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1

Charge trapping mechanisms and microdosimetric processes in lithium fluoride  

NASA Astrophysics Data System (ADS)

We present a review of the charge trapping and recombination mechanisms in LiF thermoluminescence (TL) dosimeters and discuss several dosimetric properties of this material in the light of these processes. The complex TL glow-curve from LiF doped with Mg, Ti and OH impurities consists of several individual peaks which emit in the region of 420-460 nm, depending on the glow peak temperature. The kinetics of the process appear to be first-order. From an accumulation of experimental data from a variety of sources (dielectric loss, ionic thermocurrents, ionic conductivity, photoluminescence, X-ray-induced luminescence, optical absorption, electron spin resonance, and others) it is inferred that the TL emission near 200°C is the result of electron-hole recombination at defect complexes consisting of Mg trimers and TiOH n centers. The spatial localization of the Mg defects and the Ti defects is seen to be of fundamental importance in describing certain aspects of the dose response function of this material and the stability of the TL signal. Coupled with this, however, the microscopic processes of energy deposition, in which regions of high ionization density are formed inside the irradiated sample, are seen to provide the essential framework around which it is possible to establish a model to describe all the major features of the dose response function in LiF:Mg, Ti, OH for a variety of irradiation types.

McKeever, S. W. S.; Horowitz, Y. S.

2

Trapped Atomic Ions and Quantum Information Processing  

SciTech Connect

The basic requirements for quantum computing and quantum simulation (single- and multi-qubit gates, long memory times, etc.) have been demonstrated in separate experiments on trapped ions. Construction of a large-scale information processor will require synthesis of these elements and implementation of high-fidelity operations on a very large number of qubits. This is still well in the future. NIST and other groups are addressing part of the scaling issue by trying to fabricate multi-zone arrays of traps that would allow highly-parallel and scalable processing. In the near term, some simple quantum processing protocols are being used to aid in quantum metrology, such as in atomic clocks. As the number of qubits increases, Schroedinger's cat paradox and the measurement problem in quantum mechanics become more apparent; with luck, trapped ion systems might be able to shed light on these fundamental issues.

Wineland, D. J.; Leibfried, D.; Bergquist, J. C.; Blakestad, R. B.; Bollinger, J. J.; Britton, J.; Chiaverini, J.; Epstein, R. J.; Hume, D. B.; Itano, W. M.; Jost, J. D.; Koelemeij, J. C. J.; Langer, C.; Ozeri, R.; Reichle, R.; Rosenband, T.; Schaetz, T.; Schmidt, P. O.; Seidelin, S.; Shiga, N. [Time and Frequency Division, NIST, Boulder, CO (United States)] (and others)

2006-11-07

3

Trapping for Newtonian Diffusion Processes.  

National Technical Information Service (NTIS)

A mechanism for the formation of impenetrable barriers for Newtonian diffusion processes is considered. A mean stochastic acceleration for diffusion processes is defined. The Newtonian law in the mean acts as a constraint and enables probability distribut...

P. Blanchard

1984-01-01

4

Kinetics and mechanism of Dionaea muscipula trap closing.  

PubMed

The Venus flytrap (Dionaea muscipula) possesses an active trapping mechanism to capture insects with one of the most rapid movements in the plant kingdom, as described by Darwin. This article presents a detailed experimental investigation of trap closure by mechanical and electrical stimuli and the mechanism of this process. Trap closure consists of three distinctive phases: a silent phase with no observable movement; an accelerated movement of the lobes; and the relaxation of the lobes in their closed state, resulting in a new equilibrium. Uncouplers and blockers of membrane channels were used to investigate the mechanisms of different phases of closing. Uncouplers increased trap closure delay and significantly decreased the speed of trap closure. Ion channel blockers and aquaporin inhibitors increased time of closing. Transmission of a single electrical charge between a lobe and the midrib causes closure of the trap and induces an electrical signal propagating between both lobes and midrib. The Venus flytrap can accumulate small subthreshold charges, and when the threshold value is reached, the trap closes. Repeated application of smaller charges demonstrates the summation of stimuli. The cumulative character of electrical stimuli points to the existence of electrical memory in the Venus flytrap. The observed fast movement can be explained by the hydroelastic curvature model without invoking buckling instability. The new hydroelastic curvature mechanism provides an accurate description of the authors' experimental data. PMID:18065564

Volkov, Alexander G; Adesina, Tejumade; Markin, Vladislav S; Jovanov, Emil

2008-02-01

5

Mechanical Performance of Rat, Mouse and Mole Spring Traps, and Possible Implications for Welfare Performance  

PubMed Central

Lethal spring traps are widely used for killing small mammals in the UK. Many require government approval, based primarily on humaneness. However, mole traps and break-back traps for rats and mice are exempt; those available vary widely in price and apparent quality. The EU is considering implementing a Trapping Directive that would alter UK legislation, and a recent report advised the EU that trapping legislation should cover all trapped species and encourage improvement of traps. Mechanical trap performance is often used as an indicator of welfare impact. We examined the mechanical evidence for scope to improve the welfare standards of rat, mouse and mole spring traps. We measured mechanical performance among a range of rat, mouse and mole traps. Impact momentum values varied 6-8 fold, and clamping force values 4-5.5 fold, among traps for killing each species. There was considerable overlap in the performance of rat and mouse traps. Trap-opening angle and spring type were related to impact momentum and clamping force in traps for both species. There was no relationship between price and mechanical performance in traps for any species, except talpa mole traps. We are unable to judge the direct welfare impact of the traps tested, but rather the potential welfare threat associated with their exemption from approval. The wide variation in mechanical performance in traps for each species, overlap in performance between rat and mouse traps and increasing availability of weaker plastic rodent traps indicate considerable scope for improving the humaneness of spring traps for rats, mice and moles. We conclude that all such traps should be subject to the UK approval process. New welfare categories might improve trap standards further. Our results could also help improve rodent trap design and assist consumers in selecting more powerful traps. Many thousands of rats, mice and moles might benefit.

Baker, Sandra E.; Ellwood, Stephen A.; Tagarielli, Vito L.; Macdonald, David W.

2012-01-01

6

Eliminating Impurity Traps in the Silane Process  

NASA Technical Reports Server (NTRS)

Redistribution reaction section of silane process progressively separates heavier parts of chlorosilane feedstock until light silane product is available for pyrolysis. Small amount of liquid containing impurities is withdrawn from processing stages in which trapping occurs and passed to earlier processing stage in which impurities tend to be removed via chemical reactions.

Coleman, L. M.

1982-01-01

7

CO2 Capillary-Trapping Processes in Deep Saline Aquifers  

NASA Astrophysics Data System (ADS)

The idea of reducing the Earth's greenhouse effect by sequestration of CO2 into the Earth's crust has been discussed and evaluated for more than two decades. Deep saline aquifers are the primary candidate formations for realization of this idea. Evaluation of reservoir capacity and the risk of CO2 leakage require a detailed modeling of the migration and distribution of CO2 in the subsurface structure. There is a finite risk that structural (or hydrodynamic) trapping by caprock may be compromised (e.g. by improperly abandoned wells, stratigraphic discontinuities, faults, etc.). Therefore, other trapping mechanisms (capillary trapping, dissolution, and mineralization) must be considered. Capillary trapping may be very important in providing a "secondary-seal", and is the focus of our investigation. The physical mechanism of CO2 trapping in porous media by capillary trapping incorporates three related processes, i.e. residual trapping, trapping due to hysteresis of the relative permeability, and trapping due to hysteresis of the capillary pressure. Additionally CO2 may be trapped in heterogeneous media due to difference in capillary pressure entry points for different materials. The amount of CO2 trapped by these processes is a complicated nonlinear function of the spatial distribution of permeability, permeability anisotropy, capillary pressure, relative permeability of brine and CO2, permeability hysteresis and residual gas saturation (as well as the rate, total amount and placement of injected CO2). Geological heterogeneities essentially affect the dynamics of a CO2 plume in subsurface environments. Recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to the performance of some deep saline reservoirs [1, 2]. We investigated how the dynamics of a CO2 plume, during and after injection, is influenced by the hierarchical and multi-scale stratal architecture in such reservoirs. The results strongly suggest that representing these small scales features, and representing how they are organized within a hierarchy of larger-scale features, is critical to understanding capillary trapping processes. References [1] Bridge, J.S. (2006), Fluvial facies models: Recent developments, in Facies Models Revisited, SEPM Spec. Publ., 84, edited by H. W. Posamentier and R. G. Walker, pp. 85-170, Soc. for Sediment. Geol. (SEPM), Tulsa, Okla [2] Ramanathan, R., A. Guin, R.W. Ritzi, D.F. Dominic, V.L. Freedman, T.D. Scheibe, and I.A. Lunt (2010), Simulating the heterogeneity in channel belt deposits: Part 1. A geometric-based methodology and code, Water Resources Research, v. 46, W04515.

Gershenzon, Naum I.; Soltanian, Mohamadreza; Ritzi, Robert W., Jr.; Dominic, David F.

2014-05-01

8

Novel electrodynamic trapping mechanism for neutral, polar particles  

Microsoft Academic Search

A conceptually new trapping mechanism for neutral, polar particles is introduced and discussed. Unlike existing mechanisms\\u000a that are based on oscillating saddle-point potentials or rotating electric dipole fields, the new mechanism is based on a\\u000a superposition of ac and dc electric monopolefields that dynamically generate a minimum of the effective ponderomotive potential in which the particles are trapped. Extensive\\u000a numerical

R. Blümel

2011-01-01

9

Trapped rubber processing for advanced composites  

NASA Technical Reports Server (NTRS)

Trapped rubber processing is a molding technique for composites in which precast silicone rubber is placed within a closed cavity where it thermally expands against the composite's surface supported by the vessel walls. The method has been applied by the Douglas Aircraft Company, under contract to NASA-Langley, to the design and fabrication of 10 DC-10 graphite/epoxy upper aft rudder assemblies. A three-bay development tool form mold die has been designed and manufactured, and tooling parameters have been established. Fabrication procedures include graphite layup, assembly of details in the tool, and a cure cycle. The technique has made it possible for the cocured fabrication of complex primary box structures otherwise impracticable via standard composite material processes.

Marra, P. J.

1976-01-01

10

Investigation of plasma hydrogenation and trapping mechanism for layer transfer  

NASA Astrophysics Data System (ADS)

Hydrogen ion implantation is conventionally used to initiate the transfer of Si thin layers onto Si wafers coated with thermal oxide. In this work, we studied the feasibility of using plasma hydrogenation to replace high dose H implantation for layer transfer. Boron ion implantation was used to introduce H-trapping centers into Si wafers to illustrate the idea. Instead of the widely recognized interactions between boron and hydrogen atoms, this study showed that lattice damage, i.e., dangling bonds, traps H atoms and can lead to surface blistering during hydrogenation or upon postannealing at higher temperature. The B implantation and subsequent processes control the uniformity of H trapping and the trap depths. While the trap centers were introduced by B implantation in this study, there are many other means to do the same without implantation. Our results suggest an innovative way to achieve high quality transfer of Si layers without H implantation at high energies and high doses.

Chen, Peng; Chu, Paul K.; Höchbauer, T.; Lee, J.-K.; Nastasi, M.; Buca, D.; Mantl, S.; Loo, R.; Caymax, M.; Alford, T.; Mayer, J. W.; Theodore, N. David; Cai, M.; Schmidt, B.; Lau, S. S.

2005-01-01

11

Demonstration of a Scalable, Multiplexed Ion Trap for Quantum Information Processing.  

National Technical Information Service (NTIS)

A scalable, multiplexed ion trap for quantum information processing is fabricated and tested. The trap design and fabrication process are optimized for scalability to small trap size and large numbers of interconnected traps, and for integration of contro...

D. R. Leibrandt I. L. Chuang J. Labaziewicz R. J. Clark R. J. Epstein

2009-01-01

12

Novel electrodynamic trapping mechanism for neutral, polar particles  

NASA Astrophysics Data System (ADS)

A conceptually new trapping mechanism for neutral, polar particles is introduced and discussed. Unlike existing mechanisms that are based on oscillating saddle-point potentials or rotating electric dipole fields, the new mechanism is based on a superposition of ac and dc electric monopolefields that dynamically generate a minimum of the effective ponderomotive potential in which the particles are trapped. Extensive numerical simulations of the dynamics and the stability properties of trapped HC17N molecules and ferroelectric rods (made of barium titanate or croconic acid crystals) prove the validity of the new mechanism. The examples show that the same mechanism is applicable to the trapping of macroscopic as well as microscopic particles. The numerical results are backed by a physical pseudo-potential picture and an analytical stability analysis that provide physical insight into why and how the new mechanism works. A semi-quantum, Born-Oppenheimer-type calculation that treats the intrinsic rotational degree of freedom of HC17N quantum mechanically is also presented. A detailed discussion of engineering aspects shows that laboratory implementation of the new mechanism is within current technological reach.

Blümel, R.

2011-09-01

13

Hopping and trapping mechanisms in organic field-effect transistors  

NASA Astrophysics Data System (ADS)

A charge carrier in the channel of an organic field-effect transistor (OFET) is coupled to the electric polarization of the gate in the form of a surface Fröhlich polaron [N. Kirova and M. N. Bussac, Phys. Rev. B 68, 235312 (2003)]. We study the effects of the dynamical field of polarization on both small-polaron hopping and trap-limited transport mechanisms. We present numerical calculations of polarization energies, band-narrowing effects due to polarization, hopping barriers, and interface trap depths in pentacene and rubrene transistors as functions of the dielectric constant of the gate insulator and demonstrate that a trap-and-release mechanism more appropriately describes transport in high-mobility OFETs. For mobilities on the order 0.1cm2/Vs and below, all states are highly localized and hopping becomes the predominant mechanism.

Konezny, S. J.; Bussac, M. N.; Zuppiroli, L.

2010-01-01

14

Ion funnel ion trap and process  

DOEpatents

An ion funnel trap is described that includes a inlet portion, a trapping portion, and a outlet portion that couples, in normal operation, with an ion funnel. The ion trap operates efficiently at a pressure of .about.1 Torr and provides for: 1) removal of low mass-to-charge (m/z) ion species, 2) ion accumulation efficiency of up to 80%, 3) charge capacity of .about.10,000,000 elementary charges, 4) ion ejection time of 40 to 200 .mu.s, and 5) optimized variable ion accumulation times. Ion accumulation with low concentration peptide mixtures has shown an increase in analyte signal-to-noise ratios (SNR) of a factor of 30, and a greater than 10-fold improvement in SNR for multiply charged analytes.

Belov, Mikhail E [Richland, WA; Ibrahim, Yehia M [Richland, WA; Clowers, Biran H [West Richland, WA; Prior, David C [Hermiston, OR; Smith, Richard D [Richland, WA

2011-02-15

15

Mechanical model of the ultrafast underwater trap of Utricularia.  

PubMed

The underwater traps of the carnivorous plants of the Utricularia species catch their prey through the repetition of an "active slow deflation followed by passive fast suction" sequence. In this paper, we propose a mechanical model that describes both phases and strongly supports the hypothesis that the trap door acts as a flexible valve that buckles under the combined effects of pressure forces and the mechanical stimulation of trigger hairs, and not as a panel articulated on hinges. This model combines two different approaches, namely (i) the description of thin membranes as triangle meshes with strain and curvature energy, and (ii) the molecular dynamics approach, which consists of computing the time evolution of the position of each vertex of the mesh according to Langevin equations. The only free parameter in the expression of the elastic energy is the Young's modulus E of the membranes. The values for this parameter are unequivocally obtained by requiring that the trap model fires, like real traps, when the pressure difference between the outside and the inside of the trap reaches about 15 kPa. Among other results, our simulations show that, for a pressure difference slightly larger than the critical one, the door buckles, slides on the threshold, and finally swings wide open, in excellent agreement with the sequence observed in high-speed videos. PMID:21405867

Joyeux, Marc; Vincent, Olivier; Marmottant, Philippe

2011-02-01

16

Mechanical model of the ultrafast underwater trap of Utricularia  

NASA Astrophysics Data System (ADS)

The underwater traps of the carnivorous plants of the Utricularia species catch their prey through the repetition of an “active slow deflation followed by passive fast suction” sequence. In this paper, we propose a mechanical model that describes both phases and strongly supports the hypothesis that the trap door acts as a flexible valve that buckles under the combined effects of pressure forces and the mechanical stimulation of trigger hairs, and not as a panel articulated on hinges. This model combines two different approaches, namely (i) the description of thin membranes as triangle meshes with strain and curvature energy, and (ii) the molecular dynamics approach, which consists of computing the time evolution of the position of each vertex of the mesh according to Langevin equations. The only free parameter in the expression of the elastic energy is the Young's modulus E of the membranes. The values for this parameter are unequivocally obtained by requiring that the trap model fires, like real traps, when the pressure difference between the outside and the inside of the trap reaches about 15 kPa. Among other results, our simulations show that, for a pressure difference slightly larger than the critical one, the door buckles, slides on the threshold, and finally swings wide open, in excellent agreement with the sequence observed in high-speed videos.

Joyeux, Marc; Vincent, Olivier; Marmottant, Philippe

2011-02-01

17

Trapped interacting Bose gas in nonextensive statistical mechanics  

NASA Astrophysics Data System (ADS)

We study the Bose-Einstein condensation (BEC) phenomenon in an interacting trapped Bose gas using the semiclassical two-fluid model and nonextensive statistical mechanics. The effects of nonextensivity characterized by a parameter are explored by calculating the temperature dependent thermodynamic properties, fraction of condensed particles, and density distributions of condensed and thermal components of the system. It is found that nonextensivity in the underlying statistical mechanics may have large effects on the BEC transition temperature.

Tanatar, B.

2002-04-01

18

Process-dependent residual trapping of CO2 in sandstone  

NASA Astrophysics Data System (ADS)

paper demonstrates that the nature and extent of residual CO2 trapping depend on the process by which the CO2 phase is introduced into the rock. We compare residual trapping of CO2 in Berea Sandstone by imbibing water into a core containing either exsolved CO2 or CO2 introduced by drainage. X-ray computed tomography measurements are used to map the spatial distribution of CO2 preimbibition and postimbibition. Unlike during drainage where the CO2 distribution is strongly influenced by the heterogeneity of the rock, the distribution of exsolved CO2 is comparatively uniform. Postimbibition, the CO2 distribution retained the essential features for both the exsolved and drainage cases, but twice as much residual trapping is observed for exsolved CO2 even with similar preimbibition gas saturations. Residually trapped exsolved gas also disproportionately reduced water relative permeability. Development of process-dependent parameterization will help better manage subsurface flow processes and unlock benefits from gas exsolution.

Zuo, Lin; Benson, Sally M.

2014-04-01

19

Optimization geological sequestration of CO2 by capillary trapping mechanisms  

NASA Astrophysics Data System (ADS)

Geological carbon sequestration, as a method of atmospheric greenhouse gas reduction, is at the technological forefront of the climate change movement. Sequestration is achieved by capturing carbon dioxide (CO2) gas effluent from coal fired power plants and injecting it into saline aquifers. In an effort to fully understand and optimize CO2 trapping efficiency, the capillary trapping mechanisms that immobilize subsurface CO2 were analyzed at the pore scale. Pairs of analogous fluids representing the range of in situ supercritical CO2 and brine conditions were used during experimentation. The two fluids (identified as wetting and non wetting) were imbibed and drained from a flow cell apparatus containing a sintered glass bead column. Experimental and fluid parameters, such as interfacial tension, non-wetting fluid viscosity, and flow rate, were altered to characterize their impact on capillary trapping. Through the use of computed x-ray microtomography (CMT), we were able to quantify distinct differences between initial (post NW phase imbibition) and residual (post wetting fluid flood) non-wetting phase saturations. Alterations to the viscosity of the non-wetting and wetting fluid phases were made during experimentation; results indicate that the viscosity of the non-wetting fluid is the parameter of interest as residual saturations increased with increasing viscosity. These observed trends will be used to identify optimal conditions for trapping CO2 during subsurface sequestration.

Wildenschild, D.; Harper, E.; Herring, A. L.; Armstrong, R. T.

2012-12-01

20

Precision alignment of integrated optics in surface electrode ion traps for quantum information processing  

NASA Astrophysics Data System (ADS)

The integration of optics for efficient light delivery and the collection of fluorescence from trapped ions in surface electrode ion traps is a key component to achieving scalability for quantum information processing. Diffractive optical elements (DOEs) present a promising approach as compared to bulk optics because of their small physical profile and their flexibility in tailoring the optical wavefront. The precise alignment of the optics for coupling fluorescence to and from the ions, however, poses a particular challenge. Excitation and manipulation of the ions requires a high degree of optical access, significantly restricting the area available for mounting components. The ion traps, DOEs, and other components are compact, constraining the manipulation of various elements. For efficient fluorescence collection from the ions the DOE must be have a large numerical aperture (NA), which results in greater sensitivity to misalignment. The ion traps are sensitive devices, a mechanical approach to alignment such as contacting the trap and using precision motors to back-off a set distance not only cannot achieve the desired alignment precision, but risks damage to the ion trap. We have developed a non-contact precision optical alignment technique. We use line foci produced by off-axis linear Fresnel zone plates (FZPs) projected on alignment targets etched in the top metal layer of the ion trap and demonstrate micron-level alignment accuracy.

Young, Amber L.; Hunker, Jeffrey D.; Ellis, A. Robert; Samora, Sally; Wendt, Joel R.; Stick, Daniel L.

2014-03-01

21

Quantum Information Processing and Ramsey Spectroscopy with Trapped Ions  

Microsoft Academic Search

High-resolution laser spectroscopy and quantum information processing have a great deal in common. For both applications, ions held in electromagnetic traps can be employed, the ions' quantum state being manipulated by lasers. Quantum superposition states play a key role, and information about the experiment is inferred from a quantum state measurement that projects the ions' superposition state onto one of

C. F. Roos; M. Chwalla; T. Monz; P. Schindler; K. Kim; M. Riebe; R. Blatt

2008-01-01

22

Measurements of cell wall mechanical properties using optically trapped fluorescent microspheres  

NASA Astrophysics Data System (ADS)

Information on plasma membrane (PM) and cell wall mechanical properties is important for many biophysical applications, especially for those, which involve cells, undergoing significant mechanical stress (red blood cells, outer hair cells, fibrocytes, etc.). Optical tweezers is frequently used to study PM mechanics, particularly by pulling long PM tethers. One of the limitations on using optical tweezers to study cell wall mechanics is associated with transillumination technique of the trapped object position sensing, which prevents accurate mechanical testing in the proximity to the cell. In this work we use an optical tweezers in conjunction with a position-sensing system, which spectrally separates signals from the trapped fluorescent microsphere and imaging background. We have used this setup to study mechanics of the cell wall and PM separated from the underlying cytoskeleton on human embryonic kidney cells. We measured the force exerted by the cell on the trapped microsphere as a function of the cell wall displacement during the process of tether formation, and as a function of time during the process of tether growth and relaxation. Tethering force - cell wall displacement profiles have shown a behavior, implying that tether formation process starts with elastic deformation of the intact cell wall, followed by the plastic deformations and sliding of the PM over the underlying cytoskeleton, and ends with the local separation of a PM. Tethering force - cell wall displacement profiles have been used to estimate tether formation force, stiffness parameter of the cell wall and the works of tether formation, elastic and plastic deformations of the cell wall, related to the mechanical properties of a composite cell wall and cell wall - plasma membrane association strength. Temporal steady-state and relaxation tethering force profiles have been similar to the ones measured using transillumination position sensing, however average force values have been smaller in our case, due to the methodological differences. Our results demonstrate that measurements of cell wall and PM mechanical properties using optically-trapped fluorescent microspheres presents a versatile technology for studying of the cellular mechanics, especially effective in the proximity of the trapped microsphere to the cell.

Ermilov, Sergey; Qian, Feng; Murdock, David; Brownell, William E.; Anvari, Bahman

2004-10-01

23

Trapping mechanisms of Minnelusa oil accumulations, northeastern Powder River basin, Wyoming  

Microsoft Academic Search

This paper defines and documents trapping mechanisms present in the Permian age Minnelusa oil fields of the NE. Powder River Basin, Wyoming. By far the largest portion of the Minnelusa oil in place has been trapped by paleotopographic highs occurring at the unconformity at the top of the Minnelusa Formation. Smaller amounts of Minnelusa oil have been trapped by updip

Van West

1972-01-01

24

Photocarrier transport and trapping processes in doped polyethylene terephthalate films  

SciTech Connect

The radiation-induced conductivity of polyethylene terephthalate film is modified by doping this polymer with electron acceptor molecules. Detailed results of x-ray induced thermally stimulated current and photoconductivity experiments are reported for one dopant, 2, 4, 7-trinitro-9-fluorenone. At dopant concentrations< or approx. =10/sup 19/ molecules/cm/sup 3/, this impurity acts as a deep trap for photocarriers, radically decreasing the radiation-induced conductivity of the doped film. The kinetics of photocarrier trapping in a host material exhibiting dispersive transport is discussed. At dopant concentrations > or approx. =10/sup 20/ molecules/cm/sup 3/, the radiation-induced conductivity increases due to the onset of photocarrier transport among the electron acceptor molecules. Utilizing the physical processes discussed in this work, it is possible to develop dielectric materials displaying selected levels of radiation-induced conductivity.

Kurtz, S.R.; Arnold, C. Jr.

1985-04-01

25

Modeling trapping mechanism for PCB adsorption on activated carbon  

NASA Astrophysics Data System (ADS)

The levels of polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofuran (PCDD/F) and dioxin-like polychlorinated biphenyl (DL-PCB) in fishmeal and fish oil produced for use in feed for salmon is above present European legislation levels in some regions of the world and different decontamination approaches have been proposed [1]. One of these is adsorption on activated carbon. This approach appears to be efficient for adsorption of PCDD/F but less efficient for DL-PCB [2]. Activated carbon consists of slit pores with average sizes of 20 - 50 A?ngstroms. One hypothesis [2] for the mechanism of trapping DL-PCB is reduced ability for intramolecular movements of the PCB molecules inside the slit pores. In order to investigate this hypothesis we have used quantum mechanics [3] to characterize two DL-PCB congeners, respectively congener 77 (3,3',4,4'-Tetrachlorobiphenyl) and congener 118 (2,3',4,4',5-Pentachlorobiphenyl) and Triolein (18:1) [4] as a major constituent of the solvent fish oil. A model for activated carbon was constructed using a crystal structure of graphite from the American Mineralogist Crystal Structure Database [5]. The crystal structure used was originally from Wyckoff [6]. A small program had to be written to generate the desired graphite structure as it contains no less than 31232 Carbon atoms. Partial atomic charges were estimated using QM with DFT/B3LYP/6-311+g** and SM6 [7].

Jensen, Bjørnar; Kvamme, Bjørn; Kuznetsova, Tatyana; Oterhals, A.?ge

2012-12-01

26

A family of synthetic riboswitches adopts a kinetic trapping mechanism  

PubMed Central

Riboswitches are sequences of RNA that control gene expression via RNA–ligand interactions, without the need for accessory proteins. Riboswitches consist of an aptamer that recognizes the ligand and an expression platform that couples ligand binding to a change in gene expression. Using in vitro selection, it is possible to screen large (?1013 members) libraries of RNA sequences to discover new aptamers. However, limitations in bacterial transformation efficiency make screening such large libraries for riboswitch function in intact cells impractical. Here we show that synthetic riboswitches function in an E. coli S30 extract in a manner similar to how they function in intact E. coli cells. We discovered that, although this family of riboswitches regulates the initiation of protein translation, the fate of whether an RNA message is translated is determined during transcription. Thus, ligand binding does not bias a population of rapidly equilibrating RNA structures, but rather, co-transcriptional ligand binding kinetically traps the RNA in a conformation that supports efficient translation. In addition to providing new insights into the mechanisms of action of a family of synthetic riboswitches, our experiments suggest that it may be possible to perform selections for novel synthetic riboswitches in an in vitro system.

Mishler, Dennis M.; Gallivan, Justin P.

2014-01-01

27

Spontaneous firings of carnivorous aquatic Utricularia traps: temporal patterns and mechanical oscillations.  

PubMed

Aquatic species of Utricularia are carnivorous plants living in environments poor in nutrients. Their trapping mechanism has fascinated generations of scientists and is still debated today. It was reported recently that Utricularia traps can fire spontaneously. We show here that these spontaneous firings follow an unexpected diversity of temporal patterns, from "metronomic" traps which fire at fixed time intervals to "random" patterns, displaying more scattered firing times. Some "bursting" traps even combine both aspects, with groups of fast regular firings separated by a variable amount of time. We propose a physical model to understand these very particular behaviors, showing that a trap of Utricularia accomplishes mechanical oscillations, based on continuous pumping and sudden opening of the trap door (buckling). We isolate the key parameters governing these oscillations and discuss the effect of their fluctuations. PMID:21647417

Vincent, Olivier; Roditchev, Ivan; Marmottant, Philippe

2011-01-01

28

Investigation of Aging Mechanisms in Lean NOx Traps  

SciTech Connect

Lean NO{sub x} traps (LNTs) represent a promising technology for the abatement of NO{sub x} under lean conditions. Although LNTs are starting to find commercial application, the issue of catalyst durability remains problematic. LNT susceptibility to sulfur poisoning is the single most important factor determining effective catalyst lifetime. The NO{sub x} storage element of the catalyst has a greater affinity for SO{sub 3} than it does for NO{sub 2}, and the resulting sulfate is more stable than the stored nitrate. Although this sulfate can be removed from the catalyst by means of high temperature treatment under rich conditions, the required conditions give rise to deactivation mechanisms such as precious metal sintering, total surface area loss, and solid state reactions between the various oxides present. The principle objective of this project was to improve understanding of the mechanisms of lean NO{sub x} trap aging, and to understand the effect of washcoat composition on catalyst aging characteristics. The approach utilized involved detailed characterization of model catalysts prior to and after aging, in tandem with measurement of catalyst performance in NO{sub x} storage and reduction. In this manner, NO{sub x} storage and reduction characteristics were correlated with the evolution of catalyst physico-chemical properties upon aging. Rather than using poorly characterized proprietary catalysts, or simple model catalysts of the Pt/BaO/Al{sub 2}O{sub 3} type (representing the first generation of LNTs), Pt/Rh/BaO/Al{sub 2}O{sub 3} catalysts were employed which also incorporated CeO{sub 2} or CeO{sub 2}-ZrO{sub 2}, representing a model system which more accurately reflects current LNT formulations. Catalysts were prepared in which the concentration of each of the main components was systematically varied: Pt (50, 75 or 100 g/ft{sup 3}), Rh (10 or 20 g/ft{sup 3}), BaO (15, 30 or 45 g/L), and either CeO{sub 2} (0, 50 or 100 g/L) or CeO{sub 2}-ZrO{sub 2} (0, 50 or 100 g/L). A high surface area La-stabilized alumina was used to support the BaO phase. Catalysts were obtained by washcoating onto standard cordierite substrates, the total washcoat loading being set at 260 g/L. La-stabilized alumina was used as the balance. Subsequent to de-greening, the NO{sub x} storage and reduction characteristics of the catalysts were evaluated on a bench reactor, after which the catalysts were aged on a bench reactor to the equivalent of ca. 75,000 miles of road aging using a published accelerated aging protocol. The aged catalysts were then subjected to the same evaluation proecdure used for the de-greened catalysts. In addition to the use of standard physico-chemical analytical techniques for studying the fresh and aged model catalysts, use was made of advanced analytical tools for characterizing their NO{sub x} storage/reduction and sulfation/desulfation characteristics, such as Spatially resolved capillary-inlet Mass Spectrometry (SpaciMS) and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS).

Mark Crocker

2010-03-31

29

Magnetic trapping of neutral particles: Classical and quantum-mechanical study of a Ioffe-Pritchard type trap  

NASA Astrophysics Data System (ADS)

Recently, we developed a method for calculating the lifetime of a particle inside a magnetic trap with respect to spin flips, as a first step in our efforts to understand the quantum mechanics of magnetic traps. The one-dimensional toy model that was used in this study was physically unrealistic because the magnetic field was not curl free. Here, we study, both classically and quantum mechanically, the problem of a neutral particle with spin S, mass m, and magnetic moment ?, moving in three dimensions in an inhomogeneous magnetic field corresponding to traps of the Ioffe-Pritchard ``clover-leaf'' and ``baseball'' type. Defining by ?p, ?z, and ?r the precessional, the axial, and the lateral vibrational frequencies, respectively, of the particle in the adiabatic potential Veff =?|B|, we find classically the region in the (?r/?p)-(?z/?p) plane where the particle is trapped. Quantum mechanically, we study the problem of a spin-one particle in the same field. Treating ?r/?p and ?z/?p as small parameters for the perturbation from the adiabatic Hamiltonian, we derive a closed-form expression for the transition rate 1/Tesc of the particle from its trapped ground state. In the extreme cases, the expression for 1/Tesc reduces to 4??r exp(-2?p/?r) for ?p>>?r>>?z, to 82??p?i exp(-2?p/?i) for ?p>>?r=?z??i and to ?/2 ?r(?z/?p)3/2exp(-2?p/?z) for ?p>>?z>>?r.

Gov, S.; Shtrikman, S.; Thomas, H.

2000-04-01

30

Electrons in a cryogenic planar Penning trap and experimental challenges for quantum processing  

Microsoft Academic Search

We report on trapping of clouds of electrons in a\\u000a cryogenic planar Penning trap at T ?100 mK. We describe the\\u000a experimental conditions to load, cool and detect electrons.\\u000a Perspectives for the trapping of a single electron and for quantum\\u000a information processing are given.

P. Bushev; S. Stahl; R. Natali; G. Marx; E. Stachowska; G. Werth; M. Hellwig; F. Schmidt-Kaler

2008-01-01

31

Molecular Ion Dissociation Processes in a Partially Cooled Electrostatic Trap  

NASA Astrophysics Data System (ADS)

An experimental capability being developed at the Oak Ridge National Laboratory Multi-Charged Ion Research Facility (ORNL MIRF) is described that enables stored cooling and state characterization of atomic and molecular ions of essentially any mass. Ions selected from a variety of available (hot and cold) sources are injected into a 1.5 meter long electrostatic mirror trap, in which excited internal states decay by radiative cooling. Ion lifetime studies or direct measurements of 'in-trap' interactions of molecular ions with electrons or atomic targets are accomplished with either a crossed electron beam or atomic beam (with recoil ion detection) located in the field-free region of the ion-trap, coupled with product velocity imaging. Similarly, extraction of trap-cooled ions can be used 'out-of-trap' for near state-specific electron capture (EC) and dissociative charge exchange (DCE) studies employing higher resolution COLTRIMS techniques coupled with fragment imaging.

Vane, C. R.; Bannister, M. E.; Deng, S.; Fogle, M.; Thomas, R. D.

2011-07-01

32

Optimization of exciton trapping in energy transfer processes.  

PubMed

In this paper, we establish optimal conditions for maximal energy transfer efficiency using solutions for multilevel systems and interpret these analytical solutions with more intuitive kinetic networks resulting from a systematic mapping procedure. The mapping procedure defines an effective hopping rate as the leading order picture and nonlocal kinetic couplings as the quantum correction, hence leading to a rigorous separation of thermal hopping and coherent transfer useful for visualizing pathway connectivity and interference in quantum networks. As a result of these calculations, the dissipative effects of the surrounding environments can be optimized to yield the maximal efficiency, and modulation of the efficiency can be achieved using the cumulative quantum phase along any closed loops. The optimal coupling of the system and its environments is interpreted with the generic mechanisms: (i) balancing localized trapping and delocalized coherence, (ii) reducing the effective detuning via homogeneous line-broadening, (iii) suppressing the destructive interference in nonlinear network configurations, and (iv) controlling phase modulation in closed loop configurations. Though these results are obtained for simple model systems, the physics thus derived provides insights into the working of light harvesting systems, and the approaches thus developed apply to large-scale computation. PMID:19929005

Cao, Jianshu; Silbey, Robert J

2009-12-17

33

Hydrodynamic mechanisms of cell and particle trapping in microfluidics  

PubMed Central

Focusing and sorting cells and particles utilizing microfluidic phenomena have been flourishing areas of development in recent years. These processes are largely beneficial in biomedical applications and fundamental studies of cell biology as they provide cost-effective and point-of-care miniaturized diagnostic devices and rare cell enrichment techniques. Due to inherent problems of isolation methods based on the biomarkers and antigens, separation approaches exploiting physical characteristics of cells of interest, such as size, deformability, and electric and magnetic properties, have gained currency in many medical assays. Here, we present an overview of the cell/particle sorting techniques by harnessing intrinsic hydrodynamic effects in microchannels. Our emphasis is on the underlying fluid dynamical mechanisms causing cross stream migration of objects in shear and vortical flows. We also highlight the advantages and drawbacks of each method in terms of throughput, separation efficiency, and cell viability. Finally, we discuss the future research areas for extending the scope of hydrodynamic mechanisms and exploring new physical directions for microfluidic applications.

Karimi, A.; Yazdi, S.; Ardekani, A. M.

2013-01-01

34

Trapping and luminescence mechanisms in manganese-doped zinc silicate phosphorsa tunneling model  

NASA Astrophysics Data System (ADS)

We have investigated electron trapping and luminescence (phosphorescence, thermoluminescence and photostimulated luminescence) mechanisms in Mn and Mn+As doped Zn2SiO4 phosphors. The intensities of both the phosphorescence and photostimulated luminescence are found to decay with time approximately as (time)-1. The generally accepted model of such a decay of phosphorescence, based on thermal release of electrons from a broad distribution of trap energy levels, cannot explain the observed decay of the photostimulated luminescence. In order to explain both results we have developed a new model based on radiative recombination by tunneling between holes trapped on Mn ions and electrons in shallow traps or in excited states of the deeper traps. We derive a simple expression which describes for both experiments at all times the decay of the light intensity and its dependence on experimental conditions. The agreement between theory and experiment is found to be excellent.

Avouris, Ph.; Chang, I. F.; Dove, D.; Morgan, T. N.; Thefaine, Y.

1981-09-01

35

Arbitrary waveform generator for quantum information processing with trapped ions.  

PubMed

Atomic ions confined in multi-electrode traps have been proposed as a basis for scalable quantum information processing. This scheme involves transporting ions between spatially distinct locations by use of time-varying electric potentials combined with laser or microwave pulses for quantum logic in specific locations. We report the development of a fast multi-channel arbitrary waveform generator for applying the time-varying electric potentials used for transport and for shaping quantum logic pulses. The generator is based on a field-programmable gate array controlled ensemble of 16-bit digital-to-analog converters with an update frequency of 50 MHz and an output range of ±10 V. The update rate of the waveform generator is much faster than relevant motional frequencies of the confined ions in our experiments, allowing diabatic control of the ion motion. Numerous pre-loaded sets of time-varying voltages can be selected with 40 ns latency conditioned on real-time signals. Here we describe the device and demonstrate some of its uses in ion-based quantum information experiments, including speed-up of ion transport and the shaping of laser and microwave pulses. PMID:23556808

Bowler, R; Warring, U; Britton, J W; Sawyer, B C; Amini, J

2013-03-01

36

Nonvolatile multilevel data storage memory device from controlled ambipolar charge trapping mechanism  

PubMed Central

The capability of storing multi-bit information is one of the most important challenges in memory technologies. An ambipolar polymer which intrinsically has the ability to transport electrons and holes as a semiconducting layer provides an opportunity for the charge trapping layer to trap both electrons and holes efficiently. Here, we achieved large memory window and distinct multilevel data storage by utilizing the phenomena of ambipolar charge trapping mechanism. As fabricated flexible memory devices display five well-defined data levels with good endurance and retention properties showing potential application in printed electronics.

Zhou, Ye; Han, Su-Ting; Sonar, Prashant; Roy, V. A. L.

2013-01-01

37

Nonvolatile multilevel data storage memory device from controlled ambipolar charge trapping mechanism.  

PubMed

The capability of storing multi-bit information is one of the most important challenges in memory technologies. An ambipolar polymer which intrinsically has the ability to transport electrons and holes as a semiconducting layer provides an opportunity for the charge trapping layer to trap both electrons and holes efficiently. Here, we achieved large memory window and distinct multilevel data storage by utilizing the phenomena of ambipolar charge trapping mechanism. As fabricated flexible memory devices display five well-defined data levels with good endurance and retention properties showing potential application in printed electronics. PMID:23900459

Zhou, Ye; Han, Su-Ting; Sonar, Prashant; Roy, V A L

2013-01-01

38

Molecular Mechanisms of the Interaction Between Nematode-Trapping Fungi and Nematodes: Lessons From Genomics  

Microsoft Academic Search

\\u000a Soil contains a diverse range of fungi that are parasites on nematodes. These fungi include the nematode-trapping fungi that\\u000a are dependent on specific hyphal structures on or in which nematodes can be trapped mechanically or by adhesion. The interests\\u000a of studying these fungi come from their potential use as biological control agents against plant- and animal-parasitic nematodes.\\u000a Studies on the

Anders Tunlid; Dag Ahrén

39

Use dependence of tetrodotoxin block of sodium channels: a revival of the trapped-ion mechanism.  

PubMed Central

The use-dependent block of sodium channels by tetrodotoxin (TTX) has been studied in cRNA-injected Xenopus oocytes expressing the alpha-subunit of rat brain IIA channels. The kinetics of stimulus-induced extra block are consistent with an underlying relaxation process involving only three states. Cumulative extra block induced by repetitive stimulations increases with hyperpolarization, with TTX concentration, and with extracellular Ca2+ concentration. We have developed a theoretical model based on the suggestion by Salgado et al. that TTX blocks the extracellular mouth of the ion pore less tightly when the latter has its external side occupied by a cation, and that channel opening favors a tighter binding by allowing the escape of the trapped ion. The model provides an excellent fit of the data, which are consistent with Ca2+ being more efficient than Na+ in weakening TTX binding and with bound Ca2+ stabilizing the closed state of the channel, as suggested by Armstrong and Cota. Reports arguing against the trapped-ion mechanism are critically discussed.

Conti, F; Gheri, A; Pusch, M; Moran, O

1996-01-01

40

Evaluation of the Forrester-Hepburn Mechanism as an Artifact Source in ESR Spin-Trapping  

PubMed Central

Nitrone spin traps such as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) are commonly used for free radical detection. Though proven examples are rare, artifact formation must be considered. For example, the Forrester-Hepburn mechanism yields the same radical adduct as formed by genuine radical trapping. A hydroxylamine is formed by nucleophilic attack of the substrate to DMPO and subsequently oxidized to the respective nitroxide radical. One potential candidate for this artifact is the sulfur trioxide radical adduct (DMPO/·SO3?), as detected in spin-trapping experiments with horseradish peroxidase and sulfite. It has previously been shown by NMR experiments that the hydroxylamine intermediate does indeed form, but no direct proof for the ESR artifact has been provided. Here we used isotopically labeled DMPO with horseradish peroxidase and ferricyanide to test for the Forrester-Hepburn artifact directly in a spin-trapping experiment. Besides sulfite, we investigated other nucleophiles such as cyanide, cysteine and glutathione. Neither sulfite nor biological thiols produced detectable spin-trapping artifacts, but with cyanide the relatively weak signal originated almost entirely from the nucleophilic reaction. The hydroxylamine intermediate, which is more abundant with cyanide than with sulfite, was identified as cyano-hydroxylamine by means of 2D NMR experiments. Although our study found that spin trapping provided authentic free radical signals with most of the substrates, the occurrence of the Forrester Hepburn mechanism artifact with cyanide emphasizes the importance of isotope measurements with nucleophile substrates.

Leinisch, Fabian; Ranguelova, Kalina; DeRose, Eugene; Jiang, JinJie; Mason, Ronald P.

2012-01-01

41

Mechanism of decay of trapped magnetic field in HTS bulk caused by application of AC magnetic field  

Microsoft Academic Search

In our previous work, it was observed that trapped magnetic field in an high-temperature superconductor (HTS) bulk was decayed and even erased by application of AC external field whose amplitude was much smaller than the peak value of the trapped magnetic field. Therefore, knowledge on the mechanism of the decay of the trapped magnetic field is important to design the

O. Tsukamoto; K. Yamagishi; J. Ogawa; M. Murakami; M. Tomita

2005-01-01

42

On the mechanism of trap closure of Venus flytrap ( Dionaea muscipula Ellis)  

Microsoft Academic Search

The rapid trap closure of Dionaea muscinula Ellis has been explained by either a loss of turgor pressure of the upper epidermis, which should thus become flexible, or by a sudden acid-induced wall loosening of the motor cells. According to our experiments both explanations are doubtful. Objections against the turgor mechanism come from the determination by extracellular measurements from the

Dieter Hodick; Andreas Sievers

1989-01-01

43

Molecular Mechanisms of Reversible and Irreversible Trapping of >Large DNA Molecules Undergoing Gel Electrophoresis  

NASA Astrophysics Data System (ADS)

Megabase-size DNA becomes trapped in agarose gels during electrophoresis if the electric field is greater than 2 V/cm. Fluorescence microscopy reveals that megabase molecules invariably arrest during the U-shape phase of their caterpillar cycle, adhering to the gel near the vertex of the U. The electric field dependence of the molecular sizes trapped in the gel has been determined and indicates a critical force above which molecules trap. The size of unligated ?-ladders sheared during electrophoresis at a given field is the same as the size of molecules trapped at that field and suggests that both processes occur through nick melting near the vertex of the U. Consistently, molecules nicked by exposure to UV radiation trapped more readily than un-exposed ones. To further characterize the nature of the molecule-gel interaction near the vertex, the electric force on tethered DNA molecules within a gel has been measured using laser tweezers, yielding an effective charge of 0.16 e^-/phos. This figure translates into a critical tension at the vertex of 15 pN, a force sufficient to melt nicks bent around corners in the gel path near the vertex, and to trap a molecule.

Bustamante, Carlos

1998-05-01

44

Nonlinearity from quantum mechanics: Dynamically unstable Bose-Einstein condensate in a double-well trap  

SciTech Connect

We study theoretically an atomic Bose-Einstein condensate in a double-well trap, both quantum-mechanically and classically, under conditions such that in the classical model an unstable equilibrium dissolves into large-scale oscillations of the atoms between the potential wells. Quantum mechanics alone does not exhibit such nonlinear dynamics, but measurements of the atom numbers in the potential wells may nevertheless cause the condensate to behave essentially classically.

Javanainen, Juha [Department of Physics, University of Connecticut, Storrs, Connecticut 06269-3046 (United States)

2010-05-15

45

Quantum Information Processing with Ytterbium Ions and a Frequency Comb in a Surface Trap  

NASA Astrophysics Data System (ADS)

Microfabricated surface ion traps are one of the key components for building a trapped ion quantum information processor.These multi-segmented traps are fabricated using existing silicon processing technology and can provide the fields to store a chain of ions and shuttle ions within the trap structure. Using a surface trap microfabricated by Sandia National Laboratories [1] we trap individual Yb-171 ions and demonstrate fundamental quantum information processing primitives. Low light scatter from the trap and the use of photon arrival times during fluorescence state detection enables a state detection fidelity of 98%. High fidelity rotations of the hyperfine clock state qubit have been performed using a resonant microwave field. Furthermore, we have realized single qubit rotations using Raman transitions driven by a repetition-rate stabilized frequency comb, a prerequisite for realizing motional gates with frequency combs [2]. Microelectromechanical systems (MEMS) mirrors will be used to focus Raman laser beams on individual ions in a chain to perform single qubit gates. MEMS beam steering systems can easily be scaled to multiple beams to realize two-ion gates between arbitrary ions in the chain.[4pt] [1] D Stick et al., arXiv:1008.0990v2 2010[0pt] [2] D Hayes et al., PRL 104(14)2010

Mount, Emily; Baek, So-Young; Gaultney, Daniel; Crain, Stephen; Noek, Rachel; Maunz, Peter; Kim, Jungsang

2012-06-01

46

Understanding the radical mechanism of lipoxygenases using 31P NMR spin trapping.  

PubMed

In this paper, we use our quantitative (31)P NMR spin trapping methods, already developed for simple oxygen- and carbon-centered radicals, to understand the radical intermediates generated by enzymatic systems and more specifically lipoxygenases. Our methodology rests on the fact that free radicals react with the nitroxide phosphorus compound, 5-diisopropoxy-phosphoryl-5-methyl-1-pyrroline-N-oxide (DIPPMPO), to form stable radical adducts, which are suitably detected and accurately quantified using (31)P NMR in the presence of a phosphorus containing internal standard. This system was thus applied to better understand the mechanism of enzymatic oxidation of linoleic acid by soybean lipoxygenases-1 (LOX). The total amount of radicals trapped by DIPPMPO was detected by (31)P NMR at different experimental conditions. In particular the effect of dioxygen concentration on the amount of radicals being trapped was studied. At low dioxygen concentration, a huge increase of radicals trapped was observed with respect to the amount of radicals being trapped at normal dioxygen concentrations. PMID:21474321

Zoia, Luca; Perazzini, Raffaella; Crestini, Claudia; Argyropoulos, Dimitris S

2011-05-01

47

Theory and Simulation of Neoclassical Transport Processes, with Local Trapping  

SciTech Connect

Neoclassical transport is studied using idealized simulations that follow guiding centers in given fields, neglecting collective effects on the plasma evolution, but including collisions at rate {nu}. For simplicity the magnetic field is assumed to be uniform; transport is due to asymmetries in applied electrostatic fields. Also, the Fokker-Planck equation describing the particle distribution is solved, and the predicted transport is found to agree with the simulations. Banana, plateau, and fluid regimes are identified and observed in the simulations. When separate trapped particle populations are created by application of an axisymmetric squeeze potential, enhanced transport regimes are observed, scaling as {radical}({nu}) when {nu}<{omega}{sub 0}<{omega}{sub b} and as 1/{nu} when {omega}{sub 0}<{nu}<{omega}{sub b} where {omega}{sub 0} and {omega}{sub b} are the rotation and axial bounce frequencies, respectively. These regimes are similar to those predicted for neoclassical transport in stellarators.

Dubin, Daniel H. E. [Department of Physics, University of California at San Diego, La Jolla, CA USA 92093-0319 (United States)

2009-03-30

48

With a Flick of the Lid: A Novel Trapping Mechanism in Nepenthes gracilis Pitcher Plants  

PubMed Central

Carnivorous pitcher plants capture prey with modified leaves (pitchers), using diverse mechanisms such as ‘insect aquaplaning’ on the wet pitcher rim, slippery wax crystals on the inner pitcher wall, and viscoelastic retentive fluids. Here we describe a new trapping mechanism for Nepenthes gracilis which has evolved a unique, semi-slippery wax crystal surface on the underside of the pitcher lid and utilises the impact of rain drops to ‘flick’ insects into the trap. Depending on the experimental conditions (simulated ‘rain’, wet after ‘rain’, or dry), insects were captured mainly by the lid, the peristome, or the inner pitcher wall, respectively. The application of an anti-slip coating to the lower lid surface reduced prey capture in the field. Compared to sympatric N. rafflesiana, N. gracilis pitchers secreted more nectar under the lid and less on the peristome, thereby directing prey mainly towards the lid. The direct contribution to prey capture represents a novel function of the pitcher lid.

Bauer, Ulrike; Di Giusto, Bruno; Skepper, Jeremy; Grafe, T. Ulmar; Federle, Walter

2012-01-01

49

Self-trapping mechanisms in the dynamics of three coupled Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

We formulate the dynamics of three coupled Bose-Einstein condensates within a semiclassical scenario based on the standard boson coherent states. We compare such a picture with that of K. Nemoto et al. [Phys. Rev. A 63, 013604 (2001)] and show how our approach entails a simple formulation of the dimeric regime therein studied. This allows us to recognize the parameters that govern the bifurcation mechanism causing self-trapping, and paves the way to the construction of analytic solutions.

Franzosi, Roberto; Penna, Vittorio

2002-01-01

50

Monitoring Stored-Product Pests in Food Processing Plants with Pheromone Trapping, Contour Mapping, and Mark-Recapture  

Microsoft Academic Search

Distribution and movement patterns of severalspecies of stored-product pests in a food processing plant were investigated. The objectives of this study were to determine the temporal and spatialvariation in abundance of stored-product pests using pheromone traps; assess the effectiveness of trap type, location, and number on monitoring insect populations; and to evaluate the nature of pheromone trap capture hot spots

J. F. Campbell; M. A. Mullen; A. K. Dowdy

2002-01-01

51

Active movements in plants: Mechanism of trap closure by Dionaea muscipula Ellis.  

PubMed

The Venus flytrap (Dionaea muscipula Ellis) captures insects with one of the most rapid movements in the plant kingdom. We investigated trap closure by mechanical and electrical stimuli using the novel charge-injection method and high-speed recording. We proposed a new hydroelastic curvature mechanism, which is based on the assumption that the lobes possess curvature elasticity and are composed of outer and inner hydraulic layers with different hydrostatic pressure. The open state of the trap contains high elastic energy accumulated due to the hydrostatic pressure difference between the hydraulic layers of the lobe. Stimuli open pores connecting the two layers, water rushes from one hydraulic layer to another, and the trap relaxes to the equilibrium configuration corresponding to the closed state. In this paper we derived equations describing this system based on elasticity Hamiltonian and found closing kinetics. The novel charge-injection stimulation method gives insight into mechanisms of the different steps of signal transduction and response in the plant kingdom. PMID:19513230

Markin, Vladislav S; Volkov, Alexander G; Jovanov, Emil

2008-10-01

52

Sensitivity of the Field Trapped by Superconducting Bulks on the Parameters of the Magnetization Process  

Microsoft Academic Search

Recent progress in material processing has enabled the fabrication of large single grain YBCO bulks having the potential to trap a magnetic field much stronger than that of conventional permanent magnets, thus opening the way to new applications in the field of power electric machinery. However, for YBCO bulks to find a broad use, a suitable magnetization process must be

Massimo Fabbri; Antonio Morandi; Francesco Negrini; Pier Luigi Ribani

2006-01-01

53

Chemically assisted mechanical refrigeration process  

DOEpatents

There is provided a chemically assisted mechanical refrigeration process including the steps of: mechanically compressing a refrigerant stream which includes vaporized refrigerant; contacting the refrigerant with a solvent in a mixer at a pressure sufficient to promote substantial dissolving of the refrigerant in the solvent in the mixer to form a refrigerant-solvent solution while concurrently placing the solution in heat exchange relation with a working medium to transfer energy to the working medium, said refrigerant-solvent solution exhibiting a negative deviation from Raoult's Law; reducing the pressure over the refrigerant-solvent solution in an evaporator to allow the refrigerant to vaporize and substantially separate from the solvent while concurrently placing the evolving refrigerant-solvent solution in heat exchange relation with a working medium to remove energy from the working medium to thereby form a refrigerant stream and a solvent stream; and passing the solvent and refrigerant stream from the evaporator. 5 figs.

Vobach, A.R.

1987-06-23

54

Chemically assisted mechanical refrigeration process  

DOEpatents

There is provided a chemically assisted mechanical refrigeration process including the steps of: mechanically compressing a refrigerant stream which includes vaporized refrigerant; contacting the refrigerant with a solvent in a mixer (11) at a pressure sufficient to promote substantial dissolving of the refrigerant in the solvent in the mixer (11) to form a refrigerant-solvent solution while concurrently placing the solution in heat exchange relation with a working medium to transfer energy to the working medium, said refrigerant-solvent solution exhibiting a negative deviation from Raoult's Law; reducing the pressure over the refrigerant-solvent solution in an evaporator (10) to allow the refrigerant to vaporize and substantially separate from the solvent while concurrently placing the evolving refrigerant-solvent solution in heat exchange relation with a working medium to remove energy from the working medium to thereby form a refrigerant stream and a solvent stream; and passing the solvent and refrigerant stream from the evaporator.

Vobach, Arnold R. (6006 Allentown Dr., Spring, TX 77389)

1987-01-01

55

Chemically assisted mechanical refrigeration process  

DOEpatents

There is provided a chemically assisted mechanical refrigeration process including the steps of: mechanically compressing a refrigerant stream which includes vaporized refrigerant; contacting the refrigerant with a solvent in a mixer (11) at a pressure sufficient to promote substantial dissolving of the refrigerant in the solvent in the mixer (11) to form a refrigerant-solvent solution while concurrently placing the solution in heat exchange relation with a working medium to transfer energy to the working medium, said refrigerant-solvent solution exhibiting a negative deviation from Raoult's Law; reducing the pressure over the refrigerant-solvent solution in an evaporator (10) to allow the refrigerant to vaporize and substantially separate from the solvent while concurrently placing he evolving refrigerant-solvent solution in heat exchange relation with a working medium to remove energy from the working medium to thereby form a refrigerant stream and a solvent stream; and passing the solvent and refrigerant stream from the evaporator.

Vobach, Arnold R. (6006 Allentown Dr., Spring, TX 77379)

1987-01-01

56

Chemically assisted mechanical refrigeration process  

DOEpatents

There is provided a chemically assisted mechanical refrigeration process including the steps of: mechanically compressing a refrigerant stream which includes vaporized refrigerant; contacting the refrigerant with a solvent in a mixer at a pressure sufficient to promote substantial dissolving of the refrigerant in the solvent in the mixer to form a refrigerant-solvent solution while concurrently placing the solution in heat exchange relation with a working medium to transfer energy to the working medium, said refrigerant-solvent solution exhibiting a negative deviation from Raoult's Law; reducing the pressure over the refrigerant-solvent solution in an evaporator to allow the refrigerant to vaporize and substantially separate from the solvent while concurrently placing the evolving refrigerant-solvent solution in heat exchange relation with a working medium to remove energy from the working medium to thereby form a refrigerant stream and a solvent stream; and passing the solvent and refrigerant stream from the evaporator. 5 figs.

Vobach, A.R.

1987-11-24

57

Different mechanics of snap-trapping in the two closely related carnivorous plants Dionaea muscipula and Aldrovanda vesiculosa  

Microsoft Academic Search

The carnivorous aquatic waterwheel plant (Aldrovanda vesiculosa L.) and the closely related terrestrial venus flytrap (Dionaea muscipula Sol. ex J. Ellis) both feature elaborate snap-traps, which shut after reception of an external mechanical stimulus by prey animals. Traditionally, Aldrovanda is considered as a miniature, aquatic Dionaea, an assumption which was already established by Charles Darwin. However, videos of snapping traps

Simon Poppinga; Marc Joyeux

2011-01-01

58

Equatorially trapped waves in varying basic states: Structures and lateral forcing processes  

Microsoft Academic Search

Linear shallow water equations on an equatorial beta-plane are used to theoretically investigate the effects of atmospheric basic state on equatorial waves. With different varying basic states, three main topics are addressed: eigenfrequencies and meridional structures of free equatorial waves; mechanism of equatorial Rossby wave trapping; and equatorial wave responses to transient extratropical forcings. The free Rossby wave is shown

Chi-Dong Zhang

1989-01-01

59

On the light trapping mechanism in silicon solar cells with backside diffraction gratings  

NASA Astrophysics Data System (ADS)

In this numerical study, we investigate the light trapping mechanism in silicon solar cells with backside diffraction gratings. In order to obtain a clearer view on the physical mechanisms underlying the light trapping we employ a simulation scheme that combines ray tracing with rigorous coupled wave analysis (RCWA). This combined simulation approach treats the light propagation inside the silicon absorber layer incoherently and averages out Fabry-Perot resonances, which otherwise would obscure characteristic humps in the absorption spectra that are directly related to light trapping effect of the diffraction gratings. We provide an in-depth explanation for the origin of these characteristic humps and their interrelationship with the silicon absorber thickness. A major benefit of this combined RCWA/ray tracing approach compared to the fully electromagnetic simulation methods RCWA and finite difference time domain (FDTD) is the more efficient use of computational power accompanied by a gain in simulation precision, in particular for cells with an absorber thicker than 10 ?m.

Wellenzohn, Markus; Hainberger, Rainer

2014-03-01

60

Fast electron accumulation and its mechanism in a harmonic trap under ultrahigh vacuum conditions  

SciTech Connect

We present here a fast and efficient electron accumulation in a multiring trap (MRT) in a superconducting solenoid of 5 T. More than 10{sup 10} electrons were accumulated within a fraction of a second for an electron beam in the range of 10{sup -7} A. The MRT was installed in a cryogenic bore tube cooled down to {approx}10 K. Electron accumulation as a function of various parameters such as the beam intensity, the MRT depth, and the MRT length was studied. We succeeded in extracting a consistent picture of the electron accumulation mechanisms, which consist of interactions of the incoming electron beam with the reflected beam and with the electrons trapped in the MRT.

Mohamed, T.; Imao, H.; Mohri, A. [Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Oshima, N. [National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 2, Tsukuba, Ibaraki 305-8568 (Japan); Yamazaki, Y. [Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Institute of Physics, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902 (Japan)

2011-03-15

61

Grover-like search via a Frenkel-exciton trapping mechanism  

NASA Astrophysics Data System (ADS)

We propose the physical implementation of a Grover-like search problem by means of Frenkel exciton trapping at a shallow isotopic impurity against a background of competing mechanisms. The search, culminating at the impurity molecule, designated the “winner” site, is marked by its enhanced interaction with acoustic phonons at low temperatures. The quantum search proceeds with the assistance of an oracle-like exciton-phonon interaction that addresses only the impurity site via the Dyson propagator within the Green’s function formalism. The optimum parameters of a graph lattice with long-range intersite interactions required to trap the exciton in the fastest time are determined, and estimates of error rates for the naphthalene-doped organic system are evaluated. We extend the analysis of the quantum search to a fluctuating long-range interacting cycle (LRIC) graph-lattice system.

Thilagam, A.

2010-03-01

62

Membrane-Based Gas Traps for Ammonia, Freon-21, and Water Systems to Simplify Ground Processing  

NASA Technical Reports Server (NTRS)

Gas traps are critical for the smooth operation of coolant loops because gas bubbles can cause loss of centrifugal pump prime, interference with sensor readings, inhibition of heat transfer, and blockage of passages to remote systems. Coolant loops are ubiquitous in space flight hardware, and thus there is a great need for this technology. Conventional gas traps will not function in micro-gravity due to the absence of buoyancy forces. Therefore, clever designs that make use of adhesion and momentum are required for adequate separation, preferable in a single pass. The gas traps currently used in water coolant loops on the International Space Station are composed of membrane tube sets in a shell. Each tube set is composed of a hydrophilic membrane (used for water transport and capture of bubbles) and a hydrophobic membrane (used for venting of air bubbles). For the hydrophilic membrane, there are two critical pressures, the pressure drop and the bubble pressure. The pressure drop is the decrease in system pressure across the gas trap. The bubble pressure is the pressure required for air bubbles to pass across the water filled membrane. A significant difference between these pressures is needed to ensure complete capture of air bubbles in a single pass. Bubbles trapped by the device adsorb on the hydrophobic membrane in the interior of the hydrophilic membrane tube. After adsorption, the air is vented due to a pressure drop of approximately 1 atmosphere across the membrane. For water systems, the air is vented to the ambient (cabin). Because water vapor can also transport across the hydrophobic membrane, it is critical that a minimum surface area is used to avoid excessive water loss (would like to have a closed loop for the coolant). The currently used gas traps only provide a difference in pressure drop and bubble pressure of 3-4 psid. This makes the gas traps susceptible to failure at high bubble loading and if gas venting is impaired. One mechanism for the latter is when particles adhere to the hydrophobic membrane, promoting formation of a water layer about it that can blind the membrane for gas transport (Figure 1). This mechanism is the most probable cause for observed failures with the existing design. The objective of this project was to devise a strategy for choosing new membrane materials (database development and procedure), redesign of the gas trap to mitigate blinding effects, and to develop a design that can be used in ammonia and Freon-21 coolant loops.

Ritchie, Stephen M. C.

2003-01-01

63

Correct trap type, size seen vital to energy efficiency  

Microsoft Academic Search

Steam losses and process inefficiency can result if steam traps are improperly sized or applied. Steam traps, which can be mechanical, thermostatic, or thermodynamic, should be selected on the basis of the pressure requirements, the minimum condensate load, turndown ratio, differential between steamline and return line pressure, and the trap design. Examples illustrate appropriate applications. A glossary of steam-trap terms

Warrock

1984-01-01

64

Threshold voltage instability mechanisms of nitride based charge trap flash memory--a review.  

PubMed

Technological scaling of charge trap device has become significantly more challenging due to two major physical limits revealed by International Technology Roadmap for Semiconductors (ITRS) 2011, i.e., (1) neighboring bit interference due to consistent shrinking in design floor space; (2) balancing act of ensuring sufficient number of electrons in shrinking storage layer to maintain stable threshold voltage (V(t)) against various V(t) instability mechanisms. Nitride based charge trap flash (CTF) is one of the better candidates to replace floating gate (FG) flash as the mainstream flash memory technology due to its inherent immunity to point defects and better device scalability. However, post cycled V(t) instability in the form of V(t) distribution shift and broadening of programmed/erased cells is still genuine reliability concerns for nitride based CTF devices. This is because the shift and broadening of V(t) distribution could degrade the operating window and thus caused premature failures of the devices. V(t) instability of nitride based CTF memory inevitably introduces statistical fluctuations in V(t) distribution of nitride based CTF which is detrimental to its long-term data retention performance. The scope of this review paper focuses on critical reliability challenges of future development of nitride based CTF development with emphasis on cell level V(t) instability mechanisms. Our review on recent findings of V(t) instability mechanisms are useful references for future development of nitride based CTF devices. PMID:24757947

Lee, Meng Chuan; Wong, Hirt Yong

2014-07-01

65

Magneto-mechanical resonant detection of superparamagnetic microbeads trapped by magnetic domain walls  

NASA Astrophysics Data System (ADS)

Manipulation of superparamagnetic (SPM) beads with magnetic domain walls (DWs) is of interest for lab-on-chip applications. DWs can trap SPM beads and tagged entities, enabling remote manipulation with nanoscale precision [1, 2]. Previously, we have demonstrated DW driven capture and transport of single microbeads at speeds approaching 1000 ?m/s [3]. Here, we demonstrate that the strong magnetostatic bead-DW binding leads to a unique magneto-mechanical resonance [4]. We show experimentally that this resonance can be used to distinguish bead populations based on their size, presenting a new mechanism for bead metrology. Moreover, the bead-DW interaction can be used to sense and characterize magnetic beads without the need for sensor surface functionalization. Exploiting the dual functionality of DWs as both bead carriers and sensors, we present an integrated device capable of high-speed transport and electrical sensing of the magneto-mechanical resonance of individual trapped beads.[4pt] [1] G. Vieira et al., Phys. Rev. Lett. 103, 128101 (2009).[0pt][2] M. Donolato et al., Adv. Mater. 22, 2706 (2010).[0pt] [3] E. Rapoport, G.S.D. Beach, Appl. Phys. Lett. in press.[0pt] [4] E. Rapoport, G.S.D. Beach, J. Appl. Phys. in press.

Rapoport, Elizabeth; Montana, Daniel; Beach, Geoffrey

2012-02-01

66

MECHANISMS OF DRY SO2 CONTROL PROCESSES  

EPA Science Inventory

The report discusses physical and chemical processes and reaction mechanisms for lime spray drying and dry injection of sodium compounds in dry flue gas desulfurization (FGD) processes. It includes: chemical reactions, physical changes, proposed reaction mechanisms and mathematic...

67

A Novel Method to Reduce Time Investment When Processing Videos from Camera Trap Studies  

PubMed Central

Camera traps have proven very useful in ecological, conservation and behavioral research. Camera traps non-invasively record presence and behavior of animals in their natural environment. Since the introduction of digital cameras, large amounts of data can be stored. Unfortunately, processing protocols did not evolve as fast as the technical capabilities of the cameras. We used camera traps to record videos of Eurasian beavers (Castor fiber). However, a large number of recordings did not contain the target species, but instead empty recordings or other species (together non-target recordings), making the removal of these recordings unacceptably time consuming. In this paper we propose a method to partially eliminate non-target recordings without having to watch the recordings, in order to reduce workload. Discrimination between recordings of target species and non-target recordings was based on detecting variation (changes in pixel values from frame to frame) in the recordings. Because of the size of the target species, we supposed that recordings with the target species contain on average much more movements than non-target recordings. Two different filter methods were tested and compared. We show that a partial discrimination can be made between target and non-target recordings based on variation in pixel values and that environmental conditions and filter methods influence the amount of non-target recordings that can be identified and discarded. By allowing a loss of 5% to 20% of recordings containing the target species, in ideal circumstances, 53% to 76% of non-target recordings can be identified and discarded. We conclude that adding an extra processing step in the camera trap protocol can result in large time savings. Since we are convinced that the use of camera traps will become increasingly important in the future, this filter method can benefit many researchers, using it in different contexts across the globe, on both videos and photographs.

Swinnen, Kristijn R. R.; Reijniers, Jonas; Breno, Matteo; Leirs, Herwig

2014-01-01

68

Dynamics of self-trapped hole processes in AgCl  

NASA Astrophysics Data System (ADS)

A set of phenomena involving the self-trapped hole (STH) in AgCl have been studied in crystals doped with hole sources, traps for holes and electrons and providers of cation vacancies. An energy barrier was demonstrated in the self-trapping process; its energy was related to appropriate phonon energies, and tunnelling appeared in the temperature range predicted by Mott and Stoneham. Migration of the STH can occur either by phonon-assisted hopping or by tunnelling. From the temperature dependences, one obtains the activation energy (0.062 eV), the trap depth (0.12 eV) and the temperature exponent for quantum migration (1.3). The structures and energetics of two centres involving an STH bound to a vacancy have been deduced. Also, it was shown that low-temperature capture of a hole by substitutional Fe2+ causes production of a Frenkel pair, as well as ultimately leading to formation of the (interstitial Fe3+) - (multivacancy) defect that was first characterized by Hayes et al.

Slifkin, L.

2001-03-01

69

Efficient scheme for multipartite entanglement and quantum information processing with trapped ions  

SciTech Connect

In this paper, based on the recent experiment by Roos et al. [Science 304, 1478 (2004)], a theoretical scheme is proposed to create the multipartite entanglement of many trapped ions and implement a two-qubit quantum phase gate between two ions in ion trap. In the scheme, the ion is illuminated by a single laser tuned to the first lower vibrational sideband. We also show that the scheme can be used to directly transfer information between two ions. The scheme has the advantage that it does not use the vibrational mode as the data bus and only requires a single resonant interaction. Thus the scheme is very simple and the quantum dynamics operation can be realized at a high speed. In view of the decoherence mechanism, the simplification for the entangled state preparation and experimental implementation of quantum logic operation may become crucial.

Yang Wenxing; Zhan Zhiming; Li Jiahua [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Center for Cold Atom Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China) and Guaduate School, Chinese Academy of Sciences, Beijing 100080 (China); School of Physics and Information Engineering, Jianghan University, Wuhan 430056 (China) and Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2005-12-15

70

Vacancy trapping mechanism for multiple hydrogen and helium in beryllium: a first-principles study  

NASA Astrophysics Data System (ADS)

The microscopic mechanism for H and He trapping by vacancy defects and bubble formation in a Be host lattice is investigated using first-principles calculations. A single He atom prefers to occupy a vacancy centre while H does not. He can segregate towards the vacancy from the interstitial site much more easily than H. Both H and He exhibit lower diffusion barriers from a remote interstitial to a vacancy with regard to their diffusion barriers inside a perfect Be solid. Up to five H or 12 He atoms can be accommodated into the monovacancy space, and the Be-He interaction is much weaker than Be-H. The physical origin for aggregation of multiple H or He atoms in a vacancy is further discussed. The strong tendency of H and He trapping at vacancies provides an explanation for why H and He bubbles were experimentally observed at vacancy defects in materials. We therefore argue that vacancies provide a primary nucleation site for bubbles of H and He gases inside Be materials.

Zhang, Pengbo; Zhao, Jijun; Wen, Bin

2012-03-01

71

Influence of trap location on the efficiency of trapping in dendrimers and regular hyperbranched polymers  

NASA Astrophysics Data System (ADS)

The trapping process in polymer systems constitutes a fundamental mechanism for various other dynamical processes taking place in these systems. In this paper, we study the trapping problem in two representative polymer networks, Cayley trees and Vicsek fractals, which separately model dendrimers and regular hyperbranched polymers. Our goal is to explore the impact of trap location on the efficiency of trapping in these two important polymer systems, with the efficiency being measured by the average trapping time (ATT) that is the average of source-to-trap mean first-passage time over every staring point in the whole networks. For Cayley trees, we derive an exact analytic formula for the ATT to an arbitrary trap node, based on which we further obtain the explicit expression of ATT for the case that the trap is uniformly distributed. For Vicsek fractals, we provide the closed-form solution for ATT to a peripheral node farthest from the central node, as well as the numerical solutions for the case when the trap is placed on other nodes. Moreover, we derive the exact formula for the ATT corresponding to the trapping problem when the trap has a uniform distribution over all nodes. Our results show that the influence of trap location on the trapping efficiency is completely different for the two polymer networks. In Cayley trees, the leading scaling of ATT increases with the shortest distance between the trap and the central node, implying that trap's position has an essential impact on the trapping efficiency; while in Vicsek fractals, the effect of location of the trap is negligible, since the dominant behavior of ATT is identical, respective of the location where the trap is placed. We also present that for all cases of trapping problems being studied, the trapping process is more efficient in Cayley trees than in Vicsek fractals. We demonstrate that all differences related to trapping in the two polymer systems are rooted in their underlying topological structures.

Lin, Yuan; Zhang, Zhongzhi

2013-03-01

72

Studies on Photoionization and Electron Trapping Process in Rare Earth Codoped Alkaline Earth Fluoride Crystals.  

NASA Astrophysics Data System (ADS)

In crystals with fluorite structure, such as CaF _2, SrF_2, and BaF_2, the process of photoionization of divalent rare earth ion (RE^{2+ }) impurities along with the trapping of electrons by different trivalent RE^{3+} ions have been investigated. It was found that the direct transition from a localized ground state of a rare earth to the conduction band states of the host has a negligible photoionization rate; and photoionization occurs through a localized excited state of the RE ion by thermal ionization or quantum tunneling, depending on the relative energy between the excited state and conduction band. The low energy of the exciton state of Eu ^{2+} in BaF_2 accounts for the lack of photoionization of Eu ^{2+} from the E_ {rm g} band. The Sm^ {3+} and Tm^{3+} demonstrated much higher trapping ability than Ce^{3+}. Electrons can be trapped not only by uncompensated RE^ {3+} but also by the charge compensated one. Relative trapping efficiency of Sm^ {3+} in both sites was measured in the BaF_2 crystal. Further investigation on the charge compensated Sm^{2+} ion, which is stable at low temperature, reveals that the interstitial fluoride compensator can substantially reduce the photoionization threshold, and quench the luminescence of Sm^ {2+} at lower temperature. It is also confirmed from Sm^{2+} absorption and emission spectra that Sm^ {2+}:F^{-} complex has C_{rm 3v} local symmetry in BaF_2. Ce^{3+} ions in cubic sites were reduced by X-ray irradiation at 77K in both SrF_2 and BaF_2 crystals for the first time ever. Ce^ {2+} will return to trivalent state after warming sample to room temperature. When a Ce:Na:CaF _2 crystal was irradiated with x-ray, the absorption spectra of both Ce^{3+} and Ce^{2+} showed no evidence of trapping of electron by Na^ {+} compensated Ce^{3+ }. In general, this work has shown that the ionization efficiency of RE^{2+} in fluorite lattice is affected by the energy of the self -trapped exciton state relative to the localized excited state of impurity and the proximity of charge compensator. It also demonstrates that the trapping cross section of RE ^{3+} strongly depends on the position of the charge compensator and the lattice size of host as well as the chemistry of the impurity itself.

Mou, Wanfeng

1995-01-01

73

Carrier trapping and current collapse mechanism in GaN metal-semiconductor field-effect transistors  

NASA Astrophysics Data System (ADS)

A mechanism for current collapse in GaN metal-semiconductor field-effect transistors is proposed, which assumes the existence of acceptor traps with multiple states in the band gap. Current collapse has been experimentally observed in the current-voltage characteristic after the drain voltage sweep had exceeded the threshold for impact ionization in a previous measurement. In the proposed model, electrons generated by impact ionization are captured by neutral acceptor trap states in the substrate located above the valence band. The charged trap states move to an energy level located near midgap, creating a positively charged depletion region in the channel, and causing current collapse. With increasing drain bias, the quasi-Fermi level approaches the charged trap states at the drain end of the gate, initiating detrapping of the electrons and restoring the current. The calculated results show good agreement with published experimental data.

Anwar, A. F. M.; Islam, Syed S.; Webster, Richard T.

2004-03-01

74

Neural mechanisms of spatiotemporal signal processing  

Microsoft Academic Search

We have studied the synaptic, dendritic, and network mechanisms of spatiotemporal signal processing underlying the computation of visual motion in the avian tectum. Such mechanisms are critical for information processing in all vertebrates, but have been difficult to elucidate in mammals because of anatomical limitations. We have therefore developed a chick tectal slice preparation, which has features that help us

2006-01-01

75

Collision Processes of Highly Charged Ions with Electrons Studied with an Electron Beam Ion Trap  

SciTech Connect

The electron beam ion trap in Tokyo (Tokyo-EBIT)is suitable for studying relativistic effects in the collisions of highly charged heavy ions with electrons because it can produce and trap very highly charged heavy ions which interact with a mono-energetic and unidirectional relativistic electron beam with an energy of up to 200 keV. Recently, we have been studying resonant processes in ionization and recombination by measuring the charge abundance inside the EBIT at the equilibrium. The abundance ratio between adjacent charge states varies slowly with the electron energy when there is no resonant process. However, when the electron energy coincides with the resonant energy at which ionization or recombination is enhanced, the abundance ratio can drastically change. Thus, the resonant processes can be studied by measuring the abundance ratio between adjacent ions as a function of electron beam energy. In this talk, recent progress for heavy ions with very high charge states up to He-like Bi{sup 81+}, is presented. For such ions, relativistic effects significantly affect the resonant processes. For example, the generalized Breit interaction (GBI) effect, which treats the retardation in the exchange of single virtual photon between the free and orbital electrons, has been clearly observed in the DR resonant strength in Li-like Bi{sup 80+}. Recently we have also found that the GBI effect plays an important role in the interference between non-resonant and resonant recombinations. Experimental results are presented in comparison with theoretical calculations.

Nakamura, Nobuyuki; Watanabe, Tsutomu; Ohtani, Shunsuke [Inst. for Laser Science, University of Electro-Communications, Tokyo 182-8585 (Japan); Kavanagh, Anthony P.; Currell, Fred J. [Queen's University Belfast, Belfast BT7 1NN (United Kingdom); Watanabe, Hirofumi [Chubu University, Aichi 487-8501 (Japan); Sakaue, Hiroyuki A.; Kato, Daiji [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Li Yueming [Institute of Applied Physics and Computational Mathematics, P.O.Box 8009, Beijing 100088 (China); Tong Xiaoming [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8577 (Japan)

2009-09-10

76

Collision Processes of Highly Charged Ions with Electrons Studied with an Electron Beam Ion Trap  

NASA Astrophysics Data System (ADS)

The electron beam ion trap in Tokyo (Tokyo-EBIT)[1] is suitable for studying relativistic effects in the collisions of highly charged heavy ions with electrons because it can produce and trap very highly charged heavy ions which interact with a mono-energetic and unidirectional relativistic electron beam with an energy of up to 200 keV. Recently, we have been studying resonant processes in ionization[2] and recombination[3] by measuring the charge abundance inside the EBIT at the equilibrium. The abundance ratio between adjacent charge states varies slowly with the electron energy when there is no resonant process. However, when the electron energy coincides with the resonant energy at which ionization or recombination is enhanced, the abundance ratio can drastically change. Thus, the resonant processes can be studied by measuring the abundance ratio between adjacent ions as a function of electron beam energy[4]. In this talk, recent progress for heavy ions with very high charge states up to He-like Bi81+, is presented. For such ions, relativistic effects significantly affect the resonant processes. For example, the generalized Breit interaction (GBI) effect, which treats the retardation in the exchange of single virtual photon between the free and orbital electrons, has been clearly observed in the DR resonant strength in Li-like Bi80+ [5]. Recently we have also found that the GBI effect plays an important role in the interference between non-resonant and resonant recombinations. Experimental results are presented in comparison with theoretical calculations.

Nakamura, Nobuyuki; Kavanagh, Anthony P.; Watanabe, Hirofumi; Sakaue, Hiroyuki A.; Li, Yueming; Kato, Daiji; Currell, Fred J.; Tong, Xiao-Ming; Watanabe, Tsutomu; Ohtani, Shunsuke

2009-09-01

77

Different mechanics of snap-trapping in the two closely related carnivorous plants Dionaea muscipula and Aldrovanda vesiculosa.  

PubMed

The carnivorous aquatic waterwheel plant (Aldrovanda vesiculosa L.) and the closely related terrestrial venus flytrap (Dionaea muscipula Sol. ex J. Ellis) both feature elaborate snap-traps, which shut after reception of an external mechanical stimulus by prey animals. Traditionally, Aldrovanda is considered as a miniature, aquatic Dionaea, an assumption which was already established by Charles Darwin. However, videos of snapping traps from both species suggest completely different closure mechanisms. Indeed, the well-described snapping mechanism in Dionaea comprises abrupt curvature inversion of the two trap lobes, while the closing movement in Aldrovanda involves deformation of the trap midrib but not of the lobes, which do not change curvature. In this paper, we present detailed mechanical models for these plants, which are based on the theory of thin solid membranes and explain this difference by showing that the fast snapping of Aldrovanda is due to kinematic amplification of the bending deformation of the midrib, while that of Dionaea unambiguously relies on the buckling instability that affects the two lobes. PMID:22181196

Poppinga, Simon; Joyeux, Marc

2011-10-01

78

Different mechanics of snap-trapping in the two closely related carnivorous plants Dionaea muscipula and Aldrovanda vesiculosa  

NASA Astrophysics Data System (ADS)

The carnivorous aquatic waterwheel plant (Aldrovanda vesiculosa L.) and the closely related terrestrial venus flytrap (Dionaea muscipula Sol. ex J. Ellis) both feature elaborate snap-traps, which shut after reception of an external mechanical stimulus by prey animals. Traditionally, Aldrovanda is considered as a miniature, aquatic Dionaea, an assumption which was already established by Charles Darwin. However, videos of snapping traps from both species suggest completely different closure mechanisms. Indeed, the well-described snapping mechanism in Dionaea comprises abrupt curvature inversion of the two trap lobes, while the closing movement in Aldrovanda involves deformation of the trap midrib but not of the lobes, which do not change curvature. In this paper, we present detailed mechanical models for these plants, which are based on the theory of thin solid membranes and explain this difference by showing that the fast snapping of Aldrovanda is due to kinematic amplification of the bending deformation of the midrib, while that of Dionaea unambiguously relies on the buckling instability that affects the two lobes.

Poppinga, Simon; Joyeux, Marc

2011-10-01

79

Synthesized by Mechanical Alloying Processing  

NASA Astrophysics Data System (ADS)

Nanostructured chalcopyrite CuAl0.5Ga0.5Te2 has been prepared by milling a mixture of reactants, copper, aluminum, gallium, and tellurium. The crystal structure, morphology, and composition of the prepared samples have been characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and transmission electron microscopy (TEM). X-ray diffraction has revealed the presence of the characteristic peaks of the chalcopyrite phase for the CuAl0.5Ga0.5Te2-milled powders. The crystallite size and internal strain have been evaluated by XRD patterns using the Williamson-Hall method. The average particle size decreases as the milling time is prolonged, while the lattice parameters and internal strain increase. The TEM confirmed the formation of CuAl0.5Ga0.5Tee nanoparticles. The bandgap has been found to increase from 1.42 eV up to 1.45 eV as the process time varies, respectively, from 60 min to 360 min.

Sehli, H.; Benabdeslem, M.; Benslim, N.; Bechiri, L.; Ayed, H.; Djekoun, A.; Boujnah, M.; Portier, X.; Ammar, S.; Lecoq, H.; Novack, S.; Decorse, P.

2014-06-01

80

The Electron Trap Mechanism of Luminescence in Sulphide and Silicate Phosphors  

Microsoft Academic Search

Phosphorescence and thermoluminescence emission from photoconducting impurity activated phosphors have been satisfactorily explained by the storage of electrons, freed from luminescence centres or other atoms of the solid, in metastable energy levels known as electron traps. Electrons escaping from these traps give rise to emission when they recombine with luminescence centres but there is a probability that they may be

G F J Garlick; A F Gibson

1948-01-01

81

The mechanisms of random trap fluctuation in metal oxide semiconductor field effect transistors  

NASA Astrophysics Data System (ADS)

An effect, called random trap fluctuation (RTF), is proposed to study the threshold voltage (Vth) fluctuation of metal oxide semiconductor field effect transistors (MOSFETs) under Fowler-Nordeim (FN) or hot carrier (HC) stress condition. Experiments have been demonstrated on n-channel MOSFETs, and it was found that not only the random dopant fluctuation (RDF) but also the stress-induced traps vary the Vth fluctuation. More importantly, the stress-induced trap barrier determines the Vth fluctuation. For devices after FN stress, Vth fluctuation is enhanced since the trap barrier regulates the transporting carriers. For devices after HC stress, Vth fluctuation is supressed since the carriers are backscattered into the channel by the trap barrier and fewer carriers with higher energy pass through the barrier. These results provide us a clear understanding on another source of Vth fluctuations in addition to the RDF as devices are further scaled.

Hsieh, E. R.; Chung, Steve S.

2012-11-01

82

Solute trapping of group III, IV, and V elements in silicon by an aperiodic stepwise growth mechanism  

NASA Astrophysics Data System (ADS)

With rapid solidification following pulsed laser melting, we have measured the dependence on interface orientation of the amount of solute trapping of several group III, IV, and V elements (As, Ga, Ge, In, Sb, Sn) in Si. The aperiodic stepwise growth model of Goldman and Aziz accurately fits both the velocity and orientation dependence of solute trapping of all these solutes except Ge. The success of the model implies a ledge structure for the crystal/melt interface and a step-flow mechanism for growth from the melt. In addition, we have observed an empirical inverse correlation between the two free paramters ('diffusive speeds') in this model and the equilibrium solute partition coefficient of a system. This correlation may be used to estimate values of these free paramters for other systems in which solute trapping has not or cannot be measured. The possible microscopic origin of such a correlationis discussed.

Reitano, Riccardo; Smith, Patrick M.; Aziz, Michael J.

1994-08-01

83

Compressional Trapped-Particle Mode : A New Generating Mechanism for ULF Waves  

NASA Astrophysics Data System (ADS)

A new plasma instability mechanism is proposed here for ULF magnetic pulsations in high beta magnetospheric plasmas. Here, beta is the ratio between plasma and magnetic pressures. In previous theoretical models,such pulsations are generated via either mirror mode or Alfven-ballooning mode(ABM) and their variations. While the mirror mode requires stringent high beta and/or strong anisotropy plasma conditions, the ABM is often stablized by the trapped-particle compression and takes the form of weaker instabilities via the drift-bounce resonances. Given high beta and sharp pressure gradients, however, we note that the plasma may form magnetic well, and, hence, the magnetic-gradient drift being opposite to the diamagnetic drift. A slow-magnetic compressional instability may then be excited; as noted by Rosenbluth two decades ago. We have, in the present work, further developed Rosenbluth's theory by including wave-partcile resonance and,assuming specific velocity distributions, derived a dispersion relation variationally. Both analytical and numerical results on the instability properties and the implications to observations such as the storm-time Pc5 pulsations will be discussed. Work supported by DoE and NSF Grants.

Chen, L.; Xu, B.

2002-12-01

84

Random Walk Theory of a Trap-Controlled Hopping Transport Process  

Microsoft Academic Search

A random walk theory of hopping motion in the presence of a periodic distribution of traps is presented. The solution of the continuous-time random walk equations is exact and valid for arbitrary intersite interactions and trap concentration. The treatment is shown to be equivalent to an exact solution of the master equation for this trapping problem. These interactions can be

H. Scher; C. H. Wu

1981-01-01

85

An extracellular matrix-based mechanism of rapid neutrophil extracellular trap formation in response to C. albicans1  

PubMed Central

The armament of neutrophil-mediated host defense against pathogens includes the extrusion of a lattice of DNA and microbicidal enzymes known as Neutrophil Extracellular Traps (NETs). The receptor:ligand interactions and intracellular signaling mechanisms responsible for elaborating NETs were determined for the response to Candida albicans. Since the host response of extravasated neutrophils to mycotic infections within tissues necessitates contact with ECM, this study also identified a novel and significant regulatory role for the ubiquitous matrix component fibronectin (Fn) in NET release. We report that recognition of purified fungal pathogen-associated molecular pattern ?-glucan by human neutrophils causes rapid (? 30 mins) homotypic aggregation and NET release by a mechanism that requires Fn. Alone, immobilized ?-glucan induces reactive oxygen species (ROS) production but not NET release, whereas in the context of Fn, ROS production is suppressed and NETs are extruded. NET release to Fn + ?-glucan is robust, accounting for 17.2 ± 3.4% of total DNA in the cell population. Release is dependent on ?-glucan recognition by CR3 (CD11b/CD18), but not Dectin-1, or ROS. The process of NET release included filling of intracellular vesicles with nuclear material that was eventually extruded. We identify a role for ERK in homotypic aggregation and NET release. NET formation to C. albicans hyphae was also found to depend on ?-glucan recognition by CR3, require Fn and ERK but not ROS, and result in hyphal destruction. We report a new regulatory mechanism of NETosis in which the extracellular matrix is a key component of the rapid anti-fungal response.

Byrd, Angel S.; O'Brien, Xian M.; Johnson, Courtney M.; Lavigne, Liz M.; Reichner, Jonathan S.

2013-01-01

86

An extracellular matrix-based mechanism of rapid neutrophil extracellular trap formation in response to Candida albicans.  

PubMed

The armament of neutrophil-mediated host defense against pathogens includes the extrusion of a lattice of DNA and microbicidal enzymes known as neutrophil extracellular traps (NETs). The receptor/ligand interactions and intracellular signaling mechanisms responsible for elaborating NETs were determined for the response to Candida albicans. Because the host response of extravasated neutrophils to mycotic infections within tissues necessitates contact with extracellular matrix, this study also identified a novel and significant regulatory role for the ubiquitous matrix component fibronectin (Fn) in NET release. We report that recognition of purified fungal pathogen-associated molecular pattern ?-glucan by human neutrophils causes rapid (? 30 min) homotypic aggregation and NET release by a mechanism that requires Fn. Alone, immobilized ?-glucan induces reactive oxygen species (ROS) production but not NET release, whereas in the context of Fn, ROS production is suppressed and NETs are extruded. NET release to Fn with ?-glucan is robust, accounting for 17.2 ± 3.4% of total DNA in the cell population. Release is dependent on ?-glucan recognition by complement receptor 3 (CD11b/CD18), but not Dectin-1, or ROS. The process of NET release included filling of intracellular vesicles with nuclear material that was eventually extruded. We identify a role for ERK in homotypic aggregation and NET release. NET formation to C. albicans hyphae was also found to depend on ?-glucan recognition by complement receptor 3, require Fn and ERK but not ROS, and result in hyphal destruction. We report a new regulatory mechanism of NETosis in which the extracellular matrix is a key component of the rapid antifungal response. PMID:23509360

Byrd, Angel S; O'Brien, Xian M; Johnson, Courtney M; Lavigne, Liz M; Reichner, Jonathan S

2013-04-15

87

Characterisation of FOGs in grease trap waste from the processing of chickens in Thailand.  

PubMed

Industrial firms that kill and process chickens generate wastewater that contains fat, oil, and grease (FOG). The FOGs are located in the fatty waste that is collected by floatation in grease traps. Chemical and physical characterisation of FOGs would provide useful information that would help in the development of methods designed to decrease the extent of pollution caused by disposal of the waste and to utilise commercially some of its lipid constituents. Employing these methods would enhance the profitability and competitive potential of these commercial organisations. Samples of grease trap waste from 14 firms in central Thailand have been examined. Due to the very different schemes of waste management employed by these firms, the physical appearance of their fatty wastes showed considerable variation. The chemical and physical properties of the FOGs present in these wastes showed considerable variation also. Large amounts of free fatty acids (10-70% as oleic acid) were detected in most of the 14 wastes and palmitic, cis-9-oleic, cis,cis-9,12-linoleic, stearic, and palmitoleic acids were the predominant species of free and esterified acids. Most of the FOGs were solid at temperatures below 40 °C. Many of them contained traces of heavy metals (Cu and Pb) and some contained traces of the pesticides dimethoate and cypermethrin. The content of these potentially hazardous substances would have to be considered very carefully before discarding the fatty wastes and during the development of methods designed to isolate their potentially profitable lipid constituents. PMID:24095036

Nitayapat, Nuttakan; Chitprasert, Pakamon

2014-06-01

88

Processing of strong flux trapping high T(subc) oxide superconductors: Center director's discretionary fund  

NASA Technical Reports Server (NTRS)

Magnetic suspension effect was first observed in samples of YBa2Cu3O7/AgO(Y-123/AgO) composites. Magnetization measurements of these samples show a much larger hysteresis which corresponds to a large critical current density. In addition to the Y-123AgO composites, recently similar suspension effects in other RE-123/AgO, where RE stands for rare-Earth elements, were also observed. Some samples exhibit even stronger flux pinning than that of the Y-123/AgO sample. An interesting observation was that in order to form the composite which exhibits strong flux trapping effect the sintering temperature depends on the particular RE-123 compound used. The paper presents the detailed processing conditions for the formation of these RE-123/AgO composites, as well as the magnetization and critical field data.

Wu, M. K.; Higgins, C. A.; Leong, P. T.; Chou, H.; Loo, B. H.; Curreri, P. A.; Peters, P. N.; Sisk, R. C.; Huang, C. Y.; Shapira, Y.

1989-01-01

89

Unfaulting mechanism of trapped self-interstitial atom clusters in bcc Fe: A kinetic study based on the potential energy landscape  

SciTech Connect

We report on the complete unfaulting mechanism of a trapped self-interstitial atom cluster in the form of a nonparallel configuration (NPC), investigated using the autonomous basin climbing (ABC) method. A detailed set of transition state atomic trajectories in the unfaulting process from the trapped to the mobile glide <111> configuration and the corresponding potential energy landscape were identified. The breaking of the initial ring structure of the three trimers on (111) planes followed by the rotation of the <111> crowdion in the NPC are the main rate limiting processes of the unfaulting mechanism. The effective activation barrier in the transition from the NPC to the glide <111> configuration was calculated by combining the ABC and kinetic Monte Carlo methods and was further benchmarked against molecular dynamics (MD) simulations. The effective activation barrier was found as 0.82 eV; smaller than its previously reported value of 1.68 eV. The ABC method was confirmed to be more efficient than MD, especially for the defect structure evolution processes associated with high barriers and at low temperatures.

Fan Yue; Kushima, Akihiro; Yildiz, Bilge [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States)

2010-03-01

90

Ionic motion in polypyrrole-cellulose composites: trap release mechanism during potentiostatic reduction.  

PubMed

This work investigates the movement of anions during potentiostatic controlled reduction of novel composite materials consisting of high surface area cellulose substrates, extracted from the Cladophora sp. algae, coated with thin ( approximately 50 nm) layers of the intrinsically conducting polymer (ICP) polypyrrole. The coating was achieved by chemical polymerization of pyrrole on the cellulose fibers with iron(III) chloride and phosphomolybdic acid, respectively. The composites are in the form of paper sheets and can be directly immersed into an electrolyte solution for ion absorption/desorption. The motion of glutamate and aspartate anions during cathodic polarization was investigated as a function of preceding anodic polarization at various potentials. The composite was found to exhibit memory effect as the response to a cathodic polarization of constant magnitude produced different responses depending on the magnitude of the preceding anodic potential. After the application of a cathodic potential to the composite, the reduction current curvesgenerated by anions leaving the compositewere found to initially increase in magnitude followed by a monotonic decay. A similar response has not been described and analyzed for electrochemical reduction of anion containing ICP materials earlier. A theoretical model was developed to aid the analysis of the experimental data. The model accounts for both freely mobile anions and anions that may be temporarily trapped in a contracting PPy network during cathodic polarization. By fitting the recorded reduction current curves to this model, detailed information about the ionic movement in the composite could be obtained, which may be used to further optimize the materials properties of conducting polymer systems aimed for specific electrochemical ion exchange processes. PMID:19338363

Strømme, Maria; Frenning, Göran; Razaq, Aamir; Gelin, Kristina; Nyholm, Leif; Mihranyan, Albert

2009-04-01

91

Linear chains in a monolithic symmetric trap for quantum information processing  

NASA Astrophysics Data System (ADS)

Linear ion chains are being used [1] to simulate quantum magnet Ising interactions, phase transitions, and spin frustrations. We will present results for trapping linear ion chains in a monolithic two-level trap that utilizes the flexibility, complexity and scalability provided by VLSI silicon microfabrication. This trap provides optimized features and dimensions for trapping equally spaced ion chains while minimizing light scattering and exposed dielectrics that sometimes limit surface electrode ion traps. The ions are trapped symmetrically between two electrode layers. This geometry provides a strong pseudopotential well and radial field symmetry, resulting in stable ion mode frequencies and chains. [4pt] [1] K. Kim, et al, Phys. Rev. Lett. 103, 120502 (2009)

Shaikh, Fayaz; Slusher, Richart

2012-06-01

92

Structure and dynamics of ion clusters in linear octupole traps: Phase diagrams, chirality, and melting mechanisms  

SciTech Connect

The stable structures and melting dynamics of clusters of identical ions bound by linear octupole radiofrequency traps are theoretically investigated by global optimization methods and molecular dynamics simulations. By varying the cluster sizes in the range of 10-1000 ions and the extent of trap anisotropy by more than one order of magnitude, we find a broad variety of stable structures based on multiple rings at small sizes evolving into tubular geometries at large sizes. The binding energy of these clusters is well represented by two contributions arising from isotropic linear and octupolar traps. The structures generally exhibit strong size effects, and chiral arrangements spontaneously emerge in many crystals. Sufficiently large clusters form nested, coaxial tubes with different thermal stabilities. As in isotropic octupolar clusters, the inner tubes melt at temperatures that are lower than the overall melting point.

Yurtsever, E.; Onal, E. D.; Calvo, F. [Koc University, Rumelifeneriyolu, Sariyer, Istanbul TR-34450 (Turkey); LASIM, Universite de Lyon and CNRS UMR 5579, 43 Bd du 11 Novembre 1918, FR-69622 Villeurbanne Cedex (France)

2011-05-15

93

Meanings, Mechanisms, and Measures of Holistic Processing  

PubMed Central

Few concepts are more central to the study of face recognition than holistic processing. Progress toward understanding holistic processing is challenging because the term “holistic” has many meanings, with different researchers addressing different mechanisms and favoring different measures. While in principle the use of different measures should provide converging evidence for a common theoretical construct, convergence has been slow to emerge. We explore why this is the case. One challenge is that “holistic processing” is often used to describe both a theoretical construct and a measured effect, which may not have a one-to-one mapping. Progress requires more than greater precision in terminology regarding different measures of holistic processing or different hypothesized mechanisms of holistic processing. Researchers also need to be explicit about what meaning of holistic processing they are investigating so that it is clear whether different researchers are describing the same phenomenon or not. Face recognition differs from object recognition, and not all meanings of holistic processing are equally suited to help us understand that important difference.

Richler, Jennifer J.; Palmeri, Thomas J.; Gauthier, Isabel

2012-01-01

94

A model for the trap-assisted tunneling mechanism in diffused n-p and implanted n(+)-p HgCdTe photodiodes  

NASA Technical Reports Server (NTRS)

This paper presents a theoretical model for the trap-assisted tunneling process in diffused n-on-p and implanted n(+)-on-p HgCdTe photodiodes. The model describes the connection between the leakage current associated with the traps and the trap characteristics: concentration, energy level, and capture cross sections. It is observed that the above two types of diodes differ the voltage dependence of the trap-assisted tunneling current and dynamic resistance. The model takes this difference into account and offers an explanation of the phenomenon. The good fit between measured and calculated dc characteristics of the photodiodes supports the validity of the model.

Rosenfeld, David; Bahir, Gad

1992-01-01

95

Credit Traps  

Microsoft Academic Search

This paper studies the limitations of monetary policy transmission within a credit channel frame- work. We show that, under certain circumstances, the credit channel transmission mechanism fails in that liquidity injections by the central bank into the banking sector are hoarded and not lent out. We use the term ‘credit traps’ to describe such situations and show how they can

Efraim Benmelech; Nittai K. Bergman

2010-01-01

96

Trapping rate dependence on the trap size in one dimension  

NASA Astrophysics Data System (ADS)

The one-dimensional trapping problem is revisited with emphasis on the role of the size of the traps. It is discovered that the process rate is dependent on the trap size whenever the traps are correlated. Qualitatively, the effect is manifested as a slowdown or an acceleration of trapping with an enlargement of traps, according to trap attraction or repulsion, respectively. The dependence is studied in detail for a particular model. (c) 1995 The American Physical Society

Bogachev, L. V.; Makhnovskii, Yu. A.; Berezhkovskii, A. M.

1995-12-01

97

Fluid mechanics mechanisms in the stall process of helicopters  

NASA Technical Reports Server (NTRS)

Recent experimental results from airfoils in the Mach number, Reynolds number, or reduced frequency ranges typical of helicopter rotor blades have identified the most influential flow mechanisms in the dynamic stall process. The importance of secondary shed vortices, downstream wake action, and the flow in the separated region is generally acknowledged but poorly understood. By means of surface pressure cross-correlations and flow field measurements in static stall, several new hypotheses have been generated. It is proposed that vortex shedding may be caused by acoustic disturbances propagating forward in the lower (pressure) surface boundary layer, that wake closure is a misnomer, and that the shed vortex leaves a trail of vorticity that forms a turbulent free shear layer. The known dynamic stall flow mechanisms are reviewed and the potential importance of recently proposed and hypothetical flow phenomena with respect to helicopter blade aeroelastic response are assessed.

Young, W. H., Jr.

1981-01-01

98

Random walk theory of a trap-controlled hopping transport process.  

PubMed

A random walk theory of hopping motion in the presence of a periodic distribution of traps is presented. The solution of the continuous-time random walk equations is exact and valid for arbitrary intersite interactions and trap concentration. The treatment is shown to be equivalent to an exact solution of the master equation for this trapping problem. These interactions can be a general function of electric field and are not restricted to nearest neighbors. In particular, with the inclusion of trap-to-trap interactions, as well as trap-to-host interactions, an exact treatment of the change from one hopping channel to another has been obtained. The trap-modulated propagator has been derived in terms of a type of Green's function that is introduced. The results are specialized to spatial moments of the propagator, from which expressions for the drift velocity and diffusion coefficient are obtained. Numerical results for the drift velocity are presented and shown to account for the change in hopping channels in recent transport measurements in mixed molecularly doped polymers. PMID:16592944

Scher, H; Wu, C H

1981-01-01

99

Isolated, slowly evolving, and dynamical trapping horizons: Geometry and mechanics from surface deformations  

SciTech Connect

We study the geometry and dynamics of both isolated and dynamical trapping horizons by considering the allowed variations of their foliating two-surfaces. This provides a common framework that may be used to consider both their possible evolutions and their deformations as well as derive the well-known flux laws. Using this framework, we unify much of what is already known about these objects as well as derive some new results. In particular we characterize and study the 'almost isolated' trapping horizons known as slowly evolving horizons. It is for these horizons that a dynamical first law holds and this is analogous and closely related to the Hawking-Hartle formula for event horizons.

Booth, Ivan; Fairhurst, Stephen [Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, A1C 5S7 (Canada); Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, 53201 (United States)

2007-04-15

100

Electron trapping center and SnO2-doping mechanism of indium tin oxide  

Microsoft Academic Search

.   Indium tin oxide (ITO) and Er3+-doped ITO powders were prepared by a conventional ceramic method. The density of ITO powders and optical absorption spectra\\u000a of Er3+ ions in Er3+-doped ITO were measured as a function of the SnO2 doping level. The results obtained were discussed in terms of the trapping center for immobile electrons in ITO. Observed\\u000a densities of

T. Omata; H. Fujiwara; S. Otsuka-Yao-Matsuo; N. Ono

2000-01-01

101

Processing and mechanical characterization of alumina laminates  

Microsoft Academic Search

Single-phase ceramics that combine property gradients or steps in monolithic bodies are sought as alternatives to ceramic composites made of dissimilar materials. This work describes novel processing methods to produce stepped-density (or laminated) alumina single-phase bodies that maintain their mechanical integrity. One arrangement consists of a stiff, dense bulk material with a thin, flaw tolerant, porous exterior layer. Another configuration

John K. Montgomery

2002-01-01

102

Multiple scale physical and numerical modeling for improved understanding of mechanisms of trapping and leakage of CO2 in deep geologic formations  

NASA Astrophysics Data System (ADS)

The fundamental processes associated with trapping and leakage of CO2 in deep geologic formations are complex. Formation heterogeneity manifested at all scales is expected to affect capillary and dissolution trapping and leakage of gaseous CO2 to the shallow subsurface. Research is underway to improve our fundamental understanding of trapping and leakage. This research involves experimentation in multiple scales and modeling focusing on effects of formation heterogeneity. The primary hypothesis that drives this research is that when the effects of heterogeneity on entrapment and leakage are understood, it will be possible to design more effective and safe storage schemes. Even though field investigations have some value in understanding issues related to large scale behavior and performance assessment, a fundamental understanding of how the heterogeneity affects trapping is difficult or impossible to obtain in field settings. Factors that contribute to these difficulties are the inability to fully characterize the formation heterogeneity at all scales of interest and lack of experimental control at very high depths. Intermediate scale physical model testing provides an attractive alternative to investigate these processes in the laboratory. Heterogeneities can be designed using soils with known properties in test tanks and the experiments can be conducted under controlled conditions to obtain accurate data. Conducting laboratory experiments under ambient pressure and temperature conditions to understand the processes that occur in deep formations poses many challenges. This research attempts to address such challenges and demonstrates how this testing approach could be used to generate useful data. The experiments involve the use of test systems of hierarchy of scales from small to intermediate scale tanks (~ 5 m) and long columns (~ 4.5 m). These experiments use surrogate fluids to investigate both capillary and solubility trapping in homogeneous and heterogeneous systems. A traversing x-ray scanning system is used to monitor the advancement of the plume during and after injection and to measure the residual (trapped) CO2 saturation. Dissolution of a surrogate non-wetting fluid in a surrogate wetting fluid is analyzed in small and large tanks. We test the numerical models that are capable of simulating two-phase flow and density driven flow as a result of dissolution by using the experimental data. Verified models are used to further evaluate the effect of capillary and solubility trapping in complex heterogeneous environments. During leakage, under different pressure and temperature conditions, dissolved CO2 may come back out of solution (exsolve), but the fundamental triggering mechanisms of this process in porous media are not yet well understood. An extensive series of column experiments has been conducted to investigate the factors that control the rates of CO2 gas bubble nucleation, growth, and migration. Results indicate that the saturation pressure (i.e. the amount of CO2 dissolved into the injected water) and heterogeneity both significantly affect the gas formation and migration, whereas the injection rate has less of an effect. These column experiments will soon be upscaled to an intermediate-scale two-dimensional tank to investigate the behaviour of the CO2 gas-water-soil system in more complex geological environments.

Illangasekare, T.; Plampin, M.; Trevisan, L.; Agartan, E.; Mori, H.; Sakaki, T.; Cihan, A.; Birkholzer, J.; Zhou, Q.; Pawar, R.; Zyvoloski, G.

2012-04-01

103

Influence of interlayer trapping and detrapping mechanisms on the electrical characterization of hafnium oxide/silicon nitride stacks on silicon  

NASA Astrophysics Data System (ADS)

Al/HfO2/SiNx:H/n-Si metal-insulator-semiconductor capacitors have been studied by electrical characterization. Films of silicon nitride were directly grown on n-type silicon substrates by electron cyclotron resonance assisted chemical vapor deposition. Silicon nitride thickness was varied from 3 to 6.6 nm. Afterwards, 12 nm thick hafnium oxide films were deposited by the high-pressure sputtering approach. Interface quality was determined by using current-voltage, capacitance-voltage, deep-level transient spectroscopy (DLTS), conductance transients, and flatband voltage transient techniques. Leakage currents followed the Poole-Frenkel emission model in all cases. According to the simultaneous measurement of the high and low frequency capacitance voltage curves, the interface trap density obtained for all the samples is in the 1011 cm-2 eV-1 range. However, a significant increase in this density of about two orders of magnitude was obtained by DLTS for the thinnest silicon nitride interfacial layers. In this work we probe that this increase is an artifact that must be attributed to traps existing at the HfO2/SiNx:H intralayer interface. These traps are more easily charged or discharged as this interface comes near to the substrate, that is, as thinner the SiNx:H interface layer is. The trapping/detrapping mechanism increases the capacitance transient and, in consequence, the DLTS measurements have contributions not only from the insulator/substrate interface but also from the HfO2/SiNx:H intralayer interface.

García, H.; Dueñas, S.; Castán, H.; Gómez, A.; Bailón, L.; Toledano-Luque, M.; Del Prado, A.; Mártil, I.; González-Díaz, G.

2008-11-01

104

Spectroscopic studies of the charge breeding process in high current electron beam ion traps  

NASA Astrophysics Data System (ADS)

Electron beam ion traps (EBITs) are a new tool for charge breeding of rare isotope beams. The ionization efficiency of a new high current EBIT recently built at the MPIK was investigated spectroscopically during its commissioning phase.

Baumann, T. M.; Crespo López-Urrutia, J. R.; Schwarz, S.; Lapierre, A.; Bollen, G.; Kester, O.; Dilling, J.; Ullrich, J.

2012-11-01

105

Constraints on Transport and Emplacement Mechanisms of Labile Fractions in Lunar Cold Traps  

NASA Technical Reports Server (NTRS)

Sustaining the scientific exploration of the Solar System will require a significant proportion of the necessary fuels and propellants, as well as other bulk commodities, to be produced from local raw materials [1]. The viability of mineral production depends on the ability to locate and characterize mineable deposits of the necessary feedstocks. This requires, among other things, a workable understanding of the mechanisms by which such deposits form, which is the subject of Economic Geology. Multiple deposition scenarios are possible for labile materials on the Moon. This paper suggests labile fractions moved diffusely through space; deposits may grow richer with depth until low porosity rock; lateral transport is likely to have occurred with the regolith, at least for short distances; crystalline ice may not exist; the constituent phases could be extremely complex. At present we can constrain the sources only mildly; once on the Moon, the transport mechanisms inherently mix and therefore obscure the origins. However, the importance of expanding our understanding of ore-forming processes on the Moon behooves us to make the attempt. Thus begins a time of new inquiry for Economic Geology.

Rickman, D.; Gertsch, L.

2014-01-01

106

Superexchange coupling mechanisms for electron transfer processes  

NASA Astrophysics Data System (ADS)

Electron transfer matrix elements for electron exchange between various pairs of transition metal complexes in close contact have been calculated and analyzed for a variety of approach geometries for the two reactants. The coupling between the nominal metal ion donor/acceptor sites is achieved by superexchange of the hole type arising from ligand-to-metal charge transfer (LMCT), the dominant ligand-field interaction for the electron-donor ligands considered (H sub 2 O, NH sub 3, the cyclopentadienide anion). The pronounced variations of H sub if with geometry are not correlated with the separation distance of the metal ions (between which the direct overlap is negligible) and span the range from non-adiabatic to strongly adiabatic electronic coupling. The values for metallocene/metallocinium redox pairs bracket recently reported experimental values. Analysis of the results using the method of corresponding orbitals demonstrates the validity of an effective 1-electron model for the electron transfer process to within about 10 percent for the class of systems considered. A higher-order superexchange mechanism was encountered for the Co(NH sub 3) sub 6 (2+/3+) exchange process, in which the LMCT-driven hole-transport mechanism couples excited local states of the metal ions, which in turn are connected to the corresponding ground states by spin-orbit mixing. This mechanism yields on electronic transmission factor within two orders of magnitude of unity.

Newton, M. D.

107

Steam trap  

Microsoft Academic Search

A steam trap is described for expelling large quantities of condensate held at low pressure and for self locking at pressures above a predetermined pressure. The process comprises: a body including an input port, and an output port; a chamber within the body communicating with the output port. The chamber has sidewalls and an annular shoulder adjacent the sidewalls; the

Kline

1987-01-01

108

Increased biogas production at wastewater treatment plants through co-digestion of sewage sludge with grease trap sludge from a meat processing plant  

Microsoft Academic Search

The feasibility of co-digesting grease trap sludge from a meat-processing plant and sewage sludge was studied in batch and reactor experiments at 35°C. Grease trap sludge had high methane production potential (918m3\\/tVSadded), but methane production started slowly. When mixed with sewage sludge, methane production started immediately and the potential increased with increasing grease trap sludge content. Semi-continuous co-digestion of the

S. Luostarinen; S. Luste; M. Sillanpää

2009-01-01

109

Quantum mechanical Hamiltonian models of discrete processes  

SciTech Connect

Here the results of other work on quantum mechanical Hamiltonian models of Turing machines are extended to include any discrete process T on a countably infinite set A. The models are constructed here by use of scattering phase shifts from successive scatterers to turn on successive step interactions. Also a locality requirement is imposed. The construction is done by first associating with each process T a model quantum system M with associated Hilbert space H/sub M/ and step operator U/sub T/. Since U/sub T/ is not unitary in general, M, H/sub M/, and U/sub T/ are extended into a (continuous time) Hamiltonian model on a larger space which satisfies the locality requirement. The construction is compared with the minimal unitary dilation of U/sub T/. It is seen that the model constructed here is larger than the minimal one. However, the minimal one does not satisfy the locality requirement.

Benioff, P.

1981-03-01

110

Photoexcitation, trapping, and recombination processes of the F-type centers in lasing MgO microcrystals  

Microsoft Academic Search

We report results of a detailed temperature dependence of photoluminescence (PL) decay time and continuous emission properties of the F and F+ centers in recently reported lasing MgO microcrystals [T. Uchino and D. Okutsu, Phys. Rev. Lett.PRLTAO0031-900710.1103\\/PhysRevLett.101.117401 101, 117401 (2008)]. Thermally induced ionization and carrier trapping play a vital role in the entire emission processes of the F-type centers, especially

Y. Uenaka; T. Uchino

2011-01-01

111

Influence of the inductor shape, and the magnetization processes on a trapped magnetic flux in a superconducting bulk  

NASA Astrophysics Data System (ADS)

In this paper, we study the form of the inductor for producing a magnetic field in a superconductor bulk by using a method of PFM (Pulsed Field Magnetization). We tested two inductors: vortex coil and system of three coils, where we found the best results with the system of three coils. After that, we presented two processes for trapping a magnetic field in the bulk: direct magnetization and successive magnetization where we found similar results.

Gony, B.; Linares, R.; Lin, Q.; Berger, K.; Douine, B.; Leveque, J.

2014-08-01

112

Characterization of carrier recombination and trapping processes in proton irradiated silicon by microwave absorption transients  

Microsoft Academic Search

Carrier lifetime variations dependent on proton irradiation with fluences in the range from 5×1012 to 1015cm?2 were investigated in high resistivity oxygenated silicon wafers and pad detectors. The fast recombination and slow trapping constituents within recombination transients have been distinguished by combining analyses of the excess carrier decay dependence on the excitation intensity, bias illumination and temperature, measured using the

E. Gaubas; J. Vaitkus; G. Niaura; J. Härkönen; E. Tuovinen; P. Luukka; E. Fretwurst

2005-01-01

113

Investigating the rp-process with the Canadian Penning trap mass spectrometer  

Microsoft Academic Search

The Canadian Penning trap (CPT) mass spectrometer at the Argonne National Laboratory makes precise mass measurements of nuclides with short half-lives. Since the previous ENAM conference, many significant modifications to the apparatus were implemented to improve both the precision and efficiency of measurement, and now more than 60 radioactive isotopes have been measured with half-lives as short as one second

J. A. Clark; R. C. Barber; B. Blank; C. Boudreau; F. Buchinger; J. E. Crawford; J. P. Greene; S. Gulick; J. C. Hardy; A. A. Hecht; A. Heinz; J. K. P. Lee; A. F. Levand; B. F. Lundgren; R. B. Moore; G. Savard; N. D. Scielzo; D. Seweryniak; K. S. Sharma; G. D. Sprouse; W. Trimble; J. Vaz; J. C. Wang; Y. Wang; B. J. Zabransky; Z. Zhou

2005-01-01

114

A high-speed vertical optical trap for the mechanical testing of living cells at piconewton forces  

SciTech Connect

Although atomic force microscopy is often the method of choice to probe the mechanical response of (sub)micrometer sized biomaterials, the lowest force that can be reliably controlled is limited to ?0.1 nN. For soft biological samples, like cells, such forces can already lead to a strain large enough to enter the non-elastic deformation regime. To be able to investigate the response of single cells at lower forces we developed a vertical optical trap. The force can be controlled down to single piconewtons and most of the advantages of atomic force microscopy are maintained, such as the symmetrical application of forces at a wide range of loading rates. Typical consequences of moving the focus in the vertical direction, like the interferometric effect between the bead and the coverslip and a shift of focus, were quantified and found to have negligible effects on our measurements. With a fast responding force feedback loop we can achieve deformation rates as high as 50 ?m/s, which allow the investigation of the elastic and viscous components of very soft samples. The potential of the vertical optical trap is demonstrated by measuring the linearity of the response of single cells at very low forces and a high bandwidth of deformation rates.

Bodensiek, Kai, E-mail: bodensiek@physik3.gwdg.de; Li, Weixing [III. Physikalisches Institut, Georg-August-Universität, Göttingen (Germany)] [III. Physikalisches Institut, Georg-August-Universität, Göttingen (Germany); Sánchez, Paula; Nawaz, Schanila; Schaap, Iwan A. T. [III. Physikalisches Institut, Georg-August-Universität, Göttingen (Germany) [III. Physikalisches Institut, Georg-August-Universität, Göttingen (Germany); Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen (Germany)

2013-11-15

115

The effect of trapped hydrogen on mechanical behavior of Ni{sub 3}(Si, Ti) intermetallic compound  

SciTech Connect

The effect of residual hydrogen on mechanical properties and fracture behavior of Ni{sub 3}(Si, Ti) single crystals and polycrystals is investigated by tensile tests, using materials with a low level (< 0.5 mass ppm) and high level ({approximately} 2 mass ppm) hydrogen content, and also with and without a trace amount of boron (50 ppm). Furthermore, the effect of pre-plastic deformation on these phenomena is investigated. Tensile elongation and fracture mode of the Ni{sub 3}(Si, Ti) single crystals are primarily insensitive to the hydrogen content. The tensile elongation of the Ni{sub 3}(Si, Ti) polycrystals are markedly reduced by a high level of hydrogen content, and associated fractography shows a mainly brittle intergranular fracture pattern. However, boron-doped Ni{sub 3}(Si, Ti) polycrystals are not embrittled by a high level of hydrogen content. The tensile elongation of pre-deformed and then hydrogen-charged Ni{sub 3}(Si, Ti) polycrystals increases with increasing pre-deformation although absorbed hydrogen content increases. It is suggested that residual hydrogen at {approximately} 2 mass ppm is enough to embrittle the Ni{sub 3}(Si, Ti) alloys when the hydrogen is trapped at grain boundaries, but, ineffective when the hydrogen is distributed within the grain interior or trapped at dislocations. Also, it is suggested that boron competes for site occupation with the hydrogen, and/or directly enhances grain boundary cohesion, thereby resulting in the effect of suppressing hydrogen embrittlement.

Ma, C.L.; Takasugi, T.; Hanada, S. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research] [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

1996-04-01

116

Unbinding of Semi-flexible Bio-polymers from Columnar Traps: An Exactly Solvable Problem of Statistical Mechanics  

NASA Astrophysics Data System (ADS)

We elucidate unbinding of long semi-flexible bio-polymers from long line-like attractive potential wells (columnar traps). This phase transition has been observed in the experiments with DNA molecules adsorbed on micro-structured supported cationic lipid membranes. It provides a new way to stretch (linearize) single DNA coils [Hochrein, Leierseder, Golubovic, and Raedler, Physical Review E (2007)]. We reveal that this phase transition is an exactly solvable problem of statistical mechanics. Our theory is based on mapping this nontrivial problem onto a novel class of directed random walks. This DNA unbinding transition turns out to have a unique thermodynamic character: It is of the second order however with very weakly (logarithmically) diverging correlation length. This feature induces a very strong divergence of the heat capacity at the unbinding transition of a semi-flexible polymer from a columnar trap. Our exact solution of this statistical physics problem opens a new venue in the theory of molecular shape control of bio-polymers such as DNA molecules adsorbed on specially designed biocompatible surfaces.

Golubovic, Leonardo

2010-03-01

117

Brain mechanisms involved in processing unreal perceptions.  

PubMed

Individuals sometimes experience an illusory or hallucinatory perception. This unreal perception is usually resolved after the individual recognizes that the perception was not real. In this study, we investigated the brain mechanisms involved in the process to an illusory or hallucinatory perception through 'obtaining insight into unreality'. We used a novel and intuitive paradigm designed by combining functional magnetic resonance imaging and augmented reality technology to simulate visual illusory stimuli that mimic hallucinations during brain scanning. The results showed various brain activations, predominantly in the amygdala in the early phase, the medial frontal cortex and the occipitotemporal junction in the middle phase, and the thalamus in the late phase, which correlated with a subject's proneness to hallucinating. These activations may correspond to a 'responding stage' for a perception-based immediate emotional reaction, a 'monitoring stage' for integration and recalibration to ascertain that the perception was not real, and a 'resolving stage' for controlling the information and finally settling it, respectively. Our paradigm and findings may be useful in understanding the mechanisms for discriminating and coping with hallucinatory perceptions. PMID:18801444

Ku, Jeonghun; Kim, Jae-Jin; Jung, Young Chul; Park, Il Ho; Lee, Hyeongrae; Han, Kiwan; Yoon, Kang Jun; Kim, In Young; Kim, Sun I

2008-12-01

118

Reaction between peroxynitrite and boronates: EPR spin-trapping, HPLC analyses, and quantum mechanical study of the free radical pathway  

PubMed Central

Recently we showed that peroxynitrite (ONOO?) reacts directly and rapidly with aromatic and aliphatic boronic acids (k ? 106 M?1s?1). Product analyses and substrate consumption data indicated that ONOO? reacts stoichiometrically with boronates, yielding the corresponding phenols as the major product (~85–90%), and the remaining products (10–15%) were proposed to originate from free radical intermediates (phenyl and phenoxyl radicals). Here we investigated in detail the minor, free radical pathway of boronate reaction with ONOO?. The electron paramagnetic resonance (EPR) spin-trapping technique was used to characterize the free radical intermediates formed from the reaction between boronates and ONOO?. Using 2-methyl-2-nitrosopropane (MNP) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps, phenyl radicals were trapped and detected. Although phenoxyl radicals were not detected, the positive effects of molecular oxygen, and inhibitory effects of hydrogen atom donors (acetonitrile, and 2-propanol) and general radical scavengers (GSH, NADH, ascorbic acid and tyrosine) on the formation of phenoxyl radical-derived nitrated product, suggest that phenoxyl radical was formed as the secondary species. We propose that the initial step of the reaction involves the addition of ONOO? to the boron atom in boronates. The anionic intermediate undergoes both heterolytic (major pathway) and homolytic (minor pathway) cleavage of the peroxy (O-O) bond to form phenol and nitrite as a major product (via a non-radical mechanism), or a radical pair PhB(OH)2O•?…•NO2 as a minor product. It is conceivable that phenyl radicals are formed by the fragmentation of PhB(OH)2O•? radical anion. According to the DFT quantum mechanical calculations, the energy barrier for the dissociation of PhB(OH)2O•? radical anion to form phenyl radicals is only a few kcal/mol, suggesting rapid and spontaneous fragmentation of PhB(OH)2O•? radical anion in aqueous media. Biological implications of the minor free radical pathway are discussed in the context of ONOO? detection, using the boronate probes.

Sikora, Adam; Zielonka, Jacek; Lopez, Marcos; Dybala-Defratyka, Agnieszka; Joseph, Joy; Marcinek, Andrzej; Kalyanaraman, Balaraman

2013-01-01

119

Process waste assessment methodology for mechanical departments. Final report.  

National Technical Information Service (NTIS)

Process waste assessments (PWAS) were performed for three pilot processes to develop methodology for performing PWAs for all the various processes used throughout the mechanical departments. A material balance and process flow diagram identifying the raw ...

R. B. Hedrick

1992-01-01

120

Study of carrier recombination and trapping processes in gamma-ray- and proton-irradiated silicon  

Microsoft Academic Search

Carrier lifetime variations dependent on proton irradiation at fluences in the range from 5×1012 to 1015 cm-2 and gamma-ray doses ranging from 50 to 400 Mrad were investigated in high-resistivity oxygenated silicon wafers and pad detectors. Fast recombination and slow trapping constituents within recombination transients have been distinguished by combining analyses of excess carrier decays dependent on excitation intensity and

E. Gaubas; M. Bauza; J. Vaitkus; Z. Li; J. Härkönen; E. Fretwurst

2005-01-01

121

Study of carrier recombination and trapping processes in ?-ray- and proton-irradiated silicon  

Microsoft Academic Search

Carrier lifetime variations dependent on proton irradiation at fluences in the range from 5×1012 to 1015cm?2 and ?-ray doses ranging from 50 to 400Mrad were investigated in high-resistivity oxygenated silicon wafers and pad detectors. Fast recombination and slow trapping constituents within recombination transients have been distinguished by combining analyses of excess carrier decays dependent on excitation intensity and temperature, measured

E. Gaubas; M. Bauža; J. Vaitkus; Z. Li; J. Härkönen; E. Fretwurst

2005-01-01

122

Detection of deep traps for gas molecules in the diffusion processes in low-molecular glasses  

NASA Astrophysics Data System (ADS)

The kinetics of the diffusion-controlled radical oxidation in galssy alcohol matrices of n-butanol- d10 and isopentanol has been studied at various concentrations of oxygen and nitrogen in the samples. The influences of matrix annealing and gas concentrations on the kinetics have been analyzed. A conclusion on the existence of deep traps for gas molecules in n-butanol- d10 and isoamyl alcohol is drawn.

Vasenkov, S. V.; Tolkatchev, V. A.; Bazhin, N. M.

1993-05-01

123

Molecular Probes of the Mechanism of Cytochrome P450. Oxygen Traps a Substrate Radical Intermediate  

PubMed Central

The diagnostic substrate tetramethylcyclopropane (TMCP) has been reexamined as a substrate with three drug- and xenobiotic-metabolizing cytochrome P450 enzymes, human CYP2E1, CYP3A4 and rat CYP2B1. The major hydroxylation product in all cases was the unrearranged primary alcohol along with smaller amounts of a rearranged tertiary alcohol. Significantly, another ring-opened product, diacetone alcohol, was also observed. With CYP2E1 this product accounted for 20% of the total turnover. Diacetone alcohol also was detected as a product from TMCP with a biomimetic model catalyst, FeTMPyP, but not with a ruthenium porphyrin catalyst. Lifetimes of the intermediate radicals were determined from the ratios of rearranged and unrearranged products to be 120, 13 and 1 ps for CYP2E1, CYP3A4 and CYP2B1, respectively, corresponding to rebound rates of 0.9×1010 s?1, 7.2×1010 s?1 and 1.0×1012 s?1. For the model iron porphyrin, FeTMPyP, a radical lifetime of 81 ps and a rebound rate of 1.2×1010 s?1 were determined. These apparent radical lifetimes are consistent with earlier reports with a variety of CYP enzymes and radical clock substrates, however, the large amounts of diacetone alcohol with CYP2E1 and the iron porphyrin suggest that for these systems a considerable amount of the intermediate carbon radical is trapped by molecular oxygen. These results add to the view that cage escape of the intermediate carbon radical in [FeIV-OH •R] can compete with cage collapse to form a CO bond. The results could be significant with regard to our understanding of iron-catalyzed C-H hydroxylation, the observation of P450-dependent peroxidation and the development of oxidative stress, especially for CYP2E1.

Cooper, Harriet L. R.; Groves, John T.

2010-01-01

124

Structure of a RING E3 Trapped in Action Reveals Ligation Mechanism for the Ubiquitin-like Protein NEDD8.  

PubMed

Most E3 ligases use a RING domain to activate a thioester-linked E2?ubiquitin-like protein (UBL) intermediate and promote UBL transfer to a remotely bound target protein. Nonetheless, RING E3 mechanisms matching a specific UBL and acceptor lysine remain elusive, including for RBX1, which mediates NEDD8 ligation to cullins and >10% of all ubiquitination. We report the structure of a trapped RING E3-E2?UBL-target intermediate representing RBX1-UBC12?NEDD8-CUL1-DCN1, which reveals the mechanism of NEDD8 ligation and how a particular UBL and acceptor lysine are matched by a multifunctional RING E3. Numerous mechanisms specify cullin neddylation while preventing noncognate ubiquitin ligation. Notably, E2-E3-target and RING-E2?UBL modules are not optimized to function independently, but instead require integration by the UBL and target for maximal reactivity. The UBL and target regulate the catalytic machinery by positioning the RING-E2?UBL catalytic center, licensing the acceptor lysine, and influencing E2 reactivity, thereby driving their specific coupling by a multifunctional RING E3. PMID:24949976

Scott, Daniel C; Sviderskiy, Vladislav O; Monda, Julie K; Lydeard, John R; Cho, Shein Ei; Harper, J Wade; Schulman, Brenda A

2014-06-19

125

Optical trapping for analytical biotechnology.  

PubMed

We describe the exciting advances of using optical trapping in the field of analytical biotechnology. This technique has opened up opportunities to manipulate biological particles at the single cell or even at subcellular levels which has allowed an insight into the physical and chemical mechanisms of many biological processes. The ability of this technique to manipulate microparticles and measure pico-Newton forces has found several applications such as understanding the dynamics of biological macromolecules, cell-cell interactions and the micro-rheology of both cells and fluids. Furthermore we may probe and analyse the biological world when combining trapping with analytical techniques such as Raman spectroscopy and imaging. PMID:22154469

Ashok, Praveen C; Dholakia, Kishan

2012-02-01

126

Trapping kinetics in high trap density silicon nitride insulators  

Microsoft Academic Search

An analytical method has been developed to investigate the trapping kinetics of multiple trap levels in a silicon nitride insulator under very complex conditions. Solutions for the trapped-charge distribution are given for the case of a nonuniform single carrier current in an insulator having very strong charge trapping and various detrapping mechanisms such as Poole-Frenkel emission or photoionization. The trapped-charge

Steven B. Bibyk; Vikram J. Kapoor

1984-01-01

127

A model for the trap-assisted tunneling mechanism in diffused n-p and implanted n(+)-p HgCdTe photodiodes  

NASA Technical Reports Server (NTRS)

A theoretical model for the trap-assisted tunneling process in diffused n-on-p and implanted n(+)-on-p HgCdTe photodiodes is presented. The model describes the traps and the trap characteristics: concentration, energy level, and capture cross sections. We have observed that the above two types of diodes differ in the voltage dependence of the trap-assisted tunneling current and dynamic resistance. Our model takes this difference into account and offers an explanation of the phenomenon. The good fit between measured and calculated DC characteristics of the photodiodes (for medium and high reverse bias and for temperatures from 65 to 140 K) supports the validity of the model.

Rosenfeld, David; Bahir, Gad

1992-01-01

128

Trap centers in molybdates  

NASA Astrophysics Data System (ADS)

Charge carrier trapping centers have been studied in molybdates CaMoO4, SrMoO4 and PbMoO4 with the scheelite crystal structure as well as in ZnMoO4, which crystallize in a-ZnMoO4 structural type. The trap parameters such as activation energies and frequency factors have been determined. It is shown for the first time that both electrons and holes are trapped by the elements of regular crystal structure in ZnMoO4. The effect of the charge carrier trapping on luminescence properties is demonstrated. Potential influence of the traps on the scintillation process is discussed.

Spassky, D. A.; Nagirnyi, V.; Mikhailin, V. V.; Savon, A. E.; Belsky, A. N.; Laguta, V. V.; Buryi, M.; Galashov, E. N.; Shlegel, V. N.; Voronina, I. S.; Zadneprovski, B. I.

2013-10-01

129

Mechanical-mathematical modeling for landslide process  

NASA Astrophysics Data System (ADS)

Landslides process is one of the most widespread and dangerous processes in the urbanized territories. In Moscow the landslips occupy about 3 % of the most valuable territory of city. There are near 20 places of deep landslides and some hundreds of shallow landslides in Moscow. In Russia many towns are located near rivers on high coastal sides. There are many churches and historical buildings on high costs of Volga River and Moscow River. The organization of monitoring is necessary for maintenance of normal functioning of city infrastructure in a coastal zone and duly realization of effective protective actions. Last years the landslide process activization took place in Moscow. The right coast of river Moscow on its significant extent within the limits of city Moscow is struck by deep block landslides with depth up to 90 - 100 m which formation occurred in preglacial time with basis of sliding in Callovian-Oxford clays of Jurassic system on 25 - 30 m below modern level of the river . One of landslide sites is on Vorob'evy mountains, on a high slope of the right coast of the river Moscow with height of 65 m. There is a historical monument - «Andreevsky monastery», based in 1648. Also there are the complex of buildings of Presidium of the Russian Academy of Sciences, constructed in 70 - 80th years of 20-th century, bridge with station of underground "Vorob'evy mountain", constructions of sport complexes. Landslide slope is in active condition, and there are many attributes of activization of deep block landslide. In June 2007 a rather big landslide took place there near ski-jump. Another landslide site is in a southeast part of Moscow, occupying the right coast of river Moscow near museum - reserve "Kolomenskoye". The slope in this place has height of 38 - 40 m. Motions of deep landslips have begun from 1960 in connection with construction of collectors. In 70th years of XX century there was a strong activization of a slope with formation of cracks by extent up to 500 m and displacement of a landslide in the plan over 1 m. Last serious activization of a landslide has taken place in 2002 with a motion on 53 cm. Catastrophic activization of the deep blockglide landslide in the area of Khoroshevo in Moscow took place in 2006-2007. A crack of 330 m long appeared in the old sliding circus, along which a new 220 m long creeping block was separated from the plateau and began sinking with a displaced surface of the plateau reaching to 12 m. Such activization of the landslide process was not observed in Moscow since mid XIX century. The sliding area of Khoroshevo was stable during long time without manifestations of activity. Revealing of the reasons of deformation and development of ways of protection from deep landslide motions is extremely actual and difficult problem which decision is necessary for preservation of valuable historical monuments and modern city constructions. The reasons of activization and protective measures are discussed. Structure of monitoring system for urban territories is elaborated. Mechanical-mathematical model of high viscous fluid was used for modeling of matter behavior on landslide slopes. Equation of continuity and an approximated equation of the Navier-Stockes for slow motions in a thin layer were used. The results of modelling give possibility to define the place of highest velocity on landslide surface, which could be the best place for monitoring post position. Model can be used for calibration of monitoring equipment and gives possibility to investigate some fundamental aspects of matter movement on landslide slope.

Svalova, V.

2009-04-01

130

CHEMICAL AND PHYSICAL PROCESS AND MECHANISM MODELING  

EPA Science Inventory

The goal of this task is to develop and test chemical and physical mechanisms for use in the chemical transport models of EPA's Models-3. The target model for this research is the Community Multiscale Air Quality (CMAQ) model. These mechanisms include gas and aqueous phase ph...

131

Quantitative image processing in fluid mechanics  

NASA Technical Reports Server (NTRS)

The current status of digital image processing in fluid flow research is reviewed. In particular, attention is given to a comprehensive approach to the extraction of quantitative data from multivariate databases and examples of recent developments. The discussion covers numerical simulations and experiments, data processing, generation and dissemination of knowledge, traditional image processing, hybrid processing, fluid flow vector field topology, and isosurface analysis using Marching Cubes.

Hesselink, Lambertus; Helman, James; Ning, Paul

1992-01-01

132

On the Mechanization of Creative Processes.  

National Technical Information Service (NTIS)

The paper presents tentative ideas on an operational definition of creative processes in the general context of problem-solving processes. Comments are restricted to some of the creative processes that occur in the problem-solving activities of the physic...

S. Amarel

1968-01-01

133

Process for predicting structural performance of mechanical systems  

DOEpatents

A process for predicting the structural performance of a mechanical system represents the mechanical system by a plurality of surface elements. The surface elements are grouped according to their location in the volume occupied by the mechanical system so that contacts between surface elements can be efficiently located. The process is well suited for efficient practice on multiprocessor computers. 12 figs.

Gardner, D.R.; Hendrickson, B.A.; Plimpton, S.J.; Attaway, S.W.; Heinstein, M.W.; Vaughan, C.T.

1998-05-19

134

Characterization of carrier recombination and trapping processes in proton irradiated silicon by microwave absorption transients  

NASA Astrophysics Data System (ADS)

Carrier lifetime variations dependent on proton irradiation with fluences in the range from 5×10 12 to 10 15 cm -2 were investigated in high resistivity oxygenated silicon wafers and pad detectors. The fast recombination and slow trapping constituents within recombination transients have been distinguished by combining analyses of the excess carrier decay dependence on the excitation intensity, bias illumination and temperature, measured using the technique of microwave absorption by free carriers. Differences in the rate of formation and type of defects in the ranges of moderate and highest proton irradiation fluences have been revealed from the inverse lifetime dependence on irradiation fluence. The activation factors of the capture centres have been evaluated from carrier lifetime variations in the range of low and elevated temperatures.

Gaubas, E.; Vaitkus, J.; Niaura, G.; Härkönen, J.; Tuovinen, E.; Luukka, P.; Fretwurst, E.

2005-07-01

135

Study of carrier recombination and trapping processes in ?-ray- and proton-irradiated silicon  

NASA Astrophysics Data System (ADS)

Carrier lifetime variations dependent on proton irradiation at fluences in the range from 5×10 12 to 10 15 cm -2 and ?-ray doses ranging from 50 to 400 Mrad were investigated in high-resistivity oxygenated silicon wafers and pad detectors. Fast recombination and slow trapping constituents within recombination transients have been distinguished by combining analyses of excess carrier decays dependent on excitation intensity and temperature, measured using the technique of microwave absorption by free carriers. Difference in defect formation rate and type of defects in the ranges of moderate and highest proton irradiation fluences as well as between ?-ray- and proton-irradiated material have been revealed from the inverse lifetime dependence on irradiation fluence and on temperature. The activation factors of the capture centers have been evaluated from carrier lifetime variations in the range of low and elevated temperatures.

Gaubas, E.; Bauža, M.; Vaitkus, J.; Li, Z.; Härkönen, J.; Fretwurst, E.

2005-10-01

136

A fly trap mechanism provides sequence-specific RNA recognition by CPEB proteins.  

PubMed

Cytoplasmic changes in polyA tail length is a key mechanism of translational control and is implicated in germline development, synaptic plasticity, cellular proliferation, senescence, and cancer progression. The presence of a U-rich cytoplasmic polyadenylation element (CPE) in the 3' untranslated regions (UTRs) of the responding mRNAs gives them the selectivity to be regulated by the CPE-binding (CPEB) family of proteins, which recognizes RNA via the tandem RNA recognition motifs (RRMs). Here we report the solution structures of the tandem RRMs of two human paralogs (CPEB1 and CPEB4) in their free and RNA-bound states. The structures reveal an unprecedented arrangement of RRMs in the free state that undergo an original closure motion upon RNA binding that ensures high fidelity. Structural and functional characterization of the ZZ domain (zinc-binding domain) of CPEB1 suggests a role in both protein-protein and protein-RNA interactions. Together with functional studies, the structures reveal how RNA binding by CPEB proteins leads to an optimal positioning of the N-terminal and ZZ domains at the 3' UTR, which favors the nucleation of the functional ribonucleoprotein complexes for translation regulation. PMID:24990967

Afroz, Tariq; Skrisovska, Lenka; Belloc, Eulàlia; Guillén-Boixet, Jordina; Méndez, Raúl; Allain, Frédéric H-T

2014-07-01

137

A new mechanism for radiation damage processes in alkali halides  

NASA Astrophysics Data System (ADS)

We present a theory of radiation damage formation in alkali halides based on a new mechanism of dislocation climb, which involves the production of VF centers (self-trapped hole neighboring a cation vacancy) as a result of the absorption of H centers of dislocation lines. We consider the evolution of all experimentally observed extended defects: metal colloids, gas bubbles, and vacancy voids. Voids are shown to arise and grow large due to the reaction between F and VF centers at the surface of halogen bubbles. Voids can ignite a back reaction between the radiolytic products resulting in decomposition of the irradiated material.

Dubinko, V. I.; Turkin, A. A.; Vainshtein, D. I.; den Hartog, H. W.

1999-12-01

138

Communication: Trapping upconverted energy in neat platinum porphyrin films via an unexpected fusion mechanism  

NASA Astrophysics Data System (ADS)

Direct observation of an unexpected product from excited state fusion of two excited triplet states in platinum octaethylporphyrin is reported. Transient spectroscopy was used to identify the product as a metal centered (d, d) state that decays slowly compared with the rate of fusion. The reaction was demonstrated to be second order with a rate coefficient of kTTF = (5.4 +/- 0.4) × 10-10 cm3 . s-1. The results contrast with the common assumption that fusion proceeds directly to annihilation via rapid non-radiative deactivation of the products. Following visible photo-excitation, the fusion process results in energetic upconversion of the incident photons stored in the higher energy (d, d) state at irradiances below the threshold for multi-photon absorption.

Hinke, Jonathan A.; Pundsack, Tom J.; Luhman, Wade A.; Holmes, Russell J.; Blank, David A.

2013-09-01

139

Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation  

PubMed Central

The application of rapidly applied length steps to actively contracting muscle is a classic method for synchronizing the response of myosin cross-bridges so that the average response of the ensemble can be measured. Alternatively, electron tomography (ET) is a technique that can report the structure of the individual members of the ensemble. We probed the structure of active myosin motors (cross-bridges) by applying 0.5% changes in length (either a stretch or a release) within 2 ms to isometrically contracting insect flight muscle (IFM) fibers followed after 5–6 ms by rapid freezing against a liquid helium cooled copper mirror. ET of freeze-substituted fibers, embedded and thin-sectioned, provides 3-D cross-bridge images, sorted by multivariate data analysis into ?40 classes, distinct in average structure, population size and lattice distribution. Individual actin subunits are resolved facilitating quasi-atomic modeling of each class average to determine its binding strength (weak or strong) to actin. ?98% of strong-binding acto-myosin attachments present after a length perturbation are confined to “target zones” of only two actin subunits located exactly midway between successive troponin complexes along each long-pitch helical repeat of actin. Significant changes in the types, distribution and structure of actin-myosin attachments occurred in a manner consistent with the mechanical transients. Most dramatic is near disappearance, after either length perturbation, of a class of weak-binding cross-bridges, attached within the target zone, that are highly likely to be precursors of strong-binding cross-bridges. These weak-binding cross-bridges were originally observed in isometrically contracting IFM. Their disappearance following a quick stretch or release can be explained by a recent kinetic model for muscle contraction, as behaviour consistent with their identification as precursors of strong-binding cross-bridges. The results provide a detailed model for contraction in IFM that may be applicable to contraction in other types of muscle.

Wu, Shenping; Liu, Jun; Perz-Edwards, Robert J.; Tregear, Richard T.; Winkler, Hanspeter; Franzini-Armstrong, Clara; Sasaki, Hiroyuki; Goldman, Yale E.; Reedy, Michael K.; Taylor, Kenneth A.

2012-01-01

140

Density functional theory of structural transformations of oxygen-deficient centers in amorphous silica during hole trapping: Structure and formation mechanism of the E?' center  

NASA Astrophysics Data System (ADS)

We investigate the hole trapping process of a neutral oxygen vacancy in amorphous silicon dioxide (a-SiO2) using cluster calculations based on the density functional theory (DFT) method. We show that trapping a hole at a neutral oxygen vacancy leads to the formation of several types of positively charged defects. One immediate consequence of the hole trapping process at the oxygen vacancy site is the creation of the positively charged dimer, in which a unpaired electron is almost equally distributed over the two Si aoms in the defect. Our calculations further demonstrate that the dimer configuration can be transformed into other minimum energy structures. Three possible relaxation channels are likely to exist, leading to the three distinctive defect configurations called the puckered, forward-oriented, and bridged hole-trapping oxygen-deficiency center (BHODC) configurations. To evaluate the stability of these positively charged defects against discharging, we then calculate the electrical levels for all the positively charged clusters investigated here. It is shown that the BHODC configuration has the highest electrical level, implying that this type of positively charged defect is the most stable configuration against electron trapping. We also calculate the hyperfine parameters and g values of the BHODC using the DFT method. The calculated hyperfine parameters and g values are in good agreement with those observed for the E?' center. These results corroborate our previous attribution of the E?' center [Uchino and Yoko, Phys. Rev. Lett. 86, 5522 (2001)].

Uchino, T.; Yoko, T.

2006-09-01

141

Structural changes in isometrically contracting insect flight muscle trapped following a mechanical perturbation.  

PubMed

The application of rapidly applied length steps to actively contracting muscle is a classic method for synchronizing the response of myosin cross-bridges so that the average response of the ensemble can be measured. Alternatively, electron tomography (ET) is a technique that can report the structure of the individual members of the ensemble. We probed the structure of active myosin motors (cross-bridges) by applying 0.5% changes in length (either a stretch or a release) within 2 ms to isometrically contracting insect flight muscle (IFM) fibers followed after 5-6 ms by rapid freezing against a liquid helium cooled copper mirror. ET of freeze-substituted fibers, embedded and thin-sectioned, provides 3-D cross-bridge images, sorted by multivariate data analysis into ~40 classes, distinct in average structure, population size and lattice distribution. Individual actin subunits are resolved facilitating quasi-atomic modeling of each class average to determine its binding strength (weak or strong) to actin. ~98% of strong-binding acto-myosin attachments present after a length perturbation are confined to "target zones" of only two actin subunits located exactly midway between successive troponin complexes along each long-pitch helical repeat of actin. Significant changes in the types, distribution and structure of actin-myosin attachments occurred in a manner consistent with the mechanical transients. Most dramatic is near disappearance, after either length perturbation, of a class of weak-binding cross-bridges, attached within the target zone, that are highly likely to be precursors of strong-binding cross-bridges. These weak-binding cross-bridges were originally observed in isometrically contracting IFM. Their disappearance following a quick stretch or release can be explained by a recent kinetic model for muscle contraction, as behaviour consistent with their identification as precursors of strong-binding cross-bridges. The results provide a detailed model for contraction in IFM that may be applicable to contraction in other types of muscle. PMID:22761792

Wu, Shenping; Liu, Jun; Reedy, Mary C; Perz-Edwards, Robert J; Tregear, Richard T; Winkler, Hanspeter; Franzini-Armstrong, Clara; Sasaki, Hiroyuki; Lucaveche, Carmen; Goldman, Yale E; Reedy, Michael K; Taylor, Kenneth A

2012-01-01

142

Mechanical-mathematical modeling for landslide process  

Microsoft Academic Search

Landslides process is one of the most widespread and dangerous processes in the urbanized territories. In Moscow the landslips occupy about 3 % of the most valuable territory of city. There are near 20 places of deep landslides and some hundreds of shallow landslides in Moscow. In Russia many towns are located near rivers on high coastal sides. There are

V. Svalova

2009-01-01

143

Mechanical stress modeling for silicon fabrication processes  

Microsoft Academic Search

Two finite element methods are implemented to investigate localized mechanical stress fields generated during multiple stages of silicon IC fabrication. The boundary loading method (BL) uses the oxide interface stresses as a boundary condition for the substrate solution. In the fully integrated method (FI), the strains in substrate are calculated along with the oxide stress computation. Both of the methods

Hernan A. Rueda; Stephen Cea; M. E. Law

1997-01-01

144

Epigenetic mechanisms governing the process of neurodegeneration.  

PubMed

Studies elucidating how and why neurodegeneration unfolds suggest that a complex interplay between genetic and environmental factors is responsible for disease pathogenesis. Recent breakthroughs in the field of epigenetics promise to advance our understanding of these mechanisms and to promote the development of useful and effective pre-clinical risk stratification strategies, molecular diagnostic and prognostic methods, and disease-modifying treatments. PMID:22782013

Qureshi, Irfan A; Mehler, Mark F

2013-01-01

145

Epigenetic mechanisms governing the process of neurodegeneration  

PubMed Central

Studies elucidating how and why neurodegeneration unfolds suggest that a complex interplay between genetic and environmental factors is responsible for disease pathogenesis. Recent breakthroughs in the field of epigenetics promise to advance our understanding of these mechanisms and to promote the development of useful and effective pre-clinical risk stratification strategies, molecular diagnostic and prognostic methods, and disease-modifying treatments.

Qureshi, Irfan A.; Mehler, Mark F.

2012-01-01

146

Ecological and evolutionary traps  

USGS Publications Warehouse

Organisms often rely on environmental cues to make behavioral and life-history decisions. However, in environments that have been altered suddenly by humans, formerly reliable cues might no longer be associated with adaptive outcomes. In such cases, organisms can become 'trapped' by their evolutionary responses to the cues and experience reduced survival or reproduction. Ecological traps occur when organisms make poor habitat choices based on cues that correlated formerly with habitat quality. Ecological traps are part of a broader phenomenon, evolutionary traps, involving a dissociation between cues that organisms use to make any behavioral or life-history decision and outcomes normally associated with that decision. A trap can lead to extinction if a population falls below a critical size threshold before adaptation to the novel environment occurs. Conservation and management protocols must be designed in light of, rather than in spite of, the behavioral mechanisms and evolutionary history of populations and species to avoid 'trapping' them.

Schlaepfer, M.A.; Runge, M.C.; Sherman, P.W.

2002-01-01

147

Mechanism in the reaction of cytochrome c oxidase with organic hydroperoxides: an ESR spin-trapping investigation.  

PubMed Central

Organic hydroperoxides are of great utility in probing the reaction mechanism and the toxicological consequences of lipid peroxidation. In the present study, ESR spin-trapping was employed to investigate the peroxidation of mitochondrial cytochrome c oxidase (CcO) with t-butyl hydroperoxide (t-BuOOH) and cumene hydroperoxide (CumOOH). The spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was used to detect the radical species formed from the reaction of CcO with t-BuOOH. The presence of t-BuOOH-derived alkoxyl radical (t-BuO*) as the primary radical indicates reductive scission of the O-O bond by CcO. The ESR signal of DMPO/*Ot-Bu can be partially abolished by cyanide, implying that the reductive cleavage involved the haem a(3)Cu(B) binuclear site of CcO. A nitroso spin trap, 2-methyl-2-nitrosopropane (MNP), was used to detect and identify radical species from the reaction of CcO with CumOOH. In addition to the t-BuOOH-derived methyl, hydroxylmethyl and tertiary carbon-centred radicals, a protein-derived radical was detected. The intensity of the ESR signal from the protein radical increased with the CumOOH concentration at low CumOOH/CcO ratios, with maximal intensity at a ratio of 100 mol of CumOOH/mol of CcO. The immobilized protein radical adduct of MNP was stable and persistent after dialysis; it was also resistant to proteolytic digestion, suggesting that it was formed in the transmembrane region, a region that is not accessible to proteases. Its signal was greatly enhanced when CcO cysteine residues were chemically modified by N-ethylmaleimide, when the tryptophan residues in CcO were oxidized by N-bromosuccimide, and when tyrosine residues on the surface of CcO were iodinated, showing that a radical equilibrium was established among the cysteine, tryptophan and tyrosine residues of the protein-centred radical. Pre-treatment of CcO with cyanide prevented detectable MNP adduct formation, confirming that the haem a(3)-Cu(B) binuclear centre was the initial reaction site. When the CcO was pre-treated with 10 mM (100 equivalents) of CumOOH, the enzyme activity decreased by more than 20%. This inhibition was persistent after dialysis, suggesting that the detected protein-centred radical was, in part, involved in the irreversible inactivation by CumOOH. Visible spectroscopic analysis revealed that the haem a of CcO was not affected during the reaction. However, the addition of pyridine to the reaction mixture under alkaline conditions resulted in the destruction of the haem centre of CcO, suggesting that its protein matrix rather than its haem a is the target of oxidative damage by the organic hydroperoxide.

Chen, Yeong-Renn; Mason, Ronald P

2002-01-01

148

Magnetic Trapping - Trapped Radiation  

NSDL National Science Digital Library

This set of five web pages provides a non-mathematical introduction to the motion of charged particles in magnetic fields. These pages describe the "guiding center motion" which determines the motion of ions and electrons trapped in the Earth's magnetic field and in laboratory plasma devices. Also covered are gyration and mirroring, adiabatic invariance and drifts due to an electric field and gradients in the magnetic field intensity. This is part of the work "The Exploration of the Earth's Magnetosphere". A Spanish translation is available.

Stern, David

2005-04-27

149

Ultra-fast underwater suction traps  

PubMed Central

Carnivorous aquatic Utricularia species catch small prey animals using millimetre-sized underwater suction traps, which have fascinated scientists since Darwin's early work on carnivorous plants. Suction takes place after mechanical triggering and is owing to a release of stored elastic energy in the trap body accompanied by a very fast opening and closing of a trapdoor, which otherwise closes the trap entrance watertight. The exceptional trapping speed—far above human visual perception—impeded profound investigations until now. Using high-speed video imaging and special microscopy techniques, we obtained fully time-resolved recordings of the door movement. We found that this unique trapping mechanism conducts suction in less than a millisecond and therefore ranks among the fastest plant movements known. Fluid acceleration reaches very high values, leaving little chance for prey animals to escape. We discovered that the door deformation is morphologically predetermined, and actually performs a buckling/unbuckling process, including a complete trapdoor curvature inversion. This process, which we predict using dynamical simulations and simple theoretical models, is highly reproducible: the traps are autonomously repetitive as they fire spontaneously after 5–20 h and reset actively to their ready-to-catch condition.

Vincent, Olivier; Weisskopf, Carmen; Poppinga, Simon; Masselter, Tom; Speck, Thomas; Joyeux, Marc; Quilliet, Catherine; Marmottant, Philippe

2011-01-01

150

Study of dynamical process of heat denaturation in optically trapped single microorganisms by near-infrared Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The development of laser traps has made it possible to investigate single cells and record real-time Raman spectra during a heat-denaturation process when the temperature of the surrounding medium is increased. Large changes in the phenylalanine band (1004 cm-1) of near-infrared spectra between living and heat-treated cells were observed in yeast and Escerichia coli and Enterobacter aerogenes bacteria. This change appears to reflect the change in environment of phenylalanine as proteins within the cells unfold as a result of increasing temperatures. As a comparison, we measured Raman spectra of native and heat-denatured solutions of bovine serum albumin proteins, and a similar change in the phenylalanine band of spectra was observed. In addition, we measured Raman spectra of native and heat-treated solutions of pure phenylalanine molecules; no observable difference in vibrational spectra was observed. These findings may make it possible to study conformational changes in proteins within single cells.

Xie, Changan; Li, Yong-Qing; Tang, Wei; Newton, Ronald J.

2003-11-01

151

Implementation of a fully automated process purge-and-trap gas chromatograph at an environmental remediation site  

SciTech Connect

The AQUASCAN, a commercially available, fully automated purge-and-trap gas chromatograph from Sentex Systems Inc., was implemented and evaluated as an in-field, automated monitoring system of contaminated groundwater at an active DOE remediation site in Pinellas, FL. Though the AQUASCAN is designed as a stand alone process analytical unit, implementation at this site required additional hardware. The hardware included a sample dilution system and a method for delivering standard solution to the gas chromatograph for automated calibration. As a result of the evaluation the system was determined to be a reliable and accurate instrument. The AQUASCAN reported concentration values for methylene chloride, trichloroethylene, and toluene in the Pinellas ground water were within 20% of reference laboratory values.

Blair, D.S.; Morrison, D.J.

1997-03-01

152

Detailed mechanics of membrane-membrane adhesion and separation. II. Discrete kinetically trapped molecular cross-bridges.  

PubMed Central

In general, membrane-membrane adhesion involves specific molecular binding and cross-bridging reactions. The ideal, classical view is that near equilibrium the forces required to separate adhesive contacts are essentially equal to those induced in the membrane when the contact is formed. In contrast to the classical view, experimental observations often show that negligible levels of tension are induced by the adhesive contact even though the tension required to separate the contact is large enough to rupture the membrane. The deviation in tension levels associated with contact formation and separation appears to be due to the sparse distribution of strong molecular cross-bridges. Here, the mechanics of membrane-membrane adhesion and separation is developed for the case of discrete, kinetically trapped cross-bridges. The solution is obtained by numerical computation of the membrane contour that minimizes the total free energy (membrane elastic energy of deformation plus cross-bridge energies) in the contact zone. This solution is matched with the analytical solution for membrane stresses and geometry derived for the adjacent, unbridged zone. The results yield specific values of the macroscopic tension applied to the membrane in the plane region away from the contact zone and the microscopic angle at the edge of the contact zone. Two disparate values of the macroscopic tension are found: (a) the minimum tension required to separate the adherent membranes; and (b) the maximum tension induced in the membranes when the contact is formed (i.e., the level of tension at which the contact will just begin to spread). The results show that the deviation between these two tensions can be very large and depends strongly on the surface density of cross-bridges. In addition, the results provide an estimate of the restraining forces that anchor receptors within the plane of the membrane. Images FIGURE 1

Evans, E. A.

1985-01-01

153

A study of ultrafast self-trapping processes of electron-hole pairs in RbI by femtosecond pump and probe spectroscopy  

NASA Astrophysics Data System (ADS)

Initial formation processes of self-trapped excitons from free electron-hole pairs in RbI crystals have been investigated by means of a femtosecond pump and probe spectroscopy. The short-lived intermediate analogous to the one-center self-trapped hole (STH) has been observed as a precursor for the self-trapped exciton (STE) in the time region of 0.3-5 ps. The formation process of the STE in RbI is found to be quite similar to that observed in KI rather than KBr. From the observation of the two types of formation process depending on the species of halogen atom, it is found that the lattice relaxation leading to the STE formation is affected by the width of the valence band which consists of p-orbitals of halogen ions.

Iwai, S.; Nakamura, A.; Tanimura, K.; Itoh, N.

1995-12-01

154

Crystal Structures of Nitroalkane Oxidase: Insights into the Reaction Mechanism from a Covalent Complex of the Flavoenzyme Trapped during Turnover‡  

PubMed Central

Nitroalkane oxidase (NAO) from Fusarium oxysporum catalyzes the oxidation of neutral nitroalkanes to the corresponding aldehydes or ketones with the production of H2O2 and nitrite. The flavoenzyme is a new member of the acyl-CoA dehydrogenase (ACAD) family, but it does not react with acyl-CoA substrates. We present the 2.2 ? resolution crystal structure of NAO trapped during the turnover of nitroethane as a covalent N5–FAD adduct (ES*). The homotetrameric structure of ES* was solved by MAD phasing with 52 Se-Met sites in an orthorhombic space group. The electron density for the N5-(2-nitrobutyl)-1,5-dihydro-FAD covalent intermediate is clearly resolved. The structure of ES* was used to solve the crystal structure of oxidized NAO at 2.07 ? resolution. The c axis for the trigonal space group of oxidized NAO is 485 ?, and there are six subunits (1½ holoenzymes) in the asymmetric unit. Four of the active sites contain spermine (EI), a weak competitive inhibitor, and two do not contain spermine (Eox). The active-site structures of Eox, EI, and ES* reveal a hydrophobic channel that extends from the exterior of the protein and terminates at Asp402 and the N5 position on the re face of the FAD. Thus, Asp402 is in the correct position to serve as the active-site base, where it is proposed to abstract the ? proton from neutral nitroalkane substrates. The structures for NAO and various members of the ACAD family overlay with root-mean-square deviations between 1.7 and 3.1 ?. The homologous region typically spans more than 325 residues and includes Glu376, which is the active-site base in the prototypical member of the ACAD family. However, NAO and the ACADs exhibit differences in hydrogen-bonding patterns between the respective active-site base, substrate molecules, and FAD. These likely differentiate NAO from the homologues and, consequently, are proposed to result in the unique reaction mechanism of NAO.

Nagpal, Akanksha; Valley, Michael P.; Fitzpatrick, Paul F.; Orville, Allen M.

2006-01-01

155

Crystal Structures of Nitroalkane Oxidase: Insights into the Reaction Mechanism of a Covalent Complex of the Flavoenzyme Trapped During Turnover  

SciTech Connect

Nitroalkane oxidase (NAO) from Fusarium oxysporum catalyzes the oxidation of neutral nitroalkanes to the corresponding aldehydes or ketones with the production of H2O2 and nitrite. The flavoenzyme is a new member of the acyl-CoA dehydrogenase (ACAD) family, but it does not react with acyl-CoA substrates. We present the 2.2 Angstroms resolution crystal structure of NAO trapped during the turnover of nitroethane as a covalent N5-FAD adduct (ES*). The homotetrameric structure of ES* was solved by MAD phasing with 52 Se-Met sites in an orthorhombic space group. The electron density for the N5-(2-nitrobutyl)-1,5-dihydro-FAD covalent intermediate is clearly resolved. The structure of ES* was used to solve the crystal structure of oxidized NAO at 2.07 Angstroms resolution. The c axis for the trigonal space group of oxidized NAO is 485 Angstroms, and there are six subunits (11/2 holoenzymes) in the asymmetric unit. Four of the active sites contain spermine (EI), a weak competitive inhibitor, and two do not contain spermine (E{sup ox}). The active-site structures of E{sup ox}, EI, and ES* reveal a hydrophobic channel that extends from the exterior of the protein and terminates at Asp402 and the N5 position on the re face of the FAD. Thus, Asp402 is in the correct position to serve as the active-site base, where it is proposed to abstract the {alpha} proton from neutral nitroalkane substrates. The structures for NAO and various members of the ACAD family overlay with root-mean-square deviations between 1.7 and 3.1 Angstroms. The homologous region typically spans more than 325 residues and includes Glu376, which is the active-site base in the prototypical member of the ACAD family. However, NAO and the ACADs exhibit differences in hydrogen-bonding patterns between the respective active-site base, substrate molecules, and FAD. These likely differentiate NAO from the homologues and, consequently, are proposed to result in the unique reaction mechanism of NAO.

Nagpal,A.; Valley, M.; Fitzpatrick, P.; Orville, A.

2006-01-01

156

Trap-controlled hydrogen diffusion and the mechanism of light-enhanced diffusion in [ital a]-Si:H  

SciTech Connect

We review our recent high-depth-resolution secondary ion mass spectrometry studies of hydrogen diffusion in amorphous silicon. We describe the trap-controlled H diffusion model supported by the experiments. Recent results on light enhancement of H diffusion in [ital a]-Si:H are also discussed.

Branz, H.M.; Asher, S.E.; Nelson, B.P. (National Renewable Energy Laboratory, Golden, Colorado (United States))

1992-12-01

157

Venus fly trap  

NSDL National Science Digital Library

Time-lapse photos or video show progressions from the start of an event to the end of the event. These time-lapse photos illustrate the growth of a single Venus fly trap. Biological processes require time.

Paul Lenz (None;)

2006-01-26

158

Mechanical Behavior and Processing of Aluminum Metal Matrix Composites.  

National Technical Information Service (NTIS)

The objectives of the present three year research program were threefold. First the program sought to explore the potential of using spray atomization and deposition to process aluminum metal matrix composites, not only with improved mechanical properties...

E. J. Lavernia F. A. Mohamed

1992-01-01

159

Evaluation of sheet mechanical response to laser welding processes.  

National Technical Information Service (NTIS)

The simulation of the mechanical response of steel sheets, due to the heating during welding processes by a laser source beam, obtained by Abaqus standard code, is discussed. Different hypotheses for the material behaviour at temperatures greater than the...

B. Carmignani A. Daneri G. Toselli R. Vitali G. L. Zanotelli

1995-01-01

160

WASTE PROCESSING: THE STATUS OF MECHANICAL AND BIOLOGICAL TREATMENT  

Microsoft Academic Search

The term 'Mechanical and Biological' (MBT) is commonly used to describe a hybrid process which combines Mechanical techniques used to sort municipal solid waste (MSW) and Biological techniques used to stabilise the organic fraction of it. Recently, these concepts have attracted considerable attention and have received support from public officials and environmental organisations. MBT is a step within the whole

Monique Kallassy; Boris Efremenko; Martin Champel

161

Mechanisms That Interchange Axial and Equatorial Atoms in Fluxional Processes  

NSDL National Science Digital Library

The Berry pseudorotation is a classical mechanism for interchanging axial and equatorial ligands in molecules with trigonal bipyramidal geometry. Teaching this mechanism presents particular pedagogic problems due to both its dynamic and three dimensional character. The approach taken here illustrates these processes using interactive animations embedded in a Web page and overcomes many limitations of a printed page.

162

Prediction of thermo-mechanical integrity of wafer backend processes  

Microsoft Academic Search

More than 65% of IC failures are related to thermal and mechanical problems. For wafer backend processes, thermo-mechanical failure is one of the major bottlenecks. The ongoing technological trends like miniaturization, introduction of new materials, and function\\/product integration will increase the importance of thermomechanical reliability, as confirmed by the ITRS (International technology roadmap for semiconductors; [1]). Since most of the

V. Gonda; J. M. J. Den Toonder; J. Beijer; G. Q. Zhang; W. D. van Driel; R. J. O. M. Hoofman; L. J. Ernst

2004-01-01

163

Processing, mechanical properties and microfractography of polymer concrete composite material  

Microsoft Academic Search

Mechanical properties of methyl methacrylate (MMA)-based polymer concrete (PC) were studied by means of various mechanical tests and microscopic observation. It was found that the casting and curing process is one of the most important factors influencing the strength of PC. Since the compressive strength of PC gives a general indication of its overall quality, and since PC materials are

1986-01-01

164

Memory effect of low-temperature processed ZnO thin-film transistors having metallic nanoparticles as charge trapping elements.  

PubMed

In this study, non-volatile memory effect was characterized using the single-transistor-based memory devices based on self-assembled gold nanoparticles (AuNP) as the charge trapping elements and atomic-layer deposited ZnO as the channel layer. The fabricated memory devices showed controllable and reliable threshold voltage shifts according to the program/erase operations that resulted from the charging/discharging of charge carriers in the charge trapping elements. Reliable non-volatile memory properties were also confirmed by the endurance and data retention measurements. The low temperature processes of the key device elements, i.e., AuNP charge trapping layer and ZnO channel layer, enable the use of this device structure to the transparent/flexible non-volatile memory applications in the near future. PMID:22629953

Park, Young-Su; Kim, Soo-Jin; Lyu, Si-Hoon; Lee, Byoung Hoon; Sung, Myung Mo; Lee, Jaegab; Lee, Jang-Sik

2012-02-01

165

Optical trapping  

PubMed Central

Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on—and the measurement of nanometer-level displacements of—optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications.

Neuman, Keir C.; Block, Steven M.

2006-01-01

166

Mechanical pre-treatment (MPT) - revitalised by MBR process.  

PubMed

Since the mid-nineties membrane bioreactor (MBR) technology has been introduced to municipal wastewater treatment in Europe. The first MBR plants went into operation performing a conventional mechanical pre-treatment (MPT) without any advanced treatment units. After a short operation period, clogging caused by fibrous substances and hence module sludging was observed. Thus, MPT was upgraded introducing sieves. Several investigations had been carried out to determine the removal efficiency of different sieve units and entire MPT systems. Meanwhile experiences from long-term operation at different MBR sites indicate dependencies between different MPT units, especially between the aerated grit chamber/grease trap and the subsequent sieve unit. Usually the sieve is the final MPT unit and its performance depends on the performance of the upstream MPT units. This report describes and discusses results from a research project at MBR Kaarst-Nordkanal in Germany conducted in 2008 to 2010 by the Water Board of River Erft and the Department of Sanitary and Environmental Engineering. Main focus is addressed for the parameters SS (settable solids) and grease. One major experience is the confirmation of relevant interactions between the grit chamber and the downstream sieve unit. Stable operation of the grit chamber and grease trap is essential to achieve a constantly high removal performance of the sieve unit and therefore the entire MPT stage. In turn, negative impacts on the grit chamber performance from the return flow concept have to be avoided. Finally, it is shown that the appropriate two-dimensional sieve gap size should not go beyond 1 mm when operating hollow fibre membranes. PMID:23109566

Schier, W; Drensla, K; Janot, A; Exler, H; Engelhardt, N; Frechen, F-B

2012-01-01

167

Processing and mechanical properties of nanocrystalline 5083 al alloy  

Microsoft Academic Search

A commercial aluminum alloy, 5083, was processed using a cryomilling synthesis approach to produce nanocrystalline powders. The powders were subsequently degassed, HIPped, and extruded to produce a thermally stable bulk nanocrystalline material. The grain size at each processing step was measured utilizing both X-ray diffraction and transmission electron microscopy. The mechanical properties of the n-5083 extruded material were determined utilizing

V. L. Tellkamp; E. J. Lavernia

1999-01-01

168

Simplifying steam trap selection  

SciTech Connect

In the current economic world order, there is an obligation to eliminate waste and conserve economic and natural resources. One trap blowing 100-lb of steam through a 1/4-in. orifice can cost more than $12,000 a year in wasted energy. Richard J. Debat of Armstrong International, Inc. explains the operating principles of the four basic types of steam traps as the first step in simplifying the selection process so the right trap can be specified for a given application.

Debat, R.J. (Armstrong International, Inc., Three Rivers, MI (United States))

1994-01-01

169

Two-Dimensional Patterning by a Trapping/Depletion Mechanism: The Role of TTG1 and GL3 in Arabidopsis Trichome Formation  

PubMed Central

Trichome patterning in Arabidopsis serves as a model system to study how single cells are selected within a field of initially equivalent cells. Current models explain this pattern by an activator–inhibitor feedback loop. Here, we report that also a newly discovered mechanism is involved by which patterning is governed by the removal of the trichome-promoting factor TRANSPARENT TESTA GLABRA1 (TTG1) from non-trichome cells. We demonstrate by clonal analysis and misexpression studies that Arabidopsis TTG1 can act non-cell-autonomously and by microinjection experiments that TTG1 protein moves between cells. While TTG1 is expressed ubiquitously, TTG1–YFP protein accumulates in trichomes and is depleted in the surrounding cells. TTG1–YFP depletion depends on GLABRA3 (GL3), suggesting that the depletion is governed by a trapping mechanism. To study the potential of the observed trapping/depletion mechanism, we formulated a mathematical model enabling us to evaluate the relevance of each parameter and to identify parameters explaining the paradoxical genetic finding that strong ttg1 alleles are glabrous, while weak alleles exhibit trichome clusters.

Bouyer, Daniel; Schnittger, Arp; Pesch, Martina; Wester, Katja; Balkunde, Rachappa; Timmer, Jens; Fleck, Christian; Hulskamp, Martin

2008-01-01

170

Antihydrogen Trapped  

NASA Astrophysics Data System (ADS)

In 2010 the ALPHA collaboration succeeded in trapping antihydrogen atoms for the first time.ootnotetext``Trapped antihydrogen,'' G.B. Andresen et al., Nature 468, 673 (2010) Stored antihydrogen promises to be a unique tool for making high precision measurements of the structure of this first anti-atom. Achieving this milestone presented several substantial experimental challenges and this talk will describe how they were overcome. The unique design features of the ALPHA apparatus will be explained.ootnotetext``A Magnetic Trap for Antihydrogen Confinement,'' W. Bertsche et al., Nucl. Instr. Meth. Phys. Res. A 566, 746 (2006) These allow a high intensity positron source and an antiproton imaging detector similar to the one used in the ATHENAootnotetext``Production and detection of cold antihydrogen atoms,'' M.Amoretti et al., Nature 419, 456 (2002). experiment to be combined with an innovative magnet design of the anti-atom trap. This seeks to minimise the perturbations to trapped charged particles which may cause particle loss and heating.ootnotetext``Antihydrogen formation dynamics in a multipolar neutral anti-atom trap.'' G.B. Andresen et al., Phys. Lett. B 685, 141 (2010) The diagnostic techniques used to measure the diameter, number, density, and temperatures of both plasmas will be presented as will the methods developed to actively compress and cool of both plasma species to sizes and temperaturesootnotetext``Evaporative Cooling of Antiprotons to Cryogenic Temperatures,'' G.B. Andresen et al. Phys. Rev. Lett 105, 013003 (2010)^,ootnotetext``Compression of Antiproton Clouds for Antihydrogen Trapping,'' G. B. Andresen et al. Phys. Rev. Lett 100, 203401 (2008)^,ootnotetext``Autoresonant Excitation of Antiproton Plasmas,'' G.B. Andresen et al., Phys. Rev. Lett. 106, 025002 (2011) where trapping attempts with a reasonable chance of success can be tried. The results of the successful trapping experiments will be outlined as well as some subsequent experiments to improve the trapping rate and storage time.

Bowe, Paul D.

2011-06-01

171

Carnivorous plants: trapping, digesting and absorbing all in one.  

PubMed

The Venus flytrap digests and absorbs its prey, but how does it coordinate digestion and absorption to maximise the efficiency of this highly evolved mechanism? A new study that combines direct recordings from cells within the trap along with molecular characterization of nutrient transport reveals a complex and coordinated suite of mechanisms that underlie this elegant process. PMID:24028948

Brownlee, Colin

2013-09-01

172

ThermoMechanical Processing Parameters for the INCONEL ALLOY 740  

Microsoft Academic Search

In 2000, a Cooperative Research and Development Agreement (CRADA) was undertaken between the Oak Ridge National Laboratory (ORNL) and the Special Metals Corporation (SMC) to determine the mechanical property response of the IN740 alloy to help establish thermo-mechanical processing parameters for the use of this alloy in supercritical and ultra-critical boiler tubes with the potential for other end uses. SMC

G. M. Ludtka; G. Smith

2007-01-01

173

40 CFR 408.240 - Applicability; description of the mechanized clam processing subcategory.  

Code of Federal Regulations, 2010 CFR

...Applicability; description of the mechanized clam processing subcategory. 408.240 ...PROCESSING POINT SOURCE CATEGORY Mechanized Clam Processing Subcategory § 408.240 Applicability; description of the mechanized clam processing subcategory. The...

2010-07-01

174

40 CFR 408.240 - Applicability; description of the mechanized clam processing subcategory.  

Code of Federal Regulations, 2013 CFR

...Applicability; description of the mechanized clam processing subcategory. 408.240 ...PROCESSING POINT SOURCE CATEGORY Mechanized Clam Processing Subcategory § 408.240 Applicability; description of the mechanized clam processing subcategory. The...

2013-07-01

175

40 CFR 408.240 - Applicability; description of the mechanized clam processing subcategory.  

Code of Federal Regulations, 2010 CFR

...Applicability; description of the mechanized clam processing subcategory. 408.240 ...PROCESSING POINT SOURCE CATEGORY Mechanized Clam Processing Subcategory § 408.240 Applicability; description of the mechanized clam processing subcategory. The...

2009-07-01

176

40 CFR 408.30 - Applicability; description of the mechanized blue crab processing subcategory.  

Code of Federal Regulations, 2010 CFR

...Applicability; description of the mechanized blue crab processing subcategory. 408.30...PROCESSING POINT SOURCE CATEGORY Mechanized Blue Crab Processing Subcategory § 408.30...Applicability; description of the mechanized blue crab processing subcategory. The...

2010-07-01

177

40 CFR 408.30 - Applicability; description of the mechanized blue crab processing subcategory.  

Code of Federal Regulations, 2010 CFR

...Applicability; description of the mechanized blue crab processing subcategory. 408.30...PROCESSING POINT SOURCE CATEGORY Mechanized Blue Crab Processing Subcategory § 408.30...Applicability; description of the mechanized blue crab processing subcategory. The...

2009-07-01

178

Mechanics of aeolian processes: Soil erosion and dust production  

NASA Technical Reports Server (NTRS)

Aeolian (wind) processes occur as a result of atmosphere/land-surface system interactions. A thorough understanding of these processes and their physical/mechanical characterization on a global scale is essential to monitoring global change and, hence, is imperative to the fundamental goal of the Earth observing system (Eos) program. Soil erosion and dust production by wind are of consequence mainly in arid and semi arid regions which cover 36 percent of the Earth's land surface. Some recent models of dust production due to wind erosion of agricultural soils and the mechanics of wind erosion in deserts are reviewed and the difficulties of modeling the aeolian transport are discussed.

Mehrabadi, M. M.

1989-01-01

179

Processing, reliability and integration issues in chemical mechanical planarization  

NASA Astrophysics Data System (ADS)

Global planarization is one of the major demands of the semiconductor industry. Chemical mechanical polishing (CMP) is the planarization method of choice use to achieve the required stringent tolerances essential for successful fabrication of next generation Integrated Circuits (IC). The predominant reason for CMP defects is the shear and normal stresses during polishing to which the material is subjected. Understanding the process of CMP and factor that contribute to overall stress addition during polishing requires an approach that encompasses all the four major categories of variables, namely: (a) machine parameters, (b) material properties, (c) polishing pad characteristics, and (d) polishing slurry performance. In this research, we studied the utilized in-situ technique involving acoustic emission (AE) signal monitoring and coefficient of friction (COF) monitoring using a CETR(TM) Bench Top CMP Tester to evaluate the impact of variation in machine parameters on the CMP process. The mechanical and tribological properties of different candidate materials have been evaluated bring potential challenges in their integration to the fore. The study also involves destructive and non destructive testing of polishing pads performed for characterization and optimization of polishing pad architecture. Finally, the investigation concludes proposing novel nanoparticle CMP slurry which has a predominant chemical component in its polishing mechanism. It was found that the decrease in the mechanical shear and normal loading by: (a) operating the process in the low stress regime, (b) using potential materials that are mechanically stronger, (c) using polishing pads with lesser variation in specific gravity and with a surface that is has its mechanical properties fine tuned to those of the wafer, and (d) deploying polishing slurry with a significant chemical component mechanical removal, are some of the approaches that can be employed to meet the future challenges of the CMP process and reduce the defect associated with it.

Zantye, Parshuram B.

180

Mechanistic, kinetic, and processing aspects of tungsten chemical mechanical polishing  

NASA Astrophysics Data System (ADS)

This dissertation presents an investigation into tungsten chemical mechanical polishing (CMP). CMP is the industrially predominant unit operation that removes excess tungsten after non-selective chemical vapor deposition (CVD) during sub-micron integrated circuit (IC) manufacture. This work explores the CMP process from process engineering and fundamental mechanistic perspectives. The process engineering study optimized an existing CMP process to address issues of polish pad and wafer carrier life. Polish rates, post-CMP metrology of patterned wafers, electrical test data, and synergy with a thermal endpoint technique were used to determine the optimal process. The oxidation rate of tungsten during CMP is significantly lower than the removal rate under identical conditions. Tungsten polished without inhibition during cathodic potentiostatic control. Hertzian indenter model calculations preclude colloids of the size used in tungsten CMP slurries from indenting the tungsten surface. AFM surface topography maps and TEM images of post-CMP tungsten do not show evidence of plow marks or intergranular fracture. Polish rate is dependent on potassium iodate concentration; process temperature is not. The colloid species significantly affects the polish rate and process temperature. Process temperature is not a predictor of polish rate. A process energy balance indicates that the process temperature is predominantly due to shaft work, and that any heat of reaction evolved during the CMP process is negligible. Friction and adhesion between alumina and tungsten were studied using modified AFM techniques. Friction was constant with potassium iodate concentration, but varied with applied pressure. This corroborates the results from the energy balance. Adhesion between the alumina and the tungsten was proportional to the potassium iodate concentration. A heuristic mechanism, which captures the relationship between polish rate, pressure, velocity, and slurry chemistry, is presented. In this mechanism, the colloid reacts with the chemistry of the slurry to produce active sites. These active sites become inactive by removing tungsten from the film. The process repeats when then inactive sites are reconverted to active sites. It is shown that the empirical form of the heuristic mechanism fits all of the data obtained. The mechanism also agrees with the limiting cases that were investigated.

Stein, David

181

On Mechanisms Underlying Regeneration and Reparation Processes in Tissues  

Microsoft Academic Search

Studies of the possibility of regulating the regenerative and reparative processes in pathologically modified tissues are\\u000a reviewed. A ready cell system providing the realization of reparative and regenerative processes in all organs (cell sources\\u000a of regeneration) exists in all organisms. The authors suggest that active bioregulators presented in this paper are involved\\u000a in the mechanisms of tissue regeneration by modulating

V. P. Yamskova; M. S. Krasnov; I. A. Yamskov

2010-01-01

182

On mechanisms underlying regeneration and reparation processes in tissues.  

PubMed

Studies of the probability of regulating the regenerative and reparative processes in pathologically modified tissues are reviewed. A ready cell system, providing the realization of reparative and regenerative processes in all organs (cell sources of regeneration), exists in all organisms. The authors suggest that active bioregulators, presented in this paper, are involved in the mechanisms of tissue regeneration by modulating the cell sources of regeneration. PMID:21113477

Yamskova, V P; Krasnov, M S; Yamskov, I A

2010-07-01

183

Integrated silicon-PDMS process for microrobot mechanisms  

Microsoft Academic Search

The first MEMS process integrating soft elastomers in a standard silicon-on-insulator (SOI) wafer without assembly has been demonstrated for use in microrobotic mechanisms. This process allows silicon and poly(dimethylsiloxane) (PDMS) features to be defined in-plane with feature sizes down to 2 ?m. Test structures have been used to characterize the Young's modulus of the resulting PDMS at 1.4 MPa along

Aaron P. Gerratt; Ivan Penskiy; Sarah Bergbreiter

2010-01-01

184

Round robin measurements of the flux trapping properties of melt processed Sm-Ba-Cu-O bulk superconductors  

NASA Astrophysics Data System (ADS)

Scanning Hall probe round robin measurements of the trapped field of two CFRF-clad, epoxy resin-reinforced large grain samples of Sm-Ba-Cu-O fabricated at ISTEC-SRL by top seeded melt growth (TSMG) have been performed by five European laboratories over a two year period under the auspice of the Versailles Project on Advanced Materials and Standards (VAMAS) and Technical Committee 90 (TC90) of the International Electrotechnical Commission (IEC). This study completes the interim report of the round robin tests presented at the fourth PASREG Workshop, Jena, July 2003. The peak fields derived from flux profiles measured by the different groups are found to correlate to within 6% over the measurement period. The flux trapping ability of the samples, measured by the peak field in the upper surface, deteriorated over the period of measurement by around 2% and 1%, respectively. Overall the measurements suggest that the trapped flux profile is most sensitive to changes in magnetizing field, experimental geometry and the sample-Hall probe separation. As a result, variations in these parameters should be minimized during flux mapping. In general a magnetizing field of 1.75 times the maximum trapped field for field cooled (FC) samples is required to ensure complete magnetization of a homogeneous cylindrical sample with an aspect ratio of ?2.5, corresponding to the geometry of the samples measured here. Finally, 20 min relaxation time following magnetization was observed to be sufficient to yield consistent measurement of the peak trapped field within the error of the measurement, which was typically less than 4%. Other than the recommended magnetizing field of 3 T, which should be determined by aspect ratio, temperature and maximum trapped field rather than pre-defined, the experimental conditions were confirmed to lie within the guidelines described in a draft International Electrotechnical Commission (IEC) Technical Committee 90 (TC90) standardization document on flux mapping. On the basis of the present results the proposed 5% spread in measured trapped field and a 20 min relaxation period appear to be reasonable criteria for trapped field measurements performed at different laboratories.

Cardwell, D. A.; Murakami, M.; Zeisberger, M.; Gawalek, W.; Gonzalez-Arrabal, R.; Eisterer, M.; Weber, H. W.; Fuchs, G.; Krabbes, G.; Leenders, A.; Freyhardt, H. C.; Chaud, X.; Tournier, R.; Hari Babu, N.

2004-10-01

185

Processive kinesins require loose mechanical coupling for efficient collective motility  

PubMed Central

Processive motor proteins are stochastic steppers that perform actual mechanical steps for only a minor fraction of the time they are bound to the filament track. Motors usually work in teams and therefore the question arises whether the stochasticity of stepping can cause mutual interference when motors are mechanically coupled. We used biocompatible surfaces to immobilize processive kinesin-1 motors at controlled surface densities in a mechanically well-defined way. This helped us to study quantitatively how mechanical coupling between motors affects the efficiency of collective microtubule transport. We found that kinesin-1 constructs that lack most of the non-motor sequence slow each other down when collectively transporting a microtubule, depending on the number of interacting motors. This negative interference observed for a motor ensemble can be explained quantitatively by a mathematical model using the known physical properties of individual molecules of kinesin-1. The non-motor extension of kinesin-1 reduces this mutual interference, indicating that loose mechanical coupling between motors is required for efficient transport by ensembles of processive motors.

Bieling, Peter; Telley, Ivo A; Piehler, Jacob; Surrey, Thomas

2008-01-01

186

Steam trap monitor  

DOEpatents

A steam trap monitor positioned downstream of a steam trap in a closed steam system includes a first sensor (a hot finger) for measuring the energy of condensate and a second sensor (a cold finger) for measuring the total energy of condensate and steam in the line. The hot finger includes one or more thermocouples for detecting condensate level and energy, while the cold finger contains a liquid with a lower boiling temperature than that of water. Vapor pressure from the liquid is used to do work such as displacing a piston or bellow in providing an indication of total energy (steam + condensate) of the system. Processing means coupled to and responsive to outputs from the hot and cold fingers subtracts the former from the latter to provide an indication of the presence of steam downstream from the trap indicating that the steam trap is malfunctioning. 2 figs.

Ryan, M.J.

1987-05-04

187

Early Olfactory Processing in Drosophila: Mechanisms and Principles  

PubMed Central

In the olfactory system of Drosophila melanogaster, it is relatively straightforward to make in vivo measurements of activity in neurons corresponding to targeted processing. This, together with the numerical simplicity of the Drosophila olfactory system, has produced rapid gains in our understanding of Drosophila olfaction. This review summarizes the neurophysiology of the first two layers of this system: the peripheral olfactory receptor neurons and their postsynaptic targets in the antennal lobe. We now understand in some detail the cellular and synaptic mechanisms that shape odor representations in these neurons. Together, these mechanisms imply that interesting neural adaptations to environmental statistics have occurred and place some fundamental constraints on early sensory processing that pose challenges for higher brain regions. These findings suggest some general principles with broad relevance to early sensory processing in other modalities.

Wilson, Rachel I.

2014-01-01

188

Primary Processes in the Action of Ionizing Radiations on Water: Formation And Reactivity of Self-Trapped Electrons (`Polarons')  

Microsoft Academic Search

Recent evidence is reviewed which indicates that positive as well as ; negative ionic species formed from the water may be important in the radiation ; chemistry of aqueous systems. Evidence is presented that there are two reducing ; species present in solution, namely hydrogen atoms and electrons. The self-; trapped electrons in the dielectric medium (water) were tentatively identified

Joseph Weiss

1960-01-01

189

Analysis of fault traps  

SciTech Connect

Unfaulted four-way-dip closures are the simplest and most attractive hydrocarbon traps. A single sealing lithology can provide both top and lateral seals. Seal risks are minimized with unfaulted four-way-dip closures. Unfortunately, most large four-way-drip closures have already been drilled, particularly in mature areas such as the US Gulf Coast. Exceptions may exist in deep water, at great depth, or in areas with significant lateral velocity variations, but for the most part, explorationists working mature areas are looking for either fault traps or stratigraphic traps. This article focuses on extensional fault systems, although many of the observations are applicable to compressional and strike-slip faulting. The following topics are discussed: mapping faults including discussions on the aliasing problem, fault shape, 3-D data, en echelon faults and the coherence cube; a general discussion of fault traps; juxtaposition traps and the use of ``Allan sections;`` and fault-sealing traps and the three mechanisms that cause fault-zone capillary properties to differ from unfaulted rock -- clay smear, grain crushing and diagenesis.

Brenneke, J.C. [Subsurface Consultants and Associates, Inc., Houston, TX (United States)

1995-12-01

190

An improved numerical process for solution of solid mechanics problems  

NASA Technical Reports Server (NTRS)

This paper gives an overview of the development and status of an improved numerical process for the solution of solid mechanics problems. The proposed process uses a mixed formulation with the fundamental unknowns consisting of both stress and displacement parameters. The problem is formulated either by means of first-order partial differential equations or in a variational form by using a Hellinger-Reissner-type mixed variational principle. For presentation purposes, the components of a numerical process are characterized and the criteria for an ideal process are outlined. Commonly used finite-difference and finite-element procedures are examined in the light of these criteria and it is shown that they fall short in a number of ways. The proposed numerical process, on the other hand, satisfies most of the optimality criteria and appears to be particularly suited for use with the forthcoming generation computers.

Noor, A. K.; Stephens, W. B.; Fulton, R. E.

1973-01-01

191

40 CFR 408.190 - Applicability; description of the West Coast mechanized salmon processing subcategory.  

Code of Federal Regulations, 2010 CFR

...description of the West Coast mechanized salmon processing subcategory. 408.190...SOURCE CATEGORY West Coast Mechanized Salmon Processing Subcategory § 408.190...description of the West Coast mechanized salmon processing subcategory. The...

2010-07-01

192

40 CFR 408.170 - Applicability; description of the Alaskan mechanized salmon processing subcategory.  

Code of Federal Regulations, 2010 CFR

...description of the Alaskan mechanized salmon processing subcategory. 408.170...POINT SOURCE CATEGORY Alaskan Mechanized Salmon Processing Subcategory § 408.170...description of the Alaskan mechanized salmon processing subcategory. The...

2009-07-01

193

40 CFR 408.190 - Applicability; description of the West Coast mechanized salmon processing subcategory.  

Code of Federal Regulations, 2013 CFR

...description of the West Coast mechanized salmon processing subcategory. 408.190...SOURCE CATEGORY West Coast Mechanized Salmon Processing Subcategory § 408.190...description of the West Coast mechanized salmon processing subcategory. The...

2013-07-01

194

40 CFR 408.170 - Applicability; description of the Alaskan mechanized salmon processing subcategory.  

Code of Federal Regulations, 2013 CFR

...description of the Alaskan mechanized salmon processing subcategory. 408.170...POINT SOURCE CATEGORY Alaskan Mechanized Salmon Processing Subcategory § 408.170...description of the Alaskan mechanized salmon processing subcategory. The...

2013-07-01

195

40 CFR 408.190 - Applicability; description of the West Coast mechanized salmon processing subcategory.  

Code of Federal Regulations, 2010 CFR

...description of the West Coast mechanized salmon processing subcategory. 408.190...SOURCE CATEGORY West Coast Mechanized Salmon Processing Subcategory § 408.190...description of the West Coast mechanized salmon processing subcategory. The...

2009-07-01

196

42 CFR 433.116 - FFP for operation of mechanized claims processing and information retrieval systems.  

Code of Federal Regulations, 2013 CFR

...mechanized claims processing and information retrieval systems. 433.116 Section...Mechanized Claims Processing and Information Retrieval Systems § 433.116 ...mechanized claims processing and information retrieval systems. (a)...

2013-10-01

197

40 CFR 408.190 - Applicability; description of the West Coast mechanized salmon processing subcategory.  

Code of Federal Regulations, 2011 CFR

...description of the West Coast mechanized salmon processing subcategory. 408.190...SOURCE CATEGORY West Coast Mechanized Salmon Processing Subcategory § 408.190...description of the West Coast mechanized salmon processing subcategory. The...

2011-07-01

198

40 CFR 408.170 - Applicability; description of the Alaskan mechanized salmon processing subcategory.  

Code of Federal Regulations, 2012 CFR

...description of the Alaskan mechanized salmon processing subcategory. 408.170...POINT SOURCE CATEGORY Alaskan Mechanized Salmon Processing Subcategory § 408.170...description of the Alaskan mechanized salmon processing subcategory. The...

2012-07-01

199

40 CFR 408.190 - Applicability; description of the West Coast mechanized salmon processing subcategory.  

Code of Federal Regulations, 2012 CFR

...description of the West Coast mechanized salmon processing subcategory. 408.190...SOURCE CATEGORY West Coast Mechanized Salmon Processing Subcategory § 408.190...description of the West Coast mechanized salmon processing subcategory. The...

2012-07-01

200

40 CFR 408.170 - Applicability; description of the Alaskan mechanized salmon processing subcategory.  

Code of Federal Regulations, 2010 CFR

...description of the Alaskan mechanized salmon processing subcategory. 408.170...POINT SOURCE CATEGORY Alaskan Mechanized Salmon Processing Subcategory § 408.170...description of the Alaskan mechanized salmon processing subcategory. The...

2010-07-01

201

40 CFR 408.170 - Applicability; description of the Alaskan mechanized salmon processing subcategory.  

Code of Federal Regulations, 2011 CFR

...description of the Alaskan mechanized salmon processing subcategory. 408.170...POINT SOURCE CATEGORY Alaskan Mechanized Salmon Processing Subcategory § 408.170...description of the Alaskan mechanized salmon processing subcategory. The...

2011-07-01

202

UNDERSTANDING OLIVINE CO2 MINERAL SEQUESTRATION MECHANISMS AT THE ATOMIC LEVEL: OPTIMIZING REACTION PROCESS DESIGN  

SciTech Connect

Carbonation of Mg-rich minerals offers an intriguing candidate carbon sequestration process technology, which can provide large-scale CO{sub 2} disposal. Such disposal bypasses many long-term storage problems by (i) providing containment in the form of mineral carbonates that have proven stable over geological time, (ii) generating only environmentally benign materials, and (iii) essentially eliminating the need for continuous site monitoring. The primary challenge for viable process development is reducing process cost. This is the primary focus of the CO{sub 2} Mineral Sequestration Working Group managed by Fossil Energy at DOE, which includes members from the Albany Research Center, Los Alamos National Laboratory, the National Energy Technology Laboratory, Penn State University, Science Applications International Corporation, and the University of Utah, as well as from our research group at Arizona State University. Carbonation of the widely occurring mineral olivine (e.g., forsterite, Mg{sub 2}SiO{sub 4}) is a leading process candidate, which converts CO{sub 2} into the mineral magnesite (MgCO{sub 3}). As olivine carbonation is exothermic, it offers intriguing low-cost potential. Recent studies at the Albany Research Center have found aqueous-solution carbonation is a promising approach. Cost effectively enhancing carbonation reactivity is central to reducing process cost. Many of the mechanisms that impact reactivity occur at the solid/solution interface. Understanding these mechanisms is central to the ability to engineer new and modified processes to enhance carbonation reactivity and lower cost. Herein, we report the results of our UCR I project, which focused on exploring the reaction mechanisms that govern aqueous-solution olivine carbonation using model olivine feedstock materials. Carbonation was found to be a complex process associated with passivating silica layer formation, which includes the trapping of magnesite nanocrystals within the passivating silica layers, cracking and exfoliation of the layers, silica surface migration, olivine etch pit formation, transfer of the Mg and Fe in the olivine into the product carbonate, and the nucleation and growth of magnesite crystals on/in the silica/olivine reaction matrix. These phenomena occur in concert with the large solid volume changes that accompany the carbonation process, which can substantially impact carbonation reactivity. Passivating silica layer formation appears to play a major role in inhibiting carbonation reactivity. New approaches that can mitigate the effectiveness of passivating layer formation may offer intriguing potential to enhance carbonation reactivity and lower process cost.

M.J. McKelvy; H. Bearat; A.V.G. Chizmeshya; R. Nunez; R.W. Carpenter

2003-08-01

203

The role of epigenetic mechanisms and processes in autoimmune disorders  

PubMed Central

The lack of complete concordance of autoimmune disease in identical twins suggests that nongenetic factors play a major role in determining disease susceptibility. In this review, we consider how epigenetic mechanisms could affect the immune system and effector mechanisms in autoimmunity and/or the target organ of autoimmunity and thus affect the development of autoimmune diseases. We also consider the types of stimuli that lead to epigenetic modifications and how these relate to the epidemiology of autoimmune diseases and the biological pathways operative in different autoimmune diseases. Increasing our knowledge of these epigenetic mechanisms and processes will increase the prospects for controlling or preventing autoimmune diseases in the future through the use of drugs that target the epigenetic pathways.

Greer, Judith M; McCombe, Pamela A

2012-01-01

204

Process Mechanics of Low Plasticity Burnishing of Nitinol Alloy  

NASA Astrophysics Data System (ADS)

Nitinol alloys have received considerable attention in biomedical and aerospace applications. Surface integrity of Nitinol devices by various manufacturing processes is crucial for their functionality. Low plasticity burnishing (LPB) is very promising to modify surface integrity due to its unique capability to adjust material properties down to the deep subsurface on the order of a few millimeters. Burnishing mechanics is essential to understand its effect on surface properties. The depth and width of burnished surface materials are characterized. A three-dimensional finite element simulation has been developed to incorporate the superelastic mechanical behavior of Nitinol. The simulation predictions are validated with the experimental results. The contact stresses, residual stresses, and strain profiles are investigated to better understand burnishing mechanics.

Fu, C. H.; Guo, Y. B.; McKinney, J.; Wei, X. T.

2012-12-01

205

Formation of nanostructural materials induced by mechanical processings (overview)  

NASA Astrophysics Data System (ADS)

Mechanical alloying (MA) was firstly developed to synthesize metallic matrix composite by mechanically incorporating preformed oxide and or carbide particles into a metallic matrix. A compaction process is then applied to obtain bulk materials. During MA, powders are repeatedly welded, fractured and rewelded in a high-energy mill leading to an intimate mixing on a nano/micro-scale with the possible formation of far-from-equilibrium phases. The versatility of MA is well-known; high-volume, low-energy mills can be used to commercially produce dispersion-strengthened Al, Ni and other transition metal alloys. An overview of the dynamics of the process is presented to help gain a full appreciation of the industrial potential of the technique for synthesizing materials.

Gaffet, E.; Abdellaoui, M.; Malhouroux-Gaffet, N.

1995-02-01

206

Deployment Process, Mechanization, and Testing for the Mars Exploration Rovers  

NASA Technical Reports Server (NTRS)

NASA's Mar Exploration Rover (MER) robotic prospectors were produced in an environment of unusually challenging schedule, volume, and mass restrictions. The technical challenges pushed the system s design towards extensive integration of function, which resulted in complex system engineering issues. One example of the system's integrated complexity can be found in the deployment process for the rover. Part of this process, rover "standup", is outlined in this paper. Particular attention is given to the Rover Lift Mechanism's (RLM) role and its design. Analysis methods are presented and compared to test results. It is shown that because prudent design principles were followed, a robust mechanism was created that minimized the duration of integration and test, and enabled recovery without perturbing related systems when reasonably foreseeable problems did occur. Examples of avoidable, unnecessary difficulty are also presented.

Iskenderian, Ted

2004-01-01

207

Investigation of formation mechanisms of chips in orthogonal cutting process  

NASA Astrophysics Data System (ADS)

This work investigates the formation mechanisms of chips in orthogonal cutting of mild steel and the transformation conditions between various morphology chips. It is supposed that the modeling material follows the Johnson-Cook constitutive model. In orthogonal cutting process, both the plastic flow and the instability behaviors of chip materials are caused by the plane strain loadings. Therefore, the general instability behaviors of materials in plane strain state are first analyzed with linear perturbation method and a universal instability criterion is established. Based on the analytical results, the formation mechanisms of chips and the transformation conditions between continuous and serrated chips are further studied by instability phase diagram method. The results show that the chip formation strongly depends on the intensity ratios between shear and normal stresses. The ratios of dissipative rates of plastic work done by compression and shear stresses govern the transformation from continuous to serrated chips. These results are verified by the numerical simulations on the orthogonal cutting process.

Ma, W.

2012-08-01

208

The interplay between cell signaling and mechanics in developmental processes  

PubMed Central

Force and stress production within embryos and organisms are crucial physical processes that direct morphogenesis. In addition, there is mounting evidence that biomechanical cues created by these processes guide cell behaviors and cell fates. Here we review key roles for biomechanics during development to directly shape tissues, provide positional information for cell fate decisions, and enable robust programs of development. Several recently identified molecular mechanisms suggest how cells and tissues might coordinate their responses to biomechanical cues. Lastly, we outline long-term challenges in integrating biomechanics with genetic analysis of developing embryos.

Miller, Callie Johnson; Davidson, Lance

2014-01-01

209

Insight into the mechanisms of neuronal processing from electric fish.  

PubMed

Weakly electric fish use their electric fields to locate objects and communicate with each other. Their electric discharges vary with species, gender, and social status. This variation is mediated by steroid and peptide hormones that influence ion currents through changes in gene expression or phosphorylation state. Understanding how electric fish decode the perturbations of their electric fields that result from interactions with the discharges of other fish or prey is illuminating general mechanisms of neuronal processing. Their central sensory circuits are specialized to process amplitude modulated signals, to detect microsecond variations in spike timing, and are dynamically reconfigured depending on the stimulus parameters. PMID:14662377

Zakon, Harold H

2003-12-01

210

Ion-Exchange Processes and Mechanisms in Glasses  

Microsoft Academic Search

Leaching of alkalis from glass is widely recognized as an important mechanism in the initial stages of glass-water interactions. Pioneering experimental studies [1-3] nearly thirty-five years ago established that alkali (designated as M{sup +}) are lost to solution more rapidly than network-forming cations. The overall chemical reaction describing the process can be written as: {triple_bond}Si-O-M + H{sup +} â {triple_bond}Si-OH

B. P. McGrail; J. P. Icenhower; J. G. Darab; D. k. Shuh; D. R. Baer; V. Shutthanandan; S. Thevuthasan; M. H. Engelhard; J. L. Steele; E. A. Rodriguez; P. Liu; K. E. Ivanov; C. H. Booth; P. Nachimuthu

2001-01-01

211

A New Mechanism on Brain Information Processing - Energy Coding  

Microsoft Academic Search

\\u000a According to the experimental result of signal transmission with energetic demand tightly coupled to the information coding\\u000a in cerebral cortex and electric structural property in neuronal activities, we present a brand-new scientific theory with\\u000a mechanism of brain information processing. According to the new theory, we discover that neural coding under action of stimulation\\u000a in brain is complete with way of

Rubin Wang; Zhikang Zhang

2006-01-01

212

Mechanical and tribological properties of ion beam-processed surfaces  

Microsoft Academic Search

The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation

Kodali

1998-01-01

213

Dynamics of anticipatory mechanisms during predictive context processing  

PubMed Central

We employed an EEG paradigm manipulating predictive context to dissociate the neural dynamics of anticipatory mechanisms. Subjects either detected random targets or targets preceded by a predictive sequence of three distinct stimuli. The last stimulus in the 3-stimulus sequence (decisive stimulus) did not require any motor response but 100% predicted a subsequent target event. We show that predictive context optimizes target processing via the deployment of distinct anticipatory mechanisms at different times of the predictive sequence. Prior to the occurrence of the decisive stimulus, enhanced attentional preparation was manifested by reductions in the alpha oscillatory activities over visual cortices, resulting in facilitation of processing of the decisive stimulus. Conversely, the subsequent 100% predictable target event did not reveal deployment of attentional preparation in the visual cortices, but elicited enhanced motor preparation mechanisms, indexed by an increased contingent negative variation (CNV) and reduced mu oscillatory activities over motor cortices before movement onset. The present results provide evidence that anticipation operates via different attentional and motor preparation mechanisms by selectively pre-activating task-dependent brain areas as predictability gradually increases.

Bidet-Caulet, Aurelie; Barbe, Pierre-Guillaume; Roux, Sylvie; Viswanath, Humsini; Barthelemy, Catherine; Bruneau, Nicole; Knight, Robert T.; Bonnet-Brilhault, Frederique

2012-01-01

214

Mechanical and tribological properties of ion beam-processed surfaces  

NASA Astrophysics Data System (ADS)

A variety of surface modification and surface coating techniques are currently used in industry to modify the near-surface mechanical properties that influence the friction and wear behavior of metals, metallic alloys, ceramics, and polymers. Near-surface mechanical properties such as hardness and fracture toughness of a coating-substrate system can be tailored economically without changing the bulk properties of the system. The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) Investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation. (2) Characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation. (3) Developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. Wear mechanisms that occurred in implanted and unimplanted surfaces tested against AIS152100 steel were determined to be adhesive, abrasive, and third body wear. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness. The wear morphology of the coatings that were tested against a ruby slider suggested that abrasive wear, brittle fracture, and third body wear are the mechanisms by which loss of material can occur.

Kodali, Padma

215

Disappearance of Barrier Metal during Cu Chemical Mechanical Planarization Processing and Its Mechanism  

NASA Astrophysics Data System (ADS)

The bald disappearance of barrier metal had been observed on the wafer after Cu chemical mechanical planarization (CMP) processing. It was speculated that this phenomenon occurs because the excessively oxidized Ta by electrochemical reaction with Cu ion was removed more easily than the normal Ta oxide around it. The inhibition of the electrochemical reaction is necessary to solve this phenomenon.

Asano, Hiroshi; Yasui, Akihito; Hirano, Tatsuhiko; Tamai, Kazusei; Morinaga, Hitoshi

2011-05-01

216

[Analysis on mechanism of the chemical-biological flocculation process].  

PubMed

Zeta potential, particle size distribution and molecular weight distribution of dissolved TOC were studied to elementarily disclose the mechanism of the chemical-biological flocculation (CBF) process to treat municipal wastewater. Chemically enhanced primary treatment (CEPT) process and primary sedimentation tank process were taken as the parallel-compared wastewater treatment processes. The experimental results show that under the same dosage, Zeta potential of the CBF process effluent is equal to that of the CEPT process, which indicates that flocculant in return sludge does not change the stabilization of particles in CBF reactor, and the biological flocculation is the key reason for CBF is superior to CEPT. In CBF process, good removal results are achieved for particles >10 microm and dissolved TOC with molecular weight >6 ku by chemical dosage, and biological flocculation can not only promote the removal of particles >10 microm and dissolved TOC with molecular weight >6 ku, but also have high capacity to remove small particles and dissolved TOC with small molecular weight, with the results that particles >3 tpm are removed completely and TOC with molecular weight of 2-6 ku are removed by 42.5% . PMID:17633167

Zhang, Zhi-bin; Zhao, Jian-fu; Xia, Si-qing; Liu, Chang-qing; Wang, Xue-jiang

2007-05-01

217

Mechanical and tribological properties of ion beam-processed surfaces  

SciTech Connect

The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation; (2) characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation; and (3) developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness.

Kodali, P.

1998-01-01

218

Cotranslational processing mechanisms: towards a dynamic 3D model.  

PubMed

Recent major advances have been made in understanding how cotranslational events are achieved in the course of protein biosynthesis. Specifically, several studies have shed light into the dynamic process of how nascent chains emerging from the ribosome are supported by protein biogenesis factors to ensure both processing and folding mechanisms. To take into account the awareness that coordination is needed, a new 'concerted model' recently proposed simultaneous action of both processes on the ribosome. In the model, any emerging nascent chain is first encountered by the chaperone trigger factor (TF), which forms an open cradle underneath the ribosomal exit tunnel. This cradle serves as a passive router that channels the nascent chains to the first cotranslational event, the proteolysis event performed by the N-terminal methionine excision machinery. Although fascinating, this model clearly raises more questions than it answers. Does the data used to develop this model stand up to scrutiny and, if not, what are the alternative mechanisms that the data suggest? PMID:19647435

Giglione, Carmela; Fieulaine, Sonia; Meinnel, Thierry

2009-08-01

219

Mechanisms of folate losses during processing: diffusion vs. heat degradation.  

PubMed

Though folates are sensitive to heat treatments, leaching appears to be a major mechanism involved in folate losses in vegetables during processing. The aim of our study was to study folate diffusivity and degradation from spinach and green beans, in order to determine the proportion of each mechanism involved in folate losses. Folate diffusivity constant, calculated according to Fick's second law (Crank, 1975), was 7.4×10(-12) m(2)/s for spinach and 5.8×10(-10) m(2)/s for green beans, which is the same order of magnitude as for sugars and acids for each vegetable considered. Folate thermal degradation kinetics was not monotonous in spinach and green beans especially at 45 °C and did not follow a first order reaction. The proportion of vitamers changed markedly after thermal treatment, with a better retention of formyl derivatives. For spinach, folate losses were mainly due to diffusion while for green beans thermal degradation seemed to be preponderant. PMID:24679802

Delchier, Nicolas; Ringling, Christiane; Maingonnat, Jean-François; Rychlik, Michael; Renard, Catherine M G C

2014-08-15

220

Mechanisms of Carbon Nanotube Production by Laser Ablation Process  

NASA Technical Reports Server (NTRS)

We will present possible mechanisms for nanotube production by laser oven process. Spectral emission of excited species during laser ablation of a composite graphite target is compared with that of laser irradiated C60 vapor. The similarities in the transient and spectral data suggest that fullerenes are intermediate precursors for nanotube formation. The confinement of the ablation products by means of a 25-mm diameter tube placed upstream of the target seems to improve the production and purity of nanotubes. Repeated laser pulses vaporize the amorphous/graphitic carbon and possibly catalyst particles, and dissociate fullerenes yielding additional feedstock for SWNT growth.

Scott, Carl D.; Arepalli, Sivaram; Nikolaev, Pavel; Smalley, Richard E.; Nocholson, Leonard S. (Technical Monitor)

2000-01-01

221

The Mechanical Transient Process at Asynchronous Motor Oscillating Mode  

NASA Astrophysics Data System (ADS)

The research object is squirrel-cage asynchronous motor connected to single-phase sinusoidal. There are shown, that by connecting to the stator windings a certain sequence of half-period positive and negative voltage, a motor rotor is rotated, but three times slower than in the three-phase mode. Changing the connecting sequence of positive and negative half-period voltage to stator windings, motor can work in various oscillating modes. It is tested experimentally. The mechanical transient processes had been researched in rotation and oscillating modes.

Antonovi?s, Uldis; Bražis, Viesturs; Greivulis, J?nis

2009-01-01

222

Processing mechanics of alternate twist ply (ATP) yarn technology  

NASA Astrophysics Data System (ADS)

Ply yarns are important in many textile manufacturing processes and various applications. The primary process used for producing ply yarns is cabling. The speed of cabling is limited to about 35m/min. With the world's increasing demands of ply yarn supply, cabling is incompatible with today's demand activated manufacturing strategies. The Alternate Twist Ply (ATP) yarn technology is a relatively new process for producing ply yarns with improved productivity and flexibility. This technology involves self plying of twisted singles yarn to produce ply yarn. The ATP process can run more than ten times faster than cabling. To implement the ATP process to produce ply yarns there are major quality issues; uniform Twist Profile and yarn Twist Efficiency. The goal of this thesis is to improve these issues through process modeling based on understanding the physics and processing mechanics of the ATP yarn system. In our study we determine the main parameters that control the yarn twist profile. Process modeling of the yarn twist across different process zones was done. A computational model was designed to predict the process parameters required to achieve a square wave twist profile. Twist efficiency, a measure of yarn torsional stability and bulk, is determined by the ratio of ply yarn twist to singles yarn twist. Response Surface Methodology was used to develop the processing window that can reproduce ATP yarns with high twist efficiency. Equilibrium conditions of tensions and torques acting on the yarns at the self ply point were analyzed and determined the pathway for achieving higher twist efficiency. Mechanistic modeling relating equilibrium conditions to the twist efficiency was developed. A static tester was designed to zoom into the self ply zone of the ATP yarn. A computer controlled, prototypic ATP machine was constructed and confirmed the mechanistic model results. Optimum parameters achieving maximum twist efficiency were determined in this study. The successful results of this work have led to the filing of a US patent disclosing the method for producing ATP yarns with high yarn twist efficiency using a high convergence angle at the self ply point together with applying ply torque.

Elkhamy, Donia Said

223

Role of electron traps in the excitation and de-excitation mechanism of Yb(3+) in InP  

Microsoft Academic Search

An experimental study concerning the excitation mechanism of the Yb impurity in n- and p-type InP crystals was performed by the method of optically detected microwave-induced impact ionization. Based on the results it is argued that the Yb(3+) core excitation is intermediated by a nonradiative recombination of a bound exciton. A fingerprint of the existence of such an excitonic state

I. Tsimperidis; T. Gregorkiewicz; C. A. J. Ammerlaan; M. Godlewski; F. Scholz; B. Lambert

1995-01-01

224

Study on chemical mechanical polishing process of lithium niobate  

NASA Astrophysics Data System (ADS)

Chemical mechanical polishing of lithium niobate wafer in alkaline slurries has been investigated. In the lithium niobate CMP, the slurry was made by adding colloidal silica abrasive to de-ionized water. The effects of polishing plate speed, slurry flow rate, polishing pressure on removal rate in actual CMP process has been discussed in order to determine the optimum conditions for those parameters. The optimal slurry component is colloid SiO2, concentration SiO2:DW=1:1; KOH concentration 0.5~1.5% and surfactant 5~15ml/L. The process conditions are polishing plate speed 60rpm, polishing pressure 140KPa and slurry flow rate 120ml/min. The removal rate can reach 300nm/min and surface roughness is 0.21nm.

Wang, Shengli; Liu, Yuling; Li, Zhenxia

2007-12-01

225

Microwave quantum logic gates for trapped ions.  

PubMed

Control over physical systems at the quantum level is important in fields as diverse as metrology, information processing, simulation and chemistry. For trapped atomic ions, the quantized motional and internal degrees of freedom can be coherently manipulated with laser light. Similar control is difficult to achieve with radio-frequency or microwave radiation: the essential coupling between internal degrees of freedom and motion requires significant field changes over the extent of the atoms' motion, but such changes are negligible at these frequencies for freely propagating fields. An exception is in the near field of microwave currents in structures smaller than the free-space wavelength, where stronger gradients can be generated. Here we first manipulate coherently (on timescales of 20 nanoseconds) the internal quantum states of ions held in a microfabricated trap. The controlling magnetic fields are generated by microwave currents in electrodes that are integrated into the trap structure. We also generate entanglement between the internal degrees of freedom of two atoms with a gate operation suitable for general quantum computation; the entangled state has a fidelity of 0.76(3), where the uncertainty denotes standard error of the mean. Our approach, which involves integrating the quantum control mechanism into the trapping device in a scalable manner, could be applied to quantum information processing, simulation and spectroscopy. PMID:21833084

Ospelkaus, C; Warring, U; Colombe, Y; Brown, K R; Amini, J M; Leibfried, D; Wineland, D J

2011-08-11

226

Antibiotic Trapping by Plasmid-Encoded CMY-2 ?-Lactamase Combined with Reduced Outer Membrane Permeability as a Mechanism of Carbapenem Resistance in Escherichia coli  

PubMed Central

A liver transplant patient was admitted with cholangitis, for which meropenem therapy was started. Initial cultures showed a carbapenem-susceptible (CS) Escherichia coli strain, but during admission, a carbapenem-resistant (CR) E. coli strain was isolated. Analysis of the outer membrane protein profiles showed that both CS and CR E. coli lacked the porins OmpF and OmpC. Furthermore, PCR and sequence analysis revealed that both CS and CR E. coli possessed blaCTX-M-15 and blaOXA-1. The CR E. coli strain additionally harbored blaCMY-2 and demonstrated a >15-fold increase in ?-lactamase activity against nitrocefin, but no hydrolysis of meropenem was detected. However, nitrocefin hydrolysis appeared strongly inhibited by meropenem. Furthermore, the CMY-2 enzyme demonstrated lower electrophoretic mobility after its incubation either in vitro or in vivo with meropenem, indicative of its covalent modification with meropenem. The presence of the acyl-enzyme complex was confirmed by mass spectrometry. By transformation of the CMY-2-encoding plasmid into various E. coli strains, it was established that both porin deficiency and high-level expression of the enzyme were needed to confer meropenem resistance. In conclusion, carbapenem resistance emerged by a combination of elevated ?-lactamase production and lack of porin expression. Due to the reduced outer membrane permeability, only small amounts of meropenem can enter the periplasm, where they are trapped but not degraded by the large amount of the ?-lactamase. This study, therefore, provides evidence that the mechanism of “trapping” by CMY-2 ?-lactamase plays a role in carbapenem resistance.

van der Bij, Akke K.; van Boxtel, Ria; Pitout, Johann D. D.; van Ulsen, Peter; Melles, Damian C.; Tommassen, Jan

2013-01-01

227

Switching Oxide Traps  

NASA Technical Reports Server (NTRS)

We consider radiation-induced charge trapping in SiO2 dielectric layers, primarily from the point of view of CMOS devices. However, SiO2 insulators are used in many other ways, and the same defects occur in other contexts. The key studies, which determined the nature of the oxide charge traps, were done primarily on gate oxides in CMOS devices, because that was the main radiation problem in CMOS at one time. There are two major reviews of radiation-induced oxide charge trapping already in the literature, which discuss the subject in far greater detail than is possible here. The first of these was by McLean et al. in 1989, and the second, ten years later, was intended as an update, because of additional, new work that had been reported. Basically, the picture that has emerged is that ionizing radiation creates electron-hole pairs in the oxide, and the electrons have much higher mobility than the holes. Therefore, the electrons are swept out of the oxide very rapidly by any field that is present, leaving behind any holes that escape the initial recombination process. These holes then undergo a polaron hopping transport toward the Si/SiO2 interface (under positive bias). Near the interface, some fraction of them fall into deep, relatively stable, long-lived hole traps. The nature and annealing behavior of these hole traps is the main focus of this paper.

Oldham, Timothy R.

2003-01-01

228

Thermoelectrically cooled water trap  

DOEpatents

A water trap system based on a thermoelectric cooling device is employed to remove a major fraction of the water from air samples, prior to analysis of these samples for chemical composition, by a variety of analytical techniques where water vapor interferes with the measurement process. These analytical techniques include infrared spectroscopy, mass spectrometry, ion mobility spectrometry and gas chromatography. The thermoelectric system for trapping water present in air samples can substantially improve detection sensitivity in these analytical techniques when it is necessary to measure trace analytes with concentrations in the ppm (parts per million) or ppb (parts per billion) partial pressure range. The thermoelectric trap design is compact and amenable to use in a portable gas monitoring instrumentation.

Micheels, Ronald H. (Concord, MA)

2006-02-21

229

Significant improvement of trapped flux in bulk Gd-Ba-Cu-O grains fabricated by a modified top-seeded melt growth process  

NASA Astrophysics Data System (ADS)

The seeded infiltration and growth of Gd-Ba-Cu-O single grains using a YBa2Cu3Oy pressed pellet as the liquid source has successfully solved the liquid source leakage problem even at Tmax ˜ 1100?°C. As a development of this process, a simple but essential modification to insert a liquid source pellet at the bottom of the pre-form was made to the top-seeded melt growth process. The present method resulted in a significant enhancement of the trapped flux density of the Gd-Ba-Cu-O grains. In the growth kinetics, we interpreted that the enriched liquid source surrounding the growth front leads to a more uniform distribution of Gd2BaCuO5 in the matrix and an enlarged c-orientation growth area, which help suppress the formation of high angle grain boundaries. Furthermore, we demonstrated that the present method is of great advantage in multi-seeded processes.

Zhou, Difan; Hara, Shogo; Li, Beizhan; Xu, Kun; Noudem, Jacques; Izumi, Mitsuru

2013-01-01

230

Development of brain mechanisms for processing affective touch  

PubMed Central

Affective tactile stimulation plays a key role in the maturation of neural circuits, but the development of brain mechanisms processing touch is poorly understood. We therefore used functional magnetic resonance imaging (fMRI) to study brain responses to soft brush stroking of both glabrous (palm) and hairy (forearm) skin in healthy children (5–13 years), adolescents (14–17 years), and adults (25–35 years). Adult-defined regions-of-interests in the primary somatosensory cortex (SI), secondary somatosensory cortex (SII), insular cortex and right posterior superior temporal sulcus (pSTS) were significantly and similarly activated in all age groups. Whole-brain analyses revealed that responses in the ipsilateral SII were positively correlated with age in both genders, and that responses in bilateral regions near the pSTS correlated significantly and strongly with age in females but not in males. These results suggest that brain mechanisms associated with both sensory-discriminative and affective-motivational aspects of touch are largely established in school-aged children, and that there is a general continuing maturation of SII and a female-specific increase in pSTS sensitivity with age. Our work establishes a groundwork for future comparative studies of tactile processing in developmental disorders characterized by disrupted social perception such as autism.

Bjornsdotter, Malin; Gordon, Ilanit; Pelphrey, Kevin A.; Olausson, Hakan; Kaiser, Martha D.

2014-01-01

231

Processing, mechanical properties and microfractography of polymer concrete composite material  

SciTech Connect

Mechanical properties of methyl methacrylate (MMA)-based polymer concrete (PC) were studied by means of various mechanical tests and microscopic observation. It was found that the casting and curing process is one of the most important factors influencing the strength of PC. Since the compressive strength of PC gives a general indication of its overall quality, and since PC materials are likely to be utilized mainly as compressive members, performance and evaluation of compression tests were emphasized. It was found that the compressive strength is directly proportional to the logarithm of loading rate. The compressive strength increased rapidly with curing time, The compressive strength increased with decreasing H/D (height/diameter) ratio of the specimen. The compressive strength of MMA based PC increased linearly with increasing hardness (Rockwell-K scale, R/sub K/). This linear correlation was found to be independent of the casting process and curing time. Tension-tension fluctuating fatigue tests were performed to determine the behavior of PC under repeated loading. In fatigue tests with a maximum tension less than 50% of the ultimate tensile strength, failure did not occur even after 10/sup 7/ cycles. The cracking pattern of PC is noticeably different from that of regular portland cement concrete.

Kim, K.

1986-01-01

232

A facile access to polyfunctional oxygen-containing heterocycles via intramolecularly formed protic oxonium ylide trapping processes.  

PubMed

Based on the assumption that intramolecularly formed protic oxonium ylides could be trapped by electrophiles, transition-metal-catalyzed reactions of diazoesters bearing a primary hydroxy group with electron-deficient aldehydes and isatins were examined. Good to high chemo- and diastereoselectivities were achieved with reactions catalyzed by Cu(hfacac)2. The reactions were assumed to occur via tandem intramolecular protic oxonium ylide formation and subsequent aldol-type addition. They not only provided an efficient entry to 3-substituted 1,4-dioxan-2-one heterocycles with at least one quaternary carbon center but also provided experimental evidence for a stepwise pathway for the transition-metal-catalyzed intramolecular O-H insertion of diazo compounds. PMID:24203678

Guo, Xin; Liu, Wei; Hu, Wenhao

2014-01-01

233

Trapping and cooling of 174Yb+ ions in a microfabricated surface trap  

NASA Astrophysics Data System (ADS)

Trapped atomic ions are the leading candidate to act as individual quantum bits in a large quantum information processing system. Ion traps can be conformed to a two-dimensional surface, which provides a way to increase the number of ions while maintaining the ability to move individual ions in a two-dimensional grid. However, surface traps tend to suffer from shallow trap depths and higher motional heating rates. In this work, we report the design, fabrication, and testing of a simple gold-on-fused-silica ion trap optimized for a deep trapping potential and stable motional modes. The desirable trap characteristics include long lifetime, fully-compensated micromotion, and high secular trap frequencies that were measured using a trapped and cooled 174Yb+ ion. This trap design can be integrated with an optical cavity to enhance the ion-photon coupling.

Noek, Rachel; Kim, Taehyun; Mount, Emily; Baek, So-Young; Maunz, Peter; Kim, Jungsang

2013-08-01

234

Experiments with an ion-neutral hybrid trap: cold charge-exchange collisions  

NASA Astrophysics Data System (ADS)

Due to their large trap depths (˜1 eV or 10,000 K), versatility, and ease of construction, Paul traps have important uses in high-resolution spectroscopy, plasma physics, and precision measurements of fundamental constants. An ion-neutral hybrid trap consisting of two separate but spatially concentric traps [a magneto-optic trap (MOT) for the neutral species and a mass-selective linear Paul trap for the ionic species] is an ideal apparatus for sympathetic cooling. However, over the past few years, hybrid traps have proven most useful in measuring elastic and charge-exchange rate constants of ion-neutral collisions over a wide temperature range from kilo-Kelvin to nano-Kelvin. We report some initially surprising results from a hybrid trap system in our laboratory where we have loaded the Paul trap with Ca+ ions in the presence of a Na MOT (localized dense gas of cold Na atoms). We find a strong loss of Ca+ ions with MOT exposure, attributed to an exothermic, non-resonant ion-neutral charge-exchange process with an activation barrier, which leads to the formation of Na+ ions. We propose a detailed mechanism for this process. We obtain an estimated measure of the rate constant for this charge exchange of ˜2 × 10-11 cm3/s, much less than the Langevin rate, which suggests that the Langevin assumption of unit efficiency in the reaction region is not correct in this case.

Smith, W. W.; Goodman, D. S.; Sivarajah, I.; Wells, J. E.; Banerjee, S.; Côté, R.; Michels, H. H.; Mongtomery, J. A.; Narducci, F. A.

2014-01-01

235

Injection into electron plasma traps  

SciTech Connect

Computational studies and experimental measurements of plasma injection into a Malmberg-Penning trap reveal that the number of trapped particles can be an order of magnitude higher than predicted by a simple estimates based on a ballistic trapping model. Enhanced trapping is associated with a rich nonlinear dynamics generated by the space-charge forces of the evolving trapped electron density. A particle-in-cell simulation is used to identify the physical mechanisms that lead to the increase in trapped electrons. The simulations initially show strong two-stream interactions between the electrons emitted from the cathode and those reflected off the end plug of the trap. This is followed by virtual cathode oscillations near the injection region. As electrons are trapped, the initially hollow longitudinal phase-space is filled, and the transverse radial density profile evolves so that the plasma potential matches that of the cathode. Simple theoretical arguments are given that describe the different dynamical regimes. Good agreement is found between simulation and theory.

Gorgadze, Vladimir; Pasquini, Thomas A.; Fajans, Joel; Wurtele, Jonathan S.

2003-12-02

236

Hydro-Thermo-Mechanical Processes Along Faults During Seismic Slip  

NASA Astrophysics Data System (ADS)

Field observations of maturely slipped faults show a generally broad zone of damage by cracking and granulation, but nevertheless suggest that shear in individual earthquakes takes place with extreme localization to a long-persistent slip zone, < 1-5 mm wide, within a finely granulated, ultracataclastic fault core. Relevant fault weakening processes during large crustal events are therefore likely to be thermal and, given the damage zones and geologic evidence of water-rock interactions within them, it seems reasonable to assume fluid presence. It is thus proposed that the two primary dynamic weakening mechanisms during seismic slip, both of which are expected to be active in at least the early phases of nearly all crustal events, are (1) Flash heating at highly stressed frictional micro-contacts, and (2) Thermal pressurization of fault-zone pore fluid. Both have characteristics which promote extreme localization of shear. At sufficiently large slip, macroscopic melting will occur in cases for which those processes have not efficiently enough reduced heat generation, and thus limited temperature rise, and, in silica-rich lithologies, formation of a gel-like layer may contribute to weakening at large slip too. Theoretical modeling of mechanisms (1) and (2) has been constrained with lab-determined hydrologic and poroelastic properties of fault core material and high-speed friction studies and, within considerable uncertainties in interpretation, seismic data on the fracture energy of earthquakes and its variation with slip in the events can be plausibly described by the predictions (Rice & Cocco, Dahlem Conf. in press; Rice, JGR, 2006; Rempel &Rice, JGR, 2006). Those mechanisms suggest that faults may be statically strong but are dynamically weak under typical seismic conditions. Another robust source of dynamic weakening, at least in mode II slip, comes from contrast across the fault of elastic stiffness and density of the bordering crustal rock, and it has recently been shown (Rudnicki &Rice, JGR, 2006) that contrast across the fault of permeability and poroelastic properties within fluid-saturated damage fringes along the fault walls has an analogous effect. Both allow for reductions of effective normal stress during suitably directed non-uniform slip like at a rupture front, although the "preferred" rupture direction based on one effect may either align with or oppose that based on the other. A brief summary will be presented of results on the numerical elastodynamics of propagating rupture based on the hydro- and thermo-mechanical processes described. That is work with H. Noda and E. Dunham (this AGU meeting) based on fault constitutive laws which simultaneously embody mechanisms (1) and (2) with lab-justified material parameters, and with E. Dunham (this AGU meeting) on assuming permeability and poroelastic dissimilarity in damage fringes along the fault, together with possible larger scale crustal rock dissimilarity.

Rice, J. R.

2006-12-01

237

Association between central auditory processing mechanism and cardiac autonomic regulation  

PubMed Central

Background This study was conducted to describe the association between central auditory processing mechanism and the cardiac autonomic regulation. Methods It was researched papers on the topic addressed in this study considering the following data bases: Medline, Pubmed, Lilacs, Scopus and Cochrane. The key words were: “auditory stimulation, heart rate, autonomic nervous system and P300”. Results The findings in the literature demonstrated that auditory stimulation influences the autonomic nervous system and has been used in conjunction with other methods. It is considered a promising step in the investigation of therapeutic procedures for rehabilitation and quality of life of several pathologies. Conclusion The association between auditory stimulation and the level of the cardiac autonomic nervous system has received significant contributions in relation to musical stimuli.

2014-01-01

238

Evidence of Mechanically Activated Processes in Slow Granular Flows  

NASA Astrophysics Data System (ADS)

We study how a shear band in a granular medium dramatically changes the mechanical behavior of the material further in the non sheared region. To this end, we carry out a microrheology experiment, where a constant force F is applied to a small rod immersed outside the shear band. In the absence of a shear band, a critical force Fc is necessary to move the intruder. When a shear band exists, the intruder moves even for a force F less than the critical force Fc. We systematically study how the creep velocity Vcreep of the rod varies with Fc-F and with the distance to the shear band, and show that the behavior can be described by an Eyring-like activated process.

Reddy, K. A.; Forterre, Y.; Pouliquen, O.

2011-03-01

239

Mechanism of Action of a Palladium Modifier on Atomization Processes  

NASA Astrophysics Data System (ADS)

We have demonstrated a desorption mechanism for dissipation of palladium from a palladium modifier in a graphite furnace during sample atomization. We have carried out mathematical modeling with the aim of obtaining the most important kinetic parameters of the atomization processes: diffusion rate and energy of formation of free atoms. The energy of formation of free silver atoms in the presence of palladium, calculated from the shape of the signals, increases from 118.5 ± 6.3 to 199.5 ± 8.4 kJ/mol, while the activation energy for diffusion of silver in the graphite of the furnace walls increases from 75.6 ± 1.1 to 135.2 ± 6.0 kJ/mol, which suggests direct chemical reaction between palladium and silver.

Rogulsky, Yu. V.; Illiashenko, V. Yu.; Kulik, A. N.

2014-01-01

240

Formal mechanization of device interactions with a process algebra  

NASA Technical Reports Server (NTRS)

The principle emphasis is to develop a methodology to formally verify correct synchronization communication of devices in a composed hardware system. Previous system integration efforts have focused on vertical integration of one layer on top of another. This task examines 'horizontal' integration of peer devices. To formally reason about communication, we mechanize a process algebra in the Higher Order Logic (HOL) theorem proving system. Using this formalization we show how four types of device interactions can be represented and verified to behave as specified. The report also describes the specification of a system consisting of an AVM-1 microprocessor and a memory management unit which were verified in previous work. A proof of correct communication is presented, and the extensions to the system specification to add a direct memory device are discussed.

Schubert, E. Thomas; Levitt, Karl; Cohen, Gerald C.

1992-01-01

241

Qualitative Assessment of Flow and Transport Mechanisms in Bioremediation Processes  

NASA Astrophysics Data System (ADS)

Recent studies suggest that time-lapse crosshole geophysical methods may be effective in monitoring subsurface hydrological and biochemical mechanisms. These methods have potential to provide a minimally invasive, cost-effective, high resolution, field relevant means to gain information previously limited to wellbore data. Our study area is located at a DOE Hanford site, an area heavily polluted with toxic chromate. Time- lapse crosshole seismic and radar data sets have been collected in order to monitor spatio-temporal responses to these processes. Before using these data for parameter estimation and monitoring hydrobiogeochemical processes, we need to 1) identify the critical parameters involved in these processes; 2) determine the sensitivity of seismic/radar responses to these parameters; and 3) choose the most appropriate forward modeling approach for forward and inverse modeling. In this study, we treat critical parameters (e.g., hydraulic conductivity, flow rate, and the dispersion coefficients) as random variables, which can be described by their probabilistic density distributions. Then we adopt stochastic sampling method within the Minimum relative entropy (MRE) framework to generate many realistic models based on the welllog data. From here, the geophysical (crosshole seismic and radar) responses are computed using different forward models to study the sensitivity of the responses to those aforementioned parameters, and the performances of the different forward modeling approaches are compared. Finally, geophysical data are used for hydrobiogeochemical parameter estimation through Bayesian inverse modeling. Our study provides guidance on favorable situations in which borehole geophysical data can be effectively used for monitoring subsurface hydrobiogeochemical processes.

Terry, N.; Hou, Z.

2008-12-01

242

Penning trap mass measurements of {sup 99-109}Cd with the ISOLTRAP mass spectrometer, and implications for the rp process  

SciTech Connect

Penning trap mass measurements of neutron-deficient Cd isotopes {sup 99-109}Cd have been performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN, all with relative mass uncertainties below 3{center_dot}10{sup -8}. A new mass evaluation has been performed. The mass of {sup 99}Cd has been determined for the first time, which extends the region of accurately known mass values toward the doubly magic nucleus {sup 100}Sn. The implication of the results on the reaction path of the rp process in stellar x-ray bursts is discussed. In particular, the uncertainty of the abundance and the overproduction created by the rp-process for the mass A=99 are demonstrated by reducing the uncertainty of the proton-separation energy of {sup 100}InS{sub p}({sup 100}In) by a factor of 2.5.

Breitenfeldt, M.; Schweikhard, L. [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet, D-17487 Greifswald (Germany); Audi, G.; Lunney, D.; Naimi, S. [CSNSM-IN2P3-CNRS, F-91405 Orsay-Campus (France); Beck, D.; Herfurth, F. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Planckstrasse 1, D-64291 Darmstadt (Germany); Blaum, K. [Max-Planck-Institut fuer Kernphysik, D-69117 Heidelberg (Germany); Ruprecht-Karls-Universitaet, Institut fuer Physik, D-69120 Heidelberg (Germany); George, S. [Max-Planck-Institut fuer Kernphysik, D-69117 Heidelberg (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet, D-55128 Mainz (Germany); Herlert, A.; Kowalska, M. [CERN, Physics Department, 1211 Geneva 23 (Switzerland); Kellerbauer, A. [Commission of the European Communities, Joint Research Center, European Institute for Transuranium Elements, D-76125 Karlsruhe (Germany); Kluge, H.-J. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Planckstrasse 1, D-64291 Darmstadt (Germany); Ruprecht-Karls-Universitaet, Institut fuer Physik, D-69120 Heidelberg (Germany); Neidherr, D. [Institut fuer Physik, Johannes Gutenberg-Universitaet, D-55128 Mainz (Germany); Schatz, H. [NSCL, Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824 (United States); Schwarz, S. [NSCL, Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States)

2009-09-15

243

Mechanical properties of iron processed by severe plastic deformation  

NASA Astrophysics Data System (ADS)

In the present study, the mechanical properties of Fe processed via severe plastic deformation (equal-channel angular pressing (ECAP)) at room temperature were investigated for the first time. The grain size of annealed Fe, with an initial grain size of about 200 µm, was reduced drastically during ECAP. After eight passes, the grain size reaches 200 to 400 nm, as documented by means of transmission electron microscopy (TEM). The value of microhardness during pressing increases 3 times over that of the starting material after the first pass and increases slightly during subsequent pressing for higher-purity Fe. Examination of the value of microhardness after eight passes as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization, an observation that resembles the behavior reported for heavily deformed metals and alloys. The tensile and compression behaviors were examined. In tension, a drop in the engineering stress-engineering strain curve beyond maximum load was observed both in the annealed Fe and the ECAP Fe. This drop is related to the neck deformation. The fracture surface, examined by scanning electron microscopy (SEM), shows vein patterns, which is different from the dimples found on the fracture surface of annealed Fe. In compression, an initial strain-hardening region followed by a no-strain-hardening region was observed in the ECAP Fe. The yield strength in tension of the ECAP Fe was observed to be higher than that in compression. The strengthening mechanisms and softening behavior are discussed.

Han, Bing Q.; Mohamed, Farghalli A.; Lavernia, Enrique J.

2003-01-01

244

[Mechanisms of enkephalin action on learning and memory processes].  

PubMed

The influence of enkephalin on the processes of elaboration and preservation of the defensive conditioned reflexes of bilateral avoidance (CRBA) and conditioned reflexes of passive avoidance (CRPA) in intact rats and animals with changed functional state of serotoninergic system of the brain has been examined. Injection of enkephalin in dose of 10 mkg to intact animals accelerated the elaboration of CRBA not influencing in this case their preservation, but deeply disturbed the CRPA preservation. The excess of serotonin in the brain created by means of 5-oxytryptophan fully prevented the acceleration of CRBA elaboration by enkephalin under the usual conditions. Injection of enkephalin at the background of serotonin lowering and raising in the brain favoured CRBA preservation. Under the enkephalin influence the inclusion of [3H]tyrosine and [14C]lisine in water-soluble and water-insoluble proteins of different cerebral structures lowered. The obtained data testify to participation of serotoninergic system and brain proteins in the mechanisms of enkephalin action to the processes of learning and memory. PMID:6335051

Kruglikov, R I; Chippens, G I; Getsova, V M; Iushin, V A; Mats, V N

1984-01-01

245

Codeformation processing of mechanically-dissimilar metal/intermetallic composites  

NASA Astrophysics Data System (ADS)

A systematic and scientific approach has been applied to the study of codeformation processing. A series of composites having mechanically-dissimilar phases were developed in which the high temperature flow behavior of the reinforcement material could be varied independent of the matrix. This was accomplished through the use of a series of intermetallic matrix composites (IMCs) as discontinuous reinforcements in an otherwise conventional metal matrix composite. The IMCs are produced using an in-situ reaction synthesis technique, called the XD(TM) process. The temperature of the exothermic synthesis reaction, called the adiabatic temperature, has been calculated and shown to increase with increasing volume percentage of TiB2 reinforcement. Further, this temperature has been shown to effect the size and spacing of the TiB2, microstructural features which are often used in discontinuous composite strength models. Study of the high temperature flow behavior of the components of the metal/IMC composite is critical to the development of an understanding of codeformation. A series of compression tests performed at 1000° to 1200°C and strain-rates of 10-3 and 10-4 sec-1. Peak flow stresses were used to evaluate the influence of material properties and process conditions. These data were incorporated into phenomenologically-based constitutive equations that have been used to predict the flow behavior. It has been determined that plastic deformation of the IMCs occurs readily, and is largely TiB2 independent, at temperatures approaching the melting point of the intermetallic matrices. Ti-6Al-4V/IMC powder blends were extruded at high temperatures to achieve commensurately deformed microstructures. The results of codeformation processing were analyzed in terms of the plastic strain of the IMC particulates. IMC particle deformation was shown to increase with increasing IMC particle size, volume percentage of IMC, extrusion temperature, homologous temperature, extrusion strain-rate, and decreasing TiB2 reinforcement within the IMCs. A series of finite element models were developed to simulate codeformation processing via the extrusion of a discontinuously-reinforced composite. The results were evaluated through comparison between average equivalent strain in matrix and reinforcement elements. These results show that codeformation should increase with increasing volume percentage of IMC, homologous temperature, volume percentage of IMC, and decreasing IMC particle size. With the exception of the particle size, these results correlate to those of the experimental extrusion analysis.

Marte, Judson Sloan

246

Steam trap monitor  

DOEpatents

A steam trap monitor positioned downstream of a steam trap in a closed steam system includes a first sensor (the combination of a hot finger and thermocouple well) for measuring the energy of condensate and a second sensor (a cold finger) for measuring the total energy of condensate and steam in the line. The hot finger includes one or more thermocouples for detecting condensate level and energy, while the cold finger contains a liquid with a lower boiling temperature than that of water. Vapor pressure from the liquid is used to do work such as displacing a piston or bellows in providing an indication of total energy (steam+condensate) of the system. Processing means coupled to and responsive to outputs from the thermocouple well hot and cold fingers subtracts the condensate energy as measured by the hot finger and thermocouple well from the total energy as measured by the cold finger to provide an indication of the presence of steam downstream from the trap indicating that the steam trap is malfunctioning.

Ryan, Michael J. (Plainfield, IL)

1988-01-01

247

Ohmic contacts for wide bandgap semiconductors: Processing, properties and mechanisms  

NASA Astrophysics Data System (ADS)

Stable Ohmic contacts are essential for reliable operation of wide bandgap semiconductor electronic and optoelectronic devices. Such contacts have been made to molecular beam epitaxy (MBE) grown n-type and p-type ZnSe on (100) semi-insulating GaAs substrates and metalorganic chemical vapor deposition (MOCVD) grown p-type GaN on (0001) sapphire substrates. Various metals have been deposited by thermal evaporation and annealing techniques at different temperatures. Chemical etching and cleaning, plasma treatment using reactive ion etching (RIE), and cryogenic treatment in liquid nitrogen have been studied. Ion implantation was also performed to obtain highly doped materials. The electrical characteristics for the contacts were examined by the current versus voltage data and the specific contact resistance was determined by use of the transmission line method (TLM) for II-VI n-type and p-type ZnSe and the circular transmission line method (c-TLM) for III-V p-type GaN, respectively. Contacts formed by In/Au to n-type ZnSe and Cu/Au to p-type ZnSe showed the lowest specific contact resistance values of 1.04 x 10--2 Ocm2 and 1.67 x 10--1 Ocm 2, respectively. A nitrogen plasma treatment of the ZnSe surface prior to metallization was proven to lower the contact resistance to p-type ZnSe. Two different current flow mechanisms involving thermionic emission and thermionic field emission were shown for the Cu/Au contact to low doped p-ZnSe (1 x 1017 cm--3) and three involving thermionic emission, thermionic field emission, and tunneling for the Mg/Au contact to highly doped n-ZnSe (1.15 x 1019 cm--3). MOCVD grown p-type Mg-doped GaN with hole concentration of 1.41 x 1017 cm--3 was used to study Ohmic contacts to p-type GaN. The effects of the cryogenic process on improving Ohmic behavior (I-V linearity) and reducing the specific contact resistance were investigated and may result from a combination of the improved surface morphology and the recrystallizing of new compounds such as NiO and Au:Pd solid solution. The I-V-T measurement for both contacts had similar behavior and closely fit thermionic field emission current mechanisms with little deviation but dominant transport mechanisms were not clear since the contacts were practically Ohmic. (Abstract shortened by UMI.)

Park, Mi-Ran

248

Mechanical Properties, Corrosion Resistance, and Microstructural Changes during Friction Stir Processing of 5083 Aluminum Rolled Plates  

Microsoft Academic Search

Friction stir processing is a solid-state process to modify microstructure and mechanical properties of sheet metals and as-cast materials. In this process, stirring action of the tool causes the material to intense plastic deformation that yields a dynamic recrystallization. In this study, the effect of friction stir processing (FSP) and process parameters on microstructure, mechanical properties, wear resistance, and corrosion

R. Abdi Behnagh; M. K. Besharati Givi; M. Akbari

2012-01-01

249

Soil Activated Trap Door Dibble.  

National Technical Information Service (NTIS)

The device is adapted for use in mechanized plant setting machines used in the agricultural industry. A dibble, formed by a u-shaped channel, utilizing a hinged pressure plate which, upon contact with the ground, mechanically opens a trap door within the ...

W. Moden T. Chappell W. L. DeWitt

1977-01-01

250

Steam-trap capacities  

Microsoft Academic Search

Factors that affect steam-trap capacity are listed and include: trap inlet pressure, trap discharge pressure, subcooling of inlet condensate, static head of condensate on trap, design of the trap, design of the piping. Some of the things that a user might look for in a steam pipe are examined: low installed cost, low maintenance cost, low cost of owning, and

1985-01-01

251

Parental effects in ecology and evolution: mechanisms, processes and implications  

PubMed Central

As is the case with any metaphor, parental effects mean different things to different biologists—from developmental induction of novel phenotypic variation to an evolved adaptation, and from epigenetic transference of essential developmental resources to a stage of inheritance and ecological succession. Such a diversity of perspectives illustrates the composite nature of parental effects that, depending on the stage of their expression and whether they are considered a pattern or a process, combine the elements of developmental induction, homeostasis, natural selection, epigenetic inheritance and historical persistence. Here, we suggest that by emphasizing the complexity of causes and influences in developmental systems and by making explicit the links between development, natural selection and inheritance, the study of parental effects enables deeper understanding of developmental dynamics of life cycles and provides a unique opportunity to explicitly integrate development and evolution. We highlight these perspectives by placing parental effects in a wider evolutionary framework and suggest that far from being only an evolved static outcome of natural selection, a distinct channel of transmission between parents and offspring, or a statistical abstraction, parental effects on development enable evolution by natural selection by reliably transferring developmental resources needed to reconstruct, maintain and modify genetically inherited components of the phenotype. The view of parental effects as an essential and dynamic part of an evolutionary continuum unifies mechanisms behind the origination, modification and historical persistence of organismal form and function, and thus brings us closer to a more realistic understanding of life's complexity and diversity.

Badyaev, Alexander V.; Uller, Tobias

2009-01-01

252

Part III. (4) Mechanical and Thermal Processes of Initiation  

Microsoft Academic Search

The sensitiveness of initiators to mechanical action has been examined in relation to heat, for lead azide, mercury fulminate, and in some cases lead styphnate, in order to see how far mechanical action could be equated with local heating. Previous information on mechanical sensitiveness has been extended by measuring friction sensitiveness with grit of varying hardness, and by varying the

A. R. Ubbelohde

1948-01-01

253

Chemical processes in the chemical mechanical polishing of copper  

Microsoft Academic Search

The mechanisms by which removal and planarization occur during the chemical mechanical polishing (CMP) of copper, used for pattern delineation in a multilevel metallization scheme, are investigated in this paper. We propose that removal occurs as mechanical abrasion of the surface followed by chemical dissolution of the abraded species. Planarization is achieved by the use of a rigid polishing pad

J. M. Steigerwald; S. P. Murarka; R. J. Gutmann; D. J. Duquette

1995-01-01

254

Bullet Trap User's Guide.  

National Technical Information Service (NTIS)

This Bullet Trap User's Guide provides range management professionals with direction for choosing, installing, and maintaining bullet traps to solve metal migration, erosion, or safety problems on their outdoor small arms ranges. Bullet traps provide envi...

1996-01-01

255

Trapping ions in a segmented ring trap  

NASA Astrophysics Data System (ADS)

We demonstrate robust trapping in an ion trap which has a ring shaped RF node. Ions are back-side loaded through a small 10 ?m diameter loading hole and we have demonstrated thousands of complete circuits around the trap. Each circuit passes through 44 trapping zones; the trap has 89 independent DC control electrodes. Measurements of the tangential secular frequency indicate a weak dependence on the RF and the loading hole. The ion trap is fabricated using four metal layers, allowing for the inner islanded electrodes to be electrically routed underneath the trap with negligible effects on the trapped ions. [4pt] This work was supported by the Intelligence Advanced Research Projects Activity (IARPA). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Tabakov, B. P.; Sterk, J. D.; Benito, F.; Haltli, R.; Tigges, C. P.; Stick, D.; Blain, M. G.; Moehring, D. L.

2012-06-01

256

Characterization of Mechanical Properties of Aluminum Processed by Repetitive Corrugation and Straightening Process using Taguchi Analysis  

NASA Astrophysics Data System (ADS)

The severe plastic deformation process is capable of developing the submicron grain structures in metallic alloys and to improve the mechanical properties. Repetitive corrugation and straightening (RCS) processes are widely used in industries to compensate the high-strength metal plates components used in automobiles. In this work, an attempt has been made to study the influence of RCS parameters like strain rate, number of passes, and plate thickness to produce grain refinement in metallic alloys. Experiments were based on the Taguchi method and the analysis of variance (ANOVA) technique was an effective tool to predict the degree of importance of the RCS parameters on grain size, microhardness, and tensile strength of RCS specimens. The results indicated that the number of passes has a major influence on the fine-grain refinement, followed by Al plate thickness and strain rate.

Siddesha, H. S.; Shantharaja, M.

2013-02-01

257

Micromachined Dust Traps  

NASA Technical Reports Server (NTRS)

Micromachined traps devised to capture dust particles for analysis without contaminating them. Based on micromachined structures retaining particles, rather than adhesives or greases interfering with scanning-electron-microscope analysis or x-ray imaging. Unlike maze traps and traps enmeshing particles in steel wool or similar materials, micromachined traps do not obscure trapped particles. Internal geometries of traps range from simple cones to U-shapes, all formed by etching silicon.

Bearman, Gregory H.; Bradley, James G.

1993-01-01

258

CO2-ECBM related coupled physical and mechanical transport processes  

NASA Astrophysics Data System (ADS)

The interrelation of cleat transport processes and mechanical properties was investigated by permeability tests at different stress levels (60% to 130% of in-situ stress) with sorbing (CH4, CO2) and inert gases (N2, Ar, He) on a subbituminous A coal from the Surat Basin, Queensland Australia (figure). From the flow tests under controlled triaxial stress conditions the Klinkenberg-corrected "true" permeability coefficients and the Klinkenberg slip factors were derived. The "true"-, absolute or Klinkenberg-corrected permeability depends on gas type. Following the approach of Seidle et al. (1992) the cleat volume compressibility (cf) was calculated from observed changes in apparent permeability upon variation of external stress (at equal mean gas pressures). The observed effects also show a clear dependence on gas type. Due to pore or cleat compressibility the cleat aperture decreases with increasing effective stress. Vice versa, with increasing mean pore pressure at lower confining pressure an increase in permeability is observed, which is attributed to a widening of cleat aperture. Non-sorbing gases like helium and argon show higher apparent permeabilities than sorbing gases like methane and CO2. Permeability coefficients measured with successively increasing mean gas pressures were consistently lower than those determined at decreasing mean gas pressures. The kinetics of matrix transport processes were studied by sorption tests on different particle sizes at various moisture contents and temperatures (cf. Busch et al., 2006). Methane uptake rates were determined from the pressure decline curves recorded for each particle-size fraction, and "diffusion coefficients" were calculated using several unipore and bidisperse diffusion models. While the CH4 sorption capacity of moisture-equilibrated coals was significantly lower (by 50%) than that of dry coals, no hysteresis was observed between sorption and desorption on dry and moisture-equilibrated samples and the sorption isotherms recorded for different particle sizes were essentially identical. The CH4 uptake rates were lower by a factor of two for moist coals than for dry coals. Busch, A., Gensterblum, Y., Krooss, B.M. and Siemons, N., 2006. Investigation of high-pressure selective adsorption/desorption behaviour of CO2 and CH4 on coals: An experimental study. International Journal of Coal Geology, 66(1-2): 53-68. Seidle, J.P., Jeansonne, M.W. and Erickson, D.J., 1992. Application of Matchstick Geometry to Stress-Dependent Permeability in Coals, SPE Rocky Mountain Regional Meeting, Casper, Wyoming.

Gensterblum, Y.; Sartorius, M.; Busch, A.; Krooss, B. M.; Littke, R.

2012-12-01

259

Mechanical Properties, Corrosion Resistance and Microstructural Changes during Friction Stir Processing of 5083 Aluminum Rolled Plates  

Microsoft Academic Search

Friction stir processing is a solid state process to modify microstructure and mechanical properties of sheet metals and as-cast materials. In this process, stirring action of the tool causes the material to intense plastic deformation that yields a dynamical recrystallization. In this study the effect of FSP and process parameters on microstructure, mechanical properties, wear resistance and corrosion behavior of

R. Abdi Behnagh; M. K. Besharati Givi; M. Akbari

2011-01-01

260

Process optimization and consumable development for Chemical Mechanical Planarization (CMP) processes  

NASA Astrophysics Data System (ADS)

Chemical Mechanical Planarization (CMP) is one of the most critical processing steps that enables fabrication of multilevel interconnects. The success of CMP process is limited by the implementation of an optimized process and reduction of process generated defects along with post CMP surface characteristics such as dishing and erosion. This thesis investigates to identify various sources of defects and studies the effect of factors that can be used to optimize the process. The major contributions of this work are: Understanding the effect of temperature rise on surface tribology, electrochemistry and post CMP pattern effects during the CMP process; investigating the effect of pad conditioning temperature and slurry flow rate on tribology and post CMP characteristics; development of novel slurries using polymer hybrid particles and improvement in slurry metrology to reduce surface damage during CMP. From the current research, it was shown that the effect of temperature on CMP tribology is predominantly affected by the polishing parameters and the polishing pad characteristics more than the chemical nature of the slurry. The effect of temperature is minimal on the resulting surface roughness but the with-in die non-uniformity is significantly affected by the temperature at the interface. Secondly, in this research it was shown that the effectiveness and aggressiveness of the pad conditioning process is highly influenced by the conditioning temperature. This aspect can be utilized to optimize the parameters for the pad conditioning process. Further, post CMP characteristics such as dishing, erosion and metal loss on patterned samples were shown to decrease with increase in slurry flow rate. This research then concentrates on the development of novel low defect slurry using polymer hybrid abrasive particles. Several varieties of surface functionalized polymer particles were employed to make oxide CMP slurries. These novel slurries proved to be potential candidates to reduce surface damage during CMP as they resulted in low coefficient of friction and much less surface scratches as compared to conventional abrasives. Thus, this research helps to reduce defects and non-planarity issues during CMP process thereby improving yield and reducing the cost of ownership.

Mudhivarthi, Subrahmanya R.

261

Insights into the Mechanism of Bovine CD38/NAD+Glycohydrolase from the X-Ray Structures of Its Michaelis Complex and Covalently-Trapped Intermediates  

PubMed Central

Bovine CD38/NAD+glycohydrolase (bCD38) catalyses the hydrolysis of NAD+ into nicotinamide and ADP-ribose and the formation of cyclic ADP-ribose (cADPR). We solved the crystal structures of the mono N-glycosylated forms of the ecto-domain of bCD38 or the catalytic residue mutant Glu218Gln in their apo state or bound to aFNAD or rFNAD, two 2?-fluorinated analogs of NAD+. Both compounds behave as mechanism-based inhibitors, allowing the trapping of a reaction intermediate covalently linked to Glu218. Compared to the non-covalent (Michaelis) complex, the ligands adopt a more folded conformation in the covalent complexes. Altogether these crystallographic snapshots along the reaction pathway reveal the drastic conformational rearrangements undergone by the ligand during catalysis with the repositioning of its adenine ring from a solvent-exposed position stacked against Trp168 to a more buried position stacked against Trp181. This adenine flipping between conserved tryptophans is a prerequisite for the proper positioning of the N1 of the adenine ring to perform the nucleophilic attack on the C1? of the ribofuranoside ring ultimately yielding cADPR. In all structures, however, the adenine ring adopts the most thermodynamically favorable anti conformation, explaining why cyclization, which requires a syn conformation, remains a rare alternate event in the reactions catalyzed by bCD38 (cADPR represents only 1% of the reaction products). In the Michaelis complex, the substrate is bound in a constrained conformation; the enzyme uses this ground-state destabilization, in addition to a hydrophobic environment and desolvation of the nicotinamide-ribosyl bond, to destabilize the scissile bond leading to the formation of a ribooxocarbenium ion intermediate. The Glu218 side chain stabilizes this reaction intermediate and plays another important role during catalysis by polarizing the 2?-OH of the substrate NAD+. Based on our structural analysis and data on active site mutants, we propose a detailed analysis of the catalytic mechanism.

Egea, Pascal F.; Muller-Steffner, Helene; Kuhn, Isabelle; Cakir-Kiefer, Celine; Oppenheimer, Norman J.; Stroud, Robert M.; Kellenberger, Esther; Schuber, Francis

2012-01-01

262

Fourier Transform Infrared Detection of a Polarizable Proton Trapped between Photooxidized Tyrosine YZ and a Coupled Histidine in Photosystem II: Relevance to the Proton Transfer Mechanism of Water Oxidation.  

PubMed

The redox-active tyrosine YZ (D1-Tyr161) in photosystem II (PSII) functions as an immediate electron acceptor of the Mn4Ca cluster, which is the catalytic center of photosynthetic water oxidation. YZ is also located in the hydrogen bond network that connects the Mn4Ca cluster to the lumen and hence is possibly related to the proton transfer process during water oxidation. To understand the role of YZ in the water oxidation mechanism, we have studied the hydrogen bonding interactions of YZ and its photooxidized neutral radical YZ(•) together with the interaction of the coupled His residue, D1-His190, using light-induced Fourier transform infrared (FTIR) difference spectroscopy. The YZ(•)-minus-YZ FTIR difference spectrum of Mn-depleted PSII core complexes exhibited a broad positive feature around 2800 cm(-1), which was absent in the corresponding spectrum of another redox-active tyrosine YD (D2-Tyr160). Analyses by (15)N and H/D substitutions, examination of the pH dependence, and density functional theory and quantum mechanics/molecular mechanics (QM/MM) calculations showed that this band arises from the N-H stretching vibration of the protonated cation of D1-His190 forming a charge-assisted strong hydrogen bond with YZ(•). This result provides strong evidence that the proton released from YZ upon its oxidation is trapped in D1-His190 and a positive charge remains on this His. The broad feature of the ?2800 cm(-1) band reflects a large proton polarizability in the hydrogen bond between YZ(•) and HisH(+). QM/MM calculations further showed that upon YZ oxidation the hydrogen bond network is rearranged and one water molecule moves toward D1-His190. From these data, a novel proton transfer mechanism via YZ(•)-HisH(+) is proposed, in which hopping of the polarizable proton of HisH(+) to this water triggers the transfer of the proton from substrate water to the luminal side. This proton transfer mechanism could be functional in the S2 ? S3 transition, which requires proton release before electron transfer because of an excess positive charge on the Mn4Ca cluster. PMID:24786306

Nakamura, Shin; Nagao, Ryo; Takahashi, Ryouta; Noguchi, Takumi

2014-05-20

263

Tensleep sandstone stratigraphic-hydrodynamic traps, northeast Bighorn Basin, Wyoming  

Microsoft Academic Search

The trapping mechanism for the off-structure type of accumulation in the Bighorn Basin has been a controversial subject in geologic literature. The off-structure production in a number of Bighorn Basin fields has been attributed to one or more of the following mechanisms: an updip sand pinchout or loss of porosity, a paleo trap, an unconformity trap, a tar seal, a

Pedry

1975-01-01

264

Determination of Biodegradation Process of Benzene, Toluene, Ethylbenzene and Xylenes in Seabed Sediment by Purge and Trap Gas Chromatography  

Microsoft Academic Search

Benzene, toluene, ethylbenzene, and xylenes (BTEX) are commonly found in crude oil and are used in geochemical investigations\\u000a as direct indicators of the presence of oil and gas. BTEX are easily volatile and can be degraded by microorganisms, which\\u000a affect their precise measurement seriously. A method for determining the biodegradation process of BTEX in seabed sediment\\u000a using dynamic headspace (purge

Dongqiang Han; Wanyun Ma; Dieyan Chen

2007-01-01

265

Processing, microstructure, and mechanical behavior of titanium dioxide nanotubes  

NASA Astrophysics Data System (ADS)

Titanium dioxide nanotubes are of considerable interest for use in hydrogen generation, solar cells, chemical sensors, and bioactive coatings. In this study, nanotube coatings were fabricated on a Ti substrate via anodic oxidation. A novel hierarchical coating consisting of nanotubes (˜50 nm diameter) on the nano-scale and large pores/pits (˜1-20 mum) on the micro-scale was developed. This coating has potential for use as a bioactive coating on Ti bone implants. The mechanisms for nanotube formation and microscopic pitting were discussed. Microstructure characterization was conducted using scanning electron microscopy, focused ion beam, transmission electron microscopy, and image analysis. The effect of processing variables (i.e. time, temperature, pH) on nanotube characteristics (i.e. diameter, wall thickness, length) and hierarchical structure (i.e. pit/pore size and density) was studied. Anodization time was found to affect nanotube length and microscopic pit size and density. Lowering the electrolyte pH decreased the nanotube length and microscopic pit density. Increasing electrolyte temperature decreased nanotube length and increased pit/pore density. Anodization time, pH, and temperature, showed little effect on nanotube diameter or wall thickness. Microscopic pitting in the nanotube coating was found to occur above grain boundaries in the Ti substrate and above Ti grains with (0001) orientation. It was discovered that neighboring nanotubes are connected by ridges on the tube walls and an incoherent interface is formed between crystalline Ti and amorphous titanium dioxide. The influence of Ti substrate orientation on the growth kinetics and nanotube morphology was examined. Ti grains with surface orientations near (0001) experience retarded nanotube growth compared to (xxx0) orientations. This orientation dependence is likely related to differences in atomic density. Conventional nanoindentation and interfacial force microscopy (IFM), was employed to probe the hardness, Young's modulus and deformation behavior of the nanotube coatings. From conventional nanoindentation, elastic modulus decreased for thinner coatings. Using IFM, coating modulus was measured with minimal contribution from the Ti substrate and estimated to be 4-30 GPa. During nanoindentation, nanotubes deform by tube crushing, resulting in an increase in local oxide density. Increased density causes an increase in indentation modulus from roughly 4-30 GPa in the first 50 nm of indentation.

Crawford, Grant Alan

266

CO2-ECBM related coupled physical and mechanical transport processes  

NASA Astrophysics Data System (ADS)

The interrelation of cleat transport processes and mechanical properties was investigated by permeability tests at different stress levels (60% to 130% of in-situ stress) with sorbing (CH4, CO2) and inert gases (N2, Ar, He) on a sub bituminous A coal from the Surat Basin, Queensland Australia. From the flow tests under controlled triaxial stress conditions the Klinkenberg-corrected "true" permeability coefficients and the Klinkenberg slip factors were derived. The "true"-, absolute or Klinkenberg corrected permeability shows a gas type dependence. Following the approach of Seidle et al. (1992) the cleat volume compressibility (cf) was calculated from observed changes in apparent permeability upon variation of external stress (at equal mean gas pressures). The observed effects also show a clear dependence on gas type. Due to pore or cleat compressibility the cleat aperture decreases with increasing effective stress. Vice versa we observe with increasing mean pressure at lower confining pressure an increase in permeability which we attribute to a cleat aperture widening. The cleat volume compressibility (cf) also shows a dependence on the mean pore pressure. Non-sorbing gases like helium and argon show higher apparent permeabilities than sorbing gases like methane. Permeability coefficients measured with successively increasing mean gas pressures were consistently lower than those determined at decreasing mean gas pressures. This permeability hysteresis is in accordance with results reported by Harpalani and McPherson (1985). The kinetics of matrix transport processes were studied by sorption tests on different particle sizes at various moisture contents and temperatures (cf. Busch et al., 2006). Methane uptake rates were determined from the pressure decline curves recorded for each particle-size fraction, and "diffusion coefficients" were calculated using several unipore and bidisperse diffusion models. While the CH4 sorption capacity of moisture-equilibrated coals was significantly lower (by 50%) than of dry coals, no hysteresis was observed between sorption and desorption on dry and moisture-equilibrated samples and the sorption isotherms recorded for different particle sizes were essentially identical. The CH4 uptake rates were lower by a factor of two for moist coals than for dry coals. Busch, A., Gensterblum, Y., Krooss, B.M. and Siemons, N., 2006. Investigation of high-pressure selective adsorption/desorption behaviour of CO2 and CH4 on coals: An experimental study. International Journal of Coal Geology, 66(1-2): 53-68. Harpalani, S. and McPherson, M.J., 1985. Effect of stress on permeability of coal. Quarterly Review of methane from coal seams technology, 3(2): 23-29. Seidle, J.P., Jeansonne, M.W. and Erickson, D.J., 1992. Application of Matchstick Geometry to Stress-Dependent Permeability in Coals, SPE Rocky Mountain Regional Meeting, Casper, Wyoming.

Gensterblum, Yves; Satorius, Michael; Busch, Andreas; Krooß, Bernhard

2013-04-01

267

CO2-ECBM related coupled physical and mechanical transport processes  

NASA Astrophysics Data System (ADS)

The interrelation of cleat transport processes and mechanical properties was investigated by permeability tests at different stress levels (60% to 130% of in-situ stress) with sorbing (CH4, CO2) and inert gases (N2, Ar, He) on a sub bituminous A coal from the Surat Basin, Queensland Australia. From the flow tests under controlled triaxial stress conditions the Klinkenberg-corrected "true" permeability coefficients and the Klinkenberg slip factors were derived. The "true"-, absolute or Klinkenberg corrected permeability shows a gas type dependence. Following the approach of Seidle et al. (1992) the cleat volume compressibility (cf) was calculated from observed changes in apparent permeability upon variation of external stress (at equal mean gas pressures). The observed effects also show a clear dependence on gas type. Due to pore or cleat compressibility the cleat aperture decreases with increasing effective stress. Vice versa we observe with increasing mean pressure at lower confining pressure an increase in permeability which we attribute to a cleat aperture widening. The cleat volume compressibility (cf) also shows a dependence on the mean pore pressure. Non-sorbing gases like helium and argon show higher apparent permeabilities than sorbing gases like methane. Permeability coefficients measured with successively increasing mean gas pressures were consistently lower than those determined at decreasing mean gas pressures. This permeability hysteresis is in accordance with results reported by Harpalani and McPherson (1985). The kinetics of matrix transport processes were studied by sorption tests on different particle sizes at various moisture contents and temperatures (cf. Busch et al., 2006). Methane uptake rates were determined from the pressure decline curves recorded for each particle-size fraction, and "diffusion coefficients" were calculated using several unipore and bidisperse diffusion models. While the CH4 sorption capacity of moisture-equilibrated coals was significantly lower (by 50%) than of dry coals, no hysteresis was observed between sorption and desorption on dry and moisture-equilibrated samples and the sorption isotherms recorded for different particle sizes were essentially identical. The CH4 uptake rates were lower by a factor of two for moist coals than for dry coals. Busch, A., Gensterblum, Y., Krooss, B.M. and Siemons, N., 2006. Investigation of high-pressure selective adsorption/desorption behaviour of CO2 and CH4 on coals: An experimental study. International Journal of Coal Geology, 66(1-2): 53-68. Harpalani, S. and McPherson, M.J., 1985. Effect of stress on permeability of coal. Quarterly Review of methane from coal seams technology, 3(2): 23-29. Seidle, J.P., Jeansonne, M.W. and Erickson, D.J., 1992. Application of Matchstick Geometry to Stress-Dependent Permeability in Coals, SPE Rocky Mountain Regional Meeting, Casper, Wyoming.

Gensterblum, Y.; Sartorius, M.; Busch, A.; Cumming, D.; Krooss, B. M.

2012-04-01

268

Mini ion trap mass spectrometer  

DOEpatents

An ion trap is described which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10{sup 9} and commercial mass spectrometers requiring 10{sup 4} ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products. 10 figs.

Dietrich, D.D.; Keville, R.F.

1995-09-19

269

Mini ion trap mass spectrometer  

DOEpatents

An ion trap which operates in the regime between research ion traps which can detect ions with a mass resolution of better than 1:10.sup.9 and commercial mass spectrometers requiring 10.sup.4 ions with resolutions of a few hundred. The power consumption is kept to a minimum by the use of permanent magnets and a novel electron gun design. By Fourier analyzing the ion cyclotron resonance signals induced in the trap electrodes, a complete mass spectra in a single combined structure can be detected. An attribute of the ion trap mass spectrometer is that overall system size is drastically reduced due to combining a unique electron source and mass analyzer/detector in a single device. This enables portable low power mass spectrometers for the detection of environmental pollutants or illicit substances, as well as sensors for on board diagnostics to monitor engine performance or for active feedback in any process involving exhausting waste products.

Dietrich, Daniel D. (Livermore, CA); Keville, Robert F. (Valley Springs, CA)

1995-01-01

270

Testing for Dark Matter Trapped in the Solar System  

NASA Technical Reports Server (NTRS)

We consider the possibility of dark matter trapped in the solar system in bound solar orbits. If there exist mechanisms for dissipating excess kinetic energy by an amount sufficient for generating bound solar orbits, then trapping of galactic dark matter might have taken place during formation of the solar system, or could be an ongoing process. Possible locations for acumulation of trapped dark matter are orbital resonances with the planets or regions in the outer solar system. It is posible to test for the presence of unseen matter by detecting its gravitational effects. Current results for dynamical limits obtained from analyses of planetary ephemeris data and spacecraft tracking data are presented. Possible future improvements are discussed.

Krisher, Timothy P.

1996-01-01

271

Processing effects on the mechanical properties of tungsten heavy alloys  

NASA Technical Reports Server (NTRS)

Tungsten heavy alloys exhibit significant mechanical property sensitivities to the fabrication variables. These sensitivities are illustrated in this examination of vacuum sintering and the effects of composition, sintering temperature, and sintering time on the mechanical properties of tungsten heavy alloys. Measurements were conducted to assess the density, strength, hardness, and elongation dependencies. A detrimental aspect of vacuum sintering is matrix phase evaporation, although vacuum sintering does eliminate the need for postsintering heat treatments.

Kishi, Toshihito; German, R. M.

1990-01-01

272

Mechanical and tribological properties of ion beam-processed surfaces  

Microsoft Academic Search

A variety of surface modification and surface coating techniques are currently used in industry to modify the near-surface mechanical properties that influence the friction and wear behavior of metals, metallic alloys, ceramics, and polymers. Near-surface mechanical properties such as hardness and fracture toughness of a coating-substrate system can be tailored economically without changing the bulk properties of the system. The

Padma Kodali

1997-01-01

273

High Strength Steel Weldment Reliability: Weld Metal Hydrogen Trapping.  

National Technical Information Service (NTIS)

The potential use of weld metal hydrogen getters (traps) to increase the reliability of high strength steel weldments was investigated. This research aimed to establish a fundamental understanding of the trapping mechanisms in weld metal and to evaluate t...

D. L. Olson

1998-01-01

274

The investigation of structure, chemical composition, hydrogen isotope trapping and release processes in deposition layers on surfaces exposed to DIII-D divertor plasma  

SciTech Connect

The exposure of ATG graphite sample to DIII-D divertor plasma was provided by the DiMES (Divertor Material Evaluation System) mechanism. The graphite sample arranged to receive the parallel heat flux on a small region of the surface was exposed to 600ms of outer strike point plasma. The sample was constructed to collect the eroded material directed downward into a trapping zone onto s Si disk collector. The average heat flux onto the graphite sample during the exposure was about 200W/cm{sup 2}, and the parallel heat flux was about 10 KW/cm{sup 2}. After the exposure the graphite sample and Si collector disk were analyzed using SEM, NRA, RBS, Auger spectroscopy. IR and Raman spectroscopy. The thermal desorption was studied also. The deposited coating on graphite sample is amorphous carbon layer. Just upstream of the high heat flux zone the redeposition layer has a globular structure. The deposition layer on Si disk is composed also from carbon but has a diamond-like structure. The areal density of C and D in the deposited layer on Si disk varied in poloidal and toroidal directions. The maximum D/C areal density ratio is about 0.23, maximum carbon density is about 3.8 {times} 10{sup 18}cm{sup {minus}2}, maximum D area density is about 3 {times} 10{sup 17}cm{sup 2}. The thermal desorption spectrum had a peak at 1,250K.

Buzhinskij, O.I.; Opimach, I.V.; Barsuk, V.A. [TRINITI, Troitsk (Russian Federation); Arkhipov, I.I. [Russian Academy of Science, Moscow (Russian Federation). Inst. of Physical Chemistry; West, W.P.; Wong, C.P.C. [General Atomics, San Diego, CA (United States); Whyte, D. [Univ. of California, San Diego, CA (United States); Wampler, W.R. [Sandia National Labs., Albuquerque, NM (United States)

1998-05-01

275

Quantum mechanical states as attractors for Nelson processes  

NASA Astrophysics Data System (ADS)

In this paper we reconsider, in the light of the Nelson stochastic mechanics, the idea originally proposed by Bohm and Vigier that arbitrary solutions of the evolution equation for the probability densities always relax in time toward the quantum mechanical density ¦?¦2 derived from the Schrödinger equation. The analysis of a few general propositions and of some physical examples show that the choice of the L1 metrics and of the Nelson stochastic flux is correct for a particular class of quantum states, but cannot be adopted in general. This indicates that the question if the quantum mechanical densities attract other solution of the classical Fokker-Planck equations associated to the Schrödinger equation is physically meaningful, even if a classical probabilistic model good for every quantum stale is still not available. A few suggestion in this direction are finally discussed.

Petroni, Nicola Cufaro; Guerra, Francesco

1995-02-01

276

40 CFR 408.220 - Applicability; description of the non-Alaskan mechanized bottom fish processing subcategory.  

Code of Federal Regulations, 2013 CFR

...description of the non-Alaskan mechanized bottom fish processing subcategory. 408.220 ...CATEGORY Non-Alaskan Mechanized Bottom Fish Processing Subcategory § 408.220 ...description of the non-Alaskan mechanized bottom fish processing subcategory. The...

2013-07-01

277

FINAL REPORT. AQUEOUS ELECTROCHEMICAL MECHANISMS IN ACTINIDE RESIDUE PROCESSING  

EPA Science Inventory

Plutonium and uranium residues (e.g., incinerator ash, combustibles, and sand/slag/crucibles) resulting from the purification and processing of nuclear materials constitute an enormous volume of lean processing waste and represent a significant fraction of the U. S. Department of...

278

Ion Trap Mass Spectrometry  

SciTech Connect

This chapter describes research conducted in a few research groups in the 1990s in which RF quadrupole ion trap mass spectrometers were coupled to a powerful atomic ion source, the inductively coupled plasma used in conventional ICP-MS instruments. Major section titles for this chapter are: RF Quadrupole Ion Traps Features of RF Quadrupole Ion Trap Mass Spectrometers Selective Ion Trapping methods Inductively Coupled Plasma Source Ion Trap Mass Spectrometers

Eiden, Greg C.

2005-09-01

279

Calibration of sound forces in acoustic traps  

Microsoft Academic Search

A two-dimensional or transverse acoustic trapping and its capability to noninvasively manipulate micrometersized particles with focused sound beams were experimentally demonstrated in our previous work. To apply this technique, as in optical tweezers, for studying mechanical properties of and interactions among biological particles such as cells, the trapping forces must be calibrated against known forces, i.e., viscous drag forces exerted

Jungwoo Lee; Changyang Lee; K. K. Shung

2010-01-01

280

Experimental Studies on Mechanism of Material Removal in Abrasive Flow Machining Process  

Microsoft Academic Search

In this article, the mechanism of material removal (MR) in Abrasive Flow Machining (AFM) process has been studied. Representative components of pure Aluminum and Brass were processed by AFM under similar process conditions. The processed surfaces were analyzed with the help of Scanning Electron Microscopy (SEM). SEM photographs reveal noticeable difference between abrasion patterns produced on the processed surfaces of

Sehijpal Singh; H. S. Shan; Pradeep Kumar

2008-01-01

281

Processing and mechanical characterization of lightweight polyurethane composites  

Microsoft Academic Search

A simple procedure was established to fabricate polyurethane-cenosphere particulate composite materials. Composites having four different volume fractions of cenospheres (hollow ceramic microspheres) ranging from 10 to 40% in increments of 10% were prepared and their mechanical properties were evaluated. A predictive model to estimate the fracture toughness of the composite was developed. The dynamic constitutive behavior of the composite in

V. B. Chalivendra; A. Shukla; A. Bose; V. Parameswaran

2003-01-01

282

Elementary Quantum Mechanics in a High-Energy Process  

ERIC Educational Resources Information Center

Compares two approaches to strong absorption in elementary quantum mechanics; the black sphere and a model based on the continuum theory of nuclear reactions. Examines the application to proton-antiproton interactions at low momenta and concludes that the second model is the appropriate and simplest to use. (Author/GA)

Denville, A.; And Others

1978-01-01

283

Process Demands of Rejection Mechanisms of Recognition Memory  

ERIC Educational Resources Information Center

A surge of research has been conducted to examine memory editing mechanisms that help distinguish accurate from inaccurate memories. In the present experiment, the authors examined the ability of participants to use novelty detection, recollection rejection, and plausibility judgments to reject lures presented on a recognition memory test.…

Odegard, Timothy N.; Koen, Joshua D.; Gama, Jorge M.

2008-01-01

284

Poverty Traps and Climate Change  

Microsoft Academic Search

We use a demo-economic model to examine the question of whether climate change could widen or deepen poverty traps. The model includes two crucial mechanisms. Parents are risk averse when deciding how many children to have; fertility is high when infant survival is low. High fertility spreads scarce household resources thin, resulting in children being poorly educated. At the macro

Richard S. J. Tol

2011-01-01

285

Drug trapping and delivery for Alzheimer's diagnosis.  

PubMed

In this investigation, a new design based on a PANDA ring resonator as an optical trapping tool for tangle protein, molecular motor storage, and delivery is proposed. The optical vortices are generated and the trapping mechanism is controlled in the same way as the conventional optical tweezers. The trapping force is produced by a combination of the gradient field and scattering photons. The required molecular volume is trapped and moved dynamically within the molecular network. The tangle protein and molecular motor can be transported and delivered to the required destinations for Alzheimer's diagnosis by molecular buffer and bus network. PMID:22384850

Jalil, M A; Kamoldilok, Surachart; Saktioto, T; Ong, C T; Yupapin, Preecha P

2012-10-01

286

Ion Trap in a Semiconductor Chip  

NASA Astrophysics Data System (ADS)

Current ion trap research is largely driven by the quest to build a quantum information processor, where quantum bits of information are stored in individual atomic ions and connected through a common interaction with their collective motion^1. Semiconductor processing techniques, particularly photolithography on integrated structures, allows the fabrication of ion traps which can host large numbers of qubits and shuttle ions between many separated trapping zones^2. Here we discuss the trapping of a single ion in an rf Paul trap fabricated on a monolithic GaAs heterostructure. Of particular note is that this trap is integrated on a chip and does not require any alignment or manual assembly. In addition to discussing the processing steps and electrical characteristics of the trap, we report measurements of heating of a single ion in the trap^3. Work supported by the Disruptive Technology Office under Army Research Office contract and the National Science Foundation ITR Program. 1. Cirac, J. I. & Zoller, P. Quantum computations with cold trapped ions. Phys Rev. Lett. 74, 4091-4094 (1995). 2. Kielpinski, D., Monroe, C., Wineland D. J. Architecture for a large scale ion trap quantum computer. Nature 417, 709-711 (2002). 3. D. Stick, W. K. Hensinger, S. Olmschenk, M. J. Madsen, K. Schwab, C. Monroe. Nature Phys. 2, 36-39 (2006).

Stick, Dan; Hensinger, Winfried; Olmschenk, Steven; Madsen, Martin; Schwab, Keith; Monroe, Chris

2006-05-01

287

Survey of trihalomethanes and other volatile chemical contaminants in processed foods by purge-and-trap capillary gas chromatography with mass selective detection.  

PubMed

A limited number of soft drinks, juices, beers, and waters from processed vegetables were analyzed for trihalomethanes (THMs), benzene, and toluene by a modified Environmental Protection Agency (EPA) Method 524.2. The THMs, which include chloroform, bromodichloromethane, dibromochloromethane, and bromoform, are reaction by-products of water disinfection by chlorination. EPA Method 524.2 is a purge-and-trap capillary gas chromatographic method based on mass spectrometric detection which identifies and simultaneously measures purgeable volatile organic compounds in drinking water. Chloroform was present at concentrations ranging from none detected to 94 ng/g in the 44 foods analyzed. Bromoform was not found in any of the products at a detection limit of 0.1 ng/g. Residue levels of the other THMs ranged from none detected to highs of 12 and 2 ng/g for bromodichloromethane and dibromochloromethane, respectively. Benzene residues were typically < 5 ng/g, except for 7 and 9 ng/g in 2 foods. Toluene residues were typically < or = 3 ng/g except for 23, 29, and 75 ng/g in 3 canned foods. PMID:7756854

McNeal, T P; Hollifield, H C; Diachenko, G W

1995-01-01

288

Novel designs for Penning ion traps  

Microsoft Academic Search

We present a number of alternative designs for Penning ion traps suitable for\\u000aquantum information processing (QIP) applications with atomic ions. The first\\u000atrap design is a simple array of long straight wires which allows easy optical\\u000aaccess. A prototype of this trap has been built to trap Ca+ and a simple\\u000aelectronic detection scheme has been employed to demonstrate

J. R. Castrejon-Pita; H. Ohadi; D. R. Crick; D. F. A. Winters; D. M. Segal; R. C. Thompson

2006-01-01

289

ThermoMechanical Model of Solidification Processes with Abaqus  

Microsoft Academic Search

A computational thermo-mechanical model has been developed to simulate the continuous casting of shaped sections, such as used for steel thin slabs. A general form of the transient heat equation including latent-heat from phase transformations such as solidification and other temperature-dependent properties is solved numerically for the temperature field history. The resulting thermal stresses are solved by integrating the highly

Seid Koric; Brian G. Thomas

290

Mapping optical trapping energy of nanoparticles via confocal microscopy  

NASA Astrophysics Data System (ADS)

Optical traps are highly focused laser beams that can hold and manipulate objects of microscopic scale. They are used to study the motion and energy of particles such as colloids or DNA molecules. In order to achieve this purpose we first propose to determine the energy of optical traps. We use a fluorescent nanoparticle ensemble within the optical trapping volume along with confocal microscopy to map the fluorescence intensity distribution of nanoparticles. This mapping allows us to calculate the trapping energy profile in three dimensions. We repeat this process with different trapping powers to find the depth of the trapping potential well as a function of trapping power. Trapping energy per trapping power thus measured is consistent with results obtained through previous methods such as fluorescence correlation spectroscopy conducted by our research group. With this technique of mapping trapping energy we can further study particle-particle interactions.

Lim, Min Yao

2012-02-01

291

Process entanglement as a neuronal anchorage mechanism to rough surfaces  

Microsoft Academic Search

The organization of neurons and glia cells on substrates composed of pristine carbon nanotube islands was investigated using high resolution scanning electron microscopy, immunostaining and confocal microscopy. Neurons were found bound and preferentially anchored to the rough surfaces; moreover, the morphology of the neuronal processes on the small, isolated islands of high density carbon nanotubes was found to be conspicuously

Raya Sorkin; Alon Greenbaum; Moshe David-Pur; Sarit Anava; Amir Ayali; Eshel Ben-Jacob; Yael Hanein

2009-01-01

292

Pressure infiltrated syntactic foams—Process development and mechanical properties  

Microsoft Academic Search

The pressure infiltration process for the production of aluminium syntactic foams incorporating 45 and 270?m ceramic microspheres in nominally 1350, 5083 and 6061 aluminium alloy matrices was studied. Minimisation of vacuum level, heating rate and infiltration temperature was found to allow the production of foams with very low levels of unintended porosity. Infiltration temperatures at or below the liquidus were

R. A. Palmer; K. Gao; T. M. Doan; L. Green; G. Cavallaro

2007-01-01

293

Structures, Processes and Relational Mechanisms for IT Governance  

Microsoft Academic Search

In many organisations, Information Technology (IT) has become crucial in the support, the sustainability and the growth of the business. This pervasive use of technology has created a critical dependency on IT that calls for a specific focus on IT Governance. IT Governance consists of the leadership and organisational structures and processes that ensure that the organisation's IT sustains and

Wim Van Grembergen; Steven De Haes

294

Replisome mechanics: lagging strand events that influence speed and processivity  

PubMed Central

The antiparallel structure of DNA requires lagging strand synthesis to proceed in the opposite direction of the replication fork. This imposes unique events that occur only on the lagging strand, such as primase binding to DnaB helicase, RNA synthesis, and SS B antigen (SSB) displacement during Okazaki fragment extension. Single-molecule and ensemble techniques are combined to examine the effect of lagging strand events on the Escherichia coli replisome rate and processivity. We find that primase activity lowers replisome processivity but only when lagging strand extension is inoperative. rNTPs also lower replisome processivity. However, the negative effects of primase and rNTPs on processivity are overcome by the extra grip on DNA provided by the lagging strand polymerases. Visualization of single molecules reveals that SSB accumulates at forks and may wrap extensive amounts of single-strand DNA. Interestingly SSB has an inter-strand positive effect on the rate of the leading strand based in its interaction with the replicase ?-subunit. Further, the lagging strand polymerase is faster than leading strand synthesis, indicating that replisome rate is limited by the helicase. Overall, lagging strand events that impart negative effects on the replisome are counterbalanced by the positive effects of SSB and additional sliding clamps during Okazaki fragment extension.

Georgescu, Roxana E.; Yao, Nina; Indiani, Chiara; Yurieva, Olga; O'Donnell, Mike E.

2014-01-01

295

A mechanized process algebra for verification of device synchronization protocols  

NASA Technical Reports Server (NTRS)

We describe the formalization of a process algebra based on CCS within the Higher Order Logic (HOL) theorem-proving system. The representation of four types of device interactions and a correctness proof of the communication between a microprocessor and MMU is presented.

Schubert, E. Thomas

1992-01-01

296

Knowledge Discovery Process for Characterization of Materials Failure Mechanism  

NASA Technical Reports Server (NTRS)

It is the intent of this project to provide a platform to visualize the various data collected from stress-strain testing of composite ceramic matrix materials. The data collected from the stress-strain tests are acoustic emissions (AE). As a material is subjected to a stress-strain test, various failure mechanisms occur in the material. The recorded sounds emitted during the test may correspond to various failure mechanisms. This project, thus, will give a possible way to visualize the data and data derived from the recorded AE. The stress-strain testing was performed on several composite matrix material combinations. Each of these tests produced anywhere from 1000 to 10,000+ AE events. For each AE event recorded, several characteristics in both the time and frequency domains are created. This project has two goals. First, this project will provide a summation page for a selected waveform. This page will include all of the characteristics determined from the AE event waveform along with graphs of the AE event waveform and its corresponding Power Spectrum. The other function of this project is to retrieve and display selected AE event waveforms for comparison.

Cios, Krzysztof J.

1999-01-01

297

Optimization of process parameters of mechanical type advanced machining processes using genetic algorithms  

Microsoft Academic Search

Generally, unconventional or advanced machining processes (AMPs) are used only when no other traditional machining process can meet the necessary requirements efficiently and economically because use of most of AMPs incurs relatively higher initial investment, maintenance, operating, and tooling costs. Therefore, optimum choice of the process parameters is essential for the economic, efficient, and effective utilization of these processes. Process

Neelesh K. Jain; V. K. Jain; Kalyanmoy Deb

2007-01-01

298

Fabrication of Feedthrough Atom Trapping Chips for Atomic Optics  

Microsoft Academic Search

We present a novel fabrication process for feedthrough atom trapping chips, which are used in atomic condensate optics. Copper electroplating is employed to vacuum seal the chip-through vias. The advantages of using feedthrough atom trapping chips are the simple microfabrication process and reduction of the overall chip area bonded to the glass atom trapping cell. The results demonstrate that current

H. C. Chuang; T. K. Hakala; D. Z. Anderson; V. M. Bright

2007-01-01

299

Personal Computer (PC) based image processing applied to fluid mechanics  

NASA Technical Reports Server (NTRS)

A PC based image processing system was employed to determine the instantaneous velocity field of a two-dimensional unsteady flow. The flow was visualized using a suspension of seeding particles in water, and a laser sheet for illumination. With a finite time exposure, the particle motion was captured on a photograph as a pattern of streaks. The streak pattern was digitized and processed using various imaging operations, including contrast manipulation, noise cleaning, filtering, statistical differencing, and thresholding. Information concerning the velocity was extracted from the enhanced image by measuring the length and orientation of the individual streaks. The fluid velocities deduced from the randomly distributed particle streaks were interpolated to obtain velocities at uniform grid points. For the interpolation a simple convolution technique with an adaptive Gaussian window was used. The results are compared with a numerical prediction by a Navier-Stokes computation.

Cho, Y.-C.; Mclachlan, B. G.

1987-01-01

300

Mechanical properties of a fully dense polymer derived ceramic made by a novel pressure casting process  

Microsoft Academic Search

A new process has been developed for obtaining fully dense samples of silicon carbonitride (SiCN) from polymers. The process consists of two simple steps: cross-linking the liquid organic precursor under pressure, followed by controlled pyrolysis. Net shape processing is possible by casting the liquid into a mold before polymerization. The entire process is completed below 1000 °C. Basic mechanical properties

Sandeep R Shah; Rishi Raj

2002-01-01

301

Efficient thermo-mechanical model for solidification processes  

Microsoft Academic Search

SUMMARY A new, computationally-efficient algorithm has been implemented to solve for thermal stresses, strains, and displacements in realistic solidification processes which involve highly nonlinear consitutitve relations. A general form of the transient heat equation including latent-heat from phase transformations such as solidification and other temperature-dependent properties is solved numerically for the temperature field history. The resulting thermal stresses are solved

Seid Koric; Brian G. Thomas

2006-01-01

302

Mechanism of silk processing in insects and spiders.  

PubMed

Silk spinning by insects and spiders leads to the formation of fibres that exhibit high strength and toughness. The lack of understanding of the protein processing in silk glands has prevented the recapitulation of these properties in vitro from reconstituted or genetically engineered silks. Here we report the identification of emulsion formation and micellar structures from aqueous solutions of reconstituted silkworm silk fibroin as a first step in the process to control water and protein-protein interactions. The sizes (100-200 nm diameter) of these structures could be predicted from hydrophobicity plots of silk protein primary sequence. These micelles subsequently aggregated into larger 'globules' and gel-like states as the concentration of silk fibroin increased, while maintaining solubility owing to the hydrophilic regions of the protein interspersed among the larger hydrophobic regions. Upon physical shearing or stretching structural transitions, increased birefringence and morphological alignment were demonstrated, indicating that this process mimics the behaviour of similar native silk proteins in vivo. Final morphological features of these silk materials are similar to those observed in native silkworm fibres. PMID:12944968

Jin, Hyoung-Joon; Kaplan, David L

2003-08-28

303

Optimization of pulsed TIG welding process parameters on mechanical properties of AA 5456 Aluminum alloy weldments  

Microsoft Academic Search

The present work pertains to the improvement of mechanical properties of AA 5456 Aluminum alloy welds through pulsed tungsten inert gas (TIG) welding process. Taguchi method was employed to optimize the pulsed TIG welding process parameters of AA 5456 Aluminum alloy welds for increasing the mechanical properties. Regression models were developed. Analysis of variance was employed to check the adequacy

A. Kumar; S. Sundarrajan

2009-01-01

304

PROCESSES OF CHANGE IN ALCOHOLICS ANONYMOUS: A REVIEW OF POSSIBLE MECHANISMS  

Microsoft Academic Search

Alcoholics Anonymous (AA) is the most influential approach to the treatment of alcoholism in the United States. Despite its hegemony, however, very little is known about the processes of change operative in AA. This article reviews four diverse literatures that may illuminate potential change mechanisms in AA: (1) group therapy process factors; (2) self-help group mechanisms of change; (3) the

JON D. KASSEL; ERIC F. WAGNER

1993-01-01

305

Coronal particle trapping revisited  

NASA Astrophysics Data System (ADS)

We re-examine the idea of long-term particle storage in the solar corona in the context of modern PFSS (potential-field source surface) magnetic models. As pointed out by H. Elliot in 1964 and others since then, such particles could be energetically important, at the level of some large fraction of the magnetic energy density B2/8?. We estimate the distribution and time scales of particle trapping by using representative PFSS coronal models from the Schrijver-De Rosa SolarSoft code. As the coronal field simplifies during solar minimum, it approaches axisymmetry and thus contains volumes inaccessible to charged particles under the guiding-center approximation. We conclude that time scales can be sufficiently long, so long in fact that the azimuthal drift time scale (third adiabatic invariant of guiding-center motion), for the large-scale dipolar configuration characteristic of solar minimum, can exceed one solar cycle. We discuss the possible sources of trapped particles, starting with the basic CRAND (cosmic-ray albedo neutron decay) mechanism, and relate their X-ray and ?-ray signatures to future observational capabilities including the Sentinels spacecraft.

Hudson, H. S.; MacKinnon, A.; De Rosa, M.

2006-12-01

306

Effect of pore structure on gas trapping in porous media  

NASA Astrophysics Data System (ADS)

Capillary trapping of nonwetting phase in porous media plays an important role in many geological processes. For example, large portions of hydrocarbons cannot be extracted from reservoirs due to capillary forces, while in carbon sequestration processes; capillary trapping might improve the storage efficiency. An important case is when the wetting phase (mostly water) displaces a low-viscosity low-density fluid. In such cases, like water encroachment into gas reservoirs or rising of water table in soils, competition of gravity, viscous, and capillary forces determines the final configuration of the fluids in invaded zone. The trapped nonwetting phase and its distribution within the porous media will affect many other processes such as flow of the other fluids and mass transfer phenomena. Thus, investigating the parameters affecting phase trapping and distribution, especially their relation to pore structure, which controls the capillary action, is required. The aim is to predict gas trapping from structural properties of the material. We conducted a series of column experiments, in which water displaces air at a range of flow rates in different glass-bead packs. The final 3D configuration and morphology of fluids was observed using X-Ray Computed Tomography (CT). We extracted 3D structure of porous media as well as of the trapped gas phase, and quantified them in terms of volume ratios, interfacial area, and morphology. Then we investigated the relations of the trapped phase to capillary forces (pore structure) and viscous forces (front velocity). The results give us new insights to explore the flow and dissolution processes: We found no systematic dependency of the front velocity of the invading water phase in the velocity range from 0.1 to 0.6 cm/min what corresponds to capillary numbers from 2 to 12 ×10^-6. Our experimental results indicate that the capillary trapping mechanism is controlled by the local pore structure and local connectivity and not by thermodynamics, i.e. large pores are occupied first by the gas phase.

Mohammadian, Sadjad; Geistlinger, Helmut; Vogel, Hans-Jörg

2014-05-01

307

Mechanisms of shark skin suppression by novel polymer processing aids  

NASA Astrophysics Data System (ADS)

The extrusion rate of polyethylene (PE) with narrow molar weight distribution, as e.g. metallocen catalysed polyethylene (m-PE), is limited by melt fracture. The first level of fracture is a surface defect called sharkskin. Common polymer processing aids based on fluorinated polymers shift the onset of sharkskin to higher extrusion rates by creating a "low energy surface" at the die wall and promoting wall slip. Alternatively, Kulikov et al. [1, 2] suggested thermoplastic elastomers (TPE) for sharkskin suppression, and Müller [3] showed the suitability of some TPEs as polymer processing aids. We investigated the slip velocity of several TPEs against steel, and the slip velocity in a polymeric interface between polyethylene (PE) and TPE by rotational plate-plate rheometry in the Newtonian flow regime. TPEs with lower viscosities showed higher slip velocities against steel. However, the interfacial slip velocities between PE and TPE were found to be viscosity independent. In both cases, the slip velocity was found to be proportional to the applied shear stress.

Wagner, M. H.; Himmel, T.; Kulikov, O.; Hornung, K.

2014-05-01

308

Processing and mechanical behavior of hypereutectoid steel wires  

SciTech Connect

Hypereutectoid steels have the potential for dramatically increasing the strength of wire used in tire cord and in other high strength wire applications. The basis for this possible breakthrough is the elimination of a brittle proeutectoid network that can form along grain boundaries if appropriate processing procedures and alloy additions are used. A review is made of work done by Japanese and other researchers on eutectoid and mildly hypereutectoid wires. A linear extrapolation of the tensile strength of fine wires predicts higher strengths at higher carbon contents. The influence of processing, alloy additions and carbon content in optimizing the strength, ductility and fracture behavior of hypereutectoid steels is presented. It is proposed that the tensile strength of pearlitic wires is dictated by the fracture strength of the carbide lamella at grain boundary locations in the carbide. Methods to improve the strength of carbide grain boundaries and to decrease the carbide plate thickness will contribute to enhancing the ultrahigh strength obtainable in hypereutectoid steel wires. 23 refs., 13 figs., 1 tab.

Lesuer, D.R.; Syn, C.K.; Sherby, O.D.; Kim, D.K.

1996-06-25

309

Elimination of deep surface traps in charged colloidal PbS and CdSe quantum dots  

NASA Astrophysics Data System (ADS)

Colloidal quantum dots (CQDs) offer a promising path towards high efficiency, scalable, solution and room processed photovoltaics and electronics. Their promise is curtailed today by difficulty of doping, inefficient transport, nonradiative recombination, and blinking, all generally attributed to electronic trap formation. Using first-principles simulations on off-stoichiometric colloidal quantum dots, we show that preparing a CQD free of traps is possible. However, self-compensating defects can form deep electronic trap states in response to charging or doping even in the most idealized CQDs. Surface traps arise from atomic dimers whose energy levels reside within the bandgap. The same states can also form upon photoexcitation, providing an atomistic mechanism for blinking. We show that avoiding the trap formation upon doping is possible by incorporation of select cations on the surface which shift the dimer energy levels above the quantum-confined bandedge.

Voznyy, Oleksandr; Thon, Susanna; Ip, Alex; Sargent, Edward

2013-03-01

310

Theoretical Study of the Inverting Mechanism in a Processive Cellobiohydrolase with Quantum Mechanical Calculations  

SciTech Connect

The Hypocrea jecorina Family 6 cellobiohydrolase (Cel6A) is one of most efficient enzymes for cellulose deconstruction to soluble sugars and is thus of significant current interest for the growing biofuels industry. Cel6A is known to hydrolyze b(1,4)-glycosidic linkages in cellulose via an inverting mechanism, but there are still questions that remain regarding the role of water and the catalytic base. Here we study the inverting, single displacement, hydrolytic reaction mechanism in Cel6A using density functional theory (DFT) calculations. The computational model used to follow the reaction is a truncated active site model with several explicit waters based on structural studies of H. jecorina Cel6A. Proposed mechanisms are evaluated with several density functionals. From our calculations, the role of the water in nucleophilic attack on the anomeric carbon, and the roles of several residues in the active site loops are elucidated explicitly for the first time. We also apply quantum mechanical calculations to understand the proton transfer reaction which completes the catalytic cycle.

Kim, S.; Payne, C. M.; Himmel, M. E.; Crowley, M. F.; Paton, R. S.; Beckham, G. T.

2012-01-01

311

A Better Fly Trap  

NSDL National Science Digital Library

In this activity, learners observe fly behavior and then build a flytrap. They make more observations, compare the effectiveness of different traps, and modify their traps to increase their effectiveness. In doing so, learners consider what variables make for an effective trap as well as learning how to study the behavior of an animal. Even pesky flies provide an interesting challenge.

Science, Lawrence H.

1979-01-01

312

Thermostatic steam traps  

Microsoft Academic Search

A thermostatic steam trap is described comprising: a passageway for fluid flow; two connections constituting opposite ends of the passageway; a valve that opens and closes the trap having a valve seat disposed in the passageway; and a temperature-responsive element carrying a movable part of the valve that co-operates with the valve seat to open and close the trap; either

Dewhirst

1987-01-01

313

Grain boundary engineering in alloy D9 through thermo-mechanical processing: influence of process variables and aspects of micro-mechanisms  

Microsoft Academic Search

By employing low-strain one-step thermo-mechanical processing (OTMP) and iterative thermo-mechanical processing (ITMP) we\\u000a developed grain boundary engineered microstructure in a Ti-modified austenitic stainless steel (alloy D9). In OTMP, small\\u000a amount of strain (0, 5, 10 and 15%) was imparted on solution annealed sample and subsequently annealed at various temperatures\\u000a (1173–1273 K) for different time periods (0.5, 1 and 2 h). A pre-strain

Sumantra Mandal; A. K. Bhaduri; V. Subramanya Sarma

314

3-D Modelling of Electromagnetic, Thermal, Mechanical and Metallurgical Couplings in Metal Forming Processes  

SciTech Connect

The different stages of metal forming processes often involve - beyond the mechanical deformations processes - other physical coupled problems, such as heat transfer, electromagnetism or metallurgy. The purpose of this paper is to focus on problems involving electromagnetic couplings. After a brief recall on electromagnetic modeling, we shall then focus on induction heating processes and present some results regarding heat transfer, as well as mechanical couplings. A case showing coupling for metallurgic microstructure evolution will conclude this paper.

Chenot, Jean-Loup; Bay, Francois [Center for Material Forming (CEMEF), Ecole des Mines de Paris - UMR CNRS 7635, BP 207, F-06904 Sophia-Antipolis Cedex (France)

2007-04-07

315

Optimized Bose-Einstein-condensate production in a dipole trap based on a 1070-nm multifrequency laser: Influence of enhanced two-body loss on the evaporation process  

SciTech Connect

We present an optimized strategy for the production of tightly confined Bose-Einstein condensates (BEC) of {sup 87}Rb in a crossed dipole trap with direct loading from a magneto-optical trap. The dipole trap is created with light of a multifrequency fiber laser with a center wavelength of 1070 nm. Evaporative cooling is performed by ramping down the laser power only. A comparison of the resulting atom number in an almost pure BEC to the initial atom number and the value for the gain in phase space density per atom lost confirm that this straightforward strategy is very efficient. We observe that the temporal characteristics of evaporation sequence are strongly influenced by power-dependent two-body losses resulting from enhanced optical pumping to the higher-energy hyperfine state. We characterize these losses and compare them to results obtained with a single-frequency laser at 1030 nm.

Lauber, T.; Kueber, J.; Wille, O.; Birkl, G. [Technische Universitaet Darmstadt, Institut fuer Angewandte Physik, Schlossgartenstrasse 7, D-64289 Darmstadt (Germany)

2011-10-15

316

Cyclooxygenase Reaction Mechanism of PGHS ------- Evidence for a Reversible Transition between a Pentadienyl Radical and a New Tyrosyl Radical by Nitric Oxide Trapping  

PubMed Central

Incubation of prostaglandin H synthase-1 (PGHS-1) under anaerobic conditions with peroxide and arachidonic acid leads to two major radical species: a pentadienyl radical and a radical with a narrow EPR spectrum. The proportions of the two radicals are sensitive to temperature, favoring the narrow radical species at 22 °C. The EPR characteristics of this latter radical are somewhat similar to the previously reported narrow-singlet tyrosine radical NS1a and are insensitive to deuterium labeling of AA. To probe the origin and structure of this radical, we combined EPR analysis with nitric oxide (NO) trapping of tyrosine and substrate derived radicals for both PGHS-1 and -2. Formation of 3-nitrotyrosine in the proteins was analyzed by immunoblotting, whereas NO adducts to AA and AA metabolites were analyzed by mass spectrometry and by chromatography of 14C-labeled products. The results indicate that both nitrated tyrosine residues and NO-AA adducts formed upon NO trapping. The NO-AA adduct was predominantly an oxime at C11 of AA with three conjugated double bonds, as indicated by absorption at 275 nm and by mass spectral analysis. This adduct amounted to 10% and 20% of the heme concentration of PGHS-1 and -2, respectively. For PGHS-1, the yield of NO-AA adduct matched the yield of the narrow radical signal obtained in parallel EPR experiments. High frequency EPR characterization of this narrow radical, reported in an accompanying paper, supports assignment to a new tyrosyl radical, NS1c, rather than an AA-based radical. To reconcile the results from EPR and NO-trapping studies, we propose that the NS1c is in equilibrium with an AA pentadienyl radical, and that the latter reacts preferentially with NO.

Lu, Jian-Ming; Rogge, Corina E.; Wu, Gang; Kulmacz, Richard J.; van der Donk, Wilfred A.; Tsai, Ah-lim

2011-01-01

317

Streamer-induced transport in the presence of trapped ion modes in tokamak plasmas  

SciTech Connect

Global gyrokinetic Vlasov simulations for trapped ion modes are performed by solving a Vlasov equation averaged over the cyclotron and bounce motions of trapped ions. The distribution function, for trapped ions, is then calculated in a two-dimensional phase space, parametrized by the longitudinal action (energy) and the magnetic moment in presence of magnetic shear. The physical mechanism of the saturation processes between streamerlike structures and zonal flows in relation to the suppression of turbulent transport is discussed. The magnetic shear is identified to play a key role in the dominant streamer-induced transport regime, which exhibits a Bohm-like scaling. The interaction of streamerlike structures with plasma turbulence is shown to produce the inverse cascade that condenses onto long-wavelength trapped ion structures, on the basis on wave triad interactions.

Ghizzo, A.; Del Sarto, D. [IJL UMR 7163, Nancy-Universites EPCS, BP 239, F-54506 Vandoeuvre les Nancy (France); Garbet, X.; Sarazin, Y. [IRFM, CEA Cadarache, 13108 St. Paul-Les-Durance (France)

2010-09-15

318

Age and sex selectivity in trapping mule deer  

SciTech Connect

A mule deer (Odocoileus hemionus) trapping experiment is described using modified Clover traps in which changes in the placement of bait and height of the trap door modified the ratio of adult does to male and female fawns captured. The mechanisms responsible for the changes in age-sex capture ratios are discussed and indicate that modified Clover traps selectivity capture mule deer, thus introducing bias into population sampling. (JMT)

Garrott, R.A.; White, G.C.

1982-01-01

319

Trapping cavitation bubbles with a self-focused laser beam  

Microsoft Academic Search

We observed that laser-induced cavitation bubbles in water can be trapped in a self-focused laser beam. Both optical imaging and acoustic detection have been utilized to confirm bubble trapping. Transverse and longitudinal trapping forces were measured to be as large as 87 and 11 pN, respectively. This result is contrary to conventional wisdom, since the mechanism of trapping in conventional

Jing Yong Ye; Guoqing Chang; Theodore B. Norris; Christine Tse; Marwa J. Zohdy; Kyle W. Hollman; Matthew O'Donnell; James R. Baker Jr.

2004-01-01

320

Excitation of transverse dipole and quadrupole modes in a pure ion plasma in a linear Paul trap to study collective processes in intense beams  

SciTech Connect

Transverse dipole and quadrupole modes have been excited in a one-component cesium ion plasma trapped in the Paul Trap Simulator Experiment (PTSX) in order to characterize their properties and understand the effect of their excitation on equivalent long-distance beam propagation. The PTSX device is a compact laboratory Paul trap that simulates the transverse dynamics of a long, intense charge bunch propagating through an alternating-gradient transport system by putting the physicist in the beam's frame of reference. A pair of arbitrary function generators was used to apply trapping voltage waveform perturbations with a range of frequencies and, by changing which electrodes were driven with the perturbation, with either a dipole or quadrupole spatial structure. The results presented in this paper explore the dependence of the perturbation voltage's effect on the perturbation duration and amplitude. Perturbations were also applied that simulate the effect of random lattice errors that exist in an accelerator with quadrupole magnets that are misaligned or have variance in their field strength. The experimental results quantify the growth in the equivalent transverse beam emittance that occurs due to the applied noise and demonstrate that the random lattice errors interact with the trapped plasma through the plasma's internal collective modes. Coherent periodic perturbations were applied to simulate the effects of magnet errors in circular machines such as storage rings. The trapped one component plasma is strongly affected when the perturbation frequency is commensurate with a plasma mode frequency. The experimental results, which help to understand the physics of quiescent intense beam propagation over large distances, are compared with analytic models.

Gilson, Erik P.; Davidson, Ronald C.; Efthimion, Philip C.; Majeski, Richard; Startsev, Edward A.; Wang, Hua [Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] [Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Koppell, Stewart [University of Texas at Austin, Austin, Texas 78712 (United States)] [University of Texas at Austin, Austin, Texas 78712 (United States); Talley, Matthew [Brigham Young University, Provo, Utah 84602 (United States)] [Brigham Young University, Provo, Utah 84602 (United States)

2013-05-15

321

Quantification of capillary trapping of gas clusters using X-ray microtomography  

NASA Astrophysics Data System (ADS)

major difficulty in modeling multiphase flow in porous media is the emergence of trapped phases. Our experiments demonstrate that gas can be trapped in either single-pores, multipores, or in large connected networks. These large connected clusters can comprise up to eight grain volumes and can contain up to 50% of the whole trapped gas volume. About 85% of the gas volume is trapped by multipore gas clusters. This variety of possible trapped gas clusters of different shape and volume will lead to a better process understanding of bubble-mediated mass transfer. Since multipore gas bubbles are in contact with the solid surface through ultrathin adsorbed water films the interfacial area between trapped gas clusters and intergranular capillary water is only about 80% of the total gas surface. We could derive a significant (R2 = 0.98) linear relationship between the gas-water-interface and gas saturation. We found no systematic dependency of the front velocity of the invading water phase in the velocity range from 0.1 to 0.6 cm/min corresponding to capillary numbers from 2 × 10-7 to 10-6. Our experimental results indicate that the capillary trapping mechanism is controlled by the local pore structure and local connectivity and not by thermodynamics, i.e., by the minimum of the Free Energy, at least in the considered velocity range. Consistent with this physical picture is our finding that the trapping frequency (= bubble-size distribution) reflects the pore size distribution for the whole range of pore radii, i.e., the capillary trapping process is determined by statistics and not by thermodynamics.

Geistlinger, Helmut; Mohammadian, Sadjad; Schlueter, Steffen; Vogel, Hans-Joerg

2014-05-01

322

A Laplace pressure based microfluidic trap for passive droplet trapping and controlled release  

PubMed Central

Here, we present a microfluidic droplet trap that takes advantage of the net Laplace pressure force generated when a droplet is differentially constricted. Mathematical simulations were first used to understand the working range of the component; followed by finite element modeling using the CFD software package to further characterize the behavior of the system. Controlled release of the trapped droplets is also demonstrated through both a mechanical method and a chemical method that manipulates the total pressure exerted on the trapped droplet. The unique design of this trapping device also provides the capability for selection of a single droplet from a train, as well as droplet fusion.

Simon, Melinda G.; Lin, Robert; Fisher, Jeffrey S.; Lee, Abraham P.

2012-01-01

323

Volatile Release from the Siberian Traps Inferred from Melt Inclusions  

NASA Astrophysics Data System (ADS)

The Siberian Traps Large Igneous Province is one of the largest known continental flood volcanic provinces in the Phanerozoic. The quantification of volatile degassing is particularly important because the Siberian Traps have often been invoked as a possible trigger for the end-Permian mass extinction (e.g. Campbell et al., 1992; Wignall, 2001). Volatile degassing provides a crucial mechanism to link mafic volcanic eruption to global environmental change. Mafic flood basalt magmas are expected to have low volatile contents (similar to mid-ocean ridge basalts). However, Siberian Traps magmas were chambered in and erupted through a thick sedimentary basin and may have interacted with, and obtained volatiles from, sedimentary lithologies such as limestone, coal, and evaporite. Melt inclusions from the Siberian Traps provide insight into the potential total volatile budget throughout the evolution of the large igneous province. These droplets of trapped melt may preserve volatile species that would otherwise have degassed at the time of eruption (Thordarson et al., 1996). Mafic pyroclastic deposits from the lowermost Arydzhangsky suite (basal Siberian Traps) contain clinopyroxene phenocrysts hosting melt inclusions. Electron microprobe analysis of clinopyroxene-hosted re-homogenized melt inclusions indicates maximum measured concentrations of up to 1500 - 2000 ppm sulfur, 500 - 760 ppm chlorine, and 1900 - 2400 ppm fluorine. Olivines from the Maymechinsky suite, recognized as the last extrusive products of Siberian Traps volcanism, contain melt inclusions with maximum sulfur concentrations in the range of 5000 ppm, and less substantial concentrations of chlorine and fluorine. Intrusive igneous rocks from the province also display significant volatile contents. A sill from the Ust-Ilimsk region yielded plagioclase-hosted melt inclusions which contain chlorine and fluorine concentrations nearing one weight percent. Visscher et al. (2004) proposed that chlorofluorocarbon compounds (CFCs) may have played a major role in the terrestrial end-Permian extinction. These CFCs are powerful catalysts for the breakdown of ozone, a process which can expose the biosphere to increased ultraviolet radiation. Measurements of elevated chlorine and fluorine from the Siberian Traps may thus provide a concrete source for CFCs that could have triggered this kill mechanism.

Black, B. A.; Elkins-Tanton, L. T.; Rowe, M. C.; Ukstins Peate, I.

2009-12-01

324

Mechanical-biological waste treatment with thermal processing of partial fractions.  

National Technical Information Service (NTIS)

Technologies for mechanical-biological treatment of waste in the Land of Hessen were compared including thermal processes like combustion and gasification. The new and more rigid limiting values specified in the Technical Guide for Municipal Waste Treatme...

1998-01-01

325

Studies on the Reaction Mechanism and Product Distribution of the Fischer-Tropsch Synthesis Process.  

National Technical Information Service (NTIS)

Experimental and theoretical studies on the reaction mechanism, products, and catalyst of the Fischer-Tropsch synthesis process are described. The author's many own product spectra obtained with iron base catalysts (with strongly varying pressures, temper...

M. Ritschel

1983-01-01

326

A Mechanism That Bounds Execution Performance for Process Group for Mitigating CPU Abuse  

NASA Astrophysics Data System (ADS)

Secure OS has been the focus of several studies. However, CPU resources, which are important resources for executing a program, are not the object of access control. For preventing the abuse of CPU resources, we had earlier proposed a new type of execution resource that controls the maximum CPU usage [5,6] The previously proposed mechanism can control only one process at a time. Because most services involve multiple processes, the mechanism should control all the processes in each service. In this paper, we propose an improved mechanism that helps to achieve a bound on the execution performance of a process group, in order to limit unnecessary processor usage. We report the results of an evaluation of our proposed mechanism.

Yamauchi, Toshihiro; Hara, Takayuki; Taniguchi, Hideo

327

Phenomena and mechanisms of mixed crystal formation in solutions II. Mechanism of interface processes  

NASA Astrophysics Data System (ADS)

The characteristic features of formation of mixed crystals in solutions and the basic concept underlying these processes were established in [J. Crystal Growth. 255 (2003) 150; J. Crystal Growth. 172 (1996) 226; Zap. Vses. Mineral. O. (1983) 742; Zap. Vseross. Mineral. O. (1991) 3; Zh. Struct. Khim. (1994) 79]. The present study is a continuation of the complex research of morphology and defects of potassium acid phthalate-rubidium acid phthalate (KAP-RbAP) mixed crystals that are formed in aqueous solutions. The most important characteristic of this series is the formation of heteroepitaxial porous and continuous textures as a result of the exchange reaction between the crystal and the "foreign" solution. The interaction of KAP and RbAP crystals with aqueous solutions saturated with RbAP and KAP, respectively, is studied. The corresponding processes were observed both in situ and ex situ with optical and atomic force microscopes. The results obtained were used to develop the theoretical model of formation of specific morphological textures in liquid-phase heteroepitaxy, including the textures formed in aqueous solutions of various salts.

Voloshin, A. E.; Kovalev, S. I.; Rudneva, E. B.; Glikin, A. E.

2004-01-01

328

Progress towards an experimental study of microscopic dipole trap loading and an investigation of atom dynamics in configurable microscopic double-wells  

Microsoft Academic Search

We present our progress towards an experiment to investigate microscopic optical dipole traps, trap loading and atom dynamics in microscopic optical traps. Loading mechanics of large dipole traps from a laser cooled atomic molasses or a magneto-optically trapped atoms have been extensively investigated, and the loading dynamics are relatively well understood. While microscopic traps are finding increasing number of uses,

Tyler Blum; Pasad Kulatunga

2010-01-01

329

Total simulation model of the thermo-mechanical process in shape rolling of steel rods  

Microsoft Academic Search

The production of steel reinforcing bars for civil engineering is investigated by means of FEM-simulation. An integrated system for computing appropriate thermo-mechanical parameters of the rolling process is proposed. Generalized plane strain approach and coupled thermal-mechanical solution are applied. The microstructural model combines both the effect of the recrystallization mechanisms (static, dynamic and metadynamic) upon the austenite grain forming in

N. Bontcheva; G. Petzov

2005-01-01

330

A physico-mechanical approach to modeling of metal forming processes—part I: theoretical framework  

Microsoft Academic Search

A combined physico-mechanical approach to research and modeling of forming processes for metals with predictable properties\\u000a is developed. The constitutive equations describing large plastic deformations under complex loading are based on both plastic\\u000a flow theory and continuum damage mechanics. The model which is developed in order to study strongly plastically deformed materials\\u000a represents their mechanical behavior by taking micro-structural damage

Maxim A. Zapara; Nikolay D. Tutyshkin; Wolfgang H. Müller; Kerstin Weinberg; Ralf Wille

2008-01-01

331

Thermal–hydrologic–mechanical–chemical processes in the evolution of engineered geothermal reservoirs  

Microsoft Academic Search

In a companion paper [Taron J, Elsworth D, Min K-B. Numerical simulation of thermal–hydrologic–mechanical–chemical processes in deformable, fractured porous media. Int J Rock Mech Min Sci 2009; doi:10.1016\\/j.ijrmms.2009.01.008] we introduced a new methodology and numerical simulator for the modeling of thermal–hydrologic–mechanical–chemical processes in dual-porosity media. In this paper we utilize the model to examine some of the dominant behaviors and

Joshua Taron; Derek Elsworth

2009-01-01

332

Nonlinear stabilizing control law, with a dynamical high gain observer: application to mechanical process  

Microsoft Academic Search

The authors consider mechanical systems for which a stabilizing control law from the minimization of a Lyapunov function has to be constructed. A stabilizing control law for an overhead crane is proposed. In particular, a high-gain observer is used to estimate the momentum of the mechanical process. Its gain is adaptive and depends on the estimation error

T. Chorot; J. De Leon Morales

1991-01-01

333

Steam traps: simple but important  

SciTech Connect

An overeview of various steam trap designs and their characteristics is presented. The basic uses of each design are discussed. The need for steam traps is reviewed and it is stressed that steam traps (which do not require operator attendance) is the simplest and most cost effective means of allowing condensate to drain away from critical areas. The four basic types of steam traps are described. These are: (1) inverted bucket traps; (2) float traps; (3) thermodynamic traps; and (4) condensate load traps. Advantages and disadvantages of each type of steam trap are discussed as well as cost considerations. Considerations in usage of each type of trap are pointed out. (MJJ)

Hammond, H.

1981-03-01

334

Trapping effects in irradiated and avalanche-injected MOS capacitors  

NASA Technical Reports Server (NTRS)

The trapping parameters for holes, and for electrons in the presence of trapped holes, have been measured from a set of wafers with different oxide thickness processed under controlled conditions. The trap cross-sections and densities indicate at least three trap species, including an interfacial species, a dominant bulk species which is determined to tail off from the silicon interface, and a third, lower density bulk species that is distributed throughout the oxide.

Bakowski, M.; Cockrum, R. H.; Zamani, N.; Maserjian, J.; Viswanathan, C. R.

1978-01-01

335

Chemical--Mechanical Lift-Off Process for InGaN Epitaxial Layers  

NASA Astrophysics Data System (ADS)

An InGaN-based light-emitting diode (LED) structure was separated from a GaN/sapphire structure by inserting sacrificial Si-doped InGaN/GaN superlattice layers through a chemical--mechanical lift-off (CMLO) process. The CMLO process consisted of a band-gap-selective photoelectrochemical lateral wet etching process and a mechanical lift-off process. A lower elastic modulus and hardness of the lateral-etched LED structure were measured compared with the conventional LED structure, which indicated a weak mechanical property of the treated LED structure. The photoluminescence blue-shift phenomenon and the Raman redshift phenomenon indicated that the compressive strain from the bottom GaN/sapphire structure was released through the CMLO process.

Lin, Ming-Shiou; Lin, Chia-Feng; Huang, Wan-Chun; Wang, Guei-Miao; Shieh, Bing-Cheng; Dai, Jing-Jie; Chang, Shou-Yi; Wuu, D. S.; Liu, Po-Liang; Horng, Ray-Hua

2011-06-01

336

[Processing mechanism of Epimedium fried with suet oil based on absorption and metabolism of flavonoids].  

PubMed

As beneficial traditional Chinese medicine, Epimedium fried with suet oil can enhance the effect of warming kidney yang. Previous literature studies about processing of Epimedium mainly focused on changes in chemical composition and pharmacological effect. From the angle of flavonoids absorption and metabolism, our group innovatively study the processing mechanism of Epimedium based on active component transformation combined with intestinal absorption barrier. The processing effect of fried Epimedium can be divided into two key aspects of " heat" during processing and processing accessories "suet oil". Through continuous three National Natural Science Foundation items, the research group has clarified the scientific connotation of "heat" during processing with ADME, and explains the synergistic mechanism of processing accessories "suet oil" based on self-assembled micelles formation in vivo for the first time. This paper summarizes the research ideas and results of Epimedium processing mechanism of the project team for many years, and discusses the future research direction and content, in order to provide new ideas and new methods for modern Chinese medicine processing mechanism. PMID:24946535

Sun, E; Wei, Ying-Jie; Zhang, Zhen-Hai; Cui, Li; Xu, Feng-Juan; Jia, Xiao-Bin

2014-02-01

337

Microparticle trapping in an ultrasonic Bessel beam  

PubMed Central

This paper describes an acoustic trap consisting of a multi-foci Fresnel lens on 127??m thick lead zirconate titanate sheet. The multi-foci Fresnel lens was designed to have similar working mechanism to an Axicon lens and generates an acoustic Bessel beam, and has negative axial radiation force capable of trapping one or more microparticle(s). The fabricated acoustic tweezers trapped lipid particles ranging in diameter from 50 to 200??m and microspheres ranging in diameter from 70 to 90??m at a distance of 2 to 5?mm from the tweezers without any contact between the transducer and microparticles.

Choe, Youngki; Kim, Jonathan W.; Shung, K. Kirk; Kim, Eun Sok

2011-01-01

338

Microparticle trapping in an ultrasonic Bessel beam.  

PubMed

This paper describes an acoustic trap consisting of a multi-foci Fresnel lens on 127??m thick lead zirconate titanate sheet. The multi-foci Fresnel lens was designed to have similar working mechanism to an Axicon lens and generates an acoustic Bessel beam, and has negative axial radiation force capable of trapping one or more microparticle(s). The fabricated acoustic tweezers trapped lipid particles ranging in diameter from 50 to 200??m and microspheres ranging in diameter from 70 to 90??m at a distance of 2 to 5?mm from the tweezers without any contact between the transducer and microparticles. PMID:22247566

Choe, Youngki; Kim, Jonathan W; Shung, K Kirk; Kim, Eun Sok

2011-12-01

339

Evaluating steam trap performance  

SciTech Connect

This paper presents a method for evaluating the performance level of steam traps by preparing an economic analysis of several types to determine the equivalent uniform annual cost. A series of tests on steam traps supplied by six manufacturers provided data for determining the relative efficiencies of each unit. The comparison was made using a program developed for the Texas Instruments T1-59 programmable calculator to evaluate overall steam trap economics.

Fuller, N.Y.

1985-08-08

340

Micro-fabricated stylus ion trap  

NASA Astrophysics Data System (ADS)

An electroformed, three-dimensional stylus Paul trap was designed to confine a single atomic ion for use as a sensor to probe the electric-field noise of proximate surfaces. The trap was microfabricated with the UV-LIGA technique to reduce the distance of the ion from the surface of interest. We detail the fabrication process used to produce a 150 ?m tall stylus trap with feature sizes of 40 ?m. We confined single, laser-cooled, 25Mg+ ions with lifetimes greater than 2 h above the stylus trap in an ultra-high-vacuum environment. After cooling a motional mode of the ion at 4 MHz close to its ground state ( = 0.34 +/- 0.07), the heating rate of the trap was measured with Raman sideband spectroscopy to be 387 +/- 15 quanta/s at an ion height of 62 ?m above the stylus electrodes.

Arrington, Christian L.; McKay, Kyle S.; Baca, Ehren D.; Coleman, Jonathan J.; Colombe, Yves; Finnegan, Patrick; Hite, Dustin A.; Hollowell, Andrew E.; Jördens, Robert; Jost, John D.; Leibfried, Dietrich; Rowen, Adam M.; Warring, Ulrich; Weides, Martin; Wilson, Andrew C.; Wineland, David J.; Pappas, David P.

2013-08-01

341

Mechanism of hologram formation in fixation-free rehalogenating bleaching processes  

NASA Astrophysics Data System (ADS)

The mechanism of hologram formation in fixation-free rehalogenating bleaching processes have been treated by different authors. The experiments carried out on Agfa 8E75 HD plates led to the conclusion that material transfer from the exposed to the unexposed zones is the main mechanism under the process. We present a simple model that explains the mechanism of hologram formation inside the emulsion. Also quantitative data obtained using both Agfa 8E75 HD and Slavich PFG-01 fine-grained red-sensitive emulsions are given and good agreement between theory and experiments are found.

Neipp, Cristian; Pascual, Inmaculada; Belendez, Augusto

2002-07-01

342

Applications of microelectromagnetic traps.  

PubMed

Microelectromagnetic traps (METs) have been used for almost two decades to manipulate magnetic fields. Different trap geometries have been shown to produce distinct magnetic fields and field gradients. Initially, microelectromagnetic traps were used mainly to separate and concentrate magnetic material at small scales. Recently such traps have been implemented for unique applications, for example filterless bioseparations, inductive heat generation, and biological detection. In this review, we describe recent reports in which MET geometry, current density, or external fields have been used. Descriptions of recent applications in which METs have been used to develop sensors, manipulate DNA, or block ion current are also provided. PMID:22562543

Basore, Joseph R; Baker, Lane A

2012-06-01

343

Sisyphus cooling of electrically trapped polyatomic molecules.  

PubMed

Polar molecules have a rich internal structure and long-range dipole-dipole interactions, making them useful for quantum-controlled applications and fundamental investigations. Their potential fully unfolds at ultracold temperatures, where various effects are predicted in many-body physics, quantum information science, ultracold chemistry and physics beyond the standard model. Whereas a wide range of methods to produce cold molecular ensembles have been developed, the cooling of polyatomic molecules (that is, with three or more atoms) to ultracold temperatures has seemed intractable. Here we report the experimental realization of optoelectrical cooling, a recently proposed cooling and accumulation method for polar molecules. Its key attribute is the removal of a large fraction of a molecule's kinetic energy in each cycle of the cooling sequence via a Sisyphus effect, allowing cooling with only a few repetitions of the dissipative decay process. We demonstrate the potential of optoelectrical cooling by reducing the temperature of about one million CH(3)F molecules by a factor of 13.5, with the phase-space density increased by a factor of 29 (or a factor of 70 discounting trap losses). In contrast to other cooling mechanisms, our scheme proceeds in a trap, cools in all three dimensions and should work for a large variety of polar molecules. With no fundamental temperature limit anticipated down to the photon-recoil temperature in the nanokelvin range, we expect our method to be able to produce ultracold polyatomic molecules. The low temperatures, large molecule numbers and long trapping times of up to 27 seconds should allow an interaction-dominated regime to be attained, enabling collision studies and investigation of evaporative cooling towards a Bose-Einstein condensate of polyatomic molecules. PMID:23151480

Zeppenfeld, Martin; Englert, Barbara G U; Glöckner, Rosa; Prehn, Alexander; Mielenz, Manuel; Sommer, Christian; van Buuren, Laurens D; Motsch, Michael; Rempe, Gerhard

2012-11-22

344

Deadly Glue — Adhesive Traps of Carnivorous Plants  

Microsoft Academic Search

\\u000a Carnivorous plants trap and utilize animals in order to improve their supply with mineral nutrients. One strategy for prey\\u000a capture is the use of adhesive traps, i.e., leaves that produce sticky substances. Sticky shoots are widespread in the plant\\u000a kingdom and serve to protect the plant, especially flowers and seeds. In some taxa, mechanisms have been developed to absorb\\u000a nutrients

Wolfram Adlassnig; Thomas Lendl; Marianne Peroutka; Ingeborg Lang

345

Comparison between the mechanical and radiative electron-capture processes at high energies  

NASA Astrophysics Data System (ADS)

The ground-state-ground-state mechanical and radiative electron-capture processes are studied at very high, but not relativistic, projectile velocities. Three-body calculations were carried out with use of the continuum distorted-wave theoretical method for both processes. Total cross sections and final-atom angular distributions were computed, and the importance of each mechanism examined. For total cross sections, the numerical results reaffirm that the radiative process is the predominant mechanism at very high projectile energies. For a given incident charge, the range of projectile energies in which the nonrelativistic radiative mechanism is the most important decreases as the target charge increases. It is found that the radiative mechanism produces a very sharp final-atom angular distribution in the forward direction. When both processes, the radiative and mechanical, give the same total cross section, the calculations show that the radiative differential cross section in the forward direction is almost 2 orders of magnitude larger than the mechanical one.

Gonzalez, A. D.; Miraglia, J. E.

1984-11-01

346

Mechanism of material removal in the magnetic abrasive process and the accuracy of machining  

Microsoft Academic Search

In this paper, we focus on the magnetic abrasive process as a sizing process and present a theory which explains the out-of-roundness error phenomenon based on force analysis of the material removal mechanism. The theory is independent of the size and material of the workpiece and the design of the magnetic abrasive machine tool. The theory results are verified experimentally.

G. Z. KREMEN; E. A. ELSAYED; V. I. RAFALOVICH

1996-01-01

347

Modeling of material removal in mechanical type advanced machining processes: a state-of-art review  

Microsoft Academic Search

Performance of any machining process is evaluated in terms of machining rate and surface finish produced. Higher machining rate and better surface finish are desirable for better performance of any machining process. Comprehensive qualitative and quantitative analysis of the material removal mechanism and subsequently the development of analytical model(s) of material removal (MR) are necessary for a better understanding and

Neelesh K. Jain; Vijay K. Jain

2001-01-01

348

Beyond the Memory Mechanism: Person-Selective and Nonselective Processes in Recognition of Personally Familiar Faces  

ERIC Educational Resources Information Center

Special processes recruited during the recognition of personally familiar people have been assumed to reflect the rich episodic and semantic information that selectively represents each person. However, the processes may also include person nonselective ones, which may require interpretation in terms beyond the memory mechanism. To examine this…

Sugiura, Motoaki; Mano, Yoko; Sasaki, Akihiro; Sadato, Norihiro

2011-01-01

349

Application of Parallel Processing to Probabilistic Fracture Mechanics Analysis of Gas Turbine Disks  

Microsoft Academic Search

A parallel processing methodology is developed and applied to improve the efficiency of probabilistic fracture mechanics analyses of gas turbine disks subject to metallurgical defects. A parallel processing spatial decomposition approach using a network of workstations and personal computers is described whereby each computer analyzes a region of the disk. The individual analyses are then combined to obtain the probability

Harry R. Millwater; Brian D. Shook; Sridhar Guduru; George Constantinides

350

Effect of processing conditions on morphology and mechanical properties of compatibilized polypropylene nanocomposites  

Microsoft Academic Search

This work focuses on the influence of processing conditions on the nanocomposites structure, i.e. intercalated or exfoliated, and on the enhancement of mechanical properties of polypropylene (PP) nanocomposites. These nanocomposites were prepared using the melt intercalation technique in a co-rotating intermeshing twin screw extruder. In order to optimise processing conditions, both screw speed and barrel temperature profile were changed. The

M. Modesti; A. Lorenzetti; D. Bon; S. Besco

2005-01-01

351

RECENT EXPERIENCE OF MECHANICAL VACUUM PUMPS REPLACING STEAM EJECTORS IN VOD AND VD PROCESSES  

Microsoft Academic Search

Investment in steel vacuum degassing processes, both in new plant and upgrades of existing plant, is continuing as steel companies see the opportunity to increase the value added component of their products by improving quality and supplying more specialty grade steels. In the area of ladle refining recent advances in the degassing process utilizing dry mechanical vacuum systems in place

Simon Bruce; BOC Edwards; Manor Royal; Vic Cheetham; Graham Legge

352

Biodrying for mechanical–biological treatment of wastes: A review of process science and engineering  

Microsoft Academic Search

Biodrying is a variation of aerobic decomposition, used within mechanical–biological treatment (MBT) plants to dry and partially stabilise residual municipal waste. Biodrying MBT plants can produce a high quality solid recovered fuel (SRF), high in biomass content. Here, process objectives, operating principles, reactor designs, parameters for process monitoring and control, and their effect on biodried output quality are critically examined.

C. A. Velis; P. J. Longhurst; G. H. Drew; R. Smith; S. J. T. Pollard

2009-01-01

353

Artificial neural networks modeling of mechanical property and microstructure evolution in the Tempcore process  

Microsoft Academic Search

In this study, the microstructures and the mechanical properties of steel bars treated by the Tempcore process have been investigated. In the Tempcore process, AISI 1020 steel bars of various diameters were used. In bars, unlike the self-tempering temperature and the extent of elongation, an increase in the amount of martensite was observed, which caused a consequential increase in yield

H Çetinel; H. A Özyi?it; L Özsoyeller

2002-01-01

354

Managing business processes across supply networks: the role of coordination mechanisms  

Microsoft Academic Search

The theory of network coordination provides a theoretical basis to explain how companies can overcome organizational boundaries and constraints to jointly manage business processes across supply networks. In particular, this paper focuses on Collaborative Planning, Forecasting and Replenishment (CPFR), a collaboration process whereby supply chain trading partners activate inter-firm coordination mechanisms to jointly plan key supply chain activities, from production

Pamela Danese; Pietro Romano; Andrea Vinelli

2004-01-01

355

Thermal Replication Trap  

NASA Astrophysics Data System (ADS)

The hallmark of living matter is the replication of genetic molecules and their active storage against diffusion. We have argued in the past that thermal convection can host the million-fold accumulation even of single nucleotides and at the same time trigger exponential replication [1]. Accumulation is driven by thermophoresis and convection in elongated chambers, replication by the inherent temperature cycling in convection. Optothermal pumping [2,3] allows to implement the thermal trap efficiently in a toroidal [4] or linear [5] geometry. Based on this method, we were in a position to combine accumulation and replication of DNA in the same chamber [5]. As we are missing a solid chemistry of prebiotic replication, we used as a proxy reaction for to replication the polymerase chain reaction. Convective flow both drives the DNA replicating polymerase chain reaction (PCR) while concurrent thermophoresis accumulates the replicated 143 base pair DNA in bulk solution. The time constant for accumulation is 92 s while DNA is doubled every 50 s. The length of the amplified DNA is checked with thermophoresis. Finite element simulations confirm the findings. The experiments explore conditions in pores of hydrothermal rock which can serve as a model environment for the origin of life and has prospects towards the first autonomous evolution, hosting the Darwin process by molecular selection using the thermophoretic trap. On the other side, the implemented continuous evolution will be able to breed well specified DNA or RNA molecules in the future. [4pt] [1] Baaske, Weinert, Duhr, Lemke, Russell and Braun, PNAS 104, 9346 (2007) [0pt] [2] Weinert, Kraus, Franosch and Braun, PRL 100, 164501 (2008) [0pt] [3] Weinert and Braun, Journal of Applied Physics 104, 104701 (2008) [0pt] [4] Weinert and Braun, Nano Letters 9, 4264 (2009) [0pt] [5] Mast and Braun, PRL 104, 188102 (2010)

Braun, Dieter

2011-03-01

356

Trapping of Radioactive Atoms: the Legnaro Francium Magneto-Optical Trap  

Microsoft Academic Search

Experiments aimed at laser cooling and trapping of radioactive atoms are nowadays operational at several laboratories. They open up a bridge between atomic and nuclear physics, allowing new precise spectroscopic measurements and detailed analysis of nuclear decay processes. A magneto-optical trap (MOT) for francium atoms is almost operational at the INFN Legnaro laboratories; its characterization and optimization are under way.

S. N. Atutov; V. Biancalana; A. Burchianti; R. Calabrese; L. Corradi; A. Dainelli; V. Guidi; B. Mali; C. Marinelli; E. Mariotti; L. Moi; E. Scansani; G. Stancari; L. Tomassetti; S. Veronesi

2003-01-01

357

Autophagy is required for trap formation in the nematode-trapping fungus Arthrobotrys oligospora.  

PubMed

Nematode-trapping fungi live mainly as saprobes in soil environments. When encountering nematodes, these fungi become 'carnivorous' and develop specialized trapping devices to attack their hosts for extracting nutrients, especially nitrogen source. Thus, nematode-trapping fungi are model organisms for understanding the molecular mechanism of the switch between saprobic and parasitic phases of pathogen life cycles. Arthrobotrys oligospora, one of the best-studied nematode-trapping fungi, mainly lives as a saprobe. In the presence of nematodes, A.oligospora enters the parasitic stage by forming adhesive reticulate traps to capture nematodes. In filamentous fungi, autophagy has been shown to be involved in morphogenesis and morphology. In this study, we demonstrate that autophagy is induced by nematodes during the early stage of trap formation in A.oligospora. Disruption of atg8 gene not only abolishes the nematode-induced autophagy, but also suppresses trap formation and reduces pathogenicity for nematodes. During the early stage of trap formation, the expression of genes involved in amino acid biosynthesis is upregulated and the transcriptional activity of GCN4 is induced in A.oligospora, suggesting that nematodes induce autophagy probably by triggering intracellular amino acid starvation. Autophagy is thus crucial for trap formation in A.oligospora during infection of nematodes. PMID:23864564

Chen, Yuan-Li; Gao, Ying; Zhang, Ke-Qin; Zou, Cheng-Gang

2013-08-01

358

Mechanism of Radial Redistribution of Energetic Trapped Ions Due to m=2/n=1 Internal Reconnection in Joint European Torus Shear Optimized Plasmas  

SciTech Connect

Internal radial redistribution of MeV energy ICRF-driven hydrogen minority ions was inferred from neutral particle analyzer measurements during large amplitude MHD activity leading to internal reconnection in Shear Optimized plasmas in the Joint European Torus (JET). A theory is developed for energetic ion redistribution during a reconnection driven by an m=2/n=1 internal kink mode. Plasma motion during reconnection generates an electric field which can change the energy and radial position of the energetic ions. The magnitude of ion energy change depends on the value of the safety factor at the plasma core from which the energetic ions are redistributed. A relation is found for corresponding change in canonical momentum. P(subscript phi), which leads to radial displacement of the ions. The model yields distinctive new features of energetic ion redistribution under such conditions. Predicted characteristics of ion redistribution are compared with the NPA measurements, and good correlation is found. Sometimes fast ions were transported to the plasma edge due to interaction with a long-lived magnetic island which developed after the reconnection and had chirping frequency in the laboratory frame. Convection of resonant ions trapped in a radially moving phase-space island is modeled to understand the physics of such events.

N.N. Gorelenkov; A. Gondhalekar; A.A. Korotkov; S.E. Sharapov; D. Testa; and Contributors to the EFDA-JET Workprogramme

2002-01-18

359

Towards understanding the molecular mechanism of the endocytosis-like process in the bacterium Gemmata obscuriglobus.  

PubMed

An endocytosis-like process of protein uptake in the planctomycete Gemmata obscuriglobus is a recently discovered process unprecedented in the bacterial world. The molecular mechanisms underlying this process are not yet characterized. A homolog of the MC (membrane-coating) proteins of eukaryotes has been proposed to be involved in the mechanism of this process, but its relationship to eukaryote proteins is controversial. However, a number of other proteins of G. obscuriglobus with domains homologous to those involved in endocytosis in eukaryotes can also be identified. Here we critically evaluate current bioinformatic knowledge, and suggest practical experimental steps to overcome the limits of bioinformatics in elucidating the molecular mechanism of endocytosis in bacteria. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey. PMID:24144586

Fuerst, John A; Sagulenko, Evgeny

2014-08-01

360

Towards wire-mediated coupling of trapped ions  

NASA Astrophysics Data System (ADS)

Our experiment aims at the transfer of quantum information between distant trapped ions using a macroscopic metal wire: an oscillating trapped ion induces oscillating image charges in the trap electrodes. If this current is sent to the electrodes of a second trap, it influences the motion of an ion in the second trap. With manageable trap geometries, a transfer rate of 1 ms between the motional states of the ions is possible. This ``wire-mediated'' coupling may be used not only for scaling up the quantum information processing devices, but also as a means to interconnect atomic systems to solid-state systems. Towards these goals, we are characterizing the behavior of our planar trap in terms of stray fields and electric field noise. In addition, we discuss experimental tools that we developed to characterize the trap operation in the presence of a floating wire which at a later stage will couple the two ions.

Selvarajan, Sankaranarayanan; Moeller, Soenke; Daniilidis, Nikos; Haeffner, Hartmut

2010-03-01

361

Energetics and forces of the Dionaea muscipula trap closing  

Microsoft Academic Search

The Venus flytrap is the most famous carnivorous plant. The electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf in 0.3s without mechanical stimulation of trigger hairs. Here we present results for direct measurements of the closing force of the trap of Dionaea muscipula Ellis after mechanical or electrical stimulation of the trap using the

Alexander G. Volkov; Veronica A. Murphy; Jacqueline I. Clemmons; Michael J. Curley; Vladislav S. Markin

362

Formation mechanisms of laboratory double layers  

NASA Technical Reports Server (NTRS)

The evolution processes of double layers were studied in a series of laboratory experiments. It was found that the existence of virtual cathode-type potential wells at the electron injection boundary was the dominant triggering mechanism. The rapid growth of the potential wells led to collisionless ion trapping and the establishment of the necessary trapped ion population. For double layers with small potential drops, collisionless ion trapping actually induced ion-ion streaming instabilities and the formation of ion phase-space vortices. In this regime, the system often exhibited relaxation-type oscillations which correspond to the disruption and the recovery of the double layers.

Chan, Chung

1987-01-01

363

Microstructural evolution and mechanical properties of high strength magneisum alloys fabricated by deformation processing  

NASA Astrophysics Data System (ADS)

The goal of this research was to develop high strength Mg by thermo-mechanical processing. Several novel techniques were developed to impart large plastic strains on Mg alloys and Mg based composites. The main emphasis of this work was on investigating the effect of different processing schemes on grain-refinement and texture modification of processed material. The room-temperature and elevated-temperature mechanical behavior of processed-Mg was studied in detail. Biaxial corrugated pressing, also known as alternate biaxial reverse corrugation processing was applied to twin-roll cast AZ31 Mg and warm-extruded ZK60 Mg. Friction stir processing to partial depths was applied to thixomolded AM60 Mg and warm-extruded ZK60 Mg. A new process called "bending reverse-bending", was developed and applied to hot rolled AZ31-H24 Mg. A Mg/Al laminated composite was developed by hot pressing and rolling. In processed condition, Mg alloys exhibit enhancement in room-temperature strength and ductility, as well as elevated temperature formability. It was concluded that improvement in mechanical properties of processed-Mg is strongly influenced by grain size and precipitates; while ductility largely depends on resulting deformation textures.

Mansoor, Bilal

364

Trap diversity and evolution in the family Droseraceae.  

PubMed

We review trapping mechanisms in the carnivorous flowering plant family Droseraceae (order Caryophyllales). Its members are generally known to attract, capture, retain and digest prey animals (mainly arthropods) with active snap-traps (Aldrovanda, Dionaea) or with active sticky flypaper traps (Drosera) and to absorb the resulting nutrients. Recent investigations revealed how the snap-traps of Aldrovanda vesiculosa (waterwheel plant) and Dionaea muscipula (Venus' flytrap) work mechanically and how these apparently similar devices differ as to their functional morphology and shutting mechanics. The Sundews (Drosera spp.) are generally known to possess leaves covered with glue-tentacles that both can bend toward and around stuck prey. Recently, it was shown that there exists in this genus a higher diversity of different tentacle types and trap configurations than previously known which presumably reflect adaptations to different prey spectra. Based on these recent findings, we finally comment on possible ways for intrafamiliar trap evolution. PMID:23603942

Poppinga, Simon; Hartmeyer, Siegfried R H; Masselter, Tom; Hartmeyer, Irmgard; Speck, Thomas

2013-07-01

365

Trap diversity and evolution in the family Droseraceae  

PubMed Central

We review trapping mechanisms in the carnivorous flowering plant family Droseraceae (order Caryophyllales). Its members are generally known to attract, capture, retain and digest prey animals (mainly arthropods) with active snap-traps (Aldrovanda, Dionaea) or with active sticky flypaper traps (Drosera) and to absorb the resulting nutrients. Recent investigations revealed how the snap-traps of Aldrovanda vesiculosa (waterwheel plant) and Dionaea muscipula (Venus’ flytrap) work mechanically and how these apparently similar devices differ as to their functional morphology and shutting mechanics. The Sundews (Drosera spp.) are generally known to possess leaves covered with glue-tentacles that both can bend toward and around stuck prey. Recently, it was shown that there exists in this genus a higher diversity of different tentacle types and trap configurations than previously known which presumably reflect adaptations to different prey spectra. Based on these recent findings, we finally comment on possible ways for intrafamiliar trap evolution.

Poppinga, Simon; Hartmeyer, Siegfried R.H.; Masselter, Tom; Hartmeyer, Irmgard; Speck, Thomas

2013-01-01

366

Exploring the effect of interfacial tension, viscosity, and flow rate on the effectiveness of capillary trapping of CO2  

NASA Astrophysics Data System (ADS)

Typical geologic carbon sequestration scenarios involve the injection of supercritical CO2 into an aquifer while displacing brine in what is equivalent to a water drainage process. Due to density differences, the CO2 will tend to buoyantly migrate upward until an impermeable barrier is encountered. This buoyant CO2 plume may persist for hundreds to thousands of years posing a challenge to ensuring the long-term integrity of CO2 storage. However, a potentially large fraction of the CO2 may be immobilized by one of several trapping mechanisms. Once injection stops, buoyant forces will continue to propel the supercritical CO2 upwards, while brine reoccupies the pore space in a water imbibition process, resulting in capillary trapping of some of the CO2. In addition, supercritical CO2 is partially miscible in brine and will dissolve in the brine forming a negatively buoyant phase (dissolution trapping), and will subsequently dissolve minerals to form bicarbonate and carbonate ions (ionic trapping) and may ultimately precipitate as mineral carbonates (mineral trapping). In the capillary trapping process, supercritical CO2 is immobilized by the imbibition process where capillary interactions lock isolated CO2 bubbles within unconnected rock pore space. These bubbles have significantly increased surface area with respect to brine and rock compared to bulk storage, and may facilitate enhanced dissolution of gaseous CO2 into the brine as well as chemical reactions. Thus, one approach to demonstrating storage security is the quantification of the rate and extent of these trapping mechanisms. We present experimental results based on computed x-ray microtomography (CMT) for quantifying capillary trapping mechanisms as a function of fluid properties using several pairs of analog fluids to span a range of potential supercritical CO2-brine conditions. Our experiments are conducted in a core-flood apparatus using synthetic porous media and we investigate capillary trapping by measuring trapped non-wetting phase area as a function of varying interfacial tension, viscosity, and wetting flow rate. Experiments are repeated for a single sintered glass bead core using three different non-wetting phase fluids and varying concentrations of surfactants to explore and separate the effects of interfacial tension, viscosity, and fluid flow rate. Analysis of the data demonstrates distinct and consistent differences in the amount of initial (i.e. following CO2 injection) and residual (i.e. following flood or WAG scheme) nonwetting phase occupancy as a function of fluid properties and flow rate. Further experimentation and analyses is needed, but these preliminary results indicate trends that can guide design of injection scenarios such that both initial and residual trapped gas occupancy is optimized.

Wildenschild, D.; Herring, A. L.; Carey, J. W.; Young, I. M.

2010-12-01

367

The low skill trap  

Microsoft Academic Search

Recently, it has become popular to argue that certain workers have fallen into a trap in which they have poor skills, few job opportunities and a low return on training, while others have not. This paper demonstrates how such a trap can occur within a simple matching model with rent sharing. Rent sharing diminishes the worker's incentive to acquire skills;

Ken Burdett; Eric Smith

2002-01-01

368

Fruit Fly Trap!  

NSDL National Science Digital Library

In this activity, compare the effectiveness of different traps to catch fruit flies. Is apple cider vinegar or white vinegar better at trapping these little insects? Use this activity to practice the scientific method or as a science fair project. This activity guide includes a step-by-step instructional video.

Center, Saint L.

2013-01-17

369

Steam trap monitor  

Microsoft Academic Search

A steam trap monitor positioned downstream of a steam trap in a closed steam system includes a first sensor (a hot finger) for measuring the energy of condensate and a second sensor (a cold finger) for measuring the total energy of condensate and steam in the line. The hot finger includes one or more thermocouples for detecting condensate level and

Ryan

1987-01-01

370

Steam trap monitor  

Microsoft Academic Search

A steam trap monitor positioned downstream of a steam trap in a closed steam system includes a first sensor (the combination of a hot finger and thermocouple well) for measuring the energy of condensate and a second sensor (a cold finger) for measuring the total energy of condensate and steam in the line. The hot finger includes one or more

Ryan; Michael J

1988-01-01

371

Steam trap monitor  

Microsoft Academic Search

For use in a closed steam system, apparatus coupled to a stream trap by means of a pipe and located downstream therefrom for monitoring the steam trap, the apparatus comprising: first sensing means in the pipe for determining the heat energy of a condensate flow in the pipe; second sensing means in the pipe for determining the heat energy of

Ryan

1988-01-01

372

Evaluating steam trap performance  

Microsoft Academic Search

This paper presents a method for evaluating the performance level of steam traps by preparing an economic analysis of several types to determine the equivalent uniform annual cost. A series of tests on steam traps supplied by six manufacturers provided data for determining the relative efficiencies of each unit. The comparison was made using a program developed for the Texas

Fuller

1985-01-01

373

Single beam acoustic trapping  

Microsoft Academic Search

A single beam acoustic device, with its relatively simple scheme and low intensity, can trap a single lipid droplet in a manner similar to optical tweezers. Forces in the order of hundreds of nanonewtons direct the droplet toward the beam focus, within the range of hundreds of micrometers. This trapping method, therefore, can be a useful tool for particle manipulation

Jungwoo Lee; Shia-Yen Teh; Abraham Lee; Hyung Ham Kim; Changyang Lee; K. Kirk Shung

2009-01-01

374

Neutrophil extracellular traps  

PubMed Central

Cancers prime neutrophils to release extracellular DNA traps through the systemic release of granulocyte colony-stimulating factor (G-CSF). We recently showed that these circulating neutrophil extracellular traps (NETs) promote the establishment of a pro-thrombotic state. The role of NETs in cancer biology and tumor progression may prove much more than an unfortunate side effect of cancer.

Demers, Melanie; Wagner, Denisa D.

2013-01-01

375

Microkinetic modeling of lean NOx trap chemistry  

SciTech Connect

A microkinetic chemical reaction mechanism capable of describing both the storage and regeneration processes in a fully formulated lean NO{sub x} trap is presented. The mechanism includes steps occurring on the precious metal, NO{sub x} storage, and oxygen storage sites of the catalyst. The complete reaction set is used with a transient plug flow reactor code (including boundary layer mass transfer) to simulate not only storage/regeneration cycles with a CO/H{sub 2} reductant, but also steady flow temperature sweep experiments that were previously analyzed with just a precious metal mechanism and a simpler steady state code. The results imply that NO{sub x} storage was not negligible during some of the temperature ramps, necessitating a re-evaluation of the precious metal kinetic parameters. The parameters for the entire mechanism are inferred by finding the best overall fit to the complete set of experiments. Rigorous thermodynamic consistency is enforced for parallel reaction pathways and with respect to known data for all gas phase species. It is found that nearly all of the basic experimental observations can be reproduced with the transient simulations.

Larson, Rich [Sandia National Laboratories (SNL); Chakravathy, Kalyana [Oak Ridge National Laboratory (ORNL); Pihl, Josh A [ORNL; Daw, C Stuart [ORNL

2012-01-01

376

Optically programmable excitonic traps  

PubMed Central

With atomic systems, optically programmed trapping potentials have led to remarkable progress in quantum optics and quantum information science. Programmable trapping potentials could have a similar impact on studies of semiconductor quasi-particles, particularly excitons. However, engineering such potentials inside a semiconductor heterostructure remains an outstanding challenge and optical techniques have not yet achieved a high degree of control. Here, we synthesize optically programmable trapping potentials for indirect excitons of bilayer heterostructures. Our approach relies on the injection and spatial patterning of charges trapped in a field-effect device. We thereby imprint in-situ and on-demand electrostatic traps into which we optically inject cold and dense ensembles of excitons. This technique creates new opportunities to improve state-of-the-art technologies for the study of collective quantum behavior of excitons and also for the functionalisation of emerging exciton-based opto-electronic circuits.

Alloing, Mathieu; Lemaitre, Aristide; Galopin, Elisabeth; Dubin, Francois

2013-01-01

377

Nonlinear integrable ion traps  

SciTech Connect

Quadrupole ion traps can be transformed into nonlinear traps with integrable motion by adding special electrostatic potentials. This can be done with both stationary potentials (electrostatic plus a uniform magnetic field) and with time-dependent electric potentials. These potentials are chosen such that the single particle Hamilton-Jacobi equations of motion are separable in some coordinate systems. The electrostatic potentials have several free adjustable parameters allowing for a quadrupole trap to be transformed into, for example, a double-well or a toroidal-well system. The particle motion remains regular, non-chaotic, integrable in quadratures, and stable for a wide range of parameters. We present two examples of how to realize such a system in case of a time-independent (the Penning trap) as well as a time-dependent (the Paul trap) configuration.

Nagaitsev, S.; /Fermilab; Danilov, V.; /SNS Project, Oak Ridge

2011-10-01

378

Trapping radioactive ions  

NASA Astrophysics Data System (ADS)

Trapping devices for atomic and nuclear physics experiments with radioactive ions are becoming more and more important at accelerator facilities. While about ten years ago only one online Penning trap experiment existed, namely ISOLTRAP at ISOLDE/CERN, meanwhile almost every radioactive beam facility has installed or plans an ion trap setup. This article gives an overview on ion traps in the operation, construction or planing phase which will be used for fundamental studies with short-lived radioactive nuclides such as mass spectrometry, laser spectroscopy and nuclear decay spectroscopy. In addition, this article summarizes the use of gas cells and radiofrequency quadrupole (Paul) traps at different facilities as a versatile tool for ion beam manipulation like retardation, cooling, bunching, and cleaning.

Kluge, H.-J.; Blaum, K.

2004-12-01

379

Modeling of the effect of intentionally introduced traps on hole transport in single-crystal rubrene  

NASA Astrophysics Data System (ADS)

Defects have been intentionally introduced in a rubrene single crystal by means of two different mechanisms: ultraviolet ozone (UVO) exposure and x-ray irradiation. A complete drift-diffusion model based on the mobility edge (ME) concept, which takes into account asymmetries and nonuniformities in the semiconductor, is used to estimate the energetic and spatial distribution of trap states. The trap distribution for pristine devices can be decomposed into two well defined regions: a shallow region ascribed to structural disorder and a deeper region ascribed to defects. UVO and x ray increase the hole trap concentration in the semiconductor with different energetic and spatial signatures. The former creates traps near the top surface in the 0.3-0.4 eV region, while the latter induces a wider distribution of traps extending from the band edge with a spatial distribution that peaks near the top and bottom interfaces. In addition to inducing hole trap states in the transport gap, both processes are shown to reduce the mobility with respect to a pristine crystal.

Dacuña, Javier; Desai, Amit; Xie, Wei; Salleo, Alberto

2014-06-01

380

TRAP1 Controls Mitochondrial Fusion/Fission Balance through Drp1 and Mff Expression  

PubMed Central

Mitochondria are dynamic organelles that change in response to extracellular stimuli. These changes are essential for normal mitochondrial/cellular function and are controlled by a tight balance between two antagonistic pathways that promote fusion and fission. Although some molecules have been identified to mediate the mitochondrial fusion and fission process, the underlying mechanisms remain unclear. Tumor necrosis factor receptor-associated protein 1 (TRAP1) is a mitochondrial molecule that regulates a variety of mitochondrial functions. Here, we examined the role of TRAP1 in the regulation of morphology. Stable TRAP1 knockdown cells showed abnormal mitochondrial morphology, and we observed significant decreases in dynamin-related protein 1 (Drp1) and mitochondrial fission factor (Mff), mitochondrial fission proteins. Similar results were obtained by transient knockdown of TRAP1 in two different cell lines, SH-SY5Y neuroblastoma cells and KNS-42 glioma cells. However, TRAP1 knockdown did not affect expression levels of fusion proteins. The reduction in Drp1 and Mff protein levels was rescued following treatment with the proteasome inhibitor MG132. These results suggest that TRAP1 regulates the expression of fission proteins and controls mitochondrial fusion/fission, which affects mitochondrial/cellular function.

Takamura, Hironori; Koyama, Yoshihisa; Matsuzaki, Shinsuke; Yamada, Kohei; Hattori, Tsuyoshi; Miyata, Shingo; Takemoto, Kana; Tohyama, Masaya; Katayama, Taiichi

2012-01-01

381

Radio Frequency Generation of an Electron Plasma in a Malmberg-Penning Trap  

NASA Astrophysics Data System (ADS)

The generation of an electron plasma via low-power Radio Frequency (RF) excitation has been observed in the Malmberg-Penning trap ELTRAP under ultra-high vacuum conditions. The process is sensitive to the RF parameters as well as to the trapping length. The electron heating mechanism necessary to reach the ionization energy of the residual gas has been modeled with the use of a simple one-dimensional iterative map, whose properties show a behavior similar to that of the Fermi acceleration map.

Paroli, B.; de Luca, F.; Maero, G.; Pozzoli, R.; Romé, M.

2010-06-01

382

Optimized free-form optical trapping systems.  

PubMed

We report a comprehensive process for designing and prototyping new and optimized optical trapping systems. A combination of traditional lens design strategies, simulation of optical forces, and high-end ultraprecision machining of optical free-form surfaces is applied to the realization of a highly specialized optical trapping system. The resulting compact and lightweight optical modules potentially open new classes of applications for optical manipulation. As an example we present a customized 3D trapping module made of a single piece of polymethylmethacrylate, with a large working distance of 650??m. PMID:22854491

Oeder, Andreas; Stoebenau, Sebastian; Sinzinger, Stefan

2012-01-15

383

Single trap dynamics in electrolyte-gated Si-nanowire field effect transistors  

NASA Astrophysics Data System (ADS)

Liquid-gated silicon nanowire (NW) field effect transistors (FETs) are fabricated and their transport and dynamic properties are investigated experimentally and theoretically. Random telegraph signal (RTS) fluctuations were registered in the nanolength channel FETs and used for the experimental and theoretical analysis of transport properties. The drain current and the carrier interaction processes with a single trap are analyzed using a quantum-mechanical evaluation of carrier distribution in the channel and also a classical evaluation. Both approaches are applied to treat the experimental data and to define an appropriate solution for describing the drain current behavior influenced by single trap resulting in RTS fluctuations in the Si NW FETs. It is shown that quantization and tunneling effects explain the behavior of the electron capture time on the single trap. Based on the experimental data, parameters of the single trap were determined. The trap is located at a distance of about 2 nm from the interface Si/SiO2 and has a repulsive character. The theory of dynamic processes in liquid-gated Si NW FET put forward here is in good agreement with experimental observations of transport in the structures and highlights the importance of quantization in carrier distribution for analyzing dynamic processes in the nanostructures.

Pud, S.; Gasparyan, F.; Petrychuk, M.; Li, J.; Offenhäusser, A.; Vitusevich, S. A.

2014-06-01

384

Wear Resistant Carbide-based Thermal Sprayed Coatings: Process, Properties, Mechanical Degradation and Wear  

NASA Astrophysics Data System (ADS)

Thermally sprayed ceramic-metallic composite (CerMet) materials consist of ceramic particles mainly in form of carbides reinforced by metallic binder exhibit unique microstructural and mechanical characteristics. Such structure brings in a novel combination of hardness and toughness enabling application of this class of material in wear resistant surfaces. Final deposit microstructure that defines the mechanical properties and wear performance of material depends on process parameters and starting material characteristics. Complex interaction of in-flight particles with supersonic flame, formation of complex defective deposit structure comprising of pores, cracks and splat boundaries make comprehending of interrelation of process, microstructure, properties and performance a difficult task. Additional challenge is development of systematic understanding on mechanical degradation, damage and wear mechanisms of cermet coatings due to their complex structure. This dissertation attempts to address these issues first by taking a systematic step by step approach, process map, to establish a correlation between process, particle state, microstructure and properties. Different strategies were proposed and examined to control the high velocity thermal spray process. This strategy assessment enabled a better control over in-flight particles state in high velocity thermal spray process and provided better understanding on interaction of in-flight particles with the flame. Further, possible advantages of reducing the carbide particle size from micron to nano in terms of mechanical properties and different wear performance were explored. It was suggested that poor wear performance of nano-structured coating is due to presence of brittle phases and less available binder promotes the excessive stress detrimental to load carrying capability of material. Material damage and wear mechanisms of coating under different tribological conditions were examined. The results suggest a correlation between relative abrasive particle size/carbide particle size and observed wear mechanism. Additionally effect of surface open porosities was highlighted. A surface damage mechanisms map was developed for coatings under increasing tangential force. This work has significant implications in improved material and process design of composite wear resistant structures and systems as it provides comprehensive qualitative insight to the wear mechanism of complex composite thermally sprayed structures under different tribological contact conditions. Additionally, this work provides an establishment between process, microstructure, properties and performance for this class of materials.

Ghabchi, Arash

385

An Approach for Characterizing Residual Mechanical Stress Caused by Packaging Processes  

Microsoft Academic Search

This paper reports on a new method for estimation and minimization of mechanical stress on MEMS sensor and actuator structures caused by to packaging processes based on flip-chip technology. For studying mechanical stress a test chip with silicon diaphragms was fabricated. A network of piezo-resistive solid-state resistors created by diffusion was used to measure the surface tension pattern between adjacent

Soeren Hirsch; Bertram Schmidt

386

Surface polymers of the nematode-trapping fungus Arthrobotrys oligospora.  

PubMed

The nematophagous fungus Arthrobotrys oligospora captures nematodes using adhesive polymers present on special hyphae (traps) which form a three-dimensional network. To understand further the adhesion mechanisms, A. oligospora surface polymers were visualized by transmission electron microscopy and characterized by chemical methods. Both traps and hyphae were surrounded by a fibrillar layer of extracellular polymers which stained with ruthenium red. The polymer layer was resistant to most of the chemicals and enzymes tested. However, part of the layer was removed by sonication in a Tris-buffer or by extraction in a chaotropic salt solution (LiCl), and the structure of the polymers was modified by treatment with Pronase E. Chemical analysis showed that the crude extracts of surface polymers removed by sonication or LiCl solution contained neutral sugars, uronic acids and proteins. Gel chromatography of the extracts revealed that the major carbohydrate-containing polymer(s) had a molecular mass of at least 100 kDa, containing neutral sugars (75% by weight, including glucose, mannose and galactose), uronic acids (6%) and proteins (19%). There was more polymer in mycelium containing trap-bearing cells than in vegetative hyphae. SDS-PAGE of the extracted polymers showed that the trap-forming cells contained at least one protein, with a molecular mass of approx. 32 kDa, not present on vegetative hyphae. Examining the capture of nematodes by traps of A. oligospora in which the layer of surface polymers was modified, or removed by chemical or enzymic treatments, showed that both proteins and carbohydrate surface polymers were involved in the adhesion process. PMID:1919501

Tunlid, A; Johansson, T; Nordbring-Hertz, B

1991-06-01

387

Formation of microtubule-based traps controls the sorting and concentration of vesicles to restricted sites of regenerating neurons after axotomy  

PubMed Central

Transformation of a transected axonal tip into a growth cone (GC) is a critical step in the cascade leading to neuronal regeneration. Critical to the regrowth is the supply and concentration of vesicles at restricted sites along the cut axon. The mechanisms underlying these processes are largely unknown. Using online confocal imaging of transected, cultured Aplysia californica neurons, we report that axotomy leads to reorientation of the microtubule (MT) polarities and formation of two distinct MT-based vesicle traps at the cut axonal end. Approximately 100 ?m proximal to the cut end, a selective trap for anterogradely transported vesicles is formed, which is the plus end trap. Distally, a minus end trap is formed that exclusively captures retrogradely transported vesicles. The concentration of anterogradely transported vesicles in the former trap optimizes the formation of a GC after axotomy.

Erez, Hadas; Malkinson, Guy; Prager-Khoutorsky, Masha; De Zeeuw, Chris I.; Hoogenraad, Casper C.; Spira, Micha E.

2007-01-01

388

The magnetism of a glacial aeolianite sequence from Lanzarote (Canary Islands): coupling between luvic calcisol formation and Saharan dust trapping processes during wet deposition events off northwestern Sahara  

NASA Astrophysics Data System (ADS)

In order to better document the climatic origin of pedogenized loess deposits west of Sahara, rock-magnetic measurements were performed on a Last Glacial coastal sand sequence from La Mala (LM) quarry (Lanzarote, Canary Islands) containing six interbedded loess-palaeosol units. Hysteresis and susceptibility data point to a coarse-grained magnetic enhancement in the coastal sand, which contrasts with the superparamagnetic (SP) to pseudo-single domain (PSD) behaviour of the Saharan loess and palaeosol. High- and low-temperature experiments show that oxidized titanomagnetite contributions dominate in the sand, while fine-grained (SP to PSD) iron oxidation products such as maghemite and goethite are evidenced in the Saharan loess/palaeosol units. At room temperature, the detrital PSD-multidomain titanomagnetite contribution of local origin is tentatively estimated from the AC-field dependence of magnetic susceptibility. Surface oxidation of detrital spinel grains and authigenesis of fine-grained iron oxides (including SP goethite) are proposed to explain the magnetic properties of the primarily fine, Saharan-dust-bearing material. The dry, local climate of the present-day and Late Holocene means that loess deposits are not preserved. The six pedogenized loess units, however, point to dust trapping under semi-arid, wetter conditions, probably illustrating periods of reduced latitudinal temperature gradients and climate variability of the North Atlantic climate, respectively. These findings suggest that both the Canary palaeosol and its content of (ultra)fine iron oxide might be constrained by (wet) deposition and trapping of fine Saharan dust.

Williamson, David; Jackson, Mike; Banerjee, Subir K.; Petit-Maire, Nicole

2004-06-01

389

Focused plasmonic trapping of metallic particles  

NASA Astrophysics Data System (ADS)

Scattering forces in focused light beams push away metallic particles. Thus, trapping metallic particles with conventional optical tweezers, especially those of Mie particle size, is difficult. Here we investigate a mechanism by which metallic particles are attracted and trapped by plasmonic tweezers when surface plasmons are excited and focused by a radially polarized beam in a high-numerical-aperture microscopic configuration. This contrasts the repulsion exerted in optical tweezers with the same configuration. We believe that different types of forces exerted on particles are responsible for this contrary trapping behaviour. Further, trapping with plasmonic tweezers is found not to be due to a gradient force balancing an opposing scattering force but results from the sum of both gradient and scattering forces acting in the same direction established by the strong coupling between the metallic particle and the highly focused plasmonic field. Theoretical analysis and simulations yield good agreement with experimental results.

Min, Changjun; Shen, Zhe; Shen, Junfeng; Zhang, Yuquan; Fang, Hui; Yuan, Guanghui; Du, Luping; Zhu, Siwei; Lei, Ting; Yuan, Xiaocong

2013-12-01

390

Trapped Electron Precession Shear Induced Fluctuation Decorrelation  

SciTech Connect

We consider the effects of trapped electron precession shear on the microturbulence. In a similar way the strong E x B shear reduces the radial correlation length of ambient fluctuations, the radial variation of the trapped electron precession frequency can reduce the radial correlation length of fluctuations associated with trapped electrons. In reversed shear plasmas, with the explicit dependence of the trapped electron precession shearing rate on B(subscript)theta, the sharp radial gradient of T(subscript)e due to local electron heating inside qmin can make the precession shearing mechanism more effective, and reduce the electron thermal transport constructing a positive feedback loop for the T(subscript)e barrier formation.

T.S. Hahm; P.H. Diamond; E.-J. Kim

2002-07-29

391

Mechanical Properties of Mg2Si/Mg Composites via Powder Metallurgy Process  

NASA Astrophysics Data System (ADS)

The mechanical properties of the Mg2Si/Mg composites solid-state synthesized from the mixed Mg-Si powders have been investigated. The macro-hardness (HRE) and the tensile strength of the composites increase with increasing the Si content and decreasing the Si size. The particle size of the synthesized Mg2Si depends on the initial Si size; the mechanical properties of the Mg2Si/Mg composite are remarkably improved by using fine Si particles or by decreasing the grain size of Mg matrix grains when the powder mixture was prepared via bulk mechanical alloying process.

Muramatsu, Hiroshi; Kondoh, Katsuyoshi; Yuasa, Eiji; Aizawa, Tatsuhiko

392

Low-damage direct patterning of silicon oxide mask by mechanical processing  

PubMed Central

To realize the nanofabrication of silicon surfaces using atomic force microscopy (AFM), we investigated the etching of mechanically processed oxide masks using potassium hydroxide (KOH) solution. The dependence of the KOH solution etching rate on the load and scanning density of the mechanical pre-processing was evaluated. Particular load ranges were found to increase the etching rate, and the silicon etching rate also increased with removal of the natural oxide layer by diamond tip sliding. In contrast, the local oxide pattern formed (due to mechanochemical reaction of the silicon) by tip sliding at higher load was found to have higher etching resistance than that of unprocessed areas. The profile changes caused by the etching of the mechanically pre-processed areas with the KOH solution were also investigated. First, protuberances were processed by diamond tip sliding at lower and higher stresses than that of the shearing strength. Mechanical processing at low load and scanning density to remove the natural oxide layer was then performed. The KOH solution selectively etched the low load and scanning density processed area first and then etched the unprocessed silicon area. In contrast, the protuberances pre-processed at higher load were hardly etched. The etching resistance of plastic deformed layers was decreased, and their etching rate was increased because of surface damage induced by the pre-processing. These results show that etching depth can be controlled by controlling the etching time through natural oxide layer removal and mechanochemical oxide layer formation. These oxide layer removal and formation processes can be exploited to realize low-damage mask patterns.

2014-01-01

393

Low-damage direct patterning of silicon oxide mask by mechanical processing.  

PubMed

To realize the nanofabrication of silicon surfaces using atomic force microscopy (AFM), we investigated the etching of mechanically processed oxide masks using potassium hydroxide (KOH) solution. The dependence of the KOH solution etching rate on the load and scanning density of the mechanical pre-processing was evaluated. Particular load ranges were found to increase the etching rate, and the silicon etching rate also increased with removal of the natural oxide layer by diamond tip sliding. In contrast, the local oxide pattern formed (due to mechanochemical reaction of the silicon) by tip sliding at higher load was found to have higher etching resistance than that of unprocessed areas. The profile changes caused by the etching of the mechanically pre-processed areas with the KOH solution were also investigated. First, protuberances were processed by diamond tip sliding at lower and higher stresses than that of the shearing strength. Mechanical processing at low load and scanning density to remove the natural oxide layer was then performed. The KOH solution selectively etched the low load and scanning density processed area first and then etched the unprocessed silicon area. In contrast, the protuberances pre-processed at higher load were hardly etched. The etching resistance of plastic deformed layers was decreased, and their etching rate was increased because of surface damage induced by the pre-processing. These results show that etching depth can be controlled by controlling the etching time through natural oxide layer removal and mechanochemical oxide layer formation. These oxide layer removal and formation processes can be exploited to realize low-damage mask patterns. PMID:24948891

Miyake, Shojiro; Yamazaki, Shohei

2014-01-01

394

Magnetic and mechanical properties of (Fe, Co)Pt bulk alloys prepared through various processing techniques  

Microsoft Academic Search

Magnetic and mechanical properties of Fe60Pt40, Fe60.5Pt39.5 and (Fe1-xCox)60.5Pt39.5 bulk alloys prepared by a number of processing techniques have been examined. Processing techniques include induction melting, mechanical milling (at ~77 K), hot and cold work, and melt extraction. Magnetic properties were determined in the temperature range from 300 to 1100 K using a vibrating sample magnetometer. Melt extracted Fe60.5P39.5 sample

S. Saha; C. J. Thong; M. Q. Huang; R. T. Obermyer; B. J. Zande; V. K. Chandhok; S. Simizu; S. G. Sankar

2002-01-01

395

Elemental strain and trapped space charge in thermoelectrical aging of insulating materials. Part 1: Elemental strain under thermo-electrical-mechanical stress  

Microsoft Academic Search

The life model proposed previously by the authors ascribes electrothermal aging to the formation and\\/or enlargement of nanovoids driven by electromechanical energy stored in local concentrations of space charge. In the previous work, the strain associated with the mechanical stress produced by the space charge center was derived using a macroscopic stress-strain relationship. For chain conformation changes on the molecular

L. A. Dissado; G. Mazzanti; G. C. Montanari

2001-01-01

396

Calibration of sound forces in acoustic traps.  

PubMed

A two-dimensional or transverse acoustic trapping and its capability to noninvasively manipulate micrometersized particles with focused sound beams were experimentally demonstrated in our previous work. To apply this technique, as in optical tweezers, for studying mechanical properties of and interactions among biological particles such as cells, the trapping forces must be calibrated against known forces, i.e., viscous drag forces exerted by fluid flows. The trapping forces and the trap stiffness were measured under various conditions and the results were reported in this paper. In the current experimental arrangement, because the trapped particles were positioned against an acoustically transparent mylar membrane, the ultrasound beam intensity distribution near the membrane must be carefully considered. The total intensity field (the sum of incident and scattering intensity fields) around the droplet was thus computed by finite element analysis (FEA) with the membrane included, and it was then used in the ray acoustics model to calculate the trapping forces. The membrane effect on trapping forces was discussed by comparing effective beam widths with and without the membrane. The FEA results found that the broader beam width, caused by the scattered beams from the neighboring membrane and the droplet, resulted in the lower intensity, or smaller force, on the droplet. The experimental results showed that the measured forces were as high as 64 nN. The trap stiffness, approximated as a linear spring, was estimated by linear regressions and found to be 1.3 to 4.4 nN/?m, which was on a larger scale than that of optical trapping estimated for red blood cells, a few tenths of piconewtons/nanometer. The experimental and theoretical results were in good agreement. PMID:20889418

Lee, Jungwoo; Lee, Changyang; Shung, K Kirk

2010-10-01

397

Calibration of Sound Forces in Acoustic Traps  

PubMed Central

A two-dimensional or transverse acoustic trapping and its capability to noninvasively manipulate micrometersized particles with focused sound beams were experimentally demonstrated in our previous work. To apply this technique, as in optical tweezers, for studying mechanical properties of and interactions among biological particles such as cells, the trapping forces must be calibrated against known forces, i.e., viscous drag forces exerted by fluid flows. The trapping forces and the trap stiffness were measured under various conditions and the results were reported in this paper. In the current experimental arrangement, because the trapped particles were positioned against an acoustically transparent mylar membrane, the ultrasound beam intensity distribution near the membrane must be carefully considered. The total intensity field (the sum of incident and scattering intensity fields) around the droplet was thus computed by finite element analysis (FEA) with the membrane included, and it was then used in the ray acoustics model to calculate the trapping forces. The membrane effect on trapping forces was discussed by comparing effective beam widths with and without the membrane. The FEA results found that the broader beam width, caused by the scattered beams from the neighboring membrane and the droplet, resulted in the lower intensity, or smaller force, on the droplet. The experimental results showed that the measured forces were as high as 64 nN. The trap stiffness, approximated as a linear spring, was estimated by linear regressions and found to be 1.3 to 4.4 nN/µm, which was on a larger scale than that of optical trapping estimated for red blood cells, a few tenths of piconewtons/nanometer. The experimental and theoretical results were in good agreement.

Lee, Jungwoo; Lee, Changyang; Shung, K. Kirk

2011-01-01

398

Development of a Plastic Injection Molding Processing Laboratory for Freshman Mechanical Engineering Technology Students  

NSDL National Science Digital Library

As is the case with many educational institutions that offer a MET degree, an introductory course in manufacturing materials and processes is required. At Penn State Erie, The Behrend College, we offer first-year Mechanical Engineering Technology (MET) students the introductory manufacturing materials and processes course. The course has both a lecture and laboratory segment. During the lab segment of the course, students have the opportunity to experience: material testing, plant tours, manufacturing processes, statistical process control, and inspection/measurement techniques. With 10 PIM machines, 3 extrusion lines, 2 thermoforming machines, and 2 blow molding machines, Penn State Behrend has the largest educational plastic injection molding (PIM) laboratory in the country. Collaborative efforts were initiated between the Mechanical Engineering Technology and Plastics Engineering Technology departments to enhance the learning experience. Resulting from the collaboration a decision was made to add a PIM laboratory to emphasize the lecture on plastic materials and processes. The PIM laboratory was developed to give the student an introduction to the PIM process, machine, mold and the effects of processing variables on the parts. Also, students would gain knowledge regarding the effects of part design on the process. Prior to the implementation of this lab, the students went on plant tours or were shown videos of the PIM process.

Meckley, Jonathan A.; Nitterright, Fredrick A.

2009-07-27

399

Laser trapping chemistry: from polymer assembly to amino acid crystallization.  

PubMed

Laser trapping has served as a useful tool in physics and biology, but, before our work, chemists had not paid much attention to this technique because molecules are too small to be trapped in solution at room temperature. In late 1980s, we demonstrated laser trapping of micrometer-sized particles, developed various methodologies for their manipulation, ablation, and patterning in solution, and elucidated their dynamics and mechanism. In the 1990s, we started laser trapping studies on polymers, micelles, dendrimers, and gold, as well as polymer nanoparticles. Many groups also reported laser trapping studies of nanoclusters, DNA, colloidal suspensions, etc. Following these research streams, we have explored new molecular phenomena induced by laser trapping. Gradient force leading to trapping, mass transfer by local heating, and molecular reorientation following laser polarization are intimately coupled with molecular cluster and aggregate formation due to their intermolecular interactions, which depend on whether the trapping position is at the interface/surface or in solution. In this Account, we summarize our systematic studies on laser trapping chemistry and present some new advances and our future perspectives. We describe the laser trapping of nanoparticles, polymers, and amino acid clusters in solution by focusing a continuous wave 1064 nm laser beam on the molecules of interest and consider their dynamics and mechanism. In dilute solution, nanoparticles with weak mutual interactions are individually trapped at the focal point, while laser trapping of nanoparticles in concentrated solution assembles and confines numerous particles at the focal spot. The assembly of polymers during their laser trapping extends out from the focal point because of the interpolymer interactions, heat transfer, and solvent flow. When the trapping laser is focused at an interface between a thin heavy water solution film of glycine and a glass substrate, the assembled molecules nucleate and evolve to a liquid-liquid phase separation, or they will crystallize if the trapping laser is focused on the solution surface. Laser trapping can induce spatiotemporally the liquid and solid nucleation of glycine, and the dense liquid droplet or crystal formed can grow to a bulk scale. We can control the polymorph of the formed glycine crystal selectively by tuning trapping laser polarization and power. These results provide a new approach to elucidate dynamics and mechanism of crystallization and are the fundamental basis for studying not only enantioselective crystallization but also confined polymerization, trapping dynamics by ultrashort laser pulses, and resonance effect in laser trapping. PMID:23094993

Sugiyama, Teruki; Yuyama, Ken-ichi; Masuhara, Hiroshi

2012-11-20

400

End Uses Mechanical Properties Settled By The Modified Sintering Conditions Of The Metal Injection Molding Process  

SciTech Connect

Most common mechanical applications require parts with specific properties as hard faced features. It is well known that treating parts under suitable atmospheres may improve hardness and strength yield of steels. Heat treatment process and more particularly thermo-chemical diffusion processes (such as carburizing or its variation: carbonitriding) can be performed to reach the industrial hardness profile requirements. In this work, a low-alloyed steel feedstock based on water soluble binder system is submitted to the MIM process steps (including injection molding, debinding and sintering). As-sintered parts are then treated under a low pressure carbonitriding treatment. This contribution focuses on preliminary results such as microstructural analyses and mechanical properties which are established at each stage of the process to determine and monitor changes.

Marray, Tarek [Laboratoire Materiaux, ECAM, 40 montee Saint Barthelemy, 69321, Lyon, Cedex 05 (France); Arts et Metiers ParisTech, MecaSurf Laboratory (EA 4496), 2, Cours des Arts et Metiers, 13617 Aix en Provence (France); Jaccquet, Philippe; Moinard-Checot, Delphine [Laboratoire Materiaux, ECAM, 40 montee Saint Barthelemy, 69321, Lyon, Cedex 05 (France); Arts et Metiers ParisTech, LaBoMaP, Rue Porte de Paris, 71250 CLUNY (France); Fabre, Agnes; Barrallier, Laurent [Arts et Metiers ParisTech, MecaSurf Laboratory (EA 4496), 2, Cours des Arts et Metiers, 13617 Aix en Provence (France)

2011-01-17

401

Trapping of radiation in plasmas  

SciTech Connect

The authors analyze the problem of radiation trapping (imprisonment) by the method of Holstein. The process is described by an integrodifferential equation which shows that the effective radiative decay rate of the system depends on the size and the shape of the active medium. Holstein obtains a global decay rate for a particular geometry by assuming that the radiating excited species evolves into a steady state spatial mode. The authors derive a new approximation for the trapped decay which has a space dependent decay rate and is easy to implement in a detailed computer simulation of a plasma confined within an arbitrary geometry. They analyze the line shapes that are relevant to a near-atmospheric-pressure mixture of He and Xe. This line-shape analysis can be utilized in either the Holstein formulae or the space-dependent decay approximation.

Riley, M.E.; Alford, W.J.

1995-06-01

402

Antihydrogen trapping assisted by sympathetically cooled positrons  

NASA Astrophysics Data System (ADS)

Antihydrogen, the bound state of an antiproton and a positron, is of interest for use in precision tests of nature's fundamental symmetries. Antihydrogen formed by carefully merging cold plasmas of positrons and antiprotons has recently been trapped in magnetic traps. The efficiency of trapping is strongly dependent on the temperature of the nascent antihydrogen, which, to be trapped, must have a kinetic energy less than the trap depth of \\sim 0.5\\;{{K}}\\;{{k}_{B}}. In the conditions in the ALPHA experiment, the antihydrogen temperature seems dominated by the temperature of the positron plasma used for the synthesis. Cold positrons are therefore of paramount interest in that experiment. In this paper, we propose an alternative route to make ultra-cold positrons for enhanced antihydrogen trapping. We investigate theoretically how to extend previously successful sympathetic cooling of positrons by laser-cooled positive ions to be used for antihydrogen trapping. Using simulations, we investigate the effectiveness of such cooling in conditions similar to those in ALPHA, and discuss how the formation process and the nascent antihydrogen may be influenced by the presence of positive ions. We argue that this technique is a viable alternative to methods such as evaporative and adiabatic cooling, and may overcome limitations faced by these. Ultra-cold positrons, once available, may also be of interest for a range of other applications.

Madsen, N.; Robicheaux, F.; Jonsell, S.

2014-06-01

403

Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP)  

Microsoft Academic Search

As a hot fabrication technology for micro scale parts, micro injection molding is receiving increasing market attention. Improving\\u000a mechanical properties of micro parts should be an important issue in the micro injection molding process. The relation between\\u000a weld line strength in micro injection molding parts and processing parameters is investigated. A visual mold with variotherm\\u000a unit is designed and constructed,

Lei Xie; Gerhard Ziegmann

2009-01-01

404

Crystal structures of [lamda] exonuclease in complex with DNA suggest an electrostatic ratchet mechanism for processivity  

Microsoft Academic Search

The exonuclease is an ATP-independent enzyme that binds to dsDNA ends and processively digests the 5'-ended strand to form 5' mononucleotides and a long 3' overhang. The crystal structure of exonuclease revealed a toroidal homotrimer with a central funnel-shaped channel for tracking along the DNA, and a mechanism for processivity based on topological linkage of the trimer to the DNA

Jinjin Zhang; Kimberly A. McCabe; Charles E. Bell

2011-01-01

405

Enhanced mechanical properties of graphene/copper nanocomposites using a molecular-level mixing process.  

PubMed

RGO flakes are homogeneously dispersed in a Cu matrix through a molecular-level mixing process. This novel fabrication process prevents the agglomeration of the RGO and enhances adhesion between the RGO and the Cu. The yield strength of the 2.5 vol% RGO/Cu nanocomposite is 1.8 times higher than that of pure Cu. The strengthening mechanism of the RGO is investigated by a double cantilever beam test using the graphene/Cu model structure. PMID:23983045

Hwang, Jaewon; Yoon, Taeshik; Jin, Sung Hwan; Lee, Jinsup; Kim, Taek-Soo; Hong, Soon Hyung; Jeon, Seokwoo

2013-12-10

406

Continuous hydrothermal processing of nano-crystalline particulates for chemical-mechanical planarization  

Microsoft Academic Search

A wide range of nano-crystalline, single and multi-component oxide\\/oxyhydroxide particulates, which may be potentially useful\\u000a as abrasives for chemical-mechanical planarization (CMP) processes, have been produced using a novel, flow-through hydrothermal\\u000a technology previously developed at the Pacific Northwest National Laboratory. The process, termed rapid thermal decomposition\\u000a of precursors in solution (RTDS), converts aqueous feed stock solutions containing metal salts and other

John G. Darab; Dean W. Matson

1998-01-01

407

Thermo mechanical modeling of turning process using an Arbitrary Lagrangian-Eulerian method  

Microsoft Academic Search

In this paper, thermo mechanical simulation of turning process has been developed using commercially available finite element analysis software, ABAQUS. A 2-D orthogonal cutting has been modeled using an Arbitrary Lagrangian-Eulerian (ALE) formulation. The Johnson-Cook plasticity model has been assumed to describe the material behavior during the process. Adaptive meshing dynamic explicit is also employed in this model to avoid

Wan Masrurah Bt Hairudin; Mokhtar B. Awang

2011-01-01

408

Processing of natural-fibre reinforced polymers and the resulting dynamic–mechanical properties  

Microsoft Academic Search

By means of dynamic–mechanical analysis (DMA), selected application-specific properties of flax- and hemp-fibre reinforced polypropylenes (PPs) have been determined for material characterisation. The compound samples were manufactured both by consolidation of hybrid non-wovens and compounding and injection moulding with the addition of natural fibres. The conditioning (long and short fibres), the manufacturing process and the processing parameters are the most

B Wielage; Th Lampke; H Utschick; F Soergel

2003-01-01

409

Imaging single-cell signaling dynamics with a deterministic high-density single-cell trap array.  

PubMed

Stochasticity in gene expression, protein or metabolite levels contributes to cell-cell variations, the analysis of which could lead to a better understanding of cellular processes and drug responses. Current technologies are limited in their throughput, resolution (in space, time, and tracking individual cells instead of population average) and the ability to control cellular environment. A few microfluidic tools have been developed to trap and image cells; however, in most designs available to date, there is a compromise among loading efficiency, speed, the ability to trap single cells, and density or number of trapped cells. To meet the needs of single-cell imaging studies, we developed a microfluidic platform for high-throughput capture and imaging of thousands of single cells. The optimized trapping mechanism enables 95% of the traps to be occupied with single cells, with a trap density of 860 traps/mm(2). The dense array allows up to 800 cells to be imaged simultaneously with a 4x objective and a typical camera setup. Capture occurs with low shear and 94% viability after 24 h. This platform is compatible with other upstream microfluidic components for complex cell stimulation patterns, and we show here the ability to measure heterogeneity in calcium oscillatory behavior in genetically identical cells and monitor kinetic cellular response to chemical stimuli. PMID:21809821

Chung, Kwanghun; Rivet, Catherine A; Kemp, Melissa L; Lu, Hang

2011-09-15

410

Optical trapping of dielectric nanoparticles in resonant cavities  

SciTech Connect

We theoretically investigate the opto-mechanical interactions between a dielectric nanoparticle and the resonantly enhanced optical field inside a high Q, small-mode-volume optical cavity. We develop an analytical method based on open system analysis to account for the resonant perturbation due to particle introduction and predict trapping potential in good agreement with three-dimensional (3D) finite-difference time-domain (FDTD) numerical simulations. Strong size-dependent trapping dynamics distinctly different from free-space optical tweezers arise as a consequence of the finite cavity perturbation. We illustrate single nanoparticle trapping from an ensemble of monodispersed particles based on size-dependent trapping dynamics. We further discover that the failure of the conventional dipole approximation in the case of resonant cavity trapping originates from a new perturbation interaction mechanism between trapped particles and spatially localized photons.

Hu Juejun [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716 (United States); Lin Shiyun; Crozier, Kenneth [School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts 02138 (United States); Kimerling, Lionel C. [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2010-11-15

411

Specific surface area and chemical reactivity of quartz powders during mechanical processing  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Quartz powders were submitted to mechanical processing. Black-Right-Pointing-Pointer The specific surface area and the chemical reactivity increased. Black-Right-Pointing-Pointer A model was developed to describe the observed processes. Black-Right-Pointing-Pointer The amount of powder processed at impact was estimated. Black-Right-Pointing-Pointer The surface density of reactive centers was also estimated by using a test reaction. -- Abstract: The present work focuses on the specific surface area increase, and on the related chemical reactivity enhancement of quartz powders submitted to mechanical processing. The mechanical treatment was carried out in a suitably developed ball mill allowing the control of the frequency and energy of the impacts between ball and reactor. The specific surface area was directly measured by nitrogen physisorption, whereas electron microscopy was used to determine the size distribution of powder particles. Based on the experimental results, a simplified mathematical model was developed to describe the process of specific surface area increase on a phenomenological basis. The model permits to gain valuable information on the amount of powder processed in individual impacts. The density of reactive centers at the surface of powder particles was also estimated by using the neutralization of a free radical as a test reaction. It is shown that the surface density of reactive centers increases with the energy of collisions.

Meloni, Paola [Dipartimento di Ingegneria Chimica e Materiali, Universita degli Studi di Cagliari, piazza d'Armi, I-09123 Cagliari (Italy) [Dipartimento di Ingegneria Chimica e Materiali, Universita degli Studi di Cagliari, piazza d'Armi, I-09123 Cagliari (Italy); Laboratorio per lo studio dei Materiali 'Colle di Bonaria', Universita degli Studi di Cagliari, via Ravenna, I-09100 Cagliari (Italy); Carcangiu, Gianfranco [Laboratorio per lo studio dei Materiali 'Colle di Bonaria', Universita degli Studi di Cagliari, via Ravenna, I-09100 Cagliari (Italy) [Laboratorio per lo studio dei Materiali 'Colle di Bonaria', Universita degli Studi di Cagliari, via Ravenna, I-09100 Cagliari (Italy); Istituto di Geologia Ambientale e Geoingegneria (IGAG), CNR, piazza d'Armi, I-09123 Cagliari (Italy); Delogu, Francesco, E-mail: delogu@dicm.unica.it [Dipartimento di Ingegneria Chimica e Materiali, Universita degli Studi di Cagliari, piazza d'Armi, I-09123 Cagliari (Italy)] [Dipartimento di Ingegneria Chimica e Materiali, Universita degli Studi di Cagliari, piazza d'Armi, I-09123 Cagliari (Italy)

2012-01-15

412

Do conscious perception and unconscious processing rely on independent mechanisms? A meta-contrast study.  

PubMed

There is currently no consensus regarding what measures are most valid to demonstrate perceptual processing without awareness. Likewise, whether conscious perception and unconscious processing rely on independent mechanisms or lie on a continuum remains a matter of debate. Here, we addressed these issues by comparing the time courses of subjective reports, objective discrimination performance and response priming during meta-contrast masking, under similar attentional demands. We found these to be strikingly similar, suggesting that conscious perception and unconscious processing cannot be dissociated by their time course. Our results also demonstrate that unconscious processing, indexed by response priming, occurs, and that objective discrimination performance indexes the same conscious processes as subjective visibility reports. Finally, our results underscore the role of attention by showing that how much attention the stimulus receives relative to the mask, rather than whether processing is measured by conscious discrimination or by priming, determines the time course of meta-contrast masking. PMID:24398259

Peremen, Ziv; Lamy, Dominique

2014-02-01

413

Electrical and mechanical properties as a processing condition in polyvinylchloride multi walled carbon nanotube composites.  

PubMed

We investigated the electrical conductivity (sigma) and mechanical property of polyvinylchloride/carbon nanotube composites as a function of the CNT content and processing time during a solid-state process of high speed vibration mixing (HSVM) and high energy ball milling (HEBM). Both processes were suggested to avoid high temperatures, solvents, chemical modification of carbon nanotubes. In this study, the percolation threshold (phi(c)) for electrical conduction is about 1 wt% CNT with a sigma value of 0.21 S/m, and the electrical conductivity is higher value than that reported by other researchers from melt mixing process or obtained from the other solid-state processes. We found that the dispersion of CNTs and morphology change from CNT breaking are closely related to sigma. Especially, a large morphology change in the CNTs was occurred at the specific processing time, and a significant decrease in the electrical conductivity of polyvinylchloride/carbon nanotube composite occurred in this condition. A meaningful increase of electrical properties and mechanical property is observed in the sample with about 1-2 wt% CNT contents sintered at 200 degrees C after the milling for 20 min by HEBM process. Our study indicates the proper process condition required to improve sigma of PVC/CNT composites. PMID:24245322

Song, Byung Ju; Ahn, Jin Woo; Cho, Kwon Koo; Roh, Jae Seung; Lee, Dong Yun; Yang, Yong Suk; Lee, Jae Beom; Hwang, Dae Youn; Kim, Hye Sung

2013-11-01

414

The use (and misuse) of sediment traps in coral reef environments: Theory, observations, and suggested protocols  

USGS Publications Warehouse

Sediment traps are commonly used as standard tools for monitoring “sedimentation” in coral reef environments. In much of the literature where sediment traps were used to measure the effects of “sedimentation” on corals, it is clear from deployment descriptions and interpretations of the resulting data that information derived from sediment traps has frequently been misinterpreted or misapplied. Despite their widespread use in this setting, sediment traps do not provide quantitative information about “sedimentation” on coral surfaces. Traps can provide useful information about the relative magnitude of sediment dynamics if trap deployment standards are used. This conclusion is based first on a brief review of the state of knowledge of sediment trap dynamics, which has primarily focused on traps deployed high above the seabed in relatively deep water, followed by our understanding of near-bed sediment dynamics in shallow-water environments that characterize coral reefs. This overview is followed by the first synthesis of near-bed sediment trap data collected with concurrent hydrodynamic information in coral reef environments. This collective information is utilized to develop nine protocols for using sediment traps in coral reef environments, which focus on trap parameters that researchers can control such as trap height (H), trap mouth diameter (D), the height of the trap mouth above the substrate (z o ), and the spacing between traps. The hydrodynamic behavior of sediment traps and the limitations of data derived from these traps should be forefront when interpreting sediment trap data to infer sediment transport processes in coral reef environments.

Storlazzi, C. D.; Field, M. E.; Bothner, M. H.

2011-01-01

415

Mechanical Modelling of Pultrusion Process: 2D and 3D Numerical Approaches  

NASA Astrophysics Data System (ADS)

The process induced variations such as residual stresses and distortions are a critical issue in pultrusion, since they affect the structural behavior as well as the mechanical properties and geometrical precision of the final product. In order to capture and investigate these variations, a mechanical analysis should be performed. In the present work, the two dimensional (2D) quasi-static plane strain mechanical model for the pultrusion of a thick square profile developed by the authors is further improved using generalized plane strain elements. In addition to that, a more advanced 3D thermo-chemical-mechanical analysis is carried out using 3D quadratic elements which is a novel application for the numerical modelling of the pultrusion process. It is found that the 2D mechanical models give relatively reasonable and accurate stress and displacement evolutions in the transverse direction as compared to the 3D model. Moreover, the generalized plane strain model predicts the longitudinal process induced stresses more similar to the ones calculated in the 3D model as compared with the plane strain model.

Baran, Ismet; Hattel, Jesper H.; Akkerman, Remko; Tutum, Cem C.

2014-05-01

416

Distinct shock acceleration processes — Evaluation of the magnetic trap dimensions formed upstream of an interplanetary shock using measurements of the ulysses spacecraft  

NASA Astrophysics Data System (ADS)

We analyze the acceleration signatures of energetic ions (E > 50 keV) and electrons (E > 30 keV) being observed on day 256 of the year 1992 UT, in the vicinity of the surface of a fast-mode quasi-perpendicular interplanetary hydromagnetic shock, using fine time resolution measurements by the HI-SCALE instrument onboard the Ulysses spacecraft,(s/c). The observations present strong evidence for the acceleration of energetic particles trapped within magnetic structures on the surface of the fast-mode shock. We discuss the flux-times profiles and particle distributions near the shock in the context of previous theoretical studies and models. Moreover we are in the procedure of evaluating the width L and amplitude A of the magnetic structure by using HI-SCALE measurements and a sinusoidal form geometry.

Marhavilas, P. K.; Sarris, E. T.; Anagnostopoulos, G. C.; Trochoutsos, P. C.

2003-08-01

417

The charge-trapping and triplet-triplet annihilation processes in organic light-emitting diodes: A duty cycle dependence study on magneto-electroluminescence  

NASA Astrophysics Data System (ADS)

We studied the magneto-electroluminescence (MEL) in tri-(8-hydroxyquinoline)-aluminum (Alq3)-based organic light-emitting devices through both steady-state and transient methods. As the magnetic field increases, the MEL exhibits a rapid rise, followed by the saturation tendency at all voltages in the steady-state measurement, but in the transient measurement it first increases to a maximum and then decreases to negative values when the driving voltages are higher than 8V. Furthermore, we found that the MEL strongly depends on the duty cycle of the pulse voltage. Finally, by employing the triplet-triplet annihilation model combined with the charge trapping effects, we explained the duty cycle dependence of MELs.

Peng, Qiming; Chen, Ping; Li, Feng

2013-01-01

418

Plagioclase as recorder of magma chamber processes in the Deccan Traps: Sr-isotope zoning and implications for Deccan eruptive event  

NASA Astrophysics Data System (ADS)

Deccan Trap flood basalt volcanism reached its peak 65.5 (±1) million years ago, giving rise to a 2.7 km thick lava pile that formed the Western Ghats range near Mumbai. The total duration of this activity cannot be constrained better than ±1 Ma by conventional Ar-dating techniques. It is also difficult to know whether there were short bursts of tremendous volcanic activity within that period which could have significantly impacted global climate. Here we employ diffusion relaxation modeling of 87Sr/86Sr zoning in plagioclase to obtain a better resolution on the life cycle of a magma chamber in order to provide a minimum constraint on the duration of the Western Ghats volcanic episode.

Borges, Melroy R.; Sen, Gautam; Hart, Garret L.; Wolff, John A.; Chandrasekharam, D.

2014-04-01

419

Intended process water management concept for the mechanical biological treatment of municipal solid waste  

Microsoft Academic Search

Accumulating operational experience in both aerobic and anaerobic mechanical biological waste treatment (MBT) makes it increasingly obvious that controlled water management would substantially reduce the cost of MBT and also enhance resource recovery of the organic and inorganic fraction. The MBT plant at Gescher, Germany, is used as an example in order to determine the quantity and composition of process

D. Weichgrebe; S. Maerker; T. Böning; H. Stegemann

420

Electrochemical properties of nanoparticle-based Ti-Co-Mg electrodes by mechanical alloying process.  

PubMed

The Ti-Co-Mg powders were synthesized by mechanical alloying process. The crystalline structure, particle size, surface morphology and the electrochemical performance of the Ti-Co-Mg alloy electrodes have been characterized by X-ray diffractometer, field emission-scanning electron microscopy, and charge-discharge cycler. PMID:20358974

Vediappan, Kumaran; Lee, Chang Woo

2010-05-01

421

Corn Silage Management: Effects of Hybrid, Chop Length, and Mechanical Processing on Digestion and Energy Content  

Microsoft Academic Search

Two experiments were conducted to evaluate the ef- fects of chop length and mechanical processing of two hybrids of whole plant corn on digestion and energy contentofthetotalmixedration(TMR).Theexperimen- tal designs in experiments 1 and 2 were 6 × 6 and 4 × 4 Latin squares, respectively. In the first experiment, Pioneer hybrid 3845 was harvested at three theoretical lengths of cut:

L. M. Johnson; J. H. Harrison; D. Davidson; W. C. Mahanna; K. Shinners

2003-01-01

422

Molecular dynamics simulation of the precision machining process including radiative and convective heat transfer mechanisms  

Microsoft Academic Search

During the machining process, extreme temperatures can occur in the various heat generation zones of the material. These temperatures can sometimes reach or exceed the melting point. To accurately represent the influence of this heating, heat transfer mechanisms must be incorporated i