantaneous attachment kinetics. In the former case the IEE takes the form of the well-known (noisy) Kuramoto-Sivashinsky equation, showing a morphological instability at short times that evolves into kinetic roughening of the Kardar-Parisi-Zhang (KPZ) class. In the instantaneous kinetics limit, the IEE combines the Mullins-Sekerka linear dispersion relation with a KPZ nonlinearity, and we provide a numerical study of the ensuing dynamics. In all cases, the long preasymptotic transients can account for the experimental difficulties in observing KPZ scaling. We also compare our results with relevant data from experiments and discrete models. PMID:18850840

Nicoli, Matteo; Castro, Mario; Cuerno, Rodolfo

2008-08-11

146

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

PubMed Central

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.

Poplawski, Nikodem J.; Swat, Maciej; Gens, J. Scott; Glazier, James A.

2007-01-01

147

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

PubMed Central

Despite numerous clinical trials over the past 2 decades, the overall survival for children diagnosed with diffuse intrinsic pontine glioma (DIPG) remains 9–10 months. Radiation therapy is the only treatment with proven effect and novel therapies are needed. Epidermal growth factor receptor variant III (EGFRvIII) is the most common variant of the epidermal growth factor receptor and is expressed in many tumor types but is rarely found in normal tissue. A peptide vaccine targeting EGFRvIII is currently undergoing investigation in phase 3 clinical trials for the treatment of newly diagnosed glioblastoma (GBM), the tumor in which this variant receptor was first discovered. In this study, we evaluated EGFRvIII expression in pediatric DIPG samples using immunohistochemistry with a double affinity purified antibody raised against the EGFRvIII peptide. Staining of pediatric DIPG histological samples revealed expression in 4 of 9 cases and the pattern of staining was consistent with what has been seen in EGFRvIII transfected cells as well as GBMs from adult trials. In addition, analysis of tumor samples collected immediately post mortem and of DIPG cells in culture by RT-PCR, western blot analysis, and flow cytometry confirmed EGFRvIII expression. We were therefore able to detect EGFRvIII expression in 6 of 11 DIPG cases. These data suggest that EGFRvIII warrants investigation as a target for these deadly pediatric tumors.

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

2012-01-01

148

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

PubMed

Despite numerous clinical trials over the past 2 decades, the overall survival for children diagnosed with diffuse intrinsic pontine glioma (DIPG) remains 9-10 months. Radiation therapy is the only treatment with proven effect and novel therapies are needed. Epidermal growth factor receptor variant III (EGFRvIII) is the most common variant of the epidermal growth factor receptor and is expressed in many tumor types but is rarely found in normal tissue. A peptide vaccine targeting EGFRvIII is currently undergoing investigation in phase 3 clinical trials for the treatment of newly diagnosed glioblastoma (GBM), the tumor in which this variant receptor was first discovered. In this study, we evaluated EGFRvIII expression in pediatric DIPG samples using immunohistochemistry with a double affinity purified antibody raised against the EGFRvIII peptide. Staining of pediatric DIPG histological samples revealed expression in 4 of 9 cases and the pattern of staining was consistent with what has been seen in EGFRvIII transfected cells as well as GBMs from adult trials. In addition, analysis of tumor samples collected immediately post mortem and of DIPG cells in culture by RT-PCR, western blot analysis, and flow cytometry confirmed EGFRvIII expression. We were therefore able to detect EGFRvIII expression in 6 of 11 DIPG cases. These data suggest that EGFRvIII warrants investigation as a target for these deadly pediatric tumors. PMID:22382786

Li, Gordon; Mitra, Siddhartha S; Monje, Michelle; Henrich, Kristy N; Bangs, C Dana; Nitta, Ryan T; Wong, Albert J

2012-03-02

149

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

Microsoft Academic Search

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

Samuel T Picraux; Shadi A Dayeh

2010-01-01

150

Analysis of the influence of coupled diffusion on transport in protein crystal growth for different gravity levels.  

PubMed

Diffusion has a central role in protein crystal growth both in microgravity conditions and on ground. Recently several reports have been focused on the importance to use the generalized Fick's equations in n-component systems where crystals grow. In these equations the total flux of each component is produced by the own concentration gradient (main flow) and by the concentration gradient of the other components (cross-flow) present in the system. However in literature the latter effect is often neglected, and the so-called pseudo-binary approximation is used. Lin et al. (1995) proposed a mathematical model to evaluate the concentration profile of the species present around a growing protein crystal. Although the model is reliable, it suffers of the pseudo-binary approximation (neglecting cross term diffusion coefficients and using binary diffusion coefficients), probably because of the lack of multicomponent diffusion data. The present model is based on the experimental set-up proposed by Lin et al. (1995). Nevertheless we have included the coupled diffusion effects, according to the correct description of the matter transport through the generalized Fick's equations. The crystal growth rate is calculated for different gravity levels. The model has been applied to the ternary lysozyme-NaCl-water and quaternary lysozyme-poly(ethylene glycol) (PEG)-NaCl-water systems using recent diffusion data. PMID:12351876

Castagnolo, D; Vergara, A; Paduano, L; Sartorio, R; Annunziata, O

2002-09-26

151

Monitoring of tumor growth and post-irradiation recurrence in a diffuse intrinsic pontine glioma mouse model.  

PubMed

Diffuse intrinsic pontine glioma (DIPG) is a fatal malignancy because of its diffuse infiltrative growth pattern. Translational research suffers from the lack of a representative DIPG animal model. Hence, human E98 glioma cells were stereotactically injected into the pons of nude mice. The E98 DIPG tumors presented a strikingly similar histhopathology to autopsy material of a DIPG patient, including diffuse and perivascular growth, brainstem- and supratentorial invasiveness and leptomeningeal growth. Magnetic resonance imaging (MRI) was effectively employed to image the E98 DIPG tumor. [(18) F] 3'-deoxy-3'-[(18) F]fluorothymidine (FLT) positron emission tomography (PET) imaging was applied to assess the subcutaneous (s.c.) E98 tumor proliferation status but no orthotopic DIPG activity could be visualized. Next, E98 cells were cultured in vitro and engineered to express firefly luciferase and mCherry (E98-Fluc-mCherry). These cultured E98-Fluc-mCherry cells developed focal pontine glioma when injected into the pons directly. However, the diffuse E98 DIPG infiltrative phenotype was restored when cells were injected into the pons immediately after an intermediate s.c. passage. The diffuse E98-Fluc-mCherry model was subsequently used to test escalating doses of irradiation, applying the bioluminescent Fluc signal to monitor tumor recurrence over time. Altogether, we here describe an accurate DIPG mouse model that can be of clinical relevance for testing experimental therapeutics in vivo. PMID:21159008

Caretti, Viola; Zondervan, Ilse; Meijer, Dimphna H; Idema, Sander; Vos, Wim; Hamans, Bob; Bugiani, Marianna; Hulleman, Esther; Wesseling, Pieter; Vandertop, W Peter; Noske, David P; Kaspers, Gertjan; Molthoff, Carla F M; Wurdinger, Thomas

2010-12-29

152

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

Microsoft Academic Search

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

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

2007-01-01

153

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

Microsoft Academic Search

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

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

154

Theory of the nonsteady diffusion growth of a gas bubble in a supersaturated solution of gas in liquid  

Microsoft Academic Search

Using a self-similar approach a general nonsteady theory is elaborated for the case of the diffusion growth of a gas bubble in a supersaturated solution of gas in liquid. Due to the fact that the solution and the bubble in it are physically isolated, the self-similar approach accounts for the balance of the number of gas molecules in the solution

A. P. Grinin; F. M. Kuni; G. Yu. Gor

2008-01-01

155

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

Microsoft Academic Search

BackgroundIntrauterine growth restriction (IUGR) affects 5–10% of all newborns and is associated with a high risk of abnormal neurodevelopment. The timing and patterns of brain reorganization underlying IUGR are poorly documented. We developed a rabbit model of IUGR allowing neonatal neurobehavioral assessment and high resolution brain diffusion magnetic resonance imaging (MRI). The aim of the study was to describe the

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

2012-01-01

156

Isolation and identification of a light-induced growth inhibitor in diffusates from blue light-illuminated oat (Avena sativa L.) coleoptile tips  

Microsoft Academic Search

The amounts of two growth inhibitors in diffusates from illuminatedhalves of phototropically stimulated oat (Avena sativa L.)coleoptile tips were larger than those from shaded halves. The less polarinhibitor was isolated from diffusates from oat coleoptile tips illuminatedwithblue light, and identified as uridine from 1H NMR spectrum. Thedistribution of endogenous uridine in diffusates from the illuminated andshadedsides of coleoptile tips unilaterally

T. Hasegawa; K. Yamada; S. Kosemura; S. Yamamura; J. Bruinsma; K. Miyamoto; J. Ueda; K. Hasegawa

2001-01-01

157

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

PubMed Central

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

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

2012-01-01

158

Characterization by X-ray micro-tomography of cavity coalescence during superplastic deformation  

SciTech Connect

In the case of single-phase materials, like aluminum alloys, superplastic deformation is generally limited by strain-induced cavitation, which leads to premature fracture. Cavitation is frequently divided in three main steps: nucleation, growth and coalescence of the cavities. The nucleation process is attributed to microcracking or vacancy agglomeration and is located on preferential sites in the alloy, like triple junctions and second phase particles. Growth of cavities has been extensively studied and it is associated to two main mechanisms: vacancy diffusion or plasticity of the matrix surrounding the cavity. The aim of this paper is to give first results of the use of X-ray tomography as a tool of 3D characterization of the coalescence process between cavities during superplastic deformation of an aluminum alloy.

Martin, C.F.; Josserond, C.; Salvo, L.; Blandin, J.J.; Cloetens, P.; Boller, E.

2000-01-31

159

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

160

Quantitative Forward Modeling on the Effect of Growth, Diffusion and Exsolution on Calcite- Dolomite Thermometry Data  

NASA Astrophysics Data System (ADS)

Calcite-dolomite solvus thermometry is commonly used to constrain metamorphic temperatures in carbonates. The temperature dependent Mg-exchange between calcite and dolomite is experimentally well calibrated. Its application to natural contact metamorphic samples appears to be complex, because large variations in Mg- composition are often observed within individual grains, which do not exhibit simple (concentric) zoning patterns. We developed quantitative forward models to evaluate the effect of growth zoning, volume diffusion and formation of submicroscopic exsolution lamellae (<1?m) on the measured Mg-distribution in individual calcite crystals and compare the modeling results to field data. We present detailed calcite-dolomite thermometry data on multiple scales from the Ubehebe Peak contact aureole (USA). At the aureole scale, measured X(Mg) in calcite increases as a function of increasing proximity to the intrusive contact. On the other hand, several hundred analyses obtained on single thin sections commonly result in Gaussian-shaped distributions of measured Mg-content. These variations are approximately ten times higher than the analytical uncertainty, covering a span of more than 100°C in the calculated temperatures. Nevertheless, domains of lower and higher X(Mg)-values that correlate with adjacent silicate minerals are observed at the thin section scale. Lower values correspond to the presence of tremolite and higher values to that of forsterite. This correlation is in agreement with phase petrology, where tremolite is typically formed at lower temperatures than forsterite. Hence, the apparent lower temperatures of calcite in the vicinity of tremolite suggest that the original Mg-content during crystallization is at least partially preserved. Modeling results, based on our best temperature-time path estimates for the Ubehebe Peak aureole and published experimentally derived Mg-diffusion data in calcite, reveal that the original prograde Mg-zoning of calcite will be reset, if the calcite is assumed to grow slowly along a prograde path. In contrast, models of calcite growth in which the entire grain forms over a small temperature interval, as expected for infiltration driven mineral reactions, show that parts of the original lower Mg-compositions can be preserved. Modeled Mg-distributions were transformed into histograms by taking into account intersection probabilities of grains in thin sections and random microprobe analyses. Resulting histograms are similar to the measured ones, but in contrast to our observations the predicted Mg-distribution exhibit clear concentric zoning. For further insight we modeled the effect of retrograde equilibration within a calcite grain through submicroscopic exsolution lamellae. Modeling results for selected values of spot and lamellae sizes yield randomly distributed higher and lower X(Mg)-values, hiding a possible zoning that potentially survived the T-t-path. We thus demonstrate that the Mg-composition of calcite does reflect a memory of the temperature-reaction path, which is partially obscured by diffusion and exsolution.

Mueller, T.; Baumgartner, L.; Foster, C. T.; Roselle, G. T.

2006-12-01

161

The effects of island diffusion and breakup in island growth during ion-beam assisted deposition  

Microsoft Academic Search

In ion-beam assisted deposition (IBAD) island growth is in clear contrast with growth obtained without a bombardment. In this contribution we study the effects of island mobility and island breakup in IBAD by computer simulations. It is shown that during the initial stage of growth a scaling description similar to irreversible growth applies. However, eventually growth attains a quasi-stationary state

M. Rusanen; I. Koponen; J. Heinonen; J. Sillanpää

1999-01-01

162

Cavity coalescence in superplastic deformation  

SciTech Connect

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

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

1984-01-01

163

Effect of basic fibroblast growth factor on experimental focal ischemia studied by diffusion-weighted and perfusion imaging  

Microsoft Academic Search

BACKGROUND AND PURPOSE: Basic fibroblast growth factor (bFGF) has documented neuroprotective properties. This study was performed to evaluate the effects of bFGF on infarct size when administered 30 minutes after induction of focal cerebral ischemia in rats. Diffusion-weighted and perfusion MRI were used during the drug infusion.\\u000aMETHODS: We blindly randomized 20 Sprague-Dawley rats to receive either drug (n =

Turgut Tatlisumak; Kentaro Takano; Richard A. D. Carano; Marc Fisher

1996-01-01

164

Kinetics of NiAl3 and Ni2Al3 phase growth on lateral diffusion couples  

Microsoft Academic Search

The phase formation of NiAl3 and Ni2Al3 is studied on lateral diffusion couples of an Al-rich source on a Ni thin film at temperatures from 375 to 500 °C. Analytical electron microscopy is used to determine the crystal structures, chemical compositions, and the widths of growing phases. Simultaneous growth of NiAl3 and Ni2Al3 is observed at 375 and 450 °C.

Joyce C. Liu; J. W. Mayer; J. C. Barbour

1988-01-01

165

Kinetics of NiAl3 and Ni2Al3 phase growth on lateral diffusion couples  

Microsoft Academic Search

The phase formation of NiAlâ and NiâAlâ is studied on lateral diffusion couples of an Al-rich source on a Ni thin film at temperatures from 375 to 500 °C. Analytical electron microscopy is used to determine the crystal structures, chemical compositions, and the widths of growing phases. Simultaneous growth of NiAlâ and NiâAlâ is observed at 375 and 450 °C.

Joyce C. Liu; J. W. Mayer; J. C. Barbour

1988-01-01

166

X-Ray Diffuse Scattering Study of the Kinetics of Stacking Fault Growth and Annihilation in Boron-Implanted Silicon.  

SciTech Connect

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 925 - 1025 C. From the growth kinetics we obtain an activation energy for interstitial migration in silicon: E{sub 1} = 1.98{+-}0.06eV. The measurements of intensity and size versus time suggest that faults do not shrink and disappear but rather are annihilated by a dislocation reaction mechanism.

Patel, Jamshed R.

2002-06-14

167

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.

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

2006-01-01

168

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

169

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

170

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

PubMed

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

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

2013-06-27

171

Diffusion model of the formation of growth microdefects as applied to the description of defect formation in heat-treated silicon single crystals  

NASA Astrophysics Data System (ADS)

The diffusion model of the formation of growth microdefects has been considered as applied to the description of defect formation in heat-treated silicon single crystals. It has been shown that, in the framework of the proposed kinetic model of defect formation, the formation and development of the defect structure during the growth of a crystal and its heat treatment can be considered within a unified context. The mathematical apparatus of the diffusion model can provide a basis for the development of a program package for the analysis and calculation of the formation of growth and postgrowth microdefects in dislocation-free silicon single crystals. It has been demonstrated that the diffusion model of the formation of growth and post-growth microdefects allows one to determine necessary conditions for the growth of a crystal and the regimes of its heat treatment for the preparation of a precisely defined defect structure.

Talanin, V. I.; Talanin, I. E.

2013-02-01

172

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

173

Diffusion distances of the constituent atoms in the metallurgical phenomena such as recovery, recrystallization, grain growth, and aging in aluminum and copper alloys  

Microsoft Academic Search

It is known that metallurgical phenomena such as recovery, recrystallization, grain growth, and aging are due to the diffusion\\u000a of constituent atoms in materials. The heat treatments that cause these phenomena are conducted defining both time and temperature.\\u000a In the diffusion process, it is the diffusion distance that is defined by both time and temperature. Therefore, the authors\\u000a surmise that

Y. Fukuda; Y. Kado; T. Yoshikawa; K. Oishi; Y. Mae

2002-01-01

174

Viscous cavities  

NASA Astrophysics Data System (ADS)

We study experimentally the impact of solid spheres in a viscous liquid at moderate Reynolds numbers (Re ~ 5-100). We first determine the drag force by following the slowdown dynamics of projectiles. We then focus on the shape of the free surface: such impacts generate cavities, whose original shape is described and modeled.

Le Goff, Anne; Quéré, David; Clanet, Christophe

2013-04-01

175

Growth of atomically thin hexagonal boron nitride films by diffusion through a metal film and precipitation  

NASA Astrophysics Data System (ADS)

Atomically thin hexagonal boron nitride films were grown on both the top and bottom surfaces of a polycrystalline Co or Ni film by annealing a Co (Ni)/amorphous boron nitride/SiO2 structure in vacuum. This method of growing hexagonal boron nitride is much simpler than other methods, such as thermal chemical vapour deposition. B and N atoms diffuse through the metal film, although N is almost completely insoluble in both Co and Ni, and precipitation occurs at the topmost surface. The mass transport is considered to be caused by grain boundary diffusion.

Suzuki, Satoru; Molto Pallares, Roger; Hibino, Hiroki

2012-09-01

176

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

PubMed Central

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

Saridakis, E.; Chayen, N. E.

2000-01-01

177

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

SciTech Connect

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

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

2012-03-15

178

Bubble growth within the skin by rectified diffusion might play a significant role in sonophoresis  

Microsoft Academic Search

Low frequency ultrasound has successfully been used for enhancing transdermal transport of a variety of different molecules. This phenomenon is referred to as sonophoresis. Several attempts have been made to investigate the enhancing mechanism in order to modulate the overall process.In this study we assess whether rectified diffusion is a process that occurs within the skin, which could eventually lead

Ilana Lavon; Nili Grossman; Joseph Kost; Eitan Kimmel; Giora Enden

2007-01-01

179

Volume diffusion-controlled growth kinetics and mechanisms in binary alloys  

Microsoft Academic Search

Growth kinetics and stability of simple precipitate morphologies which develop during solid-solid phase transformations in binary alloys will be briefly reviewed. Emphasis will be placed on our current understanding of the dependence of growth kinetics on the shape of precipitates and on the interfacial structure. As an example, we shall consider the lengthening kinetics of Widmanstatten precipitates and develop a

Trivedi

1981-01-01

180

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

181

Spectral Properties of Multigroup Diffusion Problem.  

National Technical Information Service (NTIS)

An eigenvalue problem has been considered for a diffusion multigroup approximation. The equations are written in the volume V which may contain a cavity, nonlocal boundary conditions being assumed on the boundary of the cavity. The completeness in the Hil...

V. M. Novikov A. I. Popykin

1976-01-01

182

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

183

A Recursive Anisotropic Fast Marching Approach to Reaction Diffusion Equation: Application to Tumor Growth Modeling  

Microsoft Academic Search

Bridging the gap between clinical applications and mathematical models is one of the new challenges of medical image analysis.\\u000a In this paper, we propose an efficient and accurate algorithm to solve anisotropic Eikonal equations, in order to link biological\\u000a models using reaction-diffusion equations to clinical observations, such as medical images. The example application we use\\u000a to demonstrate our methodology is

Ender Konukoglu; Maxime Sermesant; Olivier Clatz; Jean-marc Peyrat; Hervé Delingette; Nicholas Ayache

2007-01-01

184

The effects of ethanol on growth rate and passive proton diffusion in yeasts  

Microsoft Academic Search

Summary When cell suspensions of Saccharomyces cerevisiae NRRL-Y132 and Kluyveromyces marxianus IGC-2771 were incubated in the presence of different concentrations of ethanol, the final stable pH values (pHf) reached in these suspensions increased with increasing ethanol concentration, indicating that ethanol enhanced passive proton diffusion into the cells. The plots of pHf as a function of ethanol concentration were linear but

S. G. Kilian; J. C. Preez; Mariekie Gericke

1989-01-01

185

Experimental investigation of a chemical laser cavity flowfield  

Microsoft Academic Search

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold air as the working medium, the flow control system configuration and nozzle-cavity-supersonic diffuser assembly configuration were developed to establish acceptable flow

Stephen Walter Stiglich Jr.

1989-01-01

186

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.

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

2011-01-01

187

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

188

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

189

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

190

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

PubMed

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 degrees 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 SiO(2) layer. PMID:20672089

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

2010-02-01

191

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

PubMed Central

Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 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.

2010-01-01

192

On the growth and magnetic properties of flower-like nanostructures formed on diffusion of FePt with Si substrate  

NASA Astrophysics Data System (ADS)

Nearly equi-atomic FePt films were deposited on a silicon substrate with a native SiO2 layer by co-sputtering technique. Structural and magnetic properties of the films are influenced by the growth temperature. The native SiO2 layer acts as a diffusion barrier for the FePt film on Si. In the absence of diffusion of Fe and Pt with Si substrate, a high coercivity (˜8.2 kOe) L10 Fe50Pt50 phase is formed. Depending on the growth temperature and the thickness/quality (continuously or containing some pinholes) of SiO2 layer, diffusion of FePt film with Si substrate is observed. Diffusion results in the change in film composition, and formation of various Fe- and Pt-silicide phases along with the flower-like surface morphology. Growth of flower like nano-structures are shown to be governed by the accelerated diffusion of Fe on a dimpled surface of Si substrate. The detailed structural and magnetic characterization revealed that the flower-like patterns are composed of chemically ordered antiferromagnetic FePt3 phase (Q2-type). The Neel's temperature for these flowers-like nano-structures is ˜80 K and they are surrounded by a ferromagnetic matrix. Growth mechanism of flower-like patterns is identified. Site specific growth of antiferromagnetic nano-structures in a ferromagnetic matrix is also demonstrated.

Sharma, Parmanand; Kaushik, Neelam; Esashi, Masayoshi; Nishijima, Masahiko; Makino, Akihiro

2013-07-01

193

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

SciTech Connect

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

van Dongen, P.G.J.

1988-10-01

194

Mathematical models and simulations of bacterial growth and chemotaxis in a diffusion gradient chamber.  

PubMed

The diffusion gradient chamber (DGC) is a novel device developed to study the response of chemotactic bacteria to combinations of nutrients and attractants [7]. Its purpose is to characterize genetic variants that occur in many biological experiments. In this paper, a mathematical model which describes the spatial distribution of a bacterial population within the DGC is developed. Mathematical analysis of the model concerning positivity and boundedness of the solutions are given. An ADI (Alternating Direction Implicit) method is constructed for finding numerical solutions of the model and carrying out computer simulations. The numerical results of the model successfully reproduced the patterns that were observed in the experiments using the DGC. PMID:11261315

Chiu, C; Hoppensteadt, F C

2001-02-01

195

Volume diffusion-controlled growth kinetics and mechanisms in binary alloys  

SciTech Connect

Growth kinetics and stability of simple precipitate morphologies which develop during solid-solid phase transformations in binary alloys will be briefly reviewed. Emphasis will be placed on our current understanding of the dependence of growth kinetics on the shape of precipitates and on the interfacial structure. As an example, we shall consider the lengthening kinetics of Widmanstatten precipitates and develop a stability criteria which determines the dimension of the advancing tip of these precipitates. These theoretical results will then be compared with the available experimental data in binary alloys. The importance of interface structure in determining growth kinetics will also be illustrated by considering the migration rate of partially coherent interphase boundaries with ledge structures. These results will then be synthesized to understand the development and stability of microstructures in binary alloys.

Trivedi, R.

1981-01-01

196

Characterization of Diffusion-Controlled Growth and Dissolution of Methane Hydrate in Aqueous Solution by Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Most submarine gas hydrates occur within the two-phase equilibrium region of hydrate and interstitial water at pressures (P) ranging from 8 to 60 MPa and temperatures (T) from 2 to 20 °C. The dynamics of growth and dissolution of hydrate phases, in the absence of a vapor phase, due to the change of T, P, and salinity under geologic conditions are not well established by existing experimental studies. In this work, we observed growth and dissolution cycles of methane-hydrate crystals in an aqueous solution in a fused silica capillary capsule (FSCC) by changing T in a heating-cooling stage. The maximum T at which this hydrate (H) sample coexists with liquid water (Lw) and vapor was found to be 33.5 °C. At lower T, a ~6 mm long Lw section at one end of the capsule was always separated from the vapor phase at the other end by hydrate crystals in between. After several heating-cooling cycles at T below 30 °C, a large hydrate crystal was formed at the end of the Lw section, which was separated from the vapor phase by other hydrate crystals in between. After keeping the sample at room T for two weeks, we then kept the sample at 2 °C for 6.5 hours until the T was raised to 25 °C for 3 hours. During these T changes, the changes in length of the hydrate crystal were recorded by video, and the changes of methane concentration in Lw at four different points away from the initial H-Lw interface were monitored by Raman spectroscopy (Lu et al., 2006, Appl. Spectr., 60, 122). The rates of growth and dissolution of hydrate crystal were found to be controlled by the rate of methane transfer in solution, which was a function of the concentration gradient and the diffusion coefficient of methane in the solution. The measured apparent diffusion coefficients of methane in water in the presence of hydrate are found to be slightly lower than those without hydrate. Also, the dynamic exchange of methane between solid hydrate and the interstitial water was controlled by the difference in methane concentration at the H-Lw interface and the nearby interstitial water. Our results show that the growth and dissolution rates of methane hydrate in the pores of marine sediments is mass-transport limited instead of reaction limited. In the near future, we will focus on other factors that control the growth and dissolution rates of hydrates in the solution (salinity and P), and to enhance our understanding on the evolution of submarine hydrate systems and their effects on climate change and energy resources.

Lu, W.; Ye, Y.; Chou, I.; Liu, C.; Burruss, R. C.; Wang, F.; Wang, M.

2010-12-01

197

Microstructure and growth kinetics of the Mo 5Si 3 and Mo 3Si layers in MoSi 2\\/Mo diffusion couple  

Microsoft Academic Search

The microstructures and growth kinetics of the Mo5Si3 and Mo3Si layers in the MoSi2\\/Mo diffusion couple was investigated using optical microscopy, field-emission scanning electron microscopy, electron probe microanalyzer, and cross-sectional transmission electron microscopy. The MoSi2\\/Mo diffusion couple was made by chemical vapor deposition CVD of Si on a Mo substrate at 1100 °C and annealed at temperatures between 1250 and 1600 °C

Jin-Kook Yoon; Jong-Kwon Lee; Kyung-Hwan Lee; Ji-Young Byun; Gyeung-Ho Kim; Kyung-Tae Hong

2003-01-01

198

Patterns of inter-sectoral diffusion of technological growth: income, concentration, and public capital stocks  

Microsoft Academic Search

This paper investigates the existence and character of technological growth diffusionin form of learning spillovers at the sector level of the economy. Based on panel datafor 47 countries during the postwar period the evidence suggests robust statisticalregularities of inter-sectoral learning resulting from a changing structure of demand.The findings further show differences in the magnitude of productivity spilloversacross sectors. In particular,

Ute Pieper

2002-01-01

199

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

ERIC Educational Resources Information Center

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

Jolliffe, Lee

200

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

PubMed Central

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

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

2012-01-01

201

Experimental observation and computer simulations of 3D triplet structures in diffusion limited growth of xenon crystals.  

PubMed

Changes of growth morphologies are induced by a perturbation of the thermal diffusion field in the surrounding melt of a growing xenon crystal. Apart from the dendritic morphology, seaweed and doublon morphologies and for the first time transitions from dendritic to triplet structures (first predicted by T. Abel, E. Brener, and H. Müller-Krumbhaar [Phys. Rev. E 55, 7789 (1997)10.1103/PhysRevE.55.7789] were observed experimentally. With 3D phase-field simulations it was possible to reproduce the experimental procedure and to verify that triplet structures can grow in a stable way even in the presence of anisotropic surface free energy as found for experimental substances. PMID:19659157

Singer, H M; Singer, I; Bilgram, J H

2009-07-01

202

Experimental Observation and Computer Simulations of 3D Triplet Structures in Diffusion Limited Growth of Xenon Crystals  

NASA Astrophysics Data System (ADS)

Changes of growth morphologies are induced by a perturbation of the thermal diffusion field in the surrounding melt of a growing xenon crystal. Apart from the dendritic morphology, seaweed and doublon morphologies and for the first time transitions from dendritic to triplet structures (first predicted by T. Abel, E. Brener, and H. Müller-Krumbhaar [Phys. Rev. EPLEEE81063-651X 55, 7789 (1997)10.1103/PhysRevE.55.7789] were observed experimentally. With 3D phase-field simulations it was possible to reproduce the experimental procedure and to verify that triplet structures can grow in a stable way even in the presence of anisotropic surface free energy as found for experimental substances.

Singer, H. M.; Singer, I.; Bilgram, J. H.

2009-07-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

204

Dense fully 111-textured TiN diffusion barriers: Enhanced lifetime through microstructure control during layer growth  

NASA Astrophysics Data System (ADS)

Low-temperature deposition of TiN by reactive evaporation or sputter deposition onto amorphous substrates leads to highly underdense layers which develop mixed 111/002 orientations through competitive growth. In contrast, we demonstrate here the growth of low-temperature (450 °C) fully dense polycrystalline TiN layers with complete 111 texture. This was achieved by reactive magnetron sputter deposition using a combination of: (1) highly oriented 25-nm-thick 0002 Ti underlayers to provide 111 TiN orientation through texture inheritance (local epitaxy) and (2) high flux (JN2+/JTi=14), low-energy (EN2+~=20 eV), N2+ ion irradiation in a magnetically unbalanced mode to provide enhanced adatom diffusion leading to densification during TiN deposition. The Ti underlayers were also grown in a magnetically unbalanced mode, in this case with an incident Ar+/Ti flux ratio of 2 and EAr+~=11 eV. All TiN films were slightly overstoichiometric with a N/Ti ratio of 1.02+/-0.03. In order to assess the diffusion-barrier properties of dense 111-textured TiN, Al overlayers were deposited without breaking vacuum at 100 °C. Al/TiN bilayers were then annealed at a constant ramp rate of 3 °C s-1 to 650 °C s-1 and the interfacial reaction between Al and TiN was monitored by in situ synchrotron x-ray diffraction measurements. As a reference point, we find that interfacial Al3Ti formation is observed at 450 °C in Al/TiN bilayers in which the TiN layer is deposited directly on SiO2 in a conventional magnetically balanced mode and, hence, is underdense with a mixed 111/002 orientation. However, the onset temperature for interfacial reaction was increased to 610 °C in bilayers with fully dense TiN exhibiting complete 111 preferred orientation.

Chun, J.-S.; Petrov, I.; Greene, J. E.

1999-10-01

205

Growth retardation and destruction of experimental squamous cell carcinoma by interstitial radioactive wires releasing diffusing alpha-emitting atoms.  

PubMed

In the present study, we examined the antitumoral effects caused by the release of alpha emitting radioisotopes into solid squamous cell carcinoma (SCC) tumors. Using a novel method termed DART (Diffusing Alpha-emitters Radiation Therapy), we assessed the efficacy of short-lived daughters of (224)Ra releasing alpha particles, dispersing in the malignant tissue, to cause tumor growth retardation and destruction. It was carried out using specially designed wires loaded with (224)Ra activities in the range of 7-42 kBq in a set of experiments performed on BALB/c and nude mice bearing metastatic SCC tumors derived from either mouse SQ2 or human CAL27 cell lines. The insertion of a DART wire to the center of 6-7 mm primary tumors, retarded tumor growth, reduced lung metastatic load, prolonged life expectancy and in some cases caused tumor eradication. These effects were enhanced either when treating smaller tumors or treating identical tumors with 2 DART wires. Similar experiments on human-derived SCC tumors in nude mice were consistent with the outcomes of the murine model. Histological assessments revealed the tissue damage pattern, and indicated a role for the tumor vasculature in the dispersion of the atoms and the propagation of the damage. Our findings indicate that Diffusing Alpha-emitting Radiation Therapy is effective in a model system using SCC primary tumors. The in situ destruction of primary solid tumors by DART is evidently a necessary step toward curing cancer and might be augmented by chemotherapy and other modalities such as immunotherapy or antigrowth factors agents. PMID:18059026

Cooks, Tomer; Arazi, Lior; Schmidt, Michael; Marshak, Gideon; Kelson, Itzhak; Keisari, Yona

2008-04-01

206

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

Microsoft Academic Search

We present a continuous time\\/discrete space model of biofilm growth, starting from the semi-discrete master equation. The\\u000a probabilities of biomass movement into neighboring sites depend on the local biomass density and on the biomass density in\\u000a the target site such that spatial movement only takes place if (i) locally not enough space is available to accommodate newly\\u000a produced biomass and

Hassan Khassehkhan; Thomas Hillen; Hermann J. Eberl

2009-01-01

207

Escape from cavity through narrow tunnel  

NASA Astrophysics Data System (ADS)

The paper deals with a diffusing particle that escapes from a cavity to the outer world through a narrow cylindrical tunnel. We derive expressions for the Laplace transforms of the particle survival probability, its lifetime probability density, and the mean lifetime. These results show how the quantities of interest depend on the geometric parameters (the cavity volume and the tunnel length and radius) and the particle diffusion coefficients in the cavity and in the tunnel. Earlier suggested expressions for the mean lifetime, which correspond to different escape scenarios, are contained in our result as special cases. In contrast to these expressions, our formula predicts correct asymptotic behavior of the mean lifetime in the absence of the cavity or tunnel. To test the accuracy of our approximate theory we compare the mean lifetime, the lifetime probability density, and the survival probability (the latter two are obtained by inverting their Laplace transforms numerically) with corresponding quantities found by solving numerically the three-dimensional diffusion equation, assuming that the cavity is a sphere and that the particle has the same diffusion coefficient in the cavity and in the tunnel. Comparison shows excellent agreement between the analytical and numerical results over a broad range of the geometric parameters of the problem.

Berezhkovskii, Alexander M.; Barzykin, Alexander V.; Zitserman, Vladimir Yu.

2009-06-01

208

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

SciTech Connect

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

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

1985-11-15

209

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

PubMed Central

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

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

2011-01-01

210

An analysis of the effect of cavity nucleation rate and cavity coalescence on the tensile behavior of superplastic materials  

NASA Astrophysics Data System (ADS)

A model utilizing a simple force-equilibrium approach was developed to establish the effect of the cavity nucleation rate and cavity coalescence on the uniaxial tensile behavior of superplastic metals. All cavities were assumed to be spherical and uniformly distributed within the material, irrespective of the degree of deformation. Material input parameters for the model comprised the cavity nucleation rate ( N), the strain-rate sensitivity of the flow stress ( m), and the growth parameter for individual cavities ( ?), which was taken to be a function of m. The effect of cavity coalescence on average void size and volume fraction was treated using an empirical relation, which correlates an average void growth rate to the growth rate of individual, noninteracting cavities. Model predictions indicated that the macroscopic quantities often used to describe cavitation behavior, i.e., “initial cavity volume fraction” ( C v 0) and “apparent cavity growth rate” ( ? APP) describe the combined influence of cavity nucleation, growth, and coalescence. With regard to the overall tensile behavior, simulation results revealed that increasing cavity nucleation rates reduce ductility in a manner analogous to the effect of decreases in the strain-rate sensitivity. In addition, the failure mode was established with regard to the relative magnitudes of the cavity nucleation rate and the strain-rate sensitivity. Model predictions of tensile elongation and cavity-size distributions were validated by comparison to measurements found in the literature for cavitating superplastic materials.

Nicolaou, P. D.; Semiatin, S. L.; Ghosh, A. K.

2000-05-01

211

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

1997-03-01

212

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

213

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

NASA Astrophysics Data System (ADS)

In the bistable regime of the FitzHugh-Nagumo model of reaction-diffusion systems, spatially homogeneous patterns may be nonlinearly unstable to the formation of compact "localized states." The formation of space-filling patterns from instabilities of such structures is studied in the context of a nonlocal contour dynamics model for the evolution of boundaries between high and low concentrations of the activator. An earlier heuristic derivation [D. M. Petrich and R. E. Goldstein,

Phys. Rev. Lett. 72, 1120 (1994)
] is made more systematic by an asymptotic analysis appropriate to the limits of fast inhibition, sharp activator interfaces, and small asymmetry in the bistable minima. The resulting contour dynamics is temporally local, with the normal component of the velocity involving a local contribution linear in the interface curvature and a nonlocal component having the form of a screened Biot-Savart interaction. The amplitude of the nonlocal interaction is set by the activator-inhibitor coupling and controls the "lateral inhibition" responsible for the destabilization of localized structures such as spots and stripes, and the repulsion of nearby interfaces in the later stages of those instabilities. The phenomenology of pattern formation exhibited by the contour dynamics is consistent with that seen by Lee, McCormick, Ouyang, and Swinney
[Science 261, 192 (1993)]
in experiments on the iodide-ferrocyanide-sulfite reaction in a gel reactor. Extensive numerical studies of the underlying partial differential equations are presented and compared in detail with the contour dynamics. The similarity of these phenomena (and their mathematical description) with those observed in amphiphilic monolayers, type I superconductors in the intermediate state, and magnetic fluids in Hele-Shaw geometry is emphasized.

Goldstein, Raymond E.; Muraki, David J.; Petrich, Dean M.

1996-04-01

214

Diffusion of In atoms in InGaN ultra-thin films during post-growth thermal annealing by high-resolution Rutherford backscattering spectrometry  

NASA Astrophysics Data System (ADS)

Diffusion of In atoms was observed in InGaN ultra-thin films (3 nm thickness), which were prepared by radio-frequency induced nitrogen plasma source MBE (RF-MBE) and subsequent thermal annealing, using high-resolution Rutherford backscattering spectrometry (HRBS). To suppress decomposition of In atoms, cap-GaN layer was grown onto InGaN film. In-related signal clearly appeared in the HRBS spectra after post-growth thermal annealing at 875 °C for 10 min. The thickness of InGaN layer with post-growth thermal annealing increased comparing with that before annealing; On the contrary, the thickness of the cap-GaN layer decreased. This result indicates that diffusion of In atoms occurred at GaN/InGaN interface. The diffusion coefficient is estimated to be approximately 3.8 × 10-18 cm2/s.

Sakuta, H.; Kawano, Y.; Yamanaka, Y.; Kurai, S.; Taguchi, T.

2005-05-01

215

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

PubMed Central

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

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

1994-01-01

216

Characterization and analysis of cavity development during creep of ceramics at elevated temperature. Progress report for 1983  

SciTech Connect

The early stages of creep cavitation in sintered alumina are characterized using small angle neutron scattering (SANS). It is found that the initial cavity density is on the order of 10/sup 11/ cm/sup -3/, and that the average initial pore is aproximately 60 nm in radius. The incubation time for nucleating additional pores during subsequent creep is extremely short, in agreement with theory based on the precipitation of grain-boundary diffusing vacancies. Pore density at constant stress and temperature is a linearly increasing function of time, again as predicted by classical nucleation theory. However, a local stress of 10/sup -2/ E is required to achieve the measured nucleation rate. Cavities are observed to lie primarily on two-grain junctions in linear arrays, with an average cavity radius of approximately 60 nm. It is hypothesized that the cavities nucleate at grain boundary ledges which provide the necessary local stress concentrations. Calculation of the individual cavity growth rate yields a zero or near zero value. This suggests a rapid transient growth period following nucleation which quickly decreases to a negligible growth rate.

Page, R.A.; Lankford, J. Jr.

1983-10-15

217

Characterization and analysis of cavity development during creep of ceramics at elevated temperature. Progress report for 1983  

SciTech Connect

The early stages of creep cavitation in sintered alumina are characterized using small angle neutron scattering (SANS). It is found that the initial cavity density is on the order of 10/sup 11/ cm/sup -3/, and that the average initial pore is approximately 60 nm in radius. The incubation time for nucleating additional pores during subsequent creep is extremely short, in agreement with theory based on the precipitation of grain-boundary diffusing vacancies. Pore density at constant stress and temperature is a linearly increasing function of time, again as predicted by classical nucleation theory. However, a local stress of 10/sup -2/ E is required to achieve the measured nucleation rate. Cavities are observed to lie primarily on two-grain junctions in linear arrays, with an average cavity radius of approximately 60 nm. It is hypothesized that the cavities nucleate at grain boundary ledges which provide the necessary local stress concentrations. Calculation of the individual cavity growth rate yields a zero or near zero value. This suggests a rapid transient growth period following nucleation which quickly decreases to a negligible growth rate.

Page, R.A.; Lankford, J. Jr.

1983-10-15

218

Dual frequency optical cavity  

DOEpatents

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

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

1985-01-01

219

Evaluation of the initial growth of electroless deposited Co(W,P) diffusion barrier thin film for Cu metallization  

SciTech Connect

The formation mechanism of electroless deposited Co(W,P) films is investigated. Co(W,P) films, containing 88-90 at% of Co and 10-12 at% of W and P, are deposited directly onto p-type Si(100) substrate via Pd wet activation. Co(W,P) initially nucleates around Pd activation sites and this is followed by a strong lateral growth. Uniform Co(W,P) thin films can be obtained after 2 min deposition. Fast immersion measurement shows that the mixed potential of Co(W,P) is -0.78 V versus Ag/AgCl electrode. XRD examination shows that the Pd layer has a domination of (111) texture and the principle microstructure of the as-deposited Co(W,P) film is the hcp phase of nano-sized {epsilon}-Co. The inelastic mean free path of diffused Cu in Co(W,P) is determined to be 7.37 A which is significantly smaller than that (9.9 A) in pure Co, indicating that Co(W,P) is a very effective barrier layer. - Graphical abstract: Strong lateral coalescence of Co(W,P) nuclei after 3 s deposition.

Zhu, Aaron [Advanced Materials and Engineering Processing Laboratory (AMPEL), University of British Columbia, 2355 East Mall, Vancouver, British Columbia, V6 T 1Z4 (Canada)]. E-mail: researchman12001@yahoo.com; Shacham-Diamand, Yossi [School of EE, Tel-Aviv University, Ramat-Aviv, 69978 (Israel); School of Applied Chemistry, Waseda University, Shijuku-ku, Toyko 169-8555 (Japan); Teo, Mark [Advanced Materials and Engineering Processing Laboratory (AMPEL), University of British Columbia, 2355 East Mall, Vancouver, British Columbia, V6 T 1Z4 (Canada)

2006-12-15

220

Diffusion and growth of nickel, iron and magnesium adatoms on the aluminum truncated octahedron: A molecular dynamics simulation  

NASA Astrophysics Data System (ADS)

The structure of nickel (Ni), iron (Fe), and magnesium (Mg) adatoms on the aluminum (Al) truncated octahedron is studied using molecular dynamics and the analytic embedded atom method. First, the energy barriers of several typical diffusion processes of Ni, Fe, and Mg adatoms on the Al truncated octahedral cluster were calculated using the nudged elastic band method. The calculated energy barriers were found to be related to the surface energy and atomic radius of the adatom and substrate atom. The result shows that the incorporation of Ni and Fe atoms into Al core easily occurs, and the Mg atom should segregate at the surface of the Al cluster. Thus, the growth of Ni, Fe and Mg on the Al truncated octahedron with 1289 atoms was simulated at several temperatures. In the Ni-Al and Fe-Al cases, the core-shell structure was not obtained. For the Mg-Al system, a good Mg shell on the Al core was found at lower temperatures, and an almost perfect truncated octahedron with more Al shells emerged with an increase in temperature.

Yang, Jianyu; Hu, Wangyu; Wu, Yurong; Dai, Xiongying

2012-06-01

221

Algal morphogenesis: modelling interspecific variation in Micrasterias with reaction--diffusion patterned catalysis of cell surface growth  

PubMed Central

Semi-cell morphogenesis in unicellular desmid algae of the genus Micrasterias generates a stellar shape by repeated dichotomous branching of growing tips of the cell surface. The numerous species of the genus display variations of the branching pattern that differ markedly in number of branchings, lobe width and lobe length. We have modelled this morphogenesis, following previous work by D. M. Harrison and M. Kolar (1988), on the assumptions that patterning occurs by chemical reaction-diffusion activity within the plasma membrane, leading to morphological expression by patterned catalysis of the extension of the cell surface. The latter has been simulated in simplified form by two-dimensional computations. Our results indicate that for generation of repeated branchings and for the control of diverse species-specific shapes, the loss of patterning activity and of rapid growth in regions separating the active growing tips is an essential feature. We believe this conclusion to be much more general than the specific details of our model. We discuss the limitations of the model especially in terms of what extra features might be addressed in three-dimensional computation.

Holloway, D. M.

1999-01-01

222

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

223

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

NASA Astrophysics Data System (ADS)

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 ?m)/Sn(65 ?m)/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 150, 180, and 200°C. The growth of the intermetallic compound (IMC) layer on the Ni side was coupled with that on the Cu side by the mass flux across the Sn layer that was caused by the difference in the Ni content between the (Cu1- x Ni x )6Sn5 layer on the Ni side and the (Cu1- y Ni y )6Sn5 layer on the Cu side. As the consequence of the coupling, the growth rate of the (Cu1- x Ni x )6 Sn5 layer on the Ni side was rapidly accelerated by decreasing Sn layer thickness and increasing aging temperature. Owing to the cross-interaction with the top Ni layer, the growth rate of the (Cu1- y Ni y )6Sn5 layer on the Cu side was accelerated at 150°C and 180°C but was retarded at 200°C, while the growth rate of the Cu3Sn layer was always retarded. The growth kinetic model proposed in an attempt to interpret the experimental results was able to reproduce qualitatively all of the important experimental observations pertaining to the growth of the IMC layers in the Ni/Sn/Cu diffusion couple.

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

2008-01-01

224

Materials Research Related to W-band Cavity Construction.  

National Technical Information Service (NTIS)

Low power rf measurements S11, of electro-discharge machined (EDM) diffusion bonded mm-wave traveling wave rf cavities were not in satisfactory agreement with electromagnetic simulations. During subsequent mechanical inspection, the cell-to-cell iris were...

D. Palmer

2000-01-01

225

Diffusion of In atoms in InGaN ultra-thin films during post-growth thermal annealing by high-resolution Rutherford backscattering spectrometry  

Microsoft Academic Search

Diffusion of In atoms was observed in InGaN ultra-thin films (3 nm thickness), which were prepared by radio-frequency induced nitrogen plasma source MBE (RF-MBE) and subsequent thermal annealing, using high-resolution Rutherford backscattering spectrometry (HRBS). To suppress decomposition of In atoms, cap-GaN layer was grown onto InGaN film. In-related signal clearly appeared in the HRBS spectra after post-growth thermal annealing at

H. Sakuta; Y. Kawano; Y. Yamanaka; S. Kurai; T. Taguchi

2005-01-01

226

Kinetic description of the transition from a one-phase to a two-phase growth regime in Al\\/Pd lateral diffusion couples  

Microsoft Academic Search

The kinetics of the solid-state reaction between Al and Pd is studied in the geometry of a lateral Al-Pd diffusion couple in the temperature range between 250 and 430 °C. The first reaction phase is the crystalline Al3Pd2(?) phase. After the growth of Al3Pd2 reaches a critical length, the quasicrystalline decagonal Al3Pd(?’) phase starts to grow in between the Al

B. Blanpain; J. W. Mayer; Joyce C. Liu; K. N. Tu

1990-01-01

227

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

228

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

PubMed Central

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

2012-01-01

229

The growth and structure of double-diffusive cells adjacent to a cooled sidewall in a salt-stratified environment  

NASA Astrophysics Data System (ADS)

Observations and measurements are reported on the patterns and rates of growth in time of the double-diffusive cells that form adjacent to a cooled sidewall in a saltstratified environment. Fluid near the wall is cooled and sinks a distance h where its density, increased by cooling, matches that of the salt-stratified ambient. The fluid separates from the wall, moving outwards as a cool, fresher layer beneath a warmer, more saline region. This leads to growing double-diffusive cells that advance outward at a rate, found by dimensional reasoning, to initially be proportional to N_{0}h, where N_{0} is the initial buoyancy frequency in the ambient and h is the intrusion's vertical thickness. Near the wall at the top of each cell, the sinking colder fluid is continually replaced by selective withdrawal from the ambient ‘far field’. The fluid being withdrawn from the ambient is always the least dense in the cell, and as the experiment proceeds, the straining of the fluid in the ambient region reduces the stratification. The vertical density gradient inside the cell relaxes by continuous hydrostatic adjustment (CHA) to match the ambient and the speed of advance reduces. Measurements of the rate of advance of the cell nose were made in tanks of different lengths L with a range of initial salinity gradients and temperature differences. A simple two-dimensional model is developed to describe the rate of extension of the cells and the internal density gradient as functions of time in which the tank length appears as an important variable. This effect does not seem to have been recognized previously. The rates of evolution in each run involve the time scale tau {=} L /( {C_H hN_0 }), where C_H {?} 10({) - 2} is a heat transfer coefficient. The mean length of the cells skew2bar {l}(t)and the internal buoyancy frequency as functions of time are given by [ skew2bar {l}(t) / L = t/tau - ( t/2tau)^2,quad N = N_0 (1 - t / 2tau ). ] Inversion of the first of these expressions results in t/tau {=} 2 {-} 2\\{ {1 - (skew2bar {l}(t) / L)}\\}({1) / 2} from which a time scale tau ({) - 1} can be estimated. The measurements from individual runs when plotted in this way generally produce accurate straight lines as the model predicts, from which C_H is found. This should be approximately the same for each run; the mean over all runs was found to be 9.3 {×} 10({) - 3} with standard deviation 2.4 {×} 10({) - 3}. The velocity scale of the intrusions at the beginning of an experiment is of order 10({) - 2} cm s(-1) , for typical parameters of water at temperature 20 (°) C, cooled wall temperature of 0 (°) C and mean salinity of 5%.

Malki-Epshtein, Liora; Phillips, Owen M.; Huppert, Herbert E.

2004-11-01

230

Dual Microwave Cavity Accelerometer.  

National Technical Information Service (NTIS)

A system and method for compensating for gradients in a dual cavity device such as but not limited to an accelerometer. A first source drives a first cavity at least two different modes, at least one mode varying with changes in cavity length. A second so...

A. Petrovich J. A. Bickford M. S. Weinberg

2003-01-01

231

Partial Cavity Drag Reduction  

Microsoft Academic Search

The notion of using air to reduce a ship's frictional drag dates back to the 19^th century. Bubbles, air layers and air filled cavities have been proposed, but there has been little systematic research published. To address this, partial cavity drag reduction experiments were carried out at the W. B. Morgan Large Cavitation Channel. The partial cavity was investigated at

Simo Makiharju; Keary Lay; Ryo Yakushiji; Marc Perlin; Steven Ceccio

2008-01-01

232

Diffusion of interacting particles in discrete geometries.  

PubMed

We evaluate the self-diffusion and transport diffusion of interacting particles in a discrete geometry consisting of a linear chain of cavities, with interactions within a cavity described by a free-energy function. Exact analytical expressions are obtained in the absence of correlations, showing that the self-diffusion can exceed the transport diffusion if the free-energy function is concave. The effect of correlations is elucidated by comparison with numerical results. Quantitative agreement is obtained with recent experimental data for diffusion in a nanoporous zeolitic imidazolate framework material, ZIF-8. PMID:24074065

Becker, T; Nelissen, K; Cleuren, B; Partoens, B; Van den Broeck, C

2013-09-11

233

A numerical simulation study for the combined effect of static and rotating magnetic fields in liquid phase diffusion growth of SiGe  

NASA Astrophysics Data System (ADS)

The article presents the results of a numerical simulation study conducted to examine the combined effect of static and rotating magnetic fields on the liquid phase diffusion (LPD) growth process of SiGe single crystals. The simulation results indicate that the combined use of static and rotating magnetic fields is more effective than using either a static or rotating field alone. The application of a combined field does not only suppress natural convection but also leads to better mixing in the solution and flatter growth interfaces. For the system considered here, the application of a static field of 0.3 T and a rotating field of 4.0 or 5.0 mT makes the growth interface almost flat.

Yildiz, E.; Dost, S.

2007-05-01

234

Experimental investigation of a chemical-laser-cavity flowfield. Master's thesis  

Microsoft Academic Search

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold air as the working medium, the flow control system configuration and nozzle-cavity-supersonic diffuser assembly configuration were developed to establish acceptable flow

Stiglich

1989-01-01

235

A general cavity theory  

NASA Astrophysics Data System (ADS)

A cavity theory is used to relate the dose deposited in the cavity (sensitive volume of the detector) to that in the surrounding medium which may be of different atomic number or composition. Burlin proposed a general cavity theory to include all cavity sizes. The Burlin theory ignores all secondary-electron scattering effects which results in large discrepancies in dose to the cavity compared with the experimental results in high atomic number media. Kearsley proposed a new general cavity theory which includes secondary-electron scattering at the cavity boundary. The Kearsley theory showed excellent agreement with experimental results for -rays but poor correlation for 10 MV x-rays. The Kearsley theory has numerous parameters and the magnitude of the input parameters is arbitrary; therefore the dose to the cavity depends on the choice of parameters. We have developed a new cavity theory which includes secondary-electron backscattering from the medium into the cavity. The strengths of this proposed theory are that it contains few parameters and a methodical way of determining the magnitude of the parameters experimentally. The proposed theory gives better agreement with experimental results in lithium fluoride thermoluminescence dosimeters for -rays and 10 MV x-rays in aluminium, copper and lead than do the Burlin and Kearsley cavity theories.

Haider, Jacob Abraham; Skarsgard, Lloyd D.; Lam, Gabriel K. Y.

1997-03-01

236

Beam-Cavity Interaction Circuit at W-Band  

SciTech Connect

We describe the design, fabrication and bench-study of a mm-wave cavity employed as a relativistic klystron output structure. The OFE copper cavity was prepared by electro-discharge machining and diffusion bonding, cleaned, and tuned to 91.4 GHz. Measured cavity characteristics are presented and compared with theory, including quality factor, Q, coupling parameter {beta}, scattering matrix S{sub 11}, and axial electric field profile E{sub z}. This work provides the basis for understanding of the cavity as a transfer structure.

Hill, Marc E

1999-07-14

237

Effects of Y2O3 additions on the oxygen diffusion in top-seeded melt growth processed YBa2Cu3O7-y superconductors  

NASA Astrophysics Data System (ADS)

To understand the effect of Y2BaCuO5 (Y211)/YBa2Cu3O7-y (Y123) interfaces on the oxygen diffusion in single grain YBa2Cu3O7-y superconductors, single grain Y123 superconductors with 0.05 and 0.3 moles of Y2O3 additions were fabricated by a top-seeded melt growth (TSMG) process. Y123 compacts with Y2O3 additions were subjected to melt growth heating cycles with a cooling rate of 1 °C/h through a peritectic temperature (1015 °C) and then annealed at 450 °C for 200 h in flowing oxygen. The superconducting temperature (Tc) and critical current density (Jc) were estimated for the three different regions (top surface (s), intermediate (i) and center (c)) of samples. The amount of Y211/Y123 interface area in single grain Y123 superconductors was successfully controlled by Y2O3 additions. The Tc values of s regions were higher than those of i and c regions, which indicates the presence of more oxygen at the sample surfaces. In addition, the Tc values of i and c regions of the Y123 sample with 0.3 mole Y2O3 addition were higher than those of the same regions of the Y123 sample with 0.05 mole Y2O3 addition due to the promoted oxygen diffusion through Y211/Y123 interfaces and other related defects. In spite of the promoted oxygen diffusion by Y2O3 addition, the large Tc difference among the regions still existed, which suggests sluggish oxygen diffusion into single Y123 grains.

Jun, B.-H.; Jung, S.-A.; Park, S.-D.; Park, B. J.; Han, Y. H.; Kim, C.-J.

2011-11-01

238

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

PubMed

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

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

2007-05-30

239

The effect of several endocrine factors on the growth of ventral sebaceous gland of Rhombomys opimus (Rodentia, Mammalia) in diffusion chambers.  

PubMed

The growth of cells of ventral sebaceous gland of Rhombomys opimus was studied in diffusion chambers. The surface properties of these cells and intercellular contacts have been examined in the scanning electron microscope. After 10 to 12 days of cultivation the cells formed aggregates showing a recognizable histological pattern (the ventral sebaceous gland). The pituitary and ovarian gland explants had a significant effect on the differentiation and mitotic activity of epithelial cells of the ventral sebaceous gland. Apparently it is the cell surface itself that alters during the active processes of secretion and differentiation. PMID:7148261

Sokolov, V E; Evgenjeva, T P

1982-01-01

240

A numerical simulation study for the effect of magnetic fields in liquid phase diffusion growth of SiGe single crystals  

NASA Astrophysics Data System (ADS)

The article presents the results of a numerical simulation study conducted to examine the effect of static and rotating magnetic fields on the growth process of SiGe single crystals by liquid phase diffusion (LPD). A three-dimensional transient numerical simulation model was developed to observe the heat, mass, and momentum transfer characteristics of the SiGe solution. Simulation results indicate that the use of a static, vertical magnetic field in this growth setup is effective in suppressing natural convection in the solution. A stationary field intensity of 0.3 T is sufficient to provide significant suppression, above which the flow becomes numerically unstable. However, the vertical magnetic field does not provide the expected flattening in the growth interface. In the case of a rotating magnetic field (RMF), results show that the use of RMF is effective in providing sufficient mixing in the melt leading to more homogeneous SiGe crystals. In addition, RMF is also very beneficial for flattening the growth interface. At the 3.0 mT a RMF intensity level, the growth interface becomes almost flat.

Yildiz, E.; Dost, S.; Yildiz, M.

2006-06-01

241

Electromagnetic SCRF Cavity Tuner  

SciTech Connect

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

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

2009-05-01

242

Chronic upregulation of activated microglia immunoreactive for galectin-3\\/Mac2 and nerve growth factor following diffuse axonal injury  

Microsoft Academic Search

BACKGROUND: Diffuse axonal injury in patients with traumatic brain injury (TBI) can be associated with morbidity ranging from cognitive difficulties to coma. Magnetic resonance imaging scans now allow early detection of axonal injury following TBI, and have linked cognitive disability in these patients to white matter signal changes. However, little is known about the pathophysiology of this white matter injury,

Charu Venkatesan; MaryAnn Chrzaszcz; Nicole Choi; Mark S Wainwright

2010-01-01

243

Measurements of Silica Aggregate Particle Growth Using Light Scattering and Thermophoretic Sampling in a Coflow Diffusion Flame  

Microsoft Academic Search

The evolution of silica aggregate particles in a coflow diffusion flame has been studied experimentally using light scattering and thermophoretic sampling techniques. An attempt has been made to calculate the aggregate number density and volume fraction using the measurements of scattering cross section from 90° light scattering with combination of measuring the particle size and morphology from the localized sampling

M. Choi; J. Cho; J. Lee; H. W. Kim

1999-01-01

244

Cavity resonator filter structure having improved cavity arrangement  

US Patent & Trademark Office Database

A combined resonator-cavity filter includes a number of cavity structures designed for cooperative arrangement within a housing. The resonator cavities are constructed and arranged to pass energy in an assigned frequency band. The cavities include a first cavity structure having a corresponding cavity volume and constructed to provide a first Q, and a second cavity structure having its corresponding cavity volume and constructed to provide a second Q. The cavity volume corresponding to the second cavity structure is less than the cavity volume corresponding to the first cavity structure. Other aspects are directed to the arrangement and uses of sets of such cavity structures as part of a combined duplexer-receiver having the same housing.

1999-04-13

245

Integrated external cavity laser  

SciTech Connect

The fabrication and performance characteristics of single frequency integrated external cavity lasers of the coupled cavity type and the distributed Bragg reflector type are described. The active cavity section of these devices utilizes the double channel planar buried heterostructure scheme for current confinement. The lasers emit near 1.55 ..mu..m. The threshold current of these lasers is in the range 70--120 mA. cw linewidth of 7 MHz has been obtained for a 2-mm-long laser at an output power of 3 mW. We believe lasers with longer external cavity should exhibit lower cw linewidths.

Dutta, N.K.; Cella, T.; Piccirilli, A.B.; Brown, R.L.

1986-11-10

246

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

Microsoft Academic Search

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

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

2006-01-01

247

Flow and fracturing of viscoelastic media under diffusion-driven bubble growth: An analogue experiment for eruptive volcanic conduits  

Microsoft Academic Search

To visualize the behavior of erupting magma in volcanic conduits, we performed shock tube experiments on the ductile–brittle response of a viscoelastic medium to diffusion-driven bubble expansion. A sample of shear-thinning magma analogue is saturated by gas Ar under high pressure. On rapid decompression, Ar supersaturation causes bubbles to nucleate, grow, and coalesce in the sample, forcing it to expand,

J. Taddeucci; O. Spieler; M. Ichihara; D. B. Dingwell; P. Scarlato

2006-01-01

248

Mesocotyl growth of etiolated seedlings of Avena sativa and Zea mays in relation to light and diffusible auxin  

Microsoft Academic Search

Diffusible auxin levels were measured in coleoptiles and mesocotyls of dark-grown seedlings ofavena sativa (cv. Spear) andZea mays (cv. Golden Cross Bantam) using theAvena curvature bioassay. The coleoptile tip was confirmed as the major auxin source in etiolated seedlings. Auxin levels were\\u000a found to decrease basipetally in sequent sections of theAvena coleoptile but not to decrease in apical sections of

R. W. Kessler; L. S. Gerhold; R. M. Muir

1985-01-01

249

Simultaneous growth of a crystalline phase and a quasicrystalline phase in lateral Al–Pd diffusion couples  

Microsoft Academic Search

The solid-state reaction between Al and Pd is studied in a lateral Al–Pd diffusion couple in the temperature range between 250°C and 430°C. The first reaction phase is the crystalline Al3Pd2 phase. After this phase reaches a critical length of around 6 ?m, the quasicrystalline decagonal Al3Pd phase starts to grow in between the Al and the Al3Pd2 phases. After

B. Blanpain; J. C. Liu; D. A. Lilienfeld; J. W. Mayer

1990-01-01

250

Thermally stabilized laser cavity  

SciTech Connect

This patent describes a temperature stabilized laser cavity support structure comprising: at least two heat pipes functioning as structural elements in a laser cavity; and thermal stabilization means attached to all the heat pipes and furnishing a heat transfer path between them to maintain the heat pipes at essentially the same temperature.

Eastman, G.Y.

1987-09-22

251

Partial Cavity Drag Reduction  

NASA Astrophysics Data System (ADS)

The notion of using air to reduce a ship's frictional drag dates back to the 19^th century. Bubbles, air layers and air filled cavities have been proposed, but there has been little systematic research published. To address this, partial cavity drag reduction experiments were carried out at the W. B. Morgan Large Cavitation Channel. The partial cavity was investigated at Reynolds numbers to 70 million and stable cavities with frictional drag reduction of more than 95% were attained. The model used was a 3 m wide and 12 m long flat plate with a plenum on the bottom. The design of the cavity was based on both linear gravity wave theory and two-dimensional inviscid numerical calculations. To create the partial cavity, air was injected at the base of an 18 cm backwards facing step 1.5 m from the nose of the plate. Frictional loads, free stream speed, air flow and cavity pressures were measured over a range of flow speeds and air fluxes. High speed video was used to investigate the unsteady three dimensional cavity closure. Cloud shedding, similar to sheet-cloud cavitation shedding with natural cavitation on hydrofoils, was observed at the closure.

Makiharju, Simo; Lay, Keary; Yakushiji, Ryo; Perlin, Marc; Ceccio, Steven

2008-11-01

252

Teratocarcinosarcoma of the oral cavity.  

PubMed

Teratocarcinosarcoma (TCS) is a very rare and aggressive neoplasm characterized by teratoma and carcinosarcoma components. The authors report on a case of TCS in the oral cavity of a child. Rapid growth and extensive local destruction were prominent features prior to treatment. Histologic examination revealed various tissue elements, such as epithelial, mesenchymal, and neuroectodermal components. Chemotherapy was effective in reducing tumor mass, followed by partial anterior mandibulectomy and reconstruction with composite microvascular tissue transfer. The approach allowed radical resection of the tumor and functional reconstruction with excellent aesthetic results. PMID:15390296

Crazzolara, Roman; Puelacher, Wolfgang; Ninkovic, Milomir; Zelger, Bettina; Buchberger, Wolfgang; Meister, Bernhard; Zimmerhackl, Lothar B; Klein-Franke, Andreas

2004-11-01

253

CAVITY EXCITATION CIRCUIT  

DOEpatents

An electronic oscillator is described for energizing a resonant cavity and to a system for stabilizing the operatin g frequency of the oscillator at the particular frequency necessary to establish a particular preferred field configuration or mode in the cavity, in this instance a linear accelerator. A freely rnnning oscillator has an output coupled to a resonant cavity wherein a field may be built up at any one of several adjacent frequencies. A pickup loop in the cavity is suitably shielded and positioned in the cavity so that only energy at the panticular desired frequency is fed back to stabilize the oscillator. A phase and gain control is in cluded in the feedback line.

Franck, J.V.

1959-10-20

254

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

Microsoft Academic Search

Organisms are expected to balance energy allocation in such a way that fitness is maximized. While much research has focussed\\u000a on allocation strategies of reproducing parents, in particular birds, relatively little attention has been paid to how nestlings\\u000a allocate energy while in the nest. Nestling birds are faced with a trade-off between devoting energy to growth or to thermoregulation,\\u000a and

Russell D. Dawson; Cheyenne C. Lawrie; Erin L. O’Brien

2005-01-01

255

The effects of HCl on silicon nanowire growth: surface chlorination and existence of a 'diffusion-limited minimum diameter'.  

PubMed

Silicon nanowires were grown by chemical vapour deposition on gold catalysts using SiH4 and HCl diluted in H2. The effects of HCl on the wires and the catalysts were investigated for various HCl partial pressures. Keeping all other parameters constant, gold migration on the silicon surface is found to be dramatically reduced by the surface chlorination induced by HCl. We then use HCl to control gold migration and show the existence of a 'diffusion-limited minimum diameter'. This diameter limit arises from the surface migration kinetics and it sets a lower bound on the wire diameter distribution. PMID:19875870

Oehler, F; Gentile, P; Baron, T; Ferret, P

2009-10-29

256

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

NASA Astrophysics Data System (ADS)

Metals exposed to ultrafast laser irradiation close to ablative regimes show often a submicron-scale (near 0.5 ?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.

2012-01-01

257

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

258

Homeostatic Role of Transforming Growth Factor-? in the Oral Cavity and Esophagus of Mice and Its Expression by Mast Cells in These Tissues  

PubMed Central

Transforming growth factor-? (TGF-?) is a pleiotropic growth factor; its overexpression has been implicated in many diseases, making it a desirable target for therapeutic neutralization. In initial safety studies, mice were chronically treated (three times per week) with high doses (50 mg/kg) of a murine, pan-neutralizing, anti-TGF-? antibody. Nine weeks after the initiation of treatment, a subset of mice exhibited weight loss that was concurrent with decreased food intake. Histopathology revealed a unique, nonneoplastic cystic epithelial hyperplasia and tongue inflammation, as well as dental dysplasia and epithelial hyperplasia and inflammation of both the gingiva and esophagus. In an effort to determine the cause of this site-specific pathology, we examined TGF-? expression in these tissues and saliva under normal conditions. By immunostaining, we found higher expression levels of active TGF-?1 and TGF-?3 in normal tongue and esophageal submucosa compared with gut mucosal tissues, as well as detectable TGF-?1 in normal saliva by Western blot analysis. Interestingly, mast cells within the tongue, esophagus, and skin co-localized predominantly with the TGF-?1 expressed in these tissues. Our findings demonstrate a novel and restricted pathology in oral and esophageal tissues of mice chronically treated with anti-TGF-? that is associated with basal TGF-? expression in saliva and by mast cells within these tissues. These studies illustrate a previously unappreciated biological role of TGF-? in maintaining homeostasis within both oral and esophageal tissues.

Vitsky, Allison; Waire, James; Pawliuk, Robert; Bond, Arden; Matthews, Douglas; LaCasse, Emily; Hawes, Michael L.; Nelson, Carol; Richards, Susan; Piepenhagen, Peter A.; Garman, Richard D.; Andrews, Laura; Thurberg, Beth L.; Lonning, Scott; Ledbetter, Steve; Ruzek, Melanie C.

2009-01-01

259

The effects of electrical fields on growth of titania particles formed in a CH 4–O 2 diffusion flame  

Microsoft Academic Search

The effects of a DC electric field on the growth processes of titania particles formed in a premixed CH4–O2 flame were investigated for three basic types of electrode geometry, namely pairs of needle tips, spheres and plates. The conclusions are based on measurements of the primary particle diameter, agglomerate mobility distribution and fractal dimension, agglomerate charge distribution, as well as

M. Katzer; A. P. Weber; G. Kasper

2001-01-01

260

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.

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

2013-01-01

261

Marangoni Flows in Open Cavities with Differentially Heated End Walls.  

National Technical Information Service (NTIS)

Surface tension driven flows, induced by imposed temperature differences, in plane cavities with differentially heated end walls are considered. This configuration is connected to processes of crystal growth from melt by the open boat horizontal technique...

C. Golia A. Viviani D. Castagnolo

1992-01-01

262

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

263

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

264

Experimental investigation of a chemical laser cavity flowfield  

NASA Astrophysics Data System (ADS)

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold air as the working medium, the flow control system configuration and nozzle-cavity-supersonic diffuser assembly configuration were developed to establish acceptable flow conditions in the test section. Performance evaluation was based on pressure measurements in the nozzle-cavity-diffuser assembly and schlieren photographs of the flowfield in the cavity. Flow conditions in the test section were broken up into three different regions: flow in the hypersonic nozzles, flow in the base region and flow in the cavity region. Flow in the nozzles was analyzed using one-dimensional, steady, isentropic flow theory. Test results indicated that the hypersonic nozzles performed to design specifications. The Korst two-dimensional base-pressure flow model was used to describe the flow in the nozzle exit plane and base region. Experimentally calculated Mach numbers and static pressures corresponded very closely to theoretical values. Static pressure ports and schlieren photographs were used to describe the flow-field conditions in the cavity region.

Stiglich, Stephen Walter, Jr.

1989-12-01

265

Adaptive control of axisymmetric jets by cavities  

NASA Astrophysics Data System (ADS)

Actuators capable of producing large amplitude oscillations at desired frequencies are needed in many flow control applications. In this dissertation, turbulent jets were actuated using self-sustaining oscillations in axisymmetric cavities. Measurements on baseline turbulent jets showed that the near field coherent structures and their residence time are two important factors that could be manipulated to influence the initial growth rate of a jet. Frequency of oscillation of the pressure field within the cavity was primarily dependent on the length scale (length to depth ratio and the pipe diameter) of the cavity and the Mach number of the flow. Axisymmetric cavities with cavity length to depth ratio 1.5--2.0, preferably 1.75, placed immediately after the exit of the jet exhibited a resonant condition (between the axial shallow cavity mode and the radial acoustic mode of the pipe) with very high amplitude oscillations (in excess of 180 dB within the cavity) at moderate to high Reynolds number range of this study. Comparison with baseline jets based on centerline velocity decay and lateral jet spread rate showed that mixing characteristics had improved significantly. The potential core length (location of 90% jet exit velocity) for the best case was at 1D as compared to 5D for the baseline jet. Ensemble averages of different phases of an oscillation cycle (along the jet flow direction and in the cross-section) were used to recreate the oscillation cycle (flow visualization images, velocity and vorticity fields) and study the flow structures in the near field. Mode of oscillation (axial/helical) of the jet exiting the cavity was found to be dependent on the inlet and exit boundary conditions of the cavity. Cavities with sharp orifices at the inlet and exit boundaries had complex helical mode structures in the near field of the jet. When the exit boundary of the cavity had a short pipe instead of a sharp orifice, only axial mode vortex rings remained in the near field. However the jet entrainment was not as high, as in the case of sharp orifices.

Meganathan, Abraham Joseph

266

Visualization of Hydrogen Diffusion in a Hydrogen-Enhanced Fatigue Crack Growth in Type 304 Stainless Steel  

Microsoft Academic Search

To study the influence of hydrogen on the fatigue strength of AISI type 304 metastable austenitic stainless steel, specimens\\u000a were cathodically charged with hydrogen. Using tension-compression fatigue tests, the behavior of fatigue crack growth from\\u000a a small drill hole in the hydrogen-charged specimen was compared with that of noncharged specimen. Hydrogen charging led to\\u000a a marked increase in the crack

Hisao Matsunaga; Hiroshi Noda

2011-01-01

267

Modelling and fabrication of GaAs photonic-crystal cavities for cavity quantum electrodynamics.  

PubMed

In this paper, we present recent progress in the growth, modelling, fabrication and characterization of gallium arsenide (GaAs) two-dimensional (2D) photonic-crystal slab cavities with embedded indium arsenide (InAs) quantum dots (QDs) that are designed for cavity quantum electrodynamics (cQED) experiments. Photonic-crystal modelling and device fabrication are discussed, followed by a detailed discussion of different failure modes that lead to photon loss. It is found that, along with errors introduced during fabrication, other significant factors such as the presence of a bottom substrate and cavity axis orientation with respect to the crystal axis, can influence the cavity quality factor (Q). A useful diagnostic tool in the form of contour finite-difference time domain (FDTD) is employed to analyse device performance. PMID:20057040

Khankhoje, U K; Kim, S-H; Richards, B C; Hendrickson, J; Sweet, J; Olitzky, J D; Khitrova, G; Gibbs, H M; Scherer, A

2010-01-08

268

Lymphatic Vessel Density and Vascular Endothelial Growth Factor Expression in Squamous Cell Carcinomas of Lip and Oral Cavity: A Clinicopathological Analysis with Immunohistochemistry Using Antibodies to D2-40, VEGF-C and VEGF-D  

PubMed Central

Background Squamous cell carcinoma (SCC) of the oral region often metastasizes to the cervical lymph nodes. To investigate whether the risk of cervical lymph node metastasis are predictable through lymphatic vessel density (LVD) and vascular endothelial growth factor (VEGF) expression, we assessed the relationship between LVD and clinicopathological parameters, and VEGF expression in SCC of the oral region. Methods The subjects were 109 patients with SCC of the oral region including the lip. Clinicopathological parameters examined for the association with LVD in a peritumoral hot spot were lymph node metastasis, histological grade and disease stage. The association with VEGF expression was similarly studied. LVD was detected by immunohistochemistry using D2-40. Results LVD was significantly higher in lip cancer than in other oral tumors (P < 0.0001), while there were no significant differences of LVD among other cancers of the oral cavity. LVD tended to decrease with disease progression, increase of tumor size and increase of metastatic lymph node size. Eighty-four of 109 tumors were positive for VEGF-C or D. VEGF-C-positive tumor lesions were also positive for VEGF-D. Significantly higher levels of VEGF-C and D expressions were associated with large size of lymph node metastases (P = 0.02). Conclusion SCC of the oral region including the lip that produces VEGF-C and D is significantly more likely to cause cervical lymph node metastasis. LVD in a peritumoral hot spot does not directly indicate the risk of cervical lymph node metastasis, but instead may reflect lymphangiogenesis due to VEGF together with loss of lymphatic vessels through tumor growth and progression.

Watanabe, Soh; Kato, Masako; Kotani, Isamu; Ryoke, Kazuo; Hayashi, Kazuhiko

2013-01-01

269

Growth  

Microsoft Academic Search

\\u000a This chapter is devoted to the growth of ZnO. It starts with various techniques to grow bulk samples and presents in some\\u000a detail the growth of epitaxial layers by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and\\u000a pulsed laser deposition (PLD). The last section is devoted to the growth of nanorods. Some properties of the resulting samples

Andreas Waag

2010-01-01

270

Diffusion-controlled growth of molecular heterostructures: fabrication of two-, one-, and zero-dimensional c60 nanostructures on pentacene substrates.  

PubMed

A variety of low dimensional C60 structures has been grown on supporting pentacene multilayers. By choice of substrate temperature during growth the effective diffusion length of evaporated fullerenes and their nucleation at terraces or step edges can be precisely controlled. AFM and SEM measurements show that this enables the fabrication of either 2D adlayers or solely 1D chains decorating substrate steps, while at elevated growth temperature continuous wetting of step edges is prohibited and instead the formation of separated C60 clusters pinned at the pentacene step edges occurs. Remarkably, all structures remain thermally stable at room temperature once they are formed. In addition the various fullerene structures have been overgrown by an additional pentacene capping layer. Utilizing the different probe depth of XRD and NEXAFS, we found that no contiguous pentacene film is formed on the 2D C60 structure, whereas an encapsulation of the 1D and 0D structures with uniformly upright oriented pentacene is achieved, hence allowing the fabrication of low dimensional buried organic heterostructures. PMID:24004066

Breuer, Tobias; Witte, Gregor

2013-09-19

271

Coupled resonator vertical cavity laser  

SciTech Connect

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

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

1998-01-01

272

The insulin-like growth factor-system in a patient with diffuse large B-cell non-Hodgkin's lymphoma and lactic acidosis.  

PubMed

Lactic acidosis is a rare complication of haematological malignancies with a poor prognostic outcome and unclear aetiology. Possible mechanisms include high rate of glycolysis by cancer cells, in part due to over-expression of hexokinase II. The insulin-like growth factor (IGF)-system has an important role in normal as well as tumour cell growth. We present a case of a 79-year-old man with a diffuse large B-cell lymphoma and lactic acidosis. Initially, the patient was successfully treated according to the R-CHOP scheme. After recurrence of disease, the patient was treated according to a protocol of the Dutch-Belgian Haemato-Oncology Group (HOVON-85 study). Eleven months after completion of the last therapy, the patient still appeared to be in complete remission. Serum levels of IGFs, pro-IGF-IIE[68-88], IGF binding proteins (IGFBPs)-1 to -4, acid labile subunit (ALS), as well as ternary IGF-I-IGFBP-3-ALS complex formation, were determined in samples taken before, during and after treatment, respectively. Before treatment patient's serum concentration of the growth hormone-dependent parameters of the IGF-system and IGF-II were clearly reduced when compared with patient's values during remission of disease. On the other hand, during acidosis a relatively higher proportion of IGFs is present in binary complexes, instead of 150 kDa complexes, that may allow an increased access of IGFs to target cells including the malignant ones. Pretreatment serum levels of IGFBP-1 and -2 were elevated, decreased during therapy and normalized at remission. Especially IGFBP-2 seems a suitable marker for disease activity. PMID:23467067

Hoogwerf, Demelza; van Doorn, Jaap; Maartense, Eduard

2013-03-06

273

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

PubMed

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

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

2013-02-04

274

Erbium diffusion in silicon dioxide  

SciTech Connect

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

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

2010-10-04

275

Study of air-ventilated cavity under model hull on water surface  

Microsoft Academic Search

The use of air cavities beneath ship hulls can lead to significant drag reduction. A study of air-ventilated cavities under a simplified hull has been undertaken. Experiments with a 56-cm-long stepped-hull model were carried in an open-surface water channel at flow velocities 28–86cm\\/s. The air-cavity parameters were measured at different model positions. Different cavity forms, a strong growth of the

Konstantin I. Matveev; Tyrel J. Burnett; Alex E. Ockfen

2009-01-01

276

Diffuse large B-cell lymphoma with Homer-Wright rosettes, sinusoidal growth pattern, and CD30 expression: a possible overlap between microvillous lymphomas and sinusoidal CD30-positive large B-cell lymphomas.  

PubMed

Rosette formation is an unusual finding in malignant lymphomas. We herein report another case of a diffuse large B-cell lymphoma (DLBCL) with ultrastructural evidence of cellular projections, sinusoidal growth pattern, and strong CD30 expression. A literature review of the DLBCL cases showing all these features was also performed. PMID:19059735

Goteri, Gaia; Costagliola, Antonello; Tassetti, Angela; Stramazzotti, Daniela; Morroni, Manrico; Rupoli, Serena; Centurioni, Riccardo; Leoni, Pietro

2008-12-06

277

Reaction-diffusion processes with nonlinear diffusion.  

PubMed

We study reaction-diffusion processes with concentration-dependent diffusivity. First, the decay of the concentration in the single-species and two-species diffusion-controlled annihilation processes is determined. We then consider two natural inhomogeneous realizations. The two-species annihilation process is investigated in the situation when the reactants are initially separated, namely each species occupies a half space. In particular, we establish the growth law of the width of the reaction zone. The single-species annihilation process is studied in the situation when the spatially localized source drives the system toward the nonequilibrium steady state. Finally, we investigate a dissolution process with a localized source of diffusing atoms which react with the initially present immobile atoms forming immobile molecules. PMID:23214535

Krapivsky, P L

2012-10-09

278

Axial flow laser cavity  

SciTech Connect

An improved gaseous laser device is provided which comprises a generally tubular laser discharge tube having a laser window at each end thereof, each window disposed at an angle to the lasing asis of the device corresponding substantially the the Brewster's angle characteristic of the material comprising the windows, and including means directing substantially uniform flow of gaseous laser medium into and out of the discharge tube substantially at said angle and means providing a choked gaseous exhaust exit for canceling cavity distrubances within the device. Laser optics defining an optical resonant cavity of the laser device may be disposed external of the discharge tube and windows.

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

1984-11-13

279

Analog cavity simulator  

NASA Astrophysics Data System (ADS)

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

Orel, Peter; Mavri?, Uroš

2013-11-01

280

Underground-coal-gasification cavity simulator with solid motion  

SciTech Connect

The prediction of cavity growth and product composition have long been major goals in the development of underground coal gasification (UCG). Lawrence Livermore National Laboratory (LLNL) is developing a UCG cavity growth model which incorporates many of the key features observed during our recent large block (LBK) tests conducted at the WIDCo mine at Centralia, Washington, in which early cavity growth and product yield were studied. Postburn excavation following the tests revealed oval-shaped, rubble-filled cavities with significant void space under the cavity roof. The bottom portion of the cavity contained ash and slag, with an overlying rubble region of coal, char, and ash. A void space existed between the rubble pile and the cavity roof which was generally flat with square corners, a result of the apparent breaking away and falling in of the roof material. In this paper, basic features of the model are described and a number of preliminary runs are documented. These runs include matching of the LBK data, studies of sensitivity to variations in model parameters and operational parameters, and calculations of possible performance of the upcoming Centralia partial-seam CRIP test.

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

1983-06-01

281

The magnetic and fluid environment of an ellipsoidal circumstellar plasma cavity  

Microsoft Academic Search

The contact discontinuity surface separating a stellar wind cavity from the external magnetized and ionized interstellar plasma, or astropause, is modelled by a triaxial ellipsoid. It is argued that such a surface is likely to be closed due to the fact that the stellar wind plasma leaves the inner cavity via diffusion along the strong magnetic field gradients in the

W. Neutsch; H. J. Fahr

1982-01-01

282

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

283

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

284

Solute segregation in a lid driven cavity: Effect of the flow on the boundary layer thickness and solute segregation  

NASA Astrophysics Data System (ADS)

Our objective in the present work is to study the effect of convective flows, ranging from laminar to fully turbulent, on solute segregation in directional solidification configurations. To do so, numerical simulations performed in a model 2D lid driven cavity; the problem parameters, apart from the species molecular diffusion coefficient, are the lid and growth velocities. Purely diffusive to fully convective mass transport conditions are modelled in our parametric study. In parallel, a scaling analysis aiming at the determination of the solute boundary layer thickness is proposed. The results show that a single non-dimensional number, based on the interface stress, is able to capture the physics of the solute transport phenomena.

Garandet, J. P.; Kaupp, N.; Pelletier, D.; Delannoy, Y.

2012-02-01

285

The differentially heated cavity  

Microsoft Academic Search

This review discusses recent work dealing with natural convection flow in a differentially heated cavity. The emphasis is\\u000a placed primarily on work dealing with the non-Boussinesq regime, transitional flow, and turbulent flow. Direction for future\\u000a work in areas where additional effort is required is also provided.

S Paolucci

1994-01-01

286

Cavity ringdown strain gauge  

Microsoft Academic Search

require expensive and sophisticated signal acquisition systems. Cavity ringdown spectroscopy, a technique commonly applied to high-sensitivity chemical analysis, offers detection sensitivity advantages that can be used to improve strain measurement with biconical tapers. Combining these two technologies in a spatially extended resonator, we demonstrate a minimum detectable change in ringdown time of 0.08%, corresponding to a minimum detectable displacement of

Peter B. Tarsa; Diane M. Brzozowski; Paul Rabinowitz; Kevin K. Lehmann

2004-01-01

287

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

288

Complementary IL-23 and IL-27 anti-tumor activities cause strong inhibition of human follicular and diffuse large B-cell lymphoma growth in vivo.  

PubMed

Interleukin (IL)-23 and IL-27 are pro-inflammatory cytokines that share functional and structural similarities and may exert anti-tumor activities against solid and hematological malignancies. Here, we asked whether IL-23 and IL-27, alone or in combination, may act directly against human follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) cells. In this study, we demonstrated for the first time that human primary FL and DLBCL cells expressed complete and functional IL-23 and IL-27 receptors (R) and that IL-23 and IL-27 exerted anti-tumor activities in vitro and in vivo through different and complementary mechanisms. In vivo studies using severe combined immunodeficiency /non-obese diabetic mice-injected subcutaneously with human SU-DHL-4 cell line revealed that IL-23 inhibited directly tumor-cell proliferation, whereas IL-27 impaired the angiogenic program of lymphoma cells resulting in strong reduction of cell growth. In addition, combined treatment of IL-23 and IL-27 amplified the anti-tumor effects in vivo as compared with administration of each cytokine alone. These anti-tumor mechanisms were confirmed by in vitro experiments performed with primary lymphoma cells and cell lines. Our results strongly encourage the development of future clinical trials to evaluate the toxicity and efficacy of the IL-23 and IL-27 in lymphoma patients. PMID:22193967

Cocco, C; Di Carlo, E; Zupo, S; Canale, S; Zorzoli, A; Ribatti, D; Morandi, F; Ognio, E; Airoldi, I

2011-12-23

289

Prognostic significance of hypoxia inducible factor-1? and vascular endothelial growth factor expression in patients with diffuse large B-cell lymphoma treated with rituximab.  

PubMed

We evaluated hypoxia inducible factor-1? (HIF-1?) and vascular endothelial growth factor (VEGF) expression and their prognostic significance in diffuse large B-cell lymphoma (DLBCL). Expression of HIF-1? and VEGF was studied in 78 patients and results correlated with clinicopathological and prognostic data. HIF-1? and VEGF were expressed in 67% and 84% of patients, respectively, and a significant correlation was demonstrated between them (p < 0.001). Outcome was analyzed according to treatment. HIF-1? positive patients given rituximab demonstrated improved outcome, with 5-year overall survival of 72% for those receiving rituximab versus 65% for those not receiving rituximab, and 5-year progression-free survival (PFS) 76% versus 57%. No correlation was demonstrated between HIF-1? and other prognostic biomarkers including BCL6, CD10 and MUM-1. We demonstrated significantly improved PFS (p = 0.003) in patients receiving rituximab and showing BCL6 overexpression. The results confirm the significant association between HIF-1? and VEGF expression and suggest that HIF-1? expression is a favorable prognostic factor in patients with DLBCL treated with rituximab. PMID:23020605

Powell, James R; Dojcinov, Stefan; King, Louise; Wosniak, Sue; Gerry, Stephen; Casbard, Angela; Bailey, Hazel; Gallop-Evans, Eve; Maughan, Tim

2012-10-16

290

Mold with porous cavity vent  

US Patent & Trademark Office Database

A mold for injection molding of long thin walled articles has precisely balanced high-volume venting of a narrow cavity space surrounding a long slender cantilevered core and minimized flash. The venting is provided by closing an end of the female mold cavity with a sintered metal plug and forming an end of the mold cavity in an end face of the plug.

1979-08-21

291

Interaction of Electrons with Cavities.  

National Technical Information Service (NTIS)

The radiation emitted by an electron traversing an output cavity tuned to a single frequency after having traversed an excited input cavity is calculated using quantum field theory. It is found that the emission has maxima when the output cavity is tuned ...

C. S. Chang P. Stehle

1972-01-01

292

Interaction of Electrons with Cavities  

Microsoft Academic Search

The radiation emitted by an electron traversing an output cavity tuned to a single frequency after having traversed an excited input cavity is calculated using quantum field theory. It is found that the emission has maxima when the output cavity is tuned to a harmonic of the inputcavity frequency, the result being very similar to classical klystron theory. The emitted

C. S. Chang; P. Stehle

1972-01-01

293

NIOBIUM IN SUPERCONDUCTING RF CAVITIES  

Microsoft Academic Search

Niobium is the favorite metal for the fabrication of superconducting accelerating cavities. While the majority of these cavities are formed from niobium sheet material a large number of copper cavities have been made with a thin niobium film on the inner surface produced by sputter coating. The resonators are operated well below the transition temperature of niobium (9.2K). A high

Dieter Proch; Peter Schmueser; Waldemar Singer; Lutz Lilje

294

Digital Cavity Resonance Monitor, alternative method of measuring cavity microphonics  

SciTech Connect

As is well known, mechanical vibration or microphonics in a cryomodule causes the cavity resonance frequency to change at the vibration frequency. One way to measure the cavity microphonics is to drive the cavity with a Phase Locked Loop. Measurement of the instantaneous frequency or PLL error signal provides information about the cavity microphonic frequencies. Although the PLL error signal is available directly, precision frequency measurements require additional instrumentation, a Cavity Resonance Monitor (CRM). The analog version of such a device has been successfully used for several cavity tests [1]. In this paper we present a prototype of a Digital Cavity Resonance Monitor designed and built in the last year. The hardware of this instrument consists of an RF downconverter, digital quadrature demodulator and digital processor motherboard (Altera FPGA). The motherboard processes received data and computes frequency changes with a resolution of 0.2 Hz, with a 3 kHz output bandwidth.

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

2005-09-20

295

Wind Observations of Foreshock Cavities  

NASA Astrophysics Data System (ADS)

Wave-particle interactions energize a small fraction of the solar wind ions in the foreshock to high energies. Pressures associated with the energized ions cause bundles of magnetic field lines connected to the bow shock to expand, resulting in the formation of crater-like density, magnetic field strength, and temperature structures. While no events have been reported at the L1 libration point, previous reports indicate that the events are common just outside the subsolar bow shock, where they reach large amplitudes. We present a case study employing upstream monitors at three radial distances from Earth and then a statistical survey of Wind 3DP plasma and MFI magnetic field observations from 1994 to 1999 to determine the radial dependence of event characteristics. Plasma and magnetic field perturbations within the events are proportional to the flux of energetic ions, and densities within the events are typically depressed some 20 per cent from those in the ambient solar wind. As the flux of energetic ions decays and pitch angle distributions transition from diffuse to streaming with upstream distance, so do the perturbations. Consequently, the cavities attain greatest prominance (and significance to the solar wind-magnetosphere interaction) just outside the bow shock during periods of low solar wind density and magnetic field strength.

Sibeck, D. G.; Phan, T. D.; Lin, R. P.; Lepping, R. P.

2002-05-01

296

External cavity laser biosensor.  

PubMed

Utilizing a tunable photonic crystal resonant reflector as a mirror of an external cavity laser cavity, we demonstrate a new type of label-free optical biosensor that achieves a high quality factor through the process of stimulated emission, while at the same time providing high sensitivity and large dynamic range. The photonic crystal is fabricated inexpensively from plastic materials, and its resonant wavelength is tuned by adsorption of biomolecules on its surface. Gain for the lasing process is provided by a semiconductor optical amplifier, resulting in a simple detection instrument that operates by normally incident noncontact illumination of the photonic crystal and direct back-reflection into the amplifier. We demonstrate single-mode, biomolecule-induced tuning of the continuous-wave laser wavelength. Because the approach incorporates external optical gain that is separate from the transducer, the device represents a significant advance over previous passive optical resonator biosensors and laser-based biosensors. PMID:23429747

Ge, Chun; Lu, Meng; George, Sherine; Flood, Timothy A; Wagner, Clark; Zheng, Jie; Pokhriyal, Anusha; Eden, J Gary; Hergenrother, Paul J; Cunningham, Brian T

2013-04-01

297

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

298

Holographic diffusers  

NASA Astrophysics Data System (ADS)

Holographic diffusers are prepared using silver halide (Agfa 8E75 and Kodak 649F) and photopolymer (Polaroid DMP 128 and DuPont 600, 705, and 150 series) media. It is possible to control the diffusion angle in three ways: by selection of the properties of the source diffuser, by control of its subtended angle, and by selection of the holographic medium. Several conventional diffusers based on refraction or scattering of light are examined for comparison.

Wadle, Stephen; Wuest, Daniel; Cantalupo, John; Lakes, Roderic S.

1994-01-01

299

BEAM DIFFUSION MEASUREMENTS AT RHIC.  

SciTech Connect

During a store, particles from the beam core continually diffuse outwards into the halo through a variety of mechanisms. Understanding the diffusion rate as a function of particle amplitude can help discover which processes are important to halo growth. A collimator can be used to measure the amplitude growth rate as a function of the particle amplitude. In this paper we present results of diffusion measurements performed at the Relativistic Heavy Ion Collider (RHIC) with fully stripped gold ions, deuterons, and protons. We compare these results with measurements from previous years, and simulations, and discuss any factors that relate to beam growth in RHIC.

FLILLER,R.P.,IIIDREES,A.GASSNER,D.MCINTYRE,G.PEGGS,S.TRBOJEVIC,D.

2003-05-12

300

Diffusion MRI  

NASA Astrophysics Data System (ADS)

Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

Fukuyama, Hidenao

301

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

302

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

303

Experimental investigation of a chemical-laser-cavity flowfield. Master's thesis  

SciTech Connect

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold air as the working medium, the flow control system configuration and nozzle-cavity-supersonic diffuser assembly configuration were developed to establish acceptable flow conditions in the test section. Performance evaluation was based on pressure measurements in the nozzle-cavity-diffuser assembly and schlieren photographs of the flowfield in the cavity. Flow conditions in the test section were broken up into three different regions: flow in the hypersonic nozzles, flow in the base region and flow in the cavity region. Flow in the nozzles was analyzed using one-dimensional, steady, isentropic flow theory. Test results indicated that the hypersonic nozzles performed to design specifications. The Korst two-dimensional base-pressure flow model was used to describe the flow in the nozzle exit plane and base region. Experimentally calculated Mach numbers and static pressures corresponded very closely to theoretical values. Static pressure ports and schlieren photographs were used to describe the flow-field conditions in the cavity region. Pressure measurements indicated that supersonic conditions were reached in the cavity for specific supersonic diffuser throat areas settings, but conditions were short lived. Boundary layer, frictional, and three-dimensional effects were suspected as the main contributors to the flowfield degradation.

Stiglich, S.W.

1989-12-01

304

Growth  

NASA Astrophysics Data System (ADS)

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

Waag, Andreas

305

Superconducting cavities and modulated RF  

SciTech Connect

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

Farkas, Z.D.

1981-02-01

306

Diffusion Limited Aggregation  

NSDL National Science Digital Library

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

Joiner, David; The Shodor Education Foundation, Inc.

307

Cavity soliton billiards  

SciTech Connect

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

Prati, F.; Lugiato, L. A. [CNISM and Dipartimento di Fisica e Matematica, Universita dell'Insubria, Via Valleggio 11, I-22100 Como (Italy); Tissoni, G. [Institut Non Lineaire de Nice, UMR 6618, Universite de Nice Sophia Antipolis,1361 Route des Lucioles, F-06560 Valbonne (France); Brambilla, M. [CNISM and Dipartimento Interateneo di Fisica, Universita e Politecnico di Bari, Via Amendola 173, I-70123 Bari (Italy)

2011-11-15

308

Electrically injected cavity polaritons.  

PubMed

We have realized an electroluminescent device operating in the light-matter strong-coupling regime based on a GaAs/AlGaAs quantum cascade structure embedded in a planar microcavity. At zero bias, reflectivity measurements show a polariton anticrossing between the intersubband transition and the cavity mode. Under electrical injection the spectral features of the emitted light change drastically, as electrons are resonantly injected in a reduced part of the polariton branches. Our experiments demonstrate that electrons can be selectively injected into polariton states up to room temperature. PMID:18517986

Sapienza, L; Vasanelli, A; Colombelli, R; Ciuti, C; Chassagneux, Y; Manquest, C; Gennser, U; Sirtori, C

2008-04-04

309

Optimization of klystron buncher cavities  

NASA Astrophysics Data System (ADS)

The bandwidth of a klystron output cavity scale (approximately) as...0.8P0.2, where p is the beam perveance and P is the beam power. For high-perveance (p > 10 (mu) pervs), high-power (P > 10 kW) electron beams, it is relatively straightforward to design a broadband output cavity. However, the design of the input cavity of the broadband klystron is more difficult. The purpose of the input cavity is to produce a velocity-moldulated electron beam with a frequency-dependant modulation amplitude that will optimize the bandwidth of the entire klystron system, while providing a large enough magnitude of velocity modulation to minimize the length of the klystron. This paper shows how a multiplet (multiple cavity) buncher cavity can be designed to provide broadband (> 20%) operation while keeping the drift length of the klystron short.

Bromborsky, Alan

1995-09-01

310

Particle diffusion in overlapping resonances  

SciTech Connect

Longitudinal bunch dilution was studied in the IUCF Cooler Ring with phase modulation of a higher-order harmonic rf. Diffusion in the presence of overlapping parametric resonances has been identified as the dilution mechanism. We found that fast growth is associated with the rapid particle motion along separatrices of dominant parametric resonances, slow growth is related to particle diffusion in the chaotic sea, and saturation occurs when particles are bounded by an invariant torus.

Ng, K.Y.

1998-01-01

311

Optimization of klystron buncher cavities  

Microsoft Academic Search

The bandwidth of a klystron output cavity scale (approximately) as...0.8P0.2, where p is the beam perveance and P is the beam power. For high-perveance (p > 10 (mu) pervs), high-power (P > 10 kW) electron beams, it is relatively straightforward to design a broadband output cavity. However, the design of the input cavity of the broadband klystron is more difficult.

Alan Bromborsky

1995-01-01

312

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

313

Reactor cavity pool seal  

SciTech Connect

A reactor cavity pool seal is described wherein a removable annular seal plate has an upper surface substantially co-planar with one of a cavity well ledge and a reactor flange upper surface and has a circular edge surface spaced in opposition to a circular face beneath the one of the ledge and flange upper surface, and annular inflatable means are provided in effecting a seal between the spaced circular edge surface and face. The improvement comprises: (a) a flat seal ring on the seal plate, and (b) an annular bearing plate of the same thickness as the seal ring on one of the ledge and flange upper surface, (c) the seal ring and bearing plate defining opposed spaced circular respective inner and outer sealing surfaces, (d) the seal ring being fixed and sealed to the plate and the bearing ring being fixed and sealed to the ione of the ledge and flange upper surface such that the inner and outer sealing surfaces are concentric, (e) the annular inflatable means being located between and operable against the opposed inner and outer sealing surfaces.

Puri, A.

1988-06-28

314

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

315

Power coupler kick of the TRIUMF ICM capture cavities  

NASA Astrophysics Data System (ADS)

The TRIUMF Injector CryoModule (ICM) adapted two superconducting single cavities as the capture section for the low injecting energy of 100 keV electrons. Coupler kick induced beam deflection and projected emittance growth are one of the prime concerns of the beam stability, especially at low energies. In low energy applications, the electron velocity changes rapidly inside the cavity, which makes the numerical analysis much more complicated. The commonly used theoretical formulas of the direct integral or the Panofsky-Wenzel theorem is not suitable for the kick calculation of ? < 1 electrons. Despite that, the above mentioned kick calculation method doesn't consider injecting electron energy, the beam offset due to the coupler kick may not be negligible because of the low injection energy even if the kick is optimized. Thus the beam dynamics code TRACK is used here for the simulation of the power coupler kick perturbation. The coupler kick can be compensated for by a judicious choice of the coupler position in successive cavities from upstream to downstream. The simulation shows that because of the adiabatic damping by the following superconducting 9-cell cavity, even for the worst orbit distortion case after two capture cavities, the kick is still acceptable at the exit of the ICM after reaching 10 MeV. This paper presents the analysis of the transverse kick and the projected emittance growth induced by the coupler for ? < 1 electrons. The simulated results of the TRIUMF ICM capture cavities are described and presented.

Yan, Fang; E. Laxdal, R.; Zvyagintsev, V.; Yu., Chao; C., Gong; Koscielniak, S.

2011-06-01

316

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

2012-01-01

317

Isothermal cavity, blackbody radiation source.  

PubMed

A prototype blackbody radiation source has been developed which incorporates a double cone cavity of extremely uniform surface temperature. This uniformity of surface temperature is the result of a unique method of supplying heat to the cavity. The principle of operation is based on heat pipe techniques which transfer heat by change of phase and mass transfer. The cavity is heated by serving as the condenser section of the heat pipe which is inherently a nearly isothermal device. Optical tests show that the isothermal cavity has a lambertian distribution over an inclusive angle of better than 60 degrees while operating between 419 degrees C and 760 degrees C. PMID:20094191

Bliss, F E; Davis, S; Stein, B

1970-09-01

318

Characterization, dynamics and stabilization of diffractive domain walls and dark ring cavity solitons in parametric oscillators  

NASA Astrophysics Data System (ADS)

Mean field models of spatially extended degenerate optical parametric oscillators possess one-dimensional stable domain wall solutions in the presence of diffraction. We characterize these structures as spiral heteroclinic connections and study the spatial frequency of the local oscillations of the signal intensity which distinguish them from diffusion kinks. Close to threshold, at resonance or with positive detunings, the dynamics of two-dimensional diffractive domain walls is ruled by curvature effects with a t1/2 growth law, and coalescence of domains is observed. In this regime, we show how to stabilize regular and irregular distributions of two-dimensional domain walls by injection of a helical wave at the pump frequency. Further above threshold the shrinking of domains of one phase embedded in the other is stopped by the interaction of the oscillatory tails of the domain walls, leading to cavity solitons surrounded by a characteristic dark ring. We investigate the nature and stability of these localized states, provide evidence of their solitonic character, show that they correspond to spiral homoclinic orbits and find that their threshold of appearance lowers with increasing pump cavity finesse.

Oppo, Gian-Luca; Scroggie, Andrew J.; Firth, William J.

2001-06-01

319

Two-cavity klystron uses single-cavity tuning  

Microsoft Academic Search

Two techniques have been generally used to construct a tunable, two-cavity klystron. The first involves the use of a movable plunger in each cacity, while the second employs a single diaphram to tune both cavities. Problems concerning the use of these techniques are related to variations in the output power with tuning. The present investigation is concerned with a klystron

A. Muratore; G. Busacca; V. Meli

1983-01-01

320

FORWARD MODELING CAVITY DENSITY: A MULTI-INSTRUMENT DIAGNOSTIC  

SciTech Connect

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

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

2011-05-20

321

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

PubMed

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

2013-07-30

322

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

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

323

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.

Grigory Eremeev, Rongli Geng, Ari Palczewski, Jin Dai

2011-07-01

324

Cavity excitation of coherent hypersound  

Microsoft Academic Search

In this paper, we analyze the generation of hypersonic waves via piezoelectric surface excitation in cavity resonators and derive formulas enabling one to calculate the electromechanical conversion factor and the electric field direction for optimal excitation of any pure acoustic mode, provided the relevant material constants and cavity parameters are known. Quantitative results are given for certain acoustic modes in

D. Soumpasis

1973-01-01

325

On the collapse of cavities  

Microsoft Academic Search

The collapse of a single cavity, or a cloud of bubbles has several physical consequences when in proximity to a structure or resident within a material during deformation. The earliest recognized of these was cavitation erosion of the propellers of steam ships. However, other processes include the rapid collapse of cavities leading to hot spots in explosives from which reaction

N. K. Bourne

2002-01-01

326

Light Forces In Cavity QED  

Microsoft Academic Search

Mirrors are ideal tools for controlling the optical and motional properties of an atom. To understand the physics of the light force in a cavity, and to explain why this force can be so much larger than in free space, we present an intuitive corpuscular picture based on the notion of cavity-enhanced photon scattering. We also discuss a nonintuitive phenomenon

Gerhard Rempe; Karim Murr

2006-01-01

327

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

328

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

329

Teratocarcinosarcoma of the nasal cavity and ethmoid.  

PubMed

Sinonasal teratocarcinosarcoma is very unusual malignant neoplasm histologically consisting of an epithelial element and one or more mesenchymal components. This is a report of teratocarcinosarcoma, in a 74-year-old male, involving the right nasal cavity and ethmoids with intracranial extension. The tumour was totally resected via the craniofacial approach and the patient was given post-operative chemotherapy. Extensive tumour necrosis, rapid growth and local destruction are the prominent features of this tumour. The clinical presentation, pathological features and clinical course of this rare malignancy are discussed with a review of the literature. PMID:9775307

Sharma, H S; Abdullah, J M; Othman, N H; Muhamad, M

1998-07-01

330

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

331

Observation of multiple sub-cavities adjacent to single separatrix  

NASA Astrophysics Data System (ADS)

investigate a direct south-north crossing of a reconnection ion diffusion region in the magnetotail. During this crossing, multiple electron density dips with a further density decrease within the cavity, called sub-cavities, adjacent to the northern separatrix are observed. The correlation between electron density sub-cavities and strong electric field fluctuations is obvious. Within one of the sub-cavities, a series of very strong oscillating perpendicular electric field and patchy parallel electric field are observed. The parallel electric field is nearly unipolar and directs away from X line. In the same region, inflow electrons with energy up to 100 keV are injected into the X line. Based on the observations, we conclude that the high-energy inflowing electrons are accelerated by the patchy parallel electric field. Namely, electrons have been effectively accelerated while they are flowing into the X line along the separatrix. The observations indicate that the electron acceleration region is widely larger than the predicted electron diffusion region in the classical Hall magnetic reconnection model.

Wang, Rongsheng; Du, Aimin; Nakamura, Rumi; Lu, Quanming; Khotyaintsev, Yuri V.; Volwerk, Martin; Zhang, Tielong; Kronberg, E. A.; Daly, P. W.; Fazakerley, Andrew N.

2013-06-01

332

Vaneless diffusers  

NASA Astrophysics Data System (ADS)

The influence of vaneless diffusers on flow in centrifugal compressors, particularly on surge, is discussed. A vaneless diffuser can demonstrate stable operation in a wide flow range only if it is installed with a backward leaning blade impeller. The circumferential distortion of flow in the impeller disappears quickly in the vaneless diffuser. The axial distortion of flow at the diffuser inlet does not decay easily. In large specific speed compressors, flow out of the impeller is distorted axially. Pressure recovery of diffusers at distorted inlet flow is considerably improved by half guide vanes. The best height of the vanes is a little 1/2 diffuser width. In small specific speed compressors, flow out of the impeller is not much distorted and pressure recovery can be predicted with one-dimensional flow analysis. Wall friction loss is significant in narrow diffusers. The large pressure drop at a small flow rate can cause the positive gradient of the pressure-flow rate characteristic curve, which may cause surging.

Senoo, Y.

333

Coalescence of large grain boundary cavities in silver during tension creep  

Microsoft Academic Search

An experimental technique for implanting water vapor bubbles in silver was used to produce a uniform distribution of very large cavities along the grain boundaries of high purity silver. By implanting these very large bubbles prior to the onset of creep, the kinetics of the final stages of creep cavity growth and coalescence can be studied. The stress and temperature

S. H. Goods; W. D. Nix

1978-01-01

334

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

Microsoft Academic Search

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

KENT D. CHOQUETTE; HONG Q. HOU

1997-01-01

335

Marangoni flows in open cavities with differentially heated end walls  

Microsoft Academic Search

Surface tension driven flows, induced by imposed temperature differences, in plane cavities with differentially heated end walls are considered. This configuration is connected to processes of crystal growth from melt by the open boat horizontal technique. The field equations are numerically solved and the free surface shape is computed under the assumption of small capillary number. Attention is focused on

C. Golia; Antonio Viviani; Dario Castagnolo

1992-01-01

336

Composite resonator vertical cavity laser diode  

SciTech Connect

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

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

1998-05-01

337

Sarcomatoid carcinoma in the pelvic cavity.  

PubMed

Sarcomatoid carcinoma in the pelvic cavity is very rare. A 58-year-old Japanese man was admitted to our hospital because of lower abdominal fullness. CT and MRI revealed a large mass in the left pelvic cavity. Transurethral bladder endoscopy showed tumor invasion, and large biopsies were obtained from the bladder lesion. Histologically, the tumor was composed of malignant round cells with hyperchromatic nuclei. Many intracytoplasmic vacuoles were present. No carcinomatous areas were seen. Immunohistochemically, the tumor cells were positive for cytokeratin (CK) 18, vimentin, p53 and Ki-67 (labeling 80%). The tumor cells were negative for panCK AE1/3, CD5/6, CK7, CK8, CK14, CK19, CK20, CK 34BE12, EMA, desmin, calretinin, WT-1, S100 protein, ?-smooth muscle actin, CEA, CD34, CD45, CD20, factor VIII-related antigen, synaptophysin, p63, CDX2, and myoglobin. Because the CK18 was diffusely expressed, the pathological diagnosis was sarcomatoid carcinoma. PMID:23573329

Terada, Tadashi

2013-03-15

338

Sarcomatoid carcinoma in the pelvic cavity  

PubMed Central

Sarcomatoid carcinoma in the pelvic cavity is very rare. A 58-year-old Japanese man was admitted to our hospital because of lower abdominal fullness. CT and MRI revealed a large mass in the left pelvic cavity. Transurethral bladder endoscopy showed tumor invasion, and large biopsies were obtained from the bladder lesion. Histologically, the tumor was composed of malignant round cells with hyperchromatic nuclei. Many intracytoplasmic vacuoles were present. No carcinomatous areas were seen. Immunohistochemically, the tumor cells were positive for cytokeratin (CK) 18, vimentin, p53 and Ki-67 (labeling 80%). The tumor cells were negative for panCK AE1/3, CD5/6, CK7, CK8, CK14, CK19, CK20, CK 34BE12, EMA, desmin, calretinin, WT-1, S100 protein, ?-smooth muscle actin, CEA, CD34, CD45, CD20, factor VIII-related antigen, synaptophysin, p63, CDX2, and myoglobin. Because the CK18 was diffusely expressed, the pathological diagnosis was sarcomatoid carcinoma.

Terada, Tadashi

2013-01-01

339

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

340

Novel Crab Cavity RF Design  

SciTech Connect

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

A. Dudas, M.L. Neubauer, R. Sah, R.A. Rimmer, H. Wang

2011-03-01

341

Microwave cavity search for paraphotons  

SciTech Connect

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

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

2010-06-15

342

Atoms and photonic crystal cavities  

NASA Astrophysics Data System (ADS)

Atoms coupled to micro- or nano-scale optical resonators create a system interesting both for fundamental studies and practical applications. In particular, photonic crystal cavities fabricated in thin semiconductor membranes have extremely small optical mode volumes and are well suited for integration with optical waveguides and on-chip electronics. Here, we study how deposition of cesium atoms affects the properties of a photonic crystal cavity fabricated in gallium phosphide. Additionally, we introduce a proposal for a single photon switching scheme based on cesium atoms coupled to a photonic crystal cavity with a moderate Q-factor.

Bajcsy, Michal; Faraon, Andrei; Rivoire, Kelley; Majumdar, Arka; Vuckovic, Jelena

2011-06-01

343

Cavity QED in microsphere and Fabry-Perot cavities  

NASA Astrophysics Data System (ADS)

A long-standing ambition in the field of cavity quantum electrodynamics has been to trap single atoms inside high-Q cavities in a regime of strong coupling. Our goal has been to develop techniques for trapping that are compatible with strong coupling and that do not interfere with the cavity QED interactions. This is crucial for applications to quantum computation and communication. We have accomplished this goal by creating a trapping potential through an intracavity FORT at the 'magic' wavelength for Cesium, 935.6 nm. Unlike typical FORTS, where the signs of the AC-Stark shifts for excited and ground states are opposite, our trap causes small shifts to the relevant transition frequencies, enabling a trapping potential for the center-of-mass motion that is largely independent of the internal atomic state. This has enabled us to achieve extended trapping times (˜3 sec) for individual Cesium atoms in cavity QED in a regime of strong coupling. Although our longest lifetimes are obtained when the probing fields are turned off, the atoms can also be continuously monitored, leading to mean trapping times of 0.4 sec, with some atoms observed for over 1 sec. An important tool for studying atom-field interactions is a high-Q cavity with small mode volume. Considerable effort has been made in advancing our capabilities for high-Q resonators. While much of our work involves Fabry-Perot cavities, some of the highest quality optical resonators to date have been achieved with the whispering gallery modes (WGMs) of quartz microspheres ( Q ˜ 8 x 109). Therefore, considerable effort has been given to understanding the usefulness of microspheres for cavity QED with strong coupling. We have also worked at manufacturing high-Q microspheres suitable for cavity QED. To this end, we have been successful at making spheres with radius ˜10 mum and Q ˜ 107.

Buck, Joseph R., Jr.

344

New Chorus Diffusion Matrix  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

345

Growth mechanisms of (0 0 .1)GaN substrates in the hydride vapour-phase method: surface diffusion, spiral growth, H 2 and GaCl 3 mechanisms  

Microsoft Academic Search

The theoretical model developed to account for the {001}GaAs growth in the AsCl3\\/H2 and AsCl3\\/He systems is applied to the (00.1)GaN growth by hydride vapour-phase epitaxy in H2 or neutral carrier gases. The two growth mechanisms of chlorine desorption in HCl and in GaCl3 and the step flow and spiral growth processes are investigated. The model was improved by adding

Robert Cadoret

1999-01-01

346

Parallel Shear Flows Over Cavities.  

National Technical Information Service (NTIS)

Incompressible separated flows have long presented problems to the theoretician. Parallel shear flow over a cavity is an ideal flow configuration to evaluate numerically to shed light on fundamental relationships. It also provides a basis to predict flow ...

V. O'Brien

1970-01-01

347

Theoretical Study of Optical Cavities.  

National Technical Information Service (NTIS)

A theoretical study is performed of the resonant modes of a laser cavity having end mirrors with periodic reflectivity. Two particular examples are examined: the case of end mirrors constituted by two identical strip diffraction gratings, and the case of ...

L. Ronchi A. M. Scheggi G. Toraldo di Francia

1964-01-01

348

In-situ imaging of creep cavities by synchrotron microradiography  

SciTech Connect

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

Dobbyn, R.C.; Fields, R.J. (National Institute of Standards and Technology, Gaithersberg, MD (US)); Farris, J.; Harlow, D.G.; Delph, T.J. (Dept. of Mechanics and Mechanical Engineering, Lehigh Univ., Bethlehem, PA (US))

1989-05-01

349

Metastases to the oral cavity.  

PubMed

Metastatic spread to the oral cavity of a malignant neoplasm is a rare yet important sign of advanced systemic malignant disease. This manuscript briefly describes the metastatic process and highlights the most common neoplasms that metastasise to the oral cavity as well as their clinical and radiological presentations. The role of the patients' history in suspecting metastatic disease and the importance of a microscopic diagnosis is emphasised. PMID:23957102

Raubenheimer, E J; Noffke, C E E; Hendrik, H D

2012-11-01

350

On the collapse of cavities  

Microsoft Academic Search

.   The collapse of a single cavity, or a cloud of bubbles has several physical consequences when in proximity to a structure\\u000a or resident within a material during deformation. The earliest recognized of these was cavitation erosion of the propellers\\u000a of steam ships. However, other processes include the rapid collapse of cavities leading to hot spots in explosives from which

N. K. Bourne

2002-01-01

351

Self-Organizing Laser Cavities  

Microsoft Academic Search

The insertion of a photorefractive crystal in a laser cavity leads to spectacular behaviours. The oscillating modes record\\u000a a dynamic hologram. For a correctly designed cavity, this hologram acts as a spectral or\\/and spatial filter, which, in turn,\\u000a modifies the relative losses of these modes. Through the interaction with the amplifying medium, this modification of losses\\u000a redistributes the energy between

Gilles Pauliat; Nicolas Dubreuil; Gérald Roosen

352

Bacterial penetration of restored cavities.  

PubMed

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

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

2001-03-01

353

Holographic diffusers  

NASA Astrophysics Data System (ADS)

Diffusers are playing an increasingly important role in optics as a means to either improve uniformity of light applied for illumination of an object, or to improve visibility of an image created by an optical system from a wider range of angles. Probably the most popular applications of the first kind are milky light bulbs commonly used as light sources in our houses or flat panel displays with backlight illumination used in portable computers. The best known application of the second kind is an ordinary wall used as a screen for slide or film projector. Other examples of this type are diffusers in the view finding systems of some photographic and film cameras and in a variety of rear image projection systems (like microfiche readers or rear TV projection systems, for example). It is obvious, in this context, that demand for diffusers will increase with expansion of such systems.

Pawluczyk, Romuald

1994-01-01

354

Shunt Impedance of the MBK Cavities  

Microsoft Academic Search

There are a lot of kinds of multiple beam cavities used in klystron amplifiers. Ring, classic cylindrical and multiple barrel cavities have been researched using CST Microwave Studio 5.0 simulation code. Shunt impedance of klystron cavities determines the efficiency of interaction of electron beam with EM field. So Rsh\\/Q values of cavities of interest are considered

A. N. Sandaliv; Konstantin A. Zaytsev; Yaogen Ding; Bin Shin

2006-01-01

355

Controlled directional scattering cavity for tubular absorbers  

Microsoft Academic Search

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

1982-01-01

356

Plasmid stability in immobilized and free recombinant Escherichia coli JM105(pKK223-200): importance of oxygen diffusion, growth rate, and plasmid copy number.  

PubMed Central

Stability of the plasmid pKK223-200 in Escherichia coli JM105 was studied for both free and immobilized cells during continuous culture. The relationship between plasmid copy number, xylanase activity, which was coded for by the plasmid, and growth rate and culture conditions involved complex interactions which determined the plasmid stability. Generally, the plasmid stability was enhanced in cultured immobilized cells compared with free-cell cultures. This stability was associated with modified plasmid copy number, depending on the media used. Hypotheses are presented concerning the different plasmid instability kinetics observed in free-cell cultures which involve the antagonistic effects of plasmid copy number and plasmid presence on the plasmid-bearing/plasmid-free cell growth rate ratio. Both diffusional limitation in carrageenan gel beads, which is described in Theoretical Analysis of Immobilized-Cell Growth, and compartmentalized growth of immobilized cells are proposed to explain plasmid stability in immobilized cells.

de Taxis du Poet, P; Arcand, Y; Bernier, R; Barbotin, J N; Thomas, D

1987-01-01

357

Cavity QED with multilevel atoms  

NASA Astrophysics Data System (ADS)

The steady-state transmission spectrum of a cavity with two modes of orthogonal polarization strongly coupled to a single atom with multiple Zeeman states is computed. Effects due to cavity birefringence and atomic ac-Stark shifts are included. The transmission spectrum is compared to experimental results for a single Cesium atom trapped via an intracavity FORT in a Fabry-Perot cavity. The excellent agreement of the theory with the data is used to infer the distribution of the position of the trapped atom. The intensity correlation function of this system is also calculated, and found to be strongly antibunched and sub-Poissonian. This effect is explained in terms of photon blockade, based on the structure of the lowest energy eigenvalues. Experimental results confirm the strong nonlinearity at the single-photon level. We present theoretical predictions of the weak field spectra of microtoroid and photonic bandgap cavities strongly coupled to the D2 transition of single Cesium atoms. These calculations include all hyperfine and Zeeman states of the transition and model the cavity as a single-mode, linearly polarized resonator. Finally, we outline a technique for using multiple hyperfine and Zeeman levels of a single atom in a strongly coupled atom-cavity system to generate polarized single photons on demand in a well-defined temporal mode via adiabatic passage. The technique is insensitive to cavity birefringence and only weakly sensitive to atomic position. Variations of this technique for generating entanglement of photon polarization and atomic Zeeman state are also discussed.

Birnbaum, Kevin M.

358

Examination of UCG cavities for the Large Block Test, Centralia, Washington. [Post mortem examination  

SciTech Connect

This article describes general and specific characteristics of five underground coal gasification (UCG) cavities within the Big Dirty coal seam, Centralia, WA. The experiments involved both forward and reverse burns along drilled injection holes. Various mixtures of steam, oxygen, and air were injected into the seam. We have examined and photographed exposures of these cavities while the coal seam was sliced approximately every 1.5 m. Sixty-eight cavity exposures have been photographed, of which 26 were mapped in detail. We also present interpretations of these observations. Generally, the cavities were filled with dried coal, char, ash and slag, with open voids at the top of some. The ash and slag were always confined to the immediate vicinity of the injection borehole, and the cavities were taller than they were wide. Some cavity cross sections showed an abrupt widening of the sides of the char zone surrounding the cavity, which defined horizontal, finger-like margins a few metres long. These margins generally occurred near or between partings within the coal. The evidence suggests that the cavities primarily grew upwards. Where side growth was substantial, it was localized and strongly influenced by geologic structure. The bottoms of the cavities were bowl-shaped, while the roofs along the larger, well developed sections of the cavities were generally flat with approximately square corners. A significant void was observed in many cavities between the roof and the rubble filling the cavity. Although there were some differences between individual cavities, these were not clearly related to the various changes in gasification conditions performed during the burn.

Ramirez, A.L.; Wilder, D.G.; Pawloski, G.A.

1982-07-01

359

Local mass transfer in skewed rectangular cavities  

NASA Astrophysics Data System (ADS)

Turbulent mass transfer from surfaces of rectangular cavities is studied experimentally using the naphthalene sublimation technique. Cavity aspect ratios of 1.1, 2.2, 4.4, and 6.7 were used as well as cavity-skew angles of 90, 85, 80, and 75 deg. It is found that variation of the local mass transfer distribution on each cavity wall is strongly dependent on the aspect ratio of the cavity.

Chyu, M. K.; Kapat, J. S.

360

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

361

Analysis of the spectral relationships of cavity tones in subsonic resonant cavity flows  

NASA Astrophysics Data System (ADS)

The understanding of the self-sustained flow-acoustic coupling mechanism in flows over shallow rectangular cavities is of great interest owing to its various practical applications. The ability to understand and predict the resonant frequencies in such flows has recently been advanced through contributions from signal processing theory and by viewing the Rossiter tones as the product of an amplitude modulation process between a fundamental aeroacoustic loop frequency (fa) and a modulating lower frequency. The results obtained using this approach applied to detailed and high-quality spectral data of shallow cavity flow over the Mach number range of 0.20-0.65 are presented and discussed. The new approach, while not a predictive technique, is used to clearly identify all the tones (Rossiter modes, their harmonics, and harmonics of fa) observed in the pressure spectra and to show relationships between the tones. The asymptotic growth with Mach number of fa and the small-step changes of the modulating lower frequency over the Mach number range studied provide insight into the variation of the Rossiter mode parameters. The results also indicate that the empirical parameters in the Rossiter equation vary with Mach number for fixed cavity geometry.

Malone, J.; Debiasi, M.; Little, J.; Samimy, M.

2009-05-01

362

Nanocrystal diffusion doping.  

PubMed

A diffusion-based synthesis of doped colloidal semiconductor nanocrystals is demonstrated. This approach involves thermodynamically controlled addition of both impurity cations and host anions to preformed seed nanocrystals under equilibrium conditions, rather than kinetically controlled doping during growth. This chemistry allows thermodynamic crystal compositions to be prepared without sacrificing other kinetically trapped properties such as shape, size, or crystallographic phase. This doping chemistry thus shares some similarities with cation-exchange reactions, but proceeds without the loss of host cations and excels at the introduction of relatively unreactive impurity ions that have not been previously accessible using cation exchange. Specifically, we demonstrate the preparation of Cd1-xMnxSe (0 ? x ? ?0.2) nanocrystals with narrow size distribution, unprecedentedly high Mn(2+) content, and very large magneto-optical effects by diffusion of Mn(2+) into seed CdSe nanocrystals grown by hot injection. Controlling the solution and lattice chemical potentials of Cd(2+) and Mn(2+) allows Mn(2+) diffusion into the internal volumes of the CdSe nanocrystals with negligible Ostwald ripening, while retaining the crystallographic phase (wurtzite or zinc blende), shape anisotropy, and ensemble size uniformity of the seed nanocrystals. Experimental results for diffusion doping of other nanocrystals with other cations are also presented that indicate this method may be generalized, providing access to a variety of new doped semiconductor nanostructures not previously attainable by kinetic routes or cation exchange. PMID:24028655

Vlaskin, Vladimir A; Barrows, Charles J; Erickson, Christian S; Gamelin, Daniel R

2013-09-12

363

Ultrasmall subwavelength nanorod plasmonic cavity.  

PubMed

We propose an ultrasmall plasmonic cavity consisting of a high-index/low-index dielectric nanorod covered with silver. Full three-dimensional subwavelength confinement of the surface-plasmon polaritons was achieved at the high-index dielectric-silver interface without propagating to the low-index dielectric-silver interface. The numerical simulations showed that the plasmonic mode excited in this cavity has a deep subwavelength mode volume of 0.0038(?/2n)(3) and a quality factor of 1500 at 40 K, and consequently a large Purcell factor of ?2×10(5). Therefore, this plasmonic cavity is expected to be useful for the demonstration of high-efficiency single photon sources or low-threshold lasers in an ultracompact nanophotonic circuit. PMID:21633432

Kang, Ju-Hyung; No, You-Shin; Kwon, Soon-Hong; Park, Hong-Gyu

2011-06-01

364

Spontaneously walking discrete cavity solitons.  

PubMed

We study the dynamics of oscillating discrete solitons in an array of coupled Kerr-nonlinear cavities. They emanate from stationary discrete cavity solitons due to Hopf instability and are very robust. We show that these oscillating solitons can spontaneously lose their spatial symmetry and start rocking around the equilibrium position. Moreover they can suddenly jump to adjacent resonators starting a chaotic motion along the array, resembling the Brownian motion of particles. We also identify the parameter domain where they move with constant velocity across the array. PMID:23546226

Egorov, O A; Lederer, F

2013-04-01

365

Diffusion bonding  

DOEpatents

1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

Anderson, Robert C. (Oak Ridge, TN)

1976-06-22

366

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

367

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

Microsoft Academic Search

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

Lindsey K. Tuominen; Mary E. Musgrave

2006-01-01

368

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

369

Progress on a Be Cavity Design  

NASA Astrophysics Data System (ADS)

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, M. S.

2011-10-01

370

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

371

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.; Virostek, S.; Zisman, M. S. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Palmer, R.; Stratakis, D. [Brookhaven National Laboratory, Upton, NY 11973 (United States)

2011-10-06

372

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

373

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

374

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

375

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

Microsoft Academic Search

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

P. Rebuffet; A. Guedel

1982-01-01

376

A Diffusing Runner for Gravity Casting  

NASA Astrophysics Data System (ADS)

In gravity casting, the quality of an aluminum alloy casting relies on, among other things, the design of the runner system in which the ingate velocity into the mold cavity should be controlled to stay under a critical velocity (close to 0.5 m/s). In this study, a diffuser was proposed to reduce the velocity of liquid metal to below this critical value, while the flow rate remained almost unchanged. Flow separation and dead zones in the diffuser design were avoided. A computational modeling package and a real casting experiment (water analogy method) were employed for exploring and verifying the new design. The efficiency of the diffuser was quantified by the measurement of coefficient of discharge Cd. For this new diffuser, the pressure recovery coefficient C p and the loss coefficient K L were also estimated.

Hsu, Fu-Yuan; Lin, Huey-Jiuan

2009-12-01

377

Cavity flow control using a rod in cross flow  

NASA Astrophysics Data System (ADS)

For a variety of aerodynamic conditions and geometric configurations fluid structure interactions give rise to a reverberant field. This phenomenon, referred to as resonant acoustics, has practical importance due to its undesirable effects such as noise, structural loading, and unsteady flow field. Several flow control technologies exist but they lose efficacy at off-design conditions. With the focus on expanding their operating envelope, the present work investigates the physics of the flow control using a combination of detailed experimental measurements and theoretical analysis. The model resonant acoustic flow problem that we chose for our study is cavity tones, i.e., the high intensity acoustic tones produced by high speed air moving over rectangular cavity. The flow control actuator is a rod in cross flow, i.e., a thin horizontal rod placed upstream of the cavity. In the present work, a detailed experimental study has been undertaken to characterize the acoustics, mean velocity field as well as the pressure perturbation field both inside and outside of the cavity. Control cases with contrasting suppression results are chosen to illustrate important aspects of the mean flow field. To investigate whether the cylinder, through its wake, changes the stability characteristics of the shear layer that develops over the cavity, stability analysis of the shear layer is undertaken. First, stability of artificial velocity profiles that are prototypical of the experimentally measured velocity profiles is investigated; in order to determine what parameters of the velocity profiles influence the stability of the shear layer the most. Next stability of experimentally measured velocity profiles is evaluated to calculate integrated growth rates along the length of the cavity. Mean velocity data is also used to elucidate the shear layer lift off mechanism of the rod. Both integrated growth range and shear layer lift off data are compared with the acoustic suppression results. Based on the trends it appears that shear layer lift off, which interferes with the acoustic interaction between the shear layer and the trailing edge of the cavity, is the dominant mechanism by which the rod controls flow over the cavity.

Sarpotdar, Shekhar

378

Convective - diffusive mixing promoted by natural convection  

NASA Astrophysics Data System (ADS)

Mixing processes in fluids include two that can be clearly identified, advective and diffusive. We report a theoretical study of combined advective - diffusive mixing of a contaminant inside a cubic cavity with time-dependent boundary conditions. Advective mixing can be achieved by natural convection inside box-shaped cavities by imposing periodic hot and cold temperatures on opposite walls. Using these boundary conditions, no moving walls are required to mix the fluid inside the container. Regardless of the dynamic state of the fluid, a contaminant with an initial non-uniform concentration distribution inside the box will diffuse to smooth out the gradients and attaining asymptotically uniform concentration. Our model is based on the numerical solution of the conservation equations under the boundary conditions described above to generate natural convection. Advective mixing is evaluated with Lagrangian tracking and diffusive mixing is calculated with the Diffusive Strip Method of Meunier and Villermaux. We describe mixing efficiencies for cases dominated by each effect for an initially blob of contaminant.

de La Cruz, Luis M.; Ramos, Eduardo

2010-11-01

379

Linewidth of the electromagnetic radiation from Josephson junctions near cavity resonances  

NASA Astrophysics Data System (ADS)

The powerful terahertz emission from intrinsic Josephson junctions in high-Tc cuprate superconductors has been detected recently. The synchronization of different junctions is enhanced by excitation of the geometrical cavity resonance. A key characteristic of the radiation is its linewidth. In this work, we study the intrinsic linewidth of the radiation near the internal cavity resonance. Surprisingly, this problem was never considered before, neither for a single Josephson junction nor for a stack of the intrinsic Josephson junctions realized in cuprate superconductors. The linewidth appears due to the slow phase diffusion, which is determined by the dissipation and amplitude of the noise. We found that both these parameters are resonantly enhanced when the cavity mode is excited but enhancement of the dissipation dominates leading to the net suppression of diffusion and dramatic narrowing of the linewidth. The line shape changes from Lorentzian to Gaussian when either the Josephson frequency is shifted away from the resonance or the temperature is increased.

Lin, Shi-Zeng; Koshelev, Alexei E.

2013-06-01

380

Numerical simulation of combined thermal and mass transport in a square lid-driven cavity  

Microsoft Academic Search

The aim of this study was to investigate steady mixed convection in a square lid-driven cavity under the combined buoyancy effects of thermal and mass diffusion. The transport equations were solved numerically using the Galerkin weighted residual method. The heat and mass transfer rates were examined using several operational dimensionless parameters, such as the Richardson number Ri, Lewis number Le

Abdalla M. Al-Amiri; Khalil M. Khanafer; Ioan Pop

2007-01-01

381

XUV cavity and pumping optics  

Microsoft Academic Search

Two types of reflectors, selective multilayer mirrors and broadband concave mirrors with sliding modes, are considered for use in XUV cavities. Both of these reflector types can be used with back-reflection of XUV beams to yield efficiencies of tens of percent. An optic which is an analogue of the ideal optical concentrators used in solar physics can be employed in

A. V. Vinogradov

1986-01-01

382

On the collapse of cavities  

NASA Astrophysics Data System (ADS)

The collapse of a single cavity, or a cloud of bubbles has several physical consequences when in proximity to a structure or resident within a material during deformation. The earliest recognized of these was cavitation erosion of the propellers of steam ships. However, other processes include the rapid collapse of cavities leading to hot spots in explosives from which reaction ensues, or the more recent phenomenon of light generation by oscillating single bubbles or clouds. In the collapse of a cavity, the least considered but the most important mechanism is asymmetric closure. One of the consequences of this is the formation of jets leading to local high pressures and shears that result in the damage or reaction mechanisms observed. The challenge for the future remains in understanding the effects of cloud cavitation since it is likely that only one bubble in perhaps millions in a cloud catalyses an event. The review follows the author's work in the understanding of shock-induced cavity collapse and highlights several results which indicate the importance of this problem in a variety of fields.

Bourne, N. K.

383

Entanglement evolution in cavity QED  

Microsoft Academic Search

We investigate the evolution of entanglement in a strongly coupled cavity QED optical system when the driving field is weak enough that the steady state value of the intracavity photon number is less than the saturation photon number. We use a cross correlation between the transmitted intensity and the fluorescence of the atoms into modes other than that of the

D. L. Freimund; P. R. Rice; J. Gea-Banacloche

2005-01-01

384

Hydrofracture from a Growing Cavity.  

National Technical Information Service (NTIS)

The Los Alamos KRAK code has been used to calculate fracturing away from the growing cavity formed by a nuclear detonation. In the 55 ms before rebound, the stress in the surrounding rock is decreasing, and conditions for fracture propagation are good. Du...

T. D. Kunkle B. J. Travis

1981-01-01

385

Superconducting cavities for particle accelerators  

Microsoft Academic Search

RF Superconductivity has become an important technology for particle accelerators for high energy physics, nuclear physics, and free electron lasers. More than 100 MVolts of Superconducting RF (SRF) cavities have been installed in accelerators for heavy ions and operated at gradients of 2-3 MV\\/m in excess of 105 hours. More than 500 MVolts are installed in electron accelerators and operated

H. Padamsee

1992-01-01

386

ADPF spoke cavity cryomodule concept  

SciTech Connect

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

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

2001-01-01

387

An in vitro and in vivo analysis of fibrin glue use to control bone morphogenetic protein diffusion and bone morphogenetic protein–stimulated bone growth  

Microsoft Academic Search

Background contextRecombinant human bone morphogenetic protein-2 (rh-BMP2) has become popular for augmenting spine fusion in the lumbar and cervical spine. Concerns exist, however, over bone morphogenetic protein (BMP)-stimulated soft-tissue swelling and bone growth stimulation in areas where bone is not desired, especially as the material “leaks” into such spaces. The most detrimental effects of such leakage might be airway compromise,

Vikas V. Patel; Li Zhao; Pamela Wong; Ben B. Pradhan; Hyun W. Bae; Linda Kanim; Rick B. Delamarter

2006-01-01

388

Cavity QED with atomic ensembles  

NASA Astrophysics Data System (ADS)

Cavity Quantum Electrodynamics has long been a proving grounds for the study of the interaction of light with matter. Historically the objective has typically been to couple one atom to one photon as strongly as possible. While this endeavor has yielded a variety of beautiful and groundbreaking results, we take a different approach. Inspired by the quantum repeater scheme of Duan, Lukin, Cirac and Zoller, we have built a cavity-ensemble experiment, where the strong coupling between the light and the matter is achieved via the combination of the resonant enhancement of a cavity and a collective enhancement of an ensemble. We investigate the capabilities and limitations of such an approach through a number of experiments. The first experiment we describe is a very-high-quality source of photon pairs of opposite polarization, but otherwise nearly-identical spectral properties. We proceed to a high-fidelity single photon source, and carefully investigate the decoherence mechanisms that limit the performance of such a system. Next we present the cavity-mediated transfer of a single collective excitation between atomic ensembles, and deterministic entanglement generation. Lastly, we present a heralded, polarization preserving quantum memory. All of these experiments depend critically on the strong light-matter coupling afforded by the cavity-ensemble interaction, and require increasingly more sophisticated state control of the atoms. Finally, we describe our new apparatus, combining a relatively long, high-finesse optical resonator with a 2microm dipole trap. We focus on the technical details of stabilizing the narrow resonator, and discuss briefly a proposal for high efficiency Quantum Non-Demolition photon detection. We conclude with preliminary data demonstrating single-atom detection.

Simon, Jonathan

389

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

390

Scattering Matrix Synthesis Using Multiport Cavities.  

National Technical Information Service (NTIS)

The necessary and sufficient conditions are established on the scattering matrix for an n-port to be realizable as a cascade of multiport cavities having proportional ports coupled through circulators. Design equations, yielding cavity dimensions, are giv...

K. A. Zaki R. W. Newcomb

1973-01-01

391

Hydrogen Masers with Cavity Frequency Switching Servos.  

National Technical Information Service (NTIS)

The stability of the free-running hydrogen maser is limited by pulling of the unperturbed hydrogen transition frequency due to instability of the cavity resonance frequency. Two automatic approaches to cavity stabilization have been used successfully in f...

H. B. Owings H. E. Peters P. A. Koppang

1990-01-01

392

Compact Microwave Cavity for Hydrogen Atomic Clock.  

National Technical Information Service (NTIS)

A summary is presented that introduces the compact microwave cavity used in the hydrogen atomic clock. Special emphasis is placed on derivation of theoretical calculating equations of main parameters of the microwave cavity. A brief description is given o...

D. Zhang Y. Zhang Y. Fu Y. Zhang

1992-01-01

393

Equalizer Cavity with Independent Amplitude Control.  

National Technical Information Service (NTIS)

This report describes an equalizer cavity apparatus which is directionally coupled to a rectangular waveguide utilizes a circular waveguide with an adjustable RF absorber therein to lower the quality factor, Q, of the equalizer cavity. (Author)

H. L. Thal

1982-01-01

394

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

395

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

396

DIFFUSION PUMP  

DOEpatents

A high-vacuum diffusion pump is described, featuring a novel housing geometry for enhancing pumping speed. An upright, cylindrical lower housing portion is surmounted by a concentric, upright, cylindrical upper housing portion of substantially larger diameter; an uppermost nozzle, disposed concentrically within the upper portion, is adapted to eject downwardly a conical sheet of liquid outwardly to impinge upon the uppermost extremity of the interior wall of the lower portion. Preferably this nozzle is mounted upon a pedestal rising coaxially from within the lower portion and projecting up into said upper portion. (AEC)

Levenson, L.

1963-09-01

397

Understanding cavity resonances with intracavity dispersion properties  

SciTech Connect

We experimentally study the strongly coupled three-level atom-cavity system at both cavity and coupling frequency detuning cases. Side peak splitting and anti-crossing-like phenomena are observed under different experimental conditions. Intracavity dispersion properties are used to explain qualitatively the complicated cavity resonance structures in the composite system of inhomogeneously broadened three-level atoms inside an optical ring cavity with relatively strong driving intensities.

Sheng Jiteng; Wu Haibin; Mumba, M.; Gea-Banacloche, J.; Xiao Min [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

2011-02-15

398

Beam loading in magnicon deflection cavities  

Microsoft Academic Search

Analysis of the beam-deflection cavity interaction in a magnicon is presented and compared with experiment. For a driven cavity a dispersion relation is obtained wherein the interaction modifies the cold-cavity quality factor and the resonance frequency. In terms of a lumped-parameter equivalent circuit the interaction corresponds to a complex-valued beam admittance Yb in parallel with the cavity admittance. The response

B. Hafizi; Steven H. Gold

1997-01-01

399

Multipacting analysis for JLAB ampere class cavities  

Microsoft Academic Search

JLAB's ampere class 5-cell cavities require a moderate accelerating gradient (16.7 â 20MV\\/m). Electron multipacting activity in the machine operating range can degrade the expected performance. A survey was conducted in the area of multipacting analysis for beta=1 electron cavity shapes, including options for the new high current cavity shape. The results obtained provided useful guidance to the final cavity

Genfa Wu; Mircea Stirbet; Haipeng Wang; Robert Rimmer; Evan Donoghue

2005-01-01

400

Multipacting analysis for JLAB ampere class cavities  

SciTech Connect

JLAB's ampere class 5-cell cavities require a moderate accelerating gradient (16.7 {approx} 20MV/m). Electron multipacting activity in the machine operating range can degrade the expected performance. A survey was conducted in the area of multipacting analysis for beta=1 electron cavity shapes, including options for the new high current cavity shape. The results obtained provided useful guidance to the final cavity shape adopted and to its expected performance.

Genfa Wu; Mircea Stirbet; Haipeng Wang; Robert Rimmer; Evan Donoghue

2005-07-10

401

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

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

1996-01-01

402

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

403

Diffusion-controlled dendritic solidification  

NASA Astrophysics Data System (ADS)

A number of experiments have been carried out on constrained dendrite growth from metals of four transparent succinonitrile-based model alloys under the optical microscope and Al-Cu metal alloys during directional solidification, respectively. Tip temperatures (TTs), tip compositions (TCs), and the effective solute distribution coefficients corresponding to the tip radii are measured under various growth conditions. The results are compared with Trivedi's pure diffusion-controlled model for constrained dendritical growth. It is concluded that TT and TC are two basic parameters of dendritic growth which indicate the departure from local equilibrium at the growth front. The variation tendency of TT and tip TC with growth velocity at fixed temperature gradient shows a good correlation with theory. Trivedi's theoretical model fits the experimental results for tip radii well for three SCN-based alloys, but a discrepancy is found for SCN-Borneol.

Huang, Tao; Mao, Xiemin; Zhou, Yaohe; Lu, Deyang; Mao, Zhiying

1988-04-01

404

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

405

Quantum teleportation with atoms trapped in cavities  

Microsoft Academic Search

We propose a scheme to implement the quantum teleportation protocol with single atoms trapped in cavities. The scheme is based on the adiabatic passage and the polarization measurement. We show that it is possible to teleport the internal state of an atom trapped in a cavity to an atom trapped in another cavity with the success probability of 1\\/2 and

Jaeyoon Cho; Hai-Woong Lee

2004-01-01

406

In-Cavity Laser Raman Spectroscopy.  

National Technical Information Service (NTIS)

An external cavity arrangement can work with simple metal mirrors, perpendicular sample cell windows and with the laser and sample cavity on non-rigid tables separated by a large distance. The simplicity of such an external cavity may encourage other expe...

R. L. Schwiesow N. L. Abshire

1971-01-01

407

Power Coupler for the ILC Crab Cavity.  

National Technical Information Service (NTIS)

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. Sim...

A. Dexter B. Burt C. Beard P. A. Maintosh R. Jenkins

2007-01-01

408

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

Microsoft Academic Search

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

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

409

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

410

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

411

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 cavityâa region of the body that is the focus of laparoscopic surgeryâas 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

412

Structure of Cusp Diamagnetic Cavities  

NASA Astrophysics Data System (ADS)

While in the cusp region, POLAR regularly observes large (up to 6 RE) cavities characterized by depressed magnetic field and increased plasma pressure. The frequent occurance and apparent stability of these structures implies a pressure balance between the plasma inside and the field outside. We investigate this balance, using pressures derived from the HYDRA and MFE instruments and composition information from CAMMICE MICS, for multiple crossings of the cusp. Our results suggest that small-scale physics drives the structure of these regions.

Niehof, J.; Fritz, T.; Friedel, R.; Chen, J.

2005-05-01

413

Ferrite-filled cavity resonators  

Microsoft Academic Search

An approximation technique is developed for the electromagnetic resonances and electric fields inside a cavity of arbitrary\\u000a shape whose walls are perfectly conducting and which is filled with a lossless ferrite. Operator notation is introduced and\\u000a it is proved that the operator for this problem is self-adjoint. A variational expression is introduced and this functional\\u000a is minimized by employing the

D. A. Taggart; F. W. Schott

1972-01-01

414

Neoplasms of the Sinonasal Cavities  

Microsoft Academic Search

Many different types of malignant tumors arise within the sinonasal cavities. These tumors constitute less than 1% of all\\u000a malignant neoplasms. The incidence of these tumors shows geographical differences, being clearly higher in parts of Africa\\u000a and Japan than in the US. Sinonasal carcinoma is a disease mainly occurring in the age range of 50–70 years, although some\\u000a tumor types

Robert Hermans

415

Microwave energy storage in resonant cavities  

SciTech Connect

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

Alvarez, R.A.

1983-02-01

416

Image transmission through a stable paraxial cavity  

SciTech Connect

We study the transmission of a monochromatic 'image' through a paraxial cavity. Using the formalism of self-transform functions, we show that a transverse degenerate cavity transmits the self-transform part of the image, with respect to the field transformation over one round-trip of the cavity. This formalism gives insight into the understanding of the behavior of a transverse degenerate cavity, complementary to the transverse mode picture. An experiment of image transmission through a hemiconfocal cavity shows the interest of this approach.

Gigan, Sylvain; Lopez, Laurent; Treps, Nicolas; Maitre, Agnes; Fabre, Claude [Laboratoire Kastler-Brossel, Universite Pierre et Marie Curie, Case 74, 75252 Paris cedex 05 (France)

2005-08-15

417

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

418

Superconducting cavities for particle accelerators  

NASA Astrophysics Data System (ADS)

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

Padamsee, H.

1992-02-01

419

Cavity solitons in semiconductor devices  

NASA Astrophysics Data System (ADS)

Cavity solitons appear as bright spots in the transverse intensity profile. They are similar to spatial solitons, but arise in dissipative systems. Here we consider a broad area vertical cavity resonator, driven by an external coherent field, at room temperature. The active material is constituted either by bulk GaAs, or by a Multiple Quantum Well GaAs/AlGaAs structure (MQW). A general model valid for both configurations is presented and a set of nonlinear dynamical equations is derived. The linear stability analysis of the homogeneous steady states is performed in a general form, holding for the two cases. Then, the nonlinear susceptibilities are specified: in the bulk case, we basically work in the free-carrier approximation, with some phenomenological corrections, such as the Urbach tail and the band-gap renormalization. For the bulk case, some numerical results concerning spatial pattern formation and cavity solitons are given. In the MQW case, on the contrary, we derive a full many-body theory, with the Coulomb enhancement treated in the Pade approximation.

Brambilla, Massimo; Lugiato, Luigi A.; Maggipinto, Tommaso; Spinelli, Lorenzo; Tissoni, Giovanna

2000-07-01

420

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

421

Effects of cavities in the bacterial reaction center  

SciTech Connect

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

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

1995-12-31

422

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

423

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

2010-05-01

424

Highly stable piezoelectrically tunable optical cavities  

NASA Astrophysics Data System (ADS)

We have implemented highly stable and tunable frequency references using optical high finesse cavities which incorporate a piezo actuator. As piezo material we used ceramic PZT, crystalline quartz, or PZN-PT single crystals. Lasers locked to these cavities show a relative frequency stability better than 1× 10^{-14}, which is most likely not limited by the piezo actuators. The piezo cavities can be electrically tuned over more than one free spectral range (>1.5 GHz) with only a minor decrease in frequency stability. Furthermore, we present a novel cavity design, where the piezo actuator is prestressed between the cavity spacer components. This design features a hermetically sealable intra cavity volume suitable for, e.g., cavity enhanced spectroscopy.

Möhle, Katharina; Kovalchuk, Evgeny V.; Döringshoff, Klaus; Nagel, Moritz; Peters, Achim

2013-05-01

425

Shape Determination for Deformed Electromagnetic Cavities  

SciTech Connect

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

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

2007-12-10

426

Low-lying bifurcations in cavity quantum electrodynamics  

SciTech Connect

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

Armen, M. A.; Mabuchi, H. [Physical Measurement and Control 266-33, California Institute of Technology, Pasadena, California 91125 (United States)

2006-06-15

427

Local deposition fractions of ultrafine particles in a human nasal-sinus cavity CFD model.  

PubMed

Ultrafine particle deposition studies in the human nasal cavity regions often omit the paranasal sinus regions. Because of the highly diffusive nature of nanoparticles, it is conjectured that deposition by diffusion may occur in the paranasal sinuses, which may affect the residual deposition fraction that leaves the nasal cavity. Two identical CFD models of a human nasal cavity, one with sinuses and one without, were reconstructed from CT-scans to determine the uptake of ultrafine particles. In general, there was little flow passing through the paranasal sinuses. However, flow patterns revealed that some streamlines reached the upper nasal cavity near the olfactory regions. These flow paths promote particle deposition in the sphenoid and ethmoid sinuses. It was found that there were some differences in the deposition fractions and patterns for 5 and 10 nm particles between the nasal-sinus and the nasal cavity models. This difference is amplified when the flow rate is decreased and at a flow rate of 4 L/min the maximum difference was 17%. It is suggested that evaluations of nanoparticle deposition should consider some deposition occurring in the paranasal sinuses especially if flow rates are of concern. PMID:22746399

Ge, Qin Jiang; Inthavong, Kiao; Tu, Ji Yuan

2012-07-01

428

Growth with regulation in random environment  

Microsoft Academic Search

The diffusion model for a population subject to Malthusian growth is generalized to include regulation effects. This is done by incorporating a logarithmic term in the regulation function in a way to obtain, in the absence of noise, an S-shaped growth law retaining the qualitative features of the logistic growth curve. The growth phenomenon is modeled as a diffusion process

R. M. Capocelli; L. M. Ricciardi

1974-01-01

429

Diffusion Path Theorems for Ternary Diffusion Couples  

NASA Astrophysics Data System (ADS)

A review is given of 17 theorems concerning diffusion paths in ternary diffusion couples published by Kirkaldy and Brown in 1963. An additional 11 theorems are given herein that were taken from work published on diffusion paths after that time. The new theorems are concerned primarily with diffusion paths that result from crossing multiple-phase regions in an interdiffusion zone. The theorems describe a method for classifying microstructural boundaries between the regions and a catalog of diffusion path features that are unique to each type of boundary. In addition, a proposal is given for how to plot diffusion paths in quaternary and higher order systems.

Morral, John E.

2012-10-01

430

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

431

Melting heat transfer of liquid ice in a rectangular cavity with a heated vertical wall  

SciTech Connect

The melting characteristics of liquid ice in a rectangular cavity were studied experimentally. The liquid ice, mixture of ice particles and ethylene-glycol aqueous solution, was heated from one of the vertical walls of the cavity. The shape of the mush-liquid interface, melting rate, and local/mean heat-transfer coefficient at the heated vertical wall were observed and measured under a variety of conditions of heat flux and initial concentration of the aqueous binary solution. It was found that the formation of double-diffusive layers based on the thermal and solutal buoyancy forces exerted a great influence on the melting process of the liquid ice.

Fukusako, Shoichiro; Yamada, Masahiko; Kim, Myounghwan (Hokkaido Univ. (Japan). Dept. of Mechanical Engineering)

1993-12-01

432

Gonadotropin-releasing hormone agonist binding in tiger salamander nasal cavity.  

PubMed

Binding of the iodinated gonadotropin-releasing hormone (GnRH) agonist, buserelin, was examined in the nasal cavities of tiger salamanders using in vitro autoradiography. Binding of [125I]buserelin was seen within the chemosensory epithelium of the main nasal cavity and Jacobson's (vomeronasal) organ. Highest levels of binding were observed over the chemosensory neuron dendrites. Given the apparent lack of GnRH-immunoreactive fibers within the chemosensory epithelium as we have observed in a previous study, these observations suggest that GnRH may diffuse from fibers in the lamina propria of the chemosensory mucosa into the sensory epithelium to modulate chemosensory reception. PMID:8247354

Wirsig-Wiechmann, C R; Jennes, L

1993-10-01

433

Ionizing radiation dose distribution produced inside a canonical cavity by direct e-beam excitation  

SciTech Connect

Reliable dosimetry methods have been developed to map relativistic electrons that have been injected into a generic cavity. These measuring techniques are: (1) thermoluminescent dosimeters (TLDs) combined with photodiodes yielding dose rate; (2) TLD telescopes yielding electron angular distributions; and (3) TLD mosaic arrays yielding rough energy spectra. Total dose, dose rate, electron angular distribution and current density measurements have been obtained during electromagnetic excitation of a canonical cavity with diffuse electron beam (e-beam) bombardment. A theoretical interpretation of the dose rate and electron current density measurements is presented.