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1

Physical mechanisms in double-carrier trap-charge limited transport processes in organic electroluminescent devices: A numerical study  

NASA Astrophysics Data System (ADS)

We have developed a numerical model to simulate the double-carrier injection trap-charge limited (TCL) transport processes in organic electroluminescent devices (OEDs). Current-voltage characteristics, energy and charge profiles are obtained and analyzed to understand the mechanisms governing the OED performance under TCL conditions. Good agreement with general experimental trends and previous analytical predictions are achieved. Dependencies on several important parameters (carrier injection level, device thickness, recombination constant, temperature, etc.) are also studied.

Shen, Jun; Yang, Jie

1998-06-01

2

Universal trapping mechanism in semiconductor nanocrystals.  

PubMed

Size tunability of the optical properties and inexpensive synthesis make semiconductor nanocrystals one of the most promising and versatile building blocks for many modern applications such as lasers, single-electron transistors, solar cells, and biological labels. The performance of these nanocrystal-based devices is however compromised by efficient trapping of the charge carriers. This process exhibits different features depending on the nanocrystal material, surface termination, size, and trap location, leading to the assumption that different mechanisms are at play in each situation. Here we revolutionize this fragmented picture and provide a unified interpretation of trapping dynamics in semiconductor nanocrystals by identifying the origins of this so far elusive detrimental process. Our findings pave the way for a general suppression strategy, applicable to any system, which can lead to a simultaneous efficiency enhancement in all nanocrystal-based technologies. PMID:23627433

Califano, Marco; Gómez-Campos, Francisco M

2013-04-29

3

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

4

Trapped Atomic Ions and Quantum Information Processing  

NASA Astrophysics Data System (ADS)

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, Schrödinger'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.; Knill, M.; Koelemeij, J. C. J.; Langer, C.; Ozeri, R.; Reichle, R.; Rosenband, T.; Schaetz, T.; Schmidt, P. O.; Seidelin, S.; Shiga, N.; Wesenberg, J. H.

2006-11-01

5

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

2007-12-07

6

Mechanical performance of rat, mouse and mole spring traps, and possible implications for welfare performance.  

PubMed

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. PMID:22768073

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

2012-06-29

7

Electron trapping by electric field reversal and Fermi mechanism  

SciTech Connect

We investigate the existence of electric field reversal in the negative glow of a dc discharge, its location, the width of the well trapping the electrons, the slow electrons scattering time, and the trapping time. Based on a stress-energy tensor analysis we show the inherent instability of the well. We suggest that the Fermi mechanism is a possible process for pumping out electrons from the trough, interrelated with electrostatic plasma instabilities. A power-law distribution function for trapped electrons is also obtained. Analytical expressions are derived which can be used to calculate these characteristics from geometrical dimensions and the operational parameters of the discharge.

Pinheiro, Mario J. [Department of Physics and Centro de Fisica de Plasmas, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)

2004-11-01

8

Electron trapping by electric field reversal and Fermi mechanism.  

PubMed

We investigate the existence of electric field reversal in the negative glow of a dc discharge, its location, the width of the well trapping the electrons, the slow electrons scattering time, and the trapping time. Based on a stress-energy tensor analysis we show the inherent instability of the well. We suggest that the Fermi mechanism is a possible process for pumping out electrons from the trough, interrelated with electrostatic plasma instabilities. A power-law distribution function for trapped electrons is also obtained. Analytical expressions are derived which can be used to calculate these characteristics from geometrical dimensions and the operational parameters of the discharge. PMID:15600767

Pinheiro, Mário J

2004-11-19

9

Unification of three multiphonon trap-assisted tunneling mechanisms  

NASA Astrophysics Data System (ADS)

There are three basic multiphonon trap-assisted tunneling (TAT) mechanisms in the gate leakage current of a metal-oxide-semiconductor (MOS) structure: the short-ranged trap potential, nonadiabatic interaction and electric field induced trap-band transitions. In this paper, a comparison of these three mechanisms is made for the first time in a single (Schenk's model) MOS structure. A properly box-normalized electron wave function in the SiO2 conduction band in an electric field is used to calculate the field ionization rate of a deep neutral trap. It is found that capture and emission rates of a deep neutral trap are almost the same in the short-ranged trap potential and nonadiabatic interaction induced TAT processes, so the two mechanisms give a similar contribution to the total TAT current. The calculated TAT current and the average relaxation energy (~1.5 eV) due to these two mechanisms are in good agreement with the experimental results. In contrast, capture and emission rates in Schenk's model are several orders smaller. The TAT current induced by this mechanism is also much smaller and can be ignored.

Zhang, Manhong; Huo, Zongliang; Yu, Zhaoan; Liu, Jing; Liu, Ming

2011-12-01

10

Molten Hydroxide Trapping Process for Radioiodine  

SciTech Connect

A molten hydroxide trapping process has been considered for removing radioiodine species from off-gas streams whereby iodine is reacted directly with molten hydroxides such as NaOH or KOH. The resulting product is the corresponding iodide, which can be separated by simple cooling of the molten mixture to grow the iodide primary phase once the mixture reaches 70-80 mol% in the iodide component. Thermodynamic analysis indicates that such a chemical process is highly favorable. Experimental testing of the trapping process using molecular iodine showed trapping of up to 96% of the volatile iodine. The trapping efficiency was dependent on operational parameters such as temperature and gas-melt contact efficiency, and higher efficiencies are expected as the process is further developed. While an iodide phase could be effectively isolated by slow cooling of a molten iodide-hydroxide mixture, the persistent appearance of hydroxide indicated that an appreciable solubility of hydroxide occurred in the iodide phase.

Trowbridge, L.D.

2003-01-28

11

Reactive Transport Modelling of CO2 Storage in Saline Aquifers to Elucidate Fundamental Processes, Trapping Mechanisms, and Sequestration Partitioning  

Microsoft Academic Search

The ultimate fate of CO injected into saline aquifers for environmental isolation is governed by three interdependent yet conceptually distinct processes: CO migration as a buoyant immiscible fluid phase, direct chemical interaction of this rising plume with ambient saline waters, and its indirect chemical interaction with aquifer and cap-rock minerals through the aqueous wetting phase. Each process is directly linked

J. W. Johnson; J. J. Nitao; K. G. Knauss

2004-01-01

12

Quantum mechanics in rotating-radio-frequency traps and Penning traps with a quadrupole rotating field  

SciTech Connect

Quantum-mechanical analysis of ion motion in a rotating-radio-frequency (rrf) trap or in a Penning trap with a quadrupole rotating field is carried out. Rrf traps were introduced by Hasegawa and Bollinger [Phys. Rev. A 72, 043404 (2005)]. The classical motion of a single ion in this trap is described by only trigonometric functions, whereas in the conventional linear radio-frequency (rf) traps it is by the Mathieu functions. Because of the simple classical motion in the rrf trap, it is expected that the quantum-mechanical analysis of the rrf traps is also simple compared to that of the linear rf traps. The analysis of Penning traps with a quadrupole rotating field is also possible in a way similar to the rrf traps. As a result, the Hamiltonian in these traps is the same as the two-dimensional harmonic oscillator, and energy levels and wave functions are derived as exact results. In these traps, it is found that one of the vibrational modes in the rotating frame can have negative energy levels, which means that the zero-quantum-number state (''ground'' state) is the highest energy state.

Abe, K.; Hasegawa, T. [Department of Physics, Keio University, Kanagawa 223-8522 (Japan)

2010-03-15

13

Hydrogen-Trapping Mechanisms in Nanostructured Steels  

NASA Astrophysics Data System (ADS)

Nanoprecipitation-hardened martensitic bearing steels (100Cr6) and carbide-free nanobainitic steels (superbainite) are examined. The nature of the hydrogen traps present in both is determined via the melt extraction and thermal desorption analysis techniques. It is demonstrated that 100Cr6 can admit large amounts of hydrogen, which is loosely bound to dislocations around room temperature; however, with the precipitation of fine coherent vanadium carbide traps, hydrogen can be immobilized. In the case of carbide-free nanostructured bainite, retained austenite/bainite interfaces act as hydrogen traps, while concomitantly retained austenite limits hydrogen absorption. In nanostructured steels where active hydrogen traps are present, it is shown that the total hydrogen absorbed is proportional to the trapped hydrogen, indicating that melt extraction may be employed to quantify trapping capacity.

Szost, B. A.; Vegter, R. H.; Rivera-Díaz-del-Castillo, Pedro E. J.

2013-10-01

14

Quantum Information Processing with Trapped Ions*  

NASA Astrophysics Data System (ADS)

Trapped strings of cold ions provide an ideal system for quantum information processing. The quantum information can be stored in individual ions and these qubits can be individually prepared, the corresponding quantum states can be manipulated and measured with nearly 100% detection efficiency. With a small ion-trap quantum computer based on two and three trapped Ca^+ ions as qubits we have generated in a pre-programmed way genuine quantum states. In particular, entangled states of two particles, i.e. Bell states [1], and of three particles, i.e. GHZ and W states [2], were generated using an algorithmic procedure and their decoherence was investigated. These states are of particular interest for the implementation of a three-ion quantum register: we have demonstrated selective read-out of single qubits (while protecting the other qubits) and manipulation of single qubits of the register conditioned on the read-out results. The generated states have been measured experimentally using a technique known as state tomography allowing the population and phase of the quantum system to be mapped. Moreover, quantum teleportation with trapped ions was implemented [3] and can be used as resource for the transfer of quantum information as well as for quantum information processing. *Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria, and Institut für Quantenoptik und Quanteninformation, "Osterreichische Akademie der Wissenschaften, Technikerstraße 25, A-6020 Innsbruck, Austria. *C. F. Roos et al., Phys. Rev. Lett. 92, 220402 (2004). *C. F. Roos et al., Science 304, 1478 (2004). *M. Riebe et al., Nature 429, 734 (2004).

Koerber, Timo

2005-05-01

15

Mechanical model of the ultrafast underwater trap of Utricularia  

Microsoft Academic Search

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

Marc Joyeux; Olivier Vincent; Philippe Marmottant

2011-01-01

16

Quantum information processing with two trapped cadmium ions  

NASA Astrophysics Data System (ADS)

Quantum information processing combines information theory with laws of quantum mechanics to provide an interesting new study that promises significant technological advances in the field of computation. The quest for a physical quantum information processor not only tests the limits of quantum mechanics but also motivates the development of new control techniques for quantum systems. This thesis documents the implementation of the necessary components of a quantum computer in a new atomic ion species, while demonstrating an entangling procedure that is uniquely insensitive to certain types of phase noise. Quantum bits are stored in the ground state hyperfine levels of individual trapped cadmium ions, and the collective vibration of the ions in the trap potential form a quantum databus through which information can be transferred. Quantum state measurements and initialization processes are accomplished through optical pumping, and quantum logic operations are performed through interactions with applied electromagnetic fields. The spin-dependent force, which is the underlying principle of many entanglement schemes for trapped ions, is investigated in detail in a series of "Schrodinger cat" experiments that generates entangled wavepackets well separated in the momentum-position phase space (alpha = 6). Phase control of the interaction in the gate scheme proposed by Molmer and Sorensen results in phase coherence between single-qubit rotations and a robust two-qubit entangling logic gate that can operate on magnetic-field insensitive "clock" qubits at finite temperature. The coherence time of the clock qubit (˜ 1s) is long compared to the gate time (˜ 100mus). Finally, quantum state tomography is performed on two ions, featuring a set of universal quantum logic gates that is sufficient for any quantum computation, with an entangling gate fidelity of 0.83. The combination of the tools developed here is sufficient to perform universal quantum computation. With the advent of scalable, multi-zone ion trap structures, the concept of a quantum computation device may become reality in the not so distant future.

Lee, Patricia J.

17

Ion-trap quantum information processing: Experimental status  

NASA Astrophysics Data System (ADS)

Atomic ions trapped in ultra-high vacuum form an especially well-understood and useful physical system for quantum information processing. They provide excellent shielding of quantum information from environmental noise, while strong, well-controlled laser interactions readily provide quantum logic gates. A number of basic quantum information protocols have been demonstrated with trapped ions. Much current work aims at the construction of large-scale ion-trap quantum computers using complex microfabricated trap arrays. Several groups are also actively pursuing quantum interfacing of trapped ions with photons.

Kielpinski, Dave

2008-12-01

18

Quantum information processing and quantum control with trapped atomic ions  

NASA Astrophysics Data System (ADS)

The role of trapped atomic ions in the field of quantum information processing is briefly reviewed. We discuss some of the historical developments that enabled ions to enter the field and then summarize the basic mechanisms required for logic gates and the use of the gates in demonstrating simple algorithms. We describe potential pathways to reach fault-tolerant error levels and large-scale devices, and highlight some of the main problems that will be faced in achieving these goals. Possible near-term applications in applied and basic science, such as in metrology and quantum simulation, are discussed.

Wineland, D. J.

2009-12-01

19

Investigations of Far-Off Resonance Trap Loading and Loss Mechanisms  

NASA Astrophysics Data System (ADS)

Far-off-resonance traps (FORT's), or dipole traps, are used for a many experiments, and could be useful for precision measurements of parity-nonconserving amplitudes, the electron electric dipole moment, and ?-decay asymmetries. However, light-assisted loading and loss processes in these traps are not well understood. We are studying these mechanisms in order to increase the size of samples collected in these tightly-confining non-magnetic traps. In particular, we have studied the dependence of these processes on the spatial and temporal overlap of the FORT with a magneto-optical trap (MOT) and optical molasses. We observe loading and loss rates that depend on the intensities and detunings of the MOT and molasses lasers. This work is supported by NSF and ONR.

Corwin, K. L.; Chupp, T. E.; Miller, K. W.; Wieman, C. E.

1998-05-01

20

Kinetics and Mechanism of Dionaea muscipula Trap Closing1[C][OA  

PubMed Central

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.

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

2008-01-01

21

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

22

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

23

Quantum information processing with trapped electrons and superconducting electronics  

NASA Astrophysics Data System (ADS)

We describe a parametric frequency conversion scheme for trapped charged particles, which enables a coherent interface between atomic and solid-state quantum systems. The scheme uses geometric nonlinearities of the potential of coupling electrodes near a trapped particle, and can be implemented using standard charged-particle traps. Our scheme does not rely on actively driven solid-state devices, and is hence largely immune to noise in such devices. We present a toolbox which can be used to build electron-based quantum information processing platforms, as well as quantum hybrid platforms using trapped electrons and superconducting electronics.

Daniilidis, Nikos; Gorman, Dylan J.; Tian, Lin; Häffner, Hartmut

2013-07-01

24

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

2011-02-18

25

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

26

Mechanisms of kinetic trapping in self-assembly and phase transformation  

PubMed Central

In self-assembly processes, kinetic trapping effects often hinder the formation of thermodynamically stable ordered states. In a model of viral capsid assembly and in the phase transformation of a lattice gas, we show how simulations in a self-assembling steady state can be used to identify two distinct mechanisms of kinetic trapping. We argue that one of these mechanisms can be adequately captured by kinetic rate equations, while the other involves a breakdown of theories that rely on cluster size as a reaction coordinate. We discuss how these observations might be useful in designing and optimising self-assembly reactions.

Hagan, Michael F.; Elrad, Oren M.; Jack, Robert L.

2011-01-01

27

[Neutrophil extracellular traps: a 2-faced host defense mechanism].  

PubMed

Neutrophils play a key role in the innate immune system, providing the first line of host defense. In addition to their ability to eliminate pathogens by phagocytosis and antimicrobial secretions, it has recently been shown that neutrophils can trap and kill microorganisms by the release of extracellular structures composed of DNA and antimicrobial proteins called neutrophil extracellular traps (NETs). Although physiological amounts of NETs are important as antimicrobial agents, high levels of NETs in circulation may result in severe tissue damage. Besides, the excessive generation of NETs or a disruption in their clearance mechanism might be associated with the development of certain autoimmune diseases. This review describes the structure, function and generation of NETs, and their possible implication in the initiation and/or progression of different diseases. PMID:22766060

Camicia, Gabriela; de Larrañaga, Gabriela

2012-07-04

28

Mechanical occlusions: diagnostic traps and key points of the report.  

PubMed

Management of mechanical occlusion, particularly of the small intestine, has altered considerably over recent years, with a change of paradigm and the indication for surgery depending on the cause of the occlusion and any signs of entrapment or strangulation. It is therefore important today to make a positive diagnosis of mechanical occlusion, to assess its degree, its location and its cause, and to look for signs of entrapment and strangulation. Only computer tomography can provide the answers to these different questions. The aim of this paper is to provide a reminder of the CT signs that enable us to confirm diagnosis of the various aspects of mechanical occlusion of the stomach and duodenum, small intestine or colon, to emphasize and illustrate the diagnostic traps in CT and to set out the key points of a CT report of mechanical occlusion. PMID:23773530

Taourel, P; Alili, C; Pages, E; Curros Doyon, F; Millet, I

2013-06-15

29

Enhancement of mechanical Q-factors by optical trapping  

NASA Astrophysics Data System (ADS)

The quality factor (Q) of a mechanical resonator is an important figure of merit for observing quantum behavior. We demonstrate a technique to push the quality factor of a micro-mechanical resonator beyond conventional material and fabrication limits by using an optical lattice to trap a particular motional mode. A majority of the resonator's energy is stored in the lossless optical potential, thereby strongly diluting the effect of material dissipation. The pendulum-like mechanical resonator consists of a suspended 10 ?m diameter, 140 nm thick Si02 disk attached to the substrate by a single thin tether. The disk is trapped at the intensity maximum of an optical lattice, and we observe a frequency increase of the center of mass from 6.2 KHz to 145 KHz with a 50 fold Q increase to a final value of 5.8x10^5. This technique shows a strong potential in bringing other micro-mechanical resonators, such as SiN membranes, into a low-loss regime where observation of quantum behavior in macroscopic devices at room temperature becomes possible.

Hood, J. D.; Ni, K.-K.; Norte, R.; Wilson, D. J.; Yu, S. P.; Jayich, A. M.; Painter, O.; Kimble, H. J.

2012-06-01

30

Regeneration process of ceramic foam diesel-particulate traps  

Microsoft Academic Search

Periodic regeneration of the diesel particulate trap is essential to maintain the collection efficiency and exhaust gas back pressure at acceptable levels. The objectives of this study are to describe the phenomenology of ceramic foam filter regeneration process and to present its mathematical model. Further simulation study is carried out to estimate the effects of various factors including fuel additive

K. Takama; T. Inove; K. Kobashi; T. Kogiso; K. Oishi

1984-01-01

31

Dissipation-Assisted Quantum Information Processing with Trapped Ions  

NASA Astrophysics Data System (ADS)

We introduce a scheme to perform dissipation-assisted quantum information processing in ion traps considering realistic decoherence rates, for example, due to motional heating. By means of continuous sympathetic cooling, we overcome the trap heating by showing that the damped vibrational excitations can still be exploited to mediate coherent interactions as well as collective dissipative effects. We describe how to control their relative strength experimentally, allowing for protocols of coherent or dissipative generation of entanglement. This scheme can be scaled to larger ion registers for coherent or dissipative many-body quantum simulations.

Bermudez, A.; Schaetz, T.; Plenio, M. B.

2013-03-01

32

Macrophage clearance of neutrophil extracellular traps is a silent process.  

PubMed

Neutrophil extracellular traps (NETs) facilitate the extracellular killing of pathogens. However, in recent years, excessive NET formation has been implicated in several pathological conditions. Indeed, NETs that are not removed from tissues or from the circulation might serve to trigger autoimmune responses. We observed that physiological amounts of DNase I do not suffice to completely degrade NETs in vitro, suggesting that additional mechanisms are required for the removal of these extracellular structures. We show in this article that human monocyte-derived macrophages are able to engulf NETs in a cytochalasin D-dependent manner, indicating that this is an active, endocytic process. Furthermore, preprocessing of NETs by DNase I facilitated their clearance by macrophages. In addition, both recombinant C1q and endogenous C1q derived from human serum were found to opsonize NETs, and this facilitated NET clearance. Upon internalization, NETs were apparently degraded in lysosomes, as treatment with chloroquine led to accumulation of extranuclear DNA in human monocyte-derived macrophages. Finally, uptake of NETs alone did not induce proinflammatory cytokine secretion, whereas LPS-induced production of IL-1?, IL-6, and TNF-? was promoted by the uptake of NETs. In summary, we show that macrophages are capable of clearance of NETs and that this occurs in an immunologically silent manner. PMID:23904163

Farrera, Consol; Fadeel, Bengt

2013-07-31

33

Vacancy trapping mechanism for hydrogen bubble formation in metal  

SciTech Connect

We reveal the microscopic vacancy trapping mechanism for H bubble formation in W based on first-principles calculations of the energetics of H-vacancy interaction and the kinetics of H segregation. Vacancy provides an isosurface of optimal charge density that induces collective H binding on its internal surface, a prerequisite for the formation of H{sub 2} molecule and nucleation of H bubble inside the vacancy. The critical H density on the vacancy surface before the H{sub 2} formation is found to be 10{sup 19}-10{sup 20} H atoms per m{sup 2}. We believe that such mechanism is generally applicable for H bubble formation in metals and metal alloys.

Liu Yuelin; Zhang Ying; Zhou Hongbo; Lu Guanghong; Liu Feng; Luo, G.-N. [Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

2009-05-01

34

EPR spin-trapping of protein radicals to investigate biological oxidative mechanisms  

Microsoft Academic Search

Summary.  Presently, free radicals and oxidants are considered to mediate from signaling circuits involved in physiology and pathology\\u000a to cell and tissue injury. The elucidation of these many inter-related processes requires a better understanding of cellular\\u000a oxidative mechanisms many of which are mediated by protein radicals. Here, we will discuss the potentialities of EPR spin-trapping\\u000a of protein radicals to unravel oxidative

O. Augusto; S. Muntz Vaz

2007-01-01

35

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

36

Spontaneous Firings of Carnivorous Aquatic Utricularia Traps: Temporal Patterns and Mechanical Oscillations  

Microsoft Academic Search

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

Olivier Vincent; Ivan Roditchev; Philippe Marmottant; Tom Waigh

2011-01-01

37

Enhancement of Mechanical Q Factors by Optical Trapping  

NASA Astrophysics Data System (ADS)

The quality factor of a mechanical resonator is an important figure of merit for various sensing applications and for observing quantum behavior. Here, we demonstrate a technique to push the quality factor of a micromechanical resonator beyond conventional material and fabrication limits by using an optical field to stiffen or trap a particular motional mode. Optical forces increase the oscillation frequency by storing most of the mechanical energy in a nearly lossless optical potential, thereby strongly diluting the effect of material dissipation. By placing a 130 nm thick SiO2 pendulum in an optical standing wave, we achieve an increase in the pendulum center-of-mass frequency from 6.2 to 145 kHz. The corresponding quality factor increases 50-fold from its intrinsic value to a final value of Q=5.8(1.1)×105, representing more than an order of magnitude improvement over the conventional limits of SiO2 for this geometry. Our technique may enable new opportunities for mechanical sensing and facilitate observations of quantum behavior in this class of mechanical systems.

Ni, K.-K.; Norte, R.; Wilson, D. J.; Hood, J. D.; Chang, D. E.; Painter, O.; Kimble, H. J.

2012-05-01

38

Trapping of Reactive Intermediates to Study Reaction Mechanisms in Cellulose Chemistry  

Microsoft Academic Search

Reaction with specific scavenger agents, so-called trapping, is\\u000a a direct way to prove the occurrence of reactive intermediates in a reaction system, and thus\\u000a to elucidate the underlying reaction mechanisms. After an introduction on chemical intermediates, chemical\\u000a trapping and the peculiarities of trapping methodology in the presence of cellulose, four chapters from\\u000a cellulose chemistry were selected to illustrate how trapping can be

Thomas Rosenau; Antje Potthast; Paul Kosma

39

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

40

Current transport mechanism in trapped oxides: A generalized trap-assisted tunneling model  

Microsoft Academic Search

A generalized trap-assisted tunneling (GTAT) model is proposed in this work, where an effective tunneling barrier of trapezoidal shape is considered, instead of the triangular barrier utilized in the conventional trap-assisted tunneling (TAT) model. It is demonstrated that trapezoidal barrier tunneling dominates at low electric fields (E<4 MV\\/cm), while triangular barrier tunneling contributes the main part of the tunneling current

Mau Phon Houng; Yeong Her Wang; Wai Jyh Chang

1999-01-01

41

Capillary trapping mechanisms in water-wet laminated rocks  

SciTech Connect

Most flooding experiments in sandstone cores are carried out either in almost homogeneous samples or in core samples of uncertain heterogeneity. As a result, the interaction of small-scale sedimentary heterogeneity with the fluid mechanics of water-oil displacement cannot be adequately understood or quantified. Because most clastic sediments show some degree of lamination, this might be expected to have a significant influence on both oil displacement efficiency and residual/remaining oil saturation. This paper reports results from low-rate, drainage/imbibition floods in a 20x10x1-cm water-wet slab of cross-laminated heterogeneous eolian sandstone. The distribution of porosity, initial water saturation and residual oil saturation were monitored with computerized-tomography (CT) scanning techniques. The low-rate inhibition floods show that between 30% and 55% of original oil may be trapped in isolated high-permeability laminae. This work shows the importance of recognizing the role of core-scale heterogeneity in the laboratory measurement of waterflood behavior (i.e., the interaction of capillary forces with rock structure, particularly lamination). The practice of performing high-rate floods on rock samples assumed to be homogeneous is unwise and can lead to erroneous conclusion. The results of this work have major implications for (1) two-phase petrophysical measurements; (2) assessment of residual/remaining oil, and (3) multiphase-flow scaleup.

Huang, Y.; Ringrose, P.S.; Sorbie, K.S. [Heriot-Watt Univ., Edinburgh (United Kingdom)

1995-11-01

42

Trap-free process and thermal limitations on large-periphery SiC MESFET for RF and microwave power  

Microsoft Academic Search

In this paper, we present recent results on an SiC MESFET and we describe two of the main limitation mechanisms encountered: the self-heating and the trapping effects. Results on recent MESFET devices processed by THALES Research and Technology (TRT), Colombes, France, show that the trapping effects has been solved by using epitaxial layers on a higher purity 4H-SiC semi-insulating substrate

Frédéric Villard; J.-P. Prigent; E. Morvan; C. Dua; C. Brylinski; F. Temcamani; P. Pouvil

2003-01-01

43

Current transport mechanism in trapped oxides: A generalized trap-assisted tunneling model  

NASA Astrophysics Data System (ADS)

A generalized trap-assisted tunneling (GTAT) model is proposed in this work, where an effective tunneling barrier of trapezoidal shape is considered, instead of the triangular barrier utilized in the conventional trap-assisted tunneling (TAT) model. It is demonstrated that trapezoidal barrier tunneling dominates at low electric fields (E<4 MV/cm), while triangular barrier tunneling contributes the main part of the tunneling current at high electric fields (E=6-8 MV/cm). The comparisons of this improved model and the results of the conventional TAT model at high and low electric fields are discussed. It is concluded that GTAT can more accurately model the current density-electric field (J-E) curves for the conduction enhancement of a trapped oxide film under various deposition conditions over a wider range of electric fields. This is confirmed by the comparative use of both TAT and GTAT models on experimental data obtained from existing reports. Furthermore, a simple method for determining the trap energy level is derived from the J-E relationship. This method provides a convenient way to characterize the trap levels inside the oxide layers, without the need of other complicated measurements. The developed GTAT model can be applied to the investigations of gate oxide reliability, especially the stress-related effects and impurity incorporated oxide films (i.e., SiOF or SiON).

Houng, Mau Phon; Wang, Yeong Her; Chang, Wai Jyh

1999-08-01

44

Spontaneous Firings of Carnivorous Aquatic Utricularia Traps: Temporal Patterns and Mechanical Oscillations  

PubMed Central

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.

Vincent, Olivier; Roditchev, Ivan; Marmottant, Philippe

2011-01-01

45

A mapping approach to synchronization in the 'Zajfman trap': stability conditions and the synchronization mechanism  

Microsoft Academic Search

We present a two particle model to explain the mechanism that stabilizes a bunch of positively charged ions in an 'ion trap resonator' (Pedersen et al 2001 Phys. Rev. Lett. 87 055001). The model decomposes the motion of the two ions into two mappings for the free motion in different parts of the trap and one for a compressing momentum

Tihamér Geyer; David J. Tannor

2004-01-01

46

Kibble-Zurek mechanism in a trapped ferromagnetic Bose-Einstein condensate  

NASA Astrophysics Data System (ADS)

Spontaneous spin vortex formation in a magnetic phase transition of a trapped spin-1 Bose-Einstein condensate is investigated based on mean-field theory. In a harmonic trapping potential, an inhomogeneous atomic density leads to spatial variations of the critical point, magnetization time, and spin correlation length. The Kibble-Zurek phenomena are shown to emerge even in such inhomogeneous spinor condensates, when the quench of the quadratic Zeeman energy is fast enough. For slow quench, the magnetized region gradually expands from the center of the trap, pushing out spin vortices, which hinders the Kibble-Zurek mechanism from occurring. The case of a toroidal trapping potential is also discussed.

Saito, Hiroki; Kawaguchi, Yuki; Ueda, Masahito

2013-10-01

47

Quantum information processing with two trapped cadmium ions  

Microsoft Academic Search

Quantum information processing combines information theory with laws of quantum mechanics to provide an interesting new study that promises significant technological advances in the field of computation. The quest for a physical quantum information processor not only tests the limits of quantum mechanics but also motivates the development of new control techniques for quantum systems. This thesis documents the implementation

Patricia J. Lee

2006-01-01

48

Development and application of in vivo molecular traps reveals that dynein light chain occupancy differentially affects dynein-mediated processes  

PubMed Central

The ability to rapidly and specifically regulate protein activity combined with in vivo functional assays and/or imaging can provide unique insight into underlying molecular processes. Here we describe the application of chemically induced dimerization of FKBP to create nearly instantaneous high-affinity bivalent ligands capable of sequestering cellular targets from their endogenous partners. We demonstrate the specificity and efficacy of these inducible, dimeric “traps” for the dynein light chains LC8 (Dynll1) and TcTex1 (Dynlt1). Both light chains can simultaneously bind at adjacent sites of dynein intermediate chain at the base of the dynein motor complex, yet their specific function with respect to the dynein motor or other interacting proteins has been difficult to dissect. Using these traps in cultured mammalian cells, we observed that induction of dimerization of either the LC8 or TcTex1 trap rapidly disrupted early endosomal and lysosomal organization. Dimerization of either trap also disrupted Golgi organization, but at a substantially slower rate. Using either trap, the time course for disruption of each organelle was similar, suggesting a common regulatory mechanism. However, despite the essential role of dynein in cell division, neither trap had a discernable effect on mitotic progression. Taken together, these studies suggest that LC occupancy of the dynein motor complex directly affects some, but not all, dynein-mediated processes. Although the described traps offer a method for rapid inhibition of dynein function, the design principle can be extended to other molecular complexes for in vivo studies.

Varma, Dileep; Dawn, Amrita; Ghosh-Roy, Anindya; Weil, Sarah J.; Ori-McKenney, Kassandra M.; Zhao, Yanqiu; Keen, James; Vallee, Richard B.; Williams, John C.

2010-01-01

49

Accessing novel developmental mechanisms in the mouse by gene trapping  

Microsoft Academic Search

Genetic analysis is a powerful method for analyzing the function of specific genes in development. I sought to identify novel genes in the mouse using a genetic analysis relying on the expression pattern and phenotype of mutated genes. To this end, I have conducted a gene trap screen using the vector $\\\\rm SA\\\\beta geo,$ a promoterless DNA construct that encodes

Daniel Scudder Wagner

1997-01-01

50

A preliminary assessment of the contribution of CO2 trapping mechanisms at the Ketzin pilot site  

NASA Astrophysics Data System (ADS)

The FP7 European project CO2CARE aims to support the large-scale demonstration of the CCS technology through the development of site abandonment procedures and technologies which guarantee the fulfilment of the requirements for geological CO2 Storage. One of these requirements is the evolution of the storage site towards long-term stability. Four trapping mechanisms are acting towards long-term stabilization and immobilisation of CO2: 1. Structural trapping, 2. Residual trapping, 3. Dissolution trapping, and 4. Mineral trapping. The quantitative contribution of each of these trapping mechanisms will be site- and time-specific. By means of numerical modelling the four trapping mechanisms are evaluated in two separate steps for the Ketzin pilot site, where CO2 is injected into a saline aquifer at a depth of about 630 m to 700 m. The contribution of structural, residual and dissolution trapping is determined by dynamic modelling using the Schlumberger Eclipse 100 black-oil simulator based on the latest version of the history matched static geological model of the Stuttgart Formation (CO2MAN project). Mineral trapping capacity is evaluated through geochemical batch simulations using the PHREEQC simulator. Fluid and mineral composition are provided by a broad set of core analysis and experimental determinations (CO2SINK and CO2MAN projects) conducted for the Ketzin pilot site. Data on the dissolved CO2 amount and water saturation supplied by the dynamic simulations are used to adjust the boundary conditions of the geochemical models. With regard to the total contribution of the four CO2 trapping mechanisms, being estimated for the time span of 3,000 years, the initial dominance of structural trapping decreases with the increase of dissolution trapping. It is expected that 50% of CO2 are dissolved in the formation fluid within 500 years after injection, wherefrom a fraction slowly starts to incorporate into minerals due to chemical precipitation (mineral trapping). Residual trapping is determined by the migration behaviour of CO2 and residual gas saturation among others. As for mineral trapping in particular, of all carbonate minerals included in the model (siderite, calcite, magnesite and dolomite), siderite is the only one precipitating at the Ketzin pilot site. Variations of the reservoir pressure (and therefore of the amount of dissolved CO2) in the expected range of 55 to 76 bar were found to have a negligible effect on mineral alteration. Decreasing the water saturation on the other hand, results in faster but quantitatively smaller reactions. The total change in mineral volume after 3,000 years can be considered irrelevant in terms of porosity changes.

Klein, E.; De Lucia, M.; Kempka, T.; Tillner, E.; Kühn, M.

2012-04-01

51

CONTINUOUS COLD TRAP FOR FLUORIDE VOLATILITY PROCESSING OF URANIUM  

Microsoft Academic Search

Reprocessing of enriched U solid fuels by both volatilization from a ; fused salt, and sorption-desorption purification, requires final condensation of ; UFâ in a solids condenser or cold trap. Work hns been done to develop a ; fluidized condenser for a continuous cold trap. Using the system, I-N, and an ; intermally cooled fluidized bed of inert carrier, tests

J. C. Bresee; P. R. Larson

1957-01-01

52

Immuno-spin trapping of protein and DNA radicals: “Tagging” free radicals to locate and understand the redox process  

Microsoft Academic Search

Biomolecule-centered radicals are intermediate species produced during both reversible (redox modulation) and irreversible (oxidative stress) oxidative modification of biomolecules. These oxidative processes must be studied in situ and in real time to understand the molecular mechanism of cell adaptation or death in response to changes in the extracellular environment. In this regard, we have developed and validated immuno-spin trapping to

Sandra E. Gomez-Mejiba; Zili Zhai; Hammad Akram; Leesa J. Deterding; Kenneth Hensley; Nataliya Smith; Rheal A. Towner; Kenneth B. Tomer; Ronald P. Mason; Dario C. Ramirez

2009-01-01

53

A mechanism study of sound wave-trapping barriers.  

PubMed

The performance of a sound barrier is usually degraded if a large reflecting surface is placed on the source side. A wave-trapping barrier (WTB), with its inner surface covered by wedge-shaped structures, has been proposed to confine waves within the area between the barrier and the reflecting surface, and thus improve the performance. In this paper, the deterioration in performance of a conventional sound barrier due to the reflecting surface is first explained in terms of the resonance effect of the trapped modes. At each resonance frequency, a strong and mode-controlled sound field is generated by the noise source both within and in the vicinity outside the region bounded by the sound barrier and the reflecting surface. It is found that the peak sound pressures in the barrier's shadow zone, which correspond to the minimum values in the barrier's insertion loss, are largely determined by the resonance frequencies and by the shapes and losses of the trapped modes. These peak pressures usually result in high sound intensity component impinging normal to the barrier surface near the top. The WTB can alter the sound wave diffraction at the top of the barrier if the wavelengths of the sound wave are comparable or smaller than the dimensions of the wedge. In this case, the modified barrier profile is capable of re-organizing the pressure distribution within the bounded domain and altering the acoustic properties near the top of the sound barrier. PMID:23967929

Yang, Cheng; Pan, Jie; Cheng, Li

2013-09-01

54

Molecular Ion Dissociation Processes in a Partially Cooled Electrostatic Trap  

SciTech Connect

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 Randy [ORNL; Bannister, Mark E [ORNL; Deng, Shihu [ORNL; FogleJr, Michael R [Auburn University, Auburn, Alabama; Thomas, R. D. [Stockholm University, Stockholm, Sweden

2011-01-01

55

Process Waste Assessment, Mechanics Shop.  

National Technical Information Service (NTIS)

This Process Waste Assessment was conducted to evaluate hazardous wastes generated in the Mechanics Shop. The Mechanics Shop maintains and repairs motorized vehicles and equipment on the SNL/California site, to include motorized carts, backhoes, street sw...

N. M. Phillips

1993-01-01

56

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

57

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

58

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

59

Bioluminescence is produced from a trapped firefly luciferase conformation predicted by the domain alternation mechanism.  

PubMed

According to the domain alternation mechanism and crystal structure evidence, the acyl-CoA synthetases, one of three subgroups of a superfamily of adenylating enzymes, catalyze adenylate- and thioester-forming half-reactions in two different conformations. The enzymes accomplish this by presenting two active sites through an ~140° rotation of the C-domain. The second half-reaction catalyzed by another subgroup, the beetle luciferases, is a mechanistically dissimilar oxidative process that produces bioluminescence. We have demonstrated that a firefly luciferase variant containing cysteine residues at positions 108 and 447 can be intramolecularly cross-linked by 1,2-bis(maleimido)ethane, trapping the enzyme in a C-domain-rotated conformation previously undocumented in the available luciferase crystal structures. The cross-linked luciferase cannot adenylate luciferin but is nearly fully capable of bioluminescence with synthetic luciferyl adenylate because it retains the ability to carry out the oxidative half-reaction. The cross-linked luciferase is apparently trapped in a conformation similar to those adopted by acyl-CoA synthetases as they convert acyl adenylates into the corresponding CoA thioesters. PMID:21707059

Branchini, Bruce R; Rosenberg, Justin C; Fontaine, Danielle M; Southworth, Tara L; Behney, Curran E; Uzasci, Lerna

2011-07-01

60

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

Microsoft Academic Search

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

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

2012-01-01

61

Evaluation of the Forrester-Hepburn mechanism as an artifact source in ESR spin-trapping.  

PubMed

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 that formed by genuine radical trapping. A hydroxylamine is formed by nucleophilic attack of the substrate on DMPO and subsequently oxidized to the respective nitroxide radical. One potential candidate for this artifact is the sulfur trioxide radical adduct (DMPO/(•)SO(3)(-)), 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 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. PMID:22004308

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

2011-11-22

62

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

63

Trap-induced resonances in controlled atomic collisions for quantum information processing  

Microsoft Academic Search

Controlled collisions of ultracold atoms in optical lattices provide new avenues for quantum control and quantum information processing. The ability to precisely vary lattice parameters and the rich internal structure of trapped atoms allow for novel state manipulation. In this research, we investigate and develop new methods for analyzing and designing coherent controlled collisions of ultracold atoms in separated traps.

Rene Stock

2005-01-01

64

Kibble-Zurek mechanism in a trapped ferromagnetic Bose-Einstein condensate.  

PubMed

Spontaneous spin vortex formation in a magnetic phase transition of a trapped spin-1 Bose-Einstein condensate is investigated based on mean-field theory. In a harmonic trapping potential, an inhomogeneous atomic density leads to spatial variations of the critical point, magnetization time, and spin correlation length. The Kibble-Zurek phenomena are shown to emerge even in such inhomogeneous spinor condensates, when the quench of the quadratic Zeeman energy is fast enough. For slow quench, the magnetized region gradually expands from the center of the trap, pushing out spin vortices, which hinders the Kibble-Zurek mechanism from occurring. The case of a toroidal trapping potential is also discussed. PMID:24025530

Saito, Hiroki; Kawaguchi, Yuki; Ueda, Masahito

2013-09-11

65

A serpinB1 regulatory mechanism is essential for restricting neutrophil extracellular trap generation.  

PubMed

NETosis (neutrophil extracellular trap [NET] generation), a programmed death pathway initiated in mature neutrophils by pathogens and inflammatory mediators, can be a protective process that sequesters microbes and prevents spread of infection, but it can also be a pathological process that causes inflammation and serious tissue injury. Little is known about the regulatory mechanism. Previously, we demonstrated that serpinb1-deficient mice are highly susceptible to pulmonary bacterial and viral infections due to inflammation and tissue injury associated with increased neutrophilic death. In this study, we used in vitro and in vivo approaches to investigate whether SerpinB1 regulates NETosis. We found that serpinb1-deficient bone marrow and lung neutrophils are hypersusceptible to NETosis induced by multiple mediators in both an NADPH-dependent and -independent manner, indicating a deeply rooted regulatory role in NETosis. This role is further supported by increased nuclear expansion (representing chromatin decondensation) of PMA-treated serpinb1-deficient neutrophils compared with wild-type, by migration of SerpinB1 from the cytoplasm to the nucleus of human neutrophils that is coincident with or preceding early conversion of lobulated (segmented) nuclei to delobulated (spherical) morphology, as well as by the finding that exogenous human recombinant SerpinB1 abrogates NET production. NETosis of serpinb1-deficient neutrophils is also increased in vivo during Pseudomonas aeruginosa lung infection. The findings identify a previously unrecognized regulatory mechanism involving SerpinB1 that restricts the production of NETs. PMID:23002442

Farley, Kalamo; Stolley, J Michael; Zhao, Picheng; Cooley, Jessica; Remold-O'Donnell, Eileen

2012-09-21

66

Energy storage and dispersion of surface acoustic waves trapped in a periodic array of mechanical resonators  

Microsoft Academic Search

It has been shown previously that surface acoustic waves can be efficiently trapped and slowed by steep ridges on a piezoelectric substrate, giving rise to two families of shear-horizontal and vertically polarized surface waves. The mechanisms of energy storage and dispersion are explored by using the finite element method to model surface acoustic waves generated by high aspect ratio electrodes.

Maria B. Dühring; Vincent Laude; Abdelkrim Khelif

2009-01-01

67

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

68

Eosinophil extracellular DNA traps: molecular mechanisms and potential roles in disease.  

PubMed

Eosinophil extracellular traps (EETs) are part of the innate immune response and are seen in multiple infectious, allergic, and autoimmune eosinophilic diseases. EETs are composed of a meshwork of DNA fibers and eosinophil granule proteins, such as major basic protein (MBP) and eosinophil cationic protein (ECP). Interestingly, the DNA within the EETs appears to have its origin in the mitochondria of eosinophils, which had released most their mitochondrial DNA, but were still viable, exhibiting no evidence of a reduced life span. Multiple eosinophil activation mechanisms are represented, whereby toll-like, cytokine, chemokine, and adhesion receptors can all initiate transmembrane signal transduction processes leading to the formation of EETs. One of the key signaling events required for DNA release is the activation of the NADPH oxidase. Here, we review recent progress made in the understanding the molecular mechanisms involved in DNA and granule protein release, discuss the presence of EETs in disease, speculate on their potential role(s) in pathogenesis, and compare available data on other DNA-releasing cells, particularly neutrophils. PMID:22981682

Yousefi, Shida; Simon, Dagmar; Simon, Hans-Uwe

2012-09-13

69

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

70

Trapping processes in CaS:Eu{sup 2+},Tm{sup 3+}  

SciTech Connect

CaS:Eu{sup 2+},Tm{sup 3+} is a persistent red phosphor. Thermoluminescence was measured under different excitation and thermal treatment conditions. The results reveal that the charge defects, created by substituting Tm{sup 3+} for Ca{sup 2+}, serve as hole traps for the afterglow at room temperature. Tm{sup 3+} plays the role of deep electron trapping centers, capturing electrons either through the conduction band or directly from the excited Eu{sup 2+} ions. These two processes, in which two different sites of Tm{sup 3+} are involved, correspond to two traps with different depths. (c) 2000 American Institute of Physics.

Jia, Dongdong [Department of Materials Science and Engineering, Tsinghua University, Beijing, (China); Jia, Weiyi [Department of Physics, University of Puerto Rico, Mayaguez, Puerto Rico 00681 (Puerto Rico); Evans, D. R. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States); Dennis, W. M. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States); Liu, Huimin [Department of Physics, University of Puerto Rico, Mayaguez, Puerto Rico 00681 (Puerto Rico); Zhu, Jing [Department of Materials Science and Engineering, Tsinghua University, Beijing, (China); Yen, W. M. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States)

2000-09-15

71

Quantum information processing and cavity QED experiments with trapped Ca+ ions  

NASA Astrophysics Data System (ADS)

Single trapped Ca+ ions, stored in a linear Paul trap and laser-cooled to the ground state of their harmonic quantum motion are used for quantum information processing. As a demonstration, composite laser pulse sequences were used to implement phase gate and CNOT gate operation. For this, Stark shifts on the qubit transitions were precisely measured and compensated. With a single ion stored inside a high-finesse optical cavity, a cavity mode can be coherently coupled to the qubit transition.

Gulde, S.; Häffner, H.; Riebe, M.; Lancaster, G.; Mundt, A.; Kreuter, A.; Russo, C.; Becher, C.; Eschner, J.; Schmidt-Kaler, F.; Chuang, I. L.; Blatt, R.

2003-04-01

72

THE EFFECT OF SULFUR ON METHANE PARTIAL OXIDATION AND REFORMING PROCESSES FOR LEAN NOX TRAP CATALYSIS  

SciTech Connect

Lean NOx trap catalysis has demonstrated the ability to reduce NOx emissions from lean natural gas reciprocating engines by >90%. The technology operates in a cyclic fashion where NOx is trapped on the catalyst during lean operation and released and reduced to N2 under rich exhaust conditions; the rich cleansing operation of the cycle is referred to as "regeneration" since the catalyst is reactivated for more NOx trapping after NOx purge. Creating the rich exhaust conditions for regeneration can be accomplished by catalytic partial oxidation of methane in the exhaust system. Furthermore, catalytic reforming of partial oxidation exhaust can enable increased quantities of H2 which is an excellent reductant for lean NOx trap regeneration. It is critical to maintain clean and efficient partial oxidation and reforming processes to keep the lean NOx trap functioning properly and to reduce extra fuel consumption from the regeneration process. Although most exhaust constituents do not impede partial oxidation and reforming, some exhaust constituents may negatively affect the catalysts and result in loss of catalytic efficiency. Of particular concern are common catalyst poisons sulfur, zinc, and phosphorous. These poisons form in the exhaust through combustion of fuel and oil, and although they are present at low concentrations, they can accumulate to significant levels over the life of an engine system. In the work presented here, the effects of sulfur on the partial oxidation and reforming catalytic processes were studied to determine any durability limitations on the production of reductants for lean NOx trap catalyst regeneration.

Parks, II, James E [ORNL; Ponnusamy, Senthil [ORNL

2006-01-01

73

Process Waste Assessment, Mechanics Shop  

SciTech Connect

This Process Waste Assessment was conducted to evaluate hazardous wastes generated in the Mechanics Shop. The Mechanics Shop maintains and repairs motorized vehicles and equipment on the SNL/California site, to include motorized carts, backhoes, street sweepers, trash truck, portable emergency generators, trencher, portable crane, and man lifts. The major hazardous waste streams routinely generated by the Mechanics Shop are used oil, spent off filters, oily rags, and spent batteries. The used off and spent off filters make up a significant portion of the overall hazardous waste stream. Waste oil and spent batteries are sent off-site for recycling. The rags and spent on filters are not recycled. They are disposed of as hazardous waste. Mechanics Shop personnel continuously look for opportunities to minimize hazardous wastes.

Phillips, N.M.

1993-05-01

74

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

NASA Astrophysics Data System (ADS)

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 and with a precision ( ?m/m) approaching 10-8. The CPT mass measurement program has concentrated so far on nuclides of importance to astrophysics. In particular, measurements have been obtained of isotopes along the rp-process path, in which energy is released from a series of rapid proton-capture reactions. An X-ray burst is one possible site for the rp-process mechanism which involves the accretion of hydrogen and helium from one star onto the surface of its neutron star binary companion. Mass measurements are required as key inputs to network calculations used to describe the rp-process in terms of the abundances of the nuclides produced, the light-curve profile of the X-ray bursts, and the energy produced. This paper will present the precise mass measurements made along the rp-process path with particular emphasis on the “waiting-point” nuclides 68Se and 64Ge.

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

2005-09-01

75

Institutional Trap  

Microsoft Academic Search

One of the main obstacles for successful economic development is the formation of institutional traps, inefficient yet stable norms of behaviour. Domination of barter exchange, arrears, corruption and black market activities are examples of institutional traps that have hampered reforms in transition economies. Institutional traps are supported by mechanisms of coordination, learning, linkage and cultural inertia. The acceleration of economic

Victor Polterovich

2007-01-01

76

Charge Propagation Dynamics in Temperature Quenching of Sm-Doped TiO2: Impedance Spectroscopy of Release Processes of Trapped Charges Determining Luminescence Intensity  

NASA Astrophysics Data System (ADS)

The mechanism of the temperature quenching of luminescence in samarium-doped titanium dioxide (TiO2:Sm) was investigated with electrical measurement techniques. Because electrical measurements are sensitive to charge dynamics, the indirect excitation processes of the Sm dopants, i.e., trapping and recombination of injected charges into the host TiO2, can be clarified. Complex impedance spectroscopy between 100 and 300 K revealed a correlation between the temperature quenching of TiO2:Sm and the trapping and recombination processes. Analyses using equivalent circuits revealed that the main factor determining the temperature quenching properties was delocalization of the trapped charges and decoupling of free charges in TiO2 from trapped charges. The delocalization and decoupling parameters were evaluated from the equivalent circuit constants, and a numerical model incorporating the determined values reproduced the experimentally observed temperature quenching of photoluminescence.

Ishii, Masashi; Towlson, Brian; Harako, Susumu; Zhao, Xin-wei; Komuro, Shuji; Hamilton, Bruce

2013-02-01

77

Defining brain wiring patterns and mechanisms through gene trapping in mice  

Microsoft Academic Search

The search to understand the mechanisms regulating brain wiring has relied on biochemical purification approaches in vertebrates and genetic approaches in invertebrates to identify molecular cues and receptors for axon guidance. Here we describe a phenotype-based gene-trap screen in mice designed for the large-scale identification of genes controlling the formation of the trillions of connections in the mammalian brain. The

Philip A. Leighton; Kevin J. Mitchell; Lisa V. Goodrich; Xiaowei Lu; Kathy Pinson; Paul Scherz; William C. Skarnes; Marc Tessier-Lavigne

2001-01-01

78

Mechanism and energetics of green fluorescent protein chromophore synthesis revealed by trapped intermediate structures  

PubMed Central

Green fluorescent protein has revolutionized cell labeling and molecular tagging, yet the driving force and mechanism for its spontaneous fluorophore synthesis are not established. Here we discover mutations that substantially slow the rate but not the yield of this posttranslational modification, determine structures of the trapped precyclization intermediate and oxidized postcyclization states, and identify unanticipated features critical to chromophore maturation. The protein architecture contains a dramatic ?80° bend in the central helix, which focuses distortions at G67 to promote ring formation from amino acids S65, Y66, and G67. Significantly, these distortions eliminate potential helical hydrogen bonds that would otherwise have to be broken at an energetic cost during peptide cyclization and force the G67 nitrogen and S65 carbonyl oxygen atoms within van der Waals contact in preparation for covalent bond formation. Further, we determine that under aerobic, but not anaerobic, conditions the Gly-Gly-Gly chromophore sequence cyclizes and incorporates an oxygen atom. These results lead directly to a conjugation-trapping mechanism, in which a thermodynamically unfavorable cyclization reaction is coupled to an electronic conjugation trapping step, to drive chromophore maturation. Moreover, we propose primarily electrostatic roles for the R96 and E222 side chains in chromophore formation and suggest that the T62 carbonyl oxygen is the base that initiates the dehydration reaction. Our molecular mechanism provides the basis for understanding and eventually controlling chromophore creation.

Barondeau, David P.; Putnam, Christopher D.; Kassmann, Carey J.; Tainer, John A.; Getzoff, Elizabeth D.

2003-01-01

79

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

80

Long-term Variations of CO2 Trapped in Different Mechanisms in Deep Saline Formations: A Case Study of the Songliao Basin, China  

SciTech Connect

The geological storage of CO{sub 2} in deep saline formations is increasing seen as a viable strategy to reduce the release of greenhouse gases to the atmosphere. There are numerous sedimentary basins in China, in which a number of suitable CO{sub 2} geologic reservoirs are potentially available. To identify the multi-phase processes, geochemical changes and mineral alteration, and CO{sub 2} trapping mechanisms after CO{sub 2} injection, reactive geochemical transport simulations using a simple 2D model were performed. Mineralogical composition and water chemistry from a deep saline formation of Songliao Basin were used. Results indicate that different storage forms of CO{sub 2} vary with time. In the CO{sub 2} injection period, a large amount of CO{sub 2} remains as a free supercritical phase (gas trapping), and the amount dissolved in the formation water (solubility trapping) gradually increases. Later, gas trapping decreases, solubility trapping increases significantly due to migration and diffusion of the CO{sub 2} plume, and the amount trapped by carbonate minerals increases gradually with time. The residual CO{sub 2} gas keeps dissolving into groundwater and precipitating carbonate minerals. For the Songliao Basin sandstone, variations in the reaction rate and abundance of chlorite, and plagioclase composition affect significantly the estimates of mineral alteration and CO{sub 2} storage in different trapping mechanisms. The effect of vertical permeability and residual gas saturation on the overall storage is smaller compared to the geochemical factors. However, they can affect the spatial distribution of the injected CO{sub 2} in the formations. The CO{sub 2} mineral trapping capacity could be in the order of ten kilogram per cubic meter medium for the Songliao Basin sandstone, and may be higher depending on the composition of primary aluminosilicate minerals especially the content of Ca, Mg, and Fe.

Zhang, Wei; Li, Yilian; Xu, Tianfu; Cheng, Huilin; Zheng, Yan; Xiong, Peng

2008-06-10

81

The mechanics of manufacturing processes  

SciTech Connect

Economic pressures, particularly related to the quality of manufactured goods and `time-to-market` are forcing designers to think not only in terms of product design but also in terms of integrated product and process design, and finally in terms of deterministic manufacturing planning and control. As a result of these three high level needs, there is now an even greater need for comprehensive simulations that predict material behavior during a manufacturing process, the stresses and/or temperatures on associated tooling, and the final-product integrity. The phrase `manufacturing processes` of course covers a broad scope; it includes semiconductor manufacturing, injection molding of polymers, metal machining and precision lapping, wood and textile production, and the final assembly of piece-parts into a consumer product. It can be seen from this partial listing that the fields of fluid mechanics, solid mechanics, dynamics and tribology can all play a role. The introduction to the paper will contain a review of manufacturing processes and describe where simulations have been successfully applied, and where simulations are still lacking. The best of the simulations are those where the models accurately fit the physical phenomena, where accurate constitutive equations are available, and where boundary conditions are realistic. Thus, the body of the paper will focus on the results from one of these more successful simulations. It has been used to predict the deflections of tooling and the most appropriate operating conditions for the manufacturing process under study. A new method for manufacturing planning is described. In this method, closed form, somewhat simplified, analytical models are used to determine manufacturing planning parameters and then the results from these simpler models are refined by the fuller simulations. A case study in machining parameter selection for peripheral finish milling operations is developed.

Wright, P.; Stori, J. [California Univ., Berkeley, CA (United States). Dept. of Mechanical Engineering; King, C. [Sandia National Labs., Albuquerque, NM (United States)

1996-10-01

82

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

83

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

84

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

85

Chemically assisted mechanical refrigeration process  

SciTech Connect

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

86

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

87

Chemically assisted mechanical refrigeration process  

SciTech Connect

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

88

Quantum Information Processing with Trapped 43Ca+ Ions.  

National Technical Information Service (NTIS)

We report on experiments with strings of laser-cooled Ca+ ions for quantum information processing. An experiment using the isotope 43Ca+ was set up from scratch. We devised techniques for loading and laser-cooling 43Ca+ ion strings, initializing the ions ...

R. Blatt

2008-01-01

89

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

90

Quantum Control, Quantum Information Processing, and Quantum-Limited Metrology with Trapped Ions  

Microsoft Academic Search

We briefly discuss recent experiments on quantum information processing using trapped ions at NIST. A central theme of this work has been to increase our capabilities in terms of quantum computing protocols, but we have also applied the same concepts to improved metrology, particularly in the area of frequency standards and atomic clocks. Such work may eventually shed light on

D. J. Wineland; D. Leibfried; M. D. Barrett; A. Ben-Kish; J. C. Bergquist; R. B. Blakestad; J. J. Bollinger; J. Britton; J. Chiaverini; B. Demarco; D. Hume; W. M. Itano; M. Jensen; J. D. Jost; E. Knill; J. Koelemeij; C. Langer; W. Oskay; R. Ozeri; R. Reichle; T. Rosenband; T. Schaetz; P. O. Schmidt; S. Seidelin

2005-01-01

91

Study of the aerodynamic trap for containerless laser materials processing in microgravity  

Microsoft Academic Search

In the context of containerless laser processing of glasses in microgravity, a systematic study of the aerodynamic trap (ADT) has been done on the ground at both ambient and very high temperatures (?2000 K). This work yielded a better understanding of the ADT and helped in improving its design. Experiments indicate that restoring force and sample stability depend upon the

Paul-François Paradis; François Babin; Jean-Marie Gagné

1996-01-01

92

Unraveling A Trap-and-Trigger Mechanism in the pH-Sensitive Self-Assembly of Spider Silk Proteins.  

PubMed

When the major ampulate spidroins (MaSp1) are called upon to form spider dragline silk, one of nature's most amazing materials, a small drop in pH must occur. Using a state-of-the-art simulation technique, constant pH molecular dynamics, we discovered a few residues that respond to the pH signal in the dimerization of the N-terminal domain (NTD) of MaSp1 which is an integral step in the fiber assembly. At neutral pH the deprotonation of Glu79 and Glu119 leads to water penetration and structural changes at the monomer-monomer binding interface. At strongly acidic pH, the protonation of Asp39 and Asp40 weakens the electrostatic attraction between the monomers. Thus, we propose a "trap-and-trigger" mechanism whereby the intermolecular salt-bridges at physiologically relevant pH conditions always act as a stabilizing "trap" favoring dimerization. As pH is lowered to about 6, Glu79 and Glu119 become protonated, triggering the dimerization and subsequent silk formation. We speculate that this type of mechanism is operative in many other pH-sensitive biological processes. PMID:22866209

Wallace, Jason A; Shen, Jana K

2012-02-15

93

Unraveling A Trap-and-Trigger Mechanism in the pH-Sensitive Self-Assembly of Spider Silk Proteins  

PubMed Central

When the major ampulate spidroins (MaSp1) are called upon to form spider dragline silk, one of nature’s most amazing materials, a small drop in pH must occur. Using a state-of-the-art simulation technique, constant pH molecular dynamics, we discovered a few residues that respond to the pH signal in the dimerization of the N-terminal domain (NTD) of MaSp1 which is an integral step in the fiber assembly. At neutral pH the deprotonation of Glu79 and Glu119 leads to water penetration and structural changes at the monomer-monomer binding interface. At strongly acidic pH, the protonation of Asp39 and Asp40 weakens the electrostatic attraction between the monomers. Thus, we propose a “trap-and-trigger” mechanism whereby the intermolecular salt-bridges at physiologically relevant pH conditions always act as a stabilizing “trap” favoring dimerization. As pH is lowered to about 6, Glu79 and Glu119 become protonated, triggering the dimerization and subsequent silk formation. We speculate that this type of mechanism is operative in many other pH-sensitive biological processes.

Wallace, Jason A.; Shen, Jana K.

2012-01-01

94

Optimization of the fabrication process for high trapped field MgB2 bulks  

NASA Astrophysics Data System (ADS)

The optimization of the sintering conditions of disk shaped bulk MgB2 superconductors with respect to the trapped field is described. Series of samples were prepared by varying the sintering temperatures between 700 and 950 °C. The temperature range was divided into three regions, namely the low (<750 °C), medium (<825 °C), and high (>850 °C) temperature region. Scanning electron microscopy and X-ray diffraction indicated that homogenous single phase MgB2 bulks were produced in the medium sintering temperature range. At this processing temperature range the highest trapped field was also achieved. Samples of 20 mm in diameter and 7 mm thick produced at 775 °C exhibited trapped field of 1.50 T at 20 K.

Muralidhar, M.; Ishihara, A.; Suzuki, K.; Fukumoto, Y.; Yamamoto, Y.; Tomita, M.

2013-11-01

95

Thermalization Processes in Quantum Mechanics  

NASA Astrophysics Data System (ADS)

In quantum mechanics, the emergence of thermalization processes from unitary evolution has remained one of the greatest challenges. The two outstanding theories of this issue by Srednicki and Tasaki cannot address the concepts of temperature, heat, and work. Here, we present a theory using multiple quenches to examine the thermalization processes to advance thermodynamics concepts. To perform multiple quenches, one can vary one single control parameter (?) in a series of time evolutions, which create a set of density operators. The average of these density operators results into a diagonal operator with probability distribution function that can describe the emerging ensembles. Measuring probability distribution functions of key physical observables, temperature, equal to the derivative of energy with respect to entropy, can be easily measured. Therefore, simulations via multiple quenches can mimic dynamics in open quantum systems with much cheaper computational cost. They allow (1) tuning of temperature and entropy via ?, (2) measuring work distribution functions from distributions of a reaction coordinate, and (3) computing free-energy changes via Jarzynski's Equality. We hope that this approach can provide a new foundation and open up new directions for studying control of quantum systems.

Ngo, Van; Haas, Stephan

2013-03-01

96

Self-trapping mechanism in green phosphorescent dye-doped polymer light-emitting diodes  

NASA Astrophysics Data System (ADS)

The mechanism for exciting electroluminescence (EL) in a green phosphorescent dye, iridium(III)tris(2-(4-tolyl)pyridinato-N,C2) (Ir(mppy)3), doped in a host blue-emitting conducting polymer, poly[9,9-di-n-hexyl-fluorenyl-2,7-diyl] (PFO), has been studied. Photoluminescence measurements have been made on PFO/Ir(mppy)3 (0-12%) composites to rule out the possibility of singlet exciton energy transfer from the host polymer to the green dye. EL measurements have also been made to study the behavior of the composites in the presence of dc bias. The dominant mechanism for energy transfer from PFO to Ir(mppy)3 is found to be self-trapping of the charge carriers in the dye molecules, due to the extremely low LUMO and high HOMO levels as compared with PFO, thereby producing EL in the green region.

Madhwal, Devinder; Rait, S. S.; Verma, A.; Kumar, A.; Onoda, M.; Bhatnagar, P. K.; Mathur, P. C.

2010-06-01

97

The mechanism of radical-trapping antioxidant activity of plant-derived thiosulfinates.  

PubMed

It has long been recognized that garlic and petiveria, two plants of the Allium genus--which also includes onions, leeks and shallots--possess great medicinal value. In recent times, the biological activities of extracts of these plants have been ascribed to the antioxidant properties of the thiosulfinate secondary metabolites allicin and S-benzyl phenylmethanethiosulfinate (BPT), respectively. Herein we describe our efforts to probe the mechanism of the radical-trapping antioxidant activity of these compounds, as well as S-propyl propanethiosulfinate (PPT), a saturated analog representative of the thiosulfinates that predominate in non-medicinal alliums. Our experimental results, which include thiosulfinate-inhibited autoxidations of the polyunsaturated fatty acid (ester) methyl linoleate, investigations of their decomposition kinetics, and radical clock experiments aimed at obtaining some quantitative insights into their reactions with peroxyl radicals, indicate that the radical-trapping activity of thiosulfinates is paralleled by their propensity to undergo Cope elimination to yield a sulfenic acid. Since sulfenic acids are transient species, we complement our experimental studies with the results of theoretical calculations aimed at understanding the radical-trapping behaviour of the sulfenic acids derived from allicin, BPT and PPT, and contrasting the predicted thermodynamics and kinetics of their reactions with those of the parent thiosulfinates. The calculations reveal that sulfenic acids have among the weakest O-H bonds known (ca. 70 kcal mol(-1)), and that their reactions with peroxyl radicals take place by a near diffusion-controlled proton-coupled electron transfer mechanism. As such, it is proposed that the abundance of a thiosulfinate in a given plant species, and the ease with which it undergoes Cope elimination to form a sulfenic acid, accounts for the differences in antioxidant activity, and perhaps medicinal value, of extracts of these plants. Interestingly, while the Cope elimination of 2-propenesulfenic acid from allicin is essentially irreversible, the analogous reaction of BPT is readily reversible. Thus, in the absence of chain-carrying peroxyl radicals (or other appropriately reactive trapping agent), BPT is reformed. PMID:21445384

Lynett, Philip T; Butts, Krista; Vaidya, Vipraja; Garrett, Graham E; Pratt, Derek A

2011-03-28

98

Opto-mechanical estimation of micro-trap with cold atoms via nonlinear stimulated Raman scattering spectrum  

NASA Astrophysics Data System (ADS)

High-gain resonant nonlinear Raman spectrum on trapped cold atoms within a high-finesse optical cavity is simply explained under a nonlinear opto-mechanical mechanism, and a proposal using it to detect frequency of micro-trap is presented. The enhancement of this scattering spectrum is due to a coherent Raman conversion between two different cavity modes mediated by collective vibrations of atoms with nonlinear opto-mechanical couplings. The physical conditions of this technique are roughly estimated on Rubidium atoms, and a simple quantum analysis as well as a multi-body semiclassical simulation on this nonlinear Raman spectrum is conducted.

Zhang, Lin

2013-05-01

99

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

PubMed

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. PMID:22275003

Zhang, Pengbo; Zhao, Jijun; Wen, Bin

2012-01-25

100

Correct trap type, size seen vital to energy efficiency  

SciTech Connect

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 and a directory of 25 steam-trap manufacturers accompany the article. (DCK)

Warrock, A.M.

1984-01-01

101

Mechanism of GeO2 resistive switching based on the multi-phonon assisted tunneling between traps  

NASA Astrophysics Data System (ADS)

Model of evenly distributed traps in bulk dielectric is proposed for the resistive memory switching mechanism. Switching from high resistance to the low resistance state is explained by several-fold increase in trap concentration after the application of switching voltage. Both high and low resistance conductivities are governed by multi-phonon ionization and tunneling between neighboring traps. Thermal trap energy for oxygen vacancy and electron effective mass for crystal ?-GeO2 were calculated using density functional theory and used for the fitting of our charge transport model of resistive memory. The model was verified on the TaN-GeO2-Ni structure with good semi-quantitative agreement with experiment.

Shaposhnikov, A. V.; Perevalov, T. V.; Gritsenko, V. A.; Cheng, C. H.; Chin, A.

2012-06-01

102

Mass measurements near the r-process path using the Canadian Penning Trap mass spectrometer  

NASA Astrophysics Data System (ADS)

The masses of 40 neutron-rich nuclides from Z=51 to 64 were measured at an average precision of ?m/m=10-7 using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a 252Cf spontaneous fission source in a helium gas catcher, approach the predicted path of the astrophysical r process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in ?-endpoint measurements. Differences in mass excess from the 2003 Atomic Mass Evaluation of up to 400 keV are seen, as well as systematic disagreement with various mass models.

Van Schelt, J.; Lascar, D.; Savard, G.; Clark, J. A.; Caldwell, S.; Chaudhuri, A.; Fallis, J.; Greene, J. P.; Levand, A. F.; Li, G.; Sharma, K. S.; Sternberg, M. G.; Sun, T.; Zabransky, B. J.

2012-04-01

103

Image processing and trapping of microscopic objects using a phase conjugate Michelson interferometer  

NASA Astrophysics Data System (ADS)

We report the feasibility study of a versatile optical configuration consisting of a phase conjugate Michelson interferometer in conjunction with microscopic imaging optics for image processing and trapping of microscopic objects. Our test samples include phase gratings, amplitude gratings (i.e., Ronchi rulings), polystyrene microspheres, and biological samples such as liposomes and yeast cells. We have experimentally demonstrated (1) the novelty filtering feature which enhances the image of moving phase objects by suppressing the stationary background, (2) contrast reversal which is useful for the imaging of light absorbing (or scattering) particles, (3) the aberration correction capability of the system to enhance the image quality of microscopic objects embedded in or otherwise distorted by aberrators, and (4) optical trapping of polystyrene microspheres. The potential of using this technique for the manipulation and diagnosis of biological cells and tissues is discussed.

Chiou, Arthur E.; Hong, John H.; Sonek, Gregory J.; Liu, Yagang; Berns, Michael W.

1994-07-01

104

The Slow Dynamics of the Zero-Range Process in the Framework of the Traps Model  

NASA Astrophysics Data System (ADS)

The relaxation dynamics of the zero-range process (ZRP) has been an interesting problem. In this study, we set up the relationship between the ZRP and a model of traps, and investigate the slow dynamics of the ZRP in the framework of the trap model. Through statistical quantities such as the average rest time, the particle distribution, the two-time correlation function and the average escape time, we find that the particle interaction, especially the resulting condensation, can significantly influence the dynamics. In the stationary state, both the average rest time and the average escape time caused by the attraction among particles are obtained analytically. In the transient state, a hierarchical nature of the aging dynamics is revealed by both simulations and scaling analysis. Moreover, by comparing the particle diffusion in both the transient state and the stationary state, we find that the closer the ZRP systems approach the stationary state, the more slowly the particles diffuse.

Qi, Kai; Tang, Ming; Cui, Ai-Xiang; Fu, Yan

2012-05-01

105

COLD TRAPS  

DOEpatents

A cold trap is presented for removing a condensable component from a gas mixture by cooling. It consists of a shell, the exterior surface of which is chilled by a refrigerant, and conductive fins welded inside the shell to condense the gas, and distribute the condensate evenly throughout the length of the trap, so that the trap may function until it becomes completely filled with the condensed solid. The contents may then be removed as either a gas or as a liquid by heating the trap. This device has particuinr use as a means for removing uranium hexafluoride from the gaseous diffusion separation process during equipment breakdown and repair periods.

Thompson, W.I.

1958-09-30

106

Mechanisms of Dry SO2 Control Processes.  

National Technical Information Service (NTIS)

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 ...

C. Apple M. E. Kelly

1982-01-01

107

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

108

The floating oil pool - A unique trapping mechanism at Kern River field  

SciTech Connect

Geologic reevaluation of the giant Kern River field, a 4 billion bbl oil accumulation, suggests a nontrapping oil emplacement mechanism not previously described in the literature. The field produces 12-14{degree} API oil from a shallow, thick sequence of stacked fluvial sands situated across a homocline that dips 4-5{degree} southwest. Migration of hydrocarbons generated in deeply buried Miocene shales ended in the Kern River field when the oil reached the top of the regional groundwater table, a surface that truncates the dipping beds in the subsurface. The oil floats on top of the groundwater and is confined by an updip seal consisting of simply gravity, or barometric pressure. Significant vertical changes in the groundwater support system in the geologic and historic past have probably been caused by climatic fluctuations or changes in the volume or location of the nearby Kern River. A recharged groundwater support system would have hydraulically lifted the floating oil into shallower sands; a depleted support system would have allowed the oil to flow downdip, leaving behind undersaturated dry oil sands. Lateral propagation of this floating oil pool is limited by the inability of the unpressured oil to overcome capillary resistances and opposing groundwater movements. Stratigraphic complexities and faulting occasionally influence oil distribution, but the upper limits of producible oil are determined by the configuration of the regional groundwater table. Other shallow, heavy San Joaquin Valley oil fields that lack definitive conventional trapping mechanisms probably can also be reclassified as floating oil pools.

Kodl, E.J. (PT Caltex Pacific Indonesia, Sumatra (Indonesia)); Eacman, J.C. (Texaco Producing, Inc., Bakersfield, CA (USA))

1990-05-01

109

Quantum Many-Body Theory and Mechanisms for Low Energy Nuclear Reaction Processes in Matter  

Microsoft Academic Search

Recently, a theoretical model of Bose-Einstein Condensation (BEC) mechanism has been developed to describe low-energy nuclear reaction in a quantum many-body system confined in a micro\\/nano scale trap. The BEC mechanism is applied to explain various anomalous results observed recently in experiments involved with low-energy nuclear reaction processes in matter and in acoustic cavitation. Experimental tests of the BEC mechanism

Y. E. Kim

2004-01-01

110

Quantum many-body theory and mechanisms for low energy nuclear reaction processes in matter  

Microsoft Academic Search

Recently, a theoretical model of Bose-Einstein Condensation (BEC) mechanism has been developed to describe low-energy nuclear reaction in a quantum many-body system confined in a micro\\/nano scale trap. The BEC mechanism is applied to explain various anomalous results observed recently in experiments involved with low-energy nuclear reaction processes in matter and in acoustic cavitation. Experimental tests of the BEC mechanism

Yeong E. Kim

2004-01-01

111

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

2011-10-24

112

Spin-dependent electronic processes and long-lived spin coherence of deep-level trap sites in CdS nanocrystals  

NASA Astrophysics Data System (ADS)

Carrier trapping in colloidal nanocrystals represents a major energy loss mechanism for excitonic states crucial to devices. Surprisingly little is known about the influence of the spin degree of freedom on the nature of these intrinsic trap centers or the types of coupling that these states experience. Here, a pulsed microwave optically detected magnetic resonance study is presented that aims to probe the interaction pathways existing between shallow band-edge trap states and the deep-level emissive chemical defect states responsible for the broad, low-energy emission common to CdS nanocrystals. Due to long spin coherence times (T2) of these states, Rabi flopping detected in the luminescence under magnetic resonance provides access to information regarding the modes of coupling of shallow-trapped electron-hole pairs, both of isolated species and of those in proximity to the emissive defect. Corresponding optically detected spin-echo experiments expose an extraordinarily long intrinsic spin coherence time (T2?1.6 ?s) for colloidal nanocrystals, and an electron spin-echo envelope modulation indicative of local spin interactions. This effect provides opportunities for gaining the detailed chemical and structural information needed in order to eliminate energy loss mechanisms during the synthetic process.

van Schooten, K. J.; Huang, J.; Talapin, D. V.; Boehme, C.; Lupton, J. M.

2013-03-01

113

Multiple optical traps with a single laser beam using a simple and inexpensive mechanical element  

Microsoft Academic Search

An ordinary wire mesh is utilized to facilitate the creation of multiple optical traps (tweezers) for mani- pulation of small micron or sub-micron particles. Each of the traps formed in this manner is continuous and the entire array is amenable to easy control. Our method is simple to implement, inexpensive, and obvi- ates the need to timeshare a laser beam

J. A. Dharmadhikari; A. K. Dharmadhikari; V. S. Makhija; D. Mathur

2007-01-01

114

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

115

Collisional and Radiative Processes in Adiabatic Deceleration, Deflection, and Off-Axis Trapping of a Rydberg Atom Beam  

SciTech Connect

A supersonic beam of Rydberg hydrogen atoms has been adiabatically deflected by 90 deg., decelerated to zero velocity in less than 25 {mu}s, and loaded into an electric trap. The deflection has allowed the suppression of collisions with atoms in the trailing part of the gas pulse. The processes leading to trap losses, i.e., fluorescence to the ground state, and transitions and ionization induced by blackbody radiation have been monitored over several milliseconds and quantitatively analyzed.

Seiler, Ch.; Hogan, S. D.; Schmutz, H.; Agner, J. A.; Merkt, F. [Laboratorium fuer Physikalische Chemie, ETH Zuerich, CH-8093 Zuerich (Switzerland)

2011-02-18

116

Mass measurements along the rp-process path using the Canadian Penning trap mass spectrometer  

NASA Astrophysics Data System (ADS)

The processes responsible for the creation of elements more massive than iron are not well understood. A possible scenario for their production involves the rapid capture of protons (rp-process), which is thought to occur in explosive astrophysical events such as novae and X-ray bursts. Mass measurements of the nuclides involved with uncertainties on the order of 100 keV or better are critical to determine the energy output of the events, the resulting nuclide abundances, and the process 'path' including its termination. Particularly important are the masses of 'waiting-point' nuclides along the rp-process path where the process stalls until the subsequent ?-decay of the nuclides. This contribution will discuss the precise (< 30 keV) mass measurements made of isotopes along the rp-process path using the Canadian Penning Trap mass spectrometer (located at the ATLAS facility of the Argonne National Laboratory). Most notably, our results include the masses of two critical waiting-point nuclides, ^64Ge and ^68Se, and masses of isotopes near the proposed end-point of the rp-process path. This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada and by the U.S. Department of Energy, Nuclear Physics Division, under Contract W-31-109-ENG-38.

Clark, J. A.; Vaz, J.; Wang, J. C.; Boudreau, C.; Barber, R. C.; Sharma, K. S.; Blank, B.; Heinz, A.; Levand, A. F.; Savard, G.; Seweryniak, D.; Trimble, W.; Zhou, Z.; Buchinger, F.; Crawford, J. E.; Gulick, S.; Lee, J. K. P.; Sprouse, G. D.

2003-10-01

117

Vibration-induced mobilization of trapped oil ganglia in porous media: experimental validation of a capillary-physics mechanism.  

PubMed

The development of methods for mobilizing residual organic liquids trapped in porous media is becoming increasingly important as world demand for oil increases and because of the need to remediate aquifers degraded by slow-dissolving organic contaminants. Low-frequency elastic wave stimulation is one such technique, but until recently the lack of a mechanistic understanding of the effects of vibration on mobilization of oil ganglia has prevented the method from being applied predictably in the field. Recently, a simple capillary-physics mechanism has been developed to explain vibration-induced mobilization of a trapped non-wetting organic phase in porous media. Specific predictions that follow from this hypothesized mechanism are that vibrations will be most effective in mobilizing trapped oil when the acceleration amplitude is within an optimal range of values (that depend on the magnitudes of the capillary forces trapping the ganglia and the imposed static pressure gradients) and for sufficiently low vibration frequencies. In this paper we describe two-dimensional glass micromodel experiments that support these predictions. PMID:16009227

Li, Wenqing; Vigil, R Dennis; Beresnev, Igor A; Iassonov, Pavel; Ewing, Robert

2005-09-01

118

Halogenated organic gas-induced lung toxicity by free radical mechanisms. An EPR/Spin trapping study  

SciTech Connect

Edemagenic gases have been studied to determine physicochemical properties and basic mechanism(s) of response. The reaction of phosgene with nitrone spin traps was investigated using EPR/Spin Trapping techniques. A carbamoyl monochloride intermediate was obtained. Isotopic substitution of (13)C-phosgene was employed to verify the hyperfine coupling constant assignments. Furthermore, applying EPR/Spin Trapping techniques several intermediate species were identified in the reaction of perfluoroisobutylene (PFIB) with nitrone and nitroso spin trap agents: a carbon dioxide radical ion (CO2), a carbamoyl monofluoride intermediate (+COF), and vinyl carbanions of PFIB. Nitrone compounds formed 1,3-cycloaddition products with PFIB under anaerobic and aprotic conditions. Nitroso compounds reacted with carbanions derived from PFIB, which raises the possibility that electron transfer reactions of this type might account for the observed nitroxides. From these studies it appears that the toxicity of PFIB may be correlated with its susceptibility to nucleophilic attack. In the case of phosgene, a propagated electron transfer catalysis may be partially responsible for the pathogenesis of acute lung injury from inhalation of phosgene.

Arroyo, C.M.

1993-05-13

119

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

2013-03-15

120

Molecular conversion processing of greenhouse gases of global warming effect and conversion units employing a solid particle trap  

US Patent & Trademark Office Database

Molecular conversion processing of greenhouse gases of global warming effect and conversion units employing a solid particle trap. This is an industrial process capable of changing the chemical composition of the greenhouse gases from any source, such as the internal combustion engine, factory chimney and others, through the conversion of gas molecules to form new compounds such as clean gases. This is done by molecular conversion processing conversion unit with a solid particle trap, consisting of a plasma conversion chamber that produces a plasma jet, and an electrostatic filter for the collection of solid particles.

2011-06-21

121

DYNAMOS: a numerical MOSFET model including quantum-mechanical and near-interface trap transient effects  

Microsoft Academic Search

A numerical MOSFET model (DYNAMOS) is presented. The present approach accounts for quantum effects in the semiconductor substrate by solving the self-consistent one-dimensional Schrodinger and Poisson equations. It also includes a transient model of interface and near-interface oxide traps based on Schockley–Read–Hall statistics. By extension, this model is able to simulate the charging\\/discharging of an arbitrary trap sheet present in

Pascal Masson; Jean-Luc Autran; Daniela Munteanu

2002-01-01

122

Switching mechanism transition induced by annealing treatment in nonvolatile Cu/ZnO/Cu/ZnO/Pt resistive memory: From carrier trapping/detrapping to electrochemical metallization  

NASA Astrophysics Data System (ADS)

ZnO/Cu/ZnO trilayer films sandwiched between Cu and Pt electrodes were prepared for nonvolatile resistive memory applications. These structures show resistance switching under electrical bias both before and after a rapid thermal annealing (RTA) treatment, while it is found that the resistive switching effects in the two cases exhibit distinct characteristics. Compared with the as-fabricated device, the memory cell after RTA demonstrates remarkable device parameter improvements including lower threshold voltages, lower write current, and higher Roff/Ron ratio. A high-voltage forming process is avoided in the annealed device as well. Furthermore, the RTA treatment has triggered a switching mechanism transition from a carrier trapping/detrapping type to an electrochemical-redox-reaction-controlled conductive filament formation/rupture process, as indicated by different features in current-voltage characteristics. Both scanning electron microscopy observations and Auger electron spectroscopy depth profiles reveal that the Cu charge trapping layer in ZnO/Cu/ZnO disperses uniformly into the storage medium after RTA, while x-ray diffraction and x-ray photoelectron spectroscopy analyses demonstrate that the Cu atoms have lost electrons to become Cu2+ ions after dispersion. The above experimental facts indicate that the altered status of Cu in the ZnO/Cu/ZnO trilayer films during RTA treatment should be responsible for the switching mechanism transition. This study is envisioned to open the door for understanding the interrelation between different mechanisms that currently exist in the field of resistive memories.

Yang, Y. C.; Pan, F.; Zeng, F.; Liu, M.

2009-12-01

123

In-depth profiling of electron trap states in silicon-on-insulator layers and local mechanical stress near the silicon-on-insulator/buried oxide interface in separation-by-implanted-oxygen wafers  

NASA Astrophysics Data System (ADS)

In-depth profiling of electron trap states in silicon-on-insulator (SOI) layers of separation-by-implanted-oxygen (SIMOX) wafers was carried out using the drain current-gate voltage characteristics of metal-oxide-semiconductor field-effect transistors (MOSFETs) with different SOI thicknesses, and the density of electron trap states in a gate oxide (GOX) layer thermally grown on them was measured using the gate tunneling current-gate voltage characteristics of MOSFETs. It was found that in-depth profiles of electron trap states in SOI layers have a broad peak at around 25 nm from the SOI/buried oxide (BOX) interface, and that the density of electron trap states in a GOX layer grown on the 25-nm-thick SOI layer reaches a maximum there. A morphology study using Auger electron spectroscopy and Raman spectroscopic study revealed a correlation among the density of trap states in an SOI layer, roughness, and local mechanical stress near the SOI/BOX interface. This correlation is understood to imply that local mechanical stress near the SOI/BOX interface, which is induced by roughness at the interface peculiar to the SIMOX process, enhances the generation of structural defects and resultant electron trap states in the SOI layer of a SIMOX wafer.

Nakajima, Yoshikata; Toda, Takahiro; Hanajiri, Tatsuro; Toyabe, Toru; Sugano, Takuo

2010-12-01

124

Effects of permeability on CO2 trapping mechanisms and buoyancy-driven CO2 migration in saline formations  

Microsoft Academic Search

We present the results from a series of numerical simulations to explore systematic k heterogeneity effects on both CO2 trapping mechanisms and buoyancy-driven CO2 migration. For this purpose, we generated various permutations of two-dimensional numerical models of subsurface porous media: homogeneous, random, homogenous with a low-permeability (k) lens, and isotropically\\/anisotropically correlated k fields. For heterogeneous cases, we used a sequential

Weon Shik Han; Si-Yong Lee; Chuan Lu; Brian J. McPherson

2010-01-01

125

From organic single crystals to solution processed thin-films: Charge transport and trapping with varying degree of order  

NASA Astrophysics Data System (ADS)

We have fabricated single crystal, thermally evaporated, and spin-coated thin-film transistors (TFTs) from the same organic semiconductor N,N'-1H,1H-perfluorobutyl dicyanoperylene carboxydiimide (PDIF-CN2) using various combinations of deposition methods and gate dielectrics to investigate how the charge transport properties vary with the degree of crystalline order. Never before has a semiconductor been studied in such a wide variety of processing methods, allowing cross-comparison of the microscopic factors influencing the charge transport, and in particular the trap density of states (DOS). Excellent transistor performance was achieved for PDIF-CN2 single crystals in combination with Cytop as a dielectric layer resulting in a mobility of up to 6 cm2/Vs, an on/off-ratio exceeding 108, and a subthreshold swing of 0.45 V/dec. Furthermore, gate-bias-stress effects are not present in these transistors and we observed low stress effects in the evaporated TFTs with Cytop as the gate dielectric. These findings are reflected in the trap DOS. The single crystal field-effect transistor with Cytop has a low trap DOS, whereas in evaporated TFTs, the trap DOS is higher by 2-3 orders of magnitude. Surprisingly, the trap DOS of the spin-coated TFT is similar to that in evaporated TFTs, except for additional discrete trap states centered around 0.24 eV below the conduction band.

Willa, K.; Häusermann, R.; Mathis, T.; Facchetti, A.; Chen, Z.; Batlogg, B.

2013-04-01

126

Large-scale photonic neural networks with biology-like processing elements: the role of electron-trapping materials  

NASA Astrophysics Data System (ADS)

Neural networks employing pulsating biology-oriented integrate-and-fire (IF) model neurons, that can exhibit synchronicity (phase-locking), bifurcation, and chaos, have features that make them potentially useful for learning and recognition of spatio-temporal patterns, generation of complex motor control, emulating higher-level cortical functions like feature binding, separation of object from background, cognition and other higher-level functions; all of which are beyond the ready reach of nonpulsating sigmoidal neuron networks. The spiking nature of biology-oriented neural networks makes their study in digital hardware impractical. Prange and Klar convincingly argued that the best way of realizing such networks is through analog CMOS technology rather than digital hardware. They showed, however, that the number of neurons one can accommodate on a VLSI chip limited to a hundred or so, even when submicron CMOS technology is used, because of the relatively large size of the neuron/dendrite cell. One way of reducing the size of neuron/dendrite cell is to reduce the structural complexity of the cell by realizing some of the processes needed in the cell's operation externally to the chip and by coupling these processes to the cell optically. Two such processes are the relaxation mechanism of the IF neuron and dendritic-tree processing. We have shown, by examining the blue light impulse response of electron trapping materials (ETMs) used under simultaneous infrared and blue light bias, that these materials offer features that can be used in realizing both the optical relaxation and synapto-dendritic response mechanisms. Experimental results demonstrating the potential of this approach in realizing dense arrays of biology-oriented neuron/dendrite cells will be presented, focusing on the concept and design of ETM-based image intensifier as new enabling technology.

Farhat, Nabil H.; Wen, Zhimin

1995-08-01

127

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

128

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

129

MONITORING GEOTHERMAL PROCESSES WITH MICROEARTHQUAKE MECHANISMS  

Microsoft Academic Search

The full (moment-tensor) mechanisms of microearthquakes at geothermal areas are valuable for diagnosing processes such as shear faulting and tensile cracking, whether these processes occur naturally, as a by-product of energy extraction, or result from attempts to enhance permeability and geothermal production. Linear-programming provides a robust method for inverting seismic-wave polarity and amplitude-ratio data to determine moment tensors of geothermal

Bruce R. Julian; Gillian R. Foulger

130

Density estimation of Bemisia tabaci (Hemiptera: Aleyrodidae) in a greenhouse using sticky traps in conjunction with an image processing system  

Microsoft Academic Search

Accurate forecasting of pest density is essential for effective pest management. In this study, a simple image processing system that automatically estimated the density of whiteflies on sticky traps was developed. The estimated densities of samples in a laboratory and a greenhouse were in accordance with the actual values. The detection system was especially efficient when the whitefly densities were

Mu Qiao; Jaehong Lim; Chang Woo Ji; Bu-Keun Chung; Hwang-Yong Kim; Ki-Baik Uhm; Cheol Soo Myung; Jongman Cho; Tae-Soo Chon

2008-01-01

131

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

132

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

133

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

134

Structural Analysis and Stochastic Modelling Suggest a Mechanism for Calmodulin Trapping by CaMKII  

PubMed Central

Activation of CaMKII by calmodulin and the subsequent maintenance of constitutive activity through autophosphorylation at threonine residue 286 (Thr286) are thought to play a major role in synaptic plasticity. One of the effects of autophosphorylation at Thr286 is to increase the apparent affinity of CaMKII for calmodulin, a phenomenon known as “calmodulin trapping”. It has previously been suggested that two binding sites for calmodulin exist on CaMKII, with high and low affinities, respectively. We built structural models of calmodulin bound to both of these sites. Molecular dynamics simulation showed that while binding of calmodulin to the supposed low-affinity binding site on CaMKII is compatible with closing (and hence, inactivation) of the kinase, and could even favour it, binding to the high-affinity site is not. Stochastic simulations of a biochemical model showed that the existence of two such binding sites, one of them accessible only in the active, open conformation, would be sufficient to explain calmodulin trapping by CaMKII. We can explain the effect of CaMKII autophosphorylation at Thr286 on calmodulin trapping: It stabilises the active state and therefore makes the high-affinity binding site accessible. Crucially, a model with only one binding site where calmodulin binding and CaMKII inactivation are strictly mutually exclusive cannot reproduce calmodulin trapping. One of the predictions of our study is that calmodulin binding in itself is not sufficient for CaMKII activation, although high-affinity binding of calmodulin is.

Stefan, Melanie I.; Marshall, David P.; Le Novere, Nicolas

2012-01-01

135

Imaging trapped ions with a microfabricated lens for quantum information processing  

Microsoft Academic Search

Trapped ions are a leading system for realizing quantum information\\u000aprocessing (QIP). Most of the technologies required for implementing\\u000alarge-scale trapped-ion QIP have been demonstrated, with one key exception: a\\u000amassively parallel ion-photon interconnect. Arrays of microfabricated phase\\u000aFresnel lenses (PFL) are a promising interconnect solution that is readily\\u000aintegrated with ion trap arrays for large-scale QIP. Here we show

Erik W. Streed; Benjamin G. Norton; Andreas Jechow; Till J. Weinhold; David Kielpinski

2010-01-01

136

Unconventional Processive Mechanics of Non-muscle Myosin IIB*  

PubMed Central

Proper tension maintenance in the cytoskeleton is essential for regulated cell polarity, cell motility, and division. Non-muscle myosin IIB (NMIIB) generates tension along actin filaments in many cell types, including neuronal, cardiac, and smooth muscle cells. Using a three-bead optical trapping assay, we recorded NMIIB interactions with actin filaments to determine if a NMIIB dimer cycles along an actin filament in a processive manner. Our results show that NMIIB is the first myosin II to exhibit evidence of processive stepping behavior. Analysis of these data reveals a forward displacement of 5.4 nm and, surprisingly, frequent backward steps of ?5.9 nm. Processive stepping along the long pitch helix of actin may provide a mechanism for disassembly of fascin-actin bundles. Forward steps and detachment are weakly force-dependent at all forces, consistent with rate-limiting and force-dependent ADP release. However, backward steps are nearly force-independent. Our data support a model in which NMIIB can readily move in both directions at stall, which may be important for a general regulator of cytoskeleton tension.

Norstrom, Melanie F.; Smithback, Philip A.; Rock, Ronald S.

2010-01-01

137

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

138

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

SciTech Connect

Al/HfO{sub 2}/SiN{sub x}: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 10{sup 11} cm{sup -2} eV{sup -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 HfO{sub 2}/SiN{sub x}:H intralayer interface. These traps are more easily charged or discharged as this interface comes near to the substrate, that is, as thinner the SiN{sub x}: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 HfO{sub 2}/SiN{sub x}:H intralayer interface.

Garcia, H.; Duenas, S.; Castan, H.; Gomez, A.; Bailon, L. [Departamento de Electricidad y Electronica, E.T.S.I. Telecomunicacion, Universidad de Valladolid, Campus 'Miguel Delibes', 47011 Valladolid (Spain); Toledano-Luque, M.; Prado, A. del; Martil, I.; Gonzalez-Diaz, G. [Departamento de Fisica Aplicada III (Electricidad y Electronica), Facultad de Ciencias Fisicas, Universidad Complutense, 28040 Madrid (Spain)

2008-11-01

139

Trapped field in individual and stacked rings of bulk melt processed Y-Ba-Cu-O  

Microsoft Academic Search

Single grain rare earth barium cuprate [(RE)BCO] high temperature superconductors can trap large magnetic fields. In principle, samples can be stacked to form a quasipermanent magnet with a high length to width aspect ratio for engineering applications. The flux trapping properties of a stack of ring-shaped samples of Y-Ba-Cu-O (YBCO) were measured both on the surface and through the bore.

T. D. Withnell; N. H. Babu; M. Majoros; E. S. Reddy; D. M. Astill; Y. Shi; D. A. Cardwell; A. M. Campbell; N. Kerley; S. Zhang

2005-01-01

140

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

141

Mechanism on brain information processing: Energy coding  

NASA Astrophysics Data System (ADS)

According to the experimental result of signal transmission and neuronal energetic demands being tightly coupled to information coding in the cerebral cortex, the authors present a brand new scientific theory that offers a unique mechanism for brain information processing. They demonstrate that the neural coding produced by the activity of the brain is well described by the theory of energy coding. Due to the energy coding model's ability to reveal mechanisms of brain information processing based upon known biophysical properties, they cannot only reproduce various experimental results of neuroelectrophysiology but also quantitatively explain the recent experimental results from neuroscientists at Yale University by means of the principle of energy coding. Due to the theory of energy coding to bridge the gap between functional connections within a biological neural network and energetic consumption, they estimate that the theory has very important consequences for quantitative research of cognitive function.

Wang, Rubin; Zhang, Zhikang; Jiao, Xianfa

2006-09-01

142

Steam trap  

SciTech Connect

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 input port including an extension extending into the chamber and having an end surface forming a seating surface within the chamber; and closure means for automatically opening and closing the steam trap. The closure means are disposed within the chamber in substantially sealing engagement with the chamber sidewalls.

Kline, L.B.

1987-05-12

143

Process mechanisms in coking a distillate feedstock  

Microsoft Academic Search

1.The coking mechanism for distillate feedstocks has been studied in the example of an extract from a coker gas oil.2.In contrast to the coking of residual stocks, the coking of a distillated feedstock that is essentially asphaltene-free, within the limits of the process conditions investigated, brings about a continuous accumulation of asphaltenes in the residue.3.Another difference observed with distillate feedstock

G. D. Golubkova; E. V. Smidovich

1974-01-01

144

A Microscale Gas Trapping Investigation  

NASA Astrophysics Data System (ADS)

Immobilization and trapping of CO2 enhances its geological storage security. The trapping mechanism has been characterized into four main groups: structural, residual, dissolution and mineralization. While structural trapping acts immediately when injection starts and is well investigated, residual and dissolution trapping contribution increase over geological storage time and need to be better understood to develop more accurate models and simulator predictions. Dissolution trapping is controlled by a phase equilibrium process. The local equality of fugacities in the aqueous and the gas phase determines the amount of CO2 to be transferred. Complete dissolution of a single gas bubble can only happen after the continuous gas phase has been disconnected and immobilized by capillary trapping. This process on the other hand is governed by flow rate and pore body to throat size in the porous media. In this study, we focus on an experimental pore-scale investigation of residual and capillary trapping. Our work is a precursor to designing storage processes with enhancing storage security. In the present work, CO2-water imbibition experiments were conducted in visual micromodels whose pore space is geometrically and topologically similar to Berea sandstone. High -resolution, micro-visual data, in the form of photographs and video footage, describes the trapping mechanism and especially the disconnection and shrinkage of the CO2 phase in various phase conditions (gas-liquid-supercritical). During final bubble dissolution, special emphasis was placed on the homogeneous and heterogonous dissolution cases and their impact on storage security. Results show that the depending on the flow rate of the imbibing water different trapping mechanism are observed. Lower rates comparable to the trailing edge of the CO2 plume led to a greater frequency of snap off events and greater trapped residual saturation whereas higher rates comparable to the near wellbore area during enhanced sequestration (CO2-water alternating injection) showed displacement of gas bubbles and greater dissolution rates that ultimately leads to very low or zero gas saturation. Furthermore complete dissolution events showed that homogenous as well as heterogeneous dissolution occurs, whereas the latter could be subdivided into microbubble formation and dissolution on crevices or pore roughness. Based on the observations we can conclude that the type of rock and its roughness as well as the fines present in the brine are important factors determining the dissolution mechanism.

Buchgraber, M.; Kovscek, A. R.

2011-12-01

145

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

146

Fluid Assisted Fault Weakening: Mechanical vs. Chemical Processes  

NASA Astrophysics Data System (ADS)

The influx of fluids into fault zones can trigger two main types of weakening process that operate over different timescales, facilitate fault movement and influence fault slip behaviour. During the seismic cycle fluids can be trapped by low permeability fault zones or stratigraphic barriers favoring fluid overpressure (mechanical weakening) and earthquake nucleation. In the entire fault history fluids can react with fault rocks to produce weak mineral phases (chemical weakening) that alter the mechanical properties of the fault zones. Here I will present two examples of mechanical and chemical fault-weakening from the Apennines of Italy. Seismic profiles and deep borehole data show that the strongest earthquakes of the Apennines nucleate within overpressured Evaporites consisting of dolostones and anhydrites. Field and experimental studies on exhumed faults within the same lithology depict a cataclastic inner fault that can generate frictional instabilities with localization and increasing sliding velocity. The outer fault core presents barrier-like portions associated with foliated anhydrites, 10-21 ? permeability ?10-19 m2. The combination of field observations and rock deformation measurements suggests a fault zone structure capable of developing fluid overpressures during the seismic cycle: fluid overpressures can potentially promote earthquake nucleation and aftershock triggering. Field studies from an exhumed regional low-angle normal fault show that in the long term fluids reacted (diffusion-mass transfer processes) with fine-grained cataclasites in the fault core to produce a phyllosilicates-rich and foliated fault rock. Within the foliated microstructure, that is rich in talc, smectite and chlorite, deformation occurs by frictional sliding along 50-200-nm-thick lamellae. Rock deformation experiments show that the foliated fault rock is weak, 0.2 < friction< 0.35, it is characterized by a stable sliding slip-behaviour with no strength recovery with time. Chemical weakening associated with phyllosilicate development along fault zones represents a valuable explanation for long term weak and creeping faults. The activation of mechanical or chemical weakening processes is primarily controlled by pressure, temperature, strain-rate, protolith composition and type of fluids. The interplay between mechanical and chemical weakening favors the development of heterogeneous crustal scale faults that can contribute to explain the complex fault slip behaviour recently documented by high-resolution GPS and seismological data.

Collettini, C.

2011-12-01

147

Temperature dependence of the trapped field and mechanical properties of neutron irradiated and reinforced YBa2Cu3O7-? bulk superconductors  

Microsoft Academic Search

We report on the temperature dependence of the trapped field in neutron irradiated YBa2Cu3O7-? bulk melt-textured materials. The field trapping capability of these materials at low temperatures is limited by their mechanical properties. We observe that samples without reinforcement usually break during activation at temperatures of around 50 K. Two reinforcement techniques were tested. Resin impregnation is found to be

Raquel Gonzalez-Arrabal; Michael Eisterer; Harald W. Weber; Günter Fuchs; Peter Verges; Gernot Krabbes; Masaru Tomita; Masato Murakami; Doris Litzkendorf; Tobias Habisreuther; Wolfgang Gawalek

2003-01-01

148

Underlying mechanisms for commuting and migration processes  

NASA Astrophysics Data System (ADS)

Both frequent commuting and long-term migration are complex human processes that strongly depend on socio-demographic, spatial, political, and even economic factors. We can describe both processes using weighted networks, in which nodes represent geographic locations and link weights denote the flux of individuals who commute (or migrate) between locations. Although both processes concern the movements of individuals, they are very different: commuting takes place on a daily (or weekly) basis and always between the same two locations, while migration is a rare, one-way displacement. Despite these differences, a recently proposed stochastic model, the Radiation model, provides evidence that both processes may be successfully described by the same underlying mechanism. For example, quantities of interest for either process, such as the distributions of trip length and destination populations, appear remarkably similar to the model's predictions. We explore the similarities and differences between commuting and migration both empirically, using census data for the United States, and theoretically, by comparing these commuting and migration networks to the predictions given by the Radiation model.

Simini, Filippo; Barabasi, Albert-Laszlo; Bagrow, James

2012-02-01

149

On the role of hole trapping centers in the interactive mechanism of the trap interaction in anion-defect alumina single crystals  

NASA Astrophysics Data System (ADS)

The effect of deep hole traps on the intensity and shape of the dosimetric peak of thermoluminescence (TL) has been studied at 450 K in anion-defect alumina single crystals. It has been shown that filling of deep hole centers leads to a decrease in the sensitivity to radiation of crystals with a small half-width of the TL peak and has no effect on the sensitivity of crystals with a broadened peak. It has been assumed that traps responsible for the TL dosimetric peak broadening are of hole nature, which can be caused by the presence of Ti3+ ions in the corundum lattice. The results obtained have been interpreted within the modified model of the interactive system of traps.

Nikiforov, S. V.; Kortov, V. S.; Nosal, A. A.; Moiseikin, E. V.

2011-10-01

150

Trap states and space charge limited current in dispersion processed zinc oxide thin films  

NASA Astrophysics Data System (ADS)

The electric transport properties of nanoparticulate zinc oxide (ZnO) thin films are investigated in nitrogen and ambient atmosphere with respect to the effects of polymer adsorbates, in order to study the origin of hysteresis behavior of ZnO thin film transistors. A strong dependence on the polymer adsorbate of the conductivity in nitrogen atmosphere is observed. Utilizing the space charge limited current theory, the trap depth and concentration in the films have been estimated. According to this analysis, the low conductivity of polymer free thin films in ambient atmosphere is caused by an increase in deep traps, compensating free charge carriers and not by a reduction in donorlike defect states. Furthermore, polymeric additives seem to induce similar trap states, which make the transport properties less sensitive against atmospheric influences. However, the strongly compensated semiconductor created in this way, causes a slow trap and release behavior resulting in a strong hysteresis in the transistor characteristics and long-term instabilities. It is shown, that ignoring these time-dependent characteristics, straight forward derived transistor parameters like the field effect mobility can be easily overestimated.

Bubel, S.; Mechau, N.; Hahn, H.; Schmechel, R.

2010-12-01

151

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

1996-04-01

152

Aqueous Electrochemical Mechanisms in Actinide Residue Processing  

SciTech Connect

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 Energy's (DOE) legacy waste from fifty years of nuclear weapons production activities. Much of this material is presently in storage at sites throughout the DOE weapons production complex (most notably Rocky Flats, Savannah River and Hanford) awaiting further processing and/or final disposition. The chemical and physical stability of much of this material has been called into question recently by the Defense Nuclear Facility Safety Board (DNFSB) and resulted in the issuance of a mandate by the DNFSB to undertake a program to stabilize these materials [1]. The ultimate disposition for much of these materials is anticipated to be geologic repositories such as the proposed Waste Isolation Pilot Plant in New Mexico. However, in light of the mandate to stabilize existing residues and the probable concomitant increase in the volume of material to be disposed as a result of stabilization (e.g., from repackaging at lower residue densities), the projected storage volume for these wastes within anticipated geologic repositories will likely be exceeded simply to handle existing wastes. Additional processing of some of these residue waste streams to reduce radionuclide activity levels, matrix volume, or both is a potentially important strategy to achieve both stabilization and volume reduction so that the anticipated geologic repositories will provide adequate storage volume. In general, the plutonium and uranium that remains in solid residue materials exists in a very stable chemical form (e.g., as binary oxides), and the options available to remove the actinides are limited. However, there have been some demonstrated successes in this vain using aqueous phase electrochemical methods such as the Catalyzed Electrochemical Plutonium Oxide Dissolution (CEPOD) process pioneered by workers at Pacific Northwest National Laboratory in the mid-1970s [2]. The basis for most of these mediated electrochemical oxidation/reduction (MEO/R) processes is the generation of a dissolved electrochemical catalyst, such as Ag2+, which is capable of oxidizing or reducing solid-phase actinide species or actinide sorbates via 7 heterogeneous electron transfer to oxidation states that have significantly greater solubilities (e.g., PuO2(s) to PuO2 2+ (dissolved)). The solubilized actinide can then be recovered by ion exchange or other mechanisms. These aqueous electrochemical methods for residue treatment have been considered in many of the ''trade studies'' to evaluate options for stabilization of the various categories of residue materials. While some concerns generally arise (e.g., large secondary waste volumes could results since the process stream normally goes th rough anion exchange or precipitation steps to remove the actinide), the real utility and versatility of these methods should not be overlooked. They are low temperature, ambient pressure processes that operate in a non-corrosive environment. In principle, they can be designed to be highly selective for the actinides (i.e., no substrate degradation occurs), they can be utilized for many categories of residue materials with little or no modification in hardware or operating conditions, and they can conceivably be engineered to minimize secondary waste stream volume. However, some fundamental questions remain concerning the mechanisms through which these processes act, and how the processes might be optimized to maximize efficiency while minimizing secondary waste. In addition, given the success achieved to date on the limited set of residues, further research is merited to extend the range of applicability of these electrochemical methods to other residue and waste streams. The principal goal of the work described here is to develop a fundamental understanding of the heterogeneous electron transfer thermodynamics a

Morris, David E.; Burns, Carol J.; Smith, Wayne H.; Blanchard

2000-12-31

153

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

154

Brain mechanisms for processing affective touch.  

PubMed

Despite the crucial role of touch in social development, there is very little functional magnetic resonance imaging (fMRI) research on brain mechanisms underlying social touch processing. The "skin as a social organ" hypothesis is supported by the discovery of C-tactile (CT) nerves that are present in hairy skin and project to the insular cortex. CT-fibers respond specifically well to slow, gentle touch such as that which occurs during close social interactions. Given the social significance of such touch researchers have proposed that the CT-system represents an evolutionarily conserved mechanism important for normative social development. However, it is currently unknown whether brain regions other than the insula are involved in processing CT-targeted touch. In the current fMRI study, we sought to characterize the brain regions involved in the perception of CT-supported affective touch. Twenty-two healthy adults received manual brush strokes to either the arm or palm. A direct contrast of the blood-oxygenation-level-dependent (BOLD) response to gentle brushing of the arm and palm revealed the involvement of a network of brain regions, in addition to the posterior insula, during CT-targeted affective touch to the arm. This network included areas known to be involved in social perception and social cognition, including the right posterior superior temporal sulcus and the medial prefrontal cortex (mPFC)/dorso anterior cingulate cortex (dACC). Connectivity analyses with an mPFC/dACC seed revealed coactivation with the left insula and amygdala during arm touch. These findings characterize a network of brain regions beyond the insula involved in coding CT-targeted affective touch. PMID:22125232

Gordon, Ilanit; Voos, Avery C; Bennett, Randi H; Bolling, Danielle Z; Pelphrey, Kevin A; Kaiser, Martha D

2011-11-29

155

Effects of quantized motion of a trapped atom on non-linear optical processes  

Microsoft Academic Search

It is shown that the second order response of a single two-level atom in a harmonic trap interacting with a classical electromagnetic field is non-zero and that, in that order, the system generates a four-wave mixing signal. The resonances in that signal are analysed by assuming the atom to interact resonantly with one of the sidebands. The non-zero second order

Aditi Ray; R. R. Puri

1999-01-01

156

Molecular probes of the mechanism of cytochrome P450. Oxygen traps a substrate radical intermediate.  

PubMed

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 1ps for CYP2E1, CYP3A4 and CYP2B1, respectively, corresponding to rebound rates of 0.9×10(10)s(-1), 7.2×10(10)s(-1) and 1.0×10(12)s(-1). For the model iron porphyrin, FeTMPyP, a radical lifetime of 81ps and a rebound rate of 1.2×10(10)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 [Fe(IV)-OH ()R] can compete with cage collapse to form a C-O 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. PMID:21075070

Cooper, Harriet L R; Groves, John T

2010-11-12

157

Solution-processed zinc-tin oxide thin-film transistors with low interfacial trap density and improved performance  

NASA Astrophysics Data System (ADS)

Solution-processed amorphous oxide semiconductors are attractive channel materials in thin-film transistors (TFTs) for low-cost electronics. We demonstrate improved performance and uniformity of solution-processed zinc-tin oxide (ZTO) TFTs by optimizing the prebake process for the ZTO precursor film. ZTO prebake process prearranges the dielectric/semiconductor interface and minimizes the performance variation caused by the uneven thermal distribution during annealing process. Prearranging the interface also reduces interfacial trap density and results in improved performance. A mobility of 27.3 cm2/V s, an on/off ratio of ~107, and a subthreshold swing of 122 mV/decade have been obtained. Significant improvement in operational stability has also been observed.

Lee, Chen-Guan; Dodabalapur, Ananth

2010-06-01

158

Entangled states of trapped atomic ions  

Microsoft Academic Search

To process information using quantum-mechanical principles, the states of individual particles need to be entangled and manipulated. One way to do this is to use trapped, laser-cooled atomic ions. Attaining a general-purpose quantum computer is, however, a distant goal, but recent experiments show that just a few entangled trapped ions can be used to improve the precision of measurements. If

Rainer Blatt; David Wineland

2008-01-01

159

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

160

Processing and mechanical characterization of alumina laminates  

NASA Astrophysics Data System (ADS)

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 consists of a lightweight, low-density bulk material with a thin, hard, wear resistant exterior layer. Alumina laminates with strong interfaces have been successfully produced in this work using two different direct-casting processes. Gelcasting is a useful near-net shape processing technique that has been combined with several techniques, such as reaction bonding of aluminum oxide and the use of starch as a fugative filler, to successfully produced stepped-density alumina laminates. The other direct casting process that has been developed in this work is thermoreversible gelcasting (TRG). This is a reversible gelation process that has been used to produce near-net shape dense ceramic bodies. Also, individual layers can be stacked together and heated to produce laminates. Bilayer laminate samples were produced with varied thickness of porous and dense layers. It was shown that due to the difference in modulus and hardness, transverse cracking is found upon Hertzian contact when the dense layer is on the exterior. In the opposite arrangement, compacted damage zones formed in the porous material and no damage occurred in the underlying dense layer. Flaw tolerant behavior of the porous exterior/dense underlayer was examined by measuring biaxial strength as a function of Vickers indentation load. It was found that the thinnest layer of porous material results in the greatest flaw tolerance. Also, higher strength was exhibited at large indentation loads when compared to dense monoliths. The calculated stresses on the surfaces and interface afforded an explanation of the behavior that failure initiates at the interface between the layers for the thinnest configuration, rather than the sample surface.

Montgomery, John K.

2002-08-01

161

Planar defects as Ar traps in trioctahedral micas: A mechanism for increased Ar retentivity in phlogopite  

NASA Astrophysics Data System (ADS)

The effects of planar defects and composition on Ar mobility in trioctahedral micas have been investigated in samples from a small marble outcrop (˜500 m2) in the Frontenac Terrane, Grenville Province, Ontario. These micas crystallized during amphibolite-facies metamorphism at ˜1170 Ma and experienced a thermal pulse ˜100 Ma later at shallow crustal levels associated with the emplacement of plutons. 87Rb/86Sr ages of the phlogopites range from ˜950 to ˜1050 Ma, consistent with resetting during the later thermal event. The same phlogopites however, give 40Ar/39Ar ages between ˜950 and 1160 Ma, spanning the age range of the two thermal events. This result is intriguing because these micas have undergone the same thermal history and were not deformed after peak metamorphic conditions. In order to understand this phenomenon, the chemical, crystallographical, and microstructural nature of four mica samples has been characterized in detail using a wide range of analytical techniques. The scanning electron microscope (SEM), electron microprobe (EMP), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data show that the micas are chemically homogeneous (with the exception of Ba) and similar in composition. The Fourier transform infrared spectroscopy and Mossbauer results show that the M sites for three of the micas are dominated by divalent cations and the Fe3+/(Fe2++Fe3+) ratio for all four phlogopites ranges from 0.10 to 0.25. The stable-isotopic data for calcite indicate that this outcrop was not affected by hydrothermal fluids after peak metamorphism. No correlation between chemical composition and 87Rb/86Sr and 40Ar/39Ar age or between crystal size and 40Ar/39Ar age is observed. The only major difference among all of the micas was revealed through transmitted electron microscope (TEM), which shows that the older 1M micas contain significantly more layer stacking defects, associated with crystallization, than the younger micas. We propose that these defect structures, which are enclosed entirely within the mineral grain may serve as Ar traps and effectively increase the Ar retentivity of the mineral. As this phenomenon has not been previously documented in micas, this may have significant implications for the interpretation of 40Ar/39Ar ages of minerals which have similar defect structures.

Camacho, A.; Lee, J. K. W.; Fitz Gerald, J. D.; Zhao, J.; Abdu, Y. A.; Jenkins, D. M.; Hawthorne, F. C.; Kyser, T. K.; Creaser, R. A.; Armstrong, R.; Heaman, L. W.

2012-08-01

162

Simulation of external ion injection, cooling and extraction processes with SIMION 6.0 for the ion trap/reflectron time-of-flight mass spectrometer.  

PubMed

In this work we have developed a PC-based simulation to study ion injection, cooling and extraction processes for multiple ions in an trap/reflectron time-of-flight (IT/reTOF) system. This simulation is based upon SIMION 6.0 with user written programs in which a 3D collision model is used to describe ion--buffer gas molecule interactions. The results of various simulations describing the relation between the trapping efficiency for external injection of ions into the trap and the RF phase, and the effects of initial kinetic energy and ramp-up rate on dynamic trapping of externally produced ions are discussed. Further, single-pulsing and bipolar-pulsing schemes for ejecting ions from the trap are examined. The simulations show that bipolar pulsing can markedly improve the resolution. In the bipolar ejection mode the relation between resolution and the extraction voltages and RF ramp-off rate are studied. PMID:9299763

He, L; Lubman, D M

1997-01-01

163

Theory of magic optical traps for Zeeman-insensitive clock transitions in alkali-metal atoms  

SciTech Connect

Precision measurements and quantum-information processing with cold atoms may benefit from trapping atoms with specially engineered, 'magic' optical fields. At the magic trapping conditions, the relevant atomic properties remain immune to strong perturbations by the trapping fields. Here we develop a theoretical analysis of magic trapping for especially valuable Zeeman-insensitive clock transitions in alkali-metal atoms. The involved mechanism relies on applying a magic bias B field along a circularly polarized trapping laser field. We map out these B fields as a function of trapping laser wavelength for all commonly used alkalis. We also highlight a common error in evaluating Stark shifts of hyperfine manifolds.

Derevianko, Andrei [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States)

2010-05-15

164

Controlling the efficiency of trapping in treelike fractals  

NASA Astrophysics Data System (ADS)

Efficiently controlling the trapping process, especially the trapping efficiency, is central in the study of trap problem in complex systems, since it is a fundamental mechanism for diverse other dynamic processes. Thus, it is of theoretical and practical significance to study the control technique for trapping problem. In this paper, we study the trapping problem in a family of proposed directed fractals with a deep trap at a central node. The directed fractals are a generalization of previous undirected fractals by introducing the directed edge weights dominated by a parameter. We characterize all the eigenvalues and their degeneracies for an associated matrix governing the trapping process. The eigenvalues are provided through an exact recursive relation deduced from the self-similar structure of the fractals. We also obtain the expressions for the smallest eigenvalue and the mean first-passage time (MFPT) as a measure of trapping efficiency, which is the expected time for the walker to first visit the trap. The MFPT is evaluated according to the proved fact that it is approximately equal to reciprocal of the smallest eigenvalue. We show that the MFPT is controlled by the weight parameter by modifying which the MFPT can scale superlinealy, linearly, or sublinearly with the system size. Thus, this work paves a way to delicately controlling the trapping process in the fractals.

Wu, Bin; Zhang, Zhongzhi

2013-07-01

165

Capacitive MEMS-based sensors : thermo-mechanical stability and charge trapping  

Microsoft Academic Search

Micro-Electro Mechanical Systems (MEMS) are generally characterized as miniaturized systems with electrostatically driven moving parts. In many cases, the electrodes are capacitively coupled. This basic scheme allows for a plethora of specifications and functionality. This technology has presently matured and is widely employed in industry. \\u000aA voltage across the electrodes will attract the movable part. This relation between electric field

Essen van Martin Cornelis

2009-01-01

166

Vinyl Polymerization by Metal Complexes. XXIX. Initiation Mechanism of Vinyl Polymerization Initiated by Copper(ll) Chelates of Polyvinylamine—Carbon Tetrachloride System: Spin Trapping and Gelation Studies  

Microsoft Academic Search

The initiation mechanism of vinyl polymerization initiated by copper(II) chelates of polyvinylamine and 1, 3-diaminopropane was studied both in aqueous and dimethyl sulfoxide solution, in the presence of carbon tetrachloride. The results of spin trapping and gelation experiments made clear that trichloro-methyl free radical initiates the polymerization.

Kelichi Kimura; Yoshiakiinaki; Kiichi Takemoto

1976-01-01

167

Mass Measurements of Heavy ^252Cf Fission Fragments Near the r-Process Path with the Canadian Penning Trap  

NASA Astrophysics Data System (ADS)

Precision mass measurements of nuclides near the astrophysical r-process path are vital to reduce the uncertainties in the relevant neutron separation energies and the consequent abundance predictions. Before moving to CARIBU, the Canadian Penning Trap mass spectrometer at Argonne National Laboratory undertook a series of mass measurements of spontaneous fission products from a 150 ?Ci ^252Cf source in a previous large-volume gas catcher. Masses of 38 neutron-rich nuclides ranging from Z=51 to 64 were measured, many of which were closer to the r-process path than had previously been measured for these elements. Systematic deviations from the AME 2003 are seen over a wide range of elements, and possible effects of these deviations on the r process will be discussed. These measurements are being extended to even higher neutron excess at CARIBU. )

van Schelt, J.; Lascar, D.; Savard, G.; Clark, J. A.; Greene, J. P.; Levand, A. F.; Sun, T.; Zabransky, B. J.; Caldwell, S.; Sternberg, M.; Fallis, J.; Sharma, K. S.; Segel, R. E.; Li, G.

2010-02-01

168

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

169

Float-thermostatic trap prevents steam loss  

SciTech Connect

This article focuses on the energy efficiency of a float-thermostatic steam trap which prevents steam loss. This float-thermostatic steam trap was awarded Top Honors in the steam traps category in the 1982 Chemical Processing Vaaler competition because of the trap's lack of steam loss, its in-line installation, and its ability to be maintained in-line. The energy efficient trap features a float operated mechanism that modulates with the load and always maintains a condensate level above the main valve to prevent steam leakage, and a balance pressure thermostatic air vent that immediately and continuously discharges all non-condensibles. Other features include resistance to dirt plugging and freeze damage for long reliable service; fail-safe operation; all-stainless steel corrosion resistant internals; light weight stainless steel case with forged cover; and convenient top and bottom inlet with 1/2'' threaded or socket weld connections. The traps will save from 2 to 5 lb/hr of steam, compared to conventional traps. Annual savings are estimated at between $175 and $438 per trap, with steam costing $10 per thousand pounds.

Not Available

1982-11-01

170

Theoretical study of molecular mechanism of binding TRAP220 coactivator to Retinoid X Receptor alpha, activated by 9-cis retinoic acid  

PubMed Central

Study on molecular mechanism of conformational reorientation of RXR-alpha ligand binding domain is presented. We employed CABS - a reduced model of protein dynamics to model folding pathways of binding 9-cis retinoic acid to apo-RXR molecule and TRAP220 peptide fragment to the holo form. Based on obtained results we also propose a sequential model of RXR activation by 9-cis retinoic acid and TRAP220 coactivator. Methodology presented here may be used for investigation of binding pathways of other NR/hormone/cofactor sets.

Kurcinski, Mateusz; Kolinski, Andrzej

2010-01-01

171

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

PubMed

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)?cm(3) [middle dot] 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. PMID:24050320

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

2013-09-14

172

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

173

Processive phosphorylation: mechanism and biological importance  

PubMed Central

Recent proteomic data indicate that a majority of the phosphorylated proteins in a eucaryotic cell contain multiple sites of phosphorylation. In many signaling events, a single kinase phosphorylates multiple sites on a target protein. Processive phosphorylation occurs when a protein kinase binds once to a substrate and phosphorylates all of the available sites before dissociating. In this review, we discuss examples of processive phosphorylation by serine/threonine kinases and tyrosine kinases. We describe current experimental approaches for distinguishing processive from non-processive phosphorylation. Finally, we contrast the biological situations that are suited to regulation by processive and non-processive phosphorylation.

Patwardhan, Parag; Miller, W. Todd

2007-01-01

174

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

175

Heating rate and electrode charging measurements in a scalable, microfabricated, surface-electrode ion trap  

NASA Astrophysics Data System (ADS)

We characterise the performance of a surface-electrode ion "chip" trap fabricated using established semiconductor integrated circuit and micro-electro-mechanical-system (MEMS) microfabrication processes, which are in principle scalable to much larger ion trap arrays, as proposed for implementing ion trap quantum information processing. We measure rf ion micromotion parallel and perpendicular to the plane of the trap electrodes, and find that on-package capacitors reduce this to ?10 nm in amplitude. We also measure ion trapping lifetime, charging effects due to laser light incident on the trap electrodes, and the heating rate for a single trapped ion. The performance of this trap is found to be comparable with others of the same size scale.

Allcock, D. T. C.; Harty, T. P.; Janacek, H. A.; Linke, N. M.; Ballance, C. J.; Steane, A. M.; Lucas, D. M.; Jarecki, R. L.; Habermehl, S. D.; Blain, M. G.; Stick, D.; Moehring, D. L.

2012-06-01

176

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.

Gardner, David R. (Albuquerque, NM); Hendrickson, Bruce A. (Albuquerque, NM); Plimpton, Steven J. (Albuquerque, NM); Attaway, Stephen W. (Cedar Crest, NM); Heinstein, Martin W. (Albuquerque, NM); Vaughan, Courtenay T. (Albuquerque, NM)

1998-01-01

177

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

178

Ultra-fast underwater suction traps.  

PubMed

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. PMID:21325323

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

2011-02-16

179

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

180

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

181

Changes in mechanical properties throughout osmotic processes  

Microsoft Academic Search

In osmotic dehydration of fruits, physical and chemical changes occurring throughout the process provoke changes in the product texture and appearance to a different degree depending on the process conditions and product characteristics. Nevertheless, water content reduction and sugar gain have been observed to have some cryoprotectant effects on colour and texture in several fruits. In this work, the specific

A Chiralt; N Mart??nez-Navarrete; J Mart??nez-Monzó; P Talens; G Moraga; A Ayala; P Fito

2001-01-01

182

Fabrication of Highly Ordered Arrays of Nanoparticles by Mechanical Process  

NASA Astrophysics Data System (ADS)

We have developed a new method of fabricating nanoparticles utilizing a mechanical rubbing process. Highly ordered arrays of Au nanoparticles with a diameter of 60 nm have been fabricated on a porous anodic alumina template. Pressure measurements during the mechanical rubbing process confirmed that these nanoparticles were formed only by a mechanical separation process. Our method can be applied to fabricate nanocapsules and has a wide range of applicability to materials that have never been controlled in the nanoscale.

Ito, Hironori; Nomura, Shintaro

2006-11-01

183

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

184

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

185

A 3 T magnetic field generator using melt-processed bulk superconductors as trapped field magnets and its applications  

NASA Astrophysics Data System (ADS)

An intense magnetic field generator yielding 3.15 T in the open space between the magnetic poles has been constructed by using a pair of melt-processed bulk superconductors as trapped field magnets. The field was measured in a 2 mm gap between the magnetic poles set face-to-face after the pulsed-field magnetization ``IMRA'' method. This field generator is composed of Sm-based 123 compounds, vacuum pumps, pulsed-field coils and GM refrigerators with compressors. The system can be used in various applications. We investigated, for instance, the application to a high gradient magnetic separation system. It was found that the alpha hematite fine particles mixed in the flowing water was completely removed by this technique which was operated in the field of 1.7 T in the gap of 20 mm.

Oka, T.; Yokoyama, K.; Itoh, Y.; Yanagi, Y.; Yoshikawa, M.; Ikuta, H.; Mizutani, U.; Okada, H.; Noto, K.

2003-10-01

186

Processing mechanics for flip-chip assemblies  

Microsoft Academic Search

In this paper, a non-linear finite element framework has been implemented to simulate the sequential build-up of a flip-chip package. A generalized deformation model with element removal and addition is used to activate and deactivate the underfill material layer to simulate flip-chip package fabrication. Using process models, one can determine the warpage stresses at any intermediate stage in the process.

J. Wang; W. Ren; D. Zou; Z. Qian; S. Liu

1999-01-01

187

Aqueous Electrochemical Mechanisms in Actinide Residue Processing  

Microsoft Academic Search

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 Energy's (DOE) legacy waste from fifty years of nuclear weapons production activities. Much of this material is presently in storage at sites

David E. Morris; Carol J. Burns; Wayne H. Smith; Blanchard

2000-01-01

188

Material removal processes: Engineering mechanics consideration  

NASA Astrophysics Data System (ADS)

In the material removal process called machining, a layer of material of constant thickness is removed from the workpiece by a wedge-shaped tool that travels parallel to the workpiece at a preselected depth. Even though the speed of relative movement between workpiece and tool is low (typical 1-10 m/s), the strain-rates in the workpiece near the tool can be high, on the order of 10(exp 4)-10(exp 5) /s. When machining brittle materials or unlubricated ductile materials at low speed, the removed metal (or chip) will be discontinuous and made up of small fractured segments. On the other hand, when machining ductile material under lubricated conditions, the removed material forms a continuous coil. In this case, we can represent the material removal process as a steady-state process. In this presentation, we will restrict ourselves to orthogonal machining where the cutting edge is perpendicular to the relative motion--a situation also approximated by other material removal processes such as planing and broaching, and turning on a lathe.

Anderson, C. A.

189

Lysosomal trapping of a radiolabeled substrate of P-glycoprotein as a mechanism for signal amplification in PET  

PubMed Central

The radiotracer [11C]N-desmethyl-loperamide (dLop) images the in vivo function of P-glycoprotein (P-gp), a transporter that blocks the entry of drugs that are substrates into brain. When P-gp is inhibited, [11C]dLop, a potent opiate agonist, enters and becomes trapped in the brain. This trapping is beneficial from an imaging perspective, because it amplifies the PET signal, essentially by accumulating radioactivity over time. As we previously demonstrated that this trapping was not caused by binding to opiate receptors, we examined whether [11C]dLop, a weak base, is ionically trapped in acidic lysosomes. To test this hypothesis, we measured [3H]dLop accumulation in human cells by using lysosomotropics. Because the in vivo trapping of dLop was seen after P-gp inhibition, we also measured [3H]dLop uptake in P-gp–expressing cells treated with the P-gp inhibitor tariquidar. All lysosomotropics decreased [3H]dLop accumulation by at least 50%. In P-gp–expressing cells, tariquidar (and another P-gp inhibitor) surprisingly decreased [3H]dLop uptake. Consequently, we measured [11C]dLop uptake before and after tariquidar preadministration in lysosome-rich organs of P-gp KO mice and humans. After tariquidar pretreatment in both species, radioactivity uptake in these organs decreased by 35% to 40%. Our results indicate that dLop is trapped in lysosomes and that tariquidar competes with dLop for lysosomal accumulation in vitro and in vivo. Although tariquidar and dLop compete for lysosomal trapping in the periphery, such competition does not occur in brain because tariquidar has negligible entry into brain. In summary, tariquidar and [11C]dLop can be used in combination to selectively measure the function of P-gp at the blood–brain barrier.

Kannan, Pavitra; Brimacombe, Kyle R.; Kreisl, William C.; Liow, Jeih-San; Zoghbi, Sami S.; Telu, Sanjay; Zhang, Yi; Pike, Victor W.; Halldin, Christer; Gottesman, Michael M.; Innis, Robert B.; Hall, Matthew D.

2011-01-01

190

Mass measurements along the rp-process path using the Canadian Penning trap mass spectrometer  

Microsoft Academic Search

The processes responsible for the creation of elements more massive than iron are not well understood. A possible scenario for their production involves the rapid capture of protons (rp-process), which is thought to occur in explosive astrophysical events such as novae and X-ray bursts. Mass measurements of the nuclides involved with uncertainties on the order of 100 keV or better

J. A. Clark; J. Vaz; J. C. Wang; C. Boudreau; R. C. Barber; K. S. Sharma; B. Blank; A. Heinz; A. F. Levand; G. Savard; D. Seweryniak; W. Trimble; Z. Zhou; F. Buchinger; J. E. Crawford; S. Gulick; J. K. P. Lee; G. D. Sprouse

2003-01-01

191

Avoiding the Proofreading Trap: The Value of the Error Correction Process.  

ERIC Educational Resources Information Center

|Describes how one writing center with many English-as-a-Second-Language (ESL) students has integrated the "cultural informant" role of tutors with their role of teaching self-editing strategies. Reviews the process of introducing ESL students to use of a learner's dictionary, minimal marking, and error logs. Offers examples of using these…

Cogie, Jane; Strain, Kim; Lorinskas, Sharon

1999-01-01

192

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

Code of Federal Regulations, 2010 CFR

...operation of mechanized claims processing and information retrieval systems. ...ADMINISTRATION Mechanized Claims Processing and Information Retrieval Systems ...operation of mechanized claims processing and information retrieval...

2010-10-01

193

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

Code of Federal Regulations, 2010 CFR

...operation of mechanized claims processing and information retrieval systems. ...ADMINISTRATION Mechanized Claims Processing and Information Retrieval Systems ...operation of mechanized claims processing and information retrieval...

2009-10-01

194

Laser hardening process simulation for mechanical parts  

NASA Astrophysics Data System (ADS)

In this paper a numerical simulation of laser hardening process is presented. The Finite Difference Method (FDM) was used to solve the heat transfer and the carbon diffusion equations for a defined workpiece geometry. The model is able to predict the thermal cycle into the target material, the phase transformations and the resulting micro-structures according to the laser parameters, the workpiece dimensions and the physical properties of the workpiece. The effects of the overlapping tracks of the laser beam on the resulting micro-structures is also considered. The initial workpiece micro-structure is taken into account in the simulation by a digitized photomicrograph of the ferrite perlite distribution before the thermal cycle. Experimental tests were realized on a C43 plate and the good agreement between the theoretical and experimental results is shown.

Tani, G.; Orazi, L.; Fortunato, A.; Campana, G.; Cuccolini, G.

2007-03-01

195

Ion and electron trapping: release and relaxation processes in fluoride crystals  

NASA Astrophysics Data System (ADS)

The thermally stimulated relaxation (TSR) processes in CaF2, BaF2 and LiBaF3 crystals (X-ray irradiated at LNT or RT) have been investigated by means of the ionic conductivity, thermally stimulated (TS) ionic depolarization current (TSDC), TS current (TSC), TS luminescence (TSL) and thermal bleaching techniques. The ionic TSDC measurements evidence that under DC field fluorides accumulate large ionic space-charge (thermoelectric state is formed) as a result of the migrating anion interstitial and/or vacancy capture on defects. In the ionic conductivity region (290 - 650 K) the thermoelectric state anneals, and several wide and overlapping anionic TSDC peaks are detected. The ionic TSDC stages correlate with the X-ray induced absorption band (F-type and other) thermal bleaching stages. These data evidence that the TSR processes are initiated and controlled by the anion defect thermal detrapping and interaction with the color centers and other localized charges. The anion diffusion-controlled TSR processes take place in fluorides. The TSL, TSC and TSL efficiency (TSL/TSC) data evidence that holes and, probably, the interstitials are detrapped: in CaF2 -- at 125 - 190 K, 260 - 320 K; in LiBaF3 -- at 132 K, 170 K and 220 K. The hole or interstitial diffusion-controlled radiative recombination (TSL) takes place above LNT.

Ziraps, Valters; Kulis, Peteris; Tale, Ivars

2001-04-01

196

Crystal structures of nitroalkane oxidase: insights into the reaction mechanism from a covalent complex of the flavoenzyme trapped during turnover.  

PubMed

Nitroalkane oxidase (NAO) from Fusarium oxysporum catalyzes the oxidation of neutral nitroalkanes to the corresponding aldehydes or ketones with the production of H(2)O(2) 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 A 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 A resolution. The c axis for the trigonal space group of oxidized NAO is 485 A, and there are six subunits (1(1)/(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(ox)). The active-site structures of E(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 A. 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. PMID:16430210

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

2006-01-31

197

Ion trap technology at accelerator facilities  

Microsoft Academic Search

Ion traps allow the capture, accumulation and confinement of charged particles at rest, in vacuum. These particles can then be manipulated and studied at will in the traps or transferred to other devices. The present paper will discuss the trapping mechanisms, concentrating on capture of externally created ions, for different types of ion traps. It will then discuss the advantage

G. Savard

1996-01-01

198

Ion trap technology at accelerator facilities  

Microsoft Academic Search

Ion traps allow the capture, accumulation and confinement of charged particles at rest, in vacuum. These particles can then be manipulated and studied at will in the traps or transferred to other devices. The present paper will discuss the trapping mechanisms, concentrating on capture of externally created ions, for different types of ion traps. It will then discuss the advantage

G. Savard

1997-01-01

199

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

200

Optical trapping  

SciTech Connect

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. [Department of Biological Sciences, and Department of Applied Physics, Stanford University, Stanford, California 94305 (United States)

2004-09-01

201

The processive reaction mechanism of ribonuclease II.  

PubMed

Ribonuclease II is a processive 3' exoribonuclease in Escherichia coli. It degraded substrates with 3'-OH or 2',3'-cyclicP ends slightly faster than those with 3'-P or 2'-P groups with a turnover number of approximately 70 nt/s at 37 degrees C. RNase II does not degrade DNA but the specificity for ribose was not for the cleavage bond but rather for ribo-bonds three to four nucleotides (nt) upstream, which could explain why the limit digest is a dimer. Oligonucleotides (oligos) of deoxy(C) were reversible competitive inhibitors of the enzyme and indicated a strong upstream binding site (approximately 15 to 27 nt from the 3' end). These oligos could protect RNase II from inactivation by heat or from diethylpyrocarbonate, an agent that preferentially reacts with His residues. Compared to oligo(dC), oligos of (dA) were at least 500 times less effective inhibitors of RNase II. Using mixed oligo(dAdC) inhibitors, an obligatory 3' to 5' direction of binding into the catalytic site was shown. From the reaction kinetics of RNase II under different conditions it was concluded that the enzyme recognition differs for poly(A), poly(C) and poly(U). Poly(C) was degraded more slowly than poly(A) or poly(U) with a 3.5 times slower Vmax, while rate differences between small oligos were extreme; oligo(A)7 was degraded > 100 times faster than oligo(C)7. Ethanol, which weakens hydrophobic interactions, increased the reaction velocity of poly(C) to that of poly(A) and poly(U). It had no effect on the reaction velocities of poly(A) or poly(U), but decreased the binding of poly(A) markedly. Oligo(A) was bound more strongly to a hydrophobic column than was oligo(C). Salt, which affects charge interactions, decreased the binding affinity and/or association rate of poly(C) to RNase II, had a lesser effect on poly(U), but the reactions of poly(A) were unaffected even in much higher concentrations of salt. A clue to the slower reaction velocity of poly(C) was shown when the reaction intermediates were viewed by PAGE. At lower temperatures of reaction (< 25 degrees C), there were more intense bands separated by discrete distances of approximately 12 nt during the degradation of poly(C) by RNase II. Chase experiments showed that these stops were accounted for by dissociation of poly(C) from the enzyme. They were not seen when poly(C) was degraded at 37 degrees C or degraded in the presence of 20% ethanol at any temperatures, nor were they seen when poly(A) or poly(U) was degraded even at low temperatures.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7966309

Cannistraro, V J; Kennell, D

1994-11-11

202

Mechanism of the dielectric relaxation process in dibenzoyl  

Microsoft Academic Search

The dielectric relaxation process of dibenzoyl in p-xylene has been investigated by means of measurements in the GHz region at various temperatures. It was found that the Goulon-Rivail model provides a good description of the mechanism.

P. Freundlich; H. A. Kolodzie; S. Sorriso

1984-01-01

203

Quantum dressed classical mechanics: application to non-adiabatic processes  

Microsoft Academic Search

A newly formulated theory for time-dependent molecular quantum mechanics is used to study processes involving more than one potential energy surface. Good agreement with exact numbers is obtained using one trajectory and just two grid points.

Gert D. Billing

2001-01-01

204

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

205

Defense Mechanisms in Psychology Today: Further Processes for Adaptation  

Microsoft Academic Search

Although the concept of the defense mechanism was rejected from academic psychology for a number of years, recent empirical studies show renewed interest in defenses. Cognitive psychologists have confirmed the existence of unconscious psychological processes, a requisite for defenses. Developmental, personality, and social psychologists have all found evidence for defense mechanisms that explicate psychological functioning. The relevance of this new

Phebe Cramer

2000-01-01

206

Application of PLM processes to respond to mechanical SMEs needs  

Microsoft Academic Search

PLM is today a reality for mechanical SMEs. Some companies implement PLM systems very well but others have more difficulties. This paper aims to explain why some SMEs do not success to integrated PLM systems analyzing the needs of mechanical SMEs, the processes to implement to respond to those needs and the actual PLM software functionalities. The proposition of a

Julien Le Duigou; Alain Bernard; Nicolas Perry; Jean-Charles Delplace

2010-01-01

207

ESD failure modes: characteristics mechanisms, and process influences  

Microsoft Academic Search

Electrostatic discharge (ESD) failure modes in advanced CMOS processes have been electrically and physically characterized, and an analysis has been made of the mechanisms of each of the main failure modes. The physical failure modes have been related to the electrical degradation and, therefore, the electrical signatures of the damage mechanisms have been obtained. The distribution of the electrical characteristics

Ajith Amerasekera; Werner van den Abeelen; Leo van Roozendaal; Marcel Hannemann; Paul Schofield

1992-01-01

208

Read-disturb degradation mechanism due to electron trapping in the tunnel oxide for low-voltage flash memories  

Microsoft Academic Search

This paper describes the degradation of read-disturb characteristics related to time-dependent current caused by electron trapping in tunnel-oxide film. The time-dependent current, rather than the stress-induced leakage current, affects the threshold-voltage shift in memory cells with relatively thick tunnel oxide (>7 nm) and long disturbance time. Programming and erase endurance affects read disturb such that the read-disturb lifetime is improved

M. Kato; N. Miyamoto; H. Kume; A. Satoh; T. Adachi; M. Ushiyama; K. Kimura

1994-01-01

209

Holographic optical trapping  

SciTech Connect

Holographic optical tweezers use computer-generated holograms to create arbitrary three-dimensional configurations of single-beam optical traps that are useful for capturing, moving, and transforming mesoscopic objects. Through a combination of beam-splitting, mode-forming, and adaptive wavefront correction, holographic traps can exert precisely specified and characterized forces and torques on objects ranging in size from a few nanometers to hundreds of micrometers. Offering nanometer-scale spatial resolution and real-time reconfigurability, holographic optical traps provide unsurpassed access to the microscopic world and have found applications in fundamental research, manufacturing, and materials processing.

Grier, David G.; Roichman, Yael

2006-02-10

210

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

211

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

212

Mechanization and automation of production processes in turbine building  

Microsoft Academic Search

Specialists at the All-Union Institute of Planning and Technology of Energy Machine Building are working on the problem of mechanization and automation of production processes. One of the major technological processes being worked on is the production of welded units. At the present time the Institute has designed a centralized cutting and manufacturing shop in use at several metallurgical plants,

V. P. Slobodyanyuk

1984-01-01

213

Evaluation of membrane fouling mechanism in various membrane pretreatment processes  

Microsoft Academic Search

Pretreatment of organic matter with coagulation and MIEX® was evaluated using bench-scale experimental procedures on NOM to determine its effect on subsequent UF or MF membrane filtration. Moreover, this work determines the membrane fouling mechanisms according to membrane pretreatment conditions. When applying the MIEX® process as a pretreatment, flux decline was significantly higher than that of the coagulation process. The

C. W. Jung; H. J. Son

2009-01-01

214

Thermo-Mechanical Processing Parameters for the INCONEL ALLOY 740  

SciTech Connect

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 had developed an alloy, commercially known as INCONEL alloy 740, which exhibited various beneficial physical, mechanical, and chemical properties. As part of SMC's on-going efforts to optimize this alloy for targeted boiler applications there was a need to develop an understanding of the thermo-mechanical response of the material, characterize the resulting microstructure from this processing, and possibly, utilize models to develop the appropriate processing scheme for this product.

Ludtka, G.M.; Smith, G.

2007-11-19

215

Deformation conditions for Ni powders undergoing mechanical processing  

NASA Astrophysics Data System (ADS)

Ni powders were submitted to mechanical processing by ball milling. The microstructural refinement of the processed powders was followed by X-ray diffraction by evaluating the average crystallite size and the average strain content. The Vickers micro-hardness was also measured. The experimental evidences were rationalized using a phenomenological model, which allowed to estimate the amount of powder processed at individual collisions. The density of dislocations was also estimated and correlated with the experimental Vickers micro-hardness values. The connection between the work- and gain-hardening mechanisms described by the Bailey-Hirsch and Hall-Petch relationships is discussed.

Garroni, Sebastiano

2012-06-01

216

Deformation band formation as coupled mechanical and chemical processes  

NASA Astrophysics Data System (ADS)

Processes of deformation localization in granular or porous sediments and sedimentary rock control strength, permeability, and frictional properties of the upper few kilometer of the Earth's crust. Structures resulting from these processes, referred to as deformation bands, have been recognized and described with an emphasis on the mechanical processes including grain translation, rotation, and breakage, and particle mixing and differentiation with increasing strain. The interaction of these mechanical processes with chemical processes has received little study. Such chemical reactions include the precipitation of carbonate and quartz cement, dissolution and albitization of feldspar, and the neoformation and infiltration of clay minerals. It is shown that the mechanical process of deformation localization is strongly controlled by chemical processes including pre- kinematic pore-filling cement, syn-kinematic cement filling intra- and transgranular fractures, and stress- enhanced dissolution reactions. Prekinematic cements reduce the strength contrast between grain and aggregate thus favoring deformation localization into narrow, well defined deformation bands. Prekinematic cementation and compaction may even favor thoroughgoing opening mode fractures and prevent localization in the form of deformation bands entirely. Synkinematic cements within deformation bands will result in local strain hardening of bands and thus oppose further deformation localization with increasing strain. By comparing these mechanical-chemical interactions in deformation bands in sand and sandstone from a variety of depositional, structural, and burial settings we attempt to assess the effects of initial sediment composition, compaction state, loading conditions, and chemical environment on deformation localization and its implications on strength, failure mode, and permeability evolution.

Eichhubl, P.; Aydin, A.; Lander, R. H.; Laubach, S. E.; Reed, R. M.; Boles, J. R.; Du Bernard, X.

2006-12-01

217

Examining sediment transport processes within two submarine canyons off coastal southern California using sediment trap arrays and naturally-occurring radionuclides  

NASA Astrophysics Data System (ADS)

The transport of sediment was examined in two submarine canyons (Mugu and Hueneme) located in southern California, just south of Ventura. Two vertically-separated sediment traps were deployed in each canyon for approximately 6 months. The mooring in Mugu Canyon, which presumably receives most of its sediment load from the Calleguas Creek, was deployed in 180m of water and the two sediment traps were positioned 30m and 60m above the sea floor. Huemene Canyon lies just south of the Santa Clara River and in this system the sediment traps were also located at 30m and 60m above the sea floor on a mooring deployed in 190m of water. As has been shown previously, the offshore transport of sediment from land in this region occurs mostly during episodic winter storm events that can deliver sediment as distinct pulses that are usually correlated to heightened precipitation events. Naturally-occurring radionuclides were measured in discrete time-stamped intervals of the four extruded sediment trap columns to obtain time-series flux estimates that can provide insight into particle scavenging and removal processes. In general, 226Ra fluxes (1-31 dpm g-1 d-1) are highly correlated (R2 up to 95) to total mass fluxes (1-13 g m-2 d-1), while excess xs210Pb:total mass fluxes reveal substantial additional input/removal processes. An xs234Th-based geochronology (0.4cm d-1) of the Mugu Canyon upper sediment trap is consistent with the observed (80cm in 190 d) sedimentation rate. Our results suggest that in these two submarine canyon systems, the supply of sediment consists of two components (allochthonous and reworked/resuspended) that can be tracked using naturally-occurring radionuclides.

Swarzenski, P. W.; Xu, J.

2008-12-01

218

Thermal motion of an optically trapped nanotool  

NASA Astrophysics Data System (ADS)

By using multiple optical traps suitably sized complex bodies can be bound with respect to their positions and orientations. One recent application of this involves the use of an elongated object, equipped with a probe (a "nanotool"), to measure and apply pico-Newton sized forces to, for example, the surface of a cell. This application has been described as an optical atomic force microscope (AFM). Calculations of the mechanical susceptibility of trapped probes, and their hydrodynamic resistance are presented. These quantities are used to assess the subsequent thermal motion of an optically trapped nanotool in the context of the Orstein-Uhlenbeck process. Implications for the resolution and general behavior of the optical AFM referred to above are discussed.

Simpson, Stephen H.; Miles, Mervyn J.; Hanna, Simon

2009-08-01

219

Traps and seals I. Structural\\/fault-seal and hydrodynamic traps  

Microsoft Academic Search

This text is a reprint of earlier papers which are part of the Treatis of Petroleum Geology. This text is part of a two volume set on oil and gas traps. The papers in these two volumes deal mainly with the mechanics of trapping hydrocarbons and with trap types. Methods of exploring for traps are discussed in another volume entitled

N. H. Foster; E. A. Beaumont

1988-01-01

220

Early olfactory processing in Drosophila: mechanisms and principles.  

PubMed

In the olfactory system of Drosophila melanogaster, it is relatively straightforward to target in vivo measurements of neural activity to specific processing channels. 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. These mechanisms also 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. PMID:23841839

Wilson, Rachel I

2013-07-01

221

Protein-based bioplastics: effect of thermo-mechanical processing  

Microsoft Academic Search

Bioplastics based on glycerol and different proteins (wheat gluten, albumen, rice and albumen\\/gluten blends) have been manufactured\\u000a to determine the effect that processing and further thermal treatments exert on different thermo-mechanical properties of\\u000a the bioplastics obtained. Oscillatory shear, modulated differential scanning calorimetry, dynamic mechanical thermal analysis,\\u000a thermo-gravimetric analysis and water absorption tests were carried out to study the effect of

Abel Jerez; Pedro Partal; Inmaculada Martínez; Críspulo Gallegos; Antonio Guerrero

2007-01-01

222

ThermoMechanical Processing and Properties of a Ductile Iron  

Microsoft Academic Search

Thermo-mechanical processing of ductile irons is a potential method for enhancing their mechanical properties. A ductile cast iron containing 3.6% C, 2.6% Si and 0.045% Mg was continuously hot-and-warm rolled or one-step press-forged from a temperature in the austenite range (900°C-1100°C) to a temperature below the A, temperature. Various amounts of reduction were used (from 60% to more than 90%)

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

1997-01-01

223

Back surface reflectors with periodic textures fabricated by self-ordering process for light trapping in thin-film microcrystalline silicon solar cells  

Microsoft Academic Search

Back surface reflectors (BSRs) with grating structures have been developed to enhance light trapping in thin-film hydrogenated microcrystalline Si (?c-Si:H) solar cells. As a grating structure, a periodic honeycomb-like dimple pattern with a period of ?450nm has been fabricated on Al substrates by a self-ordering process using anodic oxidation of Al. The clear diffraction effect has been confirmed on the

Hitoshi Sai; Hiroyuki Fujiwara; Michio Kondo

2009-01-01

224

The mechanism of rare earth incorporation in solution doping process.  

PubMed

The mechanism involved during solution doping process has been systematically investigated by correlating the soot characteristics and solution parameters with the amount of rare earth (RE) incorporated in the core of optical fiber. Experiments show that the amount of RE incorporation may be controlled with better precision by adjusting Al ion concentration in the soaking solution. A model has been developed on the basis of cooperative adsorption mechanism correlating different parameters in the overall process. Theoretical estimation shows good agreement with the experimental results and can be used to predict the extent of RE incorporation for any composition if the soot layer characteristics are known. PMID:18711522

Dhar, Anirban; Pal, Atasi; Paul, Mukul Ch; Ray, P; Maiti, Himadri S; Sen, Ranjan

2008-08-18

225

Improving Software Development Process through Economic Mechanism Design  

NASA Astrophysics Data System (ADS)

We introduce the novel concept of applying economic mechanism design to software development process, and aim to find ways to adjust the incentives and disincentives of the software organization to align them with the motivations of the participants in order to maximize the delivered value of a software project. We envision a set of principles to design processes that allow people to be self motivated but constantly working toward project goals. The resulting economic mechanism will rely on game theoretic principles (i.e. Stackelberg games) for leveraging the incentives, goals and motivation of the participants in the service of project and organizational goals.

Yilmaz, Murat; O'Connor, Rory V.; Collins, John

226

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

227

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

228

Thermoplastics as engineering materials: The mechanics, materials, design, processing link  

Microsoft Academic Search

While the use of plastics has been growing at a significant pace because of weight reduction, ease of fabrication of complex shapes, and cost reduction resulting from function integration, the engineering applications of plastics have only become important in the past fifteen years. An inadequate understanding of the mechanics issues underlying the close coupling among the design, the processing (fabrication),

Vijay K. Stokes

1995-01-01

229

Neurobiological mechanisms for opponent motivational processes in addiction  

Microsoft Academic Search

The conceptualization of drug addiction as a compulsive disorder with excessive drug intake and loss of control over intake requires motivational mechanisms. Opponent process as a motivational theory for the negative reinforcement of drug dependence has long required a neurobiological explanation. Key neurochemical elements involved in reward and stress within basal forebrain structures involving the ventral striatum and extended amygdala

George F. Koob; Michel Le Moal

2008-01-01

230

In-line monitoring of chemical-mechanical polishing processes  

NASA Astrophysics Data System (ADS)

We present an overview of in-line monitoring of chemical- mechanical polishing (CMP) processes. We discuss the technical challenges and review many of the approaches that have been published. Several methods are currently under investigation including optical, thermal (pad temperature), friction (torque motor current), electrochemical, and acoustic (vibration).

Hetherington, Dale L.; Stein, David J.

1999-08-01

231

Conscious Processing of Sexual Information: Mechanisms of Appraisal  

Microsoft Academic Search

To elucidate some of the activational mechanisms of sexual response, this study investigated the effects of conscious appraisal of sexual and neutral stimuli on a categorization task and on ratings of sexual arousal. Conscious appraisal is dependent on memory, regulatory, and attentional processes, interacting with one another. It is proposed that regulation is activated by attention, furnished by representations from

Mark Spiering; Walter Everaerd; Ellen Laan

2004-01-01

232

Entanglement of Trapped Ions  

NASA Astrophysics Data System (ADS)

Entanglement, its generation, manipulation, measurement and fundamental understanding is at the very heart of quantum mechanics. We here report on the creation and characterization of entangled states of up to 8 trapped ions, the investigation of long-lived two-ion Bell-states and on experiments towards entangling ions and photons.

Becher, C.; Benhelm, J.; Chek-Al-Kar, D.; Chwalla, M.; Dür, W.; Gühne, O.; Häffner, H.; Hänsel, W.; Körber, T.; Kreuter, A.; Lancaster, G. P. T.; Monz, T.; Phillips, E. S.; Rapol, U. D.; Riebe, M.; Roos, C. F.; Russo, C.; Schmidt-Kaler, F.; Blatt, R.

2005-12-01

233

Hemispheric differences in the recruitment of semantic processing mechanisms  

PubMed Central

This study examined how the two cerebral hemispheres recruit semantic processing mechanisms by combining event-related potential measures and visual half-field methods in a word priming paradigm in which semantic strength and predictability were manipulated using lexically associated word pairs. Activation patterns on the Late Positive Complex (LPC), linked to controlled aspects of processing, showed that previously documented left hemisphere (LH) processing benefits for word pairs with a weak forward but strong backward association stem from the ability to appreciate meaning relations in an order-independent fashion and/or strategically reorder them. Whereas there is a LH benefit for such strategic processing during comprehension in passive tasks, the present study further showed that the RH is also able to make use of these mechanisms when explicit semantic judgments are required. In both hemispheres, N400 responses, linked to initial semantic activation, were largely graded by association strength, with more amplitude reduction for forward associates and strong, symmetrically associated pairs compared to backward associates and matched weak, symmetrically associated pairs. However, responses to moderately associated pairs were more facilitated after initial presentation to the LH than to the RH. This pattern converges with sentence processing findings that point to LH advantages for using context information to predict features of likely upcoming words. Together, the results suggest that an important basis for hemispheric asymmetries in language comprehension arises from when and how each uses top-down semantic mechanisms to shape initial semantic activation over time.

Kandhadai, Padmapriya; Federmeier, Kara D.

2010-01-01

234

On the construction of point processes in statistical mechanics  

NASA Astrophysics Data System (ADS)

We present a new approach to the construction of point processes of classical statistical mechanics as well as processes related to the Ginibre Bose gas of Brownian loops and to the dissolution in Rd of Ginibre's Fermi-Dirac gas of such loops. This approach is based on the cluster expansion method. We obtain the existence of Gibbs perturbations of a large class of point processes. Moreover, it is shown that certain ``limiting Gibbs processes'' are Gibbs in the sense of Dobrushin, Lanford, and Ruelle if the underlying potential is positive. Finally, Gibbs modifications of infinitely divisible point processes are shown to solve a new integration by parts formula if the underlying potential is positive.

Nehring, Benjamin; Poghosyan, Suren; Zessin, Hans

2013-06-01

235

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS Preparation of Squeezed State and Entanglement State Between Vibrational Motion of Trapped Ion and Light  

Microsoft Academic Search

Several schemes have been proposed to prepare two-mode squeezed state and entanglement state between motional states of a single trapped ion and light. Preparation of two-mode squeezed state is based on interaction of a trapped ion located in light cavity with cavity field. Preparation of entanglement state is based on interaction of a trapped ion located in light cavity with

Zhong-Jie Wang

2010-01-01

236

Network Modeling of EOR Processes: A Combined Invasion Percolation and Dynamic Model for Mobilization of Trapped Oil  

Microsoft Academic Search

A novel concept for modeling pore-scale phenomena included in several enhanced oil recovery (EOR) methods is presented. The\\u000a approach combines a quasi-static invasion percolation model with a single-phase dynamic transport model in order to integrate\\u000a mechanistic chemical oil mobilization methods. A framework is proposed that incorporates mobilization of capillary trapped\\u000a oil. We show how double displacement of reservoir fluids can

S. F. Bolandtaba; A. Skauge

237

Monoatomic layer removal mechanism in chemical mechanical polishing process: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations of nanoscratching processes were used to study the atomic-scale removal mechanism of single crystalline silicon in chemical mechanical polishing (CMP) process and particular attention was paid to the effect of scratching depth. The simulation results under a scratching depth of 1 nm showed that a thick layer of silicon material was removed by chip formation and an amorphous layer was formed on the silicon surface after nanoscratching. By contrast, the simulation results with a depth of 0.1 nm indicated that just one monoatomic layer of workpiece was removed and a well ordered crystalline surface was obtained, which is quite consistent with previous CMP experimental results. Therefore, monoatomic layer removal mechanism was presented, by which it is considered that during CMP process the material was removed by one monoatomic layer after another, and the mechanism could provide a reasonable understanding on how the high precision surface was obtained. Also, the effects of the silica particle size and scratching velocity on the removal mechanism were investigated; the wear regimes and interatomic forces between silica particle and workpiece were studied to account for the different removal mechanisms with indentation depths of 0.1 and 1 nm.

Si, Lina; Guo, Dan; Luo, Jianbin; Lu, Xinchun

2010-03-01

238

INSECT TRAP  

Technology Transfer Automated Retrieval System (TEKTRAN)

FLYBRELLA describes a lightweight inexpensive trap that can be hung like an upside-down umbrella in prominent locations where the house flies rest. It consists of a perforated transparent tube that house flies were found to enter readily, containing a strip of rapid-acting sugar-based toxicant. An i...

239

A quantum mechanical model of Rabi oscillations between two interacting harmonic oscillator modes and the interconversion of modes in a Penning trap  

NASA Astrophysics Data System (ADS)

When a Penning trap is operated with an additional quadrupole driving field with a frequency that equals a suitable combination (sum or difference) of the frequencies of the fundamental modes of motion (modified cyclotron, magnetron and axial frequency), then a periodic conversion of the participating modes into each other is observed, strongly resembling the Rabi oscillations in a 2-level atom driven by a laser field tuned to the transition frequency. This investigation attempts to understand on a fundamental level how and why the motion of a classical particle in a macroscopic apparatus can be truely analogous to the oscillations of states of quantum mechanical 2-level systems (2-level atom or magnetic resonance). Ion motion in a Penning trap with an additional quadrupole driving field is described in a quantum mechanical frame work. The Heisenberg equations of motion for the creation and annihilation operators of the interacting oscillators have been explicitly solved, the time development operator of the Schrödinger picture has been determined. The driving field provides for two types of intermode interaction: Type I preserves the total number of excitation quanta present in the two interacting modes, the system oscillates between the modes with a frequency corresponding to the Rabi frequency in two-level systems. Type II preserves the difference of the numbers of excitation quanta present in the two interacting modes, it causes the ion motion to become unbounded. The two types of interaction are associated in a natural way with a SU(2) and a SU(1,1) Lie algebra. The three generators of these algebras form a vector operator that we denote as the Bloch vector operator. The Hilbert space decomposes in a natural way into invariant subspaces, finite dimensional in the case of type I interaction (SU(2)-algebra) and infinite dimensional in the case of type II interaction (SU(1,1)-algebra). The physics of the 2-level atom in the laser field can be described in the 2-dimensional (the lowest nontrivial) sector of the Hilbert space associated with the type I (SU(2)-algebra) interaction. The Bloch vector, well known from quantum optics, is the expectation value of our Bloch operator. On the other hand, the description of ion motion in the Penning trap requires the whole infinite dimensional Hilbert space of our model. Classical ion trajectories are obtained by calculating for the observables corresponding to position and momentum the expectation values with respect to minimum uncertainty coherent oscillator states.

Kretzschmar, Martin

1999-01-01

240

A quantum mechanical model of Rabi oscillations between two interacting harmonic oscillator modes and the interconversion of modes in a Penning trap  

SciTech Connect

When a Penning trap is operated with an additional quadrupole driving field with a frequency that equals a suitable combination (sum or difference) of the frequencies of the fundamental modes of motion (modified cyclotron, magnetron and axial frequency), then a periodic conversion of the participating modes into each other is observed, strongly resembling the Rabi oscillations in a 2-level atom driven by a laser field tuned to the transition frequency. This investigation attempts to understand on a fundamental level how and why the motion of a classical particle in a macroscopic apparatus can be truely analogous to the oscillations of states of quantum mechanical 2-level systems (2-level atom or magnetic resonance). Ion motion in a Penning trap with an additional quadrupole driving field is described in a quantum mechanical frame work. The Heisenberg equations of motion for the creation and annihilation operators of the interacting oscillators have been explicitly solved, the time development operator of the Schroedinger picture has been determined. The driving field provides for two types of intermode interaction: Type I preserves the total number of excitation quanta present in the two interacting modes, the system oscillates between the modes with a frequency corresponding to the Rabi frequency in two-level systems. Type II preserves the difference of the numbers of excitation quanta present in the two interacting modes, it causes the ion motion to become unbounded. The two types of interaction are associated in a natural way with a SU(2) and a SU(1,1) Lie algebra. The three generators of these algebras form a vector operator that we denote as the Bloch vector operator. The Hilbert space decomposes in a natural way into invariant subspaces, finite dimensional in the case of type I interaction (SU(2)-algebra) and infinite dimensional in the case of type II interaction (SU(1,1)-algebra). The physics of the 2-level atom in the laser field can be described in the 2-dimensional (the lowest nontrivial) sector of the Hilbert space associated with the type I (SU(2)-algebra) interaction. The Bloch vector, well known from quantum optics, is the expectation value of our Bloch operator. On the other hand, the description of ion motion in the Penning trap requires the whole infinite dimensional Hilbert space of our model. Classical ion trajectories are obtained by calculating for the observables corresponding to position and momentum the expectation values with respect to minimum uncertainty coherent oscillator states.

Kretzschmar, Martin [Institut fuer Physik, Johannes-Gutenberg-Universitaet, 55099 Mainz (Germany)

1999-01-15

241

Photooxidation Mechanism of Fenthion by Singlet Oxygen: Evidence by ESR Analysis with a Selective Spin Trapping Agent  

Microsoft Academic Search

Our previous study suggested that UVB irradiation of the organophosphorus pesticide, fenthion and its photodegradation product, 3-methyl-4-methylthiophenol (MMTP) yielded fenthion sulfoxide and 3-methyl-4- methylsulfinylphenol (MMSP), and that the formation mechanism was related to generation of singlet oxygen (1O2). The objective of this study was to elucidate the 1O2-triggered photooxidation mechanism of fenthion in detail. Gen- eration of 1O2 in the

Yoshichika Hirahara; Tomofumi Okuno; Hitoshi Ueno; Katsuhiko Nakamurob

2003-01-01

242

Quantum processes as a mechanism in olfaction for smell recognition?  

NASA Astrophysics Data System (ADS)

The physics of smell is not well understood. The biological processes that occur following a signalling event are well understood (Buck 1991). However, the reasons how and why a signalling event occurs when a particular smell molecule and receptor combination is made, remains un-established. Luca Turin proposes a signalling mechanism which determines smell molecules by quantum mechanics (Turin 1996). Investigation of this mechanism shows it to be physically robust (Brookes,et al, 2007), and consequences of the theory provides quantitative measurements of smell and interesting potential experiments that may determine whether the recognition of smell is a quantum event. Brookes, J.C, Hartoutsiou, F, Horsfield, A.P and Stoneham, A.M. (2007). Physical Review Letters 98, no. 3 038101 Buck, L. ( 1991) Cell, 65, no.1 (4): 175-187. Turin, L. (1996) Chemical Sences 21, no 6. 773-791

Brookes, Jennifer

2011-03-01

243

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

244

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

245

Large deviations of ergodic counting processes: a statistical mechanics approach.  

PubMed

The large-deviation method allows to characterize an ergodic counting process in terms of a thermodynamic frame where a free energy function determines the asymptotic nonstationary statistical properties of its fluctuations. Here we study this formalism through a statistical mechanics approach, that is, with an auxiliary counting process that maximizes an entropy function associated with the thermodynamic potential. We show that the realizations of this auxiliary process can be obtained after applying a conditional measurement scheme to the original ones, providing is this way an alternative measurement interpretation of the thermodynamic approach. General results are obtained for renewal counting processes, that is, those where the time intervals between consecutive events are independent and defined by a unique waiting time distribution. The underlying statistical mechanics is controlled by the same waiting time distribution, rescaled by an exponential decay measured by the free energy function. A scale invariance, shift closure, and intermittence phenomena are obtained and interpreted in this context. Similar conclusions apply for nonrenewal processes when the memory between successive events is induced by a stochastic waiting time distribution. PMID:21867147

Budini, Adrián A

2011-07-27

246

The interplay between cell signalling and mechanics in developmental processes.  

PubMed

Force production and the propagation of stress and strain 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 behaviours and cell fates. In this Review we discuss key roles for biomechanics during development to directly shape tissues, to provide positional information for cell fate decisions and to enable robust programmes of development. Several recently identified molecular mechanisms suggest how cells and tissues might coordinate their responses to biomechanical cues. Finally, we outline long-term challenges in integrating biomechanics with genetic analysis of developing embryos. PMID:24045690

Miller, Callie Johnson; Davidson, Lance A

2013-10-01

247

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

248

Impurity trapping during crystal growth  

Microsoft Academic Search

A computer simulation of dendritic crystal growth was developed and used to derive a relationship between solution trapping and system and process parameters during crystal growth. The relation predicts that trapping will increase with increasing crystal growth velocity and decreasing positive and negative temperature gradients. A flow crystallizer was used to experimentally study the growth of calcium sulphate, potassium aluminum

A. S. Myerson

1977-01-01

249

Quantum mechanical model for two-state jump Markovian process  

Microsoft Academic Search

A quantum mechanical model is given which is equivalent to the stochastic dephasing subject to the two-state jump Markovian process. The stochastic variable corresponds to a Hermitian operator of a spin-1\\/2 system which is embedded in a thermal reservoir, where the time-evolution of the spin-1\\/2 system is described by the quantum master equation of the Lindblad form.

Masashi Ban; Sachiko Kitajima; Kishiko Maruyama; Fumiaki Shibata

2008-01-01

250

Application of advnced process control on mixed-product chemical mechanical polishing process  

Microsoft Academic Search

This research developed a run-to-run (RtR) process control technique on the mix-product chemical mechanical polishing (CMP) process. The model of the mix-product CMP process was constructed by using analysis of variance and time series analysis, Then, it was transferred to the state space form and the extended Kalman filter was employed to estimate the disturbances and update the tool parameter

Chien-Feng Wu; Chcng-Hsicn Chen; Mui-Home Chen; Cheng-Wenc Chen

2011-01-01

251

Experimental analysis of the magnetic field shielding and trapping properties of bulk, melt-processed YBa2Cu3O7-?  

NASA Astrophysics Data System (ADS)

A scanning Hall probe has been used to map the distribution of magnetic field in melt-processed YBa2Cu3O7-? (YBCO) discs prepared by seeded and controlled molten-zone techniques. Both shielded and trapped fields were studied as a function of applied magnetic field for each specimen. A clear four-fold symmetry has been observed in the field distribution of the seeded melt-processed sample, suggesting that there are two planes in the disc which exhibit a weak response to an applied field. Similar magnetic properties were observed for the molten-zone processed sample and attributed to the presence of cracks in the specimen. It was found that the applied field required to saturate each sample was much higher than the maximum observed trapped field, in contradiction to the Bean model for a slab geometry. This effect, which is probably due to the plate geometry of the specimens and the variation of critical current density with magnetic field, has implications for practical applications of bulk melt-processed YBCO.

Cardwell, D. A.; Jiang, X. H.; Astill, D. M.; Lo, W.; Coombs, T. A.; Campbell, A. M.; Larsen, J. G.

1995-02-01

252

Charge Trapping in Dielectrics  

NASA Astrophysics Data System (ADS)

When a dielectric is irradiated by electrons with energy E of several kiloelectron volts, a large number of processes take place: backscattering of incident electrons, excitation and ionization of the electrons in the dielectric with binding energies lower than E, creation of excitons, radiative and nonradiative decays of the excited and ionized states, slowing down of the primary and secondary electrons, and thermalization in the conduction band. The thermalized electrons can move freely in the unoccupied conduction states of the material. If electric connection exists between the dielectric and the apparatus, then the charges normally flow out. Thermalized electrons can also be trapped in excited levels localized in the band gap of the dielectric and nonradiative and radiative recombinations from these levels can be observed. The number of the trapped electrons varies with the structural characteristics of the dielectric. In a monocrystal, this number is weak because the number of the defect states in the band gap is small, making the localization of the charges restricted. In contrast, in a polycrystal or amorphous material, the number of the trapped electrons can be large and increases with the disorder. Information on the charge effects suffered by the sample during its irradiation can be deduced by studying the trapping of electrons in localized states and, consequently, by analyzing radiations emitted from these states in the visible and X-ray ranges. In the case of oxides, F+ centers (oxygen ion vacancy having trapped one electron) and F centers (F+ center having trapped a second electron) are generally present. We will show that the F+ [leftrightarrow A: l&r arrow] F conversion can be used to study the dynamic of the trapping in the oxides. Application to various samples of crystallized and amorphous alumina will be presented.

Bonnelle, C.

2004-12-01

253

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

254

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

2011-08-10

255

Traps and seals I. Structural/fault-seal and hydrodynamic traps  

SciTech Connect

This text is a reprint of earlier papers which are part of the Treatis of Petroleum Geology. This text is part of a two volume set on oil and gas traps. The papers in these two volumes deal mainly with the mechanics of trapping hydrocarbons and with trap types. Methods of exploring for traps are discussed in another volume entitled Methods of Exploration. Numerous case studies and fluid mechanics papers are provided in this text along with the classification techniques.

Foster, N.H.; Beaumont, E.A. (comps.)

1988-01-01

256

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

257

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

258

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

2009-07-31

259

Stochastic processes for indirectly interacting particles and stochastic quantum mechanics  

SciTech Connect

This work has two objectives. The first is to begin a mathematical formalism appropriate to treating particles which only interact with each other indirectly due to hypothesized memory effects in a stochastic medium. More specifically we treat a situation in which a sequence of particles consecutively passes through a region (e.g., a measuring apparatus) in such a way that one particle leaves the region before the next one enters. We want to study a situation in which a particle may interact with other particles that previously passed through the system via disturbances made in the region by these previous particles. Second, we apply the type of stochastic process appearing in this context to the stochastic interpretation of quantum mechanics to obtain a modified version of this interpretation. This version is free of many of the criticisms made against the stochastic interpretation of quantum mechanics.

Buonomano, V.; Prado de Andrade, A.F.

1988-04-01

260

Cellular mechanisms of ?-secretase substrate selection, processing and toxicity  

PubMed Central

Presenilins (PSs) are catalytic components of the ?-secretase proteolytic complexes that produce A? and cell signaling peptides. ?-Secretase substrates are mostly membrane-bound peptides derived following proteolytic cleavage of the extracellular domain of typeI transmembrane proteins. Recent work reveals that ?-secretase substrate processing is regulated by proteins termed ?-Secretase Substrate Recruiting Factors (?SSRFs) that bridge substrates to ?-secretase complexes. These factors constitute novel targets for pharmacological control of specific ?-secretase products such as A? and signaling peptides. PS familial Alzheimer’s disease (FAD) mutants cause a loss of ?-secretase cleavage function at epsilon sites of substrates thus inhibiting production of cell signaling peptides while promoting accumulation of uncleaved toxic substrates. Importantly, ?-secretase inhibitors may cause toxicity in vivo by similar mechanisms. Here we review novel mechanisms that control ?-secretase substrate selection and cleavage and examine their relevance to AD.

Gael, Barthet; Georgakopoulos, Anastasios; Robakis, Nikolaos K.

2012-01-01

261

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS Preparation of Squeezed State and Entanglement State Between Vibrational Motion of Trapped Ion and Light  

NASA Astrophysics Data System (ADS)

Several schemes have been proposed to prepare two-mode squeezed state and entanglement state between motional states of a single trapped ion and light. Preparation of two-mode squeezed state is based on interaction of a trapped ion located in light cavity with cavity field. Preparation of entanglement state is based on interaction of a trapped ion located in light cavity with cavity field and a traveling wave light field.

Wang, Zhong-Jie

2010-12-01

262

42 CFR 433.112 - FFP for design, development, installation or enhancement of mechanized claims processing and...  

Code of Federal Regulations, 2010 CFR

...enhancement of mechanized claims processing and information retrieval systems. ...ADMINISTRATION Mechanized Claims Processing and Information Retrieval Systems ...enhancement of mechanized claims processing and information retrieval...

2010-10-01

263

42 CFR 433.112 - FFP for design, development, installation or enhancement of mechanized claims processing and...  

Code of Federal Regulations, 2010 CFR

...enhancement of mechanized claims processing and information retrieval systems. ...ADMINISTRATION Mechanized Claims Processing and Information Retrieval Systems ...enhancement of mechanized claims processing and information retrieval...

2009-10-01

264

Effects of impurity trapping on irradiation-induced swelling and creep  

SciTech Connect

A general theory of the effects of point defect trapping on radiation-induced swelling and creep deformation rates is developed. The effects on the fraction of defects recombining, and on void nucleation, void growth and creep due to the separate processes of dislocation climb-glide and dislocation climb (the so-called SIPA mechanism) are studied. Trapping of vacancies or interstitials increases total recombination and decreases the rates of deformation processes. For fixed trapping parameters, the reduction is largest for void nucleation, less for void growth and creep due to dislocation climb-glide, and least for creep due to dislocation climb. With this formation, the effects of trapping at multiple vacancy and interstitial traps and of spatial and temporal variation in trap concentrations may be determined. Alternative pictures for viewing point defect trapping in terms of effective recombination and diffusion coefficients are derived. It is shown that previous derivations of these coefficients are incorrect. A rigorous explanation is given of the well-known numerical result that interstitial trapping is significant only if the binding energy exceeds the difference between the vacancy and interstitial migration energies, while vacancy trapping is significant even at small binding energies. Corrections which become necessary at solute concentrations above about 0.1% are described. Numerical results for a wide range of material and irradiation parameters are presented.

Mansur, L. K.; Yoo, M. H.

1977-12-01

265

Investigation on mechanical alloying process for vanadium alloys  

NASA Astrophysics Data System (ADS)

Mechanical alloying (MA) is an efficient approach for fabricating particle-dispersion alloys, and has recently been introduced to strengthen structural materials including vanadium alloys for fusion application. Dissolution behavior of the alloying elements is a key issue for optimizing MA in fabricating particle-dispersion vanadium alloys. This paper studies the MA process for V-4Cr-4Ti alloys with Y addition. The result shows that, in V matrix, the dissolution rate of Y is higher than that of Cr, and the dissolution rate of Cr is higher than that of Ti. In addition, dissolution of milling ball material and dispersion particles can harden the MA-fabricated alloy.

Zheng, P. F.; Nagasaka, T.; Muroga, T.; Chen, J. M.

2013-11-01

266

Trapped antihydrogen.  

PubMed

Antimatter was first predicted in 1931, by Dirac. Work with high-energy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature's fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 10(14) for the frequency of the 1s-to-2s transition), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational behaviour of antimatter. However, so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 10(7) antiprotons and 7?×?10(8) positrons, we observed 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4?±?1.4 events. This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen. PMID:21085118

Andresen, G B; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jonsell, S; Jørgensen, L V; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; el Nasr, S Seif; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2010-11-17

267

Evolution of attention mechanisms for early visual processing  

NASA Astrophysics Data System (ADS)

Early visual processing as a method to speed up computations on visual input data has long been discussed in the computer vision community. The general target of a such approaches is to filter nonrelevant information from the costly higher-level visual processing algorithms. By insertion of this additional filter layer the overall approach can be speeded up without actually changing the visual processing methodology. Being inspired by the layered architecture of the human visual processing apparatus, several approaches for early visual processing have been recently proposed. Most promising in this field is the extraction of a saliency map to determine regions of current attention in the visual field. Such saliency can be computed in a bottom-up manner, i.e. the theory claims that static regions of attention emerge from a certain color footprint, and dynamic regions of attention emerge from connected blobs of textures moving in a uniform way in the visual field. Top-down saliency effects are either unconscious through inherent mechanisms like inhibition-of-return, i.e. within a period of time the attention level paid to a certain region automatically decreases if the properties of that region do not change, or volitional through cognitive feedback, e.g. if an object moves consistently in the visual field. These bottom-up and top-down saliency effects have been implemented and evaluated in a previous computer vision system for the project JAST. In this paper an extension applying evolutionary processes is proposed. The prior vision system utilized multiple threads to analyze the regions of attention delivered from the early processing mechanism. Here, in addition, multiple saliency units are used to produce these regions of attention. All of these saliency units have different parameter-sets. The idea is to let the population of saliency units create regions of attention, then evaluate the results with cognitive feedback and finally apply the genetic mechanism: mutation and cloning of the best performers and extinction of the worst performers considering computation of regions of attention. A fitness function can be derived by evaluating, whether relevant objects are found in the regions created. It can be seen from various experiments, that the approach significantly speeds up visual processing, especially regarding robust ealtime object recognition, compared to an approach not using saliency based preprocessing. Furthermore, the evolutionary algorithm improves the overall performance of the preprocessing system in terms of quality, as the system automatically and autonomously tunes the saliency parameters. The computational overhead produced by periodical clone/delete/mutation operations can be handled well within the realtime constraints of the experimental computer vision system. Nevertheless, limitations apply whenever the visual field does not contain any significant saliency information for some time, but the population still tries to tune the parameters - overfitting avoids generalization in this case and the evolutionary process may be reset by manual intervention.

Müller, Thomas; Knoll, Alois

2011-02-01

268

COLD TRAP  

DOEpatents

An improved linear-flow cold trap is designed for highvacuum applications such as mitigating back migration of diffusion pump oil moiecules. A central pot of liquid nitrogen is nested within and supported by a surrounding, vertical, helical coil of metai sheet, all enveloped by a larger, upright, cylindrical, vacuum vessel. The vertical interstices between successive turns of the coil afford lineal, axial, high-vacuum passages between open mouths at top and bottom of said vessel, while the coil, being cold by virtue of thermal contact of its innermost turn with the nitrogen pot, affords expansive proximate condensation surfaces. (AEC)

Milleron, N.

1963-03-12

269

VACUUM TRAP  

DOEpatents

An improved adsorption vacuum trap for use in vacuum systems was designed. The distinguishing feature is the placement of a plurality of torsionally deformed metallic fins within a vacuum jacket extending from the walls to the central axis so that substantially all gas molecules pass through the jacket will impinge upon the fin surfaces. T fins are heated by direct metallic conduction, thereby ol taining a uniform temperature at the adeorbing surfaces so that essentially all of the condensible impurities from the evacuating gas are removed from the vacuum system.

Gordon, H.S.

1959-09-15

270

Mechanical sensitivity to hydrochemical processes of Monastero Bormida clay  

NASA Astrophysics Data System (ADS)

The paper presents the results of an experimental study on the mechanical behavior of a marly clay, motivated by the recurrent episodes of slope failure induced by intense rainfall events over the area of Langhe (NW Italy). The sensitivity of the material to environmental actions has been systematically explored by reproducing on laboratory samples hydrological and chemical processes similar to those expected to arise on site. Chemomechanical effects due to pore fluid dilution and decalcification have been investigated by testing both reconstituted and intact samples with different degrees of weathering. Pore water salinity was found to have minor consequences on the mechanical behavior of the material at its intact state and at the original calcite content. Decalcification enhanced the chemical sensitivity of the clay minerals constituting the soil matrix, not only by affecting the residual shear strength and the stiffness, but also by magnifying the tendency to swell under chemical loads, inducing a chemical sensitivity over swelling on saturation and enhancing water retention properties. Field observations also support the hypothesis that decalcification followed by interstitial pore water dilution are key factors to take into account to understand the degradation of the mechanical properties and that these phenomena can enhance the instability onset.

Musso, G.; Chighini, S.; Romero, E.

2008-05-01

271

Treating process wastewater employing vacuum distillation using mechanical vapor recompression  

SciTech Connect

Process wastewater has been successfully treated using an enhanced variable vacuum distillation system (VVDS). The removal of contaminants is achieved initially by degassing the liquid under an intense vacuum which removes the volatile organic compounds. The resulting liquid is then distilled under a vacuum using mechanical vapor recompression. The system was invented by Derald McCabe. This innovative treatment system removes virtually all of the contaminants, such as TSS, TDS, BOD{sub 5}, COD, heavy metals and mineral compounds. The resultant aqueous portion normally returns to a neutral pH. Due to the unique system operation, scaling problems (often encountered in conventional distillation) have not been detected in this system. The VVDS is extremely energy efficiency because the heat for distillation is generated and recycled mechanically. Using electricity as the energy source, the approximate operating cost, based on $0.05 KWH, may vary from $0.005 to $0.01 per gallon depending on the size and capacity of the equipment. Based on applications in waste streams performed to-date, the VVDS process has yielded a distilled water stream and the concentrated solids have been used as a byproduct or as a concentrated non-dischargeable waste for disposal.

McCabe, D.L. [Brandt, Houston, TX (United States); Vivona, M.A. [ICF Kaiser Engineers, Inc., Houston, TX (United States). Water and Wastewater Dept.

1999-05-01

272

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

273

Source mechanism and rupture process of Wenchuan great earthquake  

NASA Astrophysics Data System (ADS)

On May 12, 2008, occurred a disastrous earthquake, whose magnitude was later modified to be Ms8.0. Focal mechanism and rupture process of the event were determined by inverting long period waveforms from the world-wide stations. The focal mechanism was obtained by a technique of moment tensor inversion considering source time complexity, indicating that the earthquake was a thrust-dominant event with quite right-lateral component. Based on one of the inverted fault planes, which was of strike 230°/dip35°/rake123°, we selected an area with a length of 510 km in strike direction and a width of 50 km in dip direction and divided it into 255 subfaults of 10 km x 10km for inversion of rupture process. The inverted results showed that the source time function was consisted of at least 3 bigger sub-events with a total duration time of 90s, and the maximum slip value is about 7.3 m and the average slip value is 2.4 m, corresponding the maximum stress drop of 53 MPa and the average stress drop of 18 MPa, respectively. From the static slip dislocation distribution, there were mainly 2 slip-concentrated areas located in Wenchuan and Beichuan, respectively. The rupture broke the ground surface and resulted in the maximum slip of 6.1 m in Wenchuan and 5.6 m in Beichuan, respectively. From the slip-rate snapshots, there existed an evident phenomenon that the rupture strongly extended to SW in 15 s-30 s after the earthquake started, which implied that the rupture have ever come back for some time in the whole rupture process of propagating to NE direction. Also, we calculated the near-fault co-seismic displacement field based on the inverted static slip distribution, and the calculated displacement field well featured the observed intensity contours.

Zhang, Y.; Liu, C.; Chen, Y.; Feng, W.; Xu, L.

2008-12-01

274

Reconstruction of mechanically recorded sound by image processing  

NASA Astrophysics Data System (ADS)

Audio information stored in the undulations of grooves in a medium such as a phonograph record or cylinder may be reconstructed, without contact, by measuring the groove shape using precision optical metrology methods and digital image processing. In this approach, audio signal processing is accomplished by two- or three-dimensional image analysis and processing. The viability of these methods was recently demonstrated on a 78 rpm shellac disc using two-dimensional image acquisition and analysis methods [V. Fadeyev and C. Haber, J. Audio Eng. Soc. 51(12), 1172-1185 (2003)]. The present work expands on these results. A three-dimensional reconstruction of mechanically recorded sound is reported. The source material, an Edison cylinder, was scanned using confocal microscopy and resulted in a faithful playback of the recorded information. Methods to accelerate the scan rates and make these techniques practical for use in working archives are reported as well. [Work supported by the Laboratory Technology Research Program (SC-32), within the Office of Science, U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

Fedeyev, Vitaliy; Haber, Carl; Radding, Zachary; Maul, Christian; McBride, John; Golden, Mitchell

2001-05-01

275

Molecular mechanisms of transformation of SkQ mitotropic quinones and the search for new approaches to creation of selective free radical traps.  

PubMed

Features of the mechanism of action of positively charged benzoquinone derivatives (SkQ), which are the analogs of coenzyme Q (I), plastoquinone (II), and tocopherol (III), are discussed. It is usually considered that the main target of these compounds is mitochondria, where they accumulate due to the positive charge of the molecule. In the present work, it is shown with model systems that the reduced forms of compounds (I-III) under certain conditions can transform into electrically neutral cyclic zwitterions, which theoretically can escape from the matrix of energized mitochondria against the concentration gradient. A weak uncoupling effect of molecules I-III has been found on mitochondria. Its existence is in agreement with the abovementioned transformation of positively charged hydroquinones of type Ia-IIIa into electrically neutral molecules. The data obtained with model systems suggest that the target of SkQ hydroquinones as free radical traps may be not only mitochondria but also biochemical systems of the cytoplasm. Due to the presence of a large number of reactive oxygen species (ROS)-dependent signal systems in a cell, the functioning of cytoplasmic systems might be disturbed under the action of antioxidants. The problem of selective effect of antioxidants is discussed in detail in the present work, and a functional diagram of selective decrease of the "background level" of ROS based on differences in the intensity of background and "signal" ROS fluxes is considered. PMID:19916924

Eremeyev, S A; Kargin, V I; Motovilov, K A; Tashlitsky, V N; Markov, V Yu; Korshunova, G A; Sumbatyan, N V; Vyssokikh, M Yu; Yaguzhinsky, L S

2009-10-01

276

Dual-pitch processing mechanisms in primate auditory cortex.  

PubMed

Pitch, our perception of how high or low a sound is on a musical scale, is a fundamental perceptual attribute of sounds and is important for both music and speech. After more than a century of research, the exact mechanisms used by the auditory system to extract pitch are still being debated. Theoretically, pitch can be computed using either spectral or temporal acoustic features of a sound. We have investigated how cues derived from the temporal envelope and spectrum of an acoustic signal are used for pitch extraction in the common marmoset (Callithrix jacchus), a vocal primate species, by measuring pitch discrimination behaviorally and examining pitch-selective neuronal responses in auditory cortex. We find that pitch is extracted by marmosets using temporal envelope cues for lower pitch sounds composed of higher-order harmonics, whereas spectral cues are used for higher pitch sounds with lower-order harmonics. Our data support dual-pitch processing mechanisms, originally proposed by psychophysicists based on human studies, whereby pitch is extracted using a combination of temporal envelope and spectral cues. PMID:23152599

Bendor, Daniel; Osmanski, Michael S; Wang, Xiaoqin

2012-11-14

277

Dual-Pitch Processing Mechanisms in Primate Auditory Cortex  

PubMed Central

Pitch, our perception of how high or low a sound is on a musical scale, is a fundamental perceptual attribute of sounds and is important for both music and speech. After more than a century of research, the exact mechanisms used by the auditory system to extract pitch are still being debated. Theoretically, pitch can be computed using either spectral or temporal acoustic features of a sound. We have investigated how cues derived from the temporal envelope and spectrum of an acoustic signal are used for pitch extraction in the common marmoset (Callithrix jacchus), a vocal primate species, by measuring pitch discrimination behaviorally and examining pitch-selective neuronal responses in auditory cortex. We find that pitch is extracted by marmosets using temporal envelope cues for lower pitch sounds composed of higher-order harmonics, whereas spectral cues are used for higher pitch sounds with lower-order harmonics. Our data support dual-pitch processing mechanisms, originally proposed by psychophysicists based on human studies, whereby pitch is extracted using a combination of temporal envelope and spectral cues.

Bendor, Daniel; Osmanski, Michael S.

2012-01-01

278

Thermo-Mechanical Processing and Properties of a Ductile Iron  

SciTech Connect

Thermo-mechanical processing of ductile irons is a potential method for enhancing their mechanical properties. A ductile cast iron containing 3.6% C, 2.6% Si and 0.045% Mg was continuously hot-and-warm rolled or one-step press-forged from a temperature in the austenite range (900{degrees}C-1100{degrees}C) to a temperature below the A, temperature. Various amounts of reduction were used (from 60% to more than 90%) followed by a short heat ent at 600`C. The heat ent lead to a structure of fine graphite in a matrix of ferrite and carbides. The hot-and- warm worked materials developed a pearlitic microstructure while the press-forged material developed a spheroidite-like carbide microstructure in the matrix. Cementite-denuded ferrite zones were developed around graphite stringers in the hot-and-warm worked materials, but such zones were absent in the press-forged material. Tensile properties including tensile strength and total elongation were measured along the direction parallel and transverse to the rolling direction and along the direction transverse to the press-forging direction. The tensile ductility and strength both increased with a decrease in the amount of hot-and-warm working. The press- forged materials showed higher strength (645 MPa) than the hot-and-warrn worked materials (575 MPa) when compared at the same ductility level (22% elongation).

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

1997-07-14

279

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

280

Efficient collection of single photons emitted from a trapped ion into a single-mode fiber for scalable quantum-information processing  

SciTech Connect

Interference and coincidence detection of two photons emitted by two remote ions can lead to an entangled state, which is a critical resource for scalable quantum-information processing. Currently the success probabilities of experimental realizations of this protocol are mainly limited by low coupling efficiency of a photon emitted by an ion into a single-mode fiber. Here we consider two strategies to enhance the collection probability of a photon emitted from a trapped Yb{sup +} ion, using analytic methods that can be easily applied to other types of ions or neutral atoms. Our analysis shows that we can achieve fiber coupling efficiency of over 30% with an optical cavity made of a flat fiber tip and a spherical mirror. We also investigate ways to increase the fiber coupling efficiency using high-numerical-aperture optics, and show that collection probability of over 15% is possible with proper control of aberration.

Kim, Taehyun; Maunz, Peter; Kim, Jungsang [Fitzpatrick Institute for Photonics, Electrical and Computer Engineering Department, Duke University, Durham, North Carolina 27708 (United States)

2011-12-15

281

Nitronyl nitroxides as probes to study the mechanism of vasodilatory action of nitrovasodilators, nitrone spin traps, and nitroxides: Role of nitric oxide  

Microsoft Academic Search

Nitronyl nitroxides have been used to trap nitric oxide (·NO) produced during visible irradiation of nitrovasodilators such as sodium nitroprusside (Joseph et al., Biochem. Biophys. Res. Commun. 192:926–934; 1993). We have also shown that nitrone and nitroso spin traps exert a potent vasodilatory effect in the isolated perfused rat heart (Konorev et al., Free Radic. Biol. Med. 14:127–137, 1993). The

Eugene A. Konorev; Margaret M. Tarpey; Joy Joseph; John E. Baker; B. Kalyanaraman

1995-01-01

282

On the elementary mechanism underlying secondary motion processing.  

PubMed

The movement of luminance-defined targets can be easily extracted by elementary motion detectors (EMDs) of the correlation type which often are referred to as Reichardt-detectors. In contrast to such 'primary motion', in 'secondary motion' the moving target is defined by more complex features, like changes in texture, flicker, or local contrast. Such stimulus attributes have to be extracted from the retinal intensity distribution by some nonlinear preprocessing, before they are fed into motion detectors. An intriguing case is the perception of the movement of the motion signal, as is present in theta motion, where an object moves in a different direction than the texture on its surface. A two-layer model of hierarchically organised EMDs has been postulated to account for such motion extraction. Other than for the first layer, the computational nature of the mechanism underlying motion processing in the second layer so far is a matter of speculation, and is therefore characterized here by means of computer simulations and psychophysical experiments. Random dot kinematograms were generated in which sinusoidally modulated vertical dot motion defined gratings, and coherence thresholds were measured for the direction discrimination of a horizontally travelling modulation function. This was done for a variety of spatial frequencies and speeds of the modulation sinusoid. Thresholds turn out to be lowest not for a particular speed, but for a fixed temporal frequency of the modulation function (about 1 cycle per second), when various combinations of fine and coarse, and fast and slow secondary gratings are tested. This result favours a correlation-type mechanism over a gradient-type scheme which should lead to a speed-optimum independent of spatial frequency. PMID:9004321

Zanker, J M

1996-12-29

283

How varying pest and trap densities affect Tribolium castaneum (Coleoptera: Tenebrionidae) capture in pheromone traps  

Technology Transfer Automated Retrieval System (TEKTRAN)

The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is an important insect pest in food processing facilities. Pheromone trapping is frequently used to monitor red flour beetle populations in structures; however, the optimal trap density and the relationship between trap ...

284

Simultaneous trapping of two different atomic species in a vapor-cell magneto-optical trap  

Microsoft Academic Search

We have produced a magneto-optical trap that simultaneously confines two different atomic species: sodium and potassium. A measurement of the sodium trap loss rate constant due to collisions with cold potassium atoms was performed. We extract this rate constant by measuring the temporal behavior of the loading process of the sodium trap in the presence and absence of cold potassium.

M. S. Santos; P. Nussenzveig; L. G. Marcassa; K. Helmerson; J. Flemming; S. C. Zilio; V. S. Bagnato

1995-01-01

285

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

286

Policies and mechanisms to support process evolution in PSEEs  

Microsoft Academic Search

This paper discusses the characteristics that should be offered by PSEEs (process-centered software engineering environments) to support the evolution of the software process. A PSEE is a software engineering environment based on the explicit representation of the software process (the process model). Processes and process models are dynamic entities that need to evolve. Existing PSEEs offer limited capabilities to support

Sergio Bandinelli; E. Di Nitto; A. Fuggetta

1994-01-01

287

Neural mechanisms for processing binocular information I. Simple cells.  

PubMed

The visual system integrates information from the left and right eyes and constructs a visual world that is perceived as single and three dimensional. To understand neural mechanisms underlying this process, it is important to learn about how signals from the two eyes interact at the level of single neurons. Using a sophisticated receptive field (RF) mapping technique that employs binary m-sequences, we have determined the rules of binocular interactions exhibited by simple cells in the cat's striate cortex in relation to the structure of their monocular RFs. We find that binocular interaction RFs of most simple cells are well described as the product of left and right eye RFs. Therefore the binocular interactions depend not only on binocular disparity but also on monocular stimulus position or phase. The binocular interaction RF is consistent with that predicted by a model of a linear binocular filter followed by a static nonlinearity. The static nonlinearity is shown to have a shape of a half-power function with an average exponent of approximately 2. Although the initial binocular convergence of signals is linear, the static nonlinearity makes binocular interaction multiplicative at the output of simple cells. This multiplicative binocular interaction is a key ingredient for the computation of interocular cross-correlation, an algorithm for solving the stereo correspondence problem. Therefore simple cells may perform initial computations necessary to solve this problem. PMID:10444685

Anzai, A; Ohzawa, I; Freeman, R D

1999-08-01

288

Mouse Trap Racing in the Computer Age!  

NSDL National Science Digital Library

Students design, build and evaluate a spring-powered mouse trap racer. For evaluation, teams equip their racers with an intelligent brick from a LEGO© MINDSTORMS© NXT Education Base Set and a HiTechnic© acceleration sensor. They use acceleration data collected during the launch to compute velocity and displacement vs. time graphs. In the process, students learn about the importance of fitting mathematical models to measurements of physical quantities, reinforce their knowledge of Newtonian mechanics, deal with design compromises, learn about data acquisition and logging, and carry out collaborative assessment of results from all participating teams.

AMPS GK-12 Program,

289

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

290

zTrap: zebrafish gene trap and enhancer trap database  

PubMed Central

Background We have developed genetic methods in zebrafish by using the Tol2 transposable element; namely, transgenesis, gene trapping, enhancer trapping and the Gal4FF-UAS system. Gene trap constructs contain a splice acceptor and the GFP or Gal4FF (a modified version of the yeast Gal4 transcription activator) gene, and enhancer trap constructs contain the zebrafish hsp70l promoter and the GFP or Gal4FF gene. By performing genetic screens using these constructs, we have generated transgenic zebrafish that express GFP and Gal4FF in specific cells, tissues and organs. Gal4FF expression is visualized by creating double transgenic fish carrying a Gal4FF transgene and the GFP reporter gene placed downstream of the Gal4-recognition sequence (UAS). Further, the Gal4FF-expressing cells can be manipulated by mating with UAS effector fish. For instance, when fish expressing Gal4FF in specific neurons are crossed with the UAS:TeTxLC fish carrying the tetanus neurotoxin gene downstream of UAS, the neuronal activities are inhibited in the double transgenic fish. Thus, these transgenic fish are useful to study developmental biology and neurobiology. Description To increase the usefulness of the transgenic fish resource, we developed a web-based database named zTrap http://kawakami.lab.nig.ac.jp/ztrap/. The zTrap database contains images of GFP and Gal4FF expression patterns, and genomic DNA sequences surrounding the integration sites of the gene trap and enhancer trap constructs. The integration sites are mapped onto the Ensembl zebrafish genome by in-house Blat analysis and can be viewed on the zTrap and Ensembl genome browsers. Furthermore, zTrap is equipped with the functionality to search these data for expression patterns and genomic loci of interest. zTrap contains the information about transgenic fish including UAS reporter and effector fish. Conclusion zTrap is a useful resource to find gene trap and enhancer trap fish lines that express GFP and Gal4FF in desired patterns, and to find insertions of the gene trap and enhancer trap constructs that are located within or near genes of interest. These transgenic fish can be utilized to observe specific cell types during embryogenesis, to manipulate their functions, and to discover novel genes and cis-regulatory elements. Therefore, zTrap should facilitate studies on genomics, developmental biology and neurobiology utilizing the transgenic zebrafish resource.

2010-01-01

291

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

292

Stratigraphy, depositional history, and trapping mechanisms of Lone Tree Creek and Lodgepole Creek oil fields, Lower Cretaceous Fall River formation, Powder River Basin, Wyoming  

SciTech Connect

Stratigraphically trapped accumulations of oil in the Lone Tree Creek and Lodgepole Creek fields occur within and just updip from a fluvial meander belt within the Fall River Formation. The meander belt can be mapped north-to-south over a distance of at least 100 mi (161 km) in the eastern part of the Powder River basin. The northern part of the meander belt contains the oil fields of the Coyote Creek-Miller Creek trend; the southern part contains only the relatively small Lone Tree Creek and Lodgepole Creek fields. These small fields are of considerable interest, as they display a style of stratigraphic trapping of hydrocarbons not observed in the prolific Coyote Creek-Miller Creek trend. The stratigraphic traps of the Coyote Creek-Miller Creek trend occur at updip facing convexities along the eastern edge of the meander belt, with abandonment clay plugs serving as lateral permeability barriers to hydrocarbon migration. Oil has been produced in part of the Lone Tree Creek field from a similar trap. The remaining part of Lone Tree Creek field and Lodgepole creek field produce from stratigraphic traps formed by lateral pinch-outs of delta-front sandstone bodies. These traps are situated updip from and apparently in continuity with the meander-belt deposits, indicating that they may have been charged with hydrocarbons that found their way through the clay-plug barriers along the margin of the meander belt. Similar, undiscovered traps may exist updip from Fall River meander belts elsewhere in the basin.

Gustason, E.R.; Ryer, T.A.

1985-05-01

293

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

294

Copper ion-exchanged channel waveguides optimization for optical trapping.  

PubMed

Optical trapping of particles has become a powerful non-mechanical and non-destructive technique for precise particle positioning. The manipulation of particles in the evanescent field of a channel waveguide potentially allows for sorting and trapping of several particles and cells simultaneously. Channel waveguide designs can be further optimized to increase evanescent field prior to the fabrication process. This is crucial in order to make sure that the surface intensity is sufficient for optical trapping. Simulation configurations are explained in detail with specific simulation flow. Discussion on parameters optimization; physical geometry, optical polarization and wavelength is included in this paper. The effect of physical, optical parameters and beam spot size on evanescent field has been thoroughly discussed. These studies will continue toward the development of a novel copper ion-exchanged waveguide as a method of particle sorting, with biological cell propulsion studies presently underway. PMID:23726859

Reshak, A H; Khor, K N; Shahimin, M M; Murad, S A Z

2013-05-30

295

Optical trapping and evaporative cooling of fermionic atoms  

NASA Astrophysics Data System (ADS)

This dissertation describes the development of the first stable optical trap for neutral atoms and its application to studies of interactions between and evaporative cooling of a gas of fermionic atoms. This work lays the foundation for future investigations of quantum statistical effects in a dilute, ultracold gas of fermionic atoms in which the temperature, density and interaction strength can be independently controlled. Such studies may include the observation of superfluidity via Cooper pair formation at a high critical temperature. In addition, the development of a stable optical trap impacts a wide variety of applications including fundamental precision measurements, quantum computing, improved frequency standards and the precise manipulation of atoms and molecules. Optical traps are ideally suited for studies of interacting Fermi gases since they are able to confine stable two-state mixtures of fermionic atoms. The ability to trap multiple states enables ultracold collisions, which would otherwise be forbidden by the exclusion principle in a single-state fermionic vapor. However, optical traps have previously suffered from residual heating and loss mechanisms, which have limited trap lifetimes to several seconds. Using an ultrastable carbon dioxide laser to confine atoms in an ultrahigh vacuum environment, we minimize all known sources of residual heating including those due to fluctuations in the laser intensity and position. By this method we obtain trap lifetimes of 370 seconds, limited by the background gas pressure of <10-11 Torr, with residual heating rates of < 50 nanoKelvin/sec. The construction of a stable optical trap has enabled the first experimental studies of evaporative cooling of a two-state mixture of lithium fermions. By monitoring the rate of evaporation of atoms from the trap we directly measure a large low-energy cross section predicted to exist for 6Li. Based on the existence of this large interaction strength, an optically trapped gas of lithium atoms is expected to be a promising candidate for the observation of superfluidity in a dilute, ultracold, interacting Fermi gas. Ultracold temperatures and high phase space densities can be achieved in this system through forced evaporative cooling. In this process, the highest energy atoms are selectively removed from the trap by adiabatically lowering the well depth. Using this technique, a temperature of 2.4 ?K with a corresponding phase space density of 1.6 × 10-3 is achieved. Based on a theoretical model of evaporative cooling we describe in this dissertation, we expect that modest improvements to this system should enable cooling to temperatures below the Fermi temperature and possibly below the critical temperature for Cooper pair formation.

O'Hara, Kenneth Martin

2000-11-01

296

Mechanism of FGF23 processing in fibrous dysplasia.  

PubMed

Fibroblast growth factor-23 (FGF23) is a phosphate- and vitamin D-regulating hormone derived from osteoblasts/osteocytes that circulates in both active (intact, iFGF23) and inactive (C-terminal, cFGF23) forms. O-glycosylation by O-glycosyl transferase N-acetylgalactosaminyltransferase 3 (ppGalNAcT3) and differential cleavage by furin have been shown to be involved in regulating the ratio of active to inactive FGF23. Elevated iFGF23 levels are observed in a number of hypophosphatemic disorders, such as X-linked, autosomal recessive, and autosomal dominant hypophosphatemic rickets, whereas low iFGF23 levels are found in the hyperphosphatemic disorder familial tumoral calcinosis/hyperphosphatemic hyperostosis syndrome. Fibrous dysplasia of bone (FD) is associated with increased total FGF23 levels (cFGF23?+?iFGF23); however, classic hypophosphatemic rickets is uncommon. Our results suggest that it can be explained by increased FGF23 cleavage leading to an increase in inactive cFGF23 relative to active iFGF23. Given the fact that FD is caused by activating mutations in the small G-protein G(s) ? that results in increased cyclic adenosine monophosphate (cAMP) levels, we postulated that there may be altered FGF23 cleavage in FD and that the mechanism may involve alterations in cAMP levels and ppGalNacT3 and furin activities. Analysis of blood specimens from patients with FD confirmed that the elevated total FGF23 levels are the result of proportionally increased cFGF23 levels, consistent with less glycosylation and enhanced cleavage by furin. Analysis of primary cell lines of normal and mutation-harboring bone marrow stromal cells (BMSCs) from patients with FD demonstrated that BMSCs harboring the causative G(s) ? mutation had higher cAMP levels, lower ppGalNAcT3, and higher furin activity. These data support the model wherein glycosylation by ppGalNAcT3 inhibits FGF23 cleavage by furin and suggest that FGF23 processing is a regulated process that controls overall FGF23 activity in FD patients. PMID:22247037

Bhattacharyya, Nisan; Wiench, Malgorzata; Dumitrescu, Claudia; Connolly, Brian M; Bugge, Thomas H; Patel, Himatkumar V; Gafni, Rachel I; Cherman, Natasha; Cho, Monique; Hager, Gordon L; Collins, Michael T

2012-05-01

297

Isolating Quantum Mechanical Processes in Billiard Ball Collisions  

NASA Astrophysics Data System (ADS)

The few-body problem remains an important unsolved Physics problem. In atomic collisions, while the interactions are well understood, the problem is still not solvable. However, at intermediate or high energies, the contributions to ionization from binary collisions may be isolated and studied directly. Final-state interactions between the charged projectile and the ejected electron following ionization have been calculated to give cusp-like structures in the differential ionization cross section when the projectile and ejected electron emerge in the same direction with the same speed.(See for example, M.W. Lucas, K.F. Man and W. Steckelmacher, in Lecture Notes in Physics vol. 213, ed K.O. Groeneveld, W. Meckbach and I. Sellin (Berlin: Springer), p1 (1984).) These processes are known as ``capture to the continuum" for a positive projectile and "anticapture to the continuum" for a negative projectile.(L.H. Thomas, Proc. Roy. Soc. A114 561 (1927).)^,(See J.S. Briggs, Comments At. Mol. Phys. 23, 175 (1989), for more recent work.) The projectile can transfer significant momentum in these collisions and two or more outgoing particles can significant velocity after the collision which cannot be accounted for theoretically. Therefor experimental measurements can provide guidance for further theoretical development. We have reported the first experimental evidence of electron anticapture to the continuum at about 45^circ in e^- - Ar scattering at 1000 eV. This double-binary collision mechanism (the electron scattering analogue of the Thomas forward peak in ion-atom scattering) has been isolated by studying correlated projectile and ejected electrons traveling in the same direction following e^--Ar collisions. The cross section for this process rises as 45^circ is approached, but drops precipitously at about 45^circ. This dip is the signature of anticapture to the continuum for negative projectiles and corresponds to a zero Coulomb density of states factor at 45^circ. In addition, a significant departure from the Rutherford formula have been found for the one-electron differential cross section at large scattering angles.

Golden, D. E.

1997-10-01

298

Accurate measurements of the charge pumping current due to individual MOS interface traps and interactions in the carrier capture\\/emission processes  

Microsoft Academic Search

We have successfully measured accurate charge pumping (CP) currents for individual interface traps for the first time, and discovered that the maximum CP current for a single trap is various and usually less than fq (f is the gate pulse frequency, q is the electron charge). From detailed experimental results of the pulse-width dependent CP current, we concluded that the

Toshiaki Tsuchiya

2011-01-01

299

Statistical mechanics of fragmentation processes of ice and rock bodies  

NASA Astrophysics Data System (ADS)

It is a well-known experimental fact that impact fragmentation, specifically of ice and rock bodies, causes a two-step ("knee"-shaped) power distribution of fragment masses with exponent values within the limits -4 and -1.5 (here and henceforth the differential distribution is borne in mind). A new theoretical approach is proposed to determine the exponent values, a minimal fracture mass, and properties of the knee. As a basis for construction of non-equilibrium statistical mechanics of condensed matter fragmentation the maximum-entropy variational principle is used. In contrast to the usual approach founded on the Boltzmann entropy the more general Tsallis entropy allowing stationary solutions not only in the exponential Boltzmann-Gibbs form but in the form of the power (fractal) law distribution as well is invoked. Relying on the analysis of a lot of published experiments a parameter ? is introduced to describe an inhomogeneous distribution of the impact energy over the target. It varies from 0 (for an utterly inhomogeneous distribution of the impact energy) to 1 (for a homogeneous distribution). The lower limit of fragment masses is defined as a characteristic fragment mass for which the energy of fragment formation is minimal. This mass value depends crucially on the value of ?. It is shown that for ??1 only small fragments can be formed, and the maximal permitted fragment (of mass m1) is the upper boundary of the first stage of the fracture process and the point where the knee takes place. The second stage may be realized after a homogeneous redistribution of the remainder of the impact energy over the remainder of the target (when ??1). Here, the formation of great fragments is permitted only and the smallest of them (of mass m2) determines a lower boundary of the second stage. Different forms of the knee can be observed depending on relations between m1 and m2.

Bashkirov, A. G.; Vityazev, A. V.

1996-09-01

300

Multiple trap Laguerre-Gaussian holographic optical tweezers using a multiplexed ferroelectric SLM  

NASA Astrophysics Data System (ADS)

A holographic optical tweezers system is constructed using time-shared multiplexing to generate multiple optical traps. Computer generated Fresnel zone plates are used to produce the required laser focuses for standard optical traps while helical zone plates are used to generate Laguerre-Gaussian (LG) laser modes that produce doughnut shaped focuses. Standard Fresnel zone plates are used for trapping non-biological matter whereas LG modes are used in trapping delicate biological matter that is susceptible to damage from excessive laser radiation. A reflective high speed ferroelectric spatial light modulator (SLM), which is used to display the zone plate images, is capable of multiplexing a maximum of 24 binary images at a refresh rate of up to 1440Hz. By programming the SLM to display one binary hologram per bit plane, a commercial 24 bit colour SLM is used to provide 24 multiplexed traps. The ferroelectric holographic system enables multiple independently movable traps using time-shared multiplexing without the need for mechanical movement within the system. The software developed to display the zone plates uses Open GL acceleration to allow fast smooth movement in real time. Open GL utilises the graphics processing unit (GPU) common on many computers today which greatly increases the frame rate of the images displayed on the SLM. Use of the apparatus is demonstrated by the trapping and manipulation of colloidal particles and yeast cells. Preliminary results indicate that the use of LG zone plates for trapping biological cells results in significantly less damage than standard Fresnel zone plates.

Lafong, A.; Hossack, W. J.; Arlt, J.; Nowakowski, T. J.; Read, N. D.

2006-09-01

301

Excitons in electrostatic traps  

NASA Astrophysics Data System (ADS)

We consider in-plane electrostatic traps for indirect excitons in coupled quantum wells, where the traps are formed by a laterally modulated gate voltage. An intrinsic obstacle for exciton confinement in electrostatic traps is an in-plane electric field that can lead to exciton dissociation. We propose a design to suppress the in-plane electric field and, at the same time, to effectively confine excitons in the electrostatic traps. We present calculations for various classes of electrostatic traps and experimental proof of principle for trapping of indirect excitons in electrostatic traps.

Hammack, A. T.; Gippius, N. A.; Yang, Sen; Andreev, G. O.; Butov, L. V.; Hanson, M.; Gossard, A. C.

2006-03-01

302

On biodiversity conservation and poverty traps  

PubMed Central

This paper introduces a special feature on biodiversity conservation and poverty traps. We define and explain the core concepts and then identify four distinct classes of mechanisms that define important interlinkages between biodiversity and poverty. The multiplicity of candidate mechanisms underscores a major challenge in designing policy appropriate across settings. This framework is then used to introduce the ensuing set of papers, which empirically explore these various mechanisms linking poverty traps and biodiversity conservation.

Barrett, Christopher B.; Travis, Alexander J.; Dasgupta, Partha

2011-01-01

303

On biodiversity conservation and poverty traps.  

PubMed

This paper introduces a special feature on biodiversity conservation and poverty traps. We define and explain the core concepts and then identify four distinct classes of mechanisms that define important interlinkages between biodiversity and poverty. The multiplicity of candidate mechanisms underscores a major challenge in designing policy appropriate across settings. This framework is then used to introduce the ensuing set of papers, which empirically explore these various mechanisms linking poverty traps and biodiversity conservation. PMID:21873176

Barrett, Christopher B; Travis, Alexander J; Dasgupta, Partha

2011-08-22

304

MECHANICAL ANALYSIS OF WEAVING PROCESS TOWARDS SIZE-FREE WEAVING  

Technology Transfer Automated Retrieval System (TEKTRAN)

To achieve efficient weaving of cotton warp yarns with reduced or no size, exploratory efforts towards comprehensive mechanical analyses of various loom components and mechanisms are presented. Theoretical and experimental studies are suggested which involve: 1) modification of loom components made ...

305

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

306

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

2012-03-02

307

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

308

A Study of Optimality Theory and the Human Sentence Processing Mechanism  

Microsoft Academic Search

A Study of Optimality Theory and the Human Sentence Processing Mechanism Rajvinder Singh Abstract: From a computational perspective, parsing is a very interesting phenomenon. All people do it quickly, and all people do it well. The history of cognitive science has been filled with attempts to explain the mechanisms that guide the human sentence processing mechanism (hf. HSPM). These have

Rajvinder Singh

2002-01-01

309

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

310

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Generation of Arbitrary Pure States for Three-dimensional Motion of a Trapped Ion  

NASA Astrophysics Data System (ADS)

In this paper, we propose a scheme for generating an arbitrary three-dimensional pure state of vibrational motion of a trapped ion. Our scheme is based on a sequence of laser pulses, which are tuned to the appropriate vibrational sidebands with respect to the appropriate electronic transition.

Li, Da-Chuang; Wang, Xian-Ping; Dong, Ping; Yang, Ming; Cao, Zhuo-Liang

2010-04-01

311

Stratigraphy, depositional history, and trapping mechanisms of Lone Tree Creek and Lodgepole Creek oil fields, Lower Cretaceous Fall River formation, Powder River Basin, Wyoming  

Microsoft Academic Search

Stratigraphically trapped accumulations of oil in the Lone Tree Creek and Lodgepole Creek fields occur within and just updip from a fluvial meander belt within the Fall River Formation. The meander belt can be mapped north-to-south over a distance of at least 100 mi (161 km) in the eastern part of the Powder River basin. The northern part of the

E. R. Gustason; T. A. Ryer

1985-01-01

312

Magnetic Trapping of Polar Molecules with Buffer-gas Cooling  

NASA Astrophysics Data System (ADS)

Molecules possess a number of features that could greatly expand the possibilities for study of new interactions, collective quantum effects, collisional processes, fundamental tests and chemical processes. This is due to 1) the strong interactions between the dipole moments of polar molecules, 2) the rotational and vibrational internal structure of all molecules, and 3) the easily orientable internal electric field of many polar molecules. The promise of cold and ultracold dipolar molecules will only be realized when samples can be prepared with at least approximately the same ease in which we now prepare atomic samples. Several approaches towards trapping of polar molecules, the key first step toward studying ultracold polar molecules at high density, have already succeeded: direct cooling of molecules via a buffer gas, mechanical slowing of a pulsed molecular beam with electric fields and photoassociation of alkali atoms. Over the past 5 years we have developed the technique of buffer-gas cooling and loading of molecules into magnetic traps, starting with the first trapping of a molecule, CaH, in 1998. Buffer-gas cooling relies solely on elastic collisions (thermalization) of the species-to-be-trapped with a cryogenically cooled helium gas and so is independent of any particular energy level pattern. Using buffer-gas loading, paramagnetic atoms (Cr, Eu, Mo) and molecules (CaH) have been trapped and several other species have been cooled (Na, Ti, Y, Zr, Sc, PbO, and NH) and their collisional properties studied. The process is found to be highly efficient; the number of trapped species limited only by the production method. The general method and recent results will be discussed including the cooling of molecules directly from a molecular beam and the creation of cold molecular beams.

Doyle, John

2004-03-01

313

Neutrophil extracellular traps sequester circulating tumor cells and promote metastasis  

PubMed Central

The majority of patients with cancer undergo at least one surgical procedure as part of their treatment. Severe postsurgical infection is associated with adverse oncologic outcomes; however, the mechanisms underlying this phenomenon are unclear. Emerging evidence suggests that neutrophils, which function as the first line of defense during infections, facilitate cancer progression. Neutrophil extracellular traps (NETs) are extracellular neutrophil-derived DNA webs released in response to inflammatory cues that trap and kill invading pathogens. The role of NETs in cancer progression is entirely unknown. We report that circulating tumor cells become trapped within NETs in vitro under static and dynamic conditions. In a murine model of infection using cecal ligation and puncture, we demonstrated microvascular NET deposition and consequent trapping of circulating lung carcinoma cells within DNA webs. NET trapping was associated with increased formation of hepatic micrometastases at 48 hours and gross metastatic disease burden at 2 weeks following tumor cell injection. These effects were abrogated by NET inhibition with DNAse or a neutrophil elastase inhibitor. These findings implicate NETs in the process of cancer metastasis in the context of systemic infection and identify NETs as potential therapeutic targets.

Cools-Lartigue, Jonathan; Spicer, Jonathan; McDonald, Braedon; Gowing, Stephen; Chow, Simon; Giannias, Betty; Bourdeau, France; Kubes, Paul; Ferri, Lorenzo

2013-01-01

314

Spray Processing and Mechanical Behavior of gamma-TiAl.  

National Technical Information Service (NTIS)

The principal developments during the three-year contract period may be described as follows: design and successful implementation of spray forming experiments using gamma-TiAl alloys; microstructural characterization and mechanical testing on spray forme...

E. J. Lavernia J. C. Earthman

1997-01-01

315

Heating mechanism in relation to the laser machining process  

Microsoft Academic Search

Laser workpiece interaction mechanism is an important phenomenon which will assist in the development of laser machining systems.\\u000a The interaction mechanism is generally complicated and depends on the laser and workpiece properties. In the present study\\u000a a mathematical analysis for the laser material removal by evaporation and radial ejection of liquid is carried out. In the\\u000a analysis the time unsteady

Bekir S Yilbas; Ahmet Z Sahin

1993-01-01

316

Trapping polar molecules in an ac trap  

SciTech Connect

Polar molecules in high-field seeking states cannot be trapped in static traps as Maxwell's equations do not allow a maximum of the electric field in free space. It is possible to generate an electric field that has a saddle point by superposing an inhomogeneous electric field to an homogeneous electric field. In such a field, molecules are focused along one direction, while being defocused along the other. By reversing the direction of the inhomogeneous electric field the focusing and defocusing directions are reversed. When the fields are being switched back and forth at the appropriate rate, this leads to a net focusing force in all directions. We describe possible electrode geometries for creating the desired fields and discuss their merits. Trapping of {sup 15}ND{sub 3} ammonia molecules in a cylindrically symmetric ac trap is demonstrated. We present measurements of the spatial distribution of the trapped cloud as a function of the settings of the trap and compare these to both a simple model assuming a linear force and to full three-dimensional simulations of the experiment. With the optimal settings, molecules within a phase-space volume of 270 mm{sup 3} (m/s){sup 3} remain trapped. This corresponds to a trap depth of about 5 mK and a trap volume of about 20 mm{sup 3}.

Bethlem, Hendrick L. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Laser Centre Vrije Universiteit, De Boelelaan 1081, NL-1081HV Amsterdam (Netherlands); Veldhoven, Jacqueline van [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); FOM-Institute for Plasmaphysics Rijnhuizen, P.O. Box 1207, NL-3430 BE Nieuwegein (Netherlands); Schnell, Melanie; Meijer, Gerard [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

2006-12-15

317

Trap characterization of silicon nitride thin films by a modified trap spectroscopy technique  

NASA Astrophysics Data System (ADS)

Energy levels of traps in silicon nitride are determined using a modified trap spectroscopy method, based on filling of traps using electrical stress followed by optical detrapping, in a metal-silicon nitride-silicon structure. Indium tin oxide with 84% transmittance is used as transparent electrode. Photon energy dependent shift in the flat band voltage is used to estimate type and energetic position of the traps. Here, we report detection of two prominent hole trap levels at 0.5 and 1.1 eV above the valance band edge. The study suggests that phonons hardly participate in the detrapping process of holes in Si3N4.

Midya, Kousik; Dhar, Subhabrata; Kottantharayil, Anil

2013-10-01

318

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

319

Interpretation of mechanical impedance profiles for intelligent control of robotic meat processing  

Microsoft Academic Search

Mechanical processing of meat and fish for packaging and marketing may involve the removal of skin, fat, and bones, and the separation of meats of different texture. In an automated processing workcell that employs robots for such purposes, proper sensing and instrumentation would be quite crucial for fast and accurate control of processing operations. In particular, force and mechanical impedance

J. H. Gu; C. W. de Silva

1996-01-01

320

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 with 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. We present data from the analysis of more than 100 melt inclusions, including both homogenized inclusions and rare glassy inclusions with low crystallinity. Many melt inclusions from tuffs and flows near the base of the Siberian Traps sequence are substantially enriched in chlorine and fluorine compared to Deccan Traps and Laki melt inclusions (Self et al., 2008; Thordarson et al., 1996). These inclusions record chlorine concentrations up to ~1400 ppm, and fluorine concentrations up to ~5000 ppm. 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 substantial concentrations of chlorine. 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 in the range of 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, Benjamin A.; Elkins-Tanton, Linda T.; Rowe, Michael C.; Ukstins Peate, Ingrid

2010-05-01

321

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

322

Trapped inflation  

SciTech Connect

We analyze a distinctive mechanism for inflation in which particle production slows down a scalar field on a steep potential and show how it descends from angular moduli in string compactifications. The analysis of density perturbations--taking into account the integrated effect of the produced particles and their quantum fluctuations--requires somewhat new techniques that we develop. We then determine the conditions for this effect to produce 60 e-foldings of inflation with the correct amplitude of density perturbations at the Gaussian level and show that these requirements can be straightforwardly satisfied. Finally, we estimate the amplitude of the non-Gaussianity in the power spectrum and find a significant equilateral contribution.

Green, Daniel; Horn, Bart; Silverstein, Eva [SLAC and Department of Physics, Stanford University, Stanford, California 94305 (United States); Senatore, Leonardo [School of Natural Sciences, Institute for Advanced Study, Olden Lane, Princeton, New Jersey 08540 (United States); Jefferson Physical Laboratory and Center for Astrophysics, Harvard University, Cambridge, Massachusetts 02138 (United States)

2009-09-15

323

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

324

Database sharing: an efficient mechanism for supporting concurrent processes  

Microsoft Academic Search

The advent of transaction-oriented data processing systems has offered a number of new challenges to designers of database management systems. Requisites for efficient transaction processing include (1) a multiprogramming system oriented toward maximizing throughput subject to the response-time requirement of the interactive environment, and (2) an integrated database with centralized access control. An integrated database implies the elimination of redundant

Paul F. King; Arthur J. Collmeyer

1973-01-01

325

Brain mechanisms for processing perceived emotional vocalizations in humans  

Microsoft Academic Search

Humans express emotional information in their facial expressions and body movements, as well as in their voice. In this chapter we consider the neural processing of a specific kind of vocal expressions, nonverbal emotional vocalizations e.g., laughs and sobs. We outline evidence, from patient studies and functional imaging studies, for both emotion-specific and more general processing of emotional information in

Sophie K. Scott; Disa Sauter; Carolyn McGettigan

2009-01-01

326

Magnetoelectric charge trap memory.  

PubMed

It is demonstrated that a charge-trapping layer placed in proximity to a ferromagnetic metal enables efficient electrical and optical control of the metal's magnetic properties. Retention of charge trapped inside the charge-trapping layer provides nonvolatility to the magnetoelectric effect and enhances its efficiency by an order of magnitude. As such, an engineered charge-trapping layer can be used to realize the magnetoelectric equivalent to today's pervasive charge trap flash memory technology. Moreover, by supplying trapped charges optically instead of electrically, a focused laser beam can be used to imprint the magnetic state into a continuous metal film. PMID:22300444

Bauer, Uwe; Przybylski, Marek; Kirschner, Jürgen; Beach, Geoffrey S D

2012-02-08

327

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

328

Development and validation of a liquid chromatography/linear ion trap mass spectrometry method for the quantitative determination of deoxynivalenol-3-glucoside in processed cereal-derived products.  

PubMed

Cereal-based food can be frequently contaminated by the presence of mycotoxins derived from Fusarium fungus, and, in particular, by deoxynivalenol (DON). Nowadays, analytical strategies for the detection of DON are well developed, but there are gaps for what concerns a correct identification, quantification and toxicological evaluation of the respective metabolites, mainly related to detoxifying actions via plant metabolism or to processing technologies and also referred to as "masked" mycotoxins. Here, we report the development of a liquid chromatography/linear ion trap mass spectrometry method capable of determining deoxynivalenol-3-glucoside (DON-3G), which is the main known DON metabolite, in different processed cereal-derived products. Samples were extracted with a mixture of methanol/water (80:20; v/v) and cleaned up using immunoaffinity columns. Chromatographic separation was performed using a core-shell C(18) column with an aqueous acetic acid/methanol mixture as the mobile phase under gradient conditions. The method was in-house validated on a bread matrix as follows: matrix-matched linearity (r(2)>0.99) was established in the range of 10-200 ?g kg(-1); trueness expressed as recovery was close to 90%; good intermediate precision (overall RSD<9%) and adequate detection quantitation limits (4 and 11 ?g kg(-1), respectively) were achieved. Furthermore, applying a metrology approach based on intralaboratory data, the estimated measurement expanded uncertainty was determined to be equal to 29%. The reliability of the method was finally demonstrated in bread, cracker, biscuit and minicake commodities, resulting in relatively low levels of DON-3G, which were not higher than 30 ?g kg(-1). PMID:23194564

Suman, M; Bergamini, E; Catellani, D; Manzitti, A

2012-07-01

329

Mechanical-thermal processing of a beta-titanium alloy  

Microsoft Academic Search

The mechanical properties of TS 6 (Ti--10 percent Cr--7 percent V--3.5 percent Mo--3 percent Al) alloy were studied. Results are presented in plots showing yield stress vs cold work, notched tensile strength vs unnotched tensile strength, and ultimate tensile strength vs test temperature. (JRD)

Ned W. Polan; Donald H. Avery

1976-01-01

330

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

331

The neural mechanisms of gustation: a distributed processing code  

Microsoft Academic Search

Whenever food is placed in the mouth, taste receptors are stimulated. Simultaneously, different types of sensory fibre that monitor several food attributes such as texture, temperature and odour are activated. Here, we evaluate taste and oral somatosensory peripheral transduction mechanisms as well as the multi-sensory integrative functions of the central pathways that support the complex sensations that we usually associate

Ivan E. de Araujo; Ranier Gutierrez; Miguel A. L. Nicolelis; Sidney A. Simon

2006-01-01

332

Model of mechanical wear based on Markov processes  

Microsoft Academic Search

1.An analytical expression was obtained for the distribution of the working life for mechanical wear; the parameters of the distribution have specific physical significance and are determined by a special experiment.2.The diffusional distribution of the life, as shown by preliminary estimates, does not disagree with experimental data and, together with other distributions, may be used for the treatment of statistical

V. P. Strel'nikov; V. G. Tatsii

1977-01-01

333

Maternity: Neural Mechanisms, Motivational Processes, and Physiological Adaptations  

Microsoft Academic Search

This review focuses on research on both the neural substrate of maternal responsiveness and on the physiological, behavioral, and motivational adaptations to the maternal state. The female's response to her young is presented as a model motivational system and the mechanisms and neural circuitry through which the medial preoptic area regulates this responsivity is described. This analysis is then used

Michael Numan; Barbara Woodside

2010-01-01

334

Evaluating the Learning Process of Mechanical CAD Students  

ERIC Educational Resources Information Center

|There is little theoretical or experimental research on how beginner-level trainees learn CAD skills in formal training sessions. This work presents findings on how trainees develop their skills in utilizing a solid mechanical CAD tool (Pro/Engineer version 2000i[squared] and later version Wildfire). Exercises at the beginner and intermediate…

Hamade, R. F.; Artail, H. A.; Jaber, M. Y.

2007-01-01

335

Dynamic Processes in a Spheroidal Seismic-Damping Mechanism  

Microsoft Academic Search

A mathematical model of a variable-structure system of solids with rolling friction and unilateral sliding friction bonds is described. The model can be applied to seismic isolation mechanisms. Conditions for transition between the possible structures of the equations of state are formulated. The behavior of the system with kinematically defined motion of the base is analyzed as an example

E. Ya. Antonyuk; N. P. Plakhtienko

2005-01-01

336

Use of Avoidance Responses to Keep Spider Crabs Out of Traps for American Lobsters  

Microsoft Academic Search

Spider crabs Libinia spp. are a problem when caught in lobster traps because they have no market value, consume bait, occupy space in the trap, and increase trap-processing time. We conducted fishing experiments in which freshly crushed spider crabs were added to the bait in lobster traps. This treatment significantly reduced the catch of spider crabs compared to traps which

R. Anne Richards; J. Stanley Cobb

1987-01-01

337

Natural mechanisms protecting against cancer  

Microsoft Academic Search

Carcinogenesis is a multistage process. At each step of this process, there are natural mechanisms protecting against development of cancer. The majority of cancers in humans is induced by carcinogenic factors present in our environment including our food. However, some natural substances present in our diet or synthesized in our cells are able to block, trap or decompose reactive oxygen

Marek Jakóbisiak; Witold Lasek; Jakub Go?

2003-01-01

338

Steam-trap capacities  

SciTech Connect

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 maximum performance from the trapped equipment. The author notes that it is no coincidence that heating and ventilating engineers tend to use float-and-thermostative types of traps in large numbers, or that vendors of steam-heated equipment often specify inverted-bucket traps for use on their equipment. They may keep the equipment drained and operating at maximum capacity.

Monroe, E.S.

1985-04-15

339

Steam Trap Users' Guide.  

National Technical Information Service (NTIS)

Steam traps are an important element in the efficient operation of a steam system and in energy conservation. The high cost of producing and delivering steam mandates an effective steam trap inspection and maintenance program at all applicable naval activ...

D. M. Sneed J. C. King

1985-01-01

340

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

341

Polishing Characteristics of Hydrophilic Pad in Chemical Mechanical Polishing Process  

Microsoft Academic Search

This paper presents a hydrophilic chemical–mechanical polishing pad that uses a submicron graphite-particle impregnated polyurethane matrix to enhance slurry absorption. We investigated pads containing four different graphite contents of 0, 5, 15, and 25 wt%. Two diamond disks, one brazed, and one polycrystalline, were used to dress the polishing pads to create slurry supply and removal channels. The hydrophilic pad's contact

Ming-Yi Tsai; Chiou-Yuan Chen; Ying-Rong He

2011-01-01

342

Polishing Characteristics of Hydrophilic Pad in Chemical Mechanical Polishing Process  

Microsoft Academic Search

This article presents a hydrophilic chemical-mechanical polishing pad that uses a submicron graphite-particle impregnated polyurethane matrix to enhance slurry absorption. We investigated pads containing four different graphite contents of 0, 5, 15, and 25 wt%. Two diamond disks, one brazed, and one polycrystalline, were used to dress the polishing pads to create slurry supply and removal channels. The hydrophilic pad's contact

Ming-Yi Tsai; Chiou-Yuan Chen; Ying-Rong He

2012-01-01

343

Feshbach resonance cooling of trapped atom pairs  

SciTech Connect

Spectroscopic studies of few-body systems at ultracold temperatures provide valuable information that often cannot be extracted in a hot environment. Considering a pair of atoms, we propose a cooling mechanism that makes use of a scattering Feshbach resonance. Application of a series of time-dependent magnetic field ramps results in either zero, one, or two atoms remaining trapped. If two atoms remain in the trap after the field ramps are completed, then they have been cooled. Application of the proposed cooling mechanism to optical traps or lattices is considered.

Dunn, Josh W.; Borca, Bogdan; Greene, Chris H. [Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States); Blume, D. [Department of Physics, Washington State University, Pullman, Washington 99164-2814 (United States); Granger, B.E. [Department of Physics, Santa Clara University, Santa Clara, California 95053 (United States)

2005-03-01

344

Processing and mechanical properties of hydroxyapatite reinforced with hydroxyapatite whiskers.  

PubMed

Hydrothermally synthesized HAp fine crystals/HAp whiskers mixtures have been used for the preparation of HAp/0-30% (whiskers) composites. The composites have been fabricated by pressureless sintering and hot-pressing. The best mechanical properties and the highest densities have been achieved for composites hot pressed at 1000 degrees C (2 h, 30 MPa in flowing Ar). Their density was in the range of 90-97% of the theoretical density. Fracture toughness (Klc) of the composites reflected their microstructure and had the value of 1.4 MPa m1/2 (as compared with Klc = 1.0 MPa m1/2 for the non-reinforced HAp matrix). Compressive prestressing of the HAp matrix and crack deflection (both derived from the residual stress field) contributed to the increase of fracture toughness. Other toughening mechanisms have not been observed. HAp/HAp (whiskers) composites exhibited improved toughness without degradation of biocompatibility, because the HAp whiskers acted both as a reinforcement and as a biocompatible phase. Problems related to biocompatibility and mechanical properties of available HAp-based composites were also discussed. PMID:8866034

Suchanek, W; Yashima, M; Kakihana, M; Yoshimura, M

1996-09-01

345

Hydrodynamic Trap for Single Cells and Particles  

NASA Astrophysics Data System (ADS)

The ability to trap individual particles, cells and macromolecules has revolutionized many fields of science during the last two decades. Several methods of particle trapping and micromanipulation have been developed based on optical, magnetic and electric fields. In this work, we describe an alternative trapping method, the hydrodynamic trap, based on the sole action of hydrodynamic forces in a microfluidic device. A microfluidic cross slot device is fabricated consisting of two perpendicular microchannels where opposing laminar flow streams converge. In this device, a purely extensional flow field is created at the microchannel junction, thereby resulting in a semi-stable potential well at the stagnation point which enables particle trapping. We implement an automated feedback-control mechanism to adjust the location of the stagnation point which facilitates active particle trapping. Using the hydrodynamic trap, we successfully demonstrate trapping and manipulation of single particles and cells for arbitrarily long observation times. This technique offers a new venue for observation of biological materials without surface immobilization, eliminates potentially perturbative optical, magnetic and electric fields, and provides the capability to change the surrounding medium conditions of the trapped object.

Tanyeri, Melikhan; Schroeder, Charles

2010-03-01

346

Thermo-mechanical phenomena in high speed continuous casting processes  

NASA Astrophysics Data System (ADS)

Thermo-mechanical phenomena during continuous thin slab casting have been studied with the objectives of understanding the mechanism of mold crack formation, and the effect of mold design upon the mechanical behavior of the stand. To achieve these goals, several finite element models have been developed in conjunction with a series of industrial plant trials. First, an investigation of mold crack formation in thin slab casting was undertaken to elucidate the mechanism by which cracks develop and to evaluate possible solutions to the problem. Three-dimensional finite-element thermal-stress models were developed to predict temperature, distortion, and residual stress in thin-slab casting molds, comparing funnel-shaped to parallel molds. Mold wall temperatures were obtained from POSCO in Korea and analyzed to determine the corresponding heat-flux profiles in thin-slab molds. This data was utilized in an elastic-visco-plastic analysis to investigate the deformation of the molds in service for the two different mold shapes. The results of a metallurgical investigation of mold samples containing cracks were used together with the results of the mathematical models, to determine mechanisms and to suggest solutions for the formation of mold cracks. Large cyclic inelastic strains were found in the funnel transition region just below the meniscus, due to the slightly higher temperature at that location. The cracks appear to have propagated by thermal fatigue caused by major level fluctuations. Next, two-dimensional thermo-elastic-visco-plastic analysis was performed for a horizontal slice of the solidifying strand, which moves vertically down the mold during casting. The model calculates the temperature distributions, the stresses and the strains in the solidifying shell, and the air gap between the casting mold and the solidifying strand. Model predictions were verified with an analytical solution and plant trials that were carried out during billet casting at POSCO. The validated model from the billet study was next applied to thin slab casting, using mold temperature and distortion data from the mold cracking study. An investigation of the effect of mold taper on the shrinkage of the solidifying shell, its gap formation, and stress evolution was carved out for different thin slab mold geometries. The model predicts that the shell in funnel molds develops a tensile stress at the slab surface in the funnel transition region due to funnel retraction. This model also suggests that as the funnel depth increases, the possibility of surface cracks at the funnel outside bed position increases.

Park, Joong Kil

347

Evolutionary psychology: counting babies or studying information-processing mechanisms.  

PubMed

Evolutionary psychology focuses on the study of adaptations. Its practitioners put little credence in the study of reproductive success in recent and current environments, and argue for an information-processing, cost-benefit conception of adaptation. Because ancestral and current environments differ, it is necessary to distinguish between innate and operational adaptations and between concurrently contingent and developmentally contingent behaviors. These distinctions lead to an evolutionary classification of behaviors into true pathologies, pseudopathologies, quasinormal behaviors, and adaptive-culturally-variable behaviors. I argue that a complete study of the functioning of a behavioral adaptation involves modeling ancestral selection pressures, cross-cultural research, experimental studies of mental processes, and studies of the proximate biological correlates of information-processing adaptations. Finally, I claim that evolutionary psychology can help us avoid making both naturalistic and moralistic fallacies. PMID:10818618

Crawford, C

2000-04-01

348

Unusual corrosion process of gold nanoplates and the mechanism study  

NASA Astrophysics Data System (ADS)

Herein we describe an unusual localized corrosion that initiates on large {111} surfaces and ends with the complete fragmentation of the gold nanoplates, which is expected to develop into a specific method for processing large metal nanomaterials into smaller ones with desired shapes.Herein we describe an unusual localized corrosion that initiates on large {111} surfaces and ends with the complete fragmentation of the gold nanoplates, which is expected to develop into a specific method for processing large metal nanomaterials into smaller ones with desired shapes. Electronic Supplementary Information (ESI) available: Additional experimental details and TEM images. See DOI: 10.1039/b9nr00229d/

Cheng, Yingwen; Qiu, Cuicui; Ma, Houyi; Zhang, Xiaokai; Gu, Xiaohu

2010-05-01

349

Enterobacter cloacae as biosurfactant producing bacterium: differentiating its effects on interfacial tension and wettability alteration Mechanisms for oil recovery during MEOR process.  

PubMed

Microbial enhanced oil recovery (MEOR) process utilizes microorganisms or their metabolites to mobilize the trapped oil in the oil formation after primary and secondary oil recovery stages. MEOR technique is considered as more environmentally friendly and low cost process. There are several identified mechanisms for more oil recovery using MEOR processes however; wettability alteration and interfacial tension (IFT) reduction are the important ones. Enterobacter Cloacae, a facultative bio-surfactant producer bacterium, was selected as a bacterial formulation due to its known performance on IFT reduction and wettability alteration. To quantify the effects of these two mechanisms, different tests including oil spreading, in situ and ex situ core flooding, wettability measurement (Amott), IFT, viscosity and pH measurements were performed. The obtained results revealed that the experimental procedure used in this study was able to quantitatively identify the individual effects of both mechanisms on the ultimate microbial oil recovery. The results demonstrated considerable effects of both mechanisms on the tertiary oil recovery; however after a proper shut in time period, more tertiary oil was recovered because of wettability alteration mechanism. Finally, SEM images taken from the treated cores showed biofilm formation on the rock pore surfaces, which is responsible for rock surface wettability alteration. PMID:23376749

Sarafzadeh, Pegah; Hezave, Ali Zeinolabedini; Ravanbakhsh, Moosa; Niazi, Ali; Ayatollahi, Shahab

2013-01-05

350

A new hummingbird trap  

Microsoft Academic Search

New capturing methods are constantly developed to optimize field work efforts in scientific research. This paper describes the design and construction of a new hummingbird trap, called the Ruschi net trap. It consists of a circular screen lid attached to a frame and a cylindrical screen bag that is manually pulled to trap the hummingbird while it is feeding. The

Piero A. Ruschi

351

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

352

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

353

Simulations on Resistive Cooling of Trapped Highly-Charged Particles  

SciTech Connect

The increasing demand for high accuracies in atomic physics experiments requires intense beams of heavy and highly charged ions (HCI) which must be decelerated and cooled to extremely low energies. In the upcoming HITRAP (Highly charged Ion Trap) facility at GSI, Darmstadt HCI will be trapped and resistively cooled thanks to the electronic dissipation of kinetic energy on an external impedance. The cooling mechanism becomes highly nonlinear when applied to large ensembles of particles and due to the lack of thorough theoretical and experimental investigations the understanding of the process is still very limited. Our Particle-In-Cell simulations show the feasibility of this cooling mechanism and reveal some of its characteristic features.

Maero, G. [Gesellschaft fuer Schwerionenforschung mbH, Planckstrasse 1, 64291 Darmstadt (Germany); Dipartimento di Fisica, Universita degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Herfurth, F.; Kluge, H.-J.; Koszudowski, S.; Quint, W. [Gesellschaft fuer Schwerionenforschung mbH, Planckstrasse 1, 64291 Darmstadt (Germany); Kester, O.; Schwarz, S. [National Superconducting Cyclotron Laboratory, Michigan State University, 1 Cyclotron, East Lansing, MI 48824-1321 (United States)

2010-06-16

354

Unusual corrosion process of gold nanoplates and the mechanism study  

Microsoft Academic Search

Herein we describe an unusual localized corrosion that initiates on large {111} surfaces and ends with the complete fragmentation of the gold nanoplates, which is expected to develop into a specific method for processing large metal nanomaterials into smaller ones with desired shapes.Herein we describe an unusual localized corrosion that initiates on large {111} surfaces and ends with the complete

Yingwen Cheng; Cuicui Qiu; Houyi Ma; Xiaokai Zhang; Xiaohu Gu

2010-01-01

355

Unusual corrosion process of gold nanoplates and the mechanism study.  

PubMed

Herein we describe an unusual localized corrosion that initiates on large {111} surfaces and ends with the complete fragmentation of the gold nanoplates, which is expected to develop into a specific method for processing large metal nanomaterials into smaller ones with desired shapes. PMID:20648310

Cheng, Yingwen; Qiu, Cuicui; Ma, Houyi; Zhang, Xiaokai; Gu, Xiaohu

2010-02-17

356

Electrical, chemical and mechanical processes in water treeing  

Microsoft Academic Search

Water treeing is a complex phenomenon involving several processes with many synergistic effects. Although a huge number of papers on the subject have been published over the last 25 years, there is no comprehensive theory able to describe the often contradictory experimental results. However, there are some tendencies that are always observed, whatever the experimental conditions. A critical review of

Jean-Pierre Crine

1998-01-01

357

Mechanism of silk processing in insects and spiders  

Microsoft Academic Search

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

Hyoung-Joon Jin; David L. Kaplan

2003-01-01

358

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

359

A study on irregular growing defect mechanism and removal process  

NASA Astrophysics Data System (ADS)

Main Topics of a photomask have been CD(Critical Dimension), Overlay and Defects. In side of defects, technique suppressing growing defects which are occurring on a mask surface becomes as important as defect control method during mask manufacturing process. Conventional growing defects arise out of combination of sulfuric ion on a mask surface and environmental facts such as pellicle ingredient, humidity and etc. So Mask cleaning process was driven to reduce sulfuric acid on a mask surface which source of growing defects. And actually various cleaning process has been developed through the elimination of sulfuric acid such as DI, O3 cleaning. Normally Conventional growing defects are removed using DI, SC1 or SPM cleaning according to incidence. But recently irregular growing defects are occurred which are completely distinct from conventional growing defects. Interestingly, irregular growing defects are distributed differently from conventional on a mask. They spread in isolated space patterns and reduce the transmittance so that space pattern size continuously decreased. It causes Wafer Yield loss. Furthermore, irregular growing defects are not fully removed by cleaning which is traditional removal process. In this study, we provide difference between conventional and irregular growing defects based on its characteristic and distributed formation. In addition, we present and discuss removal and control technique about irregular growing defects. For elemental analysis and study, diverse analysis tool was applied such as TEM for checking Cross-Section, AFM for checking the roughness of surface, EDAX, AES, IC for analyzing remained ions and particles on the mask and AIMS.

Lee, Hyemi; Jun, Jeayoung; Jeong, Goomin; Kim, Sangchul; Kim, Sangpyo; Kim, Changreol

2011-10-01

360

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

361

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

362

Processing, microstructure and mechanical behavior of nanocomposite multilayers  

NASA Astrophysics Data System (ADS)

Nanoscale multilayer coatings have high potential for numerous engineering applications because they can combine different properties from individual components. At present, scale effects on the mechanical behavior of multilayers are not well understood. Three multilayer systems, namely Al/Al 2O3, Ti/TiN, and Cr/a-C, have been synthesized by using a dual-gun e-beam physical vapor deposition, to investigate the relationship between the nature of components, their microstructures, and mechanical behavior. The deposited Al and Ti nanolayers were found to have polycrystalline fcc and hcp structure, respectively, the Cr and TiN layers had fine columnar bcc and fcc structure, respectively, and the Al2O3 and C layers were amorphous. Nanoscale effects were observed in all three systems with the metal layer thickness affecting significantly the mechanical behavior. The hardness response of the present systems can be described as a function of the metal layer thickness by a Hall-Petch relationship. A critical Al layer thickness of 40 nm, below which there was no further hardness enhancement, was found for the Al/Al2O3 multilayers. The critical Al layer thickness could be predicted by previous theoretical models. A hardness increase was observed down to a Ti layer thickness of 5 nm for the Ti/TiN system. The strengthening of the Ti/TiN multilayers was consistent with the macroyield maps based on a confined layer slip model. Hardness in the Cr/ a-C system showed a continuous increase down to a Cr layer thickness of 20 nm. The fracture toughness of the ceramic was significantly improved by introducing a metal/ceramic multilayered structure. The wear behavior of the present multilayers was mainly controlled by the ceramic phase. The Cr/ a-C multilayers achieved a low friction coefficient (˜0.1) and low wear rate (˜10-5 mm3/N m).

Qi, Zuqiang

363

Atomic mechanism of vitrification process in simple monatomic nanoparticles?  

Microsoft Academic Search

.  \\u000a Glass formation in simple monatomic nanoparticles has been studied by\\u000a molecular dynamics simulations in spherical model with a free surface.\\u000a Models have been obtained by cooling from the melt toward glassy state.\\u000a Atomic mechanism of glass formation was monitored via spatio-temporal\\u000a arrangement of solid-like and liquid-like atoms in nanoparticles. We use\\u000a Lindemann freezing-like criterion for identification of solid-like atoms

V. V. Hoang

2011-01-01

364

Entangled States of Trapped Ions  

NASA Astrophysics Data System (ADS)

Entangled states of the internal degrees of freedom are an important resource in Quantum Information Processing (QIP) and Quantum Simulation (QS) with trapped ions. Most basic requirements for QIP and QS have been demonstrated for trapped ions, with two big challenges remaining: Improving operation fidelity and scaling up to larger numbers of qubits. In the last few years, steady progress has been achieved with laser-based entanglement schemes with demonstrated fidelities of deterministically produced Bell states of 99.3% and up to 14 ion-qubits entangled in generalized GHZ-states. Scalable architectures have been proposed; one scheme, where ion-qubits are moved through a multi-zone trap array, is studied in several laboratories. Sympathetic cooling with a second ion species, which initializes the motional states for multi-qubit operations, has been demonstrated in an experiment where arbitrary operations on two qubits were implemented. Micro-fabrication approaches to ion-trap-arrays have yielded structures that should be capable of holding and manipulating large numbers of ions. Recently, with the use of microwaves, single-qubit rotations with fidelities of 99.998% per gate operation were demonstrated and two ion-qubit gates have been implemented. Microwave control could potentially be easier to scale by directly integrating microwave-lines on micro-fabricated trap devices. It also eliminates several sources of decoherence that are present in laser-based schemes by exclusively coupling to long lived hyperfine ground states.

Leibfried, Dietrich

2012-02-01

365

Contribution of inflammatory processes to Alzheimer's disease: molecular mechanisms.  

PubMed

There is compelling evidence that Alzheimer's disease (AD) amyloid-beta (Abeta) deposition is associated with a local inflammatory response, which is initiated by the activation of microglia and the recruitment of astrocytes. These cells secrete a number of cytokines and neurotoxic products that may contribute to neuronal degeneration and cell death. It has been documented that long-term intake of non-steroidal anti-inflammatory drugs (NSAIDs) decrease the risk for developing AD and delay the onset of the disease. The mechanism behind these NSAIDs is still controversial and several hypotheses have been raised, including changes in the amyloid precursor protein (APP) metabolism, in Abeta aggregation and a decrease in inflammatory mediators. Recently, it was proposed that some NSAIDs might activate the peroxisome proliferator-activated receptor-gamma (PPAR-gamma). PPAR-gamma belongs to a family of nuclear receptors that are able to regulate the transcription of pro-inflammatory molecules, such as iNOS. The activation of PPAR-gamma has been recently reported to reduce Abeta levels in cell culture and AD animal models. The implication of PPAR-gamma in the control of Abeta-induced inflammation suggests a new target for AD therapy and emphasize the contribution of neuroinflammatory mechanisms to the pathogenesis of AD. PMID:16472958

Sastre, Magdalena; Klockgether, Thomas; Heneka, Michael T

2006-02-10

366

Mechanical signature analysis using time-frequency signal processing: application to internal combustion engine knock detection  

Microsoft Academic Search

Signature analysis consists of the extraction of information from measured signal patterns. The work presented in this paper illustrates the use of time-frequency (TF) analysis methods for the purpose of mechanical signature analysis. Mechanical signature analysis is a mature and developed field; however, TF analysis methods are relatively new to the field of mechanical signal processing, having mostly been developed

B. Samimy; G. Rizzoni

1996-01-01

367

A Case for Kernel Level Implementation of Inter Process Communication Mechanisms  

Microsoft Academic Search

Distributed systems must provide some kind of inter process communication (IPC) mechanisms to enable communication between local and especially geographically dispersed and physically distributed processes. These mechanisms may be implemented at different levels of distributed systems namely at application level, library level, operating system interface level, or kernel level. Upper level implementations are intuitively simpler to develop but are less

Seyedeh Leili Mirtaheri; Ehsan Mousavi Khaneghah; Mohsen Sharifi

2008-01-01

368

The effect of thermal processing on microstructure and mechanical properties in a nickel-iron alloy  

Microsoft Academic Search

The correlation between processing conditions, resulted microstructure and mechanical properties is of interest in the field of metallurgy for centuries. In this work, we investigated the effect of thermal processing parameters on microstructure, and key mechanical properties to turbine rotor design: tensile yield strength and crack growth resistance, for a nickel-iron based superalloy Inconel 706. The first step of the

Ling Yang

2007-01-01

369

Neurobehavioral Mechanisms of Temporal Processing Deficits in Parkinson's Disease  

PubMed Central

Background Parkinson's disease (PD) disrupts temporal processing, but the neuronal sources of deficits and their response to dopamine (DA) therapy are not understood. Though the striatum and DA transmission are thought to be essential for timekeeping, potential working memory (WM) and executive problems could also disrupt timing. Methodology/Findings The present study addressed these issues by testing controls and PD volunteers ‘on’ and ‘off’ DA therapy as they underwent fMRI while performing a time-perception task. To distinguish systems associated with abnormalities in temporal and non-temporal processes, we separated brain activity during encoding and decision-making phases of a trial. Whereas both phases involved timekeeping, the encoding and decision phases emphasized WM and executive processes, respectively. The methods enabled exploration of both the amplitude and temporal dynamics of neural activity. First, we found that time-perception deficits were associated with striatal, cortical, and cerebellar dysfunction. Unlike studies of timed movement, our results could not be attributed to traditional roles of the striatum and cerebellum in movement. Second, for the first time we identified temporal and non-temporal sources of impaired time perception. Striatal dysfunction was found during both phases consistent with its role in timekeeping. Activation was also abnormal in a WM network (middle-frontal and parietal cortex, lateral cerebellum) during encoding and a network that modulates executive and memory functions (parahippocampus, posterior cingulate) during decision making. Third, hypoactivation typified neuronal dysfunction in PD, but was sometimes characterized by abnormal temporal dynamics (e.g., lagged, prolonged) that were not due to longer response times. Finally, DA therapy did not alleviate timing deficits. Conclusions/Significance Our findings indicate that impaired timing in PD arises from nigrostriatal and mesocortical dysfunction in systems that mediate temporal and non-temporal control-processes. However, time perception impairments were not improved by DA treatment, likely due to inadequate restoration of neuronal activity and perhaps corticostriatal effective-connectivity.

Harrington, Deborah L.; Castillo, Gabriel N.; Greenberg, Paul A.; Song, David D.; Lessig, Stephanie; Lee, Roland R.; Rao, Stephen M.

2011-01-01

370

Silver-clad ? superconducting tapes fabricated by different mechanical processing  

Microsoft Academic Search

0953-2048\\/11\\/10\\/032\\/img10\\/silver composites were fabricated by drawing a silver tube packed with precursor powders into round wire and deforming the round wire into flat tapes by longitudinal rolling, transverse rolling and uniaxial pressing respectively. The resultant tapes were observed by optical microscopy to examine the superconductor core\\/silver interface. Short pieces were cut from the tapes and heat-treated by a thermomechanical process

Y. C. Guo; H. K. Liu; S. X. Dou; T. Kuroda; Y. Tanaka

1998-01-01

371

Processing and mechanical properties of HA\\/UHMWPE nanocomposites  

Microsoft Academic Search

A hydroxyapatite (HA) particulate reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposite was fabricated by compounding HA and UHMWPE mixtures in paraffin oil using twin-screw extrusion and then compression molding. Scanning electron microscope images revealed that HA aggregates were broken down to nano-sized particles and homogeneously dispersed in UHMWPE by the combined processes of twin-screw extrusion and UHMWPE swelling treatment. Transmission

Liming Fang; Yang Leng; Ping Gao

2006-01-01

372

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

373

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

374

Molecular mechanisms of olfactory processing in the mammalian olfactory epithelium.  

PubMed

In humans the sense of smell plays an important role in protecting the organism from external hazards like fire, gas or spoiled food, in the consumption of food and in chemical communication with one another. Increasingly, the study of human olfaction is relevant to a number of medical problems connected with olfactory dysfunction, i.e. neurodegenerative diseases which are also manifested in the olfactory epithelium. Although much is known about behavioral aspects and neuronal activities elicited by odorants, we still cannot clearly describe the molecular mechanisms by which odor stimuli are transformed into an electrical cell signal. Here recent progress in our knowledge about the molecular elements of the transduction machinery are reviewed. It can help to understand the general principles underlying our sense of smell. PMID:8883103

Hatt, H

375

Predictive capacity of semi-empirical MNDO/PM3 and molecular mechanics MM2 estimations of the reactivity of cyclic nitrones as spin traps  

NASA Astrophysics Data System (ADS)

It is shown that the reactivity of nitrone compounds in spin trapping reactions (addition of short-lived free radicals to the nitrone double bond) can be predicted by means of not very complicated semi-empirical procedures simulating a hypothetical adsorption complex and its further transformation into spin adducts. Thus estimated reaction characteristics (the site of radical addition to a nitrone, stability of the resulting spin adduct, the effect of its geometry on hyperfine splitting constants in the EPR spectra of spin adducts) generally agree with the experimental data available on these nitrones.

Dultsev, F. N.; Dultseva, G. G.

2006-10-01

376

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

377

Development of Brain Mechanisms for Processing Orthographic and Phonologic Representations  

PubMed Central

Developmental differences in the neurocognitive networks for lexical processing were examined in 15 adults and 15 children (9- to 12-year-olds) using functional magnetic resonance imaging (fMRI). The lexical tasks involved spelling and rhyming judgments in either the visual or auditory modality. These lexical tasks were compared with nonlinguistic control tasks involving judgments of line patterns or tone sequences. The first main finding was that adults showed greater activation than children during the cross-modal lexical tasks in a region proposed to be involved in mapping between orthographic and phonologic representations. The visual rhyming task, which required conversion from orthography to phonology, produced greater activation for adults in the angular gyrus. The auditory spelling task, which required the conversion from phonology to orthography, also produced greater activation for adults in the angular gyrus. The greater activation for adults suggests they may have a more elaborated posterior heteromodal system for mapping between representational systems. The second main finding was that adults showed greater activation than children during the intra-modal lexical tasks in the angular gyrus. The visual spelling and auditory rhyming did not require conversion between orthography and phonology for correct performance but the adults showed greater activation in a system implicated for this mapping. The greater activation for adults suggests that they have more interactive convergence between representational systems during lexical processing.

Booth, James R.; Burman, Douglas D.; Meyer, Joel R.; Gitelman, Darren R.; Parrish, Todd B.; Mesulam, M. Marsel

2005-01-01

378

Investigation of material removal mechanism of silicon wafer in the chemical mechanical polishing process using molecular dynamics simulation method  

Microsoft Academic Search

Chemical mechanical polishing (CMP) technology, being the mainstream technique of acquiring global planarization and nanometer\\u000a level surface, has already become an attractive research item. In the case of CMP process, the indentation depth lies in the\\u000a range of nanometer or sub-nanometer, huge hydrostatic pressure induced in the local deformation area which makes the material\\u000a removal and surface generation process different

Xuesong Han; Yuanzhong Hu; Siyuan Yu

2009-01-01

379

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

380

Atomic mechanism of vitrification process in simple monatomic nanoparticles *  

NASA Astrophysics Data System (ADS)

Glass formation in simple monatomic nanoparticles has been studied by molecular dynamics simulations in spherical model with a free surface. Models have been obtained by cooling from the melt toward glassy state. Atomic mechanism of glass formation was monitored via spatio-temporal arrangement of solid-like and liquid-like atoms in nanoparticles. We use Lindemann freezing-like criterion for identification of solid-like atoms which occur randomly in supercooled region. Their number grows intensively with decreasing temperature and they form clusters. Subsequently, single percolation solid-like cluster occurs at temperature above the glass transition. Glass transition occurs when atoms aggregated into this single percolation cluster are in majority in the system to form relatively rigid glassy state. Solid-like domain is forming in the center of nanoparticles and grows outward to the surface. We found temperature dependence of potential energy, mean-squared displacement (MSD) of atoms, diffusion constant, incoherent intermediate scattering function, radial distribution function (RDF), local bond-pair orders detected by Honeycutt-Andersen analysis, radial density profile and radial atomic displacement distributions in nanoparticles. We found that liquid-like atoms in models obtained below glass transition have a tendency to concentrate in the surface layer of nanoparticles. However, they do not form a purely liquid-like surface layer coated nanoparticles.

Hoang, V. V.

2011-02-01

381

Thermal and field dependencies of latent relaxation processes in irradiated MOS devices  

Microsoft Academic Search

Latent interface trap buildup, latent positive charge annealing, and molecular hydrogen annealing response of irradiated MOSFET were studied. The mechanisms of latent process and latent processes implications for hardness assurance are discussed

V. V. Emelianov; A. V. Sogoyan; S. V. Cherepko; O. V. Meshurov; V. N. Ulimov; A. I. Chumakov; V. I. Rogov; A. Y. Nikiforov

1997-01-01

382

Quantum mechanics can be formulated as a non-Markovian stochastic process  

NASA Astrophysics Data System (ADS)

Both quantum mechanics and stochastic-process theory deal with dynamical systems the behaviors of which can be predicted only probabilistically. It is shown here that the measurable behavior of an elementary quantum system can be modeled as a non-Markovian stochastic process. The conclusion that quantum behavior can generally be modeled as a real stochastic process eliminates some mysterious characteristics of quantum mechanics when viewed in Copenhagen-interpretation terms.

Skorobogatov, German A.; Svertilov, Sergey I.

1998-11-01

383

Neural mechanisms for processing binocular information II. Complex cells.  

PubMed

Complex cells in the striate cortex exhibit extensive spatiotemporal nonlinearities, presumably due to a convergence of various subunits. Because these subunits essentially determine many aspects of a complex cell receptive field (RF), such as tuning for orientation, spatial frequency, and binocular disparity, examination of the RF properties of subunits is important for understanding functional roles of complex cells. Although monocular aspects of these subunits have been studied, little is known about their binocular properties. Using a sophisticated RF mapping technique that employs binary m-sequences, we have examined binocular interactions exhibited by complex cells in the cat's striate cortex and the binocular RF properties of their underlying functional subunits. We find that binocular interaction RFs of complex cells exhibit subregions that are elongated along the frontoparallel axis at different binocular disparities. Therefore responses of complex cells are largely independent of monocular stimulus position or phase as long as the binocular disparity of the stimulus is kept constant. The binocular interaction RF is well described by a sum of binocular interaction RFs of underlying functional subunits, which exhibit simple cell-like RFs and a preference for different monocular phases but the same binocular disparity. For more than half of the complex cells examined, subunits of each cell are consistent with the characteristics specified by an energy model, with respect to the number of subunits as well as relationships between the subunit properties. Subunits exhibit RF binocular disparities that are largely consistent with a phase mechanism for encoding binocular disparity. These results indicate that binocular interactions of complex cells are derived from simple cell-like subunits, which exhibit multiplicative binocular interactions. Therefore binocular interactions of complex cells are also multiplicative. This suggests that complex cells compute something analogous to an interocular cross-correlation of images for a local region of visual space. The result of this computation can be used for solving the stereo correspondence problem. PMID:10444686

Anzai, A; Ohzawa, I; Freeman, R D

1999-08-01

384

Effect on Two-Step Polishing Process of Electrochemical Mechanical Planarization and Chemical-Mechanical Planarization on Planarization  

NASA Astrophysics Data System (ADS)

Chemical-mechanical planarization (CMP) is a technique used for planarizing an overburden film in the fabrication of semiconductor devices by chemical treatment and mechanical abrasion. However, a variety of defects such as dishing of metal interconnects, erosion, delamination, and metal layer peeling are generated by a high down force in CMP. A high down force is required to generate a high material removal rate (MRR), which results in greater defects. To minimize these defects, a new planarization process is used, known as electrochemical mechanical planarization (ECMP), which requires electrochemical and mechanical energies. ECMP first involves using an electrochemical reaction to change the surface on the target material into a passivation film. Then, the passivation film is worn down using a polishing pad or abrasives on the contacted areas of the metal film with the polishing pad under a low down force. The electrochemical energy dissolves the copper solid into copper ions in an aqueous electrolyte on the contacted areas of the metal film and the polishing pad. Therefore, the low-down-force ECMP reduces the defects such as dishing, erosion, delamination and metal layer peeling to a greater degree than a conventional high-down-force CMP. Also, the MRR of the ECMP process is higher than that of the low-down-force CMP process because the MRR of the ECMP process is proportional to current density. However, some residual metal between the dielectric material was generated through the use of a nonconductive polishing pad in the ECMP process. Therefore, the CMP process is required for the final process to remove residual metals. In this research, we investigated a two-step polishing method that consists of ECMP with a nonconductive polishing pad and a conventional CMP process to planarize a micro-patterned wafer for microelectromechanical systems (MEMS). First, the ECMP process using a nonconductive polishing pad removed several tens of micrometers (?m) of bulk copper on the patterned wafer over a shorter process time than the copper CMP process only. Then, the residual copper was completely removed through the low-down-force copper CMP process. The total process time and the amount of dishing defects were reduced by applying the two-step polishing method.

Jeong, Sukhoon; Joo, Sukbae; Kim, Hyoungjae; Kim, Sungryul; Jeong, Haedo

2009-06-01

385

Increased oxidative stress brought on by pro-inflammatory cytokines in neurodegenerative processes and the protective role of nitrone-based free radical traps  

Microsoft Academic Search

Nitrone-based free radical traps (NFTs) have been shown to be protective in several neurodegenerative models. Our research has strongly implicated that: A) several neurodegenerative conditions exhibit increased levels of pro-inflammatory cytokines which consequently result in increased levels of oxidative stress and B) that NFTs act in part by suppressing oxidative stress through suppression of the action of the cytokine cascade.

R. A. Floyd; K. Hensley; F. Jaffery; L. Maidt; K. Robinson; Q. Pye; C. Stewart

1999-01-01

386

What mechanisms/processes underlie radiation-induced genomic instability?  

PubMed

Radiation-induced genomic instability is a modification of the cell genome found in the progeny of irradiated somatic and germ cells but that is not confined on the initial radiation-induced damage and may occur de novo many generations after irradiation. Genomic instability in the germ line does not follow Mendelian segregation and may have unpredictable outcomes in every succeeding generation. This phenomenon, for which there is extensive experimental data and some evidence in human populations exposed to ionising radiation, is not taken into account in health risk assessments. It poses an unknown morbidity/mortality burden. Based on experimental data derived over the last 20 years (up to January 2012) six mechanistic explanations for the phenomenon have been proposed in the peer-reviewed literature. This article compares these hypotheses with the empirical data to test their fitness to explain the phenomenon. As a conclusion, the most convincing explanation of radiation-induced genomic instability attributes it to an irreversible regulatory change in the dynamic interaction network of the cellular gene products, as a response to non-specific molecular damage, thus entailing the rejection of the machine metaphor for the cell in favour of one appropriate to a complex dissipative dynamic system, such as a whirlpool. It is concluded that in order to evaluate the likely morbidity/mortality associated with radiation-induced genomic instability, it will be necessary to study the damage to processes by radiation rather than damage to molecules. PMID:22955377

Karotki, Andrei V; Baverstock, Keith

2012-09-06

387

Dynamical mechanisms of odor processing in olfactory bulb mitral cells.  

PubMed

In the olfactory system, the contribution of dynamical properties such as neuronal oscillations and spike synchronization to the representation of odor stimuli is a matter of substantial debate. While relatively simple computational models have sufficed to guide current research in large-scale network dynamics, less attention has been paid to modeling the membrane dynamics in bulbar neurons that may be equally essential to sensory processing. We here present a reduced, conductance-based compartmental model of olfactory bulb mitral cells that exhibits the complex dynamical properties observed in these neurons. Specifically, model neurons exhibit intrinsic subthreshold oscillations with voltage-dependent frequencies that shape the timing of stimulus-evoked action potentials. These oscillations rely on a persistent sodium conductance, an inactivating potassium conductance, and a calcium-dependent potassium conductance and are reset via inhibitory input such as that delivered by periglomerular cell shunt inhibition. Mitral cells fire bursts, or clusters, of spikes when continuously stimulated. Burst properties depend critically on multiple currents, but a progressive deinactivation of I(A) over the course of a burst is an important regulator of burst termination. Each of these complex properties exhibits appropriate dynamics and pharmacology as determined by electrophysiological studies. Additionally, we propose that a second, inconsistently observed form of infrathreshold bistability in mitral cells may derive from the activation of ATP-activated potassium currents responding to hypoxic conditions. We discuss the integration of these cellular properties in the larger context of olfactory bulb network operations. PMID:16707721

Rubin, Daniel B; Cleland, Thomas A

2006-05-17

388

A comparison of monkey and human motion processing mechanisms.  

PubMed

Single-cell recording studies have provided vision scientists with a detailed understanding of motion processing at the neuronal level in non-human primates. However, despite the development of brain imaging techniques, it is not known to what extent the response characteristics of motion-sensitive neurons in monkey brain mirror those of human motion-sensitive neurons. Using a motion adaptation paradigm, the direction aftereffect, we recently provided evidence of a strong resemblance in the response functions of motion-sensitive neurons in monkey and human to moving dot patterns differing in dot density. Here we describe a series of experiments in which measurements of the direction aftereffect are used to infer the response characteristics of human motion-sensitive neurons when viewing transparent motion and moving patterns that differ in their signal-to-noise ratio (motion coherence). In the case of transparent motion stimuli, our data suggest suppressed activity of motion-sensitive neurons similar to that reported for macaque monkey. In the case of motion coherence, our results are indicative of a linear relationship between signal intensity (coherence) and neural activity; a pattern of activity which also bears a striking similarity to macaque neural activity. These findings strongly suggest that monkey and human motion-sensitive neurons exhibit similar response and inhibitory characteristics. PMID:20705083

Lynn, Catherine; Curran, William

2010-08-10

389

Immobilizing live bacteria for AFM imaging of cellular processes  

Microsoft Academic Search

Coccoid cells of the bacterial species Staphylococcus aureus have been mechanically trapped in lithographically patterned substrates and imaged under growth media using atomic force microscopy (AFM) in order to follow cellular processes. The cells are not perturbed as there is no chemical linkage to the surface. Confinement effects are minimized compared to trapping the cells in porous membranes or soft

L. Kailas; E. C. Ratcliffe; E. J. Hayhurst; M. G. Walker; S. J. Foster; J. K. Hobbs

2009-01-01

390

PATTERN AND PROCESS DEPENDENCIES IN COPPER DAMASCENE CHEMICAL MECHANICAL POLISHING PROCESSES  

Microsoft Academic Search

In this paper we present experimental data that shows the dependence of copper dishing and oxide ero- sion on pitch and pattern density, as well as on polishing process parameters including table speed, do wn force, and process sequence. Specifi cally, the data shows that the degree of dishing and erosion strongly depends on both the processing parameters and layout

T. Tugbawa; J. Yoon; D. Boning; J. Chung; R. Muralidhar; S. Hymes; Y. Gotkis; S. Alamgir; R. Walesa; L. Shumway; G. Wu; F. Zhang; R. Kistler; J. Hawkins

391

Processing and mechanical behavior of aluminium oxide microstructure composites  

NASA Astrophysics Data System (ADS)

We have proposed a new class of composites that accesses different component properties not through the use of distinct materials, but through the exploitation of the microstructure-property relationship within a single material. That is, we seek to adapt composite concepts to take advantage of the considerable variance in properties associated with different microstructures. This new class of composites is called microstructure composites. Microstructure composites are predominately single phase ceramics that utilize multiple distinct microstructure features in the same composite to obtain unique property combinations. Spatial control and composite connectivity of the individual microstructure components of a microstructure composite are ultimately the key to developing and controlling useful and unique properties. Microstructural features can be controlled via the starting location and transport of the dopants, minority second phases, and liquid phases that are used to manipulate microstructure development. This work focuses on textured-equiaxed microstructure in the Al2O 3 system. Texture is obtained in situ using templated grain growth (TGG). To control microstructure development locally during microstructure composite fabrication, it is important to use relatively low levels of dopant to mitigate the effects of dopant interdiffusion. Therefore, the development of texture in alpha-Al2O3 using TGG was explored under low liquid-phase dopant concentration conditions. High temperature dilatometry was performed to quantify the effect of template constraint on x-y plane shirinkage and the extent to which this constraint could be mitigated as a function of the dopant concentration. x-y plane shrinkage was observed to be increasingly constrained with increasing template loading and decreasing dopant concentration. Final x-y plane shrinkage was greater for samples with 0.14 wt% dopant than for those without dopant, despite have a much lower peak strain rate. It was concluded that densification was impeded by the dopant at lower temperatures but enhanced significantly above 1450°C. Texture is highly developed in samples with no dopant and 0.14 wt% dopant by 1550°C and in samples with 2 wt% dopant by 1350°C. We proposed a new class of composites (called microstructure composites) that accesses different component properties not through the use of distinct materials, but rather through the exploitation of the microstructure-property relationship within a single material. Microstructure composites, therefore, are single phase ceramics that combine components with distinct microstructures within a single composite to obtain unique property combinations. Spatial control and composite connectivity of the individual microstructural 'components' of a microstructure composite are ultimately the key to developing and controlling useful and unique properties. Microstructural components are developed by controlling the starting location and transport of dopants during processing and sintering. This work focuses on alpha-Al2O3 microstructure composites that combine textured components, developed in situ using templated grain growth (TGG), and fine-grained equiaxed components. To control microstructure development locally during composite fabrication, it is important to use relatively low levels of dopant to mitigate the effects of dopant interdiffusion. Therefore, the development of texture in alpha-Al 2O3 using low liquid-phase dopant concentrations was explored, with a focus on the effect of template constraint on texture plane shrinkage. High quality texture was obtained with just 0.14 wt% (SiO2 + CaO) dopant. Textured Al2O3 exhibited transgranular fracture, as well as lower strength and fracture toughness than the fine-grained equiaxed Al2O3. A processing strategy using tape casting was developed for the fabrication of textured-equiaxed Al2O3 microstructure composites with 2-2 connectivity. Dopants used to promote TGG (SiO2 + CaO) were included in the templated tapes and dopants used to prevent abnormal grain growth (MgO) were inclu

Pavlacka, Robert J.

392

Trap style influences wild pig behavior and trapping success  

USGS Publications Warehouse

Despite the efforts of many natural resource professionals, wild pig (Sus scrofa) populations are expanding in many areas of the world. Although many creative techniques for controlling pig populations are being explored, trapping has been and still is themost commonly usedmethod of population control formany public and private land managers. We conducted an observational study to examine the efficiency of 2 frequently used trap styles: a small, portable box-style trap and a larger, semi-permanent, corral-style trap.We used game cameras to examine patterns of trap entry by wild pigs around each style of trap, and we conducted a trapping session to compare trapping success between trap styles. Adult female and juvenile wild pigs entered both styles of trap more readily than did adult males, and adult males seemed particularly averse to entering box traps. Less than 10% of adult male visits to box traps resulted in entries, easily the least percentage of any class at any style of trap. Adult females entered corral traps approximately 2.2 times more often per visit than box traps and re-entered corral traps >2 times more frequently. Juveniles entered and reentered both box and corral traps at similar rates. Overall (all-class) entry-per-visit rates at corral traps (0.71) were nearly double that of box traps (0.37). Subsequent trapping data supported these preliminary entry data; the capture rate for corral traps was >4 times that of box traps. Our data suggest that corral traps are temporally and economically superior to box traps with respect to efficiency; that is, corral traps effectively trap more pigs per trap night at a lower cost per pig than do box traps. ?? 2011 The Wildlife Society.

Williams, B. L.; Holtfreter, R. W.; Ditchkoff, S. S.; Grand, J. B.

2011-01-01

393

Dissociable Brain Mechanisms for Processing Social Exclusion and Rule Violation  

PubMed Central

Social exclusion inherently involves an element of expectancy violation, in that we expect other people to follow the unwritten rule to include us in social interactions. In this functional magnetic resonance imaging (fMRI) study, we employed a unique modification of an interactive virtual ball-tossing game called “Cyberball” (Williams et al., 2000) and a novel paradigm called “Cybershape”, in which rules are broken in the absence of social exclusion, to dissociate brain regions that process social exclusion from rule violations more generally. Our Cyberball game employed an alternating block design and removed evoked responses to events when the participant was throwing the ball in inclusion to make this condition comparable to exclusion, where participants did not throw. With these modifications, we replicated prior findings of ventral anterior cingulate cortex (vACC), insula, and posterior cingulate cortex activity evoked by social exclusion relative to inclusion. We also identified exclusion-evoked activity in the hippocampi, left ventrolateral prefrontal cortex, and left middle temporal gyrus. Comparing social exclusion and rule violation revealed a functional dissociation in the active neural systems as well as differential functional connectivity with vACC. Some overlap was observed in regions differentially modulated by social exclusion and rule violation, including the vACC and lateral parietal cortex. These overlapping brain regions showed different activation during social exclusion compared to rule violation, each relative to fair play. Comparing activation patterns to social exclusion and rule violation allowed for the dissociation of brain regions involved in the experience of exclusion versus expectancy violation.

Bolling, Danielle Z.; Pitskel, Naomi B.; Deen, Ben; Crowley, Michael J.; McPartland, James C.; Mayes, Linda C.; Pelphrey, Kevin A.

2010-01-01

394

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

395

Microstructure evolution and mechanical properties of AA1100 aluminum sheet processed by accumulative roll bonding  

Microsoft Academic Search

In this study, accumulative roll bonding (ARB) process was carried out on an AA1100 aluminum sheet up to 10 cycles. Electron backscattering diffraction (EBSD) method was utilized to investigate the microstructural evolution during the ARB process. It was observed that the ARB is a promising process for fabricating ultra-fine grained structures in aluminum sheets. The results indicate that several mechanisms

H. Pirgazi; A. Akbarzadeh; R. Petrov; L. Kestens

2008-01-01

396

Processing of poly(lactic acid): Characterization of chemical structure, thermal stability and mechanical properties  

Microsoft Academic Search

The processing of poly(lactic acid) (injection and extrusion\\/injection) as well as annealing of processed materials were studied in order to analyze the variation of its chemical structure, thermal degradation and mechanical properties. Processing of PLA was responsible for a decrease in molecular weight, as determined by GPC, due to chain scission. The degree of crystallinity was evaluated by means of

F. Carrasco; P. Pagès; J. Gámez-Pérez; O. O. Santana; M. L. Maspoch

2010-01-01

397

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Preparation of Macroscopic Quantum-Interference States for a Collection of Trapped Ions Via a Single Geometric Operation  

NASA Astrophysics Data System (ADS)

We describe a scheme for the generation of macroscopic quantum-interference states for a collection of trapped ions by a single geometric phase operation. In the scheme the vibrational mode is displaced along a circle with the radius proportional to the number of ions in a certain ground electronic state. For a given interaction time, the vibrational mode returns to the original state, and the ionic system acquires a geometric phase proportional to the area of the circle, evolving from a coherent state to a superposition of two coherent states. The ions undergo no electronic transitions during the operation. Taking advantage of the inherent fault-tolerant feature of the geometric operation, our scheme is robust against decoherence.

Lin, Li-Hua

2010-05-01

398

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

399

Trapping in complex networks  

NASA Astrophysics Data System (ADS)

We investigate the trapping problem in Erd?s-Rényi (ER) and scale-free (SF) networks. We calculate the evolution of the particle density ?(t) of random walkers in the presence of one or multiple traps with concentration c. We show using theory and simulations that in ER networks, while for short times ?(t)~exp(-Act), for longer times ?(t) exhibits a more complex behavior, with explicit dependence on both the number of traps and the size of the network. In SF networks we reveal the significant impact of the trap's location: ?(t) is drastically different when a trap is placed on a random node compared to the case of the trap being on the node with the maximum connectivity. For the latter case we find ?(t) propto exp [-At/N?-2/?-1 langlekrangle] for all ?> 2, where ? is the exponent of the degree distribution P(k)~k- ?.

Kittas, A.; Carmi, S.; Havlin, S.; Argyrakis, P.

2008-11-01

400

Microfabricated ion trap array  

DOEpatents

A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.

Blain, Matthew G. (Albuquerque, NM); Fleming, James G. (Albuquerque, NM)

2006-12-26

401

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

402

Inexpensive, floating, insect-emergence trap  

SciTech Connect

The Environmental Sciences Division of Oak Ridge National Laboratory has been investigating the usefulness of aquarium microcosms and ponds for the quantification and predictions of toxicant effects on freshwater systems. Ideally, concepts and methods applicable to both 150-L microcosms and 15,000-L ponds would bridge the gap between the two. The effort of processing the benthic samples, as well as the destructiveness of the sampling in small ponds, limited the number of samples that could be taken. Therefore, the author developed an inexpensive emergence trap appropriate for use in small outdoor ponds, as one method of increasing sampling efficiency and economy. To prevent the possibility of trapping adults from adjacent ponds, which would confound the results, the traps had to be designed such that they could only trap insects from the ponds upon which they were floating. The design of this trap is described.

Cushman, R.M.

1983-11-01

403

Excitons in electrostatic traps  

Microsoft Academic Search

We consider in-plane electrostatic traps for indirect excitons in coupled quantum wells, where the traps are formed by a laterally modulated gate voltage. An intrinsic obstacle for exciton confinement in electrostatic traps is an in-plane electric field that can lead to exciton dissociation. We propose a design to suppress the in-plane electric field and, at the same time, to effectively

A. T. Hammack; N. A. Gippius; Sen Yang; G. O. Andreev; L. V. Butov; M. Hanson; A. C. Gossard

2006-01-01

404

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

405

Permanent magnetic trapping  

NASA Astrophysics Data System (ADS)

It is shown that the global nature of trapped particle motion in phase space makes it entirely plausible that particles with pitch angles near 90 deg are trapped for extremely long times, probably indefinitely. The long observed lifetimes of trapped particles can immediately be accounted for by this former population. For particles with low pitch angles an 'overstability' develops which serves to produce rapid variations in pitch angle and, presumably, random walk into the loss cone.

Michel, F. C.

1980-02-01

406

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

2012-11-14

407

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

408

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

409

Shaking-induced dynamics of cold atoms in magnetic traps  

NASA Astrophysics Data System (ADS)

We describe an experiment in which cold rubidium atoms, confined in an elongated magnetic trap, are excited by transverse oscillation of the trap center. The temperature after excitation exhibits resonance as a function of the driving frequency. We measure these resonances at several different trap frequencies. In order to interpret the experiments, we develop a simple model that incorporates both collisions between atoms and the anharmonicity of the real three-dimensional trapping potential. As well as providing a precise connection between the transverse harmonic oscillation frequency and the temperature resonance frequency, this model gives insight into the heating and loss mechanisms and into the dynamics of driven clouds of cold trapped atoms.

Llorente García, I.; Darquié, B.; Sinclair, C. D. J.; Curtis, E. A.; Tachikawa, M.; Hudson, J. J.; Hinds, E. A.

2013-10-01

410

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

411

45 CFR 205.35 - Mechanized claims processing and information retrieval systems; definitions.  

Code of Federal Regulations, 2011 CFR

...205.35 Mechanized claims processing and information retrieval systems; definitions. Section 205.35 through...plan requirements for an automated statewide management information system, conditions for FFP and...

2011-10-01

412

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

Code of Federal Regulations, 2012 CFR

... The provisions of this subpart are applicable to discharges resulting from the processing of blue crab in which mechanical picking or separation of crab meat from the shell is utilized. [40 FR 55780, Dec. 1,...

2012-07-01

413

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

2013-04-19

414

Process controls on the development of stratigraphic trap potential on the margins of confined turbidite systems and aids to reservoir evaluation  

Microsoft Academic Search

Stratigraphic trapping at pinch-out margins is a key feature of many turbidite-hosted hydrocarbon reservoirs. In systems confined by lat- eral or oblique frontal slopes, outcrop studies show that there is a continuum between two geometries of pinch-out configuration. In type A, turbidites thin onto the confining surface—although the final sandstone pinch-out is commonly abrupt—and individual beds tend not to erode

William McCaffrey; Benjamin Kneller

415

Identification of metabolites of crude and processed Fructus Corni in rats by microdialysis sampling coupled with electrospray ionization linear quadrupole ion trap mass spectrometry  

Microsoft Academic Search

A microdialysis (MD) sampling coupled with electrospray ionization linear quadrupole ion trap mass spectrometry (LTQ-MSn) method has been developed for rapid and sensitive analysis of rat microdialysate metabolite profile of Fructus Corni, a well-known Traditional Chinese Medicine (TCM). The purified samples were separated by a reversed-phase HPLC with C18 column under a gradient elution. Parent compounds and metabolites of crude

Gang Cao; Hao Cai; Yun Zhang; Xiaodong Cong; Chengrong Zhang; Baochang Cai

2011-01-01

416

Laser trapping of {sup 21}Na atoms  

SciTech Connect

This thesis describes an experiment in which about four thousand radioactive {sup 21}Na (t{sub l/2} = 22 sec) atoms were trapped in a magneto-optical trap with laser beams. Trapped {sup 21}Na atoms can be used as a beta source in a precision measurement of the beta-asymmetry parameter of the decay of {sup 21}Na {yields} {sup 21}Ne + {Beta}{sup +} + v{sub e}, which is a promising way to search for an anomalous right-handed current coupling in charged weak interactions. Although the number o trapped atoms that we have achieved is still about two orders of magnitude lower than what is needed to conduct a measurement of the beta-asymmetry parameter at 1% of precision level, the result of this experiment proved the feasibility of trapping short-lived radioactive atoms. In this experiment, {sup 21}Na atoms were produced by bombarding {sup 24}Mg with protons of 25 MeV at the 88 in. Cyclotron of Lawrence Berkeley Laboratory. A few recently developed techniques of laser manipulation of neutral atoms were applied in this experiment. The {sup 21}Na atoms emerging from a heated oven were first transversely cooled. As a result, the on-axis atomic beam intensity was increased by a factor of 16. The atoms in the beam were then slowed down from thermal speed by applying Zeeman-tuned slowing technique, and subsequently loaded into a magneto-optical trap at the end of the slowing path. The last two chapters of this thesis present two studies on the magneto-optical trap of sodium atoms. In particular, the mechanisms of magneto-optical traps at various laser frequencies and the collisional loss mechanisms of these traps were examined.

Lu, Zheng-Tian

1994-09-01

417

PROCESSING OF MODIFIED AI (7010)SIC PARTICULATE COMPOSITES BY MECHANICAL ALLOYING AND HOT - PRESSING  

Microsoft Academic Search

Modified Al (7010) matrix composites with 0-15 wt.% dispersion;; of SiC particles (?7 ?m) have been developed by powder metallurgy route. The processing route involved attritor milling of Al, Zn, Mg, Cu and SiC powders blended with 2% stearic acid to accomplish mechanical alloying and dispersion of SiC. The process of mechanical alloying was monitored by image analysis and XRD.

A. N. Tiwari; V. Gopinathan; P. Ramakrishnan

1991-01-01

418

Analytical process design for chemo-mechanical polishing of glass aspheres  

Microsoft Academic Search

This work deals with the chemo-mechanical sub-aperture polishing of glass lenses using spiral tool path and pressure-inflated membrane tools. Current trends in manufacturing precision optics in Europe go to smaller lot sizes and an increasing ratio of custom specific lens design. This requires deterministic processes as well as methods for an analytical process set-up without empirical try-outs. Chemo-mechanical polishing is

Daniel Waechter; Olaf Dambon; Fritz Klocke

2011-01-01

419

Machining Performance Optimization in End ED Milling and Mechanical Grinding Compound Process  

Microsoft Academic Search

Silicon carbide (SiC) ceramic has been widely used in modern industry for its excellent physical and mechanical properties. However, SiC ceramic is difficult to machine owing to its high hardness and brittleness. This paper presents a novel compound process that integrates end electric discharge (ED) milling and mechanical grinding to machine SiC ceramic. The process is able to effectively machine

Renjie Ji; Yonghong Liu; Yanzhen Zhang; Fei Wang; Baoping Cai; Xin Dong

2011-01-01

420

Machining Performance Optimization in End ED Milling and Mechanical Grinding Compound Process  

Microsoft Academic Search

Silicon carbide (SiC) ceramic has been widely used in modern industry for its excellent physical and mechanical properties. However, SiC ceramic is difficult to machine owing to its high hardness and brittleness. This article presents a novel compound process that integrates end electric discharge (ED) milling and mechanical grinding to machine SiC ceramic. The process is able to effectively machine

Renjie Ji; Yonghong Liu; Yanzhen Zhang; Fei Wang; Baoping Cai; Xin Dong

2012-01-01

421

Influence of process conditions on mechanical properties of osmotically dehydrated mango  

Microsoft Academic Search

The influence of osmotic treatments using 45° and 65° Brix sucrose containing calcium lactate at different levels (0%, 1% and 2%), applying or not a vacuum pulse at the beginning of the process, on the mechanical response of mango samples was studied. Mango samples were dehydrated till 30° Brix and were characterised as mechanical properties, sugar and calcium gain, water

J. D. Torres; P. Talens; I. Escriche; A. Chiralt

2006-01-01

422

Interplay between linear, dissipative and permanently critical mechanical processes in Arctic sea ice  

Microsoft Academic Search

Mechanical processes in the Arctic ice pack result in fragmented sea ice cover, the regular geometry of which could be described in main features in terms of the conventional mechanics. However, the size distribution of sea ice floes does not exhibit the random (poissonian-like) statistics and follows the power law typical for self-similar (fractal) structures. The analysis of ice floe

A. Chmel; V. Smirnov; A. Panov