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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

Diffusion of radon gas in soil cavities  

SciTech Connect

To assess the potential radon hazard of a new home construction site and the steps (if any) that should be taken to mitigate that hazard, the soil pore gas radon source strength S (i.e., the number of radon atoms emitted into a unit volume of pore gas per unit time), the pore gas radon diffusion length L, and the soil porosity p must be known. Methods exist for measuring the steady-state soil pore gas radon concentration. The purposes of this paper are to analyze the kinetics of the radon concentration in a cavity in the soil, to determine the parameters that affect the kinetics, and to establish and analyze an in situ method for measuring S, L, and p.

Jarzemba, M.S.; Blue, T.E.; Mervis, J.; Holcomb, D.

1989-01-01

3

[Diffuse primary malignant mesothelioma in abdominal cavity].  

PubMed

Two cases of diffuse malignant mesothelioma of abdominal cavity were analysed. These tumors arise from the peritoneum and are also found in the parietal and visceral pleura, pericardium and in vaginal tunic. All of them, infra or supra-diaphragmatic, are associated with asbestos exposure in at least 80% of cases. It is difficult to explain how inhaled asbestos induces peritoneal neoplasms. This aspects become very important in the diagnostic, basically why it is done at laparotomy or laparoscopy. When was proceed the biopsy of the lesions, and occasionally by identification of malignant mesothelial cells in ascitic fluid. In this two cases exposed considerations about the advanced phase of diagnostic are made, the diagnostic was performed in the majority of the collected cells, showing the advanced stage of the disease. At that time of diagnosis we observed poor evolution. We call attention to the importance of precancer diagnosis, the best chance to treatment options, always based on surgical resections, radiation or chemotherapy alone or combined. If the radical surgery is not possible, this patients must be treated by chemotherapy or radiotherapy, defined after complete staging of the disease. PMID:9611294

D'Albuquerque, L A; Padilla, J M; Rodrigues, A L; Souza, M V; Quireze Júnior, C; Meniconi, M T; Copstein, J L; dos Santos Júnior, E D; de Melo, C R; Santo, G C; de Oliveira e Silva, A

1997-01-01

4

Fabrication of whispering gallery mode cavity using crystal growth  

NASA Astrophysics Data System (ADS)

We developed a method for fabricating crystalline whispering gallery mode cavities based on laser-heated pedestal growth. We fabricated sapphire cavities and obtained a Q factor of 1.6 × 104 with a cavity whose radius was about 120 ?m. We showed numerically that the cross sectional shape of the cavity is sensitive to the cavity Q, and we controlled it by changing the growth condition in the molten zone, without significantly degrading the crystal structure.

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

2013-05-01

5

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

2014-07-01

6

Diffusion, Viscosity and Crystal Growth in Microgravity  

NASA Technical Reports Server (NTRS)

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

Myerson, Allan S.

1996-01-01

7

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

8

Physical Calculation of HTGR with a Cavity in the Framework of the Diffusion Approximation.  

National Technical Information Service (NTIS)

Methods and programs of calculation were considered within the framework of diffusion approximation of HTGR with large cavity and their approbation was performed using data on KAHTER critical assemblies. Calculation of elementary cells was conducted accor...

A. V. Zhirnov A. S. Kaminskij

1985-01-01

9

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

10

Density cavity in magnetic reconnection diffusion region in the presence of guide field  

NASA Astrophysics Data System (ADS)

Understanding the structure of the diffusion region of magnetic reconnection is crucial to pinpoint the mechanism of energy conversion from magnetic field to plasma. Characteristics of a diffusion region with guide field (i.e., component reconnection) may be significantly different from those of a diffusion region without guide field (i.e., antiparallel reconnection). In this study, we attempt to understand the structure of a diffusion region with guide field by studying the density cavity along separatrix. We present an event in which a density cavity was detected by the Cluster spacecraft in a diffusion region in the presence of guide field. The cavity was located around the separatrix region on the southern hemisphere of the neutral sheet and earthward of the X-line and was coincident with strong magnetic field compression. The width of the cavity was on the ion inertial scale. This cavity contained a relatively strong antiparallel current, which was mainly contributed by parallel streaming electrons with energy of 1-10 keV. Enhancements of lower hybrid wave and electromagnetic whistler wave were observed inside the cavity. These waves are probably excited by parallel streaming electrons along separatrix via electron beam instability. Two-dimensional electromagnetic particle-in-cell simulation was employed to study the structure of the density cavity. The location and scale of the cavity and the signature of electric current and electron velocity are consistent with our observations. It is found that there was displacement between the position of electron density minimum and out-of-plane magnetic field maximum in reconnection with guide field. However, this displacement is much less than that in reconnection without guide field. There was no significant acceleration for electrons to reach energy larger than 30 keV at the cavity.

Zhou, M.; Pang, Y.; Deng, X. H.; Yuan, Z. G.; Huang, S. Y.

2011-06-01

11

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

12

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

NASA Astrophysics Data System (ADS)

A simplified theoretical model was developed for the thermal-wave cavity (TWC) technique in this study. This model takes thermal radiation into account and can be employed for absolute measurements of the thermal diffusivity of gas and liquid samples without any knowledge of geometrical and thermal parameters of the components of the TWC. Using this model and cavity-length scans, thermal diffusivities of air and distilled water were accurately and precisely measured as (2.191 ± 0.004) × 10-5 and (1.427 ± 0.009) × 10-7 m2 s-1, respectively, in very good agreement with accepted literature values.

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

2013-12-01

13

Diffuse glioma growth: a guerilla war  

PubMed Central

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

Idema, Albert J.; Wesseling, Pieter

2007-01-01

14

Absolute CH concentration measurements by cavity ring-down spectroscopy in an atmospheric diffusion flame  

Microsoft Academic Search

Absolute concentrations of CH radical are reported for the first time in an atmospheric diffusion flame. Measurements are performed by cavity ring-down (CRD) spectroscopy by probing the C–X system of CH around 315 nm. We used standard 308 nm coated mirrors also suitable for OH CRD measurements. Absolute concentrations are obtained from integrated absorption measurements after a deconvolution procedure. Peak

X. Mercier; P Jamette; J. F Pauwels; P Desgroux

1999-01-01

15

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

16

Volume Diffusion Growth Kinetics and Step Geometry in Crystal Growth  

NASA Technical Reports Server (NTRS)

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

Mazuruk, Konstantin; Ramachandran, Narayanan

1998-01-01

17

Measurements of thermal diffusivity of water-alcohol mixtures using a thermal-wave resonator cavity  

NASA Astrophysics Data System (ADS)

A photothermal technique for ultra-high resolution measurements of thermal diffusivity of liquid mixtures was developed. Frequency scan experiments using the thermal-wave resonator cavity (TWRC) method [1] were performed. A theoretical model describing the one-dimensional temperature field within the cavity was developed. Comparison between the theoretical and experimental data for signal amplitude and phase in water shows excellent agreement. To achieve the ultra-high sensitivity of the measurements for liquid mixtures at low concentrations we modified the thermal-wave resonator cavity method coupling it with a signal common-mode rejection demodulation (CMRD) scheme [2]. This non-conventional technique has shown sensitivity of the photothermal signal to methanol in water at the level of 0.25% by volume.

Matvienko, A.; Mandelis, A.

2005-06-01

18

Diffuse large B-cell lymphoma of the nasal cavity presenting as abducens nerve palsy.  

PubMed

An 87-year-old man presented with a 1-week history of transient facial numbness, followed by the onset of left diplopia 1 month later. In the neurological examination, he was found to have left abducens nerve palsy. A brain MRI showed an infiltrative lesion invading the left posterior nasal cavity and pterygopalatine fossa, and extending into the left paracavernous region. The histological diagnosis was diffuse large B-cell lymphoma. We report an unusual case of diffuse large B-cell lymphoma occurring in the sinonasal tract with unilateral abducens nerve palsy presenting as an early feature. PMID:24220442

Kang, Ju Wan; Kim, Jeong Hong

2013-11-01

19

Reduction of Beam Breakup Growth by Cavity Cross-Couplings in Recirculating Accelerators.  

National Technical Information Service (NTIS)

It is shown that cross-coupling among cavities may reduce beam breakup (BBU) growth in a recirculating accelerator. The main reason for this growth reduction appears to be the sharing of the deflecting mode energy among coupled cavities. The result is bas...

D. Chernin D. Colombant Y. Y. Lau

1990-01-01

20

Laser cooling of neutral atoms by red-shifted diffuse light in an optical integral sphere cavity.  

National Technical Information Service (NTIS)

In this paper, we report a cooling and deceleration experiment of a thermal beam by using a nearly resonant red-shifted diffuse light in an optical integral sphere cavity. With this red-shifted diffuse light, a part of thermal sodium atoms is cooled to 38...

Wang Yuzhu Chen Hongxin Cai Weiquan Liu Liang Zhou Shanyu

1994-01-01

21

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

DOEpatents

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

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

1995-01-01

22

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

23

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

NASA Astrophysics Data System (ADS)

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

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

2000-07-01

24

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

25

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

NASA Technical Reports Server (NTRS)

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

Smialek, J. L.; Gibala, R.

1983-01-01

26

Lightning, IT diffusion and economic growth across US states  

Microsoft Academic Search

Empirically, a higher frequency of lightning strikes is associated with slower growth in labor productivity across the 48 contiguous US states after 1990; before 1990 there is no correlation between growth and lightning. Other climate variables (e.g., temperature, rainfall and tornadoes) do not conform to this pattern. A viable explanation is that lightning influences IT diffusion. By causing voltage spikes

Thomas Barnebeck Andersen; Jeanet Bentzen; Carl-Johan Dalgaard; Pablo Selaya

2011-01-01

27

Lightning, IT Diffusion and Economic Growth across US States  

Microsoft Academic Search

Empirically, a higher frequency of lightning strikes is associated with slower growth in labor productivity across the 48 contiguous US states after 1990; before 1990 there is no correlation between growth and lightning. Other climate variables (e.g., temperature, rainfall and tornadoes) do not conform to this pattern. A viable explanation is that lightning influences IT diffusion. By causing voltage spikes

Thomas Barnebeck Andersen; Jeanet Bentzen; Carl-Johan Dalgaard; Pablo Selaya

2009-01-01

28

Reduction of beam breakup growth by cavity cross-couplings in recirculating accelerators  

NASA Astrophysics Data System (ADS)

1407_54It is shown that cross-coupling among cavities may reduce beam breakup (BBU) growth in a recirculating accelerator. The main reason for this growth reduction is the sharing of the deflecting mode energy among coupled cavities. This result is based on a numerical study of the proof-of-principle experiment currently planned for the spiral line induction accelerator (SLIA, 35 ns, 10 kA, 8.5 MeV). Reduction of BBU amplitude by factors of several hundreds is also predicted for a SLIA upgrade (35 ns, 10 kA, 25 MeV) which consists of a 7-turn, 70-cavity system. Various issues are addressed.

Colombant, Denis G.; Lau, Yue Y.; Chernin, David P.

1991-04-01

29

Neuronal growth as diffusion in an effective potential  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

30

Accurate flux estimation during molecular beam epitaxy growth of vertical-cavity surface-emitting lasers  

Microsoft Academic Search

We report an in-situ method for accurate flux monitoring in gas-source molecular-beam epitaxy (GSMBE) growth of vertical-cavity surface-emitting lasers (VCSELs). The method uses a single reflectivity spectrum measurement on the incomplete structure to estimate the values of the effusion cell fluxes (and therefore the thickness and the composition of the different layers) used for the growth of the first part

L. Couturier; P. Grosse; A. Grouillet; A. Chenevas-Paule

1996-01-01

31

Bubble growth in mold cavities during microcellular injection molding processes  

Microsoft Academic Search

Bubble nucleation and growth are the key steps in polymer foam generation processes. The mechanical properties of foam polymers\\u000a are closely related to the size of the bubbles created inside the material, and most existing analysis methods use a constant\\u000a viscosity and surface tension to predict the size of the bubbles. Under actual situations, however, when the polymer contains\\u000a gases,

Yongrak Moon; Kyoung-soo Lee; Sung W. Cha

2009-01-01

32

Literature Dynamics: Studies on Growth, Diffusion, and Epidemics.  

ERIC Educational Resources Information Center

This review provides a summary of the main theoretical arguments and empirical results available in literature dynamics. Discusses studies of growth, diffusion of information, epidemic theory, and fast-growing literatures. Deals with methodological problems of publication counts, the time factor, and converging indicators, and discusses two…

Tabah, Albert N.

1999-01-01

33

Surface Diffusion: The Low Activation Energy Path for Nanotube Growth  

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

34

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

PubMed Central

Primary lymphomas of the oral cavity are rare and the most frequent type is diffuse large B-cell lymphoma (DLBCL). Recently, several reports have highlighted the value of classifying DLBCL into prognostically important subgroups, namely germinal center B-cell like (GCB) and non-germinal center B-cell like (non-GCB) lymphomas based on gene expression profiles and by immunohistochemical expression of CD10, BCL6 and MUM-1. GCB lymphomas tend to exhibit a better prognosis than non-GCB lymphomas. Studies validating this classification have been done for DLBCL of the breast, CNS, testes and GI tract. Therefore we undertook this study to examine if primary oral DLBCLs reflect this trend. We identified 13 cases (age range 38–91 years) from our archives dating from 2003–09. IHC was performed using antibodies against germinal center markers (CD10, BCL6), activated B-cell markers (MUM1, BCL2) and Ki-67 (proliferation marker). Cases were sub-classified as GCB subgroup if CD10 and/or BCL6 were positive and MUM-1, was negative and as non-GCB subgroup if CD10 was negative and MUM-1 was positive. Immunoreactivity was noted in 2/13 cases for CD10, in 12/13 for BCL6, in 8/13 for MUM-1, and in 6/13 for BCL2. Therefore, 8/13 (58%) were sub-classified as non-GCB DLBCLs and 5/13 (42%) as GCB subgroup. All tumors showed frequent labeling with Ki-67 (range 40–95%). Four of the 8 patients with non-GCB subgroup succumbed to their disease, with the mean survival rate of 16 months. Two patients in this group are alive, one with no evidence of disease and another with disease. No information was available for the other 3 patients in this group. Four of the 5 patients in the GCB subgroup were alive with no evidence of disease and one patient succumbed to complications of therapy and recurrent disease after 18 months. In conclusion, our analysis shows that primary oral DLBCL predominantly belongs to the non-GCB subgroup, which tends to exhibit a poorer prognosis. These findings could allow pathologists to provide a more accurate insight into the potential aggressive behavior and poorer prognosis of these lymphomas.

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

2010-01-01

35

Cavity ring-down measurements of OH radical in atmospheric premixed and diffusion flames  

Microsoft Academic Search

Cavity ring-down spectroscopy (CRDS) is tested in two atmospheric burners: a premixed flat flame burner and a Wolfhard–Parker burner. The quantitative nature and the spatial resolution of CRDS are compared with those of laser-absorption and laser-induced fluorescence by recording OH concentration profiles. Losses per pass due to the abundant OH sample in the CRD cavity need to be carefully controlled

X. Mercier; E Therssen; J. F Pauwels; P Desgroux

1999-01-01

36

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

37

Solutions of the full Navier-Stokes equations for reacting three-dimensional chemical laser cavity and diffuser flow fields  

NASA Astrophysics Data System (ADS)

This paper addresses a computer model that is capable of predicting chemical laser performance and pressure recovery for complex three-dimensional chemical laser configurations. The time-dependent numerical technique allows for complex arbitrary geometrical boundaries, the solution of the full three-dimensional Navier-Stokes equations with a turbulent kinetic energy model, and chemical vibrational and rotational nonequilibrium chemistry (including gain calculations). Calculations are compared with measurements for both (1) a three-dimensional viscous chemical laser cavity flow with swirl-inducing trip injection, and (2) a radial vane diffuser with multiple internal shock/boundary layer interactions.

Hendricks, W. L.; Mikatarian, R. R.; Gross, B. J.; Rapagnani, N. L.

1981-06-01

38

Nonequilibrium Models for Diffusive Cavitation of Grain Interfaces.  

National Technical Information Service (NTIS)

Existing models for the diffusive growth of voids on grain interfaces, at elevated temperature, are for the most part based on quasi-equilibrium assumptions: surface diffusion is assumed to be sufficiently rapid that the cavity has a rounded, equilibrium ...

T. J. Chuang K. I. Kagawa J. R. Rice L. B. Sills

1978-01-01

39

Random ballistic growth and diffusion in symmetric spaces  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

40

An analysis of cavity growth during open-die hot forging of Ti-6Al-4V  

NASA Astrophysics Data System (ADS)

The effect of local deformation conditions on the cavitation behavior of Ti-6Al-4V during open-die forging was quantified using optical metallography and continuum finite-element-method (FEM) analysis of pancake forgings. The observations were interpreted using meso- and microscopic-scale models, which were used to predict the average cavity size as well the size of the largest cavities. The mesoscale model gave excellent predictions of the average cavity size at different locations of the workpiece, but grossly underestimated the size of the largest cavities by an order of magnitude. On the other hand, the micromechanical model, which accounted for the effect of local colony orientation on cavity growth, was capable of predicting the size of the largest cavities very well. Because the large cavities are the most deleterious with respect to subsequent processing and service performance, it was concluded that micromechanical models should be used to design primary hot working processes in order to minimize the size and number of such cavities.

Nicolaou, P. D.; Semiatin, S. L.

2005-06-01

41

Growth characteristics of polycyclic aromatic hydrocarbons in dimethyl ether diffusion flame  

Microsoft Academic Search

The growth characteristics of polycyclic aromatic hydrocarbons (PAHs) in laminar dimethyl ether (DME) diffusion flame were investigated experimentally, and we assumed that the growth of PAHs within the flame was predominantly due to methyl addition\\/cyclization (MAC) mechanism. Methane and propane laminar diffusion flames were also investigated for comparison, and their PAHs growth characteristics had been explained by reactions concerning acetylene

Kazuhiro Hayashida; Toshio Mogi; Kenji Amagai; Masataka Arai

2011-01-01

42

Diffusion, diffusion creep and grain growth characteristics of nanocrystalline and fine-grained monoclinic, tetragonal and cubic zirconia  

Microsoft Academic Search

The experimentally measured grain size compensated diffusion creep rates are essentially identical in cubic, tetragonal and monoclinic zirconia, suggesting a similarity in the absolute magnitudes of their grain boundary diffusion coefficients. However, grain growth is substantially slower in tetragonal zirconia due to significant grain boundary segregation.

Atul H. Chokshi

2003-01-01

43

1.4-kW Nd:YAG slab laser with a diffusive closed-coupled pump cavity  

NASA Astrophysics Data System (ADS)

A high-power high-efficiency Nd:YAG slab laser with lamp pumping is developed by use of a novel diffusive closed-coupled lamp pump cavity. In cw-mode operation, 1.45 kW of output power is obtained with a slope efficiency of 5.0%. In pulsed-mode operation (50 pulses / s, 25% pulse duty), 1.4 kW of output power is obtained with a slope efficiency of 4.3%. The output power per unit volume is 45 W /cm3 . To our knowledge, these output powers and the power per unit volume are the highest obtained for the single-head Nd:YAG slab laser with lamp pumping.

Seguchi, Masaki; Kuba, Kazuki

1995-02-01

44

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

45

Ice crystal growth in a dynamic thermal diffusion chamber  

NASA Technical Reports Server (NTRS)

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

Keller, V. W.

1980-01-01

46

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

47

A bioreaction–diffusion model for growth of marine sponge explants in bioreactors  

Microsoft Academic Search

Marine sponges are sources of high-value bioactives. Engineering aspects of in vitro culture of sponges from cuttings (explants) are poorly understood. This work develops a diffusion-controlled growth model for sponge explants. The model assumes that the explant growth is controlled by diffusive transport of at least some nutrients from the surrounding medium into the explant that generally has a poorly

F. Garcia Camacho; T. Chileh; M. C. Cerón García; A. Sánchez Mirón; E. H. Belarbi; Y. Chisti; E. Molina Grima

2006-01-01

48

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

49

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth  

Microsoft Academic Search

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

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

2004-01-01

50

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

PubMed

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. PMID:12241366

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

2002-07-01

51

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

52

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

SciTech Connect

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

Gianluigi Ciovati

2005-09-15

53

Irregular growth of AlSb in solid aluminum-solid antimony diffusion couples  

Microsoft Academic Search

An investigation was made of the growth of the intermediate phase aluminum antimonide (AlSb) in solid aluminum-solid antimony\\u000a diffusion couples, AlSb being the only intermediate phase present in the equilibrum phase diagram. Most diffusion couples\\u000a were assembled from polycrystalline aluminum and antimony, but a few were made from single crystals; the diffusion couple\\u000a surfaces were prepared in a variety of

John E. Lyttle; Peter V. Dembowski; Louis S. Castleman

1971-01-01

54

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

55

Further studies on beam breakup growth reduction by cavity cross-couplings in recirculating accelerators: Effects of long pulse length and multiturn recirculation  

NASA Astrophysics Data System (ADS)

Cavity cross-coupling was recently found to reduce beam breakup (BBU) growth in a recirculating accelerator known as the Spiral LIne Induction Accelerator (SLIA). Here, we extend the analyses in two respects: long beam pulse lengths and a SLIA upgrade geometry which accelerates a 10 kA, 35 ns beam to 25 MeV via a 70-cavity, 7-turn recirculation. We found that when the beam pulse length tau exceeds the beam's transit time tau' between cross-coupled cavities, BBU growth may be worsened as a result of the cross-couplings among cavities. This situation is not unlike other long pulse recirculating accelerators when beam recirculation leads to beam breakup of a regenerative type. Thus, the advantage of BBU reduction by cavity cross-coupling is restricted primarily to beams with tau is less than tau', a condition envisioned for all SLIA geometries. For the 70-gap, 7-turn SLIA upgrade, we found that cavity cross-coupling may reduce BBU growth up to factors of a thousand when the quality factor Q of the deflecting modes are relatively high (like 100). In these high Q cases, the amount of growth reduction depends on the arrangement and sequence of beam recirculation. For Q less than or = 20, BBU growth reduction by factors of hundreds is observed, but this reduction is insensitive to the sequence of beam recirculation. The above conclusions were based on simple models of cavity coupling that have been used in conventional microwave literature.

Colombant, D.; Lau, Y. Y.

1991-09-01

56

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

NASA Astrophysics Data System (ADS)

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

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

57

From snowflake formation to growth of bacterial colonies. Diffusive patterning in azoic systems  

Microsoft Academic Search

Many phenomena display the emergence of patterns during diffusive growth, ranging from the growth of snowflake s to the aggregation of a soot particle, from oil recovery by fluid injection to solidification of metals and from the formation of a coral reef to cell differentiation during embryonic development. Is the diversity of patterns found in Nature a result of different

Eshel Ben-Jacob

1993-01-01

58

Influence of diffusion barriers on the nucleation and growth of CVD Cu for interconnect applications  

Microsoft Academic Search

Nucleation and growth behavior of Cu influence strongly the macroscopic properties of the resultant films. In this work the nucleation of CVD Cu on different underlayer materials is studied. It is found that nucleation on bare diffusion barrier surfaces leads to island growth and, therefore, bad wetting and adhesion. An enrichment of F, O and carbon was found at the

R Kröger; M Eizenberg; D Cong; N Yoshida; L. Y Chen; S Ramaswami; D Carl

2000-01-01

59

Germanium diffusion during HfO2 growth on Ge by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

The authors study the Ge diffusion during HfO2 growth by molecular beam epitaxy on differently in situ prepared germanium substrates and at different growth temperatures. While HfO2 layers grown directly on Ge do not show any germanium contamination, oxygen rich interfacial layers such as GeOx or GeOxNy partly dissolve into the HfO2 layer, giving rise to high Ge contamination (from 1% to 10%). The use of nitridated interfacial layers does not prevent Ge diffusion into the HfO2 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.

2006-09-01

60

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

Microsoft Academic Search

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

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

2008-01-01

61

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

62

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

NASA Astrophysics Data System (ADS)

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 m standoff distance. An external cavity quantum cascade laser provided tunable illumination between 7 and 8 ?m. Important differences were identified in the spectral features between specular reflection and diffuse scattering which will impact most practical testing scenarios and complicate material identification. We discuss some of the factors influencing the dependence of observed spectra on the experimental geometry.

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

2012-09-01

63

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

64

Adsorption, Diffusion and Growth Mode of ZnO Thin Film from First Principles  

NASA Astrophysics Data System (ADS)

A heteroepitaxial growth model of the ZnO film on sapphire (0001) is calculated by using a plane wave ultrasoft pseudo-potential method based on density functional theory. It is found that interfacial atoms have different diffusivity at 400°C, 600°C and 800°C. The temperature has a decisive effect on the surface and interface structures of ZnO/?-Al2O3 (0001) and on the growth mode of ZnO thin films. In the whole process of the adsorption and growth of ZnO, the diffusivity of O atoms is higher than that of Zn, and the interlayer diffusion has an important impact on the homogeneous growth of thin films. There are two growth modes of ZnO on sapphire (0001), which is further demonstrated by theoretical calculation. The growth mode at about 400°C has a character of mainly spiral-twisted growth with Zn-hexagonal symmetry structure, and it is favorable for forming the Zn-terminated surface. But in the case of 600°C, a regular in-plane growth is observed, which facilitates the O-terminated surface of the ZnO thin film. It can be observed from the calculation that the vacancies of Zn where the atomic layer is near to the ?-Al2O3 (0001) surface is more than that of O atoms.

Chun, Yang; Li, Y. R.; Yi, Yu

65

Growth of aluminum antimonide in solid aluminum-liquid antimony diffusion couples  

Microsoft Academic Search

An investigation was made of the isothermal growth of the intermediate alloy phase aluminum antimonide AlSb, at the interfaces\\u000a of diffusion couples consisting either of solid aluminum and liquid antimony or of solid aluminum and of an Sb?Al alloy slightly\\u000a supersaturated in AlSb. The diffusion anneals were carried out in the temperature range 635° to 655°C and for times up

N. Grado; L. S. Castleman

1971-01-01

66

Further studies on beam breakup growth reduction by cavity cross-couplings in recirculating accelerators: effects of long pulse length and multiturn recirculation  

NASA Astrophysics Data System (ADS)

Cavity cross-coupling was recently found to reduce beam breakup (BBU) growth in a recirculating accelerator known as the Spiral Line Induction Accelerator (SLIA). Here, we extend the analyses in two respects: long beam pulse lengths and a SLIA upgrade geometry which accelerates a 10 kA, 35 ns beam to 25 MeV via a 70 cavity, 7 turn recirculation. We found that when the beam pulse length ? exceeds the beam's transit time ?' between cross-coupled cavities. BBU growth may be worsened as a result of the cross-couplings among cavities. This situation is not unlike other long pulse recirculating accelerators where beam recirculation leads to beam breakup of a regenative type. Thus, the advantage of BBU reduction by cavity cross-coupling is restricted primarily to beams with ?cavity cross-coupling may reduce BBU growth up to factors of a thousand when the quality factor Q of the deflecting modes are relatively high (like 100). In these high Q cases, the amount of growth reduction depends on the arrangement and sequence of beam recirculation. For Q?20, BBU growth reduction by factors of hundreds is observed, but this reduction is insensitive to the sequence of beam recirculation. The above conclusions were based on simple models of cavity coupling that have been used in conventional microwave literature. Not addressed is the detail design consideration that leads to the desired degree of cavity coupling.

Colombant, D.; Lau, Y. Y.

1992-01-01

67

Electrical Activity Modulates Growth Cone Guidance by Diffusible Factors  

Microsoft Academic Search

Brief periods of electrical stimulation of cultured Xenopus spinal neurons resulted in a marked alteration in the turning responses of the growth cone induced by gradients of attractive or repulsive guidance cues. Netrin-1-induced attraction was enhanced, and the repulsion induced by myelin-associated glycoprotein (MAG) or myelin membrane fragments was converted to attraction. The effect required the presence of extracellular Ca2+

Guo-li Ming; John Henley; Marc Tessier-Lavigne; Hong-jun Song; Mu-ming Poo

2001-01-01

68

Diffusion  

NSDL National Science Digital Library

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

Consortium, The C.

2011-12-11

69

Non-linear resonance of fluids in a crystal growth cavity  

NASA Technical Reports Server (NTRS)

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

Wang, Francis C.

1996-01-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

71

Solute Layers and Double-Diffusive Interfaces during the Solidification of NH4Cl-H2O in Rectangular Cavities  

NASA Astrophysics Data System (ADS)

Flow and temperature fields during the solidification of hypereutectic and hypoeutectic NH4Cl-H2O 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 NH4Cl 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.

2010-03-01

72

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

73

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

74

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

75

Hair-Inspired Crystal Growth of HOA in Cavities of Cellulose Matrix via Hydrophobic-Hydrophilic Interface Interaction.  

PubMed

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

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

2014-06-25

76

Kinetics of diffusion-controlled growth of fayalite  

Microsoft Academic Search

The rate of growth of fayalite (Fe2SiO4) has been measured at one atmosphere total pressure, temperatures from 1000 to 1120 C, and oxygen fugacities controlled\\u000a by CO\\/CO2 gas-mixing from 10-9.9 to 10-13.0atm, chosen to span the fayalite stability field. The fine-grained polycrystalline fayalite layer was formed by reacting the\\u000a oxides FeO or Fe3O4 with a thin slice of single-crystal quartz.

D. K. Fisler; S. J. Mackwell

1994-01-01

77

Electrical activity modulates growth cone guidance by diffusible factors.  

PubMed

Brief periods of electrical stimulation of cultured Xenopus spinal neurons resulted in a marked alteration in the turning responses of the growth cone induced by gradients of attractive or repulsive guidance cues. Netrin-1-induced attraction was enhanced, and the repulsion induced by myelin-associated glycoprotein (MAG) or myelin membrane fragments was converted to attraction. The effect required the presence of extracellular Ca(2+) during electrical stimulation and appeared to be mediated by an elevation of both cytoplasmic Ca(2+) and cAMP. Thus, electrical activity may influence the axonal path finding of developing neurons, and intermittent electrical stimulation may be effective in promoting nerve regeneration after injury. PMID:11239434

Ming, G; Henley, J; Tessier-Lavigne, M; Song, H; Poo, M

2001-02-01

78

Experimental growth of åkermanite reaction rims between wollastonite and monticellite: evidence for volume diffusion control  

NASA Astrophysics Data System (ADS)

Growth rates of monomineralic, polycrystalline åkermanite (Ca2MgSi2O7) rims produced by solid-state reactions between monticellite (CaMgSiO4) and wollastonite (CaSiO3) single crystals were determined at 0.5 GPa dry argon pressure, 1,000-1,200°C and 5 min to 60 h, using an internally heated pressure vessel. Inert Pt-markers, initially placed at the monticellite-wollastonite interface, indicate symmetrical growth into both directions. This and mass balance considerations demonstrate that rim growth is controlled by transport of MgO. At 1,200°C and run durations between 5 min and 60 h, rim growth follows a parabolic rate law with rim widths ranging from 0.4 to 16.3 ?m indicating diffusion-controlled rim growth. The effective bulk diffusion coefficient D_{{eff,MgO}}^{{Ak}} is calculated to 10-15.8±0.1 m2 s-1. Between 1,000°C and 1,200°C, the effective bulk diffusion coefficient follows an Arrhenius law with E a = 204 ± 18 kJ/mol and D 0 = 10-8.6±1.6 m2 s-1. Åkermanite grains display a palisade texture with elongation perpendicular to the reaction interface. At 1,200°C, average grain widths measured normal to elongation, increase with the square root of time and range from 0.4 to 5.4 ?m leading to a successive decrease in the grain boundary area fraction, which, however, does not affect D_{{eff,MgO}}^{{Ak}} to a detectible extent. This implies that grain boundary diffusion only accounts for a minor fraction of the overall chemical mass transfer, and rim growth is essentially controlled by volume diffusion. This is corroborated by the agreement between our estimates of the effective MgO bulk diffusion coefficient and experimentally determined volume diffusion data for Mg and O in åkermanite from the literature. There is sharp contrast to the MgO-SiO2 binary system, where grain boundary diffusion controls rim growth.

Joachim, Bastian; Gardés, Emmanuel; Abart, Rainer; Heinrich, Wilhelm

2011-03-01

79

Stationary growth and unique invariant harmonic measure of cylindrical diffusion limited aggregation.  

PubMed

We prove that the harmonic measure is stationary, unique, and invariant on the interface of diffusion limited aggregation (DLA) growing on a cylinder surface. We provide a detailed theoretical analysis puzzling together multiscaling, multifractality, and conformal invariance, supported by extensive numerical simulations of clusters built using conformal mappings and on a lattice. The growth properties of the active and frozen zones are clearly elucidated. We show that the unique scaling exponent characterizing the stationary growth is the DLA fractal dimension. PMID:23006279

Marchetti, Riccardo; Taloni, Alessandro; Caglioti, Emanuele; Loreto, Vittorio; Pietronero, Luciano

2012-08-10

80

Studies of bacterial branching growth using reaction–diffusion models for colonial development  

Microsoft Academic Search

Various bacterial strains exhibit colonial branching patterns during growth on poor substrates. These patterns reflect bacterial cooperative self-organization and cybernetic processes of communication, regulation and control employed during colonial development. One method of modeling is the continuous, or coupled reaction–diffusion approach, in which continuous time evolution equations describe the bacterial density and the concentration of the relevant chemical fields. In

Ido Golding; Yonathan Kozlovsky; Inon Cohen; Eshel Ben-Jacob

1998-01-01

81

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

NASA Astrophysics Data System (ADS)

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).

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

1997-03-01

82

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

83

Introducing carbon diffusion barriers for uniform, high-quality graphene growth from solid sources.  

PubMed

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

Weatherup, Robert S; Baehtz, Carsten; Dlubak, Bruno; Bayer, Bernhard C; Kidambi, Piran R; Blume, Raoul; Schloegl, Robert; Hofmann, Stephan

2013-10-01

84

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

PubMed Central

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

2013-01-01

85

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

86

Liquid-liquid diffusion profiles in microgravity experiments, and crystal growth of the membrane protein bacteriorhodopsin  

NASA Astrophysics Data System (ADS)

Bacteriorhodopsin (BR) is a light-driven electrogenic proton pump from Halobacterium halobium. BR crystals, particularly into the third dimension, are ordered by relatively weak intermolecular bonds, possibly susceptible to disturbing solutal convection. Minimized convection is given under microgravity, e.g., during IML or EURECA space missions, but duration may not be long enough to terminate the crystal growth under microgravity. At the distal end of the PCF protein chamber, kinetics of measured protein crystal growth and of salt/protein diffusion will be demonstrated here: equilibrium of salt diffusion and of BR crystal growth is reached within a time span of 100 to 200 h; similar values are predicted by the CRYSLIB computer program for the CRYOSTAT protein chamber.

Wagner, Gottfried; Linhardt, Rudolf

1991-03-01

87

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

88

Efficacy and safety of selenium nanoparticles administered intraperitoneally for the prevention of growth of cancer cells in the peritoneal cavity.  

PubMed

Peritoneal implantation of cancer cells, particularly postoperative seeding metastasis, frequently occurs in patients with primary tumors in the stomach, colon, liver, and ovary. Peritoneal carcinomatosis is associated with poor prognosis. In this work, we evaluated the prophylactic effect of intraperitoneal administration of selenium (Se), an essential trace element and a putative chemopreventive agent, on peritoneal implantation of cancer cells. Elemental Se nanoparticles were injected into the abdominal cavity of mice, into which highly malignant H22 hepatocarcinoma cells had previously been inoculated. Se concentrations in the cancer cells and tissues, as well as the efficacy of proliferation inhibition and safety, were evaluated. Se was mainly concentrated in cancer cells compared to Se retention in normal tissues, showing at least an order of magnitude difference between the drug target cells (the H22 cells) and the well-recognized toxicity target of Se (the liver). Such a favorable selective distribution resulted in strong proliferation suppression without perceived host toxicity. The mechanism of action of the Se nanoparticle-triggered cytotoxicity was associated with Se-mediated production of reactive oxygen species, which impaired the glutathione and thioredoxin systems. Our results suggest that intraperitoneal administration of Se is a safe and effective means of preventing growth of cancer cells in the peritoneal cavity for the above-mentioned high-risk populations. PMID:24727439

Wang, Xin; Sun, Kang; Tan, Yanping; Wu, Shanshan; Zhang, Jinsong

2014-07-01

89

Surface diffusion experiments with STM: equilibrium correlations and non-equilibrium low temperature growth.  

PubMed

Measurements of surface diffusion depend on the state of the system whether the state is equilibrium versus non-equilibrium. Equilibrium experiments carried out in 2-d overlayers measure the collective diffusion coefficient D(c) and can test theoretical predictions in two-dimensional statistical mechanics. Growth experiments typically carried out at low temperatures and/or high flux rates probe systems under non-equilibrium conditions where novel diffusion mechanisms can potentially exist. The use of STM to study both types of measurements is discussed. D(c) can be measured from the autocorrelation of time-dependent tunneling current fluctuations generated by atom motion in and out of the tunneling area. Controlled experiments as function of temperature, coverage and tip-surface separation confirm that the signal is diffusive. For growth experiments the unusually uniform height island (for Pb/Si(111) In/Si(111)) has revealed a novel and intriguing type of diffusion at low temperatures that accounts for the high degree of the self organization. By monitoring the evolution of the stable islands out of a mixture of stable and unstable islands the unusual role of the wetting layer surrounding the growing islands is revealed. PMID:21386459

Tringides, M C; Hupalo, M

2010-07-01

90

Cavity nucleation and growth during helium implantation and neutron irradiation of Fe and steel  

NASA Astrophysics Data System (ADS)

The present work concerns investigations of damage accumulation during helium implantation of pure iron and the reduced activation ferritic-martensitic steel 'EUROFER 97' at 323K and 623K as well as during neutron irradiation with or without prior helium implantation. The defect microstructure, in particular the cavities, was characterized using Positron Annihilation Lifetime Spectroscopy (PALS) and Transmission Electron Microscopy (TEM). The PALS investigations reveal a clear difference between the He implantation effects in Fe and EUROFER 97 at both temperatures. For both materials the mean positron lifetime increases with He dose in the range 1 - 100 appm, although the increase is stronger for Fe than for EUROFER 97 and for both materials stronger for implantation at 323K than at 623K.

Eldrup, M.; Singh, B. N.

2013-06-01

91

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

SciTech Connect

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

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

2012-06-15

92

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

93

Cavity growth and rupture of {beta}-treated zirconium: A crystallographic model  

SciTech Connect

This study aims to understand the damage mechanisms observed in {beta}-treated zirconium. Damage voids are characterized by a tubular morphology with hexagonal cross-section; their growth kinetics is determined experimentally. From these observations, a model based on the principle of creation of free surface by crystallographic slip permits one to explain the stability of the hexagonal shape and to predict a growth rate closer to the experimental value than traditional models. This improvement is due to the sensitivity of the free surface creation mechanism to the stress concentration factor k, which can not be accounted for in models based on continuum mechanics.

Crepin, J.; Bretheau, T.; Caldemaison, D. [Ecole Polytechnique, Palaiseau (France). Lab. de Mecanique des Solides] [Ecole Polytechnique, Palaiseau (France). Lab. de Mecanique des Solides

1996-12-01

94

Further Studies on Beam Breakup Growth Reduction by Cavity Cross-Couplings in Recirculating Accelerators: Effects of Long Pulse Length and Multiturn Recirculation.  

National Technical Information Service (NTIS)

Cavity cross-coupling was recently found to reduce beam breakup (BBU) growth in a recirculating accelerator known as the Spiral LIne Induction Accelerator (SLIA). Here, we extend the analyses in two respects: long beam pulse lengths and a SLIA upgrade geo...

D. Colombant Y. Y. Lau

1991-01-01

95

Diffuse proliferative glomerulonephritis associated with cetuximab, an epidermal growth factor receptor inhibitor.  

PubMed

Cetuximab is an epidermal growth factor receptor inhibitor used for advanced squamous cell carcinoma of the head and neck. We report an unusual case of diffuse proliferative and crescentic glomerulonephritis in a 67-year-old man in close temporal association with cetuximab treatment for recurrent oral squamous cell carcinoma. The patient presented with acute renal failure and nephrotic-range proteinuria. Kidney biopsy showed diffuse proliferative and focally crescentic glomerulonephritis associated with immunoglobulin A (IgA)-dominant immune-complex deposition within glomerular capillary walls and mesangium. The patient showed dramatic improvement in kidney function after discontinuation of cetuximab therapy and a short course of cyclophosphamide and steroid. The clinical outcome of this case suggests that cetuximab therapy may trigger or exacerbate IgA-mediated glomerular injury and warrants close monitoring of kidney function in patients treated with this epidermal growth factor receptor inhibitor. PMID:23474009

Sasaki, Kotaro; Anderson, Eric; Shankland, Stuart J; Nicosia, Roberto F

2013-06-01

96

Atomic self-diffusion behaviors relevant to 2D homoepitaxy growth on stepped Pd(001) surface  

NASA Astrophysics Data System (ADS)

Using molecular dynamics, nudged elastic band and modified analytic embedded atom methods, the diffusion behaviors of Pd adatom on stepped Pd(001) surface have been investigated. Lower than 975 K, Pd adatom just hops along the perfect [110]-direction step. The diffusion dynamics equation is derived from the Arrhenius law between 875 and 975 K, and the corresponding migration energy and prefactor are 0.76 eV and 5.2 × 10? 2 cm2/s respectively, which shows that they adhere to the step in case of adatom moving to the step. The adatom diffuses across the perfect step with an Ehrlich–Schwoebel barrier of 0.09 eV by exchange mechanism. Our calculations show the kink at step can markedly decrease the static energy barrier across the step with a negative Ehrlich–Schwoebel barrier, and it contributes to form layer-by-layer growth model in the epitaxial experiment. Our calculations show that the kink can also markedly improve the adatom's mass transport of interlayer, contributing to the formation of the compact film. Lastly, a quantitative result at 300 K shows that the kink affects tremendously the diffusion mobility of adatom near it, which indicates that the kink plays a key role in the formation of the compact and uniform film on Pd(001) surface in an epitaxial growth experiment.

Liu, Fusheng; Hu, Wangyu; Chen, Yifeng; Deng, Huiqiu; Chen, Han; Yang, Xiyuan; Luo, Wenhua

2014-06-01

97

Effect of kinks and concerted diffusion mechanisms on mass transport and growth on stepped metal surfaces  

NASA Astrophysics Data System (ADS)

We study the effect of kinks and concerted atomic mechanisms on diffusion processes relevant to metal-on-metal homoepitaxy on fcc metal surfaces vicinal to the fcc (100) direction. First, we carry out extensive finite-temperature molecular dynamics simulations based on the effective medium theory to search for diffusion mechanisms that dominate the mass transport perpendicular and parallel to step edges. Then, the energetics of these processes are studied by ground state calculations. Our results show that kinks play an important role for diffusion both across and along step edges. In particular, the combined effect of kinks and concerted exchange is found to be able to remove locally the step edge barrier for mass transport across the step. The relative importance of some of the processes depends on the local tilt of the interface. We report results for copper, silver, and nickel, and discuss the generic features of energetics of diffusion processes in effective medium theory and other semi-empirical many-atom models. We also consider the implications of our results on surface growth and for models of surface growth under molecular beam epitaxy conditions.

Merikoski, J.; Vattulainen, I.; Heinonen, J.; Ala-Nissila, T.

1997-10-01

98

Pattern formation in reaction-diffusion models with nonuniform domain growth  

Microsoft Academic Search

Recent examples of biological pattern formation where a pattern changes qualitatively as the underlying domain grows have\\u000a given rise to renewed interest in the reaction-diffusion (Turing) model for pattern formation. Several authors have now reported\\u000a studies showing that with the addition of domain growth the Turing model can generate sequences of patterns consistent with\\u000a experimental observations. These studies demonstrate the

E. J. Crampin; W. W. Hackborn; P. K. Maini

2002-01-01

99

A simple diffusion model for the growth kinetics of ?' iron nitride on the pure iron substrate  

NASA Astrophysics Data System (ADS)

A simplified diffusion model designed to predict the thickness, microstructure of nitrided layer on the pure iron, and the nitrogen profile is reported. The error function model based on Fick's laws was used to study the growth kinetics of ?' phase during the gas nitriding process. The validity of the generated computer program was checked by comparing our simulation results with the experimental data taken from the literature and a fairly good agreement is achieved between calculated and experimentally measured values.

Keddam, M.; Djeghlal, M. E.; Barrallier, L.

2005-04-01

100

Fitting dynamic growth models of biological phenomena from sample observations through Gaussian diffusion processes.  

PubMed

This paper addresses the building of stochastic models that adequately describe dynamic phenomena and, in particular, those that occur in the Biosciences. In this context, the empirical fitting of a Gaussian diffusion process from sample data of a dynamic growth phenomenon is considered. In order to do this, a methodology based on approximations to its mean and variance functions is presented. Finally, several applications based on simulated and real data have been carried out. PMID:23313515

Barrera-García, Antonio J; Román-Román, Patricia; Torres-Ruiz, Francisco

2013-06-01

101

The dynamics of diffusion and gel growth during nonsolvent-induced phase inversion of polyethersulfone  

Microsoft Academic Search

The in-situ, macroscopic dynamics of diffusion and gel growth during phase inversion of polyethersulfone (PES) solutions have been investigated using optical monitoring of the dark-ground and reflected light images which form on solution-nonsolvent contact. Data are reported for various ternary PES\\/solvent\\/nonsolvent systems. Analysis of two molecular weight systems shows that, under rapid quench conditions, a well-defined liquid demixing zone forms

A. J. McHugh; D. C. Miller

1995-01-01

102

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

NASA Astrophysics Data System (ADS)

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

Aschwanden, Markus J.

2012-09-01

103

Application of Monte Carlo techniques to transient thermal modeling of cavity radiometers having diffuse-specular surfaces  

NASA Technical Reports Server (NTRS)

A viable alternative to the net exchange method of radiative analysis which is equally applicable to diffuse and diffuse-specular enclosures is presented. It is particularly more advantageous to use than the net exchange method in the case of a transient thermal analysis involving conduction and storage of energy as well as radiative exchange. A new quantity, called the distribution factor is defined which replaces the angle factor and the configuration factor. Once obtained, the array of distribution factors for an ensemble of surface elements which define an enclosure permits the instantaneous net radiative heat fluxes to all of the surfaces to be computed directly in terms of the known surface temperatures at that instant. The formulation of the thermal model is described, as is the determination of distribution factors by application of a Monte Carlo analysis. The results show that when fewer than 10,000 packets are emitted, an unsatisfactory approximation for the distribution factors is obtained, but that 10,000 packets is sufficient.

Mahan, J. R.; Eskin, L. D.

1981-01-01

104

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

105

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

PubMed Central

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

Picard, Nicolas; Liang, Jingjing

2014-01-01

106

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

PubMed

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

Picard, Nicolas; Liang, Jingjing

2014-01-01

107

Morphologies of an anisotropic diffusion limited growth model to study electroless deposition  

NASA Astrophysics Data System (ADS)

We report results of Monte Carlo simulation of a model which mimics certain aspects of electroless deposition of metals on polymeric surfaces. In the proposed model growth germinates from certain ``active'' particles residing on a flat surface. Further growth occurs via sticking of a diffusing particle while it is within the range of one of these active particles. Once within the attractive range of an ``active'' particle, the motion of the approaching particle is considered ballistic. This newly adsorbed particle then acts as an ``active'' site for further growth and the process continues. We monitor the layer by layer density variation, the pair correlation function and the structure factor as a function of the initial density of the particles and the range of the reaction, and comment on the fractal aspect of the morphology.

Kuebler, Stephen M.; Clukay, Christopher J.; Dutta, Aniruddha; Grabill, Christopher N.; Heinrich, Helge; Bhattacharya, Aniket

2012-02-01

108

Atomistic studies of manipulation, growth and diffusion on fcc metal surfaces  

NASA Astrophysics Data System (ADS)

In this dissertation I present an extensive study of several issues related to manipulation, growth and diffusion of atoms and nanoclusters on fcc metal surfaces. One of the important aspects in understanding the effect of adatoms or clusters or even the effect of a tip is to examine the energy landscape of the surface in the presence of these objects. In our study of lateral manipulation using a tip, the use of the Grid method to obtain the energy landscape, has revealed useful information about the shift in the saddle point. Calculations on homogeneous as well as heterogeneous fcc(111) metal systems have been performed. Vertical manipulation on flat, stepped and kinked surfaces have given interesting results about the ease of manipulation on these surfaces. During growth, atoms at the edges of stepped surfaces experience an effect called the Kink Ehrlich Schwoebel Effect (KESE). Fluctuations that occur along the step edges play an important role in island decay for islands in the vicinity of a step edge, as observed in many experiments. Our standard Kinetic Monte Carlo (KMC) study on the vicinals of Cu(001) systems has shown that the KES barrier is in fact responsible for the ledge morphology that we see in our systems. To investigate cluster diffusion on fcc(111) systems which are more complex due to the occurrence of two types of step edge microfacets ((100) and (111)) in them, a KMC technique involving a unique pattern recognition scheme was developed to classify the environment of an atom. The energy barriers for different mechanisms were calculated extensively for Cu/Cu(111) as well as Ag/Ag(111) systems, using the NEB. The intriguing results obtained for these two-dimensional clusters, show magic cluster sizes having much lower diffusivity at 300 K as compared to the general clusters. The dependence of the diffusion coefficient on temperature as well as size of cluster has also been explored. Diffusion prefactors play an important role in the diffusion mechanisms. Most of the KMC studies assume a fixed prefactor. However, realistically this is not true. To get an understanding of the prefactors and their ratios for the important mechanisms, a study on the Ag/Ag(111) system shows that the ratio of the prefactors for step edge to terrace diffusion >1, at low temperatures, which is in agreement with experimental observations. A molecular dynamics (MD) study was also performed to get an understanding of the initial evolution of certain clusters and the important mechanisms involved. All these investigations have given us a deep insight into several intriguing surface phenomena, observed in experiments and theoretical simulations.

Ghosh, Chandana

109

Growth of Mycobacterium lepraemurium in Diffusion Chambers Containing Human Embryonic Skin Cells and in Cell-free Chambers  

Microsoft Academic Search

SUMMARY Mycobacterium lepraemurium grew in diffusion chambers containing human embryonic skin cells maintained in mice, guinea pigs and Petri plate monolayer cultures of human embryonic skin cells. Growth also occurred in diffusion chambers without skin cells maintained in mice and guinea pigs. A 28-8-fold increase in the number of bacilli was obtained when chambers containing skin cells were incuba- ted

W. C. WIYGUL; W. A. RIGHTSEL

1971-01-01

110

Substrate and metabolite diffusion within model medium for soft cheese in relation to growth of Penicillium camembertii.  

PubMed

Penicillium camembertii was cultivated on a jellified peptone-lactate based medium to simulate the composition of Camembert cheese. Diffusional limitations due to substrate consumption were not involved in the linear growth recorded during culture, while nitrogen (peptone) limitation accounted for growth cessation. Examination of gradients confirmed that medium neutralization was the consequence of lactate consumption and ammonium production. The diffusion of the lactate assimilated from the core to the rind and that of the ammonium produced from the rind to the core was described by means of a diffusion/reaction model involving a partial linking of consumption or production to growth. The model matched experimental data throughout growth. PMID:16491357

Aldarf, Mazen; Fourcade, Florence; Amrane, Abdeltif; Prigent, Yves

2006-08-01

111

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

112

Growth kinetics and morphology of a ballistic deposition model that incorporates surface diffusion for two species.  

PubMed

We introduce a ballistic deposition model for two kinds of particles (active and inactive) in (2+1) dimensions upon introducing surface diffusion for the inactive particles. A morphological structural transition is found as the probability of being the inactive particle increases. This transition is well defined by the change in the behavior of the surface width when it is plotted as a function of time and probability. The exponents alpha and beta calculated for different values of probability show the same behavior. The presence of both types of particles gives rise to three different processes that control the growing surface: overhanging, nonlocal growth, and diffusion. It finally leads to a morphological structural transition where the universality changes away from that of Kardar, Parisi, and Zhang, in (2+1) dimensions, but not into that of Edwards and Wilkinson. PMID:11969884

El-Nashar, H F; Cerdeira, H A

1999-08-01

113

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

114

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

NASA Astrophysics Data System (ADS)

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

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

115

Growth of 1.5 micron gallium indium nitrogen arsenic antimonide vertical cavity surface emitting lasers by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Fiber optics has revolutionized long distance communication and long haul networks, allowing unimaginable data speeds and noise-free telephone calls around the world for mere pennies per hour at the trunk level. But the high speeds of optical fiber generally do not extend to individual workstations or to the home, in large part because it has been difficult and expensive to produce lasers which emitted light at wavelengths which could take advantage of optical fiber. One of the most promising solutions to this problem is the development of a new class of semiconductors known as dilute nitrides. Dilute nitrides such as GaInNAs can be grown directly on gallium arsenide, which allows well-established processing techniques. More important, gallium arsenide allows the growth of vertical-cavity surface-emitting lasers (VCSELs), which can be grown in dense, 2D arrays on each wafer, providing tremendous economies of scale for manufacturing, testing, and packaging. Unfortunately, GaInNAs lasers have suffered from what has been dubbed the "nitrogen penalty," with high thresholds and low efficiency as the fraction of nitrogen in the semiconductor was increased. This thesis describes the steps taken to identify and essentially eliminate the nitrogen penalty. Protecting the wafer surface from plasma ignition, using an arsenic cap, greatly improved material quality. Using a Langmuir probe, we further found that the nitrogen plasma source produced a large number of ions which damaged the wafer during growth. The ions were dramatically reduced using deflection plates. Low voltage deflection plates were found to be preferable to high voltages, and simulations showed low voltages to be adequate for ion removal. The long wavelengths from dilute nitrides can be partly explained by wafer damage during growth. As a result of these studies, we demonstrated the first CW, room temperature lasers at wavelengths beyond 1.5mum on gallium arsenide, and the first GaInNAs(Sb) VCSELs beyond 1.31mum: 1.46mum. These techniques offer the promise of inexpensive, high speed fiber networking.

Wistey, Mark Allan

116

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

PubMed Central

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

2013-01-01

117

Growth kinetics of intermediate compounds at a planar solid-solid or solid-liquid interface by diffusion mechanisms  

Microsoft Academic Search

A diffusional model of interface displacement kinetics is proposed for the growth of n intermediate compounds at an initially planar interface between two semi-infinite phases. The model is based on the solution of Fick’s equations with the restrictive assumptions of simultaneous growth of n intermediate phases, unidirectional diffusion flow, and local equilibrium conditions. The velocity of each interface follows the

André Coulet; Karine Bouche; Francis Marinelli; Francoise Barbier

1997-01-01

118

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

SciTech Connect

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

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

2007-03-15

119

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

PubMed

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

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

2014-04-01

120

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

PubMed

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

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

2010-03-01

121

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

PubMed

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

Bayraktar, Meriç; Männer, Jörg

2014-01-01

122

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

PubMed Central

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

Bayraktar, Meric; Manner, Jorg

2014-01-01

123

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

PubMed

The effects of cluster diffusion on the submonolayer island density and island-size distribution are studied for the case of irreversible growth of compact islands on a 2D substrate. In our model we assume instantaneous coalescence of circular islands, while the cluster mobility is assumed to exhibit power-law decay as a function of island size with exponent ?. Results are presented for ?=1/2,1, and 3/2 corresponding to cluster diffusion via Brownian motion, correlated evaporation condensation, and edge diffusion respectively, as well as for higher values including ?=2,3, and 6. We also compare our results with those obtained in the limit of no cluster mobility (?=?). In agreement with theoretical predictions of power-law behavior of the island-size distribution (ISD) for ?<1, for ?=1/2 we find N(s)(?)~s(-?) [where N(s)(?) is the number of islands of size s at coverage ?] up to a crossover island-size S(c). However, the value of the exponent ? obtained in our simulations is higher than the mean-field (MF) prediction ?=(3-?)/2. Similarly, the measured value of the exponent ? corresponding to the dependence of S(c) on the average island-size S (e.g., S(c)~S(?)) is also significantly higher than the MF prediction ?=2/(?+1). A generalized scaling form for the ISD [N(s)(?)=?/S(1+??)f(s/S(?))] is also proposed for ?<1, and using this form excellent scaling is found for ?=1/2. However, for finite ??1 neither the generalized scaling form nor the standard scaling form N(s)(?)=?/S(2)f(s/S) lead to scaling of the entire ISD for finite values of the ratio R of the monomer diffusion rate to deposition flux. Instead, the scaled ISD becomes more sharply peaked with increasing R and coverage. This is in contrast to models of epitaxial growth with limited cluster mobility for which good scaling occurs over a wide range of coverages. PMID:21599179

Kryukov, Y A; Amar, Jacques G

2011-04-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2000-03-01

125

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

126

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

PubMed

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

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

2013-12-01

127

Diffusion of lactate and ammonium in relation to growth of Geotrichum candidum at the surface of solid media.  

PubMed

Geotrichum candidum was cultivated at the surface of solid model media containing peptone to simulate the composition of Camembert cheese. The surface growth of G. candidum induced the diffusion of substrates from the core to the rind and the diffusion of produced metabolites from the rind to the core. In the range of pH measured during G. candidum growth, constant diffusion coefficients were found for lactate and ammonium, 0.4 and 0.8 cm(2) day(-1), respectively, determined in sterile culture medium. Growth kinetics are described using the Verlhust model and both lactate consumption and ammonium production are considered as partially linked to growth. The experimental diffusion gradients of lactate and ammonium recorded during G. candidum growth have been fitted. The diffusion/reaction model was found to match with experimental data until the end of growth, except with regard to ammonium concentration gradients in the presence of lactate in the medium. Indeed, G. candidum preferentially assimilated peptone over lactate as a carbon source, resulting in an almost cessation of ammonium release before the end of growth. On peptone, it was found that the proton transfer did not account for the ammonium concentration gradients. Indeed, amino acids, being positively charged, are involved in the proton transfer at the beginning of growth. This effect can be neglected in the presence of lactate within the medium, and the sum of both lactate consumption and ammonium release gradients corresponded well to the proton transfer gradients, confirming that both components are responsible for the pH increase observed during the ripening of soft Camembert cheese. PMID:15211490

Aldarf, M; Fourcade, F; Amrane, A; Prigent, Y

2004-07-01

128

Influence of the supersaturation on Si diffusion and growth of Si nanoparticles in silicon-rich silica  

NASA Astrophysics Data System (ADS)

SiOX/SiO2 multilayers have been prepared using magnetron sputtering and annealed in order to induce the growth of Si nanoparticles in Si-rich sublayers. This sample has undergone several successive annealing treatments and has been analyzed using a laser-assisted tomographic atom probe. This allows the phase separation between Si and SiO2 and the growth process to be studied at the atomic scale as a function of annealing temperature. Si diffusion coefficient is estimated from the accurate measurement of matrix composition and Si particle size. We demonstrate that the diffusion coefficient in SiOX is supersaturation dependent, leading to a decrease in silicon particle growth kinetics during annealing. In addition, we use our measurements to predict the critical thickness for efficient SiO2 diffusion barriers.

Roussel, M.; Talbot, E.; Pareige, P.; Gourbilleau, F.

2013-02-01

129

Novel optical studies of ion-erosion, growth, and diffusion on metal surfaces  

NASA Astrophysics Data System (ADS)

In this dissertation, the novel optical techniques of oblique-incidence reflectivity difference (OI-RD) and linear optical diffraction (LOD), combined in some cases with low energy electron diffraction (LEED), are applied to several distinct surface physics problems. First, studies of Ar- and Ne-ion sputtering and thermal annealing of Nb(110) and Cu(111) using the OI-RD technique are reported. Using a 1.3° miscut Ni(111) sample, it is demonstrated for the first time that the OI-RD technique can be used to monitor directly the average slope of a surface morphology undergoing ion-erosion. In addition, the adsorption, growth and desorption of Xe on Nb(110) is investigated using LEED and OI-RD. The Xe/Nb(110) system is particularly interesting because of the large lattice mismatch between the adsorbate and the substrate. It is found that the sticking coefficient of Xe on Nb(110) is close to unity, and Xe forms a (111) close-packed thin film after forming two somewhat disordered mono-atomic transition layers on the surface. Using a linear optical diffraction technique the diffusion of Xe density-grating on Nb(110) at different temperatures is also studied. The diffusion rate is characterized by an Arrhenius behavior, and the values for the activation energy and the diffusivity are determined. Finally, OI-RD studies of the adsorption and desorption of atomic hydrogen and deuterium on Nb(110) and Cu(111) are reported. On the Nb(110) surface, very small values of initial sticking coefficients are found. From the desorption studies of hydrogen from Cu(111), the desorption energy and the pre-exponential factor are determined.

Thomas, Petros

130

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

NASA Astrophysics Data System (ADS)

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

Xi, Hanmi; Sun, Ye; Yu, Lian

2009-03-01

131

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

132

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

133

Random walk on lattices: graph-theoretic approach to simulating long-range diffusion-attachment growth models.  

PubMed

Interest in thin-film fabrication for industrial applications have driven both theoretical and computational aspects of modeling its growth. One of the earliest attempts toward understanding the morphological structure of a film's surface is through a class of solid-on-solid limited-mobility growth models such as the Family, Wolf-Villain, or Das Sarma-Tamborenea models, which have produced fascinating surface roughening behaviors. These models, however, restrict the motion of an incidence atom to be within the neighborhood of its landing site, which renders them inept for simulating long-distance surface diffusion such as that observed in thin-film growth using a molecular-beam epitaxy technique. Naive extension of these models by repeatedly applying the local diffusion rules for each hop to simulate large diffusion length can be computationally very costly when certain statistical aspects are demanded. We present a graph-theoretic approach to simulating a long-range diffusion-attachment growth model. Using the Markovian assumption and given a local diffusion bias, we derive the transition probabilities for a random walker to traverse from one lattice site to the others after a large, possibly infinite, number of steps. Only computation with linear-time complexity is required for the surface morphology calculation without other probabilistic measures. The formalism is applied, as illustrations, to simulate surface growth on a two-dimensional flat substrate and around a screw dislocation under the modified Wolf-Villain diffusion rule. A rectangular spiral ridge is observed in the latter case with a smooth front feature similar to that obtained from simulations using the well-known multiple registration technique. An algorithm for computing the inverse of a class of substochastic matrices is derived as a corollary. PMID:24730847

Limkumnerd, Surachate

2014-03-01

134

Random walk on lattices: Graph-theoretic approach to simulating long-range diffusion-attachment growth models  

NASA Astrophysics Data System (ADS)

Interest in thin-film fabrication for industrial applications have driven both theoretical and computational aspects of modeling its growth. One of the earliest attempts toward understanding the morphological structure of a film's surface is through a class of solid-on-solid limited-mobility growth models such as the Family, Wolf-Villain, or Das Sarma-Tamborenea models, which have produced fascinating surface roughening behaviors. These models, however, restrict the motion of an incidence atom to be within the neighborhood of its landing site, which renders them inept for simulating long-distance surface diffusion such as that observed in thin-film growth using a molecular-beam epitaxy technique. Naive extension of these models by repeatedly applying the local diffusion rules for each hop to simulate large diffusion length can be computationally very costly when certain statistical aspects are demanded. We present a graph-theoretic approach to simulating a long-range diffusion-attachment growth model. Using the Markovian assumption and given a local diffusion bias, we derive the transition probabilities for a random walker to traverse from one lattice site to the others after a large, possibly infinite, number of steps. Only computation with linear-time complexity is required for the surface morphology calculation without other probabilistic measures. The formalism is applied, as illustrations, to simulate surface growth on a two-dimensional flat substrate and around a screw dislocation under the modified Wolf-Villain diffusion rule. A rectangular spiral ridge is observed in the latter case with a smooth front feature similar to that obtained from simulations using the well-known multiple registration technique. An algorithm for computing the inverse of a class of substochastic matrices is derived as a corollary.

Limkumnerd, Surachate

2014-03-01

135

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

2012-07-01

136

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

137

Dependence of superconducting properties of underdoped Bi2201 single crystals on the charge composition and growth conditions in gas-filled cavities  

Microsoft Academic Search

High-quality Bi2 + x\\u000a Sr2 ? y\\u000a CuO6 + ? (Bi-2201) single crystals with the ratio Bi\\/Sr = 1.4–2.0 were grown by the free growth method in gas-filled cavities in KCl\\u000a solution-melt in a range of doping levels, which provides variation in superconducting properties from insulators to optimally\\u000a doped crystals. The charge composition Bi : Sr : Cu = 1.7

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

2008-01-01

138

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

2011-07-01

139

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

140

Do volcanic gases represent equilibrium volatile concentrations? Some insights from a model of diffusive fractionation during rapid bubble growth  

NASA Astrophysics Data System (ADS)

Measurements of volcanic gas compositions are often presumed to be directly related to equilibrium compositions of fluids exsolved at depth in magmatic systems that rapidly escape into the atmosphere. In particular, changes in the ratios of volatile species concentrations in volcanic gases have been interpreted to reflect influx of new magma batches or changes in the degassing depth. However, other mechanisms can also yield changes in volcanic gas compositions. One such mechanism is diffusive fractionation during rapid bubble growth. Such fractionation can occur because radial growth rates of bubbles in magmas are estimated to be in the range of 10-6 to 10-3 m s-1 and diffusion coefficients of minor volatiles (e.g., Cl, F, S, CO2) are orders of magnitude slower, 10-12 to 10-9 m2 s-1. Thus a bubble that rapidly grows and subsequently loses its volatiles to the surface may contribute a fluid sample whose concentration is affected by the interplay between the kinetics of bubble growth and volatile diffusion in the melt. A finite difference code was developed to calculate the effects of rapid bubble growth on the concentration of minor elements in the bubble for a spherical growth geometry. The bubble is modeled with a fixed growth rate and a constant equilibrium fluid-melt partition coefficient, KD. Bubbles were modeled to grow to a radius of 50 ?m, the size at which the dominant bubble growth mechanism appears to change from diffusion to coalescence. The critical variables that control the departure from equilibrium behavior are the K D and the ratio of the growth velocity, V, to the diffusivity, D. Modeling bubble growth in a magma chamber at 100 MPa demonstrates that when KD is in the range of 10 to 1000 at low V/D values (e.g., 103 m-1) the composition of the fluid is at, or near, equilibrium with the melt. However, as V/D increases the bubble composition deviates increasingly from equilibrium. For V/D ratios of 105 and equilibrium KD's of either 50 or 100 (similar to estimates for S), a bubble with a 50 ?m radius will contain a fluid whose concentration was apparently determined by a KD of less than 10. These models also demonstrate that the combination of rapid bubble growth with slow diffusion can deplete the melt in the volatile species only within the immediate neighborhood, on the order of 100 ?m. If bubbles are spaced further apart the melts may retain significant concentrations of dissolved volatiles, which could lead to secondary and tertiary nucleation events. These models for diffusive fractionation during rapid bubble growth suggest that changes in the ratios of minor elements in volcanic gases may be influenced by bubble growth rate changes. Volatiles with lower diffusivities and volatiles with very high or very low partition coefficients will be more influenced by this process. Diffusive fractionation may be responsible for the drop in the CO2/SO2 ratios sometimes observed prior to large eruptions of Stromboli volcano.

Baker, D. R.

2012-12-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

142

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

143

Growth of Highly Strained InGaAs Quantum Wells by Metalorganic Chemical Vapor Deposition with Application to Vertical-Cavity Surface-Emitting Laser  

NASA Astrophysics Data System (ADS)

A series of highly strained InGaAs quantum wells (QWs) with GaAs barriers emitting at wavelength longer than 1.2 ?m are grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). The optimized windows of the V/III ratio of the InGaAs layer and the growth rate of the barrier are first investigated on thease highly strained QWs. By an appropriate choice of the growth conditions, we extend the room-temperature photoluminescence (PL) wavelength of InGaAs QWs to 1245 nm, which corresponds to an indium content of 42%. A GaAs-based InGaAs vertical-cavity surface-emitting laser (VCSEL) at an emission wavelength of 1.28 ?m with a large detuning of 90 nm has been realized by the use of highly strained InGaAs QWs.

Chen, I-Liang; Hsu, Wei-Chou; Lee, Tsin-Dong; Kuo, Hao-Chung; Su, Ke-Hua; Chiou, Chih-Hung; Wang, Jin-Mei; Chang, Yu-Hsiang

2006-01-01

144

Cavity QED in Quantum Dot - Micropillar Cavity Systems  

Microsoft Academic Search

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

S. Reitzenstein; A. Forchel

2009-01-01

145

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

146

c-Ski overexpression promotes tumor growth and angiogenesis through inhibition of transforming growth factor-beta signaling in diffuse-type gastric carcinoma.  

PubMed

c-Ski, originally identified as a proto-oncogene product, is an important negative regulator of transforming growth factor (TGF)-beta family signaling through interaction with Smad2, Smad3, and Smad4. High expression of c-Ski has been found in some cancers, including gastric cancer. We previously showed that disruption of TGF-beta signaling by dominant-negative TGF-beta type II receptor in a diffuse-type gastric carcinoma model accelerated tumor growth through induction of tumor angiogenesis by decreased expression of the anti-angiogenic factor thrombospondin (TSP)-1. Here, we examined the function of c-Ski in human diffuse-type gastric carcinoma OCUM-2MLN cells. Overexpression of c-Ski inhibited TGF-beta signaling in OCUM-2MLN cells. Interestingly, c-Ski overexpression resulted in extensive acceleration of the growth of subcutaneous xenografts in BALB/c nu/nu female mice (6 weeks of age). Similar to tumors expressing dominant-negative TGF-beta type II receptor, histochemical studies revealed less fibrosis and increased angiogenesis in xenografted tumors expressing c-Ski compared to control tumors. Induction of TSP-1 mRNA by TGF-beta was attenuated by c-Ski in vitro, and expression of TSP-1 mRNA was decreased in tumors expressing c-Ski in vivo. These findings suggest that c-Ski overexpression promotes the growth of diffuse-type gastric carcinoma through induction of angiogenesis. PMID:19594546

Kiyono, Kunihiko; Suzuki, Hiroshi I; Morishita, Yasuyuki; Komuro, Akiyoshi; Iwata, Caname; Yashiro, Masakazu; Hirakawa, Kosei; Kano, Mitsunobu R; Miyazono, Kohei

2009-10-01

147

On the transition from short-range diffusion-limited to collision-limited growth in alloy solidification  

SciTech Connect

Short-range diffusion-limited growth, collision-limited growth, and the transition between the two regimes are explained as natural consequences of a single model for the kinetics of alloy solidification. Analytical expressions are developed for the velocity-undercooling function of a planar interface during dilute alloy solidification, using Turnbull`s collision-limited growth model and the Continuous Growth Solute Trapping Model of Aziz and Kaplan both with and without a solute drag effect. The interface mobility, {minus}dv/dT, is shown to be very high (proportional to the speed of sound) if the alloy is sufficiently dilute or if the growth rate is sufficiently rapid for nearly complete solute trapping. The interface mobility is reduced by the three orders of magnitude (becoming proportional to the diffusive speed) at intermediate growth rates where partial solute trapping occurs. Differences in low velocity predictions of the models with and without solute drag are also discussed. Comparison of the results of the analytical expressions to numerical solutions of the non-dilute kinetic model for Al-Be alloys shows that the dilute approximation breaks down at melt compositions on the order of 10 at.%. Similar variations in the interface mobility are shown for the disorder-trapping model of Boettinger and Aziz.

Aziz, M.J. [Harvard Univ., Cambridge, MA (United States)] [Harvard Univ., Cambridge, MA (United States); Boettinger, W.J. [National Inst. of Standards and Technology, Gaithersburg, MD (United States). Metallurgy Div.] [National Inst. of Standards and Technology, Gaithersburg, MD (United States). Metallurgy Div.

1994-02-01

148

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

NASA Astrophysics Data System (ADS)

Recent studies of impact craters formed on low-density asteroids led to the proposal of a new crater formation mechanism dominated by pore collapse and compaction. Thus, it is important to study the crater formation process associated with the projectile penetration on porous cohesive targets. Laboratory impact experiments were conducted for a porous gypsum target with porosity of 50%, and flash X-rays were used to visualize the interior of the target for in situ observation of crater formation and projectile penetration. Spherical projectiles made of three different materials, stainless steel, aluminum, and nylon were impacted at 1.9-2.4 km/s (low-velocity impact) and 5.6-6.4 km/s (high-velocity impact) by using a two-stage light-gas gun. Two imaging plates were used to take two X-ray images at a different delay time from the impact moment for one shot. Two types of crater cavity shape were found on the porous gypsum target, that is, penetration holes or hemispherical cavities, depending on the projectile size and density, and the impact velocity. The drag coefficient of a projectile was determined by measuring the penetration depth changing with time, and we found that it was closely related to the crater cavity shape: it was about 0.9 for a penetration hole, while it was 2.3-3.9 for a hemispherical cavity. This large value for a hemispherical cavity could have been caused by the deformation or the disruption of the projectile. The cratering efficiency, ?tVcr(t)/mp, was found to have a power law relationship to the scaling time for crater growth, ?t = vit/rp, where vi is the impact velocity, rp is the projectile radius, and t is the time after the impact, and all data for stainless steel and aluminum projectiles merged completely and could be fitted by a power-law equation of ?V(t)/m=2.69×10-1?t1.10. Furthermore, the scaled crater volume, ?V = Vcr_final?t/mp, where Vcr_final is the final crater cavity volume, ?t is the target density, and mp is the projectile mass, was successfully fitted by a power law equation when another scaling parameter was used for the crater formation in strength regime, ?=Y/?vi2, where Yt is the target material strength, as follows: ?=1.69×10-1?Y-0.51. As a result, the crater formed on porous gypsum was revealed to be more than one order of magnitude smaller than that formed on basalt. Based on our experimental results, which visualize how crater cavities on porous cohesive materials grow with projectile penetration, we are able to discuss compression and excavation processes during crater formation quantitatively. This observation enables us to investigate and revise numerical models and crater scaling laws for high-velocity impacts into porous cohesive materials.

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

2012-11-01

149

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

150

Diffusion mediated growth of (111) oriented silver nanoparticles in polyvinyl alcohol film under 6 MeV electron irradiation  

NASA Astrophysics Data System (ADS)

Silver (111) nanoparticles were synthesized by diffusing silver from a solution into polyvinyl alcohol (PVA) films under 6 MeV electron irradiation at room temperature (~25 °C). The diffusion of silver in the PVA was confirmed by the Rutherford backscattering spectroscopy and scanning electron microscopy techniques. The plasmon absorption peak at ~426 nm was an evidence for the initiation of the diffusion mediated growth of silver nanoparticles. The x-ray diffraction results and the blueshift in the plasmon absorption peak reveal that the size of silver nanoparticles could be tailored in the range from 35 to 15 nm by varying the electron fluence over the range of 1014-1015 e/cm2.

Bogle, K. A.; Dhole, S. D.; Bhoraskar, V. N.

2006-06-01

151

Heparin and heparan sulfate increase the radius of diffusion and action of basic fibroblast growth factor  

Microsoft Academic Search

The radius of diffusion of basic FGF (bFGF) in the presence and in the absence of the glycosaminoglycans heparin and heparan sulfate was measured. Iodinated t25I-bFGF diffuses further in agarose, fibrin, and on a monolayer of bovine aortic endothelial (BAE) ceils in the presence of heparin than in its absence. Heparan sulfates affected the diffusion of ~25I-bFGF in a manner

Robert Flaumenhaft; David Moscatelli; Daniel B. Ritkin

1990-01-01

152

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

153

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

NASA Astrophysics Data System (ADS)

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

Denysenko, I.; Ostrikov, K.

2007-06-01

154

The formation of columnar fiber texture in wollastonite rims by induced stress and implications for diffusion-controlled corona growth  

Microsoft Academic Search

The evolution of columnar fiber texture was studied in wollastonite reaction rims synthesized by the reaction calcite + quartz=wollastonite\\u000a + CO2. Experiments were performed at 850 to 950 °C at 100 MPa in dry CO2 and were evaluated by scanning and transmission electron microscopy. Rim growth rates are interpreted as controlled by the\\u000a diffusion of the SiO2 component through the

R. Milke; R. Wirth

2003-01-01

155

Transforming growth factor-? decreases the cancer-initiating cell population within diffuse-type gastric carcinoma cells  

Microsoft Academic Search

Stem cells in normal tissues and cancer-initiating cells (CICs) are known to be enriched in side population (SP) cells. However, the factors responsible for the regulation of expression of ABCG2, involved in efflux of dyes, in SP cells have not been fully investigated. Here, we characterized the SP cells within diffuse-type gastric carcinoma, and examined the effects of transforming growth

S Ehata; E Johansson; R Katayama; S Koike; A Watanabe; Y Hoshino; Y Katsuno; A Komuro; D Koinuma; M R Kano; M Yashiro; K Hirakawa; H Aburatani; N Fujita; K Miyazono

2011-01-01

156

Cavity Resonators.  

National Technical Information Service (NTIS)

The microwave cavity resonator may be used in the field of electron spin resonance spectroscopy for studying samples of paramagnetic materials which are supported within the resonator. The resonator passes a maximum amount of light through the walls to th...

E. L. Cochran

1965-01-01

157

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

158

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

159

Micromechanical modeling of the interaction of diffusion mechanisms and surface energy with nonlinear material deformation: Applications to powder densification and void growth  

Microsoft Academic Search

Diffusive processes coupled to nonlinear material behavior assume importance in such important technological problems as consolidation of powders, diffusive cavitation at grain-boundary interfaces, and void growth and coalescence in solids. The first three chapters of this thesis are devoted to the study of powder densification using a small-strain finite-element scheme. In the first chapter, the coupled action of stress-driven diffusion

Sankara Jayaraman Subramanian

2001-01-01

160

Two-species d-dimensional diffusive model and its mapping onto a growth model  

Microsoft Academic Search

In this work, we consider a diffusive two-species d-dimensional model and study it in great detail. Two types of particles, with hard core, diffuse symmetrically and cross each other. For arbitrary dimensions, we obtain the exact density, the instantaneous, as well as noninstantaneous, two-point correlation functions for various initial conditions. We study the impact of correlations in the initial state

M. Mobilia; P.-A. Bares

2002-01-01

161

High affinity epidermal growth factor receptors on the surface of A431 cells have restricted lateral diffusion.  

PubMed Central

Rhodamine-labelled epidermal growth factor (Rh-EGF) was shown to bind to A431 cells grown at low density both to a small number of high affinity receptors (KD = 2.8 X 10(-10) M; fraction of total binding sites approximately 0.12) and also to a large number of low affinity receptors (KD = 4 X 10(-9) M; fraction of total binding sites approximately 0.88). Measurements of the lateral diffusion of EGF receptors on the cell surface were made using Rh-EGF and the technique of fluorescence photobleaching recovery. The high affinity receptors (labelled with 1.6 X 10(-10) M Rh-EGF, 5% of EGF binding sites occupied) did not show lateral mobility over the temperature range 3 degrees-37 degrees C. The low affinity receptors (labelled with 2.4 X 10(-7) M Rh-EGF, 90% of EGF sites occupied) showed at least 75% fluorescence recovery after photobleaching, and lateral diffusion coefficients of approximately 2 X 10(-10) cm2/s. These results show that the two populations of EGF receptors defined by binding studies differ in their freedom to diffuse laterally. The observation that the high affinity receptors are immobile indicates that lateral diffusion of receptors, at least over a distance of a few hundred nanometres or more, may not be required for the action of low concentrations of EGF.

Rees, A R; Gregoriou, M; Johnson, P; Garland, P B

1984-01-01

162

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

163

Diffusion-controlled and "diffusionless" crystal growth near the glass transition temperature: relation between liquid dynamics and growth kinetics of seven ROY polymorphs.  

PubMed

The liquid dynamics of 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, named ROY for its red, orange, and yellow crystal polymorphs, was characterized by dielectric spectroscopy and differential scanning calorimetry. Four of these polymorphs show fast "diffusionless" crystal growth at low temperatures while three others do not. ROY was found to be a typical fragile organic liquid. Its alpha relaxation process has time-temperature superposition symmetry across the viscous range (tau(alpha)=100 s-100 ns) with the width of the relaxation peak characterized by a constant beta(KWW) of 0.73. No secondary relaxation peak was observed, even with glasses made by fast quenching. For the polymorphs not showing fast crystal growth in the glassy state, the growth rate has a power-law relation with tau(alpha), u proportional to tau(alpha)(-xi), where xi approximately = 0.7. For the polymorphs showing fast crystal growth in the glassy state, the growth is so fast near and below the glass transition temperature T(g) that thousands of molecular layers can be added to the crystalline phase during one structural relaxation time of the liquid. In the glassy state, this mode of growth slows slightly over time. This slowdown is not readily explained by the effect of physical aging on the thermodynamic driving force of crystallization, the glass vapor pressure, or the rate of structural relaxation. This study demonstrates that from the same liquid or glass, the growth of some polymorphs is accurately described as being limited by the rate of structural relaxation or bulk diffusion, whereas the growth of other polymorphs is too fast to be under such control. PMID:19708750

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

2009-08-21

164

Crystallization near glass transition: transition from diffusion-controlled to diffusionless crystal growth studied with seven polymorphs.  

PubMed

A remarkable property of certain glass-forming liquids is that a fast mode of crystal growth is activated near the glass transition temperature Tg and continues in the glassy state. This growth mode, termed GC (glass-crystal), is so fast that it is not limited by molecular diffusion in the bulk liquid. We have studied the GC mode by growing seven polymorphs from the liquid of ROY, currently the top system for the number of coexisting polymorphs of known structures. Some polymorphs did not show GC growth, while others did, with the latter having higher density and more isotropic molecular packing. The polymorphs not showing GC growth grew as compact spherulites at all temperatures; their growth rates near Tg decreased smoothly with falling temperature. The polymorphs showing GC growth changed growth morphologies with temperature, from faceted single crystals near the melting points, to fiber-like crystals near Tg, and to compact spherulites in the GC mode; in the GC mode, they grew at rates 3-4 orders of magnitude faster with activation energies 2-fold smaller than the polymorphs not showing GC growth. The GC mode had rates and activation energies similar to those of a polymorphic transformation observed near Tg. The GC mode was disrupted by the onset of the liquid's structural relaxation but could persist well above Tg (up to 1.15 Tg) in the form of fast-growing fibers. We consider various explanations for the GC mode and suggest that it is solid-state transformation enabled by local molecular motions native to the glassy state and disrupted by the liquid's structural relaxation (the alpha process). PMID:18407712

Sun, Ye; Xi, Hanmi; Chen, Shuang; Ediger, M D; Yu, Lian

2008-05-01

165

Growth of highly bright-white silica nanowires as diffusive reflection coating in LED lighting.  

PubMed

Large quantities of silica nanowires were synthesized through thermal treatment of silicon wafer in the atmosphere of N(2)/H(2)(5%) under 1200 °C with Cu as catalyst. These nanowires grew to form a natural bright-white mat, which showed highly diffusive reflectivity over the UV-visible range, with more than 60% at the whole range and up to 88% at 350 nm. The utilization of silica nanowires in diffusive coating on the reflector cup of LED is demonstrated, which shows greatly improved light distribution comparing with the specular reflector cup. It is expected that these nanowires can be promising coating material for optoelectronic applications. PMID:22274235

Xi, Shuang; Shi, Tielin; Zhang, Lei; Liu, Dan; Lai, Wuxing; Tang, Zirong

2011-12-19

166

Tourmaline nodules from Capo Bianco aplite (Elba Island, Italy): an example of diffusion limited aggregation growth in a magmatic system  

NASA Astrophysics Data System (ADS)

The morphology of tourmaline nodules occurring in the Capo Bianco aplite (Elba Island, Italy) is studied. Outcrop features indicate that tourmaline nodules are the product of magmatic crystallization, as they are aligned along flow fields developed within the magmatic hosting mass. Mesoscopic observations indicate that nodule morphologies are very variable, from rounded to dendritic. Morphometric analyses show that tourmaline nodules are fractals and that fractal dimension quantifies their degree of irregularity. Numerical simulations of nodule growth are performed by using a Diffusion-Limited Aggregation process. The presence in natural samples of nodules with different morphologies is explained by considering a chaotic magmatic system characterized by a complex interplay between growth rate in different dynamical regions, latent heat of crystallization, and local convection dynamics. It is suggested that higher growth rates correspond to growth of tourmaline nodules in dynamical regions where the transfer of nutrients is very efficient. In such conditions, the latent heat released by the growing nodule is high, inducing strong local convection dynamics, destabilizing the nodule interface, and promoting the formation of dendritic morphologies. On the contrary, the growth of nodules in dynamical regions characterized by weak transfer of nutrients is inhibited leading to weak local convection dynamics and, consequently, to the formation of rounded morphologies.

Perugini, Diego; Poli, Giampiero

2007-05-01

167

Cavity QED in Quantum Dot - Micropillar Cavity Systems  

NASA Astrophysics Data System (ADS)

In this contribution we review our recent work on cavity quantum electrodynamics experiments (cQED) with single quantum dots in high quality micropillar cavities. After a short introduction to the theoretical background of cQED with single two level emitters, important aspects in the growth and patterning of quantum dot-micropillar cavities will be addressed in the second part of this review. In particular, the optimization of both the quantum dot and cavity characteristics will be discussed. Differences between weak and strong coupling are illustrated experimentally in the framework of cQED. Furthermore, the demonstration of the quantum nature in a strongly coupled quantum dot-micropillar system as well as a coherent photonic coupling of QDs mediated by the strong light field in high-Q micropillar cavities will be addressed.

Reitzenstein, S.; Forchel, A.

168

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

169

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

Microsoft Academic Search

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

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

2002-01-01

170

Combined heat transfer in floating zone growth of large silicon crystals with radiation on diffuse and specular surfaces  

NASA Astrophysics Data System (ADS)

Numerical analyses are conducted to investigate the combined heat transfer in floating zone growth of large Si crystals with needle-eye technique. The radiation element method, REM2, is employed to determine the radiative heat exchange, in which the view factors associated with the components in the float zone furnace and both the diffuse and specular reflection components are incorporated. The boundary element method and the finite difference method are adopted to calculate the electromagnetic field and the heat conduction, respectively. The effect of surface radiative characteristics of Si melt and crystal, i.e., diffuse and/or specular, is discussed in detail. It is found that the consideration of specular surfaces increases the Joulean heat and the radiative heat flux. The temperature fields are obtained for the cases of diffuse and specular, and the difference between the two different cases is obvious in the crystal and molten zone areas. The molten zone is enlarged when the specular surface is accounted for. The interface shape is examined and found to be in good agreement with the experiment.

Guo, Zhixiong; Maruyama, Shigenao; Togawa, Shinji

1998-01-01

171

Properties of vacancies and self-interstitials in silicon deduced from crystal growth, wafer processing, self-diffusion and metal diffusion  

Microsoft Academic Search

Vacancies and self-interstitials in silicon are involved, in a straightforward way, in the formation of grown-in microdefects, diffusion of metals (Au, Zn), self-diffusion and installation of vacancy depth profiles in thin quenched wafers. The diffusivities and equilibrium concentrations of the intrinsic point defects, in dependence of temperature, could be deduced by analyzing these phenomena. The defect diffusivities are high while

V. V. Voronkov; R. Falster

2006-01-01

172

[Mechanism of inhibiting the cell growth in diffuse large B-cell lymphoma by valproic acid combined with temsirolimus].  

PubMed

The aim of this study was to illustrate the mechanism of inhibiting the cell growth in diffuse large B-cell lymphoma by histone deacetylase inhibitor valproic acid (VPA) combined with mTOR inhibitor temsirolimus (TEM). MTT assay and Wright's stain were used to assess cell growth inhibition and to detect the cell morphological changes respectively. The cell apoptosis, cell cycle and cell autophagy were determined by flow cytometry. Ultrastructure changes were confirmed by electron microscopy. Protein changes were detected by Western blot. The results showed that both VPA and TEM alone inhibited cell proliferation and the effect was more obvious in the combination group. VPA combined with TEM induced cell arrest in G0/G1 phase and upregulated the expression of autophagy-related protein LC3, without cell apoptosis. Moreover, typical autophagosomes were observed, further confirming the presence of autophagy. Western blot showed the changes of proteins involved in autophagy signaling pathway. VPA decreased HDAC1 and HDAC3 expression and increased histone acetylation, suggesting that VPA also affected lymphoma cell proliferation through epigenetic modification. It is concluded that the combined treatment of VPA and TEM induces cell cycle arrest and cell autophagy, which provides a new clue for their clinical application in diffuse large B-cell lymphoma. PMID:24370026

Zheng, Zhong; Zhao, Yan; Dong, Li-Hua; Wang, Li; Cheng, Shu; Zhao, Wei-Li

2013-12-01

173

LATERAL DIFFUSION LPE GROWTH OF SINGLE CRYSTALLINE SILICON FOR PHOTOVOLTAIC APPLICATIONS  

Microsoft Academic Search

A modified liquid phase epitaxy (LPE) technique, called lateral diffusion LPE (LDLPE), is invented for low cost and high efficiency solar cell applications. Potentially, LDLPE is able to produce single crystalline silicon wafers directly from the raw material, rather than cutting wafers from single crystalline silicon ingots, therefore reducing the cost by avoiding the cutting and polishing processes.\\u000aBy using

Bo Li

2012-01-01

174

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

Microsoft Academic Search

Periodic arrays of Ta nanopillars were grown onto patterned substrates by glancing angle sputter deposition at growth temperatures T{sub s} ranging from 200 to 900 deg. C. The Si substrates were patterned using a colloidal suspension of 260-nm-diameter silica spheres that was dispersed to form a two-dimensional close-packed monolayer. At low growth temperatures, T{sub s}{<=}500 deg. C, nanopillars exhibit regular

C. M. Zhou; D. Gall

2007-01-01

175

Spatially quantifying microscopic tumor invasion and proliferation using a voxel-wise solution to a glioma growth model and serial diffusion MRI.  

PubMed

The purpose of this study was to develop a voxel-wise analytical solution to a glioma growth model using serial diffusion MRI. These cell invasion, motility, and proliferation level estimates (CIMPLE maps) provide quantitative estimates of microscopic tumor growth dynamics. After an analytical solution was found, noise simulations were performed to predict the effects that perturbations in apparent diffusion coefficient values and the time between apparent diffusion coefficient map acquisitions would have on the accuracy of CIMPLE maps. CIMPLE maps were then created for 53 patients with gliomas with WHO grades of II-IV. MR spectroscopy estimates of the choline-to-N-acetylaspartate ratio were compared to cell proliferation estimates in CIMPLE maps using Pearson's correlation analysis. Median differences in cell proliferation and diffusion rates between WHO grades were compared. A strong correlation (R(2) = 0.9714) and good spatial correspondence were observed between MR spectroscopy measurements of the choline-to-N-acetylaspartate ratio and CIMPLE map cell proliferation rate estimates. Estimates of cell proliferation and diffusion rates appear to be significantly different between low- (WHO II) and high-grade (WHO III-IV) gliomas. Cell diffusion rate (motility) estimates are highly dependent on the time interval between apparent diffusion coefficient map acquisitions, whereas cell proliferation rate estimates are additionally influenced by the level of noise present in apparent diffusion coefficient maps. PMID:21413079

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

2011-04-01

176

On the stability of radiation-pressure-dominated cavities  

NASA Astrophysics Data System (ADS)

Context. When massive stars exert a radiation pressure onto their environment that is higher than their gravitational attraction (super-Eddington condition), they launch a radiation-pressure-driven outflow, which creates cleared cavities. These cavities should prevent any further accretion onto the star from the direction of the bubble, although it has been claimed that a radiative Rayleigh-Taylor instability should lead to the collapse of the outflow cavity and foster the growth of massive stars. Aims: We investigate the stability of idealized radiation-pressure-dominated cavities, focusing on its dependence on the radiation transport approach used in numerical simulations for the stellar radiation feedback. Methods: We compare two different methods for stellar radiation feedback: gray flux-limited diffusion (FLD) and ray-tracing (RT). Both methods are implemented in our self-gravity radiation hydrodynamics simulations for various initial density structures of the collapsing clouds, eventually forming massive stars. We also derive simple analytical models to support our findings. Results: Both methods lead to the launch of a radiation-pressure-dominated outflow cavity. However, only the FLD cases lead to prominent instability in the cavity shell. The RT cases do not show such instability; once the outflow has started, it precedes continuously. The FLD cases display extended epochs of marginal Eddington equilibrium in the cavity shell, making them prone to the radiative Rayleigh-Taylor instability. In the RT cases, the radiation pressure exceeds gravity by 1-2 orders of magnitude. The radiative Rayleigh-Taylor instability is then consequently suppressed. It is a fundamental property of the gray FLD method to neglect the stellar radiation temperature at the location of absorption and thus to underestimate the opacity at the location of the cavity shell. Conclusions: Treating the stellar irradiation in the gray FLD approximation underestimates the radiative forces acting on the cavity shell. This can lead artificially to situations that are affected by the radiative Rayleigh-Taylor instability. The proper treatment of direct stellar irradiation by massive stars is crucial for the stability of radiation-pressure-dominated cavities. Movies are available in electronic form at http://www.aanda.org

Kuiper, R.; Klahr, H.; Beuther, H.; Henning, Th.

2012-01-01

177

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

NASA Astrophysics Data System (ADS)

We show that d+1 -dimensional surface growth models can be mapped onto driven lattice gases of d -mers. The continuous surface growth corresponds to one dimensional drift of d -mers perpendicular to the (d-1) -dimensional “plane” spanned by the d -mers. This facilitates efficient bit-coded algorithms with generalized Kawasaki dynamics of spins. Our simulations in d=2 , 3, 4, 5 dimensions provide scaling exponent estimates on much larger system sizes and simulations times published so far, where the effective growth exponent exhibits an increase. We provide evidence for the agreement with field theoretical predictions of the Kardar-Parisi-Zhang universality class and numerical results. We show that the (2+1) -dimensional exponents conciliate with the values suggested by Lässig within error margin, for the largest system sizes studied here, but we cannot support his predictions for (3+1)d numerically.

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

2010-03-01

178

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

179

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

2008-07-15

180

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

181

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

Microsoft Academic Search

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

Marius Heinen; Alain Mollier; Peter De Willigen

2003-01-01

182

Multiple lineage colony growth from human marrow in plasma clot diffusion chambers  

SciTech Connect

Marrow cells from ten healthy adult donors were cultured in plasma clot diffusion chambers implanted intraperitoneally into mice. Host animals were conditioned by two injections of phenylhydrazine and 600 cGy of x-rays. Cultures (5 X 10(4) cells/chamber) were continued for between 2 and 40 days and the chambers were retransplanted into new host animals every 5 days. Following termination of cultures, plasma clots were stained with benzidine-hematoxylin and analyzed microscopically. Erythroid, neutrophil, monocyte, eosinophil, megakaryocyte, mixed, undifferentiated, and fibroblastoid colonies were grown with neutrophil, erythroid, monocyte, and eosinophil colonies being the most frequent. A total of between 25 and 60 colonies was observed per chamber at any time point.

Pojda, Z.; Szczylik, C.; Wiktor-Jedrzejczak, W.

1987-10-01

183

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

184

Prognostic significance of hepatocyte growth factor and c-MET expression in patients with diffuse large B-cell lymphoma.  

PubMed

The expression and prognostic significance of hepatocyte growth factor (HGF) and its receptor c-MET (MET proto-oncogene) was analysed in 96 cases of diffuse large B-cell lymphoma (DLBCL). Tissue sections were immunohistochemically stained for HGF and c-Met. The prognosis of HGF-positive and c-Met-positive cases was significantly worse than negative cases (HGF: P = 0.0036; c-Met: P = 0.0002). In addition, in the low-risk international prognostic index group, HGF-negative and c-Met-negative cases had a significantly better prognosis than positive cases (HGF: P = 0.0009; c-Met: P < 0.0001). Our results suggest that HGF/c-MET is a useful clinical marker of prognosis for patients with DLBCL. PMID:15491290

Kawano, R; Ohshima, K; Karube, K; Yamaguchi, T; Kohno, S; Suzumiya, J; Kikuchi, M; Tamura, K

2004-11-01

185

Diffusion and interface growth in hafnium oxide and silicate ultrathin films on Si(001)  

Microsoft Academic Search

Medium energy ion scattering has been used in combination with O16 and O18 isotope tracing to determine elemental depth distributions and elucidate oxygen transport in 2-5 nm thick HfO2 and HfSiOx films grown by atomic layer deposition on Si(001). Both the oxygen isotope exchange rate in the dielectric as well as the interfacial silicon oxide growth rates were examined as

L. V. Goncharova; M. Dalponte; T. Feng; T. Gustafsson; E. Garfunkel; P. S. Lysaght; G. Bersuker

2011-01-01

186

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

SciTech Connect

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

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

2003-04-01

187

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

SciTech Connect

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

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

1997-03-01

188

A diffusion model for describing the bilayer growth (FeB\\/Fe 2B) during the iron powder-pack boriding  

Microsoft Academic Search

In this paper, a diffusion model is proposed for studying the bilayer growth kinetics (FeB\\/Fe2B) on pure iron substrate during the powder-pack boriding in the temperature range of 1023–1273K.This model based on Fick's laws was solved, under certain assumptions, considering a parabolic growth of iron borides.For this purpose, a computer simulation program was created for predicting the boride layer thickness

M. Keddam; S. M. Chentouf

2005-01-01

189

Seeded growth of HgZnTe by directional solidification using an initial composition profile simulating a ``diffusion-boundary'' layer  

NASA Astrophysics Data System (ADS)

Hg 0.84Zn 0.16Te crystals were grown vertically by back-melting a series of precast segments followed by directional solidification. The predetermined composition profiles of these segments simulate the distribution of a "diffusion boundary" layer in the melt ahead of the solid-melt interface during the directional solidification experiment. Composition analysis of the grown crystals confirm that steady-state growth were achieved from the beginning of the growth process.

Sha, Yi-Gao; Su, Ching-Hua; Alexander, H. A.; Lehoczky, S. L.; Wang, J.-C.

1997-04-01

190

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

191

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

192

What's a Cavity?  

MedlinePLUS

... Flu Shot? The Pink Locker Society What's a Cavity? KidsHealth > Kids > Q&A > Q & A > What's a ... while you're getting your new filling. Continue Cavity Prevention Tips Though cavities can be repaired, try ...

193

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

NASA Astrophysics Data System (ADS)

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, flow, and fracture. Experimental variables include saturation pressure and duration, and shape and lubrication of the flow path. Bubble growth in the experiments controls both flow and fracturing, and is consistent with physical models of magma vesiculation. Two types of fractures are observed: i) sharp fractures along the uppermost rim of the sample, and ii) fractures pervasively diffused throughout the sample. Rim fractures open when shear stress accumulates and strain rate is highest at the margin of the flow (a process already inferred from observations and models to occur in magma). Pervasive fractures originate when wall-friction retards expansion of the sample, causing pressure to build-up in the bubbles. When bubble pressure overcomes wall-friction and the tensile strength of the porous sample, fractures open with a range of morphologies. Both types of fracture open normally to flow direction, and both may heal as the flow proceeds. These experiments also illustrate how the development of pervasive fractures allows exsolving gas to escape from the sample before the generation of a permeable network via other processes, e.g., bubble coalescence. This is an observation that potentially impact the degassing of magma and the transition between explosive and effusive eruptions.

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

2006-03-01

194

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

195

Osteogenesis by chondrocytes from growth cartilage of rat rib  

Microsoft Academic Search

Chondrocytes were isolated from growth cartilage and resting cartilage of rat rib and cultivatedin vitro. The cultivated chondrocytes were placed in Millipore diffusion chambers, which were then implanted into the abdominal cavities\\u000a of rats for several weeks and prepared for histological analysis. The results indicate that growth cartilage cells have a\\u000a remarkable osteogenic potential, even after cultivationin vitro, whereas resting

Y. Shimomura; T. Yoneda; F. Suzuki

1975-01-01

196

Photon confinement in photonic crystal cavities  

NASA Astrophysics Data System (ADS)

In this thesis, the use of photonic crystal cavities for experiments in cavity quantum-electrodynamics is described. To this end, the propagation of light in photonic crystals, and the creation of cavities by making defects in the photonic crystal lattice, is discussed. By drawing an analogy with Fabry-Perot etalons, the mechanism of light confinement in these cavities is explained. It is shown that by engineering the immediate cavity neighborhood, the mirror reflectivities can be increased, resulting in a very high quality factor (Q) and low mode volume. Photonic crystal cavity designs used in this thesis are introduced, along with numerically computed data of their performance. Device fabrication in gallium arsenide wafers is described in detail, with special attention to address factors that lead to a lack of reproducibility. Over the course of this thesis effort, several thousand cavities were fabricated, and a wide range of Qs were recorded. Careful experiments were performed to determine the causes of low Qs, both at the wafer growth level, and at the fabrication level. Technological improvements in wafer growth are reported, as well as fabrication techniques to improve cavity Q. These cavities contain indium arsenide quantum dots (QDs) as internal light sources. Cavity-induced enhancement of QD light emission is discussed, along with interferometric measurements of photon correlations. It is found that light emission from coupled QD-cavity systems is highly non-classical, and this quantum nature is characterized by means of a second order correlation function. To conclude, a novel application of high-Q cavities is discussed, that of an electrically-pumped laser fabricated in a 1D nanobeam cavity. The salient feature of such a geometry is that a high Q is retained even with the introduction of gold in the cavity vicinity. Finally, approaches to improve cavity Q by material system optimizations are explored. In the first approach, QD growth in III-V material systems with light emission wavelengths in the telecommunications wavelength range (lambda ? 1.55 ?m) is discussed, and in the second, the growth of III-V-based active media in silicon structures is considered.

Khankhoje, Uday Kiran

197

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

198

Segmented trapped vortex cavity  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

199

Microwave cavity antennas  

Microsoft Academic Search

Advances in the design of microwave cavity antennas are discussed, surveying both Western and Soviet work for the period 1950-1988. The fundamental principles and classification of cavity antennas are reviewed, and particular attention is given to cavity-backed antennas; translucent-aperture cavity antennas; cavity-backed, crossed-dipole-fed, helical, and spiral antennas; short-backfire antennas; and long-backfire antennas. Extensive diagrams, drawings, graphs, and photographs are provided.

A. Kumar; H. D. Hristov

1989-01-01

200

Plasma growth hormone (GH) responses after administration of the peptidergic GH secretagogue KP102 into the oral cavity, rumen, abomasum and duodenum in adult goats  

Microsoft Academic Search

The study was performed to determine whether orally administered KP102 (also known as GHRP-2) stimulates GH release in adult goats, and how the orally administered KP102 passes through the digestive tract and stimulates GH release in ruminant animals. Five mg\\/kg body weight (BW) of KP102 dissolved in 9 ml of saline were administered into the oral cavity, rumen, omasum and

T Hashizume; Y Tanabe; K Ohtsuki; A Mori; N Matsumoto; S Hara

2001-01-01

201

A diffusion model for describing the bilayer growth (FeB/Fe 2B) during the iron powder-pack boriding  

NASA Astrophysics Data System (ADS)

In this paper, a diffusion model is proposed for studying the bilayer growth kinetics (FeB/Fe 2B) on pure iron substrate during the powder-pack boriding in the temperature range of 1023-1273 K. This model based on Fick's laws was solved, under certain assumptions, considering a parabolic growth of iron borides. For this purpose, a computer simulation program was created for predicting the boride layer thickness as a function of process parameters (temperature, time and surface boron content). A fairly good agreement was observed between the simulation calculations and experimental data derived from the literature.

Keddam, M.; Chentouf, S. M.

2005-10-01

202

Human normal B lymphocytes produce a growth-promoting activity for granulocyte progenitors in diffusion chamber culture after stimulation with pokeweed mitogen.  

PubMed

We have measured the effect of normal B lymphocytes on more primitive granulocyte progenitors (CFU-dG) clonal growth in double-diffusion chamber culture in vivo. It was found that pokeweed mitogen (PWM) stimulated B cells produce a growth-promoting activity which augments the CFU-dG--derived myeloid colony formation in a dose-dependent fashion. All colonies formed under the experimental conditions were composed exclusively of granulocytes at different stages of maturation. Unstimulated B lymphocytes did not effect the CFU-dG clonal proliferation. PMID:1709901

Hansz, J; Koz?owska-Skrzypczak, M

1990-01-01

203

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

204

Coupling cavity damper for the ARES cavity  

Microsoft Academic Search

The coaxial (WX120D) antenna damper has been developed for damping the parasitic 0 and pi modes of the KEKB ARES cavity. It is installed in the coupling cavity of the ARES. The damper consists of a disk-type coaxial ceramic window and a cross stub support. The cross stub is used in order to run the cooling water through the antenna

F. Naito; K. Akai; N. Akasaka; E. Ezura; T. Kageyama; H. Mizuno; H. Nakanishi; H. Sakai; Y. Takeuchi; Y. Yamazaki; T. Kobayashi

1997-01-01

205

Carbohydrates and Cavities  

MedlinePLUS

... Celiac disease. Tip of the Day Carbohydrates and Cavities October is Dental Hygiene Month, a great time ... to improve your dental health. Whether you get cavities depends on many things, including heredity, oral hygiene, ...

206

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

PubMed Central

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

Cane, Gaelle; Moal, Vanessa Lievin-Le; Pages, Gilles; Servin, Alain L.; Hofman, Paul; Vouret-Craviari, Valerie

2007-01-01

207

A selection of high gradient cavity experiments  

SciTech Connect

In the two years since the 7th SRF workshop, a variety of cavity tests have been carried out with the objective to reproducibly achieve surface electric rf fields above 40 MV/m with no or only very little electron loading. This paper reports about a collection of tests on single cell and multi-cell cavities, which received standard surface treatments such as buffered chemical polishing and high pressure ultrapure water rinsing, but no heat treatments. Often the cavities were limited by quenches, posting a limit of 700 to 1,000 Oersted on achievable peak magnetic fields of high purity niobium RRR values between 200 and 250. In a seamless single cell cavity fabricated by V. Palmieri of INFN Legnaro by spinning, a very promising gradient of E{sub acc}=25 MV/m was measured. In collaboration with CERN, several tests on sputtering niobium prepared at CERN were also carried out, and accelerating gradients up to 25 MV/m were achieved. A single cell cavity, electron beam welded after electrochemical buffing, showed only good performance--E{sub p} > 50 MV/m--after the removal of more than 100 {micro}m of material. However, this cavity showed rather heavy Q disease even when cooled down rapidly; the Q degradation could be partially reversed by diffusing the oxygen from an anodized Nb{sub 2}O{sub 5} layer into the niobium by heating the cavity in-situ at T=250 C.

Peter Kneisel

1998-01-01

208

All about Cavities  

MedlinePLUS

All About Cavities What's in Your Mouth? How Your Teeth Decay Types of Decay Preventing Cavities What's in Your Mouth? To understand what happens ... the plaque teems with bacteria that can cause cavities and periodontal (gum) disease. Calculus — If left alone ...

209

Surface diffusion processes in molecular beam epitaxial growth of GaAs and AlAs as studies on GaAs (001)-(111)B facet structures  

NASA Astrophysics Data System (ADS)

Mechanisms of molecular beam epitaxy have been investigated for GaAs and AlAs by growing and analyzing the shapes of facet structures consisting of an (001) top surface and two (111)B side surfaces. It is found that all of the Ga flux on the three facet planes is incorporated into the film, but the growth rates on (111)b AND (001) depend strongly on the As flux and are mainly determined by the diffusion of Ga ad-atoms between the two planes. In contrast, the diffusion of Al is found to be almost negligible, irrespective of the As flux. By analyzing the shape of the facet, the diffusion length, lambda, of Ga on a (001) surface is estimated to be about 1 micrometers at 580 C, while that of Al is about 0.02 micrometers. On (111)B, lambda of Ga is found to be serveral micrometers. The reflectivity of diffusing Ga atoms is found to be far less than 1 for the (001)-(111)B boundary, and almost unity at facet boundaries where the (111)B side surfaces are bound by the (1 -1 0) side walls.

Koshiba, S.; Nakamura, Y.; Tsuchiya, M.; Noge, H.; Kano, H.; Nagamune, Y.; Noda, T.; Sakaki, H.

1994-10-01

210

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

PubMed Central

We investigated the interplay between surface trafficking and binding dynamics of the immunoglobulin cell adhesion molecule L1 at neuronal growth cones. Primary neurons were transfected with L1 constructs bearing thrombin-cleavable green fluorescent protein (GFP), allowing visualization of newly exocytosed L1 or labeling of membrane L1 molecules by Quantum dots. Intracellular 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.

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

2007-01-01

211

Effects of Y 2O 3 additions on the oxygen diffusion in top-seeded melt growth processed YBa 2Cu 3O 7-y superconductors  

NASA Astrophysics Data System (ADS)

To understand the effect of Y 2BaCuO 5 (Y211)/YBa 2Cu 3O 7-y (Y123) interfaces on the oxygen diffusion in single grain YBa 2Cu 3O 7-y superconductors, single grain Y123 superconductors with 0.05 and 0.3 moles of Y 2O 3 additions were fabricated by a top-seeded melt growth (TSMG) process. Y123 compacts with Y 2O 3 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 Y 2O 3 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 Y 2O 3 addition were higher than those of the same regions of the Y123 sample with 0.05 mole Y 2O 3 addition due to the promoted oxygen diffusion through Y211/Y123 interfaces and other related defects. In spite of the promoted oxygen diffusion by Y 2O 3 addition, the large T c 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

212

Micromechanical modeling of the interaction of diffusion mechanisms and surface energy with nonlinear material deformation: Applications to powder densification and void growth  

NASA Astrophysics Data System (ADS)

Diffusive processes coupled to nonlinear material behavior assume importance in such important technological problems as consolidation of powders, diffusive cavitation at grain-boundary interfaces, and void growth and coalescence in solids. The first three chapters of this thesis are devoted to the study of powder densification using a small-strain finite-element scheme. In the first chapter, the coupled action of stress-driven diffusion and curvature-driven diffusion over the interparticle contact areas and the pore surfaces respectively, and elasticity and power-law creep processes in the bulk of the particles is studied. Numerical results indicate that the interaction of the deformation mechanisms is very important in determining the overall densification rates of the powder aggregate, and that models that focus on a single, dominant densification mechanism underestimate the densification rate. In the second chapter, the macroscopic strain rate of a particle aggregate is obtained from an analytically-constructed and numerically-obtained potential function in terms of the applied loads, the relative density of the compact, and material parameters. The predictions of this potential agree quantitatively with experimentally obtained densification data for copper wires. The interparticle diffusion process is modified in the third chapter to account for the situation when part of the externally delivered power is expended in driving the interface reaction (addition to or removal of atoms from the interparticle boundaries). Numerical computations reproduce experimentally observed decrease in overall densification rates with increasing interface reaction strength. In order to study densification to a larger range of relative density, the densification problem is recast in finite-strain form in the fourth chapter, and it is observed that the small-strain model underestimates the relative density increase for a given amount of time. Void growth in nonlinearly creeping solids under plane-strain conditions is studied in the fifth chapter. Numerical results reveal a rich variety of solutions; in general, void shape is controlled by the strength of the diffusion process relative to the bulk creep process, whereas void size depends critically on the surface energy of the void in relation to the void size and applied load.

Subramanian, Sankara Jayaraman

2001-07-01

213

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

Microsoft Academic Search

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

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

2011-01-01

214

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

215

Spectral effective emissivities of nonisothermal cavities calculated by the Monte Carlo method  

NASA Astrophysics Data System (ADS)

An algorithm based on the Monte Carlo method is described that permits the precise calculation of radiant emission characteristics of nonisothermal blackbody cavities for use as standard sources in radiometry, photometry, and radiation thermometry. The algorithm is realized for convex axisymmetric specular-diffuse cavities formed by three conical surfaces. The numerical experiments provide estimates of normal effective emissivities of cylindrical blackbody cavities with flat or conical bottoms for various axisymmetric temperature distributions on the cavity walls.

Sapritsky, V. I.; Prokhorov, A. V.

1995-09-01

216

Cavity enhanced terahertz modulation  

NASA Astrophysics Data System (ADS)

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

Born, N.; Scheller, M.; Koch, M.; Moloney, J. V.

2014-03-01

217

Optically measuring interior cavities  

DOEpatents

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

Stone, Gary Franklin (Livermore, CA)

2008-12-21

218

Optically measuring interior cavities  

DOEpatents

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

Stone, Gary Franklin (Livermore, CA)

2009-11-03

219

Characterization of cavity wakes  

NASA Astrophysics Data System (ADS)

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

Kidd, James A.

220

Effect of H and He irradiation on cavity formation and blistering in ceramics  

NASA Astrophysics Data System (ADS)

Single- or poly-crystalline specimens of SiC, Si3N4, MgO, Al2O3 and MgAl2O4 were implanted with 0.4-1 MeV H+ or He+ ion beams at room temperature and 650 °C up to fluences of ˜1 × 1022/m2. This produced peak implanted gas and displacement damage levels as high as ˜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 × 1021/m2 (˜15 at.% peak implanted gas concentration), and surface exfoliation occurred for fluences above ˜1 × 1022/m2 (˜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: (0 0 0 1) and {1 1¯ 0 0} for Al2O3, (0 0 0 1) for ?-SiC, {0 0 1} and {1 1 0} for MgO, and {1 1 0} and {1 1 1} for MgAl2O4. 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, S. J.

2012-09-01

221

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

222

Correlation between film thickness and zinc defect distribution along the growth direction in an isotopic multilayer ZnO thin film grown by pulsed laser deposition analyzed using the internal diffusion method  

NASA Astrophysics Data System (ADS)

Zinc self-diffusion along the growth direction was analyzed for the isotopic multilayer ZnO thin film (( 64ZnO/ 68ZnO) 664ZnO) deposited by pulsed laser deposition. The isotopic distribution was measured using a secondary ion mass spectrometry. The amplitude of the 64Zn abundance in the depth profile was reduced by annealing at 993 K for several hours due to interdiffusion between the 64ZnO and 68ZnO layers. The diffusion profiles at the isotopic interfaces were analyzed using a periodic equation. The obtained zinc self-diffusion coefficients at several isotopic interfaces along the growth direction showed that the self-diffusion coefficients increased towards the film/substrate interface. A similar trend was also found in the lateral direction. The variation among the self-diffusion coefficients was related to the film thicknesses at the analysis positions. Since zinc self-diffusion is controlled by a vacancy-mediated mechanism, the variation in zinc diffusivity along the growth direction can be attributed to the effect of compressive biaxial stress. These findings are useful for producing high-quality ZnO devices.

Matsumoto, Kenji; Adachi, Yutaka; Ohgaki, Takeshi; Ohashi, Naoki; Haneda, Hajime; Sakaguchi, Isao

2010-11-01

223

LHC Beam Diffusion Dependence on RF Noise: Models And Measurements  

SciTech Connect

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

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

2010-09-14

224

Transverse diffusion of proton beams due to noise  

Microsoft Academic Search

Diffusion due to random transverse forces is calculated for proton beams. The result is applied to the case of a colliding electron current and the tolerable level of noise calculated. The result is also applied to radiofrequency cavities and it is concluded that transverse diffusion due to these cavities should not be a difficult problem. 5 refs.

Channell

1973-01-01

225

An epigenetic chromatin remodeling role for NFATc1 in transcriptional regulation of growth and survival genes in diffuse large B-cell lymphomas  

PubMed Central

The nuclear factor of activated T cells (NFAT) family of transcription factors functions as integrators of multiple signaling pathways by binding to chromatin in combination with other transcription factors and coactivators to regulate genes central for cell growth and survival in hematopoietic cells. Recent experimental evidence has implicated the calcineurin/NFAT signaling pathway in the pathogenesis of various malignancies, including diffuse large B-cell lymphoma (DLBCL). However, the molecular mechanism(s) underlying NFATc1 regulation of genes controlling lymphoma cell growth and survival is still unclear. In this study, we demonstrate that the transcription factor NFATc1 regulates gene expression in DLBCL cells through a chromatin remodeling mechanism that involves recruitment of the SWItch/Sucrose NonFermentable chromatin remodeling complex ATPase enzyme SMARCA4 (also known as Brahma-related gene 1) to NFATc1 targeted gene promoters. The NFATc1/Brahma-related gene 1 complex induces promoter DNase I hypersensitive sites and recruits other transcription factors to the active chromatin site to regulate gene transcription. Targeting NFATc1 with specific small hairpin RNA inhibits DNase I hypersensitive site formation and down-regulates target gene expression. Our data support a novel epigenetic control mechanism for the transcriptional regulation of growth and survival genes by NFATc1 in the pathophysiology of DLBCL and suggests that targeting NFATc1 could potentially have therapeutic value.

Tamayo, Archito T.; Li, Changping; Bueso-Ramos, Carlos; Ford, Richard J.

2010-01-01

226

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

PubMed

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

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

2014-05-01

227

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

228

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

229

Diffusion-reaction modeling of silicon oxide interlayer growth during thermal annealing of high dielectric constant materials on silicon  

Microsoft Academic Search

We present the quantitative physicochemical modeling of the thermal annealing of high dielectric constant (k) thin films on silicon in oxygen and\\/or inert ambient. In particular, we study the kinetics of the SiO2 interfacial layer growth at the high- k material structure\\/Si interface. Upon annealing, the transport of oxygen species in the high- k film to the silicon interface is

Deepthi Gopireddy; Christos G. Takoudis

2008-01-01

230

What Are Nasal Cavity and Paranasal Sinus Cancers?  

MedlinePLUS

... not cancers, but they may still cause problems. Nasal polyps Nasal polyps are abnormal growths inside the nasal cavity or ... and tend to have a smooth surface. Most nasal polyps are benign (non-cancerous) and are caused by ...

231

Tuned optical cavity magnetometer  

DOEpatents

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

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

2010-11-02

232

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

PubMed Central

Apogossypolone (ApoG2) is a semi-synthesized derivative of gossypol. The principal objective of this study was to compare stability and toxicity between ApoG2 and gossypol, and to evaluate anti-lymphoma activity of ApoG2 in vitro and in vivo. ApoG2 shows better stability when compared with a racemic gossypol and can be better tolerated by mice compared to gossypol. ApoG2 showed significant inhibition of cell proliferation of WSU-DLCL2 and primary cells obtained from lymphoma patients, whereas it displayed no toxicity on normal peripheral blood lymphocytes. For a treatment of 72 h, the IC50 of ApoG2 was determined to be 350 nM against WSU-DLCL2 cells. Treatment with ApoG2 at 600 mg/kg resulted in significant growth inhibition of WSU-DLCL2 xenografts. When combined with CHOP, ApoG2 displayed even more complete inhibition of tumor growth. ApoG2 binds to purified recombinant Bcl-2, Mcl-1 and Bcl-XL proteins with high affinity and is shown to block the formation of heterodimers between Bcl-XL and Bim. For a treatment of 72 h, ApoG2 induced a maximum of 32% of apoptotic cell death. Western blot experiments showed that treatment with ApoG2 led to cleavage of caspase-3, caspase-9 and PARP. Moreover, pretreatment of DLCL2 cells with caspase-3, -9 and broad spectrum caspase inhibitors significantly blocked growth inhibition induced by ApoG2. In conclusion, ApoG2 effectively inhibits growth of DLCL2 cells at least partly by inducing apoptosis. It is an attractive small molecule inhibitor of the Bcl-2 family proteins to be developed further for the treatment of diffuse large cell lymphoma.

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

2014-01-01

233

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

PubMed

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

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

2008-09-01

234

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

235

Radial profiling of microdroplets using cavity-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The composition of 7.7- mu m-radius methanol-water droplets was radially resolved by cavity-enhanced Raman spectroscopy. Optical cavity modes, encompassing well-defined radial zones within each droplet, were sequentially excited by a 514.5-nm laser beam to generate spontaneous Raman scattered light. The cavity-enhanced Raman spectral peaks gave information as to the identity and amount of species present. The measured radial and time dependence of the methanol concentration agreed with a diffusion-limited evaporation mode.

Lin, H.-B.; Campillo, A. J.

1995-08-01

236

Multiple membrane cavity optomechanics  

NASA Astrophysics Data System (ADS)

We investigate theoretically the extension of cavity optomechanics to multiple membrane systems. We describe the simplest case of two membranes in a cavity, in terms of the coupling of the light fields to the breathing and center-of-mass modes of the membrane array. We show that these normal modes can be optically addressed individually and also be cooled, trapped, and characterized, e.g., via quantum nondemolition measurements. The extension to a larger number of membranes is briefly discussed.

Bhattacharya, M.; Meystre, P.

2008-10-01

237

Tungsten diffusion in silicon  

NASA Astrophysics Data System (ADS)

Two doses (1013 and 1015 cm-2) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960 °C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%-0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.

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

2014-01-01

238

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

2010-02-10

239

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

PubMed

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

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

2012-02-28

240

Diffusion-controlled growth of molecular heterostructures: fabrication of two-, one-, and zero-dimensional C(60) 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

2013-10-01

241

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

NASA Technical Reports Server (NTRS)

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

Wendt, Bruce J.

2000-01-01

242

RF Cavity Characterization with VORPAL  

Microsoft Academic Search

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

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

2011-01-01

243

What Are Oral Cavity and Oropharyngeal Cancers?  

MedlinePLUS

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

244

Lateral coupled cavity semiconductor laser  

SciTech Connect

This patent describes a monolithic lateral-coupled laser array comprised of at least two stripe laser cavities of different effective length in close parallel proximity to each other for coupling of radiation. The longer of the stripe laser cavities is cleaved to provide separate parts, and the parts are cleaved coupled to form one strip laser cavity lateral coupled to the shorter laser cavity. A separate stripe contact varies the relative currents supplied to each laser cavity, including the cleaved coupled cavities of the longer of the stripe laser cavities.

Salzman, J.; Lang, R.J.; Yariv, A.

1987-06-16

245

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

2013-03-01

246

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

NASA Astrophysics Data System (ADS)

Atomic force microscopy (AFM) has been used to study the hollow cavity formation mechanisms of the L-arginine phosphate monohydrate (LAP) crystals. Hollow cavities are formed through three modes. During 2D nucleation growth, initially formed 2D cavity prevents the growth around it layer-by-layer and causes the formation of 3D cavity with stepped-walls inside. Interaction of the steps advancing along different directions generated by different dislocation sources is also responsible for the appearance of hollow cavities. When the steps overrun impurities incorporated into the kinks, triangular pits among regular elementary steps come into being.

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

247

Ring resonant cavities for spectroscopy  

DOEpatents

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

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

1999-01-01

248

Ring resonant cavities for spectroscopy  

DOEpatents

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

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

1999-06-15

249

Video Toroid Cavity Imager  

DOEpatents

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

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

2004-08-10

250

Anti-adhesive membrane for pleural cavity.  

PubMed

An anti-adhesive membrane containing a large amount of glycerin was developed for lung surgery and was tested in the pleural cavity of six dogs. The test membranes were put between the lung and the chest wound of the pleural cavity wall to separate them. In five of the animals, no adhesion was observed after 3 weeks in the area where the membrane had been inserted, but the area without the membrane showed firm adhesion between the lung and the pleural cavity wall. A sixth animal observed for 3 months also showed no adhesion. Seprafilm, which is the product of choice for peritoneal surgeries, was used as a control in six dogs. Seprafilm could not prevent adhesion in the pleural cavity of all six animals after 3 weeks observation. The new test membrane contained glycerin, which gathered and dispersed abundant water. Together with this, growth factors are also dispersed, resulting in dilution of excessive growth factors at the wound sites. In general, fibroblasts do not migrate in an extremely hydrous gel matrix. Migration of fibroblasts into the membrane is minimized, resulting in the prevention of formation of adhesion tissue composed of fibroblasts and collagen fibers. From the results, we assume that water can prevent adhesion after surgery. PMID:20447048

Noishiki, Yasuharu; Shintani, Noriyuki

2010-03-01

251

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

252

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

253

Precision tunable resonant microwave cavity  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

254

Apparent absorption in a paraboloid of revolution-shaped cavity irradiated by a focused beam  

Microsoft Academic Search

The apparent or integrated energy absorbed by the welding or drilling cavity subject to a focused beam is investigated in this paper. The cavity is assumed to be paraboloid of revolution and the incident flux is considered to be a Gaussian distribution specified by the divergence angle, focal spot size and focal location. Accounting for multiple specular and diffuse reflections

C. Y. Ho; Chung Ho

2005-01-01

255

Model of Mercury Vapor Transport from Amalgam Restorations in the Oral Cavity  

Microsoft Academic Search

A model of the oral cavity was used as the basis for a discussion of the conditions prevalent during the transport of mercury vapor from amalgam restorations via the saliva to the gas phase of the oral cavity during respiration or during pumping of air through the mouth. It was found that the mercury diffusion rate through the saliva layer

S. Olsson; A. Berglund; L. Pohl; M. Bergman

1989-01-01

256

Change of RF superconductivity parameters induced by heat treatment on niobium cavities  

Microsoft Academic Search

We have investigated the thermal quench evolution of a Niobium cavity, chemically polished, during ultra high vacuum annealings from 100 to 800°C. Ten cavities have been tested before heat treatment (HT) and the results show a good agreement with the BCS theory for a diffuse reflection of the conduction electrons on the metal surface. All along the HT we have

B. Visentin; J. P. Charrier; G. Congretel

2001-01-01

257

Electromagnetic SCRF Cavity Tuner  

Microsoft Academic Search

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

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

2009-01-01

258

Seamless/bonded niobium cavities  

NASA Astrophysics Data System (ADS)

Technological aspects and performance of seamless cavities produced by hydroforming are presented. Problems related to the fabrication of seamless cavities from bulk niobium are mainly solved thanks to the progress of the last years. The highest achieved accelerating gradients are comparable for both seamless and welded versions (ca. 40 MV/m) Nevertheless further development of seamless cavities is desirable in order to avoid the careful preparation of parts for welding and get reliable statistic. Fabrication of NbCu clad cavities from bimetallic tubes is an interesting option that gives new opportunity to the seamless technique. On the one hand it allows reducing the niobium costs contribution; on the other hand it increases the thermal stability of the cavity. The highest accelerating gradient achieved on seamless NbCu clad single cell cavities (ca. 40 MV/m) is comparable to the one reached on bulk Nb cavities. Fabrication of multi-cell NbCu cavities by hydroforming was recently proven.

Singer, W.

2006-07-01

259

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

260

Validation of Ultrasonography to Evaluate Murine Orthotopic Oral Cavity Tumors  

Microsoft Academic Search

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

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

2006-01-01

261

In Vivo Toxicity of Arsenic Trioxide for Human Cells in Diffusion Chambers.  

National Technical Information Service (NTIS)

The diffusion chamber system was used to monitor the toxicity of trivalnet arsenic for human target cells in vivo. Cell-impermeable diffusion chambers containing human embryonic lung cells were implanted into the peritoneal cavity of hamsters that one day...

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

1986-01-01

262

Automated measurement of cavity frequency and cavity tuning at CEBAF  

SciTech Connect

We propose a method here which allows the measurement of the cavity resonance frequency in a frequency range up to {plus_minus}5 kHz from the operating frequency. This is achieved by phase modulation of the incident signal with noise to drive the cavity with a broad band spectrum. The cavity resonance frequency can then be determined from the response signal of the field probe, which has a narrow frequency spectrum due to the high loaded Q of the cavity of 6.6{times}10{sup 6}, corresponding to a cavity bandwidth of 125 Hz.

Li, Rui; Simrock, S.N.; Yunn, Byung C.

1993-06-01

263

Lateral coupled cavity semiconductor laser  

Microsoft Academic Search

This patent describes a monolithic lateral-coupled laser array comprised of at least two stripe laser cavities of different effective length in close parallel proximity to each other for coupling of radiation. The longer of the stripe laser cavities is cleaved to provide separate parts, and the parts are cleaved coupled to form one strip laser cavity lateral coupled to the

J. Salzman; R. J. Lang; A. Yariv

1987-01-01

264

Hollow waveguide cavity ringdown spectroscopy  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

265

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

266

Diffusion-Limited Aggregation with Active Edge Diffusion  

NASA Astrophysics Data System (ADS)

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

Röder, Holger; Bromann, Karsten; Brune, Harald; Kern, Klaus

1995-04-01

267

Polychromatic photonic quasicrystal cavities.  

PubMed

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

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

2010-06-18

268

Oral cavity and pharynx.  

PubMed

Imaging of the oral cavity and pharynx often is required in three settings: assessment of an inflammatory mass in association with odontogenic, tonsillar, or pharyngeal infections; determination of the cause of a submucosal mass; and staging of squamous-cell carcinomas. Spread of infection from the oral cavity and pharynx can lead to abscesses in the masticatory space, the retropharyngeal compartment, and in a parapharyngeal location. Submucosal masses include congenital cysts (thyroglossal and dermoid), benign neoplasms (hemangioma, schwannomas, pleomorphic adenomas juvenile angiofibromas), inflammatory cysts (mucous retention cysts, ranulas), and pseudotumors (osteophytes, carotid arteries). Staging of squamous-cell carcinomas must focus on deep invasion, spread to the brain, nerves, mandible, prevertebral muscle, and pre-epiglottic fat. PMID:9747196

Yousem, D M; Chalian, A A

1998-09-01

269

Oral Cavity Surgery Codes  

Cancer.gov

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

270

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

271

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

PubMed

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

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

2013-12-01

272

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

273

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

274

Interaction of cavities with misfit dislocations in SiGe/Si heterostructures  

SciTech Connect

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

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

1996-09-01

275

Pb-Zn liquid metal diffusion  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

276

Breakdown in rf cavities.  

SciTech Connect

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

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

2005-01-01

277

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

278

Cavity soliton billiards  

NASA Astrophysics Data System (ADS)

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.; Tissoni, G.; Brambilla, M.

2011-11-01

279

Spatial response of cavity systems  

SciTech Connect

We show that a plane-mirror Fabry-Perot cavity is capable of converting a spatially phase (amplitude) modulated input beam into an amplitude (phase) modulated output. For a cavity close to resonance the effect is most easily seen for negative detunings. When nonlinear elements are added to the mean-field cavity, the effect persists but acquires an intensity dependence, while the requirement of net negative dispersion remains. In addition, the output of a near-resonant nonlinear cavity can have the same type of modulation as the input, something which is impossible in the corresponding linear cavity. These results are demonstrated in cavities containing Kerr or two-level materials, as well as in optical parametric oscillators.

Scroggie, A.J.; Jeffers, J.; McCartney, G.; Oppo, G.-L. [Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 ONG, Scotland (United Kingdom)

2005-08-15

280

Fabrication of Niobium Rf Cavities  

Microsoft Academic Search

A new process for fabricating niobium rf cavities for use in beam separators and linear accelerators is described. The best performance to date for a cavity made by this process was obtained with a TE011 mode cavity, operating at 11.2 GHz at a peak magnetic field of ?500 G, for which Q≈2×1010. The principle advantages of the process described over

R. W. Meyerhoff

1969-01-01

281

Multicolor cavity metrology.  

PubMed

Long-baseline laser interferometers used for gravitational-wave detection have proven to be very complicated to control. In order to have sufficient sensitivity to astrophysical gravitational waves, a set of multiple coupled optical cavities comprising the interferometer must be brought into resonance with the laser field. A set of multi-input, multi-output servos then lock these cavities into place via feedback control. This procedure, known as lock acquisition, has proven to be a vexing problem and has reduced greatly the reliability and duty factor of the past generation of laser interferometers. In this article, we describe a technique for bringing the interferometer from an uncontrolled state into resonance by using harmonically related external fields to provide a deterministic hierarchical control. This technique reduces the effect of the external seismic disturbances by 4 orders of magnitude and promises to greatly enhance the stability and reliability of the current generation of gravitational-wave detectors. The possibility for using multicolor techniques to overcome current quantum and thermal noise limits is also discussed. PMID:23201656

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

2012-10-01

282

Externally deposited phase-compensating dielectric mirrors for asymmetric Fabry-Perot cavity tuning  

Microsoft Academic Search

The wavelength dispersion of the phase shift on reflection that is inherent in dielectric Bragg mirrors can be used to phase compensate resonant-cavity-based devices such as multiple quantum well asymmetric Fabry–Perot spatial light modulators and vertical cavity surface-emitting lasers. We demonstrate the post-growth ability to accurately fine-tune the location of the Fabry–Perot minima in a resonant cavity by employing either

Z. Karim; C. Kyriakakis; A. R. Tanguay Jr.; K. Hu; L. Chen; A. Madhukar

1994-01-01

283

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

284

Anomalous Diffusion Near Resonances  

SciTech Connect

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

Sen, Tanaji; /Fermilab

2010-05-01

285

Accessory oral cavity.  

PubMed

This is a rare case report of a patient around 11 years with the complaint of extra mouth who reported to the hospital for removal of that extra mouth. On examination there was accessory oral cavity with small upper and lower lips, seven teeth and saliva was drooling out. Under general anesthesia crevicular incision from 32 to 43 was put and labial gingiva with alveolar mucosa was reflected completely and bone exposed to lower border of mandible. There were seven teeth resembling lower permanent anterior teeth in the accessory mouth, which was excised with the accessory lips. 41 extracted and osteotomy carried out extending the incision from the extracted site and osteotomy carried out. Dermoid cyst both below and above the mylohyoid muscle and rudimentary tongue found and excised and the specimen sent for histopathological examination. The wound was closed and uneventful healing noted to the satisfaction of the patient. This is a rare and interesting case which has been documented. PMID:23833508

Gnaneswaran, Manica Ramamoorthy; Varadarajan, Usha; Srinivasan, Ramesh; Kamatchi, Sangeetha

2012-07-01

286

Destabilization of diocotron modes inside structured anode cavities  

NASA Astrophysics Data System (ADS)

Previous stability analysis of low space charge ?e2/?2<<1, E×B drifting flows inside smooth anode cavities has shown that they are practically stable against slow wave ?/ck<<1 diocotron instabilities when the flow touches the cathode (cathode layer). It is shown here that the presence of periodically structured anode destabilizes cathode layer modes when their phase velocity matches that of an empty cavity eigenmode, as structured cavities support slow waves in vacuum. An analytic dispersion relation that self-consistently includes the structured anode effects is obtained in the guiding center approximation. The growth rate, related to the onset of magnetron oscillations, scales as ?/?~?D/?~=1/kd it is independent of, and remains finite as, ?e2/?2-->0. The most unstable frequency corresponds to a resonant layer below the flow surface (slightly below the Buneman-Hartree frequency) and the growth rate is found symmetric relative to the detuning from resonance.

Riyopoulos, Spilios

1999-01-01

287

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

288

External Cavity Coherent Transmitter Modules.  

National Technical Information Service (NTIS)

This report covers work done with a Fabry-Perot semiconductor laser based external cavity structure, for use with coherent fiber optical communications systems. A novel structure was developed which uses a single-mode fiber as part of the external cavity,...

H. Sunak

1990-01-01

289

ANGIOSARCOMA OF THE ORAL CAVITY  

Microsoft Academic Search

An angiosarcoma is described, localized in the oral cavity and diagnosed rather late after its marked manifes- tation. The authors focus on the differential diagnosis of he- mangioendothelioma and hemangiopericytoma, recom- mending early and relevant studies in cases of tumour in- vasion in the oral cavity. shadows in the pulmonary areas, which were likely to be related to the principal

Emil Sarachev; G. Mateeva

290

Optical discharge in laser cavity  

NASA Astrophysics Data System (ADS)

Experimental investigations of the absorption of laser radiation in the optical discharge when placed in the laser cavity were conducted. A significant increase in the absorption until complete absorption was established. An optical schemes of the initiation and maintenance of the optical discharge in the cavity are proposed, which greatly extends the field of application of optical discharge in technology.

Chivel, Yuri

2013-12-01

291

Quench studies of ILC cavities  

SciTech Connect

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

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

2011-07-01

292

Versatile RF cavity mode damper.  

National Technical Information Service (NTIS)

The ferrite tuned KAON booster synchrotron cavity is coaxial with the beam and operates from 46 to 61 MHz. Higher order modes can be strongly damped by including one or more 50 (Omega) resistors shunted by a 250 MHz annular slot cavity within the accelera...

W. R. Smythe T. A. Enegren R. L. Poirier

1990-01-01

293

Acquired feline oral cavity disease  

Microsoft Academic Search

FIGURES quoted in the literature over the past 30 years indicate that oral cavity disease occurs very commonly in cats as well as in dogs. Unless severe, disease often goes unnoticed or may even be ignored by owner and veterinary surgeon alike. In addition, it is clear that few animals with oral cavity disease actually present with a history from

Norman Johnston

1998-01-01

294

Monochromatic radio frequency accelerating cavity  

DOEpatents

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

Giordano, S.

1984-02-09

295

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

296

Monochromatic radio frequency accelerating cavity  

DOEpatents

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

Giordano, Salvatore (Port Jefferson, NY)

1985-01-01

297

Small angle neutron scattering study of fatigue induced grain boundary cavities  

SciTech Connect

Small angle neutron scattering (SANS) has been used to study grain boundary cavitation in high purity copper fatigued at elevated temperatures. SANS is an extremely sensitive method for observing cavities. Void volume fractions of less than 10/sup -6/ can be detected. Analysis of scattering data yields values for the total void volume per unit volume and the total number of voids in a fatigued sample. The size distribution of the voids also can be calculated. From a series of specimens, each fatigued under identical conditions but for varying lengths of time, it is possible to obtain the void nucleation rate and the rate of growth of the total void volume and of the individual voids. Extrapolation of curves of void volume fraction vs time of fatigue to zero time shows that cavitation begins upon commencement of fatiguing without any measurable incubation time. Void nucleation is continuous throughout fatigue Calculated values of the individual void growth rate agree very well, as regards time dependence, temperature dependence, and even absolute value, with growth rates derived from a theory of fatigueinduced cavitation based on transient effects in vacancy diffusion.

Page, R.; Roth, M.; Weertman, J.R.

1982-07-01

298

Phase and frequency locking of a cavity vircator driven by a relativistic magnetron  

Microsoft Academic Search

Observations of mode selection, frequency locking, and phase locking of a high-power, S-band, cavity vircator oscillator by an externally injected, relativistic magnetron are reported. The injected electric field can increase the virtual cathode oscillation growth rate and defeat chirping. The peak power extracted from the driven vircator cavity is between 100 and 500 MW. The output power from the magnetron

D. Price; H. Sze; D. Fittinghoff

1989-01-01

299

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

300

Hillslope diffusion  

NSDL National Science Digital Library

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

Mcdermott, Jeni

301

Temporary Sealing of Cavities for Leak Testing  

NASA Technical Reports Server (NTRS)

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

Little, J.

1984-01-01

302

Diffusion of sorbing and non-sorbing radionuclides  

Microsoft Academic Search

Diffusion is considered one of the most important retardation mechanisms in fractured media. The diffusion experiments conducted involved solid tuff and groundwater from Yucca Mountain. The uptake of radionuclides by the tuff was studied utilizing containers made of tuff in the form of beakers. The solution containing the radionuclides of interest was placed in the tuff beaker cavity and the

I. R. Triay; K. H. Birdsell; A. J. Mitchell; M. A. Ott

1993-01-01

303

Lasing and cooling in a finite-temperature cavity  

SciTech Connect

We present a microscopic laser model for many atoms coupled to a single-cavity mode, including the light forces, which result from atom-field momentum exchange. Within a semiclassical description, we solve the equations for the atomic motion and the internal dynamics to obtain analytic expressions for the optical potential and the friction force seen by each atom. When optical gain is maximum at frequencies where the light field extracts kinetic energy from the atomic motion, the dynamics combines optical lasing and motional cooling. From the corresponding momentum-diffusion coefficient we predict sub-Doppler temperatures in the stationary state. This generalizes the theory of cavity-enhanced laser cooling to active cavity systems. We identify the gain-induced reduction of the effective resonator linewidth as the key origin for the faster cooling and the lower temperatures, which implies that a bad cavity with a gain medium can replace a high-Q cavity. In addition, this shows the importance of light forces for gas lasers in the low-temperature limit, where atoms can arrange in a periodic pattern maximizing gain and counteracting spatial hole burning. Ultimately, in the low-temperature limit, such a setup should allow us to combine optical lasing and atom lasing in a single device.

Salzburger, Thomas; Ritsch, Helmut [Institute for Theoretical Physics, University Innsbruck, Technikerstrasse 25/2, 6020 Innsbruck (Austria)

2006-09-15

304

Cavity QED with semiconductor nanocrystals.  

PubMed

We report on a strongly coupled cavity quantum electrodynamic (CQED) system consisting of a CdSe nanocrystal coupled to a single photon mode of a polymer microsphere. The strong exciton-photon coupling is manifested by the observation of a cavity mode splitting variant Planck's over 2piOmega(exp) between 30 und 45 microeV and photon lifetime measurements of the coupled exciton-photon state. The single photon mode is isolated by lifting the mode degeneracy in a slightly deformed microsphere cavity and addressing it by high-resolution imaging spectroscopy. This cavity mode is coupled to a localized exciton of an anisotropically shaped CdSe nanocrystal that emits highly polarized light in resonance to the cavity mode and that was placed in the maximum electromagnetic field close to the microsphere surface. The exciton confined in the CdSe nanorod exhibits an optical transition dipole moment much larger than that of atoms, the standard system for CQED experiments, and a low-temperature homogeneous line width much narrower than the high-Q cavity mode width. The observation of strong coupling in a colloidal semiconductor nanocrystal-cavity system opens the way to study fundamental quantum-optics phenomena and to implement quantum information processing concepts that work in the visible spectral range and are based on solid-state nanomaterials. PMID:16522062

Le Thomas, N; Woggon, U; Schöps, O; Artemyev, M V; Kazes, M; Banin, U

2006-03-01

305

Cryogenic High-Conductivity Cavity  

NASA Astrophysics Data System (ADS)

A refrigerated cavity saves a considerable amount of driving power owing to the cryo enhancement in conductivity. An L-band copper cavity is expected to have about six times the room-temperature Q factor at 40 K, which is nowadays easily attainable by a compact refrigerator, and therefore reduce the required power to one sixth. The reduction in operation power enables the use of solid state amplifiers as a compact and handy power source. The combination of the cryogenic high-conductivity cavities and the solid state amplifiers, with each cavity fed separately by each amplifier, provides a flexible accelerating system applicable to a wide range of particle velocities. A post-accelerator for deuterons has been proposed as the first pilot system employing individually driven cryo cavities, which should serve to realize a simultaneous acceleration of protons and deuterons in the KEK PS injector. A 400 MHz copper cavity, equivalent to each of the unit cavities composing the post-accelerator, passed a test operation at liquid nitrogen temperature with a 20 Hz-repetition 0.3 ms-width pulsed power up to the peak value 5 kW giving rise to the specified voltage. It will be subjected to further operation at lower temperature.

Morozumi, Yuichi

1997-05-01

306

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

307

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.

308

Novel Crab Cavity RF Design  

SciTech Connect

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

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

2011-03-01

309

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

310

Lithographic nanofabrication of optical cavities  

NASA Astrophysics Data System (ADS)

Lithographic control over nanostructures has recently evolved to an accuracy that permits the sub-wavelength manipulation of light within high refractive index semiconductors. We have used this lithographic control to fabricate two-dimensional photonic crystal cavities and micro-ring resonators. Here we will show the fabrication techniques utilized for the construction of High-Q nanocavities and, in particular, focus on the influence of present-day lithographic and etching procedures on the performance of the cavities. Applications of these optical cavities range from communications to chemical sensing and we will describe the effects of geometry on the different applications. We show the use of optical cavities for the miniaturization of optical spectroscopy systems with ultra-high spatial and spectral resolution.

DeRose, Guy A.; Loncar, Marko; Adams, Mark L.; Hochberg, Michael; Scherer, Axel

2005-01-01

311

Nose, Nasal Cavities & Paranasal Sinuses  

MedlinePLUS

... Citation Help Home » Cancer Registration & Surveillance Modules » Anatomy & Physiology » Respiratory System » Conducting Passages » Nose, Nasal Cavities & Paranasal Sinuses Cancer Registration & Surveillance Modules Anatomy & Physiology Intro to the Human Body Body Functions & Life ...

312

Enhanced diffusion welding  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

313

Counterion Diffusion in Ionomers  

NASA Astrophysics Data System (ADS)

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

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

2004-03-01

314

Sequential cavity use in a cottonwood bottomland  

USGS Publications Warehouse

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

Sedgwick, J. A.

1997-01-01

315

Polishing Difficult-To-Reach Cavities  

NASA Technical Reports Server (NTRS)

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

Malinzak, R. Michael; Booth, Gary N.

1990-01-01

316

Analysis of performance limitations for superconducting cavities  

Microsoft Academic Search

The performance of superconducting cavities in accelerators can be limited by several factors, such as: field emission, quenches, arcing, rf power; and the maximum gradient at which a cavity can operate will be determined by the lowest of these limitations for that particular cavity. The CEBAF accelerator operates with over 300 cavities and, for each of them, the authors have

J. R. Delayen; L. R. Doolittle; C. E. Reece

1998-01-01

317

Study of klystron cavity using MAFIA  

Microsoft Academic Search

An efficient method of determining the frequency and the characteristic impedance of the reentrant cavity for klystrons using MAFIA is presented in this paper. Two kinds of cavities are calculated. One is cylindrical cavity and the other is rectangular cavity. The results from MAFIA are compared with those from equivalent circuit model and those from cold test measurements. The error

Liang Youhuan; Liao Fujiang; Li Zepu

2004-01-01

318

Reactive diffusion in the roll bonded iron–aluminum system  

Microsoft Academic Search

The diffusion-controlled growth of iron aluminide (Fe2Al5) was studied on bulk Fe–Al solid state diffusion couples annealed for 10–90 min at 773–873 K. The layer growth kinetics was parabolic. The parabolic growth constants of the second kind for the exclusive growth of Fe2Al5 from the adjacent phases were calculated from the measurement on the Fe–Al diffusion couples. The rate constants

Vikas Jindal; V. C. Srivastava; Arpan Das; R. N. Ghosh

2006-01-01

319

TEM observations of crack tip: cavity interactions  

SciTech Connect

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

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

1981-01-01

320

Cavity-Modulation Autotuner For Hydrogen Maser  

NASA Technical Reports Server (NTRS)

Cavity-modulation tuning system maintains resonance of hydrogen-maser cavity automatically, stabilizing maser frequency, without introducing undesirable frequency modulation. System tunes maser cavity rapidly by modulating one of physical characteristics of cavity affecting resonant frequency. Frequency-controlling components of tuning system placed at maser cavity, within maser vacuum. Thermal environment well controlled, and device insensitive to driving signal. Features contribute to stability of maser frequency.

Dick, G. J.; Tucker, T. K.

1987-01-01

321

First-principles calculation of self-diffusion, arsenic diffusion, and surface segregation in silicon  

Microsoft Academic Search

Integrated circuit device densities have increased more than 2000 times since Gordon Moore's observation of exponential growth in 1965. Modern devices are thus sensitive to minute variations in diffusion, such as the transient-enhanced diffusivity resulting from ion implantation, concentration-dependent diffusivity of dopants due to changes in the Fermi level, and the effects of high stresses and stress gradients (resulting from

Scott A. Centoni

2003-01-01

322

Diffusion on Cu surfaces  

NASA Technical Reports Server (NTRS)

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

Karimi, Majid

1993-01-01

323

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

324

Cavity characteristics of selectively oxidized vertical-cavity lasers  

SciTech Connect

We show that a buried oxide layer forming a current aperture in an all epitaxial vertical-cavity surface emitting laser has a profound influence on the optical and electrical characteristics of the device. The lateral index variation formed around the oxide current aperture leads to a shift in the cavity resonance wavelength. The resonance wavelength under the oxide layer can thus be manipulated, independent of the as-grown cavity resonance, by adjusting the oxide layer thickness and its placement relative to the active region. In addition, the electrical confinement afforded by the oxide layer enables record low threshold current densities and threshold voltages in these lasers. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Choquette, K.D.; Lear, K.L.; Schneider, R.P. Jr.; Geib, K.M. [Photonics Research Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Photonics Research Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

1995-06-19

325

Cavity quantum electrodynamics with quantum dot - photonic crystal nanocavities  

NASA Astrophysics Data System (ADS)

High quality factor, small mode volume photonic crystal cavities and single emitter quantum dots are the topic of this dissertation. They are studied as both a combined system with InAs quantum dots grown in the center of a 2D GaAs photonic crystal slab nanocavity as well as individually. The individual studies are concerned with passive 1D silicon photonic crystal nanobeam cavities and deterministic, site-selectively grown arrays of InAs quantum dots. For the combined system, strong light matter coupling in a quantum dot photonic crystal slab nanocavity is discussed. Vacuum Rabi splitting is seen when the interaction strength exceeds the dissipative processes of the coupled system. In order to increase the probability of a spectral matching between cavity modes and quantum dot transitions, a technique for condensing an inert gas onto a sample is used. This can lead to a spectral tuning of up to 4 nm of the cavity mode with minimal change in the cavity quality factor while maintaining cryogenic temperatures down to 4 K. The effect of a large density of quantum dots within a quantum dot photonic crystal slab nanocavity is also addressed. Gain and absorption effects are found to occur, changing the cavity emission linewidth from that of its intrinsic value, as well as lasing with a low number of quantum dots and with high spontaneous emission coupling factors. Additionally, methods for improving the quality factor of GaAs photonic crystal cavities and better understanding different loss mechanisms are discussed. In the individual studies, the site-selective growth of InAs quantum dots on pre-structured GaAs wafers is shown as a promising method for the eventual deterministic fabrication of photonic crystal cavities to single quantum dots. An in-situ annealing step is used to reduce quantum dot density, helping ensure that dots are not grown in unwanted locations. Given silicon's potential for achieving higher quality factors than its GaAs counterpart, a study of 1D passive silicon photonic crystal nanobeam cavities is carried out. Transmission through a coupled microfiber is used to measure quality factors of the cavities and compared with that of a crossed polarized resonant scattering measurement.

Hendrickson, Joshua R.

326

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

327

The ESS spoke cavity cryomodules  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

328

The ESS elliptical cavity cryomodules  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

329

Non-axisymmetric collapse of cylindrical cavities  

NASA Astrophysics Data System (ADS)

Upon the impact of a circular disk on a water surface an expanding cylindrical cavity is created which collapses under the influence of the hydrostatic pressure. We experimentally observe small disturbances in the azimuthal direction that tend to grow towards the pinch-off. To quantitatively investigate the growth of specific mode-numbers, we use disks with a harmonic disturbance applied to their round shapes and study the collapse of the disturbed cavity using high-speed imaging. We performed experiments using disturbances up to mode number m=6, with varying strength from 1% to 25% of the radius of the undisturbed circular disk. For the smallest disturbances we compare the experimental results to a linear stability analysis, following Schmidt et al., Nat. Phys. 5, 343-346 (2009). Larger disturbances become non-linear in an early stage, showing a wealth of complex phenomena like secondary collapses and jets, during which the initial symmetry corresponding to the mode number m always remains preserved.

Peters, Ivo; Puente, Oscar R. Enriquez Paz Y.; Gekle, Stephan; Schmidt, Laura E.; van der Meer, Devaraj; Lohse, Detlef

2009-11-01

330

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

331

The Superconducting Cavity Stabilized Oscillator  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

332

Cavity ring-down ellipsometry  

NASA Astrophysics Data System (ADS)

We demonstrate the enhancement of ellipsometric measurements by multiple reflections of a polarized light pulse on a highly reflective target surface, using an optical cavity. The principle is demonstrated by measuring the adsorbed amount of a molecular vapor (fenchone) onto the ring-cavity mirrors. A phase shift sensitivity of about 10-2° in a single laser pulse is achieved in 1 ?s. Further improvements are discussed that should allow sensitivities of at least 10-4°, surpassing current commercial ellipsometers, but also surpassing their time resolution by several orders of magnitude, allowing the uses of sensitive ellipsometry to be expanded to include the study of fast surface phenomena with submicrosecond resolution.

Karaiskou, Anna; Papadakis, Vassilis; Loppinet, Benoit; Rakitzis, T. Peter

2009-09-01

333

Thermal-wave interferometry of gas-liquid applied to a thermal-wave resonator cavity technique  

NASA Astrophysics Data System (ADS)

We propose the potential use of thermal-wave interferometry in measuring thermal diffusivities of two media with a thermal-wave resonator cavity technique. In the derived expression for a two-layer configuration, during cavity length probing of the upper medium, the physical and thermal properties of the lower medium were reasonably assumed to be independent of cavity length; hence each of the two slopes of signal versus cavity length actually determines the thermal diffusivity of the corresponding medium. In order to check the validity of the proposed model, we measure the thermal diffusivity of air and glycerol. A good linear relation of the amplitude and the phase with respect to cavity length in the thermally thick region of both media was observed, and the thermal diffusivities of air and glycerol obtained were close to the literature values. We suggest the potential application of thermal-wave resonator cavity technique to measure the thermal properties of a single-layer fluid in a general thermal condition where the advantage is that the signal-to-noise ratio is normally high compared to the thermally thick case. This can be achieved possibly by coating the pyroelectric transducer with a thermally thick solid material prior to any measurements.

Azmi, B. Z.; Liaw, H. S.; Abbas, Z.

2005-07-01

334

Analog detection for cavity lifetime spectroscopy  

DOEpatents

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

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

2001-05-15

335

Analog detection for cavity lifetime spectroscopy  

DOEpatents

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

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

2003-01-01

336

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

337

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

PubMed Central

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

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

2014-01-01

338

FXR accelerator cavity impedance experiments.  

National Technical Information Service (NTIS)

One of the goals of the present Flash X-Ray (FXR) accelerator upgrade effort (1)(2) at Lawrence Livermore National Laboratory (LLNL) is to reduce the cavity transverse impedance, since it has been shown that beam stability is significantly affected by thi...

C. A. Avalle

1998-01-01

339

Facing rim cavities fluctuation modes  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

340

Improving cooling of cavity blackbodies  

NASA Astrophysics Data System (ADS)

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

Barrat, Catherine; Chauvel, Gildas

2013-10-01

341

"Grinding" cavities in polyurethane foam  

NASA Technical Reports Server (NTRS)

Grinding tool installed on conventional milling machine cuts precise cavities in foam blocks. Method is well suited for prototype or midsize production runs and can be adapted to computer control for mass production. Method saves time and materials compared to bonding or hot wire techniques.

Brower, J. R.; Davey, R. E.; Dixon, W. F.; Robb, P. H.; Zebus, P. P.

1980-01-01

342

Cavity Radar Cross Section Prediction  

Microsoft Academic Search

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

Adam Zdunek; Waldemar Rachowicz

2008-01-01

343

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

SciTech Connect

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

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

2005-07-06

344

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

PubMed Central

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

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

2013-01-01

345

A new method for simulating the late stages of island coarsening in thin film growth: The role of island diffusion and evaporation  

NASA Astrophysics Data System (ADS)

We have developed a method for simulating the evolution of an ensemble of one-atom-high islands from deposition and nucleation to coarsening. Using this method we have studied three regimes of coarsening; coarsening due to island coalescence, coarsening driven by evaporation, and the case in which both mechanisms act simultaneously. The parameters have been chosen to mimic coarsening of Ag on Ag(001); they are not meant to reproduce the experimental results for Ag quantitatively, but to provide simulations relevant to metal-on-metal homoepitaxy. We find that the scaling laws proposed by the mean-field theory for the time dependence of the number of islands and the island size distribution function work well in the limiting case when coarsening is dominated by island diffusion and coalescence. In the opposite limit, when coarsening is dominated by evaporation, the scaling predicted for the island size works well, but the island size distribution predicted by the mean-field theory is narrower than the one found in simulations. In the case when island migration and evaporation are both important, the evolution of the number of islands shows a crossover; at early times it scales as if coarsening takes place by island coalescence, and at later times it scales as if coarsening is dominated by evaporation. Regardless of the coarsening mechanism, most islands disappear by coalescence.

Mattsson, Thomas R.; Mills, Greg; Metiu, Horia

1999-06-01

346

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

Microsoft Academic Search

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

Heinrich J. Voelk; Peter L. Biermann

1988-01-01

347

Boron retarded self-interstitial diffusion in Czochralski growth of silicon crystals and its role in oxidation-induced stacking-fault ring dynamics  

NASA Astrophysics Data System (ADS)

The effect of boron doping on the position of the oxidation-induced stacking-fault ring (OSF ring) during Czochralski (CZ) crystal growth is described using a comprehensive model for point defect dynamics including the role of boron. The important interactions between boron atoms and intrinsic point defects are selected on the basis of tight-binding estimates for the energies of formation for boron-point defect structures. Intrinsic point defect properties used are taken from a parameterized model of point defect dynamics for predicting OSF-ring dynamics. Entropies of formation for boron-point defect species are obtained by fitting the predictions of the model to experimental data for OSF-ring dynamics. The model successfully predicts OSF-ring dynamics for a variety of doping and growth conditions. The effect of boron on the OSF ring is caused by the retardation of point defect recombination at temperatures near the melting point caused by dynamic storage of self-interstitials in complexes with boron.

Sinno, Talid; Susanto, Hendi; Brown, Robert A.; von Ammon, Wilfried; Dornberger, Erich

1999-09-01

348

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

349

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

350

On the Stability of Radiation Pressure Dominated Cavities in the Formation of Massive Stars  

NASA Astrophysics Data System (ADS)

Context: Once massive stars exert a radiation pressure onto their environment higher than gravitational attraction, they launch a radiation pressure driven outflow, which creates cleared polar cavities. Where as such cavities would shield further accretion onto the star from the direction of the bubble, it has been claimed that a radiative Rayleigh-Taylor instability would lead to the collapse of the outflow cavity. Aims: We investigate the stability of radiation pressure dominated cavities, focusing on its dependence on the radiation transport approach used in numerical simulations. Methods: We compare two different methods for stellar radiation feedback: gray Flux-Limited Diffusion (FLD) and frequency-dependent Ray-Tracing (RT). Both methods are implemented in our self-gravity radiation-hydrodynamics simulations for various initial density structures of the collapsing clouds. We also derive simple analytical models to support our findings. Results: Both methods lead to the launch of a radiation pressure dominated outflow cavity. But only FLD cases lead to prominent instability in the cavity shell. The RT cases do not show such instability; once the outflow started, it precedes continuously. The FLD cases display extended epochs of marginal Eddington equilibrium in the cavity shell, making them prone to the radiative Rayleigh-Taylor instability. In the RT cases, the radiation pressure exceeds gravity by 1-2 orders of magnitude. Then the radiative Rayleigh-Taylor instability is consequently suppressed. It is a fundamental property of the gray FLD method to neglect the stellar radiation temperature at the location of absorption and thus to underestimate opacity at the location of the cavity shell. Conclusions: Treating the stellar irradiation in the gray FLD approximation underestimates the radiative forces acting on the cavity shell. This can artificially lead to situations unstable to the radiative Rayleigh-Taylor instability. The proper treatment of direct stellar irradiation by massive stars is crucial for the stability of radiation pressure dominated cavities.

Kuiper, Rolf

2012-01-01

351

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

352

Toward Cavity QED on an atom chip  

NASA Astrophysics Data System (ADS)

We describe the construction and operation of microfabricated atom chips containing optical cavities suitable for cavity QED. The silicon or sapphire chips support microfabricated magnetic traps and guides for ultracold atoms, as well as Fabry- Perot optical cavities with axes perpendicular to the chips' surface. In the case of the sapphire chip, the cavities are half planar with the flat mirrors deposited directly on the surface of the chip, and curved macroscopic mirrors mounted above the chip. The silicon chip has micromachined holes through which the modes of externally mounted Fabry-Perot cavities pass. The cavities have small enough mode volume and high enough finesse to be useful as atom number detectors in a variety of on-chip experiments. Also this technology may be used in a number of cavity QED based quantum optics schemes, which would benefit from controllable magnetic loading of cold atoms into optical cavities.

Purdy, Thomas; Stamper-Kurn, Dan

2006-05-01

353

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

354

Experimental Cavity Pressure Distributions at Supersonic Speeds.  

National Technical Information Service (NTIS)

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

R. L. Stallings F. J. Wilcox

1987-01-01

355

Cancer of the Oral Cavity and Pharynx  

MedlinePLUS

... third party. HPF: SEER Stat Fact Sheets: Oral Cavity and Pharynx Cancer Expand All Collapse All Mortality ... Years Or More after Being Diagnosed with Oral Cavity and Pharynx Cancer? Relative survival statistics compare the ...

356

Stages of Lip and Oral Cavity Cancer  

MedlinePLUS

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

357

Optical modeling of certical-cavity surface-emitting lasers  

SciTech Connect

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

Hadley, G.R.

1996-12-31

358

A Diffusing Runner for Gravity Casting  

Microsoft Academic Search

In gravity casting, the quality of an aluminum alloy casting relies on, among other things, the design of the runner system\\u000a in which the ingate velocity into the mold cavity should be controlled to stay under a critical velocity (close to 0.5 m\\/s).\\u000a In this study, a diffuser was proposed to reduce the velocity of liquid metal to below this critical

Fu-Yuan Hsu; Huey-Jiuan Lin

2009-01-01

359

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

360

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

361

Coupled-cavity drift-tube linac  

Microsoft Academic Search

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the .pi.-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is .beta..lambda., where .lambda. is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by

Billen; James H

1996-01-01

362

Coupled-cavity drift-tube linac  

Microsoft Academic Search

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the Ï-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is βλ, where λ is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by

Billen

1996-01-01

363

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

364

Electron paramagnetic resonance instrument with superconductive cavity  

Microsoft Academic Search

The EPR instrument includes an X band klystron used to generate microwave power that is transmitted to a superconductive waveguide cavity resonator. The cavity is placed between the pole pieces of a large d-c magnet and small a-c magnetic coils energized by a modulation signal source. A microwave crystal detector detects RF energy emitted from the cavity. The detector output

Jasper

1989-01-01

365

Discrete wavelength-locked external cavity laser  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

366

Cavity Predictor: Is Your Child at Risk?  

MedlinePLUS

The Cavity Predictor: Is Your Child at Risk? 1. Has your child ever had a cavity? No - Low risk Yes - Moderate to high risk ... is under the age of 5, how many cavities have you or his or her caregiver had ...

367

An Automatically Tunable Cavity Resonator System  

Microsoft Academic Search

A tunable cavity resonator is described that uses a feedback control system to alter its resonant characteristics in response to changes in its environment, without changing the physical dimensions of the resonator. Tuning wires inserted into the cavity are connected or disconnected to the cavity wall under the control of a binary algorithm that searches for desirable operating states from

Raoul O. Ouedraogo; Edward J. Rothwell; Shih-Yuan Chen; Brian J. Greetis

2010-01-01

368

Performance of Single Crystal Niobium Cavities  

Microsoft Academic Search

We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other

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

2008-01-01

369

Microwave cavities for vapor cell frequency standards  

Microsoft Academic Search

In this paper, we report an analysis of the design criteria of microwave cavities for vapor cell frequency standards. Two main geometries exploited in those devices are considered: the cylindrical cavity, used, for example, in the coherent population trapping maser and in the pulsed optically pumped (POP) clock, and the spherical cavity used in the isotropically laser cooled clock. The

Aldo Godone; Salvatore Micalizio; Filippo Levi; Claudio Calosso

2011-01-01

370

Diffusion Processes in Metals.  

National Technical Information Service (NTIS)

This book consists of a collection of papers dealing with diffusion welding of metals, effect of irradiation on diffusion and diffusion-controlled processes, migration of particles in the stress-field of dislocation loops, diffusion in liquid metals, grai...

1969-01-01

371

Calculations of HOMs and coupled bunch instabilities due to the RHIC rf cavities  

SciTech Connect

The cavities for the two RHIC rf systems have been defined, a 26.7 MHz cavity developed by the RHIC rf group and the well documented CERN SPS 200 MHz cavity tuned to 196.1 MHz for operation in RHIC. Calculations of the shunt impedances and Q`s of the higher order modes (HOMs) are summarized along with beadpull measurements of R/Q of selected modes. Estimates of coupled bunch instability growth rates are calculated with both analytical techniques and using the code ZAP and used to make projections of mode damping requirements.

Rose, J.

1994-09-01

372

Edge and vertical cavity surface emitting InAs quantum dot lasers  

Microsoft Academic Search

Quantum dot (QD) edge emitting and vertical cavity lasers are realized using a self-organized growth approach. Threshold current densities at room temperature (RT) of about 60Acm?2 for edge emitting and 170Acm?2 for vertical cavity lasers are measured. High internal (>96%) and differential (70%) efficiencies are obtained for InGaAs–AlGaAs lasers based on vertically coupled QDs and RT 1W continuous wave operation

D. Bimberg; N. N Ledentsov; M. Grundmann; F. Heinrichsdorff; V. M Ustinov; P. S Kop'ev; Zh. I Alferov; J. A Lott

1998-01-01

373

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

SciTech Connect

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

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

1996-03-01

374

Cavity ring-down ellipsometry.  

PubMed

We demonstrate the enhancement of ellipsometric measurements by multiple reflections of a polarized light pulse on a highly reflective target surface, using an optical cavity. The principle is demonstrated by measuring the adsorbed amount of a molecular vapor (fenchone) onto the ring-cavity mirrors. A phase shift sensitivity of about 10(-2) degrees in a single laser pulse is achieved in 1 micros. Further improvements are discussed that should allow sensitivities of at least 10(-4) degrees , surpassing current commercial ellipsometers, but also surpassing their time resolution by several orders of magnitude, allowing the uses of sensitive ellipsometry to be expanded to include the study of fast surface phenomena with submicrosecond resolution. PMID:19791842

Karaiskou, Anna; Papadakis, Vassilis; Loppinet, Benoit; Rakitzis, T Peter

2009-09-28

375

YIG tuners for RF cavities  

SciTech Connect

Tuning of radio frequency (RF) accelerator cavities in electron storage rings is needed to maintain accelerating gap voltage under varying beam loading conditions. A new type of ferrite tuner based on stripline configuration has been tested at the National Synchrotron Light Source (NSLS). The tuner is basically a short-circuited ferrite-loaded transmission line which is inductively coupled to the RF cavity to be tuned. The use of substituted yttrium iron garnet (YIG) allows for custom tailoring the saturation magnetization to the specific application and thus minimizing the bias field requirement. The design goal for the tuner was to achieve a tuning range of 50 KHz. The authors were able to demonstrate linear tunability of 78 KHz, exceeding the goals set for the tuner. Results of testing the YIG tuner are presented.

Hanna, S.M.; Keane, J. (Brookhaven National Lab., Upton, NY (United States). National Synchrotron Light Source); Pivit, E. (ANT Nachrichtentenchnik GmbH, Backnang (Germany))

1992-09-01

376

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

377

Stent hypersensitivity and infection in sinus cavities  

PubMed Central

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

Soufras, George D.; Hahalis, George

2013-01-01

378

Stent hypersensitivity and infection in sinus cavities.  

PubMed

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

Kounis, Nicholas G; Soufras, George D; Hahalis, George

2013-01-01

379

Controlled directional scattering cavity for tubular absorbers  

DOEpatents

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

Winston, Roland (Chicago, IL)

1982-01-01

380

Acoustic cavity technology for high performance injectors  

NASA Technical Reports Server (NTRS)

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

1976-01-01

381

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

382

Lithographic nanofabrication of optical cavities  

Microsoft Academic Search

Lithographic control over nanostructures has recently evolved to an accuracy that permits the sub-wavelength manipulation of light within high refractive index semiconductors. We have used this lithographic control to fabricate two-dimensional photonic crystal cavities and micro-ring resonators. Here we will show the fabrication techniques utilized for the construction of High-Q nanocavities and, in particular, focus on the influence of present-day

Guy A. DeRose; Marko Loncar; Mark L. Adams; Michael Hochberg; Axel Scherer

2005-01-01

383

Grinding Inside A Toroidal Cavity  

NASA Technical Reports Server (NTRS)

Weld lines ground smooth within about 0.001 in. Grinding tool for smoothing longitudinal weld lines inside toroidal cavity includes curved tunnel jig to guide grinding "mouse" along weld line. Curvature of tunnel jig matched to shape of toroid so grinding ball in mouse follows circular arc of correct radius as mouse is pushed along tunnel. Tool enables precise control of grindout shape, yet easy to use.

Mayer, Walter; Adams, James F.; Burley, Richard K.

1987-01-01

384

External cavity coherent transmitter modules  

NASA Astrophysics Data System (ADS)

This report covers work done with a Fabry-Perot semiconductor laser based external cavity structure, for use with coherent fiber optical communications systems. A novel structure was developed which uses a single-mode fiber as part of the external cavity, together with a graded-index rod lens and a diffraction grating end reflector. The advantages of choosing this structure are highlighted, the principal being that it can be used with any modulation format, at any bit rate and also as the transmitter laser or the local oscillator laser. The latter has to have wide tunability so that the coherent receiver can select closely packed optical channels, and the structure selected is the only one that offers very wide turnability of over 100nm or 12,000 GHz. Various measurements done with this structure are included in this report. Extensive theoretical work an spectral linewidth and tunability is also reported and detailed comparison of the above structure is made with those based on distributed feedback lasers and also having external cavities.

Sunak, Harish

1990-11-01

385

Hepatoid carcinoma of the pancreas penetrating into the gastric cavity: a case report and literature review.  

PubMed

A 79-year-old Japanese woman was admitted to our hospital for treatment of a pancreatic tumor measuring approximately 7 × 5 cm. The tumor had invaded the left adrenal gland and gastric wall and had penetrated into the gastric cavity. Surgical resection was performed. The tumor was composed of a brown to whitish solid area and a zone of hemorrhage, necrosis, and cystic degeneration resembling the gross features of solid pseudopapillary tumor (SPT). Histologically, the tumor showed a heterogeneous growth pattern with a combination of seat-like, trabecular, papillary and hemorrhagic-necrotic areas in various proportions. The differential diagnoses first considered were acinar cell carcinoma, neuroendocrine carcinoma and SPT with malignant transformation. Immunohistochemistry showed tumor cells were negative for pancreatic exocrine enzymes and endocrine markers. Tumor cells diffusely expressed cytokeratin 19, alpha-fetoprotein, carcinoembryonic antigen and glypican-3, but lacked vimentin or ?-catenin expression. Small proportions of tumor cells expressed hepatocyte paraffin-1. Although typical morphological features of well-differentiated hepatocellular carcinoma (HCC) were not distinctly apparent, the tumor morphology partly resembled poorly differentiated HCC. Given these findings and considerations, the tumor was finally diagnosed as poorly differentiated hepatoid carcinoma of the pancreas. PMID:22726068

Kai, Keita; Nakamura, Jun; Ide, Takao; Masuda, Masanori; Kitahara, Kenji; Miyoshi, Atsushi; Noshiro, Hirokazu; Tokunaga, Osamu

2012-07-01

386

Coronal Cavity Catalog from SDO Observations  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

387

Plasmonic Coupled Cavities on Moire Surfaces  

NASA Astrophysics Data System (ADS)

We investigate surface plasmon polariton (SPP) coupled cavity modes on Moire surfaces. An experimental study has been made of the propagation of SPPs on a thin silver surface that is textured with Moire surface pattern using interference lithography. The Moire surface contains periodic array of one dimensional cavities. The distance between the cavities can be controlled by changing the periodicities of Moire surface. When the SPP cavity separation is sufficiently small, we show splitting of strongly coupled plasmonic cavity modes through numerical simulations. Conversely, when the SPP cavity separation is sufficiently large, SPP cavity modes are found to be localized and do not show splitting of SPP cavity modes . This splitting of SPP cavity modes are well explained with a tight binding model that has been succesfully applied in photonic coupled cavities. Reflection measurements and numerical simulation of a large number of adjacent SPP cavities have shown a coupled resonator optical waveguide (CROW) type plasmonic waveguide band formation within the band gap region of unperturbed uniform grating.

Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla

2010-03-01

388

Control of Cavity Resonance Using Oscillatory Blowing  

NASA Technical Reports Server (NTRS)

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

Scarfe, Alison Lamp; Chokani, Ndaona

2000-01-01

389

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

390

Coupled resonator vertical-cavity laser diode  

SciTech Connect

We report the operation of an electrically injected monolithic coupled resonator vertical-cavity laser which consists of an active cavity containing In{sub x}Ga{sub 1{minus}x}As quantum wells optically coupled to a passive GaAs cavity. This device demonstrates modulation characteristics arising from dynamic changes in the coupling between the active and passive cavities. A composite mode theory is used to model the output modulation of the coupled resonator vertical-cavity laser. It is shown that the laser intensity can be modulated by either forward or reverse biasing the passive cavity. Under forward biasing, the modulation is due to carrier induced changes in the refractive index, while for reverse bias operation the modulation is caused by field dependent cavity enhanced absorption. {copyright} {ital 1999 American Institute of Physics.}

Fischer, A.J.; Choquette, K.D.; Chow, W.W.; Hou, H.Q.; Geib, K.M. [Center for Compound Semiconductor Science and Technology, Sandia National Labs, Albuquerque, New Mexico 87185 (United States)] [Center for Compound Semiconductor Science and Technology, Sandia National Labs, Albuquerque, New Mexico 87185 (United States)

1999-11-01

391

Novel Geometries for the LHC Crab Cavity  

SciTech Connect

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

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

2010-05-01

392

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

393

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

394

Performance Capability of Single-Cavity Vortex Gaseous Nuclear Rockets  

NASA Technical Reports Server (NTRS)

An analysis was made to determine the maximum powerplant thrust-to-weight ratio possible with a single-cavity vortex gaseous reactor in which all the hydrogen propellant must diffuse through a fuel-rich region. An assumed radial temperature profile was used to represent conduction, convection, and radiation heat-transfer effects. The effect of hydrogen property changes due to dissociation and ionization was taken into account in a hydrodynamic computer program. It is shown that, even for extremely optimistic assumptions of reactor criticality and operating conditions, such a system is limited to reactor thrust-to-weight ratios of about 1.2 x 10(exp -3) for laminar flow. For turbulent flow, the maximum thrust-to-weight ratio is less than 10(exp -3). These low thrusts result from the fact that the hydrogen flow rate is limited by the diffusion process. The performance of a gas-core system with a specific impulse of 3000 seconds and a powerplant thrust-to-weight ratio of 10(exp -2) is shown to be equivalent to that of a 1000-second advanced solid-core system. It is therefore concluded that a single-cavity vortex gaseous reactor in which all the hydrogen must diffuse through the nuclear fuel is a low-thrust device and offers no improvement over a solid-core nuclear-rocket engine. To achieve higher thrust, additional hydrogen flow must be introduced in such a manner that it will by-pass the nuclear fuel. Obviously, such flow must be heated by thermal radiation. An illustrative model of a single-cavity vortex system employing supplementary flow of hydrogen through the core region is briefly examined. Such a system appears capable of thrust-to-weight ratios of approximately 1 to 10. For a high-impulse engine, this capability would be a considerable improvement over solid-core performance. Limits imposed by thermal radiation heat transfer to cavity walls are acknowledged but not evaluated. Alternate vortex concepts that employ many parallel vortices to achieve higher hydrogen flow rates offer the possibility of sufficiently high thrust-to-weight ratios, if they are not limited by short thermal-radiation path lengths.

Ragsdale, Robert G.

1963-01-01

395

Selective advantage of diffusing faster.  

PubMed

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

Pigolotti, Simone; Benzi, Roberto

2014-05-01

396

Selective Advantage of Diffusing Faster  

NASA Astrophysics Data System (ADS)

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

Pigolotti, Simone; Benzi, Roberto

2014-05-01

397

Temperature Structure of a Coronal Cavity  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

398

Temperature Structure of a Coronal Cavity  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

399

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

400

Numerical simulation of double-diffusive mixed convective flow in rectangular enclosure with insulated moving lid  

Microsoft Academic Search

The present study is concerned with the mixed convection in a rectangular lid-driven cavity under the combined buoyancy effects of thermal and mass diffusion. Double-diffusive convective flow in a rectangular enclosure with moving upper surface is studied numerically. Both upper and lower surfaces are being insulated and impermeable. Constant different temperatures and concentration are imposed along the vertical walls of

Mohamed A. Teamah; Wael M. El-Maghlany

2010-01-01

401

Unstable resonator cavity semiconductor lasers  

NASA Astrophysics Data System (ADS)

GaAs heterostructure lasers with unstable resonator cavities were demonstrated for the first time with both curved mirrors fabricated by etching. Typical output powers of 0.35 W were observed in a stable, highly coherent lateral mode. The laser operated stably in a single longitudinal mode over a large range of injection currents. The external quantum efficiency was 70 percent of that of a similar laser with both mirror facets cleaved implying good output coupling of the energy from the entire region.

Salzman, J.; Lang, R.; Mittelstein, M.; Yariv, A.; Venkatesan, T.

1985-02-01

402

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

NASA Technical Reports Server (NTRS)

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

Ragsdale, Robert G.; Hyland, Robert E.

1961-01-01

403

Cavity nucleation in Al 5083 alloys  

SciTech Connect

In this paper the authors address the controversial issue of nucleation of cavities in Al 5083 alloys. They focus on the origin of cavities during the manufacture of these alloys into SPF (superplastic forming) sheet form. Experimental observations on the pre-existing cavities in this alloy are made using optical and electron microscopy. The effects of rolling direction and state of stress during superplastic deformations on the formation of cavities are also discussed. Numerical simulations of the sheet manufacturing process are carried out to understand the effect of hard phase/matrix, mechanical properties and interfacial strength on the origin of cavities. Based on the numerical results, a simplified model relating the process, material parameters and the cavity nucleation is presented.

Chandra, N.; Chen, Z.

2000-07-01

404

Coupled-cavity drift-tube linac  

DOEpatents

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the .pi.-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is .beta..lambda., where .lambda. is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a .pi./2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range.

Billen, James H. (Los Alamos, NM)

1996-01-01

405

Coupled-cavity drift-tube linac  

DOEpatents

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the {pi}-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is {beta}{lambda}, where {lambda} is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a {pi}/2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range. 5 figs.

Billen, J.H.

1996-11-26

406

Mounting system for optical frequency reference cavities  

NASA Technical Reports Server (NTRS)

A technique for reducing the vibration sensitivity of laser-stabilizing optical reference cavities is based upon an improved design and mounting method for the cavity, wherein the cavity is mounted vertically. It is suspended at one plane, around the spacer cylinder, equidistant from the mirror ends of the cavity. The suspension element is a collar of an extremely low thermal expansion coefficient material, which surrounds the spacer cylinder and contacts it uniformly. Once the collar has been properly located, it is cemented in place so that the spacer cylinder is uniformly supported and does not have to be squeezed at all. The collar also includes a number of cavities partially bored into its lower flat surface, around the axial bore. These cavities are support points, into which mounting base pins will be inserted. Hence the collar is supported at a minimum of three points.

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

2008-01-01

407

Performance of Single Crystal Niobium Cavities  

SciTech Connect

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

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

2008-07-01

408

Cavity-Dumped Communication Laser Design  

NASA Technical Reports Server (NTRS)

Cavity-dumped lasers have significant advantages over more conventional Q-switched lasers for high-rate operation with pulse position modulation communications, including the ability to emit laser pulses at 1- to 10-megahertz rates, with pulse widths of 0.5 to 5 nanoseconds. A major advantage of cavity dumping is the potential to vary the cavity output percentage from pulse to pulse, maintaining the remainder of the energy in reserve for the next pulse. This article presents the results of a simplified cavity-dumped laser model, establishing the requirements for cavity efficiency and projecting the ultimate laser efficiency attainable in normal operation. In addition, a method of reducing or eliminating laser dead time is suggested that could significantly enhance communication capacity. The design of a laboratory demonstration laser is presented with estimates of required cavity efficiency and demonstration potential.

Roberts, W. T.

2003-01-01

409

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

USGS Publications Warehouse

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

Kile, D. E.

2005-01-01

410

Natural cavities used by wood ducks in north-central Minnesota  

USGS Publications Warehouse

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

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

1978-01-01

411

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

SciTech Connect

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

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

1984-01-01

412

Cavity QED-based quantum walk  

SciTech Connect

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

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

2004-09-01

413

Compact Superconducting Crabbing and Deflecting Cavities  

SciTech Connect

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

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

2012-09-01

414

Resonant-cavity antenna for plasma heating  

DOEpatents

Disclosed is a resonant coil cavity wave launcher for energizing a plasma immersed in a magnetic field. Energization includes launching fast Alfven waves to excite ion cyclotron frequency resonances in the plasma. The cavity includes inductive and capacitive reactive members spaced no further than one-quarter wavelength from a first wall confinement chamber of the plasma. The cavity wave launcher is energized by connection to a waveguide or transmission line carrying forward power from a remote radio frequency energy source.

Perkins, Jr., Francis W. (Princeton, NJ); Chiu, Shiu-Chu (San Diego, CA); Parks, Paul (San Diego, CA); Rawls, John M. (Del Mar, CA)

1987-01-01

415

Soft X-ray laser cavities  

Microsoft Academic Search

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

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

1986-01-01

416

Soft x-ray laser cavities  

SciTech Connect

We report progress in the development of multilayer components for use in multiple pass soft x-ray laser cavities operating in the 100A to 300A spectral range. Our work includes fabrication and characterization of multilayer components; simple resonant cavity design; damage threshold assessment for multilayers in the x-ray laser environment; and multipass cavity experiments for efficiency enhancement and transverse mode selection. 14 refs., 9 figs.

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

1986-07-08

417

General recipe for designing photonic crystal cavities  

Microsoft Academic Search

We describe a general recipe for designing high-quality factor (Q) photonic crystal cavities with small mode volumes. We first derive a simple expression for out-of-plane losses in terms of the k-space distribution of the cavity mode. Using this, we select a field that will result in a high Q. We then derive an analytical relation between the cavity field and

Dirk Englund; Ilya Fushman; Jelena Vuckovic

2005-01-01

418

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

PubMed Central

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

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

2014-01-01

419

Fractional diffusion models of anomalous diffusion  

NASA Astrophysics Data System (ADS)

Perturbative transport experiments, and numerical simulations have provided evidence of non-Gaussian, anomalous diffusive transport in magnetically confined plasmas. These results are incompatible with the standard diffusive, local transport paradigm, and there is the need to develop alternative models. Here we explore the idea of constructing non-Gaussian diffusion models using fractional diffusion operators. In particular, we study the role of non-Gaussian diffusion in the propagation of fronts in the L-H transition, and show that fractional diffusion leads to the exponential acceleration of the front and the algebraic decay of the front's tail [1]. We also present a fractional in space and time diffusion model describing the non-Gaussian diffusion of test particles in pressure driven plasma turbulence. [1] D. del-Castillo-Negrete, B.A. Carreras, and V.E. Lynch, Phys Rev Lett, 91, 018302-1, (2003).

del-Castillo-Negrete, Diego; Carreras, B. A.; Lynch, V. E.

2003-10-01

420

Breakthrough: Record-Setting Cavity  

ScienceCinema

Gianluigi "Gigi" Ciovati, a superconducting radiofrequency scientist, discusses how scientists at the U.S. Department of Energy's Jefferson Lab in Newport News, VA, used ARRA funds to fabricate a niobium cavity for superconducting radiofrequency accelerators that has set a world record for energy efficiency. Jefferson Lab's scientists developed a new, super-hot treatment process that could soon make it possible to produce cavities more quickly and at less cost, benefitting research and healthcare around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.

Ciovati, Gianluigi

2014-05-21

421

Tunable Fabry-Perot cavities  

NASA Astrophysics Data System (ADS)

The construction of self supporting or suspended structures is one of the fundamental challenges of MEMS, with many technologies existing for the fabrication of such structures, such as bulk micromachining and surface machining. Generally surface micromachining techniques rely on the high temperature deposition process such as LPCVD, which produce high quality films. Process technologies exist for the deposition of material at substantially reduced temperatures, in particular PECVD that can deposit films at temperatures <300 degree(s)C. Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon nitride has not been used extensively in MEMS structures due to the material limitations created via the deposition technique, primarily controllability of the intrinsic stress and etch selectivity of the deposited film. We show here that PECVD silicon nitride can be used successfully in MEMS structures, and that the intrinsic stress is controllable through variations in the PECVD deposition parameters. A MEMS based Fabry-Perot cavity was fabricated using PECVD silicon nitride as the membrane layer with ZnS as the sacrificial material. Devices with an initial 1-micron cavity length typically provide a displacement of 320 nm across a 300 micrometers membrane span for an applied bias of 2.4 V.

Winchester, Kevin J.; Spaargaren, Sue M.; Dell, John M.

2000-10-01

422

Breakthrough: Record-Setting Cavity  

SciTech Connect

Gianluigi "Gigi" Ciovati, a superconducting radiofrequency scientist, discusses how scientists at the U.S. Department of Energy's Jefferson Lab in Newport News, VA, used ARRA funds to fabricate a niobium cavity for superconducting radiofrequency accelerators that has set a world record for energy efficiency. Jefferson Lab's scientists developed a new, super-hot treatment process that could soon make it possible to produce cavities more quickly and at less cost, benefitting research and healthcare around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.

Ciovati, Gianluigi

2012-03-01

423

Cavity cooling of a microlever.  

PubMed

The prospect of realizing entangled quantum states between macroscopic objects and photons has recently stimulated interest in new laser-cooling schemes. For example, laser-cooling of the vibrational modes of a mirror can be achieved by subjecting it to a radiation or photothermal pressure, actively controlled through a servo loop adjusted to oppose its brownian thermal motion within a preset frequency window. In contrast, atoms can be laser-cooled passively without such active feedback, because their random motion is intrinsically damped through their interaction with radiation. Here we report direct experimental evidence for passive (or intrinsic) optical cooling of a micromechanical resonator. We exploit cavity-induced photothermal pressure to quench the brownian vibrational fluctuations of a gold-coated silicon microlever from room temperature down to an effective temperature of 18 K. Extending this method to optical-cavity-induced radiation pressure might enable the quantum limit to be attained, opening the way for experimental investigations of macroscopic quantum superposition states involving numbers of atoms of the order of 10(14). PMID:15616555

Metzger, Constanze Höhberger; Karrai, Khaled

2004-12-23

424

Silicon Integrated Cavity Optomechanical Transducer  

NASA Astrophysics Data System (ADS)

Cavity optomechanics enables measurements of mechanical motion at the fundamental limits of precision imposed by quantum mechanics. However, the need to align and couple devices to off-chip optical components hinders development, miniaturization and broader application of ultrahigh sensitivity chip-scale optomechanical transducers. Here we demonstrate a fully integrated and optical fiber pigtailed optomechanical transducer with a high Q silicon micro-disk cavity near-field coupled to a nanoscale cantilever. We detect the motion of the cantilever by measuring the resonant frequency shift of the whispering gallery mode of the micro-disk. The sensitivity near the standard quantum limit can be reached with sub-uW optical power. Our on-chip approach combines compactness and stability with great design flexibility: the geometry of the micro-disk and cantilever can be tailored to optimize the mechanical/optical Q factors and tune the mechanical frequency over two orders of magnitudes. Electrical transduction in addition to optical transduction was also demonstrated and both can be used to effectively cool the cantilever. Moreover, cantilevers with sharp tips overhanging the chip edge were fabricated to potentially allow the mechanical cantilever to be coupled to a wide range of off-chip systems, such as spins, DNA, nanostructures and atoms on clean surfaces.

Zou, Jie; Miao, Houxun; Michels, Thomas; Liu, Yuxiang; Srinivasan, Kartik; Aksyuk, Vladimir

2013-03-01

425

Fastrac Rocket Engine Combustion Chamber Acoustic Cavities  

NASA Technical Reports Server (NTRS)

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

Christensen, Eric; Nesman, Tom

1998-01-01

426

Cavity-QED-based quantum phase gate  

SciTech Connect

We describe a quantum phase gate in which the two qubits are represented by the photons in the two modes of the cavity field. The gate is implemented by passing a three-level atom in a cascade configuration through the cavity. The upper levels of the atom are resonant with one of the cavity modes whereas the lower levels are appropriately detuned from the other mode of the cavity. A {pi} phase shift is introduced when there is one photon each in the two modes and the atom is initially in the ground state. We also discuss the one-