Quantitative sampling of conformational heterogeneity of a DNA hairpin using molecular dynamics simulations and ultrafast fluorescence spectroscopy.

PubMed

Voltz, Karine; Léonard, Jérémie; Touceda, Patricia Tourón; Conyard, Jamie; Chaker, Ziyad; Dejaegere, Annick; Godet, Julien; Mély, Yves; Haacke, Stefan; Stote, Roland H

2016-04-20

Molecular dynamics (MD) simulations and time resolved fluorescence (TRF) spectroscopy were combined to quantitatively describe the conformational landscape of the DNA primary binding sequence (PBS) of the HIV-1 genome, a short hairpin targeted by retroviral nucleocapsid proteins implicated in the viral reverse transcription. Three 2-aminopurine (2AP) labeled PBS constructs were studied. For each variant, the complete distribution of fluorescence lifetimes covering 5 orders of magnitude in timescale was measured and the populations of conformers experimentally observed to undergo static quenching were quantified. A binary quantification permitted the comparison of populations from experimental lifetime amplitudes to populations of aromatically stacked 2AP conformers obtained from simulation. Both populations agreed well, supporting the general assumption that quenching of 2AP fluorescence results from pi-stacking interactions with neighboring nucleobases and demonstrating the success of the proposed methodology for the combined analysis of TRF and MD data. Cluster analysis of the latter further identified predominant conformations that were consistent with the fluorescence decay times and amplitudes, providing a structure-based rationalization for the wide range of fluorescence lifetimes. Finally, the simulations provided evidence of local structural perturbations induced by 2AP. The approach presented is a general tool to investigate fine structural heterogeneity in nucleic acid and nucleoprotein assemblies. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

The origin of ultra diffuse galaxies: stellar feedback and quenching

NASA Astrophysics Data System (ADS)

Chan, T. K.; Kereš, D.; Wetzel, A.; Hopkins, P. F.; Faucher-Giguère, C.-A.; El-Badry, K.; Garrison-Kimmel, S.; Boylan-Kolchin, M.

2018-05-01

We test if the cosmological zoom-in simulations of isolated galaxies from the FIRE project reproduce the properties of ultra diffuse galaxies (UDGs). We show that outflows that dynamically heat galactic stars, together with a passively aging stellar population after imposed quenching, naturally reproduce the observed population of red UDGs, without the need for high spin halos, or dynamical influence from their host cluster. We reproduce the range of surface brightness, radius and absolute magnitude of the observed red UDGs by quenching simulated galaxies at a range of different times. They represent a mostly uniform population of dark matter-dominated dwarf galaxies with M* ˜ 108 M⊙, low metallicity and a broad range of ages; the more massive the UDGs, the older they are. The most massive red UDG in our sample (M* ˜ 3 × 108M⊙) requires quenching at z ˜ 3 when its halo reached Mh ˜ 1011 M⊙. Our simulated UDGs form with normal stellar-to-halo ratios and match the central enclosed masses and the velocity dispersions of the observed UDGs. Enclosed masses remain largely fixed across a broad range of quenching times because the central regions of their dark matter halos complete their growth early. If our simulated dwarfs are not quenched, they evolve into bluer low-surface brightness galaxies with M/L similar to observed field dwarfs. While our simulation sample covers a limited range of formation histories and halo masses, we predict that UDG is a common, and perhaps even dominant, galaxy type around M* ˜ 108 M⊙, both in the field and in clusters.

The origin of ultra diffuse galaxies: stellar feedback and quenching

NASA Astrophysics Data System (ADS)

Chan, T. K.; Kereš, D.; Wetzel, A.; Hopkins, P. F.; Faucher-Giguère, C.-A.; El-Badry, K.; Garrison-Kimmel, S.; Boylan-Kolchin, M.

2018-07-01

We test if the cosmological zoom-in simulations of isolated galaxies from the FIRE project reproduce the properties of ultra diffuse galaxies (UDGs). We show that outflows that dynamically heat galactic stars, together with a passively aging stellar population after imposed quenching, naturally reproduce the observed population of red UDGs, without the need for high spin haloes, or dynamical influence from their host cluster. We reproduce the range of surface brightness, radius, and absolute magnitude of the observed red UDGs by quenching simulated galaxies at a range of different times. They represent a mostly uniform population of dark matter-dominated dwarf galaxies with M* ˜ 108 M⊙, low metallicity, and a broad range of ages; the more massive the UDGs, the older they are. The most massive red UDG in our sample (M* ˜ 3 × 108 M⊙) requires quenching at z ˜ 3 when its halo reached Mh ˜ 1011 M⊙. Our simulated UDGs form with normal stellar-to-halo ratios and match the central enclosed masses and the velocity dispersions of the observed UDGs. Enclosed masses remain largely fixed across a broad range of quenching times because the central regions of their dark matter haloes complete their growth early. If our simulated dwarfs are not quenched, they evolve into bluer low surface brightness galaxies with M/L similar to observed field dwarfs. While our simulation sample covers a limited range of formation histories and halo masses, we predict that UDG is a common, and perhaps even dominant, galaxy type around M* ˜ 108 M⊙, both in the field and in clusters.

Effect of ice-quenching on the change in hardness of a Pd-Au-Zn alloy during porcelain firing simulation.

PubMed

Shin, Hye-Jeong; Kim, Min-Jung; Kim, Hyung-Il; Kwon, Yong Hoon; Seol, Hyo-Joung

2017-03-31

This study examined the effect of ice-quenching after degassing on the change in hardness of a Pd-Au-Zn alloy during porcelain firing simulations. By ice-quenching after degassing, the specimens were softened due to homogenization without the need for an additional softening heat treatment. The lowered hardness by ice-quenching after degassing was recovered greatly from the first stage of porcelain firing process by controlling the cooling rate. The increase in hardness during cooling after porcelain firing was attributed to the precipitation of the f.c.t. PdZn phase containing Au, which caused severe lattice strain in the interphase boundary between the precipitates and matrix of the f.c.c. structure. The final hardness was slightly higher in the ice-quenched specimen than in the specimen cooled at stage 0 (the most effective cooling rate for alloy hardening) after degassing. This was attributed to the more active grain interior precipitation during cooling in the ice-quenched specimen after degassing.

Comparison of Austenite Decomposition Models During Finite Element Simulation of Water Quenching and Air Cooling of AISI 4140 Steel

NASA Astrophysics Data System (ADS)

Babu, K.; Prasanna Kumar, T. S.

2014-08-01

An indigenous, non-linear, and coupled finite element (FE) program has been developed to predict the temperature field and phase evolution during heat treatment of steels. The diffusional transformations during continuous cooling of steels were modeled using Johnson-Mehl-Avrami-Komogorov equation, and the non-diffusion transformation was modeled using Koistinen-Marburger equation. Cylindrical quench probes made of AISI 4140 steel of 20-mm diameter and 50-mm long were heated to 1123 K (850 °C), quenched in water, and cooled in air. The temperature history during continuous cooling was recorded at the selected interior locations of the quench probes. The probes were then sectioned at the mid plane and resultant microstructures were observed. The process of water quenching and air cooling of AISI 4140 steel probes was simulated with the heat flux boundary condition in the FE program. The heat flux for air cooling process was calculated through the inverse heat conduction method using the cooling curve measured during air cooling of a stainless steel 304L probe as an input. The heat flux for the water quenching process was calculated from a surface heat flux model proposed for quenching simulations. The isothermal transformation start and finish times of different phases were taken from the published TTT data and were also calculated using Kirkaldy model and Li model and used in the FE program. The simulated cooling curves and phases using the published TTT data had a good agreement with the experimentally measured values. The computation results revealed that the use of published TTT data was more reliable in predicting the phase transformation during heat treatment of low alloy steels than the use of the Kirkaldy or Li model.

Bar quenching in gas-rich galaxies

NASA Astrophysics Data System (ADS)

Khoperskov, S.; Haywood, M.; Di Matteo, P.; Lehnert, M. D.; Combes, F.

2018-01-01

Galaxy surveys have suggested that rapid and sustained decrease in the star-formation rate (SFR), "quenching", in massive disk galaxies is frequently related to the presence of a bar. Optical and near-IR observations reveal that nearly 60% of disk galaxies in the local universe are barred, thus it is important to understand the relationship between bars and star formation in disk galaxies. Recent observational results imply that the Milky Way quenched about 9-10 Gyr ago, at the transition between the cessation of the growth of the kinematically hot, old, metal-poor thick disk and the kinematically colder, younger, and more metal-rich thin disk. Although perhaps coincidental, the quenching episode could also be related to the formation of the bar. Indeed the transfer of energy from the large-scale shear induced by the bar to increasing turbulent energy could stabilize the gaseous disk against wide-spread star formation and quench the galaxy. To explore the relation between bar formation and star formation in gas rich galaxies quantitatively, we simulated gas-rich disk isolated galaxies. Our simulations include prescriptions for star formation, stellar feedback, and for regulating the multi-phase interstellar medium. We find that the action of stellar bar efficiently quenches star formation, reducing the star-formation rate by a factor of ten in less than 1 Gyr. Analytical and self-consistent galaxy simulations with bars suggest that the action of the stellar bar increases the gas random motions within the co-rotation radius of the bar. Indeed, we detect an increase in the gas velocity dispersion up to 20-35 km s-1 at the end of the bar formation phase. The star-formation efficiency decreases rapidly, and in all of our models, the bar quenches the star formation in the galaxy. The star-formation efficiency is much lower in simulated barred compared to unbarred galaxies and more rapid bar formation implies more rapid quenching.

ELUCID. IV. Galaxy Quenching and its Relation to Halo Mass, Environment, and Assembly Bias

NASA Astrophysics Data System (ADS)

Wang, Huiyuan; Mo, H. J.; Chen, Sihan; Yang, Yang; Yang, Xiaohu; Wang, Enci; van den Bosch, Frank C.; Jing, Yipeng; Kang, Xi; Lin, Weipeng; Lim, S. H.; Huang, Shuiyao; Lu, Yi; Li, Shijie; Cui, Weiguang; Zhang, Youcai; Tweed, Dylan; Wei, Chengliang; Li, Guoliang; Shi, Feng

2018-01-01

We examine the quenched fraction of central and satellite galaxies as a function of galaxy stellar mass, halo mass, and the matter density of their large-scale environment. Matter densities are inferred from our ELUCID simulation, a constrained simulation of the local universe sampled by SDSS, while halo masses and central/satellite classification are taken from the galaxy group catalog of Yang et al. The quenched fraction for the total population increases systematically with the three quantities. We find that the “environmental quenching efficiency,” which quantifies the quenched fraction as a function of halo mass, is independent of stellar mass. And this independence is the origin of the stellar mass independence of density-based quenching efficiency found in previous studies. Considering centrals and satellites separately, we find that the two populations follow similar correlations of quenching efficiency with halo mass and stellar mass, suggesting that they have experienced similar quenching processes in their host halo. We demonstrate that satellite quenching alone cannot account for the environmental quenching efficiency of the total galaxy population, and that the difference between the two populations found previously arises mainly from the fact that centrals and satellites of the same stellar mass reside, on average, in halos of different mass. After removing these effects of halo mass and stellar mass, there remains a weak, but significant, residual dependence on environmental density, which is eliminated when halo assembly bias is taken into account. Our results therefore indicate that halo mass is the prime environmental parameter that regulates the quenching of both centrals and satellites.

Taking care of business in a flash: constraining the time-scale for low-mass satellite quenching with ELVIS

NASA Astrophysics Data System (ADS)

Fillingham, Sean P.; Cooper, Michael C.; Wheeler, Coral; Garrison-Kimmel, Shea; Boylan-Kolchin, Michael; Bullock, James S.

2015-12-01

The vast majority of dwarf satellites orbiting the Milky Way and M31 are quenched, while comparable galaxies in the field are gas rich and star forming. Assuming that this dichotomy is driven by environmental quenching, we use the Exploring the Local Volume in Simulations (ELVIS) suite of N-body simulations to constrain the characteristic time-scale upon which satellites must quench following infall into the virial volumes of their hosts. The high satellite quenched fraction observed in the Local Group demands an extremely short quenching time-scale (˜2 Gyr) for dwarf satellites in the mass range M⋆ ˜ 106-108 M⊙. This quenching time-scale is significantly shorter than that required to explain the quenched fraction of more massive satellites (˜8 Gyr), both in the Local Group and in more massive host haloes, suggesting a dramatic change in the dominant satellite quenching mechanism at M⋆ ≲ 108 M⊙. Combining our work with the results of complementary analyses in the literature, we conclude that the suppression of star formation in massive satellites (M⋆ ˜ 108-1011 M⊙) is broadly consistent with being driven by starvation, such that the satellite quenching time-scale corresponds to the cold gas depletion time. Below a critical stellar mass scale of ˜108 M⊙, however, the required quenching times are much shorter than the expected cold gas depletion times. Instead, quenching must act on a time-scale comparable to the dynamical time of the host halo. We posit that ram-pressure stripping can naturally explain this behaviour, with the critical mass (of M⋆ ˜ 108 M⊙) corresponding to haloes with gravitational restoring forces that are too weak to overcome the drag force encountered when moving through an extended, hot circumgalactic medium.

The size evolution of star-forming and quenched galaxies in the IllustrisTNG simulation

NASA Astrophysics Data System (ADS)

Genel, Shy; Nelson, Dylan; Pillepich, Annalisa; Springel, Volker; Pakmor, Rüdiger; Weinberger, Rainer; Hernquist, Lars; Naiman, Jill; Vogelsberger, Mark; Marinacci, Federico; Torrey, Paul

2018-03-01

We analyse scaling relations and evolution histories of galaxy sizes in TNG100, part of the IllustrisTNG simulation suite. Observational qualitative trends of size with stellar mass, star formation rate and redshift are reproduced, and a quantitative comparison of projected r band sizes at 0 ≲ z ≲ 2 shows agreement to much better than 0.25 dex. We follow populations of z = 0 galaxies with a range of masses backwards in time along their main progenitor branches, distinguishing between main-sequence and quenched galaxies. Our main findings are as follows. (i) At M*, z = 0 ≳ 109.5 M⊙, the evolution of the median main progenitor differs, with quenched galaxies hardly growing in median size before quenching, whereas main-sequence galaxies grow their median size continuously, thus opening a gap from the progenitors of quenched galaxies. This is partly because the main-sequence high-redshift progenitors of quenched z = 0 galaxies are drawn from the lower end of the size distribution of the overall population of main-sequence high-redshift galaxies. (ii) Quenched galaxies with M*, z = 0 ≳ 109.5 M⊙ experience a steep size growth on the size-mass plane after their quenching time, but with the exception of galaxies with M*, z = 0 ≳ 1011 M⊙, the size growth after quenching is small in absolute terms, such that most of the size (and mass) growth of quenched galaxies (and its variation among them) occurs while they are still on the main sequence. After they become quenched, the size growth rate of quenched galaxies as a function of time, as opposed to versus mass, is similar to that of main-sequence galaxies. Hence, the size gap is retained down to z = 0.

Quench anaylsis of MICE spectrometer superconducting solenoid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashikhin, Vladimir; Bross, Alan; /Fermilab

MICE superconducting spectrometer solenoids fabrication and tests are in progress now. First tests of the Spectrometer Solenoid discovered some issues which could be related to the chosen passive quench protection system. Both solenoids do not have heaters and quench propagation relied on the 'quench back' effect, cold diodes, and shunt resistors. The solenoids have very large inductances and stored energy which is 100% dissipated in the cold mass during a quench. This makes their protection a challenging task. The paper presents the quench analysis of these solenoids based on 3D FEA solution of coupled transient electromagnetic and thermal problems. Themore » simulations used the Vector Fields QUENCH code. It is shown that in some quench scenarios, the quench propagation is relatively slow and some areas can be overheated. They describe ways of improving the solenoids quench protection in order to reduce the risk of possible failure.« less

Numerical simulation of quench protection for a 1.5 T persistent mode MgB2 conduction-cooled MRI magnet

NASA Astrophysics Data System (ADS)

Deissler, Robert J.; Baig, Tanvir; Poole, Charles; Amin, Abdullah; Doll, David; Tomsic, Michael; Martens, Michael

2017-02-01

The active quench protection of a 1.5 T MgB2 conduction-cooled MRI magnet operating in persistent current mode is considered. An active quench protection system relies on the detection of the resistive voltage developed in the magnet, which is used to trigger the external energizing of quench heaters located on the surfaces of all ten coil bundles. A numerical integration of the heat equation is used to determine the development of the temperature profile and the maximum temperature in the coil at the origin, or ‘hot spot’, of the quench. Both n-value of the superconductor and magnetoresistance of the wire are included in the simulations. An MgB2 wire manufactured by Hyper Tech Research, Inc. was used as the basis to model the wire for the simulations. With the proposed active quench protection system, the maximum temperature was limited to 200 K or less, which is considered low enough to prevent damage to the magnet. By substituting Glidcop for the Monel in the wire sheath or by increasing the thermal conductivity of the insulation, the margin for safe operation was further increased, the maximum temperature decreasing by more than 40 K. The strain on the MgB2 filaments is calculated using ANSYS, verifying that the stress and strain limits in the MgB2 superconductor and epoxy insulation are not exceeded.

Investigating a method of producing "red and dead" galaxies

NASA Astrophysics Data System (ADS)

Skory, Stephen

2010-08-01

In optical wavelengths, galaxies are observed to be either red or blue. The overall color of a galaxy is due to the distribution of the ages of its stellar population. Galaxies with currently active star formation appear blue, while those with no recent star formation at all (greater than about a Gyr) have only old, red stars. This strong bimodality has lead to the idea of star formation quenching, and various proposed physical mechanisms. In this dissertation, I attempt to reproduce with Enzo the results of Naab et al. (2007), in which red and dead galaxies are formed using gravitational quenching, rather than with one of the more typical methods of quenching. My initial attempts are unsuccessful, and I explore the reasons why I think they failed. Then using simpler methods better suited to Enzo + AMR, I am successful in producing a galaxy that appears to be similar in color and formation history to those in Naab et al. However, quenching is achieved using unphysically high star formation efficiencies, which is a different mechanism than Naab et al. suggests. Preliminary results of a much higher resolution, follow-on simulation of the above show some possible contradiction with the results of Naab et al. Cold gas is streaming into the galaxy to fuel starbursts, while at a similar epoch the galaxies in Naab et al. have largely already ceased forming stars in the galaxy. On the other hand, the results of the high resolution simulation are qualitatively similar to other works in the literature that show a somewhat different gravitational quenching mechanism than Naab et al. I also discuss my work using halo finders to analyze simulated cosmological data, and my work improving the Enzo/AMR analysis tool "yt". This includes two parallelizations of the halo finder HOP (Eisenstein and Hut, 1998) which allows analysis of very large cosmological datasets on parallel machines. The first version is "yt-HOP," which works well for datasets between about 2563 and 5123 particles, but has memory bottlenecks as the datasets get larger. These bottlenecks inspired the second version, "Parallel HOP," which is a fully parallelized method and implementation of HOP that has worked on datasets with more than 20483 particles on hundreds of processing cores. Both methods are described in detail, as are the various effects of performance-related runtime options. Additionally, both halo finders are subjected to a full suite of performance benchmarks varying both dataset sizes and computational resources used. I conclude with descriptions of four new tools I added to yt. A Parallel Structure Function Generator allows analysis of two-point functions, such as correlation functions, using memory- and workload-parallelism. A Parallel Merger Tree Generator leverages the parallel halo finders in yt, such as Parallel HOP, to build the merger tree of halos in a cosmological simulation, and outputs the result to a SQLite database for simple and powerful data extraction. A Star Particle Analysis toolkit takes a group of star particles and can output the rate of formation as a function of time, and/or a synthetic Spectral Energy Distribution (S.E.D.) using the Bruzual and Charlot (2003) data tables. Finally, a Halo Mass Function toolkit takes as input a list of halo masses and can output the halo mass function for the halos, as well as an analytical fit for those halos using several previously published fits.

Quench Modeling in High-field Nb3Sn Accelerator Magnets

NASA Astrophysics Data System (ADS)

Bermudez, S. Izquierdo; Bajas, H.; Bottura, L.

The development of high-field magnets is on-going in the framework of the LHC luminosity upgrade. The resulting peak field, in the range of 12 T to 13 T, requires the use Nb3Sn as superconductor. Due to the high stored energy density (compact winding for cost reduction) and the low stabilizer fraction (to achieve the desired margins), quench protection becomes a challenging problem. Accurate simulation of quench transientsin these magnets is hence crucial to the design choices, the definition of priority R&D and to prove that the magnets are fit for operation. In this paper we focus on the modelling of quench initiation and propagation, we describe approaches that are suitable for magnet simulation, and we compare numerical results with available experimental data.

Reshaping of large aeronautical structural parts: A simplified simulation approach

NASA Astrophysics Data System (ADS)

Mena, Ramiro; Aguado, José V.; Guinard, Stéphane; Huerta, Antonio

2018-05-01

Large aeronautical structural parts present important distortions after machining. This problem is caused by the presence of residual stresses, which are developed during previous manufacturing steps (quenching). Before being put into service, the nominal geometry is restored by means of mechanical methods. This operation is called reshaping and exclusively depends on the skills of a well-trained and experienced operator. Moreover, this procedure is time consuming and nowadays, it is only based on a trial and error approach. Therefore, there is a need at industrial level to solve this problem with the support of numerical simulation tools. By using a simplification hypothesis, it was found that the springback phenomenon behaves linearly and it allows developing a strategy to implement reshaping at an industrial level.

Iterative simulated quenching for designing irregular-spot-array generators.

PubMed

Gillet, J N; Sheng, Y

2000-07-10

We propose a novel, to our knowledge, algorithm of iterative simulated quenching with temperature rescaling for designing diffractive optical elements, based on an analogy between simulated annealing and statistical thermodynamics. The temperature is iteratively rescaled at the end of each quenching process according to ensemble statistics to bring the system back from a frozen imperfect state with a local minimum of energy to a dynamic state in a Boltzmann heat bath in thermal equilibrium at the rescaled temperature. The new algorithm achieves much lower cost function and reconstruction error and higher diffraction efficiency than conventional simulated annealing with a fast exponential cooling schedule and is easy to program. The algorithm is used to design binary-phase generators of large irregular spot arrays. The diffractive phase elements have trapezoidal apertures of varying heights, which fit ideal arbitrary-shaped apertures better than do trapezoidal apertures of fixed heights.

Understanding CO2 decomposition by thermal plasma with supersonic expansion quench

NASA Astrophysics Data System (ADS)

Tao, YANG; Jun, SHEN; Tangchun, RAN; Jiao, LI; Pan, CHEN; Yongxiang, YIN

2018-04-01

CO2 pyrolysis by thermal plasma was investigated, and a high conversion rate of 33% and energy efficiency of 17% were obtained. The high performance benefited from a novel quenching method, which synergizes the converging nozzle and cooling tube. To understand the synergy effect, a computational fluid dynamics simulation was carried out. A quick quenching rate of 107 K s‑1 could be expected when the pyrolysis gas temperature decreased from more than 3000 to 1000 K. According to the simulation results, the quenching mechanism was discussed as follows: first, the compressible fluid was adiabatically expanded in the converging nozzle and accelerated to sonic speed, and parts of the heat energy converted to convective kinetic energy; second, the sonic fluid jet into the cooling tube formed a strong eddy, which greatly enhanced the heat transfer between the inverse-flowing fluid and cooling tube. These two mechanisms ensure a quick quenching to prevent the reverse reaction of CO2 pyrolysis gas when it flows out from the thermal plasma reactor.

Knowledge Assisted Integrated Design of a Component and Its Manufacturing Process

NASA Astrophysics Data System (ADS)

Gautham, B. P.; Kulkarni, Nagesh; Khan, Danish; Zagade, Pramod; Reddy, Sreedhar; Uppaluri, Rohith

Integrated design of a product and its manufacturing processes would significantly reduce the total cost of the products as well as the cost of its development. However this would only be possible if we have a platform that allows us to link together simulations tools used for product design, performance evaluation and its manufacturing processes in a closed loop. In addition to that having a comprehensive knowledgebase that provides systematic knowledge guided assistance to product or process designers who may not possess in-depth design knowledge or in-depth knowledge of the simulation tools, would significantly speed up the end-to-end design process. In this paper, we propose a process and illustrate a case for achieving an integrated product and manufacturing process design assisted by knowledge support for the user to make decisions at various stages. We take transmission component design as an example. The example illustrates the design of a gear for its geometry, material selection and its manufacturing processes, particularly, carburizing-quenching and tempering, and feeding the material properties predicted during heat treatment into performance estimation in a closed loop. It also identifies and illustrates various decision stages in the integrated life cycle and discusses the use of knowledge engineering tools such as rule-based guidance, to assist the designer make informed decisions. Simulation tools developed on various commercial, open-source platforms as well as in-house tools along with knowledge engineering tools are linked to build a framework with appropriate navigation through user-friendly interfaces. This is illustrated through examples in this paper.

Galaxy formation in the Planck cosmology - IV. Mass and environmental quenching, conformity and clustering

NASA Astrophysics Data System (ADS)

Henriques, Bruno M. B.; White, Simon D. M.; Thomas, Peter A.; Angulo, Raul E.; Guo, Qi; Lemson, Gerard; Wang, Wenting

2017-08-01

We study the quenching of star formation as a function of redshift, environment and stellar mass in the galaxy formation simulations of Henriques et al. (2015), which implement an updated version of the Munich semi-analytic model (L-GALAXIES) on the two Millennium Simulations after scaling to a Planck cosmology. In this model, massive galaxies are quenched by active galactic nucleus (AGN) feedback depending on both black hole and hot gas mass, and hence indirectly on stellar mass. In addition, satellite galaxies of any mass can be quenched by ram-pressure or tidal stripping of gas and through the suppression of gaseous infall. This combination of processes produces quenching efficiencies which depend on stellar mass, host halo mass, environment density, distance to group centre and group central galaxy properties in ways which agree qualitatively with observation. Some discrepancies remain in dense regions and close to group centres, where quenching still seems too efficient. In addition, although the mean stellar age of massive galaxies agrees with observation, the assumed AGN feedback model allows too much ongoing star formation at late times. The fact that both AGN feedback and environmental effects are stronger in higher density environments leads to a correlation between the quenching of central and satellite galaxies which roughly reproduces observed conformity trends inside haloes.

Simulations of Cold Electroweak Baryogenesis: quench from portal coupling to new singlet field

NASA Astrophysics Data System (ADS)

Mou, Zong-Gang; Saffin, Paul M.; Tranberg, Anders

2018-01-01

We compute the baryon asymmetry generated from Cold Electroweak Baryogenesis, when a dynamical Beyond-the-Standard-Model scalar singlet field triggers the spinodal transition. Using a simple potential for this additional field, we match the speed of the quench to earlier simulations with a "by-hand" mass flip. We find that for the parameter subspace most similar to a by-hand transition, the final baryon asymmetry shows a similar dependence on quench time and is of the same magnitude. For more general parameter choices the Higgs-singlet dynamics can be very complicated, resulting in an enhancement of the final baryon asymmetry. Our results validate and generalise results of simulations in the literature and open up the Cold Electroweak Baryogenesis scenario to further model building.

Organic Scintillator Detector Response Simulations with DRiFT

DOE PAGES

Andrews, Madison Theresa; Bates, Cameron Russell; Mckigney, Edward Allen; ...

2016-06-11

Here, this work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNPR output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed- field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNPR ®6, which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discriminationmore » plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.« less

Organic scintillator detector response simulations with DRiFT

NASA Astrophysics Data System (ADS)

Andrews, M. T.; Bates, C. R.; McKigney, E. A.; Solomon, C. J.; Sood, A.

2016-09-01

This work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNP® output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed-field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNP® 6 , which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discrimination plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.

Transient analysis of an HTS DC power cable with an HVDC system

NASA Astrophysics Data System (ADS)

Dinh, Minh-Chau; Ju, Chang-Hyeon; Kim, Jin-Geun; Park, Minwon; Yu, In-Keun; Yang, Byeongmo

2013-11-01

The operational characteristics of a superconducting DC power cable connected to a highvoltage direct current (HVDC) system are mainly concerned with the HVDC control and protection system. To confirm how the cable operates with the HVDC system, verifications using simulation tools are needed. This paper presents a transient analysis of a high temperature superconducting (HTS) DC power cable in connection with an HVDC system. The study was conducted via the simulation of the HVDC system and a developed model of the HTS DC power cable using a real time digital simulator (RTDS). The simulation was performed with some cases of short circuits that may have caused system damage. The simulation results show that during the faults, the quench did not happen with the HTS DC power cable because the HVDC controller reduced some degree of the fault current. These results could provide useful data for the protection design of a practical HVDC and HTS DC power cable system.

Wetting-layer formation mechanisms of surface-directed phase separation under different quench depths with off-critical compositions in polymer binary mixture

NASA Astrophysics Data System (ADS)

Yan, Li-Tang; Xie, Xu-Ming

2007-02-01

Focusing on the off-critical condition, the quench depth dependence of surface-directed phase separation in the polymer binary mixture is numerically investigated by combination of the Cahn-Hilliard-Cook theory and the Flory-Huggins-de Gennes theory. Two distinct situations, i.e., for the wetting, the minority component is preferred by the surface and the majority component is preferred by the surface, are discussed in detail. The simulated results show that the formation mechanism of the wetting layer is affected by both the quench depth and the off-critical extent. Moreover, a diagram, illustrating the formation mechanisms of the wetting layer with various quench depths and compositions, is obtained on the basis of the simulated results. It is found that, when the minority component is preferred by the surface, the growth of the wetting layer can exhibit pure diffusion limited growth law, logarithmic growth law, and Lifshitz-Slyozov growth law. However, when the majority component is preferred by the surface, the wetting layer always grows logarithmically, regardless of the quench depth and the off-critical extent. It is interesting that the surface-induced nucleation can be observed in this case. The simulated results demonstrate that the surface-induced nucleation only occurs below a certain value of the quench depth, and a detailed range about it is calculated and indicated. Furthermore, the formation mechanisms of the wetting layer are theoretically analyzed in depth by the chemical potential gradient.

Nonequilibrium forces following quenches in active and thermal matter.

PubMed

Rohwer, Christian M; Solon, Alexandre; Kardar, Mehran; Krüger, Matthias

2018-03-01

Nonequilibrium systems with conserved quantities like density or momentum are known to exhibit long-ranged correlations. This, in turn, leads to long-ranged fluctuation-induced (Casimir) forces, predicted to arise in a variety of nonequilibrium settings. Here, we study such forces, which arise transiently between parallel plates or compact inclusions in a gas of particles, following a change ("quench") in temperature or activity of the medium. Analytical calculations, as well as numerical simulations of passive or active Brownian particles, indicate two distinct forces: (i) The immediate effect of the quench is adsorption or desorption of particles of the medium to the immersed objects, which in turn initiates a front of relaxing (mean) density. This leads to time-dependent density-induced forces. (ii) A long-term effect of the quench is that density fluctuations are modified, manifested as transient (long-ranged) (pair-)correlations that relax diffusively to their (short-ranged) steady-state limit. As a result, transient fluctuation-induced forces emerge. We discuss the properties of fluctuation-induced and density-induced forces as regards universality, relaxation as a function of time, and scaling with distance between objects. Their distinct signatures allow us to distinguish the two types of forces in simulation data. Our simulations also show that a quench of the effective temperature of an active medium gives rise to qualitatively similar effects to a temperature quench in a passive medium. Based on this insight, we propose several scenarios for the experimental observation of the forces described here.

Nonequilibrium forces following quenches in active and thermal matter

NASA Astrophysics Data System (ADS)

Rohwer, Christian M.; Solon, Alexandre; Kardar, Mehran; Krüger, Matthias

2018-03-01

Nonequilibrium systems with conserved quantities like density or momentum are known to exhibit long-ranged correlations. This, in turn, leads to long-ranged fluctuation-induced (Casimir) forces, predicted to arise in a variety of nonequilibrium settings. Here, we study such forces, which arise transiently between parallel plates or compact inclusions in a gas of particles, following a change ("quench") in temperature or activity of the medium. Analytical calculations, as well as numerical simulations of passive or active Brownian particles, indicate two distinct forces: (i) The immediate effect of the quench is adsorption or desorption of particles of the medium to the immersed objects, which in turn initiates a front of relaxing (mean) density. This leads to time-dependent density-induced forces. (ii) A long-term effect of the quench is that density fluctuations are modified, manifested as transient (long-ranged) (pair-)correlations that relax diffusively to their (short-ranged) steady-state limit. As a result, transient fluctuation-induced forces emerge. We discuss the properties of fluctuation-induced and density-induced forces as regards universality, relaxation as a function of time, and scaling with distance between objects. Their distinct signatures allow us to distinguish the two types of forces in simulation data. Our simulations also show that a quench of the effective temperature of an active medium gives rise to qualitatively similar effects to a temperature quench in a passive medium. Based on this insight, we propose several scenarios for the experimental observation of the forces described here.

Characterisation of the turbulent electromotive force and its magnetically-mediated quenching in a global EULAG-MHD simulation of solar convection

NASA Astrophysics Data System (ADS)

Simard, Corinne; Charbonneau, Paul; Dubé, Caroline

2016-10-01

We perform a mean-field analysis of the EULAG-MHD millenium simulation of global magnetohydrodynamical convection presented in Passos and Charbonneau (2014). The turbulent electromotive force (emf) operating in the simulation is assumed to be linearly related to the cyclic axisymmetric mean magnetic field and its first spatial derivatives. At every grid point in the simulation's meridional plane, this assumed relationship involves 27 independent tensorial coefficients. Expanding on Racine et al. (2011), we extract these coefficients from the simulation data through a least-squares minimization procedure based on singular value decomposition. The reconstructed α -tensor shows good agreement with that obtained by Racine et al. (2011), who did not include derivatives of the mean-field in their fit, as well as with the α -tensor extracted by Augustson et al. (2015) from a distinct ASH MHD simulation. The isotropic part of the turbulent magnetic diffusivity tensor β is positive definite and reaches values of 5.0 ×107 m2 s-1 in the middle of the convecting fluid layers. The spatial variations of both αϕϕ and βϕϕ component are well reproduced by expressions obtained under the Second Order Correlation Approximation, with a good matching of amplitude requiring a turbulent correlation time about five times smaller than the estimated turnover time of the small-scale turbulent flow. By segmenting the simulation data into epochs of magnetic cycle minima and maxima, we also measure α - and β -quenching. We find the magnetic quenching of the α -effect to be driven primarily by a reduction of the small-scale flow's kinetic helicity, with variations of the current helicity playing a lesser role in most locations in the simulation domain. Our measurements of turbulent diffusivity quenching are restricted to the βϕϕ component, but indicate a weaker quenching, by a factor of ≃ 1.36, than of the α -effect, which in our simulation drops by a factor of three between the minimum and maximum phases of the magnetic cycle.

Skyrmion morphology in ultrathin magnetic films

NASA Astrophysics Data System (ADS)

Gross, I.; Akhtar, W.; Hrabec, A.; Sampaio, J.; Martínez, L. J.; Chouaieb, S.; Shields, B. J.; Maletinsky, P.; Thiaville, A.; Rohart, S.; Jacques, V.

2018-02-01

Nitrogen-vacancy magnetic microscopy is employed in the quenching mode as a noninvasive, high-resolution tool to investigate the morphology of isolated skyrmions in ultrathin magnetic films. The skyrmion size and shape are found to be strongly affected by local pinning effects and magnetic field history. Micromagnetic simulations including a static disorder, based on the physical model of grain-to-grain thickness variations, reproduce all experimental observations and reveal the key role of disorder and magnetic history in the stabilization of skyrmions in ultrathin magnetic films. This work opens the way to an in-depth understanding of skyrmion dynamics in real, disordered media.

Atomic quantum simulation of dynamical gauge fields coupled to fermionic matter: from string breaking to evolution after a quench.

PubMed

Banerjee, D; Dalmonte, M; Müller, M; Rico, E; Stebler, P; Wiese, U-J; Zoller, P

2012-10-26

Using a Fermi-Bose mixture of ultracold atoms in an optical lattice, we construct a quantum simulator for a U(1) gauge theory coupled to fermionic matter. The construction is based on quantum links which realize continuous gauge symmetry with discrete quantum variables. At low energies, quantum link models with staggered fermions emerge from a Hubbard-type model which can be quantum simulated. This allows us to investigate string breaking as well as the real-time evolution after a quench in gauge theories, which are inaccessible to classical simulation methods.

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

PubMed Central

Rabenhold, Markus; Steiniger, Frank; Fahr, Alfred; Hilger, Ingrid

2015-01-01

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous number of imaging techniques currently available and the progress in instrumentation, there is still a need for highly sensitive probes that are suitable for in vivo imaging. One typical problem of available preclinical fluorescent probes is their rapid clearance in vivo, which reduces their imaging sensitivity. To circumvent rapid clearance, increase number of dye molecules at the target site, and thereby reduce background autofluorescence, encapsulation of the near-infrared fluorescent dye, DY-676-COOH in liposomes and verification of its potential for in vivo imaging of inflammation was done. DY-676 is known for its ability to self-quench at high concentrations. We first determined the concentration suitable for self-quenching, and then encapsulated this quenching concentration into the aqueous interior of PEGylated liposomes. To substantiate the quenching and activation potential of the liposomes we use a harsh freezing method which leads to damage of liposomal membranes without affecting the encapsulated dye. The liposomes characterized by a high level of fluorescence quenching were termed Lip-Q. We show by experiments with different cell lines that uptake of Lip-Q is predominantly by phagocytosis which in turn enabled the characterization of its potential as a tool for in vivo imaging of inflammation in mice models. Furthermore, we use a zymosan-induced edema model in mice to substantiate the potential of Lip-Q in optical imaging of inflammation in vivo. Considering possible uptake due to inflammation-induced enhanced permeability and retention (EPR) effect, an always-on liposome formulation with low, non-quenched concentration of DY-676-COOH (termed Lip-dQ) and the free DY-676-COOH were compared with Lip-Q in animal trials. PMID:25591069

Improving the Quality of Hot Stamping Parts with Innovative Press Technology and Inline Process Control

NASA Astrophysics Data System (ADS)

Vollmer, R.; Palm, C.

2017-09-01

The increasing number of hot stamped parts in the automotive industry is challenging different process areas. This paper presents a method how to improve the production rates over the whole life cycle of a hot forming part. In the core element of a hot forming line, the hydraulic press, mainly two processing steps are performed. Forming and quenching of the sheet metal part. In addition to the forming operation, it is inevitable to optimize the quenching condition in the bottom dead centre in order to reach a fully martensitic structure and tight geometrical tolerances of the part. Deviations in the blank thickness, tool wear, polishing of classical tools impair the quenching condition and therefore the part quality over the time. A new press and tool design has been developed to counter this effect by providing homogenous contact pressure over the whole die. Especially with a multi cavity tool, the new method is advantageous. Test series have shown that the new tool and press concept can produce parts with a blank thickness of 1.0 mm within 8.0 s cycle time. The so called PCH flex principle makes it possible to produce such high output rates under reliable conditions.

Satellite quenching time-scales in clusters from projected phase space measurements matched to simulated orbits

NASA Astrophysics Data System (ADS)

Oman, Kyle A.; Hudson, Michael J.

2016-12-01

We measure the star formation quenching efficiency and time-scale in cluster environments. Our method uses N-body simulations to estimate the probability distribution of possible orbits for a sample of observed Sloan Digital Sky Survey galaxies in and around clusters based on their position and velocity offsets from their host cluster. We study the relationship between their star formation rates and their likely orbital histories via a simple model in which star formation is quenched once a delay time after infall has elapsed. Our orbit library method is designed to isolate the environmental effect on the star formation rate due to a galaxy's present-day host cluster from `pre-processing' in previous group hosts. We find that quenching of satellite galaxies of all stellar masses in our sample (109-10^{11.5}M_{⊙}) by massive (> 10^{13} M_{⊙}) clusters is essentially 100 per cent efficient. Our fits show that all galaxies quench on their first infall, approximately at or within a Gyr of their first pericentric passage. There is little variation in the onset of quenching from galaxy-to-galaxy: the spread in this time is at most ˜2 Gyr at fixed M*. Higher mass satellites quench earlier, with very little dependence on host cluster mass in the range probed by our sample.

Quench protection analysis of the Mu2e production solenoid

NASA Astrophysics Data System (ADS)

Kashikhin, Vadim; Ambrosio, Giorgio; Andreev, Nikolai; Lamm, Michael; Nicol, Thomas; Orris, Darryl; Page, Thomas

2014-01-01

The Muon-to-Electron conversion experiment (Mu2e), under development at Fermilab, seeks to detect direct muon to electron conversion to provide evidence for a process violating muon and electron lepton number conservation that cannot be explained by the Standard Model of particle physics. The Mu2e magnet system consists of three large superconducting solenoids. In case of a quench, the stored magnetic energy is extracted to an external dump circuit. However, because of the fast current decay, a significant fraction of the energy dissipates inside of the cryostat in the coil support shells made of structural aluminum, and in the radiation shield. A 3D finite-element model of the complete cold-mass was created in order to simulate the quench development and understand the role of the quench-back. The simulation results are reported at the normal and non-standard operating conditions.

Quench protection analysis of the Mu2e production solenoid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashikhin, Vadim; Ambrosio, Giorgio; Andreev, Nikolai

The Muon-to-Electron conversion experiment (Mu2e), under development at Fermilab, seeks to detect direct muon to electron conversion to provide evidence for a process violating muon and electron lepton number conservation that cannot be explained by the Standard Model of particle physics. The Mu2e magnet system consists of three large superconducting solenoids. In case of a quench, the stored magnetic energy is extracted to an external dump circuit. However, because of the fast current decay, a significant fraction of the energy dissipates inside of the cryostat in the coil support shells made of structural aluminum, and in the radiation shield. Amore » 3D finite-element model of the complete cold-mass was created in order to simulate the quench development and understand the role of the quench-back. The simulation results are reported at the normal and non-standard operating conditions.« less

Numerical Analysis of Heat Transfer During Quenching Process

NASA Astrophysics Data System (ADS)

Madireddi, Sowjanya; Krishnan, Krishnan Nambudiripad; Reddy, Ammana Satyanarayana

2018-04-01

A numerical model is developed to simulate the immersion quenching process of metals. The time of quench plays an important role if the process involves a defined step quenching schedule to obtain the desired characteristics. Lumped heat capacity analysis used for this purpose requires the value of heat transfer coefficient, whose evaluation requires large experimental data. Experimentation on a sample work piece may not represent the actual component which may vary in dimension. A Fluid-Structure interaction technique with a coupled interface between the solid (metal) and liquid (quenchant) is used for the simulations. Initial times of quenching shows boiling heat transfer phenomenon with high values of heat transfer coefficients (5000-2.5 × 105 W/m2K). Shape of the work piece with equal dimension shows less influence on the cooling rate Non-uniformity in hardness at the sharp corners can be reduced by rounding off the edges. For a square piece of 20 mm thickness, with 3 mm fillet radius, this difference is reduced by 73 %. The model can be used for any metal-quenchant combination to obtain time-temperature data without the necessity of experimentation.

The nature of massive transition galaxies in CANDELS, GAMA and cosmological simulations

NASA Astrophysics Data System (ADS)

Pandya, Viraj; Brennan, Ryan; Somerville, Rachel S.; Choi, Ena; Barro, Guillermo; Wuyts, Stijn; Taylor, Edward N.; Behroozi, Peter; Kirkpatrick, Allison; Faber, Sandra M.; Primack, Joel; Koo, David C.; McIntosh, Daniel H.; Kocevski, Dale; Bell, Eric F.; Dekel, Avishai; Fang, Jerome J.; Ferguson, Henry C.; Grogin, Norman; Koekemoer, Anton M.; Lu, Yu; Mantha, Kameswara; Mobasher, Bahram; Newman, Jeffrey; Pacifici, Camilla; Papovich, Casey; van der Wel, Arjen; Yesuf, Hassen M.

2017-12-01

We explore observational and theoretical constraints on how galaxies might transition between the 'star-forming main sequence' (SFMS) and varying 'degrees of quiescence' out to z = 3. Our analysis is focused on galaxies with stellar mass M* > 1010 M⊙, and is enabled by GAMA and CANDELS observations, a semi-analytic model (SAM) of galaxy formation, and a cosmological hydrodynamical 'zoom in' simulation with momentum-driven AGN feedback. In both the observations and the SAM, transition galaxies tend to have intermediate Sérsic indices, half-light radii, and surface stellar mass densities compared to star-forming and quiescent galaxies out to z = 3. We place an observational upper limit on the average population transition time-scale as a function of redshift, finding that the average high-redshift galaxy is on a 'fast track' for quenching whereas the average low-redshift galaxy is on a 'slow track' for quenching. We qualitatively identify four physical origin scenarios for transition galaxies in the SAM: oscillations on the SFMS, slow quenching, fast quenching, and rejuvenation. Quenching time-scales in both the SAM and the hydrodynamical simulation are not fast enough to reproduce the quiescent population that we observe at z ∼ 3. In the SAM, we do not find a clear-cut morphological dependence of quenching time-scales, but we do predict that the mean stellar ages, cold gas fractions, SMBH (supermassive black hole) masses and halo masses of transition galaxies tend to be intermediate relative to those of star-forming and quiescent galaxies at z < 3.

Identifying Jets Using Artifical Neural Networks

NASA Astrophysics Data System (ADS)

Rosand, Benjamin; Caines, Helen; Checa, Sofia

2017-09-01

We investigate particle jet interactions with the Quark Gluon Plasma (QGP) using artificial neural networks modeled on those used in computer image recognition. We create jet images by binning jet particles into pixels and preprocessing every image. We analyzed the jets with a Multi-layered maxout network and a convolutional network. We demonstrate each network's effectiveness in differentiating simulated quenched jets from unquenched jets, and we investigate the method that the network uses to discriminate among different quenched jet simulations. Finally, we develop a greater understanding of the physics behind quenched jets by investigating what the network learnt as well as its effectiveness in differentiating samples. Yale College Freshman Summer Research Fellowship in the Sciences and Engineering.

TASK 2: QUENCH ZONE SIMULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fusselman, Steve

Aerojet Rocketdyne (AR) has developed an innovative gasifier concept incorporating advanced technologies in ultra-dense phase dry feed system, rapid mix injector, and advanced component cooling to significantly improve gasifier performance, life, and cost compared to commercially available state-of-the-art systems. A key feature of the AR gasifier design is the transition from the gasifier outlet into the quench zone, where the raw syngas is cooled to ~ 400°C by injection and vaporization of atomized water. Earlier pilot plant testing revealed a propensity for the original gasifier outlet design to accumulate slag in the outlet, leading to erratic syngas flow from themore » outlet. Subsequent design modifications successfully resolved this issue in the pilot plant gasifier. In order to gain greater insight into the physical phenomena occurring within this zone, AR developed a cold flow simulation apparatus with Coanda Research & Development with a high degree of similitude to hot fire conditions with the pilot scale gasifier design, and capable of accommodating a scaled-down quench zone for a demonstration-scale gasifier. The objective of this task was to validate similitude of the cold flow simulation model by comparison of pilot-scale outlet design performance, and to assess demonstration scale gasifier design feasibility from testing of a scaled-down outlet design. Test results did exhibit a strong correspondence with the two pilot scale outlet designs, indicating credible similitude for the cold flow simulation device. Testing of the scaled-down outlet revealed important considerations in the design and operation of the demonstration scale gasifier, in particular pertaining to the relative momentum between the downcoming raw syngas and the sprayed quench water and associated impacts on flow patterns within the quench zone. This report describes key findings from the test program, including assessment of pilot plant configuration simulations relative to actual results on the pilot plant gasifier and demonstration plant design recommendations, based on cold flow simulation results.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrews, Madison Theresa; Bates, Cameron Russell; Mckigney, Edward Allen

Here, this work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNPR output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed- field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNPR ®6, which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discriminationmore » plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.« less

Fatigue Life Variability in Large Aluminum Forgings with Residual Stress

DTIC Science & Technology

2011-07-01

been conducted. A detailed finite element analysis of the forge/ quench /coldwork/machine process was performed in order to predict the bulk residual...forge/ quench /coldwork/machine process was performed in order to predict the bulk residual stresses in a fictitious aluminum bulkhead. The residual...continues to develop the capability for computational simulation of the forge, quench , cold work and machining processes. In order to handle the

Testing beam-induced quench levels of LHC superconducting magnets

NASA Astrophysics Data System (ADS)

Auchmann, B.; Baer, T.; Bednarek, M.; Bellodi, G.; Bracco, C.; Bruce, R.; Cerutti, F.; Chetvertkova, V.; Dehning, B.; Granieri, P. P.; Hofle, W.; Holzer, E. B.; Lechner, A.; Nebot Del Busto, E.; Priebe, A.; Redaelli, S.; Salvachua, B.; Sapinski, M.; Schmidt, R.; Shetty, N.; Skordis, E.; Solfaroli, M.; Steckert, J.; Valuch, D.; Verweij, A.; Wenninger, J.; Wollmann, D.; Zerlauth, M.

2015-06-01

In the years 2009-2013 the Large Hadron Collider (LHC) has been operated with the top beam energies of 3.5 and 4 TeV per proton (from 2012) instead of the nominal 7 TeV. The currents in the superconducting magnets were reduced accordingly. To date only seventeen beam-induced quenches have occurred; eight of them during specially designed quench tests, the others during injection. There has not been a single beam-induced quench during normal collider operation with stored beam. The conditions, however, are expected to become much more challenging after the long LHC shutdown. The magnets will be operating at near nominal currents, and in the presence of high energy and high intensity beams with a stored energy of up to 362 MJ per beam. In this paper we summarize our efforts to understand the quench levels of LHC superconducting magnets. We describe beam-loss events and dedicated experiments with beam, as well as the simulation methods used to reproduce the observable signals. The simulated energy deposition in the coils is compared to the quench levels predicted by electrothermal models, thus allowing one to validate and improve the models which are used to set beam-dump thresholds on beam-loss monitors for run 2.

Quenching and Sensitizing Fullerene Photoreactions by Natural Organic Matter

EPA Science Inventory

Effects of natural organic matter (NOM) on the photoreaction kinetics of fullerenes (i.e., C60 and fullerenol) were investigated using simulated sunlight and monochromatic radiation (365 nm). NOM from several sources quenched (slowed) the photoreaction of C60 aggregates in water ...

Quench simulation studies of TAC jelly roll superferric dipole corrector elements for the SSC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez, G.

Using the computer program SSC-DTAC-T, which is a modification of the quench computer program SSC-RR to model Jelly Roll coils, the quench behavior of the dipole corrector element (TAC design with Jelly Roll winding) is studied. The simulations are made as a function of the length of the magnet, the copper-to-superconducting ratio, and the thickness of insulation surrounding the wires. The magnet is self-protected with all listed considerations. In addition, this implies that other corrector multipoles (quadrupole, sextupole, octupole, etc.), which use the same conductor winding technique, are self-protected. A passive protection system should work for these elements. 9 refs.,more » 18 figs., 1 tab.« less

The transformation and quenching of simulated gas-rich dwarf satellites within a group environment

NASA Astrophysics Data System (ADS)

Yozin, C.; Bekki, K.

2015-10-01

The underlying mechanisms driving the quenching of dwarf-mass satellite galaxies remain poorly constrained, but recent studies suggest they are particularly inefficient for those satellites with stellar mass 109 M⊙. We investigate the characteristic evolution of these systems with chemodynamical simulations and idealized models of their tidal/hydrodynamic interactions within the 10^{13-13.5}-M⊙ group-mass hosts in which they are preferentially quenched. Our fiducial simulations highlight the role played by secular star formation and stellar bars, and demonstrate a transition from a gas-rich to passive, H I-deficient state (i.e. ΔSFR ≤ -1, def_{H I}} ≥ 0.5) within 6 Gyr of first infall. Furthermore, in the 8-10 Gyr in which these systems have typically been resident within group hosts, the bulge-to-total ratio of an initially bulgeless disc can increase to 0.3 < B/T < 0.4, its specific angular momentum λR reduce to ˜0.5, and strong bisymmetries formed. Ultimately, this scenario yields satellites resembling dwarf S0s, a result that holds for a variety of infall inclinations/harassments albeit with broad scatter. The key assumptions here lie in the rapid removal of the satellite's gaseous halo upon virial infall, and the satellite's local intragroup medium density being defined by the host's spherically averaged profile. We demonstrate how quenching can be greatly enhanced if the satellite lies in an overdensity, consistent with recent cosmological-scale simulations but contrasting with observationally inferred quenching mechanisms/time-scales; an appraisal of these results with respect to the apparent preferential formation of dS0s/S0s in groups is also given.

The role of quench rate in colloidal gels.

PubMed

Royall, C Patrick; Malins, Alex

2012-01-01

Interactions between colloidal particles have hitherto usually been fixed by the suspension composition. Recent experimental developments now enable the control of interactions in situ. Here we use Brownian dynamics simulations to investigate the effect of controlling interactions upon gelation, by "quenching" the system from an equilibrium fluid to a gel. We find that, contrary to the normal case of an instantaneous quench, where the local structure of the gel is highly disordered, controlled quenching results in a gel with a much higher degree of local order. Under sufficiently slow quenching, local crystallisation is found, which is strongly enhanced when a monodisperse system is used. The higher the degree of local order, the smaller the mean squared displacement, indicating an enhancement of gel stability.

Fluorescence self-quenching assay for the detection of target collagen sequences using a short probe peptide.

PubMed

Nian, Linge; Hu, Yue; Fu, Caihong; Song, Chen; Wang, Jie; Xiao, Jianxi

2018-01-01

The development of novel assays to detect collagen fragments is of utmost importance for diagnostic, prognostic and therapeutic decisions in various collagen-related diseases, and one essential question is to discover probe peptides that can specifically recognize target collagen sequences. Herein we have developed the fluorescence self-quenching assay as a convenient tool to screen the capability of a series of fluorescent probe peptides of variable lengths to bind with target collagen peptides. We have revealed that the targeting ability of probe peptides is length-dependent, and have discovered a relatively short probe peptide FAM-G(POG) 8 capable to identify the target peptide. We have further demonstrated that fluorescence self-quenching assay together with this short probe peptide can be applied to specifically detect the desired collagen fragment in complex biological media. Fluorescence self-quenching assay provides a powerful new tool to discover effective peptides for the recognition of collagen biomarkers, and it may have great potential to identify probe peptides for various protein biomarkers involved in pathological conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Relationship between locked modes and thermal quenches in DIII-D

NASA Astrophysics Data System (ADS)

Sweeney, R.; Choi, W.; Austin, M.; Brookman, M.; Izzo, V.; Knolker, M.; La Haye, R. J.; Leonard, A.; Strait, E.; Volpe, F. A.; The DIII-D Team

2018-05-01

Locked modes are known to be one of the major causes of disruptions, but the physical mechanisms by which locking leads to disruptions are not well understood. Here we analyze the evolution of the temperature profile in the presence of multiple coexisting locked modes during partial and full thermal quenches. Partial quenches are often observed to be an initial, distinct stage in the full thermal quench. Near the onset of partial quenches, locked island O-points are observed to align with each other on the midplane, and their widths are sufficient to overlap each other, as indicated by the Chirikov parameter. Energy conservation analysis of one partial thermal quench shows that the energy lost is both radiated in the divertor region, and conducted or convected to the divertor. Nonlinear resistive magnetohydrodynamic simulations support the interpretation of stochastic fields causing a partial axisymmetric collapse, though the simulated temperature profile exhibits less degradation than the experimental profiles. In discharges with minimum values of the safety factor above  ∼1.2, locked modes are observed to self-stabilize by inducing, possibly via double tearing modes, a minor disruption that removes their neoclassical drive. These high q min discharges often exhibit relatively low ratios of the plasma internal inductance to the safety factor at 95% of the poloidal flux, which might imply classical stability, in agreement with the decay of the mode when the neoclassical drive is removed.

Syngas formation in methane flames and carbon monoxide release during quenching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinberg, Felix; Carleton, Fred; Houdmont, Raphael

Following a recent investigation into chemi-ionization and chemiluminescence during gradual aeration of small, laminar methane flames, we proposed that partial oxidation products, or syngas constituents, formed in the pre-flame zone well below the luminous region, were responsible for the observed effects. We therefore map temperature, CO, and H{sub 2} for geometries and conditions relevant to burners in domestic boiler systems, to assess the potential hazard of CO release into the ambient atmosphere, should any partial quenching occur. CO concentrations peaks of 5.5 volume % are recorded in the core surrounding the axis. Appreciable CO concentrations are also found in themore » absence of added air. Experiments on various burner port geometries and temperatures suggest that this is not due to air entrainment at the flame base but to diffusion from zones closer to the flame. Next, quenching surfaces such as grids, perforated plates and flame trap matrices of different metals are progressively lowered into the flame. To avoid flow line distortion, suction aspirates the quenched products. The highest emission rate occurs with the quenching plane some 4 mm above the burner; further lowering of the quenching surface causes flame extinction. The maximum CO release is close to converting 10% of the CH{sub 4} feed, with some variation with quenching material. Expressing this potential release in terms of, e.g. boiler power, predicts a potentially serious hazard. Results of numerical simulations adequately parallel the experimental sampling profiles and provide insights into local concentrations, as well as the spatially resolved CO flux, which is calculated for a parabolic inlet flow profile. Integration across the stream implies, on the basis of the simulation, a possible tripling of the experimental CO release, were quenching simply to release the local gas composition into the atmosphere. Comparison with experiment suggests some chemical interaction with the quenching surface. (author)« less

Quench simulation studies of the TAC Jelly Roll superferric dipole corrector elements for the SSC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez, G.

Using the computer program SSC-DTAC-T, which is a modification of the quench computer program SSC-RR, to model Jelly Roll coils, the quench behavior of the dipole corrector element (TAC design with Jelly roll winding) is studied. The simulations are made as a function of the length of the magnet, the copper to superconducting ratio, and the thickness of insulation surrounding the wires. The magnet is quite well self-protected under all of these considerations. In addition, this implies that the other corrector multipoles (quadrupole, sextupole, octupole, etc.) which use the same conductor winding technique are self-protected. A passive protection system ismore » likely to work for these elements. 6 refs., 2 figs., 1 tab.« less

Mean-field approaches to the totally asymmetric exclusion process with quenched disorder and large particles

NASA Astrophysics Data System (ADS)

Shaw, Leah B.; Sethna, James P.; Lee, Kelvin H.

2004-08-01

The process of protein synthesis in biological systems resembles a one-dimensional driven lattice gas in which the particles (ribosomes) have spatial extent, covering more than one lattice site. Realistic, nonuniform gene sequences lead to quenched disorder in the particle hopping rates. We study the totally asymmetric exclusion process with large particles and quenched disorder via several mean-field approaches and compare the mean-field results with Monte Carlo simulations. Mean-field equations obtained from the literature are found to be reasonably effective in describing this system. A numerical technique is developed for computing the particle current rapidly. The mean-field approach is extended to include two-point correlations between adjacent sites. The two-point results are found to match Monte Carlo simulations more closely.

Microstructure Modeling of 3rd Generation Disk Alloys

NASA Technical Reports Server (NTRS)

Jou, Herng-Jeng

2010-01-01

The objective of this program is to model, validate, and predict the precipitation microstructure evolution, using PrecipiCalc (QuesTek Innovations LLC) software, for 3rd generation Ni-based gas turbine disc superalloys during processing and service, with a set of logical and consistent experiments and characterizations. Furthermore, within this program, the originally research-oriented microstructure simulation tool will be further improved and implemented to be a useful and user-friendly engineering tool. In this report, the key accomplishment achieved during the second year (2008) of the program is summarized. The activities of this year include final selection of multicomponent thermodynamics and mobility databases, precipitate surface energy determination from nucleation experiment, multiscale comparison of predicted versus measured intragrain precipitation microstructure in quench samples showing good agreement, isothermal coarsening experiment and interaction of grain boundary and intergrain precipitates, primary microstructure of subsolvus treatment, and finally the software implementation plan for the third year of the project. In the following year, the calibrated models and simulation tools will be validated against an independently developed experimental data set, with actual disc heat treatment process conditions. Furthermore, software integration and implementation will be developed to provide material engineers valuable information in order to optimize the processing of the 3rd generation gas turbine disc alloys.

Correlations induced by depressing synapses in critically self-organized networks with quenched dynamics

NASA Astrophysics Data System (ADS)

Campos, João Guilherme Ferreira; Costa, Ariadne de Andrade; Copelli, Mauro; Kinouchi, Osame

2017-04-01

In a recent work, mean-field analysis and computer simulations were employed to analyze critical self-organization in networks of excitable cellular automata where randomly chosen synapses in the network were depressed after each spike (the so-called annealed dynamics). Calculations agree with simulations of the annealed version, showing that the nominal branching ratio σ converges to unity in the thermodynamic limit, as expected of a self-organized critical system. However, the question remains whether the same results apply to the biological case where only the synapses of firing neurons are depressed (the so-called quenched dynamics). We show that simulations of the quenched model yield significant deviations from σ =1 due to spatial correlations. However, the model is shown to be critical, as the largest eigenvalue of the synaptic matrix approaches unity in the thermodynamic limit, that is, λc=1 . We also study the finite size effects near the critical state as a function of the parameters of the synaptic dynamics.

Turbulent scalar flux transport in head-on quenching of turbulent premixed flames: a direct numerical simulations approach to assess models for Reynolds averaged Navier Stokes simulations

NASA Astrophysics Data System (ADS)

Lai, Jiawei; Alwazzan, Dana; Chakraborty, Nilanjan

2017-11-01

The statistical behaviour and the modelling of turbulent scalar flux transport have been analysed using a direct numerical simulation (DNS) database of head-on quenching of statistically planar turbulent premixed flames by an isothermal wall. A range of different values of Damköhler, Karlovitz numbers and Lewis numbers has been considered for this analysis. The magnitudes of the turbulent transport and mean velocity gradient terms in the turbulent scalar flux transport equation remain small in comparison to the pressure gradient, molecular dissipation and reaction-velocity fluctuation correlation terms in the turbulent scalar flux transport equation when the flame is away from the wall but the magnitudes of all these terms diminish and assume comparable values during flame quenching before vanishing altogether. It has been found that the existing models for the turbulent transport, pressure gradient, molecular dissipation and reaction-velocity fluctuation correlation terms in the turbulent scalar flux transport equation do not adequately address the respective behaviours extracted from DNS data in the near-wall region during flame quenching. Existing models for transport equation-based closures of turbulent scalar flux have been modified in such a manner that these models provide satisfactory prediction both near to and away from the wall.

Effect of Various Heat Treatment Processes on Fatigue Behavior of Tool Steel for Cold Forging Die

NASA Astrophysics Data System (ADS)

Jin, S. U.; Kim, S. S.; Lee, Y. S.; Kwon, Y. N.; Lee, J. H.

Effects of various heat treatment processes, including "Q/T (quenching and tempering)", "Q/CT/T (Quenching, cryogenic treatment and tempering)", "Q/T (quenching and tempering) + Ti-nitriding" and "Q/CT/T (Cryogenic treatment and tempering) + Ti-nitriding", on S-N fatigue behavior of AISI D2 tool steel were investigated. The optical micrographs and Vicker's hardness values at near surface and core area were examined for each specimen. Uniaxial fatigue tests were performed by using an electro-magnetic resonance fatigue testing machine at a frequency of 80 Hz and an R ratio of -1. The overall resistance to fatigue tends to decrease significantly with Ti-nitriding treatment compared to those for the general Q/T and Q/CT/T specimens. The reduced resistance to fatigue with Ti-nitriding is discussed based on the microstructural and fractographic analyses.

Understanding Uncertainties and Biases in Jet Quenching in High-Energy Nucleus-Nucleus Collisions

NASA Astrophysics Data System (ADS)

Heinz, Matthias

2017-09-01

Jets are the collimated streams of particles resulting from hard scattering in the initial state of high-energy collisions. In heavy-ion collisions, jets interact with the quark-gluon plasma (QGP) before freezeout, providing a probe into the internal structure and properties of the QGP. In order to study jets, background must be subtracted from the measured event, potentially introducing a bias. We aim to understand quantify this subtraction bias. PYTHIA, a library to simulate pure jet events, is used to simulate a model for a signature with one pure jet (a photon) and one quenched jet, where all quenched particle momenta are reduced by the same fraction. Background for the event is simulated using multiplicity values generated by the TRENTO initial state model of heavy-ion collisions fed into a thermal model from which to sample particle types and a 3-dimensional Boltzmann distribution from which to sample particle momenta. Data from the simulated events is used to train a statistical model, which computes a posterior distribution of the quench factor for a data set. The model was tested first on pure jet events and later on full events including the background. This model will allow for a quantitative determination of biases induced by various methods of background subtraction. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Disruption of Giant Molecular Clouds by Massive Star Clusters

NASA Astrophysics Data System (ADS)

Harper-Clark, Elizabeth

The lifetime of a Giant Molecular Cloud (GMC) and the total mass of stars that form within it are crucial to the understanding of star formation rates across a whole galaxy. In particular, the stars within a GMC may dictate its disruption and the quenching of further star formation. Indeed, observations show that the Milky Way contains GMCs with extensive expanding bubbles while the most massive stars are still alive. Simulating entire GMCs is challenging, due to the large variety of physics that needs to be included, and the computational power required to accurately simulate a GMC over tens of millions of years. Using the radiative-magneto-hydrodynamic code Enzo, I have run many simulations of GMCs. I obtain robust results for the fraction of gas converted into stars and the lifetimes of the GMCs: (A) In simulations with no stellar outputs (or "feedback''), clusters form at a rate of 30% of GMC mass per free fall time; the GMCs were not disrupted but contained forming stars. (B) Including ionization gas pressure or radiation pressure into the simulations, both separately and together, the star formation was quenched at between 5% and 21% of the original GMC mass. The clouds were fully disrupted within two dynamical times after the first cluster formed. The radiation pressure contributed the most to the disruption of the GMC and fully quenched star formation even without ionization. (C) Simulations that included supernovae showed that they are not dynamically important to GMC disruption and have only minor effects on subsequent star formation. (D) The inclusion of a few micro Gauss magnetic field across the cloud slightly reduced the star formation rate but accelerated GMC disruption by reducing bubble shell disruption and leaking. These simulations show that new born stars quench further star formation and completely disrupt the parent GMC. The low star formation rate and the short lifetimes of GMCs shown here can explain the low star formation rate across the whole galaxy.

Relationship between locked modes and thermal quenches in DIII-D

DOE PAGES

Sweeney, R.; Choi, W.; Austin, M.; ...

2018-03-28

Locked modes are known to be one of the major causes of disruptions, but the physical mechanisms by which locking leads to disruptions are not well understood. For this study, we analyze the evolution of the temperature profile in the presence of multiple coexisting locked modes during partial and full thermal quenches. Partial quenches are often observed to be an initial, distinct stage in the full thermal quench. Near the onset of partial quenches, locked island O-points are observed to align with each other on the midplane, and their widths are sufficient to overlap each other, as indicated by themore » Chirikov parameter. Energy conservation analysis of one partial thermal quench shows that the energy lost is both radiated in the divertor region, and conducted or convected to the divertor. Nonlinear resistive magnetohydrodynamic simulations support the interpretation of stochastic fields causing a partial axisymmetric collapse, though the simulated temperature profile exhibits less degradation than the experimental profiles. In discharges with minimum values of the safety factor above ~1.2, locked modes are observed to self-stabilize by inducing, possibly via double tearing modes, a minor disruption that removes their neoclassical drive. These high q min discharges often exhibit relatively low ratios of the plasma internal inductance to the safety factor at 95% of the poloidal flux, which might imply classical stability, in agreement with the decay of the mode when the neoclassical drive is removed.« less

Relationship between locked modes and thermal quenches in DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sweeney, R.; Choi, W.; Austin, M.

Locked modes are known to be one of the major causes of disruptions, but the physical mechanisms by which locking leads to disruptions are not well understood. For this study, we analyze the evolution of the temperature profile in the presence of multiple coexisting locked modes during partial and full thermal quenches. Partial quenches are often observed to be an initial, distinct stage in the full thermal quench. Near the onset of partial quenches, locked island O-points are observed to align with each other on the midplane, and their widths are sufficient to overlap each other, as indicated by themore » Chirikov parameter. Energy conservation analysis of one partial thermal quench shows that the energy lost is both radiated in the divertor region, and conducted or convected to the divertor. Nonlinear resistive magnetohydrodynamic simulations support the interpretation of stochastic fields causing a partial axisymmetric collapse, though the simulated temperature profile exhibits less degradation than the experimental profiles. In discharges with minimum values of the safety factor above ~1.2, locked modes are observed to self-stabilize by inducing, possibly via double tearing modes, a minor disruption that removes their neoclassical drive. These high q min discharges often exhibit relatively low ratios of the plasma internal inductance to the safety factor at 95% of the poloidal flux, which might imply classical stability, in agreement with the decay of the mode when the neoclassical drive is removed.« less

Manual for the Jet Event and Background Simulation Library(JEBSimLib)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinz, Matthias; Soltz, Ron; Angerami, Aaron

Jets are the collimated streams of particles resulting from hard scattering in the initial state of high-energy collisions. In heavy-ion collisions, jets interact with the quark-gluon plasma (QGP) before freezeout, providing a probe into the internal structure and properties of the QGP. In order to study jets, background must be subtracted from the measured event, potentially introducing a bias. We aim to understand and quantify this subtraction bias. PYTHIA, a library to simulate pure jet events, is used to simulate a model for a signature with one pure jet (a photon) and one quenched jet, where all quenched particle momentamore » are reduced by a user-de ned constant fraction. Background for the event is simulated using multiplicity values generated by the TRENTO initial state model of heavy-ion collisions fed into a thermal model consisting of a 3-dimensional Boltzmann distribution for particle types and momenta. Data from the simulated events is used to train a statistical model, which computes a posterior distribution of the quench factor for a data set. The model was tested rst on pure jet events and then on full events including the background. This model will allow for a quantitative determination of biases induced by various methods of background subtraction.« less

Manual for the Jet Event and Background Simulation Library

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinz, M.; Soltz, R.; Angerami, A.

Jets are the collimated streams of particles resulting from hard scattering in the initial state of high-energy collisions. In heavy-ion collisions, jets interact with the quark-gluon plasma (QGP) before freezeout, providing a probe into the internal structure and properties of the QGP. In order to study jets, background must be subtracted from the measured event, potentially introducing a bias. We aim to understand and quantify this subtraction bias. PYTHIA, a library to simulate pure jet events, is used to simulate a model for a signature with one pure jet (a photon) and one quenched jet, where all quenched particle momentamore » are reduced by a user-de ned constant fraction. Background for the event is simulated using multiplicity values generated by the TRENTO initial state model of heavy-ion collisions fed into a thermal model consisting of a 3-dimensional Boltzmann distribution for particle types and momenta. Data from the simulated events is used to train a statistical model, which computes a posterior distribution of the quench factor for a data set. The model was tested rst on pure jet events and then on full events including the background. This model will allow for a quantitative determination of biases induced by various methods of background subtraction.« less

Investigating structure-property relationships of biomineralized calcium phosphate compounds as fluorescent quenching-recovery platform

NASA Astrophysics Data System (ADS)

Wang, Liuzheng; He, Xiang; Zhang, Wei; Liu, Yong; Banks, Craig E.; Zhang, Ying

2018-02-01

The structure-property relationship between biomineralized calcium phosphate compounds upon a fluorescent quenching-recovery platform and their distinct crystalline structure and surficial functional groups are investigated. A fluorescence-based sensing platform is shown to be viable for the sensing of 8-hydroxy-2-deoxy-guanosine in simulated systems.

Finite Element Simulation and Experimental Verification of Internal Stress of Quenched AISI 4140 Cylinders

NASA Astrophysics Data System (ADS)

Liu, Yu; Qin, Shengwei; Hao, Qingguo; Chen, Nailu; Zuo, Xunwei; Rong, Yonghua

2017-03-01

The study of internal stress in quenched AISI 4140 medium carbon steel is of importance in engineering. In this work, the finite element simulation (FES) was employed to predict the distribution of internal stress in quenched AISI 4140 cylinders with two sizes of diameter based on exponent-modified (Ex-Modified) normalized function. The results indicate that the FES based on Ex-Modified normalized function proposed is better consistent with X-ray diffraction measurements of the stress distribution than FES based on normalized function proposed by Abrassart, Desalos and Leblond, respectively, which is attributed that Ex-Modified normalized function better describes transformation plasticity. Effect of temperature distribution on the phase formation, the origin of residual stress distribution and effect of transformation plasticity function on the residual stress distribution were further discussed.

Test of quantum thermalization in the two-dimensional transverse-field Ising model

PubMed Central

Blaß, Benjamin; Rieger, Heiko

2016-01-01

We study the quantum relaxation of the two-dimensional transverse-field Ising model after global quenches with a real-time variational Monte Carlo method and address the question whether this non-integrable, two-dimensional system thermalizes or not. We consider both interaction quenches in the paramagnetic phase and field quenches in the ferromagnetic phase and compare the time-averaged probability distributions of non-conserved quantities like magnetization and correlation functions to the thermal distributions according to the canonical Gibbs ensemble obtained with quantum Monte Carlo simulations at temperatures defined by the excess energy in the system. We find that the occurrence of thermalization crucially depends on the quench parameters: While after the interaction quenches in the paramagnetic phase thermalization can be observed, our results for the field quenches in the ferromagnetic phase show clear deviations from the thermal system. These deviations increase with the quench strength and become especially clear comparing the shape of the thermal and the time-averaged distributions, the latter ones indicating that the system does not completely lose the memory of its initial state even for strong quenches. We discuss our results with respect to a recently formulated theorem on generalized thermalization in quantum systems. PMID:27905523

Generative Models in Deep Learning: Constraints for Galaxy Evolution

NASA Astrophysics Data System (ADS)

Turp, Maximilian Dennis; Schawinski, Kevin; Zhang, Ce; Weigel, Anna K.

2018-01-01

New techniques are essential to make advances in the field of galaxy evolution. Recent developments in the field of artificial intelligence and machine learning have proven that these tools can be applied to problems far more complex than simple image recognition. We use these purely data driven approaches to investigate the process of star formation quenching. We show that Variational Autoencoders provide a powerful method to forward model the process of galaxy quenching. Our results imply that simple changes in specific star formation rate and bulge to disk ratio cannot fully describe the properties of the quenched population.

Kinetic Monte Carlo simulations of excitation density dependent scintillation in CsI and CsI(Tl)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhiguo; Williams, Richard; Grim, Joel

2013-08-15

Nonlinear quenching of electron-hole pairs in the denser regions of ionization tracks created by γ-ray and high-energy electrons is a likely cause of the light yield nonproportionality of many inorganic scintillators. Therefore, kinetic Monte Carlo (KMC) simulations were carried out to investigate the scintillation properties of pure and thallium-doped CsI as a function of electron-hole pair density. The availability of recent experimental data on the excitation density dependence of the light yield of CsI following ultraviolet excitation allowed for an improved parameterization of the interactions between self-trapped excitons (STE) in the KMC model via dipole-dipole Förster transfer. The KMC simulationsmore » reveal that nonlinear quenching occurs very rapidly (within a few picoseconds) in the early stages of the scintillation process. In addition, the simulations predict that the concentration of thallium activators can affect the extent of nonlinear quenching as it has a direct influence on the STE density through STE dissociation and electron scavenging. This improved model will enable more realistic simulations of the nonproportional γ-ray and electron response of inorganic scintillators.« less

The metal enrichment of passive galaxies in cosmological simulations of galaxy formation

NASA Astrophysics Data System (ADS)

Okamoto, Takashi; Nagashima, Masahiro; Lacey, Cedric G.; Frenk, Carlos S.

2017-02-01

Massive early-type galaxies have higher metallicities and higher ratios of α elements to iron than their less massive counterparts. Reproducing these correlations has long been a problem for hierarchical galaxy formation theory, both in semi-analytic models and cosmological hydrodynamic simulations. We show that a simulation in which gas cooling in massive dark haloes is quenched by radio-mode active galactic nuclei (AGNs) feedback naturally reproduces the observed trend between α/Fe and the velocity dispersion of galaxies, σ. The quenching occurs earlier for more massive galaxies. Consequently, these galaxies complete their star formation before α/Fe is diluted by the contribution from Type Ia supernovae. For galaxies more massive than ˜1011 M⊙, whose α/Fe correlates positively with stellar mass, we find an inversely correlated mass-metallicity relation. This is a common problem in simulations in which star formation in massive galaxies is quenched either by quasar- or radio-mode AGN feedback. The early suppression of gas cooling in progenitors of massive galaxies prevents them from recapturing enriched gas ejected as winds. Simultaneously reproducing the [α/Fe]-σ relation and the mass-metallicity relation is, thus, difficult in the current framework of galaxy formation.

Quench Crack Behavior of Nickel-base Disk Superalloys

NASA Technical Reports Server (NTRS)

Gayda, John; Kantzos, Pete; Miller, Jason

2002-01-01

There is a need to increase the temperature capability of superalloy turbine disks to allow higher operating temperatures in advanced aircraft engines. When modifying processing and chemistry of disk alloys to achieve this capability, it is important to preserve the ability to use rapid cooling during supersolvus heat treatments to achieve coarse grain, fine gamma prime microstructures. An important step in this effort is an understanding of the key variables controlling the cracking tendencies of nickel-base disk alloys during quenching from supersolvus heat treatments. The objective of this study was to investigate the quench cracking tendencies of several advanced disk superalloys during simulated heat treatments. Miniature disk specimens were rapidly quenched after solution heat treatments. The responses and failure modes were compared and related to the quench cracking tendencies of actual disk forgings. Cracking along grain boundaries was generally observed to be operative. For the alloys examined in this study, the solution temperature not alloy chemistry was found to be the primary factor controlling quench cracking. Alloys with high solvus temperatures show greater tendency for quench cracking.

Environmental quenching of low-mass field galaxies

NASA Astrophysics Data System (ADS)

Fillingham, Sean P.; Cooper, Michael C.; Boylan-Kolchin, Michael; Bullock, James S.; Garrison-Kimmel, Shea; Wheeler, Coral

2018-07-01

In the local Universe, there is a strong division in the star-forming properties of low-mass galaxies, with star formation largely ubiquitous amongst the field population while satellite systems are predominantly quenched. This dichotomy implies that environmental processes play the dominant role in suppressing star formation within this low-mass regime (M⋆ ˜ 105.5-8 M⊙). As shown by observations of the Local Volume, however, there is a non-negligible population of passive systems in the field, which challenges our understanding of quenching at low masses. By applying the satellite quenching models of Fillingham et al. (2015) to subhalo populations in the Exploring the Local Volume In Simulations suite, we investigate the role of environmental processes in quenching star formation within the nearby field. Using model parameters that reproduce the satellite quenched fraction in the Local Group, we predict a quenched fraction - due solely to environmental effects - of ˜0.52 ± 0.26 within 1 < R/Rvir < 2 of the Milky Way and M31. This is in good agreement with current observations of the Local Volume and suggests that the majority of the passive field systems observed at these distances are quenched via environmental mechanisms. Beyond 2Rvir, however, dwarf galaxy quenching becomes difficult to explain through an interaction with either the Milky Way or M31, such that more isolated, field dwarfs may be self-quenched as a result of star-formation feedback.

Modeling the formation of the quench product in municipal solid waste incineration (MSWI) bottom ash.

PubMed

Inkaew, Kanawut; Saffarzadeh, Amirhomayoun; Shimaoka, Takayuki

2016-06-01

This study investigated changes in bottom ash morphology and mineralogy under lab-scale quenching conditions. The main purpose was to clarify the mechanisms behind the formation of the quench product/layer around bottom ash particles. In the experiments, the unquenched bottom ashes were heated to 300°C for 1h, and were quenched by warm water (65°C) with different simulated conditions. After having filtered and dried, the ashes were analyzed by a combination of methodologies namely, particle size distribution analysis, intact particle and thin-section observation, X-ray diffractometry, and scanning electron microscope with energy dispersive X-ray spectroscopy. The results indicated that after quenching, the morphology and mineralogy of the bottom ash changed significantly. The freshly quenched bottom ash was dominated by a quench product that was characterized by amorphous and microcrystalline calcium-silicate-hydrate (CSH) phases. This product also enclosed tiny minerals, glasses, ceramics, metals, and organic materials. The dominant mineral phases produced by quenching process and detected by XRD were calcite, Friedel's salt, hydrocalumite and portlandite. The formation of quench product was controlled by the fine fraction of the bottom ash (particle size <0.425mm). From the observations, a conceptual model of the ash-water reactions and formation of the quench product in the bottom ash was proposed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Environmental Quenching of Low-Mass Field Galaxies

NASA Astrophysics Data System (ADS)

Fillingham, Sean P.; Cooper, Michael C.; Boylan-Kolchin, Michael; Bullock, James S.; Garrison-Kimmel, Shea; Wheeler, Coral

2018-04-01

In the local Universe, there is a strong division in the star-forming properties of low-mass galaxies, with star formation largely ubiquitous amongst the field population while satellite systems are predominantly quenched. This dichotomy implies that environmental processes play the dominant role in suppressing star formation within this low-mass regime (M⋆ ˜ 105.5 - 8 M⊙). As shown by observations of the Local Volume, however, there is a non-negligible population of passive systems in the field, which challenges our understanding of quenching at low masses. By applying the satellite quenching models of Fillingham et al. (2015) to subhalo populations in the Exploring the Local Volume In Simulations (ELVIS) suite, we investigate the role of environmental processes in quenching star formation within the nearby field. Using model parameters that reproduce the satellite quenched fraction in the Local Group, we predict a quenched fraction - due solely to environmental effects - of ˜0.52 ± 0.26 within 1 < R/Rvir < 2 of the Milky Way and M31. This is in good agreement with current observations of the Local Volume and suggests that the majority of the passive field systems observed at these distances are quenched via environmental mechanisms. Beyond 2 Rvir, however, dwarf galaxy quenching becomes difficult to explain through an interaction with either the Milky Way or M31, such that more isolated, field dwarfs may be self-quenched as a result of star-formation feedback.

NASA MSFC Electrostatic Levitator (ESL) Rapid Quench System

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Craven, Paul D.

2014-01-01

Electrostatic levitation, a form of containerless processing, is an important tool in materials research. Levitated specimens are free from contact with a container; therefore, heterogeneous nucleation on container walls is not possible. This allows studies of deeply undercooled melts. Furthermore, studies of high-temperature, highly reactive materials are also possible. Studies of the solidification and crystallization of undercooled melts is vital to the understanding of microstructure development, particularly the formation of alloys with unique properties by rapid solidification. The NASA Marshall Space Flight Center (MSFC) Electrostatic Levitator (ESL) lab has recently been upgraded to allow for rapid quenching of levitated materials. The ESL Rapid Quench System uses a small crucible-like vessel that can be partially filled with a low melting point material, such as a Gallium alloy, as a quench medium. An undercooled sample can be dropped into the vessel to rapidly quench the sample. A carousel with nine vessels sits below the bottom electrode assembly. This system allows up to nine rapid quenches before having to break vacuum and remove the vessels. This new Rapid Quench System will allow materials science studies of undercooled materials and new materials development. In this presentation, the system is described and initial results are presented.

Non-kinematic Flux-transport Dynamos Including the Effects of Diffusivity Quenching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ichimura, Chiaki; Yokoyama, Takaaki

2017-04-10

Turbulent magnetic diffusivity is quenched when strong magnetic fields suppress turbulent motion in a phenomenon known as diffusivity quenching. Diffusivity quenching can provide a mechanism for amplifying magnetic field and influencing global velocity fields through Lorentz force feedback. To investigate this effect, we conducted mean field flux-transport dynamo simulations that included the effects of diffusivity quenching in a non-kinematic regime. We found that toroidal magnetic field strength is amplified by up to approximately 1.5 times in the convection zone as a result of diffusivity quenching. This amplification is much weaker than that in kinematic cases as a result of Lorentzmore » force feedback on the system’s differential rotation. While amplified toroidal fields lead to the suppression of equatorward meridional flow locally near the base of the convection zone, large-scale equatorward transport of magnetic flux via meridional flow, which is the essential process of the flux-transport dynamo, is sustainable in our calculations.« less

Compressive properties of post-fire strain hardening cementitious composites

NASA Astrophysics Data System (ADS)

Yu, Dianyou; Xu, Zhichao; Liu, Yingchun

2018-03-01

In present research, the influence of post-fire curing methods on the mechanical properties of fire-damaged UHTCC was investigated. A heating temperature up to 800°C and lasting for 2 hours was adopted to simulate the fire damage, after which, the heated specimens were subjected to three types of cooling regimes (i.e., 1.cooling in air, 2. quenching in water for 5 minutes, and 3. quenching in water for 30 minutes). It was found that quenching in water helped the recovery of the compressive properties of UHTCC.

Convective Dynamics and Disequilibrium Chemistry in the Atmospheres of Giant Planets and Brown Dwarfs

NASA Astrophysics Data System (ADS)

Bordwell, Baylee; Brown, Benjamin P.; Oishi, Jeffrey S.

2018-02-01

Disequilibrium chemical processes significantly affect the spectra of substellar objects. To study these effects, dynamical disequilibrium has been parameterized using the quench and eddy diffusion approximations, but little work has been done to explore how these approximations perform under realistic planetary conditions in different dynamical regimes. As a first step toward addressing this problem, we study the localized, small-scale convective dynamics of planetary atmospheres by direct numerical simulation of fully compressible hydrodynamics with reactive tracers using the Dedalus code. Using polytropically stratified, plane-parallel atmospheres in 2D and 3D, we explore the quenching behavior of different abstract chemical species as a function of the dynamical conditions of the atmosphere as parameterized by the Rayleigh number. We find that in both 2D and 3D, chemical species quench deeper than would be predicted based on simple mixing-length arguments. Instead, it is necessary to employ length scales based on the chemical equilibrium profile of the reacting species in order to predict quench points and perform chemical kinetics modeling in 1D. Based on the results of our simulations, we provide a new length scale, derived from the chemical scale height, that can be used to perform these calculations. This length scale is simple to calculate from known chemical data and makes reasonable predictions for our dynamical simulations.

Variational method for lattice spectroscopy with ghosts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burch, Tommy; Hagen, Christian; Gattringer, Christof

2006-01-01

We discuss the variational method used in lattice spectroscopy calculations. In particular we address the role of ghost contributions which appear in quenched or partially quenched simulations and have a nonstandard euclidean time dependence. We show that the ghosts can be separated from the physical states. Our result is illustrated with numerical data for the scalar meson.

Investigation of Kibble-Zurek Quench Dynamics in a Spin-1 Ferromagnetic BEC

NASA Astrophysics Data System (ADS)

Anquez, Martin; Robbins, Bryce; Hoang, Thai; Yang, Xiaoyun; Land, Benjamin; Hamley, Christopher; Chapman, Michael

2014-05-01

We study the temporal evolution of spin populations in small spin-1 87Rb condensates following a slow quench. A ferromagnetic spin-1 BEC exhibits a second-order gapless (quantum) phase transition due to a competition between the magnetic and collisional spin interaction energies. The dynamics of slow quenches through the critical point are predicted to exhibit universal power-law scaling as a function of quench speed. In spatially extended condensates, these excitations are revealed as spatial spin domains. In small condensates, the excitations are manifest in the temporal evolution of the spin populations, illustrating a Kibble-Zurek type scaling. We will present the results of our investigation and compare them to full quantum simulations of the system.

Experimental, computational and chemometrics studies of BSA-vitamin B6 interaction by UV-Vis, FT-IR, fluorescence spectroscopy, molecular dynamics simulation and hard-soft modeling methods.

PubMed

Manouchehri, Firouzeh; Izadmanesh, Yahya; Aghaee, Elham; Ghasemi, Jahan B

2016-10-01

The interaction of pyridoxine (Vitamin B6) with bovine serum albumin (BSA) is investigated under pseudo-physiological conditions by UV-Vis, fluorescence and FTIR spectroscopy. The intrinsic fluorescence of BSA was quenched by VB6, which was rationalized in terms of the static quenching mechanism. According to fluorescence quenching calculations, the bimolecular quenching constant (kq), dynamic quenching (KSV) and static quenching (KLB) at 310K were obtained. The efficiency of energy transfer and the distance between the donor (BSA) and the acceptor (VB6) were calculated by Foster's non-radiative energy transfer theory and were equal to 41.1% and 2.11nm. The collected UV-Vis and fluorescence spectra were combined into a row-and column-wise augmented matrix and resolved by multivariate curve resolution-alternating least squares (MCR-ALS). MCR-ALS helped to estimate the stoichiometry of interactions, concentration profiles and pure spectra for three species (BSA, VB6 and VB6-BSA complex) existed in the interaction procedure. Based on the MCR-ALS results, using mass balance equations, a model was developed and binding constant of complex was calculated using non-linear least squares curve fitting. FT-IR spectra showed that the conformation of proteins was altered in presence of VB6. Finally, the combined docking and molecular dynamics (MD) simulations were used to estimate the binding affinity of VB6 to BSA. Five-nanosecond MD simulations were performed on bovine serum albumin (BSA) to study the conformational features of its ligand binding site. From MD results, eleven BSA snapshots were extracted, at every 0.5ns, to explore the binding affinity (GOLD score) of VB6 using a docking procedure. MD simulations indicated that there is a considerable flexibility in the structure of protein that affected ligand recognition. Structural analyses and docking simulations indicated that VB6 binds to site I and GOLD score values depend on the conformations of both BSA and ligand. Molecular modeling results showed that VB6-BSA complex formed not only on the basis of electrostatic forces, but also on the basis of π-π staking and hydrogen bond. There was an excellent agreement between the experimental and computational results. The results presented in this paper, will offer a reference for detailed and systematic studies on the biological effects and action mechanism of small molecules with proteins. Copyright © 2016 Elsevier Inc. All rights reserved.

(Talk) Investigating The Star Formation Quenching Across Cosmic Time - A Methodology To Select Galaxies Just After The Quenching Of Star Formation

NASA Astrophysics Data System (ADS)

Citro, Annalisa; Pozzetti, Lucia; Quai, Salvatore; Moresco, Michele; Vallini, Livia; Cimatti, Andrea

2017-06-01

We propose a method aimed at identifing galaxies in the short evolutionary phase in which they quench their star-formation (SF). We rely on high- to low-ionization emission line ratios, which rapidly disappear after the SF halt due to the softening of the UV ionizing radiation. In particular, we focus on [O III] 5007/Halpha and [Ne III] 3869/[O II] 3727, simulating their time evolution by means of the CLOUDY photoionization code. We find that these two emission line ratios are able to trace the quenching on very short time-scales (i.e. 10-80 Myr), depending on if a sharp or a smoother SF quenching is assumed. We adopt the [N II] 6584/[O II] 3727 ratio as metallicity diagnostic to mitigate the metallicity degeneracy which affects our method. Using a Sloan Digital Sky Survey galaxy sample, we identify 11 examples of extreme quenching candidates within the [O III] 5007/Halpha vs. [N II] 6584/[O II] 3727 plane, characterized by faint [Ne III] 3869, blue dust-corrected spectra and blue (u-r) colours, as expected if the quenching occurred in the recent past. Our results also suggest that the observed fractions of quenching candidates can be used to constrain the quenching mechanism at work and its time-scales.

EPS (Electric Particulate Suspension) Microgravity Technology Provides NASA with New Tools

NASA Technical Reports Server (NTRS)

Colver, Gerald M.; Greene, Nate; Xu, Hua

2004-01-01

The Electric Particulate Suspension is a fire safety ignition test system being developed at Iowa State University with NASA support for evaluating combustion properties of powders, powder-gas mixtures, and pure gases in microgravity and gravitational atmospheres (quenching distance, ignition energy, flammability limits). A separate application is the use of EPS technology to control heat transfer in vacuum and space environment enclosures. In combustion testing, ignitable powders (aluminum, magnesium) are introduced in the EPS test cell and ignited by spark, while the addition of inert particles act as quenching media. As a combustion research tool, the EPS method has potential as a benchmark design for quenching powder flames that would provide NASA with a new fire safety standard for powder ignition testing. The EPS method also supports combustion modeling by providing accurate measurement of flame-quenching distance as an important parameter in laminar flame theory since it is closely related to characteristic flame thickness and flame structure. In heat transfer applications, inert powder suspensions (copper, steel) driven by electric fields regulate heat flow between adjacent surfaces enclosures both in vacuum (or gas) and microgravity. This simple E-field control can be particularly useful in space environments where physical separation is a requirement between heat exchange surfaces.

N-Acyl Homoserine Lactone-Mediated Quorum Sensing with Special Reference to Use of Quorum Quenching Bacteria in Membrane Biofouling Control

PubMed Central

Paul, Diby

2014-01-01

Membrane biofouling remains a severe problem to be addressed in wastewater treatment systems affecting reactor performance and economy. The finding that many wastewater bacteria rely on N-acyl homoserine lactone-mediated quorum sensing to synchronize their activities essential for biofilm formations; the quenching bacterial quorum sensing suggests a promising approach for control of membrane biofouling. A variety of quorum quenching compounds of both synthetic and natural origin have been identified and found effective in inhibition of membrane biofouling with much less environmental impact than traditional antimicrobials. Work over the past few years has demonstrated that enzymatic quorum quenching mechanisms are widely conserved in several prokaryotic organisms and can be utilized as a potent tool for inhibition of membrane biofouling. Such naturally occurring bacterial quorum quenching mechanisms also play important roles in microbe-microbe interactions and have been used to develop sustainable nonantibiotic antifouling strategies. Advances in membrane fabrication and bacteria entrapment techniques have allowed the implication of such quorum quenching bacteria for better design of membrane bioreactor with improved antibiofouling efficacies. In view of this, the present paper is designed to review and discuss the recent developments in control of membrane biofouling with special emphasis on quorum quenching bacteria that are applied in membrane bioreactors. PMID:25147787

Quantum quenches in two spatial dimensions using chain array matrix product states

DOE PAGES

A. J. A. James; Konik, R.

2015-10-15

We describe a method for simulating the real time evolution of extended quantum systems in two dimensions (2D). The method combines the benefits of integrability and matrix product states in one dimension to avoid several issues that hinder other applications of tensor based methods in 2D. In particular, it can be extended to infinitely long cylinders. As an example application we present results for quantum quenches in the 2D quantum [(2+1)-dimensional] Ising model. As a result, in quenches that cross a phase boundary we find that the return probability shows nonanalyticities in time.

Early structural development in melt-quenched polymer PTT from atomistic molecular dynamic simulations

NASA Astrophysics Data System (ADS)

Hsieh, Min-Kang; Lin, Shiang-Tai

2009-12-01

Molecular dynamics simulations are performed to study the initial structural development in poly(trimethylene terephthalate) (PTT) when quenched below its melting point. The development of local ordering has been observed in our simulations. The thermal properties, such as the glass transition temperature (Tg) and the melting temperature (Tm), determined from our simulations are in reasonable agreement with experimental values. It is found that, between these two temperatures, the number of local structures quickly increases during the thermal relaxation period soon after the system is quenched and starts to fluctuate afterwards. The formation and development of local structures is found to be driven mainly by the torsional and van der Waals forces and follows the classical nucleation-growth mechanism. The variation of local structures' fraction with temperature exhibits a maximum between Tg and Tm, resembling the temperature dependence of the crystallization rate for most polymers. In addition, the backbone torsion distribution for segments within the local structures preferentially reorganizes to the trans-gauche-gauche-trans (t-g-g-t) conformation, the same as that in the crystalline state. As a consequence, we believe that such local structural ordering could be the baby nuclei that have been suggested to form in the early stage of polymer crystallization.

Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

NASA Astrophysics Data System (ADS)

Wheeler, Coral Rose

We study dwarf satellite galaxy quenching using observations from the Geha et al. (2012) NSA/SDSS catalog together with CDM cosmological simulations to facilitate selection and interpretation. We show that fewer than 30% of dwarfs (M* ˜ 108.5-9.5 Msun ) identified as satellites within massive host halos (M host ˜ 1012.5-14 Msun) are quenched. We conclude that whatever the action triggering environmental quenching of dwarf satellites, the process must be highly inefficient. We investigate a series of simple, one-parameter quenching models in order to understand what is required to explain the low quenched fraction and conclude that either the quenching timescale is very long (> 9.5 Gyr, a "slow starvation" scenario) or that the environmental trigger is not well matched to accretion within the virial volume. We further present FIRE/Gizmo hydrodynamic zoom-in simulations of isolated dark matter halos, two each at the mass of classical dwarf galaxies (Mvir ˜ 1010 Msun) and ultra-faint galaxies (Mvir ˜ 10 9 Msun). The resulting central galaxies lie on an extrapolated abundance matching relation from M* ˜ 106 to 104 Msun without a break. Our dwarfs with M* ˜ 106 Msun each have 1-2 well-resolved satellites with M* = 3 - 200 x 103 Msun. Even our isolated ultra-faint galaxies have star-forming subhalos. We combine our results with the ELVIS simulations to show that targeting the ˜ 50 kpc regions around nearby isolated dwarfs could increase the chances of discovering ultra-faint galaxies by ˜35% compared to random pointings. The well-resolved ultra-faint galaxies in our simulations (M * ˜ 3 - 30 x 103 Msun) form within Mpeak ˜ 0.5 - 3 x 109 Msun halos. Each has a uniformly ancient stellar population (> 10 Gyr) owing to reionization-related quenching. More massive systems, in contrast, all have late-time star formation. Our results suggest that Mhalo ˜ 5 x 109 Msun is a probable dividing line between halos hosting reionization "fossils" and those hosting dwarfs that can continue to form stars in isolation after reionization. Finally, we perform a systematic Bayesian analysis of rotation vs. dispersion support (vrot/sigma) in 40 dwarf galaxies throughout the Local Volume (LV) over a stellar mass range 103.5 M sun < M* < 108 Msun. We find that the stars in 80% of the LV dwarf galaxies studied -- both satellites and isolated systems -- are dispersion-supported. These results challenge the traditional view that the stars in gas-rich dwarf irregulars (dIrrs) are distributed in cold, rotationally-supported stellar disks, while gas-poor dwarf spheroidals (dSphs) are kinematically distinct in having dispersion supported stars. We apply the same Bayesian analysis to four of the FIRE/Gizmo hydrodynamic zoom-in simulations of isolated dwarf galaxies (109 Msun < M vir < 1010 Msun) and show that the simulated isolated dIrr galaxies have stellar ellipticities and stellar vrot/sigma ratios that are consistent with the observed population of dIrrs and dSphs without the need to subject these dwarfs to any external perturbations or tidal forces. We posit that most dwarf galaxies form as puffy, dispersion-dominated systems, rather than cold, angular momentum-supported disks. If this is the case, then transforming a dIrr into a dSph may require little more than removing its gas.

Simulation of mixing in the quick quench region of a rich burn-quick quench mix-lean burn combustor

NASA Technical Reports Server (NTRS)

Shih, Tom I.-P.; Nguyen, H. Lee; Howe, Gregory W.; Li, Z.

1991-01-01

A computer program was developed to study the mixing process in the quick quench region of a rich burn-quick quench mix-lean burn combustor. The computer program developed was based on the density-weighted, ensemble-averaged conservation equations of mass, momentum (full compressible Navier-Stokes), total energy, and species, closed by a k-epsilon turbulence model with wall functions. The combustion process was modeled by a two-step global reaction mechanism, and NO(x) formation was modeled by the Zeldovich mechanism. The formulation employed in the computer program and the essence of the numerical method of solution are described. Some results obtained for nonreacting and reacting flows with different main-flow to dilution-jet momentum flux ratios are also presented.

Characterization and quenching of friction-induced limit cycles of electro-hydraulic servovalve control systems with transport delay.

PubMed

Wang, Yuan-Jay

2010-10-01

This paper develops a systematic and straightforward methodology to characterize and quench the friction-induced limit cycle conditions in electro-hydraulic servovalve control systems with transport delay in the transmission line. The nonlinear friction characteristic is linearized by using its corresponding describing function. The delay time in the transmission line, which could accelerate the generation of limit cycles is particularly considered. The stability equation method together with parameter plane method provides a useful tool for the establishment of necessary conditions to sustain a limit cycle directly in the constructed controller coefficient plane. Also, the stable region, the unstable region, and the limit cycle region are identified in the parameter plane. The parameter plane characterizes a clear relationship between limit cycle amplitude, frequency, transport delay, and the controller coefficients to be designed. The stability of the predicted limit cycle is checked by plotting stability curves. The stability of the system is examined when the viscous gain changes with respect to the temperature of the working fluid. A feasible stable region is characterized in the parameter plane to allow a flexible choice of controller gains. The robust prevention of limit cycle is achieved by selecting controller gains from the asymptotic stability region. The predicted results are verified by simulations. It is seen that the friction-induced limit cycles can be effectively predicted, removed, and quenched via the design of the compensator even in the case of viscous gain and delay time variations unconditionally. Copyright © 2010 ISA. Published by Elsevier Ltd. All rights reserved.

Confronting models of star formation quenching in galaxy clusters with archival Spitzer data

NASA Astrophysics Data System (ADS)

Rudnick, Gregory

Large scale structures in the universe form hierarchically: small structures merge to form larger ones. Over the same epoch where these structures experience significant growth, the fraction of star forming galaxies within them decreases, and at a faster rate than for field galaxies. It is now widely accepted that there must be physical processes at work in these dense environments to actively quench star formation. However, despite no shortage of candidate mechanisms, sophisticated cosmological simulations still cannot reproduce the star formation rate distributions within dense environments, such as galaxy clusters. Insufficient observational constraints are a primary obstacle to further progress. In particular, the interpretation of observations of nearby clusters relies on untested assumptions about the properties of galaxies before they entered the dense cluster environment at higher redshifts. Clearly, direct constraints on these properties are required. Our group has assembled two data sets designed to address these concerns. The first focuses on an intermediate wide-field cluster sample and the second focuses on a well-matched low-redshift cluster sample. We will use these samples, along with sophisticated models of hierarchical galaxy formation, to meet the following objectives: 1. Directly measure the SFR distribution of the progenitors of present-day cluster galaxies. We will use ground-based spectroscopy to identify cluster members within four virial radii of eight intermediate-redshift clusters. We will couple this with archival Spitzer/MIPS data to measure the SFRs of galaxies out to the cluster outskirts. 2. Measure the SFR distribution of the present-day cluster galaxies using Spitzer and WISE. Robust N-body simulations tell us statistically which galaxies at intermediate redshifts will have entered the cluster virial radius by the current epoch. By combining our wide-field coverage at high redshift with our local cluster sample, we will determine the evolution in cluster galaxy SFRs over 6 billion years making minimal assumptions about the infalling galaxy population. 3. Provide a rigorous test of the quenching processes embedded in the theoretical models. We will create observed realizations of the theoretical models by subjecting them to our observational selection. This will enable a fair comparison between the models and the data, which will provide a valuable test of current theoretical implementations of quenching processes. We will also modify the quenching prescriptions in the models to determine the parameters required to reproduce the observations. The proposed research is novel for several reasons. 1) We have wide-field Spitzer/MIPS data that allows us to robustly measure SFRs in our distant cluster galaxies. WISE data on local clusters will provide us with analogous measurements in the nearby Universe. 2) Our significant investment in ancillary spectroscopy allows us to identify infalling galaxies that will eventually join the central regions of the cluster z=0. 3) Our intermediate redshift cluster sample was chosen to have characteristics expected for the progenitors of a large fraction of the known clusters at z=0. 4) We will take advantage of our own cosmological simulations of structure growth to interpret our data. 5) We have optical photometry over the full infall region, allowing us to control for stellar masses and to distinguish passive from dusty star-forming galaxies. We will learn which, if any, of the quenching prescriptions currently employed in semi-analytic models correctly reproduces the observed characteristics of the galaxies that will become cluster galaxies at z=0. We will pinpoint the cluster-centric radii over which quenching takes place between. We will determine the timescale (as a function of stellar mass) over which it must take place. This program will cement the legacy of Spitzer and WISE as tools for studying galaxy formation in clusters.

Prediction, experimental results and analysis of the ITER TF insert coil quench propagation tests, using the 4C code

NASA Astrophysics Data System (ADS)

Zanino, R.; Bonifetto, R.; Brighenti, A.; Isono, T.; Ozeki, H.; Savoldi, L.

2018-07-01

The ITER toroidal field insert (TFI) coil is a single-layer Nb3Sn solenoid tested in 2016-2017 at the National Institutes for Quantum and Radiological Science and Technology (former JAEA) in Naka, Japan. The TFI, the last in a series of ITER insert coils, was tested in operating conditions relevant for the actual ITER TF coils, inserting it in the borehole of the central solenoid model coil, which provided the background magnetic field. In this paper, we consider the five quench propagation tests that were performed using one or two inductive heaters (IHs) as drivers; out of these, three used just one IH but with increasing delay times, up to 7.5 s, between the quench detection and the TFI current dump. The results of the 4C code prediction of the quench propagation up to the current dump are presented first, based on simulations performed before the tests. We then describe the experimental results, showing good reproducibility. Finally, we compare the 4C code predictions with the measurements, confirming the 4C code capability to accurately predict the quench propagation, and the evolution of total and local voltages, as well as of the hot spot temperature. To the best of our knowledge, such a predictive validation exercise is performed here for the first time for the quench of a Nb3Sn coil. Discrepancies between prediction and measurement are found in the evolution of the jacket temperatures, in the He pressurization and quench acceleration in the late phase of the transient before the dump, as well as in the early evolution of the inlet and outlet He mass flow rate. Based on the lessons learned in the predictive exercise, the model is then refined to try and improve a posteriori (i.e. in interpretive, as opposed to predictive mode) the agreement between simulation and experiment.

Evaluation of Microstructure and Toughness of AISI D2 Steel by Bright Hardening in Comparison with Oil Quenching

NASA Astrophysics Data System (ADS)

Torkamani, H.; Raygan, Sh.; Rassizadehghani, J.

2011-12-01

AISI D2 is used widely in the manufacture of blanking and cold-forming dies, on account of its excellent hardness and wear behavior. Increasing toughness at a fixed high level of hardness is growing requirement for this kind of tool steel. Improving microstructure characteristics, especially refinement of coarse carbides, is an appropriate way to meet such requirement. In this study, morphology and size of carbides in martensite matrix were compared between two kinds of samples, which were bright hardened (quenching in hot alkaline salt bath consisting of 60% KOH and 40% NaOH) at 230 °C and quenched in oil bath at 60 °C. Results showed that morphology and distribution of carbides in samples performed by bright hardening were finer and almost spherical compared to that of oil quenched. This microstructure resulted in an improvement in toughness and tensile properties of alloy.

The influence of containerless undercooling and rapid solid-state quenching on the superconductive and magnetic properties of some clustering alloy systems

NASA Technical Reports Server (NTRS)

Collings, E. W.

1984-01-01

The properties of clustering alloy systems and the manner in which they are influenced by rapid quenching from a containerless undercooled melt are discussed. It was postulated that rapid quenching under such conditions would result in highly disordered metastable alloys, and furthermore, that alloys in such conditions would possess physical properties characteristically different from those of alloys in the annealed equilibrium state. The scope of the program is essentially to gauge the influence of containerless undercooling on the submicrostructure of clustering-type alloys, using certain physical properties as diagnostic tools. Microstructures and macrostructures were to be examined using optical- and scanning-electron microscopy.

Quench-Induced Stresses in AA2618 Forgings for Impellers: A Multiphysics and Multiscale Problem

NASA Astrophysics Data System (ADS)

Chobaut, Nicolas; Saelzle, Peter; Michel, Gilles; Carron, Denis; Drezet, Jean-Marie

2015-05-01

In the fabrication of heat-treatable aluminum parts such as AA2618 compressor impellers for turbochargers, solutionizing and quenching are key steps to obtain the required mechanical characteristics. Fast quenching is necessary to avoid coarse precipitation as it reduces the mechanical properties obtained after heat treatment. However, fast quenching induces residual stresses that can cause unacceptable distortions during machining. Furthermore, the remaining residual stresses after final machining can lead to unfavorable stresses in service. Predicting and controlling internal stresses during the whole processing from heat treatment to final machining is therefore of particular interest to prevent negative impacts of residual stresses. This problem is multiphysics because processes such as heat transfer during quenching, precipitation phenomena, thermally induced deformations, and stress generation are interacting and need to be taken into account. The problem is also multiscale as precipitates of nanosize form during quenching at locations where the cooling rate is too low. This precipitation affects the local yield strength of the material and thus impacts the level of macroscale residual stresses. A thermomechanical model accounting for precipitation in a simple but realistic way is presented. Instead of modelling precipitation that occurs during quenching, the model parameters are identified using a limited number of tensile tests achieved after representative interrupted cooling paths in a Gleeble machine. The simulation results are compared with as-quenched residual stresses in a forging measured by neutron diffraction.

Mechanical stress analysis during a quench in CLIQ protected 16 T dipole magnets designed for the future circular collider

NASA Astrophysics Data System (ADS)

Zhao, Junjie; Prioli, Marco; Stenvall, Antti; Salmi, Tiina; Gao, Yuanwen; Caiffi, Barbara; Lorin, Clement; Marinozzi, Vittorio; Farinon, Stefania; Sorbi, Massimo

2018-07-01

Protecting the magnets in case of a quench is a challenge for the 16 T superconducting dipole magnets presently designed for the 100 TeV: Future Circular Collider (FCC). These magnets are driven to the foreseen technological limits in terms of critical current, mechanical strength and quench protection. The magnets are protected with CLIQ (Coupling-Loss Induced Quench) system, which is a recently developed quench protection method based on discharging a capacitor bank across part of the winding. The oscillation of the magnet currents and the dissipation of the high stored energy into the windings cause electrodynamic forces and thermal stresses, which may need to be considered in the magnet mechanical design. This paper focuses on mechanical stress analysis during a quench of the 16 T cos-θ and block type dipole magnets. A finite element model allowed studying the stress due to the non-uniform temperature and current distribution in the superconducting coils. Two different CLIQ configurations were considered for the cos-θ design and one for the block type magnet. The analyses of the mechanical behavior of two magnets during a quench without or with hot spot turn were separately carried out. The simulation results show that the stress related to a quench should be considered when designing a high field magnet.

Fluorescent Metal-Organic Framework (MOF) as a Highly Sensitive and Quickly Responsive Chemical Sensor for the Detection of Antibiotics in Simulated Wastewater.

PubMed

Zhu, Xian-Dong; Zhang, Kun; Wang, Yu; Long, Wei-Wei; Sa, Rong-Jian; Liu, Tian-Fu; Lü, Jian

2018-02-05

A Zn(II)-based fluorescent metal-organic framework (MOF) was synthesized and applied as a highly sensitive and quickly responsive chemical sensor for antibiotic detection in simulated wastewater. The fluorescent chemical sensor, denoted FCS-1, exhibited enhanced fluorescence derived from its highly ordered, 3D MOF structure as well as excellent water stability in the practical pH range of simulated antibiotic wastewater (pH = 3.0-9.0). Remarkably, FCS-1 was able to effectively detect a series of sulfonamide antibiotics via photoinduced electron transfer that caused detectable fluorescence quenching, with fairly low detection limits. Two influences impacting measurements related to wastewater treatment and water quality monitoring, the presence of heavy-metal ions and the pH of solutions, were studied in terms of fluorescence quenching, which was nearly unaffected in sulfonamide-antibiotic detection. Additionally, the effective detection of sulfonamide antibiotics was rationalized by the theoretical computation of the energy bands of sulfonamide antibiotics, which revealed a good match between the energy bands of FCS-1 and sulfonamide antibiotics, in connection with fluorescence quenching in this system.

Design of the superconducting magnet for 9.4 Tesla whole-body magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Li, Y.; Wang, Q.; Dai, Y.; Ni, Z.; Zhu, X.; Li, L.; Zhao, B.; Chen, S.

2017-02-01

A superconducting magnet for 9.4 Tesla whole-body magnetic resonance imaging is designed and fabricated in Institute of Electrical Engineering, Chinese Academy of Sciences. In this paper, the electromagnetic design methods of the main coils and compensating coils are presented. Sensitivity analysis is performed for all superconducting coils. The design of the superconducting shimming coils is also presented and the design of electromagnetic decoupling of the Z2 coils from the main coils is introduced. Stress and strain analysis with both averaged and detailed models is performed with finite element method. A quench simulation code with anisotropic continuum model and control volume method is developed by us and is verified by experimental study. By means of the quench simulation code, the quench protection system for the 9.4 T magnet is designed for the main coils, the compensating coils and the shimming coils. The magnet cryostat design with zero helium boiling-off technology is also introduced.

An analysis of the nucleon spectrum from lattice partially-quenched QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

W. Armour; Allton, C. R.; Leinweber, Derek B.

2010-09-01

The chiral extrapolation of the nucleon mass, Mn, is investigated using data coming from 2-flavour partially-quenched lattice simulations. The leading one-loop corrections to the nucleon mass are derived for partially-quenched QCD. A large sample of lattice results from the CP-PACS Collaboration is analysed, with explicit corrections for finite lattice spacing artifacts. The extrapolation is studied using finite range regularised chiral perturbation theory. The analysis also provides a quantitative estimate of the leading finite volume corrections. It is found that the discretisation, finite-volume and partial quenching effects can all be very well described in this framework, producing an extrapolated value ofmore » Mn in agreement with experiment. This procedure is also compared with extrapolations based on polynomial forms, where the results are less encouraging.« less

Effect of heat treatment On Microstructure of steel AISI 01 Tools

NASA Astrophysics Data System (ADS)

Dyanasari Sebayang, Melya; Yudo, Sesmaro Max; Silitonga, Charlie

2018-03-01

This study discusses the influence of quenching, normalizing, and annealing to changes in hardness, tensile, and microstructure of materials tool steel AISI 01 after the material undergo heat treatment process. This heat treatment process includes an initial warming of 600° C and a 5-minute detention time, followed by heating to an austenisation temperature of 850°C. After that a different cooling process, including annealing process, normalizing and quenching oil SAE 40. Tests performed include tensile, hard, and microstructure with shooting using SEM (Scanning Electron Microscope). This is done to see the effect of different heat treatment and cooling process. The result of this research is difference of tensile test value, hard, and micro structure from influence of difference of each process. The quenching process obtains the highest tensile and hard values followed by the normalizing process, annealing, and the lowest is in the starting material, this is because the initial material does not undergo heat treatment process. The resulting microstructure is pearlit and cementite, the difference seen from the shape and size of the grains. The larger the grain size, the greater the hardness.

Parallel Decomposition of the Fictitious Lagrangian Algorithm and its Accuracy for Molecular Dynamics Simulations of Semiconductors.

NASA Astrophysics Data System (ADS)

Yeh, Mei-Ling

We have performed a parallel decomposition of the fictitious Lagrangian method for molecular dynamics with tight-binding total energy expression into the hypercube computer. This is the first time in literature that the dynamical simulation of semiconducting systems containing more than 512 silicon atoms has become possible with the electrons treated as quantum particles. With the utilization of the Intel Paragon system, our timing analysis predicts that our code is expected to perform realistic simulations on very large systems consisting of thousands of atoms with time requirements of the order of tens of hours. Timing results and performance analysis of our parallel code are presented in terms of calculation time, communication time, and setup time. The accuracy of the fictitious Lagrangian method in molecular dynamics simulation is also investigated, especially the energy conservation of the total energy of ions. We find that the accuracy of the fictitious Lagrangian scheme in small silicon cluster and very large silicon system simulations is good for as long as the simulations proceed, even though we quench the electronic coordinates to the Born-Oppenheimer surface only in the beginning of the run. The kinetic energy of electrons does not increase as time goes on, and the energy conservation of the ionic subsystem remains very good. This means that, as far as the ionic subsystem is concerned, the electrons are on the average in the true quantum ground states. We also tie up some odds and ends regarding a few remaining questions about the fictitious Lagrangian method, such as the difference between the results obtained from the Gram-Schmidt and SHAKE method of orthonormalization, and differences between simulations where the electrons are quenched to the Born -Oppenheimer surface only once compared with periodic quenching.

Special features of the technology of boronizing steel in a calcium chloride melt

NASA Astrophysics Data System (ADS)

Chernov, Ya. B.; Anfinogenov, A. I.; Veselov, I. N.

1999-12-01

A technology for hardening machine parts and tools by boronizing in molten calcium chloride with amorphous-boron powder in electrode salt baths has been developed with the aim of creating a closed cycle of utilizing the raw materials and the washing water. A process of boronizing that includes quenching and tempering of the boronized articles is described. The quenching medium is an ecologically safe and readily available aqueous solution of calcium chloride. The process envisages return of the melt components to the boronizing bath. Boronizing by the suggested method was tested for different classes of steel, namely, structural and tool steels for cold and hot deformation. The wear resistance of the boronized steels was studied.

Thin Disk Accretion in the Magnetically-Arrested State

NASA Astrophysics Data System (ADS)

Avara, Mark J.; McKinney, Jonathan; Reynolds, Christopher S.

2016-01-01

Shakura-Sunyaev thin disk theory is fundamental to black hole astrophysics. Though applications of the theory are wide-spread and powerful tools for explaining observations, such as Soltan's argument using quasar power, broadened iron line measurements, continuum fitting, and recently reverberation mapping, a significant large-scale magnetic field causes substantial deviations from standard thin disk behavior. We have used fully 3D general relativistic MHD simulations with cooling to explore the thin (H/R~0.1) magnetically arrested disk (MAD) state and quantify these deviations. This work demonstrates that accumulation of large-scale magnetic flux into the MAD state is possible, and then extends prior numerical studies of thicker disks, allowing us to measure how jet power scales with the disk state, providing a natural explanation of phenomena like jet quenching in the high-soft state of X-ray binaries. We have also simulated thin MAD disks with a misaligned black hole spin axis in order to understand further deviations from thin disk theory that may significantly affect observations.

Efficient tomography of a quantum many-body system

NASA Astrophysics Data System (ADS)

Lanyon, B. P.; Maier, C.; Holzäpfel, M.; Baumgratz, T.; Hempel, C.; Jurcevic, P.; Dhand, I.; Buyskikh, A. S.; Daley, A. J.; Cramer, M.; Plenio, M. B.; Blatt, R.; Roos, C. F.

2017-12-01

Quantum state tomography is the standard technique for estimating the quantum state of small systems. But its application to larger systems soon becomes impractical as the required resources scale exponentially with the size. Therefore, considerable effort is dedicated to the development of new characterization tools for quantum many-body states. Here we demonstrate matrix product state tomography, which is theoretically proven to allow for the efficient and accurate estimation of a broad class of quantum states. We use this technique to reconstruct the dynamical state of a trapped-ion quantum simulator comprising up to 14 entangled and individually controlled spins: a size far beyond the practical limits of quantum state tomography. Our results reveal the dynamical growth of entanglement and describe its complexity as correlations spread out during a quench: a necessary condition for future demonstrations of better-than-classical performance. Matrix product state tomography should therefore find widespread use in the study of large quantum many-body systems and the benchmarking and verification of quantum simulators and computers.

Computational Thermodynamics Characterization of 7075, 7039, and 7020 Aluminum Alloys Using JMatPro

DTIC Science & Technology

2011-09-01

parameters of temperature and time may be selected to simulate effects on microstructure during annealing , solution treating, quenching, and tempering...nucleation may be taken into account by use of a wetting angle function. Activation energy may be taken into account for rapidly quenched alloys...the stable forms of precipitates that result from solutionizing, annealing or intermediate heat treatment, and phase formation during nonequilibrium

A journal bearing with variable geometry for the suppression of vibrations in rotating shafts: Simulation, design, construction and experiment

NASA Astrophysics Data System (ADS)

Chasalevris, Athanasios; Dohnal, Fadi

2015-02-01

The idea for a journal bearing with variable geometry was formerly developed and investigated on its principles of operation giving very optimistic theoretical results for the vibration quenching of simple and more complicated rotor bearing systems during the passage through the first critical speed. The journal bearing with variable geometry is presented in this paper in its final form with the detailed design procedure. The current journal bearing was constructed in order to be applied in a simple real rotor bearing system that already exists as an experimental facility. The current paper presents details on the manufactured prototype bearing as an experimental continuation of previous works that presented the simulation of the operating principle of this journal bearing. The design parameters are discussed thoroughly under the numerical simulation for the fluid film pressure in dependency of the variable fluid film thickness during the operation conditions. The implementation of the variable geometry bearing in an experimental rotor bearing system is outlined. Various measurements highlight the efficiency of the proposed bearing element in vibration quenching during the passage through resonance. The inspiration for the current idea is based on the fact that the alteration of the fluid film characteristics of stiffness and damping during the passage through resonance results in vibration quenching. This alteration of the bearing characteristics is achieved by the introduction of an additional fluid film thickness using the passive displacement of the lower half-bearing part. • The contribution of the current journal bearing in vibration quenching. • Experimental evidence for the VGJB contribution.

Acoustic emission during quench training of superconducting accelerator magnets

NASA Astrophysics Data System (ADS)

Marchevsky, M.; Sabbi, G.; Bajas, H.; Gourlay, S.

2015-07-01

Acoustic emission (AE) sensing is a viable tool for superconducting magnet diagnostics. Using in-house developed cryogenic amplified piezoelectric sensors, we conducted AE studies during quench training of the US LARP's high-field quadrupole HQ02 and the LBNL's high-field dipole HD3. For both magnets, AE bursts were observed, with spike amplitude and frequency increasing toward the quench current during current up-ramps. In the HQ02, the AE onset upon current ramping is distinct and exhibits a clear memory of the previously-reached quench current (Kaiser effect). On the other hand, in the HD3 magnet the AE amplitude begins to increase well before the previously-reached quench current (felicity effect), suggesting an ongoing progressive mechanical motion in the coils. A clear difference in the AE signature exists between the untrained and trained mechanical states in HD3. Time intervals between the AE signals detected at the opposite ends of HD3 coils were processed using a combination of narrow-band pass filtering; threshold crossing and correlation algorithms, and the spatial distributions of AE sources and the mechanical energy release were calculated. Both distributions appear to be consistent with the quench location distribution. Energy statistics of the AE spikes exhibits a power-law scaling typical for the self-organized critical state.

Antigen-dependent fluorescence response of anti-c-Myc Quenchbody studied by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Mori, Yoshiharu; Okumura, Hisashi; Watanabe, Takayoshi; Hohsaka, Takahiro

2018-04-01

We performed metadynamics molecular dynamics simulations to reveal mechanism of antigen-dependent fluorescence response observed for site-specifically fluorescent-labeled single-chain antibody against c-Myc peptide antigen. We found that VH and VL bind with each other only when the antigen exists and that the fluorophore labeled at the N-terminus of VH interacts with Trp103 most stably. These results support the mechanism proposed from previous experiments: In the absence of antigen, Trp residues are partially exposed at the interface of VH and quench the fluorophore. In the presence of antigen, the Trp residues are buried between VH and VL , and the quenching is eliminated.

Witnessing The Onset Of Environmental Quenching At Z 1-2

NASA Astrophysics Data System (ADS)

Fossati, Matteo

2017-06-01

During the last decade observations of galaxies across cosmic times coupled with cosmological simulations have provided an increasingly clear description of galaxy evolution. In particular we have a fairly detailed phenomenological picture of how galaxies transition from star forming to passive (or quenched) as a function of their internal properties (e.g. stellar mass) and the external environment (e.g. local density). By exploiting the highly complete coverage of grism and spectroscopic redshifts from the 3D-HST survey, we derive the local environment for a deep and complete sample of galaxies in the five 3D-HST deep fields at 0.5 < z < 2.5. A robust definition of environment also requires accurate calibrations obtained using the most up to date semi-analytic model derived from the Millennium simulation. By combining observational data and models we have devised a robust statistical framework within which we link observables to physical quantities (e.g. halo mass and central/satellite status). In this talk I will present our latest results on the environmental quenching of satellites up to z 2.5 in the range of haloes commonly included in our sample Mhalo < 10^14. We find evidences that the quenching timescales for satellites are almost independent on halo mass but have a significant stellar mass dependence. In contrast to local observations we found that for low mass galaxies at z>1 this timescale approaches the Hubble time. I will discuss the physical motivation of these results in terms of quenching mechanisms and gas content of the satellites at the epoch of infall.

How can we probe the atom mass currents induced by synthetic gauge fields?

NASA Astrophysics Data System (ADS)

Paramekanti, Arun; Killi, Matthew; Trotzky, Stefan

2013-05-01

Ultracold atomic fermions and bosons in an optical lattice can have quantum ground states which support equilibrium currents in the presence of synthetic magnetic fields or spin orbit coupling. As a tool to uncover these mass currents, we propose using an anisotropic quantum quench of the optical lattice which dynamically converts the current patterns into measurable density patterns. Using analytical calculations and numerical simulations, we show that this scheme can probe diverse equilibrium bulk current patterns in Bose superfluids and Fermi fluids induced by synthetic magnetic fields, as well as detect the chiral edge currents in topological states of atomic matter such as quantum Hall and quantum spin Hall insulators. This work is supported by NSERC of Canada and the Canadian Institute for Advanced Research.

Spectroscopy of collective excitations in interacting low-dimensional many-body systems using quench dynamics.

PubMed

Gritsev, Vladimir; Demler, Eugene; Lukin, Mikhail; Polkovnikov, Anatoli

2007-11-16

We study the problem of rapid change of the interaction parameter (quench) in a many-body low-dimensional system. It is shown that, measuring the correlation functions after the quench, the information about a spectrum of collective excitations in a system can be obtained. This observation is supported by analysis of several integrable models and we argue that it is valid for nonintegrable models as well. Our conclusions are supplemented by performing exact numerical simulations on finite systems. We propose that measuring the power spectrum in a dynamically split 1D Bose-Einsten condensate into two coupled condensates can be used as an experimental test of our predictions.

Effects of die quench forming on sheet thinning and 3-point bend testing of AA7075-T6

NASA Astrophysics Data System (ADS)

Kim, Samuel; Omer, Kaab; Rahmaan, Taamjeed; Butcher, Clifford; Worswick, Michael

2017-10-01

Lab-scaled AA7075 aluminum side impact beams were manufactured using the die quenching technique in which the sheet was solutionized and then quenched in-die during forming to a super saturated solid state. Sheet thinning measurements were taken at various locations throughout the length of the part and the effect of lubricant on surface scoring and material pick-up on the die was evaluated. The as-formed beams were subjected to a T6 aging treatment and then tested in three-point bending. Simulations were performed of the forming and mechanical testing experiments using the LS-DYNA finite element code. The thinning and mechanical response was predicted well.

A dichotomy in satellite quenching around L* galaxies

NASA Astrophysics Data System (ADS)

Phillips, John I.; Wheeler, Coral; Boylan-Kolchin, Michael; Bullock, James S.; Cooper, Michael C.; Tollerud, Erik J.

2014-01-01

We examine the star formation properties of bright (˜0.1 L*) satellites around isolated ˜L* hosts in the local Universe using spectroscopically confirmed systems in the Sloan Digital Sky Survey Data Release 7. Our selection method is carefully designed with the aid of N-body simulations to avoid groups and clusters. We find that satellites are significantly more likely to be quenched than a stellar mass-matched sample of isolated galaxies. Remarkably, this quenching occurs only for satellites of hosts that are themselves quenched: while star formation is unaffected in the satellites of star-forming hosts, satellites around quiescent hosts are more than twice as likely to be quenched than stellar-mass-matched field samples. One implication of this is that whatever shuts down star formation in isolated, passive L* galaxies also play at least an indirect role in quenching star formation in their bright satellites. The previously reported tendency for `galactic conformity' in colour/morphology may be a by-product of this host-specific quenching dichotomy. The Sérsic indices of quenched satellites are statistically identical to those of field galaxies with the same specific star formation rates, suggesting that environmental and secular quenching give rise to the same morphological structure. By studying the distribution of pairwise velocities between the hosts and satellites, we find dynamical evidence that passive host galaxies reside in dark matter haloes that are ˜45 per cent more massive than those of star-forming host galaxies of the same stellar mass. We emphasize that even around passive hosts, the mere fact that galaxies become satellites does not typically result in star formation quenching: we find that only ˜30 per cent of ˜0.1L* galaxies that fall in from the field are quenched around passive hosts, compared with ˜0 per cent around star-forming hosts.

Killing Star Formation in Satellite Galaxies

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-08-01

When a dwarf galaxy falls into the halo of a large galaxy like the Milky Way, how is star formation in the dwarf affected? A collaboration led by Andrew Wetzel (California Institute of Technology and Carnegie Observatories) recently set out to answer this question using observations of nearby galaxies and simulations of the infall process. Observed Quenching: Isolated dwarf galaxies tend to be gas-rich and very actively star-forming. In contrast, most dwarf galaxies within 300 kpc of us (the Milky Way's virial radius) contain little or no cold gas, and they're quiescent: there's not much star formation happening. And this isn't just true of the Milky Way; we observe the same difference in the satellite galaxies surrounding Andromeda galaxy. Once a dwarf galaxy has moved into the gravitational realm of a larger galaxy, the satellite's gas vanishes rapidly and its star formation is shut off — but how, and on what timescale? The known dwarf galaxies in the Local Group (out to 1.6 Mpc) are plotted by their distance from their host vs. their stellar mass. Blue stars indicate actively star-forming dwarfs and red circles indicate quiescent ones. Credit: Wetzel et al. 2015. Timescales for Quiescence: To answer these questions, the authors explored the process of galaxy infall using Exploring the Local Volume in Simulations (ELVIS), a suite of cosmological N-body simulations intended to explore the Local Group. They combined the infall times from the simulations with observational knowledge of the fraction of nearby galaxies that are currently quiescent, in order to determine what timescales are required for different processes to deplete the gas in the dwarf galaxies and quench star formation. Based on their results, two types of quenching culprits are at work: gas consumption (where a galaxy simply uses up its immediate gas supply and doesn't have access to more) and gas stripping (where external forces like ram pressure remove gas from the galaxy). These processes operate at different rates for different sizes of galaxies. The authors argue that for galaxies with stellar mass larger than 109 solar masses, the primary means of quenching is gas consumption. The timescale for this mechanism to quench the largest galaxies is roughly 5 Gyr. For galaxies with stellar mass smaller than 109 solar masses, gas stripping takes over, and star-formation is quenched within 1 Gyr for the smallest galaxies. Neither quenching mechanisms operates efficiently for galaxies with stellar mass right around 109 solar masses, though, so these galaxies can sustain star formation for much longer. This could explain why the Magellanic clouds (which both have stellar mass of roughly 109 solar masses) are still star-forming despite being within the Milky Way's halo! Citation: Andrew R. Wetzel et al. 2015, ApJ, 808, L27. doi:10.1088/2041-8205/808/1/L27

Caspase-Activated Cell-Penetrating Peptides Reveal Temporal Coupling Between Endosomal Release and Apoptosis in an RGC-5 Cell Model

PubMed Central

Johnson, James R.; Kocher, Brandon; Barnett, Edward M.; Marasa, Jayne; Piwnica-Worms, David

2012-01-01

Caspase-activatable cell-penetrating peptide (CPP) probes, designed for efficient cell uptake and specificity via cleavable intramolecular quenched-fluorophore strategies, show promise for identifying and imaging retinal ganglion cell apoptosis in vivo. However, initial cell uptake and trafficking events cannot be visualized because the probes are designed to be optically quenched in the intact state. To visualize subcellular activation events in real-time during apoptosis, a new series of matched quenched and non-quenched CPP probes were synthesized. In both native and staurosporine-differentiated RGC-5 cells, probe uptake was time- and concentration-dependent through clathrine-, caveolin- and pinocytosis-mediated endocytic mechanisms. During apoptosis, KcapTR488, a novel dual fluorophore CPP probe, revealed by multi-spectral imaging a temporal coupling of endosomal release and effector caspase activation in RGC-5 cells. The novel CPPs described herein provide new tools to study spatial and temporal regulation of endosomal permeability during apoptosis. PMID:22900707

Using a Specific RNA-Protein Interaction To Quench the Fluorescent RNA Spinach.

PubMed

Roszyk, Laura; Kollenda, Sebastian; Hennig, Sven

2017-12-15

RNAs are involved in interaction networks with other biomolecules and are crucial for proper cell function. Yet their biochemical analysis remains challenging. For Förster Resonance Energy Transfer (FRET), a common tool to study such interaction networks, two interacting molecules have to be fluorescently labeled. "Spinach" is a genetically encodable RNA aptamer that starts to fluoresce upon binding of an organic molecule. Therefore, it is a biological fluorophore tag for RNAs. However, spinach has never been used in a FRET assembly before. Here, we describe how spinach is quenched when close to acceptors. We used RNA-DNA hybridization to bring quenchers or red organic dyes in close proximity to spinach. Furthermore, we investigate RNA-protein interactions quantitatively on the example of Pseudomonas aeruginosa phage coat protein 7 (PP7) and its interacting pp7-RNA. We utilize spinach quenching as a fully genetically encodable system even under lysate conditions. Therefore, this work represents a direct method to analyze RNA-protein interactions by quenching the spinach aptamer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muzzin, Adam; Van der Burg, R. F. J.; McGee, Sean L.

We investigate the velocity versus position phase space of z ∼ 1 cluster galaxies using a set of 424 spectroscopic redshifts in nine clusters drawn from the GCLASS survey. Dividing the galaxy population into three categories, that is, quiescent, star-forming, and poststarburst, we find that these populations have distinct distributions in phase space. Most striking are the poststarburst galaxies, which are commonly found at small clustercentric radii with high clustercentric velocities, and appear to trace a coherent 'ring' in phase space. Using several zoom simulations of clusters, we show that the coherent distribution of the poststarbursts can be reasonably wellmore » reproduced using a simple quenching scenario. Specifically, the phase space is best reproduced if these galaxies are quenched with a rapid timescale (0.1 0.5 Gyr) or by quenching galaxies at larger radii (R ∼ R {sub 200}). We compare this quenching timescale to the timescale implied by the stellar populations of the poststarburst galaxies and find that the poststarburst spectra are well-fit by a rapid quenching (τ {sub Q} = 0.4{sub −0.4}{sup +0.3} Gyr) of a typical star-forming galaxy. The similarity between the quenching timescales derived from these independent indicators is a strong consistency check of the quenching model. Given that the model implies satellite quenching is rapid and occurs well within R {sub 200}, this would suggest that ram-pressure stripping of either the hot or cold gas component of galaxies are the most plausible candidates for the physical mechanism. The high cold gas consumption rates at z ∼ 1 make it difficult to determine whether hot or cold gas stripping is dominant; however, measurements of the redshift evolution of the satellite quenching timescale and location may be capable of distinguishing between the two.« less

Combining Graphical and Analytical Methods with Molecular Simulations To Analyze Time-Resolved FRET Measurements of Labeled Macromolecules Accurately

PubMed Central

2017-01-01

Förster resonance energy transfer (FRET) measurements from a donor, D, to an acceptor, A, fluorophore are frequently used in vitro and in live cells to reveal information on the structure and dynamics of DA labeled macromolecules. Accurate descriptions of FRET measurements by molecular models are complicated because the fluorophores are usually coupled to the macromolecule via flexible long linkers allowing for diffusional exchange between multiple states with different fluorescence properties caused by distinct environmental quenching, dye mobilities, and variable DA distances. It is often assumed for the analysis of fluorescence intensity decays that DA distances and D quenching are uncorrelated (homogeneous quenching by FRET) and that the exchange between distinct fluorophore states is slow (quasistatic). This allows us to introduce the FRET-induced donor decay, εD(t), a function solely depending on the species fraction distribution of the rate constants of energy transfer by FRET, for a convenient joint analysis of fluorescence decays of FRET and reference samples by integrated graphical and analytical procedures. Additionally, we developed a simulation toolkit to model dye diffusion, fluorescence quenching by the protein surface, and FRET. A benchmark study with simulated fluorescence decays of 500 protein structures demonstrates that the quasistatic homogeneous model works very well and recovers for single conformations the average DA distances with an accuracy of < 2%. For more complex cases, where proteins adopt multiple conformations with significantly different dye environments (heterogeneous case), we introduce a general analysis framework and evaluate its power in resolving heterogeneities in DA distances. The developed fast simulation methods, relying on Brownian dynamics of a coarse-grained dye in its sterically accessible volume, allow us to incorporate structural information in the decay analysis for heterogeneous cases by relating dye states with protein conformations to pave the way for fluorescence and FRET-based dynamic structural biology. Finally, we present theories and simulations to assess the accuracy and precision of steady-state and time-resolved FRET measurements in resolving DA distances on the single-molecule and ensemble level and provide a rigorous framework for estimating approximation, systematic, and statistical errors. PMID:28709377

Out-of-equilibrium protocol for Rényi entropies via the Jarzynski equality.

PubMed

Alba, Vincenzo

2017-06-01

In recent years entanglement measures, such as the von Neumann and the Rényi entropies, provided a unique opportunity to access elusive features of quantum many-body systems. However, extracting entanglement properties analytically, experimentally, or in numerical simulations can be a formidable task. Here, by combining the replica trick and the Jarzynski equality we devise an alternative effective out-of-equilibrium protocol for measuring the equilibrium Rényi entropies. The key idea is to perform a quench in the geometry of the replicas. The Rényi entropies are obtained as the exponential average of the work performed during the quench. We illustrate an application of the method in classical Monte Carlo simulations, although it could be useful in different contexts, such as in quantum Monte Carlo, or experimentally in cold-atom systems. The method is most effective in the quasistatic regime, i.e., for a slow quench. As a benchmark, we compute the Rényi entropies in the Ising universality class in 1+1 dimensions. We find perfect agreement with the well-known conformal field theory predictions.

Enabling the Public to Experience Science from Beginning to End (Invited)

NASA Astrophysics Data System (ADS)

Trouille, L.; Chen, Y.; Lintott, C.; Lynn, S.; Simmons, B.; Smith, A.; Tremonti, C.; Whyte, L.; Willett, K.; Zevin, M.; Science Team; Moderator Team, G.

2013-12-01

In this talk we present the results of an experiment in collaborative research and article writing within the citizen science context. During July-September 2013, astronomers and the Zooniverse team ran Galaxy Zoo Quench (quench.galaxyzoo.org), investigating the mechanism(s) that recently and abruptly shut off star formation in a sample of post-quenched galaxies. Through this project, the public had the opportunity to experience the entire process of science, including galaxy classification, reading background literature, data analysis, discussion, debate, drawing conclusions, and writing an article to submit to a professional journal. The context was galaxy evolution, however, the lessons learned are applicable across the disciplines. The discussion will focus on how to leverage online tools to authentically engage the public in the entire process of science.

Probing transverse momentum broadening via jet-related angular correlations in relativistic nuclear collisions

NASA Astrophysics Data System (ADS)

Chen, Lin; Qin, Guang-You; Wei, Shu-Yi; Xiao, Bo-Wen; Zhang, Han-Zhong

2017-11-01

Jet-related correlations have been regarded as important tools for studying jet-medium interaction and jet quenching in relativistic heavy-ion collisions at RHIC and the LHC. Here we present our recent work [L. Chen, G.-Y. Qin, S.-Y. Wei, B.-W. Xiao, H.-Z. Zhang, Probing Transverse Momentum Broadening via Dihadron and Hadron-jet Angular Correlations in Relativistic Heavy-ion Collisions, arxiv:arXiv:1607.01932] and show that the back-to-back angular correlations in dijet, dihadron and hadron-jet measurements can be utilized as a quantitative tool to probe the medium-induced transverse momentum broadening and to extract jet quenching parameter q̂. By comparing with the dihadron and hadron-jet angular correlation data at RHIC, we obtain the medium-induced transverse momentum broadening, averaged over different jet paths, 〈 p⊥2 〉 ∼ 13 GeV2 for a quark jet in most central Au-Au collisions at 200A GeV. Future experiments with statistically improved data on jet-related (angular) correlations will allow us to obtain more precise knowledge of jet quenching parameter and parton-medium interaction in high-energy nuclear collisions.

Probing the binding of Cu(2+) ions to a fragment of the Aβ(1-42) polypeptide using fluorescence spectroscopy, isothermal titration calorimetry and molecular dynamics simulations.

PubMed

Makowska, Joanna; Żamojć, Krzysztof; Wyrzykowski, Dariusz; Żmudzińska, Wioletta; Uber, Dorota; Wierzbicka, Małgorzata; Wiczk, Wiesław; Chmurzyński, Lech

2016-09-01

Steady-state and time-resolved fluorescence quenching measurements supported by isothermal titration calorimetry (ITC) and molecular dynamics simulations (MD), with the NMR-derived restraints, were used to investigate the interactions of Cu(2+) ions with a fragment of the Aβ(1-42) polypeptide, Aβ(5-16) with the following sequence: Ac-Arg-His-Asp-Ser-Gly-Tyr-Glu-Val-His-His-Gln-Lys-NH2, denoted as HZ1. The studies presented in this paper, when compared with our previous results (Makowska et al., Spectrochim. Acta A 153: 451-456), show that the affinity of the peptide to metal ions is conformation-dependent. All the measurements were carried out in 20mM 2-(N-morpholino)ethanesulfonic acid (MES) buffer solution, pH6.0. The Stern-Volmer equations, along with spectroscopic observations, were used to determine the quenching and binding parameters. The obtained results unequivocally suggest that Cu(2+) ions quench the fluorescence of HZ1 only through a static quenching mechanism, in contrast to the fragment from the N-terminal part of the FPB28 protein, with sequence Ac-Tyr-Lys-Thr-Ala-Asp-Gly-Lys-Thr-Tyr- NH2 (D9) and its derivative with a single point mutation: Ac-Tyr-Lys-Thr-Ala-Asn-Gly-Lys-Thr-Tyr- NH2 (D9_M), where dynamic quenching occurred. The thermodynamic parameters (ΔITCH, ΔITCS) for the interactions between Cu(2+) ions and the HZ1 peptide were determined from the calorimetric data. The conditional thermodynamic parameters suggest that, under the experimental conditions, the formation of the Cu(2+)-HZ1 complex is both an enthalpy and entropy driven process. Copyright © 2016 Elsevier B.V. All rights reserved.

Refolding dynamics of stretched biopolymers upon force quench

PubMed Central

Hyeon, Changbong; Morrison, Greg; Pincus, David L.; Thirumalai, D.

2009-01-01

Single-molecule force spectroscopy methods can be used to generate folding trajectories of biopolymers from arbitrary regions of the folding landscape. We illustrate the complexity of the folding kinetics and generic aspects of the collapse of RNA and proteins upon force quench by using simulations of an RNA hairpin and theory based on the de Gennes model for homopolymer collapse. The folding time, τF, depends asymmetrically on δfS = f S − f m and δf Q = f m − f Q where f S (f Q) is the stretch (quench) force and f m is the transition midforce of the RNA hairpin. In accord with experiments, the relaxation kinetics of the molecular extension, R(t), occurs in three stages: A rapid initial decrease in the extension is followed by a plateau and finally, an abrupt reduction in R(t) occurs as the native state is approached. The duration of the plateau increases as λ = τ Q/τ F decreases (where τ Q is the time in which the force is reduced from f S to f Q). Variations in the mechanisms of force-quench relaxation as λ is altered are reflected in the experimentally measurable time-dependent entropy, which is computed directly from the folding trajectories. An analytical solution of the de Gennes model under tension reproduces the multistage stage kinetics in R(t). The prediction that the initial stages of collapse should also be a generic feature of polymers is validated by simulation of the kinetics of toroid (globule) formation in semiflexible (flexible) homopolymers in poor solvents upon quenching the force from a fully stretched state. Our findings give a unified explanation for multiple disparate experimental observations of protein folding. PMID:19915145

Off-resonance energy absorption in a linear Paul trap due to mass selective resonant quenching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sivarajah, I.; Goodman, D. S.; Wells, J. E.

Linear Paul traps (LPT) are used in many experimental studies such as mass spectrometry, atom-ion collisions, and ion-molecule reactions. Mass selective resonant quenching (MSRQ) is implemented in LPT either to identify a charged particle's mass or to remove unwanted ions from a controlled experimental environment. In the latter case, MSRQ can introduce undesired heating to co-trapped ions of different mass, whose secular motion is off resonance with the quenching ac field, which we call off-resonance energy absorption (OREA). We present simulations and experimental evidence that show that the OREA increases exponentially with the number of ions loaded into the trapmore » and with the amplitude of the off-resonance external ac field.« less

Correlation of heat transfer coefficient in quenching process using ABAQUS

NASA Astrophysics Data System (ADS)

Davare, Sandeep Kedarnath; Balachandran, G.; Singh, R. K. P.

2018-04-01

During the heat treatment by quenching in a liquid medium the convective heat transfer coefficient plays a crucial role in the extraction of heat. The heat extraction ultimately influences the cooling rate and hence the hardness and mechanical properties. A Finite Element analysis of quenching a simple flat copper sample with different orientation of sample and with different quenchant temperatures were carried out to check and verify the results obtained from the experiments. The heat transfer coefficient (HTC) was calculated from temperature history in a simple flat copper disc sample experimentally. This HTC data was further used as input to simulation software and the cooling curves were back calculated. The results obtained from software and using experimentation shows nearly consistent values.

Lateral Distribution of NBD-PC Fluorescent Lipid Analogs in Membranes Probed by Molecular Dynamics-Assisted Analysis of Förster Resonance Energy Transfer (FRET) and Fluorescence Quenching

PubMed Central

Loura, Luís M. S.

2012-01-01

Förster resonance energy transfer (FRET) is a powerful tool used for many problems in membrane biophysics, including characterization of the lateral distribution of lipid components and other species of interest. However, quantitative analysis of FRET data with a topological model requires adequate choices for the values of several input parameters, some of which are difficult to obtain experimentally in an independent manner. For this purpose, atomistic molecular dynamics (MD) simulations can be potentially useful as they provide direct detailed information on transverse probe localization, relative probe orientation, and membrane surface area, all of which are required for analysis of FRET data. This is illustrated here for the FRET pairs involving 1,6-diphenylhexatriene (DPH) as donor and either 1-palmitoyl,2-(6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino] hexanoyl)- sn-glycero-3-phosphocholine (C6-NBD-PC) or 1-palmitoyl,2-(12-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]dodecanoyl)-sn-glycero-3-phosphocholine (C12-NBD-PC) as acceptors, in fluid vesicles of 1,2-dipalmitoyl-sn-3-glycerophosphocholine (DPPC, 50 °C). Incorporation of results from MD simulations improves the statistical quality of model fitting to the experimental FRET data. Furthermore, the decay of DPH in the presence of moderate amounts of C12-NBD-PC (>0.4 mol%) is consistent with non-random lateral distribution of the latter, at variance with C6-NBD-PC, for which aggregation is ruled out up to 2.5 mol% concentration. These conclusions are supported by analysis of NBD-PC fluorescence self-quenching. Implications regarding the relative utility of these probes in membrane studies are discussed. PMID:23203080

Lateral distribution of NBD-PC fluorescent lipid analogs in membranes probed by molecular dynamics-assisted analysis of Förster Resonance Energy Transfer (FRET) and fluorescence quenching.

PubMed

Loura, Luís M S

2012-11-08

Förster resonance energy transfer (FRET) is a powerful tool used for many problems in membrane biophysics, including characterization of the lateral distribution of lipid components and other species of interest. However, quantitative analysis of FRET data with a topological model requires adequate choices for the values of several input parameters, some of which are difficult to obtain experimentally in an independent manner. For this purpose, atomistic molecular dynamics (MD) simulations can be potentially useful as they provide direct detailed information on transverse probe localization, relative probe orientation, and membrane surface area, all of which are required for analysis of FRET data. This is illustrated here for the FRET pairs involving 1,6-diphenylhexatriene (DPH) as donor and either 1-palmitoyl,2-(6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino] hexanoyl)- sn-glycero-3-phosphocholine (C6-NBD-PC) or 1-palmitoyl,2-(12-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]dodecanoyl)-sn-glycero-3-phosphocholine (C12-NBD-PC) as acceptors, in fluid vesicles of 1,2-dipalmitoyl-sn-3-glycerophosphocholine (DPPC, 50 °C). Incorporation of results from MD simulations improves the statistical quality of model fitting to the experimental FRET data. Furthermore, the decay of DPH in the presence of moderate amounts of C12-NBD-PC (>0.4 mol%) is consistent with non-random lateral distribution of the latter, at variance with C6-NBD-PC, for which aggregation is ruled out up to 2.5 mol% concentration. These conclusions are supported by analysis of NBD-PC fluorescence self-quenching. Implications regarding the relative utility of these probes in membrane studies are discussed.

Counting defects in an instantaneous quench.

PubMed

Ibaceta, D; Calzetta, E

1999-09-01

We consider the formation of defects in a nonequilibrium second-order phase transition induced by an instantaneous quench to zero temperature in a type II superconductor. We perform a full nonlinear simulation where we follow the evolution in time of the local order parameter field. We determine how far into the phase transition theoretical estimates of the defect density based on the Gaussian approximation yield a reliable prediction for the actual density. We also characterize quantitatively some aspects of the out of equilibrium phase transition.

Spectral functions at small energies and the electrical conductivity in hot quenched lattice QCD.

PubMed

Aarts, Gert; Allton, Chris; Foley, Justin; Hands, Simon; Kim, Seyong

2007-07-13

In lattice QCD, the maximum entropy method can be used to reconstruct spectral functions from Euclidean correlators obtained in numerical simulations. We show that at finite temperature the most commonly used algorithm, employing Bryan's method, is inherently unstable at small energies and gives a modification that avoids this. We demonstrate this approach using the vector current-current correlator obtained in quenched QCD at finite temperature. Our first results indicate a small electrical conductivity above the deconfinement transition.

The Tensile Properties of Advanced Nickel-Base Disk Superalloys During Quenching Heat Treatments

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; Gayda, John; Kantzos, Pete T.; Biles, Tiffany; Konkel, William

2001-01-01

There is a need to increase the temperature capabilities of superalloy turbine disks. This would allow full utilization of higher temperature combustor and airfoil concepts under development. One approach to meet this goal is to modify the processing and chemistry of advanced alloys, while preserving the ability to use rapid cooling supersolvus heat treatments to achieve coarse grain, fine gamma prime microstructures. An important step in this effort is to understand the key high temperature tensile properties of advanced alloys as they exist during supersolvus heat treatments. This could help in projecting cracking tendencies of disks during quenches from supersolvus heat treatments. The objective of this study was to examine the tensile properties of two advanced disk superalloys during simulated quenching heat treatments. Specimens were cooled from the solution heat treatment temperatures at controlled rates, interrupted, and immediately tensile tested at various temperatures. The responses and failure modes were compared and related to the quench cracking tendencies of disk forgings.

Thermal stability analysis of a superconducting magnet considering heat flow between magnet surface and liquid helium

NASA Astrophysics Data System (ADS)

Jang, J. Y.; Hwang, Y. J.; Ahn, M. C.; Choi, Y. S.

2018-07-01

This paper represents a numerical calculation method that enables highly-accurate simulations on temperature analysis of superconducting magnets considering the heat flow between the magnet and liquid helium during a quench. A three-dimensional (3D) superconducting magnet space was divided into many cells and the finite-difference method (FDM) was adopted to calculate the superconducting magnet temperatures governed by the heat transfer and joule heating of the each cell during a quench. To enhance the accuracy of the temperature calculations during a quench, the heat flow between the superconducting magnet surface and liquid helium, which lowers the magnet temperatures, was considered in this work. The electrical equation coupled with the governing thermal equation was also applied to calculate the change of the decay of the magnet current related to the joule heating. The proposed FDM method for temperatures calculation of a superconducting magnet during a quench process achieved results that were in good agreement with those obtained from an experiment.

Quenching of satellite galaxies at the outskirts of galaxy clusters

NASA Astrophysics Data System (ADS)

Zinger, Elad; Dekel, Avishai; Kravtsov, Andrey V.; Nagai, Daisuke

2018-04-01

We find, using cosmological simulations of galaxy clusters, that the hot X-ray emitting intracluster medium (ICM) enclosed within the outer accretion shock extends out to Rshock ˜ (2-3)Rvir, where Rvir is the standard virial radius of the halo. Using a simple analytic model for satellite galaxies in the cluster, we evaluate the effect of ram-pressure stripping on the gas in the inner discs and in the haloes at different distances from the cluster centre. We find that significant removal of star-forming disc gas occurs only at r ≲ 0.5Rvir, while gas removal from the satellite halo is more effective and can occur when the satellite is found between Rvir and Rshock. Removal of halo gas sets the stage for quenching of the star formation by starvation over 2-3 Gyr, prior to the satellite entry to the inner cluster halo. This scenario explains the presence of quenched galaxies, preferentially discs, at the outskirts of galaxy clusters, and the delayed quenching of satellites compared to central galaxies.

Evidence for strong evolution in galaxy environmental quenching efficiency between z = 1.6 and z = 0.9

NASA Astrophysics Data System (ADS)

Nantais, Julie B.; Muzzin, Adam; van der Burg, Remco F. J.; Wilson, Gillian; Lidman, Chris; Foltz, Ryan; DeGroot, Andrew; Noble, Allison; Cooper, Michael C.; Demarco, Ricardo

2017-02-01

We analyse the evolution of environmental quenching efficiency, the fraction of quenched cluster galaxies which would be star forming if they were in the field, as a function of redshift in 14 spectroscopically confirmed galaxy clusters with 0.87 < z < 1.63 from the Spitzer Adaptation of the Red-Sequence Cluster Survey. The clusters are the richest in the survey at each redshift. Passive fractions rise from 42_{-13}^{+10} per cent at z ˜ 1.6 to 80_{-9}^{+12} per cent at z ˜ 1.3 and 88_{-3}^{+4} per cent at z < 1.1, outpacing the change in passive fraction in the field. Environmental quenching efficiency rises dramatically from 16_{-19}^{+15} per cent at z ˜ 1.6 to 62_{-15}^{+21} per cent at z ˜ 1.3 and 73_{-7}^{+8} per cent at z ≲ 1.1. This work is the first to show direct observational evidence for a rapid increase in the strength of environmental quenching in galaxy clusters at z ˜ 1.5, where simulations show cluster-mass haloes undergo non-linear collapse and virialization.

E+A Galaxy Properties and Post-Starburst Galaxy Evolution Data through SDSS-IV MaNGA and Illustris: A Co-Analysis

NASA Astrophysics Data System (ADS)

Ojanen, Winonah; Dudley, Raymond; Edwards, Kay; Gonzalez, Andrea; Johnson, Amalya; Kerrison, Nicole; Marinelli, Mariarosa; Melchert, Nancy; Liu, Charles; Sloan Collaboration, SDSS-IV MaNGA

2018-01-01

E+A galaxies (Elliptical + A-type stars) are post-starburst galaxies that have experienced a sudden quenching phase. Using previous research methods, 39 candidates out of 2,812 galaxies observed, or 1.4%, were selected from the SDSS-IV MaNGA survey. We then identified morphological characteristics of the 39 galaxies including stellar kinematics, Gini coefficient, gas density and distribution and stellar ages. To study the origin of how E+A galaxies evolved to their present state, galaxy simulation data from the Illustris simulation was utilized to identify similar quenched post-starburst candidates. Seven post-starburst candidates were identified through star formation rate histories of Illustris simulated galaxies. The evolution of these galaxies is studied from 0 to 13.8 billion years ago to identify what caused the starburst and quenching of the Illustris candidates. Similar morphological characteristics of Illustris post-starburst candidates are pulled from before, during, and post-starburst and compared to the same morphological characteristics of the E+A galaxies from SDSS-IV MaNGA. The characteristics and properties of the Illustris galaxies are used to identify the possible evolutionary histories of the observed E+A galaxies. This work was supported by grants AST-1460860 from the National Science Foundation and SDSS FAST/SSP-483 from the Alfred P. Sloan Foundation to the CUNY College of Staten Island.

The influence of alloy composition on residual stresses in heat treated aluminium alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, J.S., E-mail: jeremy.robinson@ul.ie; Redington, W.

The as quenched properties of eight different heat treatable aluminium alloys are related to residual stress magnitudes with the objective being to establish if there is a relationship between the residual stress and the as quenched alloy hardness and strength. Near surface residual stresses were assessed with X-ray diffraction using both the established sin{sup 2}ψ method and the more recent cos α technique. Through thickness residual stresses were also characterised using neutron diffraction. The alloys were chosen to encompass a wide range of strengths. The low to medium strength alloys were 6060 and 6082, medium to high strength 2618A, 2014A,more » 7075, 7010 and two variants of 7449, while the very high strength alloy was the powder metallurgy alloy N707. To assess the as quenched strength, dynamic hardness and tensile properties were determined from samples tested immediately after quenching to minimise the influence of precipitation hardening by natural aging. In addition, hot hardness measurements were made in situ on samples cooled to simulate quench paths. Within the experimental constraints of the investigation, the distribution of residual stress through the thickness was found to follow the same pattern for all the alloys investigated, varying from tensile in the interior to surface compression. The influence of alloy strength was manifested as a change in the observed residual stress magnitudes, and surface residual stresses were found to vary linearly with as quenched hardness and strength. - Highlights: • As quenched aluminium alloys contain high magnitude residual stresses. • Surface is compressive balance by a tensile core. • As quenched surface residual stress is linear function of alloy strength. • In situ hot hardness demonstrates rapid change in intrinsic hardness during rapid cooling.« less

Measured and simulated heavy-ion beam loss patterns at the CERN Large Hadron Collider

NASA Astrophysics Data System (ADS)

Hermes, P. D.; Bruce, R.; Jowett, J. M.; Redaelli, S.; Salvachua Ferrando, B.; Valentino, G.; Wollmann, D.

2016-05-01

The Large Hadron Collider (LHC) at CERN pushes forward to new regimes in terms of beam energy and intensity. In view of the combination of very energetic and intense beams together with sensitive machine components, in particular the superconducting magnets, the LHC is equipped with a collimation system to provide protection and intercept uncontrolled beam losses. Beam losses could cause a superconducting magnet to quench, or in the worst case, damage the hardware. The collimation system, which is optimized to provide a good protection with proton beams, has shown a cleaning efficiency with heavy-ion beams which is worse by up to two orders of magnitude. The reason for this reduced cleaning efficiency is the fragmentation of heavy-ion beams into isotopes with a different mass to charge ratios because of the interaction with the collimator material. In order to ensure sufficient collimation performance in future ion runs, a detailed theoretical understanding of ion collimation is needed. The simulation of heavy-ion collimation must include processes in which 82 + 208Pb ions fragment into dozens of new isotopes. The ions and their fragments must be tracked inside the magnetic lattice of the LHC to determine their loss positions. This paper gives an overview of physical processes important for the description of heavy-ion loss patterns. Loss maps simulated by means of the two tools ICOSIM [1,2] and the newly developed STIER (SixTrack with Ion-Equivalent Rigidities) are compared with experimental data measured during LHC operation. The comparison shows that the tool STIER is in better agreement.

Protection heater design validation for the LARP magnets using thermal imaging

DOE PAGES

Marchevsky, M.; Turqueti, M.; Cheng, D. W.; ...

2016-03-16

Protection heaters are essential elements of a quench protection scheme for high-field accelerator magnets. Various heater designs fabricated by LARP and CERN have been already tested in the LARP high-field quadrupole HQ and presently being built into the coils of the high-field quadrupole MQXF. In order to compare the heat flow characteristics and thermal diffusion timescales of different heater designs, we powered heaters of two different geometries in ambient conditions and imaged the resulting thermal distributions using a high-sensitivity thermal video camera. We observed a peculiar spatial periodicity in the temperature distribution maps potentially linked to the structure of themore » underlying cable. Two-dimensional numerical simulation of heat diffusion and spatial heat distribution have been conducted, and the results of simulation and experiment have been compared. Imaging revealed hot spots due to a current concentration around high curvature points of heater strip of varying cross sections and visualized thermal effects of various interlayer structural defects. Furthermore, thermal imaging can become a future quality control tool for the MQXF coil heaters.« less

The Mass-Size Relation of Quenched, Quiescent Galaxies in the WISP Survey

NASA Astrophysics Data System (ADS)

Pahl, Anthony; Scarlata, Claudia; Rutkowski, Michael J.; Zanella, Anita; Bagley, Micaela B.; Colbert, James W.; Baronchelli, Ivano; Henry, Alaina L.; Hathi, Nimish P.; Teplitz, Harry I.; Rafelski, Marc; Dai, Yu Sophia; Malkan, Matthew Arnold; Mehta, Vihang; Beck, Melanie

2016-01-01

The relation between the stellar mass and size, if measured for galaxies of similar types, can be a useful tool for studying galactic evolution. We study the mass-size relation of quenched, quiescent galaxies to determine the effect of star-formation history on the growth of these objects over time. The WFC3 Infrared Spectroscopic Parallels (WISP) survey is a large HST IR grism survey of over 385 fields of ~4 arcmin2 each, and it is ideal for studying the star-formation rate with its broad spectral coverage. Using a subset of these fields with deep IR data and measurements across both filters (28 fields), we perform a color selection and identify 83 quenched galaxies with a median z~1.6. With GALFIT, we measure their effective radius and sersic index on the 2-D surface brightness distribution in the F110W band. We perform fitting of grism spectra of the observed galaxies to derive redshift, stellar mass and age for all galaxies. We combine the size, stellar mass, and stellar age determinations to investigate whether the evolution of the mass-size relation over time is primarily driven by the entrance of newly quenched galaxies or by processes affecting the individual quenched galaxies.

The molecular dynamics simulation on the mechanical properties of Ni glass with external pressure

NASA Astrophysics Data System (ADS)

Zhang, Chuan-Hui; Wang, Ying; Sun, Dong-Bai

2017-08-01

In this paper, rapid quenching of Ni from crystal to metallic glass (MG) at different external pressures is simulated by molecular dynamics. The pair distribution functions (PDFs), mean-square displacement, glass transition temperature (Tg) and elastic property are calculated and compared with each other. The split of the second PDF peak means the liquid’s transition to glass state starts as previously reported for other MGs. And the Ri/R1 ratio rule is found to hold very well in Ni MG and reveals the SPO structural feature in the configurations. Moreover, with high external pressure, Tg values are more approximated by density-temperature and enthalpy-temperature curves. At last, the elastic modulus and mechanics modulus of quenching models produced a monotonous effect with increasing external pressure and temperature.

Lattice QCD static potentials of the meson-meson and tetraquark systems computed with both quenched and full QCD

NASA Astrophysics Data System (ADS)

Bicudo, P.; Cardoso, M.; Oliveira, O.; Silva, P. J.

2017-10-01

We revisit the static potential for the Q Q Q ¯Q ¯ system using SU(3) lattice simulations, studying both the color singlets' ground state and first excited state. We consider geometries where the two static quarks and the two antiquarks are at the corners of rectangles of different sizes. We analyze the transition between a tetraquark system and a two-meson system with a two by two correlator matrix. We compare the potentials computed with quenched QCD and with dynamical quarks. We also compare our simulations with the results of previous studies and analyze quantitatively fits of our results with Ansätze inspired in the string flip-flop model and in its possible color excitations.

Quenching an expanding chiral condensate

NASA Astrophysics Data System (ADS)

Bialas, A.; Czyz, W.; Gmyrek, M.

1995-04-01

We simulate quenching in the O(4) σ model of hadronic matter expanding along the z axis, with randomly generated initial conditions imposed at a given boost invariant time τ0= √t2-z2 . A comparison of our results with the simulations of Rajagopal and Wilczek for a nonexpanding case shows that the normalized power exhibits approximately the same frequency of oscillations in the laboratory time in both cases. However, the response of the expanding system depends on τ0: e.g., for τ0=1 fm it is about 2 orders of magnitude smaller than for the nonexpanding system. Also, the relaxation time becomes shorter with expansion present. When τ0-->∞ the two cases become identical. Kinematical windows for the production of a disoriented chiral condensate are also discussed.

Correlation effects in the quench-induced phase separation dynamics of a two species ultracold quantum gas

NASA Astrophysics Data System (ADS)

Mistakidis, S. I.; Katsimiga, G. C.; Kevrekidis, P. G.; Schmelcher, P.

2018-04-01

We explore the quench dynamics of a binary Bose–Einstein condensate crossing the miscibility–immiscibility threshold and vice versa, both within and in particular beyond the mean-field approximation. Increasing the interspecies repulsion leads to the filamentation of the density of each species, involving shorter wavenumbers and longer spatial scales in the many-body (MB) approach. These filaments appear to be strongly correlated and exhibit domain-wall structures. Following the reverse quench process multiple dark–antidark solitary waves are spontaneously generated and subsequently found to decay in the MB scenario. We simulate single-shot images to connect our findings to possible experimental realizations. Finally, the growth rate of the variance of a sample of single-shots probes the degree of entanglement inherent in the system.

The investigation of the interaction between NCP-EDA and bovine serum albumin by spectroscopic approaches

NASA Astrophysics Data System (ADS)

Yu, Xianyong; Lu, Shiyu; Yang, Ying; Li, Xiaofang; Yi, Pinggui

2011-12-01

The fluorescence and ultraviolet spectroscopies were explored to study the interaction between N-confused porphyrins-edaravone diad (NCP-EDA) and bovine serum albumin (BSA) under simulative physiological condition at different temperatures. The experimental results show that the fluorescence quenching mechanism between NCP-EDA and BSA is a combined quenching (dynamic and static quenching). The binding constants, binding sites and the corresponding thermodynamic parameters (Δ G, Δ H, and Δ S) of the interaction system were calculated at different temperatures. According to Förster non-radiation energy transfer theory, the binding distance between NCP-EDA and BSA was calculated to be 3.63 nm. In addition, the effect of NCP-EDA on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy.

Simulation of the Growth of Austenite from As-Quenched Martensite in Medium Mn Steels

NASA Astrophysics Data System (ADS)

Huyan, Fei; Yan, Jia-Yi; Höglund, Lars; Ågren, John; Borgenstam, Annika

2018-04-01

As part of an ongoing development of third-generation advanced high-strength steels with acceptable cost, austenite reversion treatment of medium Mn steels becomes attractive because it can give rise to a microstructure of fine mixture of ferrite and austenite, leading to both high strength and large elongation. The growth of austenite during intercritical annealing is crucial for the final properties, primarily because it determines the fraction, composition, and phase stability of austenite. In the present work, the growth of austenite from as-quenched lath martensite in medium Mn steels has been simulated using the DICTRA software package. Cementite is added into the simulations based on experimental observations. Two types of systems (cells) are used, representing, respectively, (1) austenite and cementite forming apart from each other, and (2) austenite forming on the cementite/martensite interface. An interfacial dissipation energy has also been added to take into account a finite interface mobility. The simulations using the first type of setup with an addition of interfacial dissipation energy are able to reproduce the observed austenite growth in medium Mn steels reasonably well.

Understanding homogeneous nucleation in solidification of aluminum by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Mahata, Avik; Asle Zaeem, Mohsen; Baskes, Michael I.

2018-02-01

Homogeneous nucleation from aluminum (Al) melt was investigated by million-atom molecular dynamics simulations utilizing the second nearest neighbor modified embedded atom method potentials. The natural spontaneous homogenous nucleation from the Al melt was produced without any influence of pressure, free surface effects and impurities. Initially isothermal crystal nucleation from undercooled melt was studied at different constant temperatures, and later superheated Al melt was quenched with different cooling rates. The crystal structure of nuclei, critical nucleus size, critical temperature for homogenous nucleation, induction time, and nucleation rate were determined. The quenching simulations clearly revealed three temperature regimes: sub-critical nucleation, super-critical nucleation, and solid-state grain growth regimes. The main crystalline phase was identified as face-centered cubic, but a hexagonal close-packed (hcp) and an amorphous solid phase were also detected. The hcp phase was created due to the formation of stacking faults during solidification of Al melt. By slowing down the cooling rate, the volume fraction of hcp and amorphous phases decreased. After the box was completely solid, grain growth was simulated and the grain growth exponent was determined for different annealing temperatures.

Forced-Unfolding and Force-Quench Refolding of RNA Hairpins

PubMed Central

Hyeon, Changbong; Thirumalai, D.

2006-01-01

Nanomanipulation of individual RNA molecules, using laser optical tweezers, has made it possible to infer the major features of their energy landscape. Time-dependent mechanical unfolding trajectories, measured at a constant stretching force (fS) of simple RNA structures (hairpins and three-helix junctions) sandwiched between RNA/DNA hybrid handles show that they unfold in a reversible all-or-none manner. To provide a molecular interpretation of the experiments we use a general coarse-grained off-lattice Gō-like model, in which each nucleotide is represented using three interaction sites. Using the coarse-grained model we have explored forced-unfolding of RNA hairpin as a function of fS and the loading rate (rf). The simulations and theoretical analysis have been done both with and without the handles that are explicitly modeled by semiflexible polymer chains. The mechanisms and timescales for denaturation by temperature jump and mechanical unfolding are vastly different. The directed perturbation of the native state by fS results in a sequential unfolding of the hairpin starting from their ends, whereas thermal denaturation occurs stochastically. From the dependence of the unfolding rates on rf and fS we show that the position of the unfolding transition state is not a constant but moves dramatically as either rf or fS is changed. The transition-state movements are interpreted by adopting the Hammond postulate for forced-unfolding. Forced-unfolding simulations of RNA, with handles attached to the two ends, show that the value of the unfolding force increases (especially at high pulling speeds) as the length of the handles increases. The pathways for refolding of RNA from stretched initial conformation, upon quenching fS to the quench force fQ, are highly heterogeneous. The refolding times, upon force-quench, are at least an order-of-magnitude greater than those obtained by temperature-quench. The long fQ-dependent refolding times starting from fully stretched states are analyzed using a model that accounts for the microscopic steps in the rate-limiting step, which involves the trans to gauche transitions of the dihedral angles in the GAAA tetraloop. The simulations with explicit molecular model for the handles show that the dynamics of force-quench refolding is strongly dependent on the interplay of their contour length and persistence length and the RNA persistence length. Using the generality of our results, we also make a number of precise experimentally testable predictions. PMID:16473903

Degradation of different elastomeric polymers in simulated geothermal environments at 300°C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugama, Toshifumi; Pyatina, Tatiana; Redline, Erica Marie

This study evaluates the degradation of six different elastomeric polymers used for O-rings: EPDM, FEPM, type I- and II-FKM, FFKM, and FSR, in five different simulated geothermal environments at 300 °C: 1) non-aerated steam/cooling cycles, 2) aerated steam/cooling cycles, 3) water-based drilling fluid, 4) CO 2-rich geo-brine fluid, and, 5) heat–cool water quenching cycles. The factors assessed included the extent of oxidation, changes in thermal behavior, micro-defects, permeation of ionic species from the test environments into the O-rings, silicate-related scale-deposition, and changes in the O-rings' elastic modulus. The reliability of the O-rings to maintain their integrity depended on the elastomericmore » polymer composition and the exposure environment. FSR disintegrated while EPDM was oxidized only to some degree in all the environments, FKM withstood heat-water quenching but underwent chemical degradation, FEPM survived in all the environments with the exception of heat-water quenching where it underwent severe oxidation-induced degradation, and FFKM displayed outstanding compatibility with all the tested environments. This study discusses the degradation mechanisms of the polymers under the aforementioned conditions.« less

Degradation of different elastomeric polymers in simulated geothermal environments at 300°C

DOE PAGES

Sugama, Toshifumi; Pyatina, Tatiana; Redline, Erica Marie; ...

2015-07-17

This study evaluates the degradation of six different elastomeric polymers used for O-rings: EPDM, FEPM, type I- and II-FKM, FFKM, and FSR, in five different simulated geothermal environments at 300 °C: 1) non-aerated steam/cooling cycles, 2) aerated steam/cooling cycles, 3) water-based drilling fluid, 4) CO 2-rich geo-brine fluid, and, 5) heat–cool water quenching cycles. The factors assessed included the extent of oxidation, changes in thermal behavior, micro-defects, permeation of ionic species from the test environments into the O-rings, silicate-related scale-deposition, and changes in the O-rings' elastic modulus. The reliability of the O-rings to maintain their integrity depended on the elastomericmore » polymer composition and the exposure environment. FSR disintegrated while EPDM was oxidized only to some degree in all the environments, FKM withstood heat-water quenching but underwent chemical degradation, FEPM survived in all the environments with the exception of heat-water quenching where it underwent severe oxidation-induced degradation, and FFKM displayed outstanding compatibility with all the tested environments. This study discusses the degradation mechanisms of the polymers under the aforementioned conditions.« less

Shattered Pellet Injection Simulations With NIMROD

NASA Astrophysics Data System (ADS)

Kim, Charlson; Parks, Paul; Lao, Lang; Lehnan, Michael; Loarte, Alberto; Izzo, Valerie; Nimrod Team

2017-10-01

Shattered Pellet Injection (SPI) will be the Disruption Mitigation System in ITER. SPI propels a cryo-pellet of high-Z and deuterium into a sharp bend of the flight tube, shattering the pellet into a plume of shards. These shards are injected into the plasma to quench it and mitigate forces and heat loads that may damage in-vessel components. We use NIMROD to perform 3-D nonlinear MHD simulations of SPI to study the thermal quench. This work builds upon prior Massive Gas Injection (MGI) studies by Izzo. A Particle-in-Cell (PIC) model is implemented to mimic the shards, providing a discrete moving source. Observations indicate that the quench proceeds in two phases. Initially, the outer plasma is shed via interchange-like instabilities while preserving the core temperature. This results in a steep gradient and triggers the second phase, an external kink-like event that collapses the core. We report on the radiation efficiency and toroidal peaking as well as fueling efficiency and other metrics that assess the efficacy of the SPI system. Work supported by GA ITER Contract ITER/CT/14/4300001108 and US DOE DE-FG02-95ER54309.

Experimental evaluation of tool wear throughout a continuous stroke blanking process of quenched 22MnB5 ultra-high-strength steel

NASA Astrophysics Data System (ADS)

Vogt, S.; Neumayer, F. F.; Serkyov, I.; Jesner, G.; Kelsch, R.; Geile, M.; Sommer, A.; Golle, R.; Volk, W.

2017-09-01

Steel is the most common material used in vehicles’ chassis, which makes its research an important topic for the automotive industry. Recently developed ultra-high-strength steels (UHSS) provide extreme tensile strength up to 1,500 MPa and combine great crashworthiness with good weight reduction potential. However, in order to reach the final shape of sheet metal parts additional cutting steps such as trimming and piercing are often required. The final trimming of quenched metal sheets presents a huge challenge to a conventional process, mainly because of the required extreme cutting force. The high cutting impact, due to the materials’ brittleness, causes excessive tool wear or even sudden tool failure. Therefore, a laser is commonly used for the cutting process, which is time and energy consuming. The purpose of this paper is to demonstrate the capability of a conventional blanking tool design in a continuous stroke piercing process using boron steel 22MnB5 sheets. Two different types of tool steel were tested for their suitability as active cutting elements: electro-slag remelted (ESR) cold work tool steel Bohler K340 ISODUR and powder-metallurgic (PM) high speed steel Bohler S390 MICROCLEAN. A FEM study provided information about an optimized punch design, which withstands buckling under high cutting forces. The wear behaviour of the process was assessed by the tool wear of the active cutting elements as well as the quality of cut surfaces.

Some results on excited hadrons in 2-flavor QCD

NASA Astrophysics Data System (ADS)

Engel, G.; Lang, C. B.; Limmer, M.; Mohler, D.; Schafer, A.

Results of hadron spectroscopy with two dynamical mass-degenerate chirally improved quarks are presented. Three ensembles with pion masses of 322(5), 470(4) and 525(7) MeV, lattices of size 16^3 \\times 32, and lattice spacings close to 0.15 fm are investigated. We discuss the possible appearance of scattering states, considering masses and eigenvectors. Partially quenched results in the scalar channel suggest the presence of a 2-particle state, however, in most channels we cannot identify them. Where available, we compare to results from quenched simulations using the same action.

Quantum Kibble-Zurek Mechanism in a Spin-1 Bose-Einstein Condensate

NASA Astrophysics Data System (ADS)

Anquez, M.; Robbins, B. A.; Bharath, H. M.; Boguslawski, M.; Hoang, T. M.; Chapman, M. S.

2016-04-01

The dynamics of a quantum phase transition are explored using slow quenches from the polar to the broken-axisymmetry phases in a small spin-1 ferromagnetic Bose-Einstein condensate. Measurements of the evolution of the spin populations reveal a power-law scaling of the temporal onset of excitations versus quench speed as predicted from quantum extensions of the Kibble-Zurek mechanism. The satisfactory agreement of the measured scaling exponent with the analytical theory and numerical simulations provides experimental confirmation of the quantum Kibble-Zurek model.

Quenching of graphene quantum dots fluorescence by alkaline phosphatase activity in the presence of hydroquinone diphosphate.

PubMed

Pereira da Silva Neves, Marta Maria; González-García, María Begoña; Pérez-Junquera, Alejandro; Hernández-Santos, David; Fanjul-Bolado, Pablo

2018-05-01

In this work, a turn-off photoluminescent sensing proof-of-concept based on blue luminescent graphene quantum dots (GQDs) as the fluorescent probe was developed. For that purpose, GQDs optical response was related with the catalytic enzymatic activity of alkaline phosphatase (ALP), in the presence of hydroquinone diphosphate (HQDP). The hydrolysis of HQDP by ALP generated hydroquinone (HQ). The oxidation of HQ, enzymatically produced, to p-benzoquinone (BQ) resulted in the quenching of GQDs fluorescence (FL). Therefore, the developed luminescent sensing mechanism allowed the FL quenching with ALP activity to be related and thus quantified the concentration of ALP down to 0.5 nM of enzyme. This innovative design principle appears as a promising tool for the development of enzymatic sensors based on ALP labeling with fluorescent detection or even for direct ALP luminescent quantification in an easy, fast and sensitive manner. Copyright © 2018 John Wiley & Sons, Ltd.

The analysis of critical cooling rate for high-rise building steel S460

NASA Astrophysics Data System (ADS)

Lu, Shiping; Chen, Xia; Li, Qun; Wang, Haibao; Gu, Linhao

2017-09-01

High-rise building steel S460 is an important structure steel.The product process of the steel is Quenching&Tempering. The critical cooling rate of steel is very important in heavy plate quenching process, and it is also the basis of the cooling process[1].The critical cooling rate of HSLA steel S460 is obtained from the Thermal simulation method,and the differences about the microstructure and properties of different cooling rate is also analyzed.In this article, the angle of the grain boundary and the average grain size are analyzed by EBSD under different cooling rate. The relationship between grain boundary angle and grain size with the cooling rate is obtained. According to the experiment,it provides the basis for the formulation of the quenching process of the industrial production.

A diffusion-limited reaction model for self-propagating Al/Pt multilayers with quench limits

NASA Astrophysics Data System (ADS)

Kittell, D. E.; Yarrington, C. D.; Hobbs, M. L.; Abere, M. J.; Adams, D. P.

2018-04-01

A diffusion-limited reaction model was calibrated for Al/Pt multilayers ignited on oxidized silicon, sapphire, and tungsten substrates, as well as for some Al/Pt multilayers ignited as free-standing foils. The model was implemented in a finite element analysis code and used to match experimental burn front velocity data collected from several years of testing at Sandia National Laboratories. Moreover, both the simulations and experiments reveal well-defined quench limits in the total Al + Pt layer (i.e., bilayer) thickness. At these limits, the heat generated from atomic diffusion is insufficient to support a self-propagating wave front on top of the substrates. Quench limits for reactive multilayers are seldom reported and are found to depend on the thermal properties of the individual layers. Here, the diffusion-limited reaction model is generalized to allow for temperature- and composition-dependent material properties, phase change, and anisotropic thermal conductivity. Utilizing this increase in model fidelity, excellent overall agreement is shown between the simulations and experimental results with a single calibrated parameter set. However, the burn front velocities of Al/Pt multilayers ignited on tungsten substrates are over-predicted. Possible sources of error are discussed and a higher activation energy (from 41.9 kJ/mol.at. to 47.5 kJ/mol.at.) is shown to bring the simulations into agreement with the velocity data observed on tungsten substrates. This higher activation energy suggests an inhibited diffusion mechanism present at lower heating rates.

CONNECTING STAR FORMATION QUENCHING WITH GALAXY STRUCTURE AND SUPERMASSIVE BLACK HOLES THROUGH GRAVITATIONAL HEATING OF COOLING FLOWS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Fulai, E-mail: fulai.guo@phys.ethz.ch

2014-12-20

Recent observations suggested that star formation quenching in galaxies is related to galaxy structure. Here we propose a new mechanism to explain the physical origin of this correlation. We assume that while quenching is maintained in quiescent galaxies by a feedback mechanism, cooling flows in the hot halo gas can still develop intermittently. We study cooling flows in a large suite of around 90 hydrodynamic simulations of an isolated galaxy group, and find that the flow development depends significantly on the gravitational potential well in the central galaxy. If the galaxy's gravity is not strong enough, cooling flows result inmore » a central cooling catastrophe, supplying cold gas and feeding star formation to galactic bulges. When the bulge grows prominent enough, compressional heating starts to offset radiative cooling and maintains cooling flows in a long-term hot mode without producing a cooling catastrophe. Our model thus describes a self-limited growth channel for galaxy bulges and naturally explains the connection between quenching and bulge prominence. In particular, we explicitly demonstrate that M{sub ∗}/R{sub eff}{sup 1.5} is a good structural predictor of quenching. We further find that the gravity from the central supermassive black hole also affects the bimodal fate of cooling flows, and we predict a more general quenching predictor to be M{sub bh}{sup 1.6}M{sub ∗}/R{sub eff}{sup 1.5}, which may be tested in future observational studies.« less

Wet disc contraction to galactic blue nuggets and quenching to red nuggets

NASA Astrophysics Data System (ADS)

Dekel, A.; Burkert, A.

2014-02-01

We study the origin of high-redshift, compact, quenched spheroids (red nuggets) through the dissipative shrinkage of gaseous discs into compact star-forming systems (blue nuggets). The discs, fed by cold streams, undergo violent disc instability that drives gas into the centre (along with mergers). The inflow is dissipative when its time-scale is shorter than the star formation time-scale. This implies a threshold of ˜0.28 in the cold-to-total mass ratio within the disc radius. For the typical gas fraction ˜0.5 at z ˜ 2, this threshold is traced back to a maximum spin parameter of ˜0.05, implying that ˜half the star-forming galaxies contract to blue nuggets, while the rest form extended stellar discs. Thus, the surface density of blue galaxies is expected to be bimodal about ˜109 M⊙ kpc-2, slightly increasing with mass. The blue nuggets are expected to be rare at low z when the gas fraction is low. The blue nuggets quench to red nuggets by complementary internal and external mechanisms. Internal quenching by a compact bulge, in a fast mode and especially at high z, may involve starbursts, stellar and active galactic nucleus feedback, or Q-quenching. Quenching due to hot-medium haloes above 1012 M⊙ provides maintenance and a slower mode at low redshift. These predictions are confirmed in simulations and are consistent with observations at z = 0-3.

How to quench a galaxy

NASA Astrophysics Data System (ADS)

Pontzen, Andrew; Tremmel, Michael; Roth, Nina; Peiris, Hiranya V.; Saintonge, Amélie; Volonteri, Marta; Quinn, Tom; Governato, Fabio

2017-02-01

We show how the interplay between active galactic nuclei (AGNs) and merger history determines whether a galaxy quenches star formation (SF) at high redshift. We first simulate, in a full cosmological context, a galaxy of total dynamical mass Mvir = 1012 M⊙ at z = 2. Then we systematically alter the accretion history of the galaxy by minimally changing the linear overdensity in the initial conditions. This `genetic modification' approach allows the generation of three sets of Λ CDM initial conditions leading to maximum merger ratios of 1:10, 1:5 and 2:3, respectively. The changes leave the final halo mass, large-scale structure and local environment unchanged, providing a controlled numerical experiment. Interaction between the AGN physics and mergers in the three cases leads, respectively, to a star-forming, temporarily quenched and permanently quenched galaxy. However, the differences do not primarily lie in the black hole accretion rates, but in the kinetic effects of the merger: the galaxy is resilient against AGN feedback unless its gaseous disc is first disrupted. Typical accretion rates are comparable in the three cases, falling below 0.1 M⊙ yr-1, equivalent to around 2 per cent of the Eddington rate or 10-3 times the pre-quenching star formation rate, in agreement with observations. This low level of black hole accretion can be sustained even when there is insufficient dense cold gas for SF. Conversely, supernova feedback is too distributed to generate outflows in high-mass systems, and cannot maintain quenching over periods longer than the halo gas cooling time.

Combining Statistical Samples of Resolved-ISM Simulated Galaxies with Realistic Mock Observations to Fully Interpret HST and JWST Surveys

NASA Astrophysics Data System (ADS)

Faucher-Giguere, Claude-Andre

2016-10-01

HST has invested thousands of orbits to complete multi-wavelength surveys of high-redshift galaxies including the Deep Fields, COSMOS, 3D-HST and CANDELS. Over the next few years, JWST will undertake complementary, spatially-resolved infrared observations. Cosmological simulations are the most powerful tool to make detailed predictions for the properties of galaxy populations and to interpret these surveys. We will leverage recent major advances in the predictive power of cosmological hydrodynamic simulations to produce the first statistical sample of hundreds of galaxies simulated with 10 pc resolution and with explicit interstellar medium and stellar feedback physics proved to simultaneously reproduce the galaxy stellar mass function, the chemical enrichment of galaxies, and the neutral hydrogen content of galaxy halos. We will process our new set of full-volume cosmological simulations, called FIREBOX, with a mock imaging and spectral synthesis pipeline to produce realistic mock HST and JWST observations, including spatially-resolved photometry and spectroscopy. By comparing FIREBOX with recent high-redshift HST surveys, we will study the stellar build up of galaxies, the evolution massive star-forming clumps, their contribution to bulge growth, the connection of bulges to star formation quenching, and the triggering mechanisms of AGN activity. Our mock data products will also enable us to plan future JWST observing programs. We will publicly release all our mock data products to enable HST and JWST science beyond our own analysis, including with the Frontier Fields.

How to model AGN feedback in cosmological simulations?

NASA Astrophysics Data System (ADS)

Sijacki, Debora

2015-08-01

Hydrodynamical cosmological simulations are one of the most powerful tools to study the formation and evolution of galaxies in the fully non-linear regime. Despite several recent successes in simulating Milky Way look-alikes, self-consistent, ab-initio models are still a long way off. In this talk I will review numerical and physical uncertainties plaguing current state-of-the-art cosmological simulations of galaxy formation. I will then discuss which feedback mechanisms are needed to reproduce realistic stellar masses and galaxy morphologies in the present day Universe and argue that the black hole feedback is necessary for the quenching of massive galaxies. I will then demonstrate how black hole - host galaxy scaling relations depend on galaxy morphology and colour, highlighting the implications for the co-evolutionary picture between galaxies and their central black holes. In the second part of the talk I will present a novel method that permits to resolve gas flows around black holes all the way from large cosmological scales to the Bondi radii of black holes themselves. I will demonstrate that with this new numerical technique it is possible to estimate much more accurately gas properties in the vicinity of black holes than has been feasible before in galaxy and cosmological simulations, allowing to track reliably gas angular momentum transport from Mpc to pc scales. Finally, I will also discuss if AGN-driven outflows are more likely to be energy- or momentum-driven and what implications this has for the redshift evolution of black hole - host galaxy scaling relations.

Pulse-shape discrimination and energy quenching of alpha particles in Cs2LiLaBr6:Ce3+

NASA Astrophysics Data System (ADS)

Mesick, K. E.; Coupland, D. D. S.; Stonehill, L. C.

2017-01-01

Cs2LiLaBr6:Ce3+(CLLB) is an elpasolite scintillator that offers excellent linearity and gamma-ray energy resolution and sensitivity to thermal neutrons with the ability to perform pulse-shape discrimination (PSD) to distinguish gammas and neutrons. Our investigation of CLLB has indicated the presence of intrinsic radioactive alpha background that we have determined to be from actinium contamination of the lanthanum component. We measured the pulse shapes for gamma, thermal neutron, and alpha events and determined that PSD can be performed to separate the alpha background with a moderate figure of merit of 0.98. We also measured the electron-equivalent-energy of the alpha particles in CLLB and simulated the intrinsic alpha background from 227Ac to determine the quenching factor of the alphas. A linear quenching relationship Lα =Eα × q +L0 was found at alpha particle energies above 5 MeV, with a quenching factor q = 0.71 MeVee / MeV and an offset L0 = - 1.19 MeVee .

Ensemble and Single-Molecule Studies on Fluorescence Quenching in Transition Metal Bipyridine-Complexes

PubMed Central

Brox, Dominik; Kiel, Alexander; Wörner, Svenja Johanna; Pernpointner, Markus; Comba, Peter; Martin, Bodo; Herten, Dirk-Peter

2013-01-01

Beyond their use in analytical chemistry fluorescent probes continuously gain importance because of recent applications of single-molecule fluorescence spectroscopy to monitor elementary reaction steps. In this context, we characterized quenching of a fluorescent probe by different metal ions with fluorescence spectroscopy in the bulk and at the single-molecule level. We apply a quantitative model to explain deviations from existing standard models for fluorescence quenching. The model is based on a reversible transition from a bright to a dim state upon binding of the metal ion. We use the model to estimate the stability constants of complexes with different metal ions and the change of the relative quantum yield of different reporter dye labels. We found ensemble data to agree widely with results from single-molecule experiments. Our data indicates a mechanism involving close molecular contact of dye and quenching moiety which we also found in molecular dynamics simulations. We close the manuscript with a discussion of possible mechanisms based on Förster distances and electrochemical potentials which renders photo-induced electron transfer to be more likely than Förster resonance energy transfer. PMID:23483966

Quench protection challenges in long nb3sn accelerator magnets

NASA Astrophysics Data System (ADS)

Salmi, Tiina-Mari; Ambrosio, G.; Caspi, S.; Chlachidze, Guram; Dhallé, Marc; Felice, Helene; Ferracin, Paolo; Marchevsky, M.; Sabbi, G. L.; ten Kate, H. H. J.

2012-06-01

The quench protection of the several meter long, large aperture high-field Nb3Sn quadrupoles that the LARP collaboration is developing for the LHC interaction region upgrade, requires efficient protection heaters to quickly generate large resistive segments across the windings. To support the protection design, experiments in the recently tested LARP R&D magnets are aimed to characterize the coil response to different protection schemes. In particular, the delay to quench and the final hotspot temperatures are evaluated after firing the heaters at different powering regimes and coverage. Also, the contribution of external energy extraction is investigated. Based on the performed studies and computer simulations, it seems that if the same protection efficiency per unit length that is measured in a 1 m long model magnet can be scaled to a 3.6 m long magnet, and the heater coverage can be improved, about 1 MJ/m of stored energy can be absorbed in the magnet after a quench. However, significant technology developments are needed to scale the protection heater efficiency to longer magnets and to increase the coverage.

The contribution of residential coal combustion to the air quality in Beijing-Tianjin-Hebei (BTH), China: A case study

NASA Astrophysics Data System (ADS)

Li, X.; Li, G.; Junji, C.

2017-12-01

In the present study, a persistent heavy haze episode from 13 to 20 January 2014 in Beijing-Tianjin-Hebei (BTH) is simulated using the WRF-CHEM model to evaluate the contribution of residential coal combustion to the air quality. The residential coal used in BTH is replaced by the water-quenched semi-coke with much lower emission factors (EFs) in simulations. The EFs of OC for water-quenched semi-coke (0.12 g kg-1) is 2.42 times lower than that for residential coal used in Beijing-Tianjin (0.29 g kg-1) and 9.17 times in Hebei (1.1 g kg-1). The WRF-CHEM model reasonably well reproduces the spatial distributions and temporal variations of PM2.5 mass concentrations in BTH against the observations over monitoring sites and the temporal variations of aerosol species compared to the AMS measurements in Beijing. On average, the PM2.5 concentration is reduced by around 20 µg m-3 due to the residential coal replacement. Organic aerosols constitute about 62.3% of the PM2.5 reduction in BTH, much higher than the contribution from sulfate (7.0%), nitrate (3.1%), and ammonium (3.1%). In addition, the usage of water-quenched semi-coke in BTH also significantly reduces polycyclic aromatic hydrocarbon (PAHs) concentrations by 50-450 ng m-3 on average. Therefore, the usage of water-quenched semi-coke in BTH could considerably reduce the emissions of air pollutants and decrease the PM2.5 level, beneficial to improvement of the air quality in BTH.

A methodology to select galaxies just after the quenching of star formation

NASA Astrophysics Data System (ADS)

Citro, Annalisa; Pozzetti, Lucia; Quai, Salvatore; Moresco, Michele; Vallini, Livia; Cimatti, Andrea

2017-08-01

We propose a new methodology aimed at finding star-forming galaxies in the phase which immediately follows the star-formation (SF) quenching, based on the use of high- to low-ionization emission line ratios. These ratios rapidly disappear after the SF halt, due to the softening of the UV ionizing radiation. We focus on [O III] λ5007/Hα and [Ne III] λ3869/[O II] λ3727, studying them with simulations obtained with the cloudy photoionization code. If a sharp quenching is assumed, we find that the two ratios are very sensitive tracers as they drop by a factor of ˜ 10 within ˜10 Myr from the interruption of the SF; instead, if a smoother and slower SF decline is assumed (I.e. an exponentially declining SF history with e-folding time τ = 200 Myr), they decrease by a factor of ˜2 within ˜80 Myr. We mitigate the ionization-metallicity degeneracy affecting our methodology using pairs of emission line ratios separately related to metallicity and ionization, adopting the [N II] λ6584/[O II] λ3727 ratio as metallicity diagnostic. Using a Sloan Digital Sky Survey galaxy sample, we identify 10 examples among the most extreme quenching candidates within the [O III] λ5007/Hα versus [N II] λ6584/[O II] λ3727 plane, characterized by low [O III] λ5007/Hα, faint [Ne III] λ3869, and by blue dust-corrected spectra and (u - r) colours, as expected if the SF quenching has occurred in the very recent past. Our results also suggest that the observed fractions of quenching candidates can be used to constrain the quenching mechanism at work and its time-scales.

Finite-volume and partial quenching effects in the magnetic polarizability of the neutron

NASA Astrophysics Data System (ADS)

Hall, J. M. M.; Leinweber, D. B.; Young, R. D.

2014-03-01

There has been much progress in the experimental measurement of the electric and magnetic polarizabilities of the nucleon. Similarly, lattice QCD simulations have recently produced dynamical QCD results for the magnetic polarizability of the neutron approaching the chiral regime. In order to compare the lattice simulations with experiment, calculation of partial quenching and finite-volume effects is required prior to an extrapolation in quark mass to the physical point. These dependencies are described using chiral effective field theory. Corrections to the partial quenching effects associated with the sea-quark-loop electric charges are estimated by modeling corrections to the pion cloud. These are compared to the uncorrected lattice results. In addition, the behavior of the finite-volume corrections as a function of pion mass is explored. Box sizes of approximately 7 fm are required to achieve a result within 5% of the infinite-volume result at the physical pion mass. A variety of extrapolations are shown at different box sizes, providing a benchmark to guide future lattice QCD calculations of the magnetic polarizabilities. A relatively precise value for the physical magnetic polarizability of the neutron is presented, βn=1.93(11)stat(11)sys×10-4 fm3, which is in agreement with current experimental results.

Lattice study of planar equivalence: The quark condensate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armoni, Adi; Lucini, Biagio; Patella, Agostino

2008-08-15

We study quenched SU(N) gauge theories with fermions in the two-index symmetric, antisymmetric and the adjoint representations. Our main motivation is to check whether at large number of colors those theories become nonperturbatively equivalent. We prove the equivalence assuming that the charge-conjugation symmetry is not broken in pure Yang-Mills theory. We then carry out a quenched lattice simulation of the quark condensate in the symmetric, antisymmetric and the adjoint representations for SU(2), SU(3), SU(4), SU(6), and SU(8). We show that the data support the equivalence and discuss the size of subleading corrections.

Cryogenic-coolant He-4-superconductor interaction

NASA Technical Reports Server (NTRS)

Caspi, S.; Lee, J. Y.; Kim, Y. I.; Allen, R. J.; Frederking, T. H. K.

1978-01-01

The thermodynamic and thermal interaction between a type 2 composite alloy and cryo-coolant He4 was studied with emphasis on post quench phenomena of formvar coated conductors. The latter were investigated using a heater simulation technique. Overall heat transfer coefficients were evaluated for the quench onset point. Heat flux densities were determined for phenomena of thermal switching between a peak and a recovery value. The study covered near saturated liquid, pressurized He4, both above and below the lambda transition, and above and below the thermodynamic critical pressure. In addition, friction coefficients for relative motion between formvar insulated conductors were determined.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohr, C.L.; Rausch, W.N.; Hesson, G.M.

The LOCA Simulation Program in the NRU reactor is the first set of experiments to provide data on the behavior of full-length, nuclear-heated PWR fuel bundles during the heatup, reflood, and quench phases of a loss-of-coolant accident (LOCA). This paper compares the temperature time histories of 4 experimental test cases with 4 computer codes: CE-THERM, FRAP-T5, GT3-FLECHT, and TRUMP-FLECHT. The preliminary comparisons between prediction and experiment show that the state-of-the art fuel codes have large uncertainties and are not necessarily conservative in predicting peak temperatures, turn around times, and bundle quench times.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smedskjaer, Morten M., E-mail: mos@bio.aau.dk; Bauchy, Mathieu; Mauro, John C.

The properties of glass are determined not only by temperature, pressure, and composition, but also by their complete thermal and pressure histories. Here, we show that glasses of identical composition produced through thermal annealing and through quenching from elevated pressure can result in samples with identical density and mean interatomic distances, yet different bond angle distributions, medium-range structures, and, thus, macroscopic properties. We demonstrate that hardness is higher when the density increase is obtained through thermal annealing rather than through pressure-quenching. Molecular dynamics simulations reveal that this arises because pressure-quenching has a larger effect on medium-range order, while annealing hasmore » a larger effect on short-range structures (sharper bond angle distribution), which ultimately determine hardness according to bond constraint theory. Our work could open a new avenue towards industrially useful glasses that are identical in terms of composition and density, but with differences in thermodynamic, mechanical, and rheological properties due to unique structural characteristics.« less

Dynamics of the quantum phase transition in the one-dimensional Bose-Hubbard model: Excitations and correlations induced by a quench

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gardas, Bartłomiej; Dziarmaga, Jacek; Zurek, Wojciech H.

The ground state of the one-dimensional Bose-Hubbard model at unit filling undergoes the Mott-superfluid quantum phase transition. It belongs to the Kosterlitz-Thouless universality class with an exponential divergence of the correlation length in place of the usual power law. Here, we present numerical simulations of a linear quench both from the Mott insulator to superfluid and back. The results satisfy the scaling hypothesis that follows from the Kibble-Zurek mechanism (KZM). In the superfluid-to-Mott quenches there is no significant excitation in the superfluid phase despite its gaplessness. And since all critical superfluid ground states are qualitatively similar, the excitation begins tomore » build up only after crossing the critical point when the ground state begins to change fundamentally. The last process falls into the KZM framework.« less

Bounding entanglement spreading after a local quench

NASA Astrophysics Data System (ADS)

Drumond, Raphael C.; Móller, Natália S.

2017-06-01

We consider the variation of von Neumann entropy of subsystem reduced states of general many-body lattice spin systems due to local quantum quenches. We obtain Lieb-Robinson-like bounds that are independent of the subsystem volume. The main assumptions are that the Hamiltonian satisfies a Lieb-Robinson bound and that the volume of spheres on the lattice grows at most exponentially with their radius. More specifically, the bound exponentially increases with time but exponentially decreases with the distance between the subsystem and the region where the quench takes place. The fact that the bound is independent of the subsystem volume leads to stronger constraints (than previously known) on the propagation of information throughout many-body systems. In particular, it shows that bipartite entanglement satisfies an effective "light cone," regardless of system size. Further implications to t density-matrix renormalization-group simulations of quantum spin chains and limitations to the propagation of information are discussed.

Dynamics of the quantum phase transition in the one-dimensional Bose-Hubbard model: Excitations and correlations induced by a quench

DOE PAGES

Gardas, Bartłomiej; Dziarmaga, Jacek; Zurek, Wojciech H.

2017-03-24

The ground state of the one-dimensional Bose-Hubbard model at unit filling undergoes the Mott-superfluid quantum phase transition. It belongs to the Kosterlitz-Thouless universality class with an exponential divergence of the correlation length in place of the usual power law. Here, we present numerical simulations of a linear quench both from the Mott insulator to superfluid and back. The results satisfy the scaling hypothesis that follows from the Kibble-Zurek mechanism (KZM). In the superfluid-to-Mott quenches there is no significant excitation in the superfluid phase despite its gaplessness. And since all critical superfluid ground states are qualitatively similar, the excitation begins tomore » build up only after crossing the critical point when the ground state begins to change fundamentally. The last process falls into the KZM framework.« less

Tribological performances of new steel grades for hot stamping tools

NASA Astrophysics Data System (ADS)

Medea, F.; Venturato, G.; Ghiotti, A.; Bruschi, S.

2017-09-01

In the last years, the use of High Strength Steels (HSS) as structural parts in car body-in-white manufacturing has rapidly increased thanks to their favourable strength-to-weight ratio and stiffness, which allow a reduction of the fuel consumption to accommodate the new restricted regulations for CO2 emissions control. The survey of the technical and scientific literature shows a large interest in the development of different coatings for the blanks from the traditional Al-Si up to new Zn-based coatings and on the analysis of hard PVD, CVD coatings and plasma nitriding applied on the tools. By contrast, fewer investigations have been focused on the development and test of new tools steels grades capable to improve the wear resistance and the thermal properties that are required for the in-die quenching during forming. On this base, the paper deals with the analysis and comparison the tribological performances in terms of wear, friction and heat transfer of new tool steel grades for high-temperature applications, characterized by a higher thermal conductivity than the commonly used tools. Testing equipment, procedures as well as measurements analyses to evaluate the friction coefficient, the wear and heat transfer phenomena are presented. Emphasis is given on the physical simulation techniques that were specifically developed to reproduce the thermal and mechanical cycles on the metal sheets and dies as in the industrial practice. The reference industrial process is the direct hot stamping of the 22MnB5 HSS coated with the common Al-Si coating for automotive applications.

Modeling of rapid shutdown in the DIII-D tokamak by core deposition of high-Z material

DOE PAGES

Izzo, Valerie A.; Parks, Paul B.

2017-06-22

MHD modeling of shell-pellet injection for disruption mitigation is carried out under the assumption of idealized delivery of the radiating payload to the core, neglecting the physics of shell ablation. The shell pellet method is designed to produce an inside-out thermal quench in which core thermal heat is radiated while outer flux surfaces remain intact, protecting the divertor from large conducted heat loads. In the simulation, good outer surfaces remain until the thermal quench is nearly complete, and a high radiated energy fraction is achieved. As a result, when the outermost surfaces are destroyed, runaway electron test orbits indicate thatmore » the rate of runaway electron loss is very fast compared with prior massive gas injection simulations, which is attributed to the very different current profile evolution that occurs with central cooling.« less

Posttest calculations of bundle quench test CORA-13 with ATHLET-CD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bestele, J.; Trambauer, K.; Schubert, J.D.

Gesellschaft fuer Anlagen- und Reaktorsicherheit is developing, in cooperation with the Institut fuer Kernenergetik und Energiesysteme, Stuttgart, the system code Analysis of Thermalhydraulics of Leaks and Transients with Core Degradation (ATHLET-CD). The code consists of detailed models of the thermal hydraulics of the reactor coolant system. This thermo-fluid dynamics module is coupled with modules describing the early phase of the core degradation, like cladding deformation, oxidation and melt relocation, and the release and transport of fission products. The assessment of the code is being done by the analysis of separate effect tests, integral tests, and plant events. The code willmore » be applied to the verification of severe accident management procedures. The out-of-pile test CORA-13 was conducted by Forschungszentrum Karlsruhe in their CORA test facility. The test consisted of two phases, a heatup phase and a quench phase. At the beginning of the quench phase, a sharp peak in the hydrogen generation rate was observed. Both phases of the test have been calculated with the system code ATHLET-CD. Special efforts have been made to simulate the heat losses and the flow distribution in the test facility and the thermal hydraulics during the quench phase. In addition to previous calculations, the material relocation and the quench phase have been modeled. The temperature increase during the heatup phase, the starting time of the temperature escalation, and the maximum temperatures have been calculated correctly. At the beginning of the quench phase, an increased hydrogen generation rate has been calculated as measured in the experiment.« less

Evidence of bovine serum albumin-viologen herbicide binding interaction and associated structural modifications

NASA Astrophysics Data System (ADS)

Roy, Swarup; Saxena, Shailendra K.; Mishra, Suryakant; Yogi, Priyanka; Sagdeo, P. R.; Kumar, Rajesh

2017-07-01

The binding ability of viologen herbicide with bovine serum albumin (BSA) has been investigated to understand viologen associated hazards by investigating ethyl viologen's (EV) binding using various spectroscopies and in-silico molecular docking approaches. Apparent association constant (1.3 × 104 L/mol), calculated using UV-Vis spectra indicating a moderate complex formation between BSA and EV. A static mode of fluorescence quenching has been observed as evident from inverse temperature dependence of Stern-Volmer quenching constant which also confirms an EV-BSA complex formation. Emission and time resolved fluorescence studies reveal that the emission quenching of BSA with EV is initiated by static quenching mechanism. A moderately strong binding affinity between EV and BSA has been observed (binding constant value of 7.58 × 104 L/Mol) using fluorescence quenching titration, obtained at 298 K. Quantitative measurements of thermodynamic parameters like enthalpy and entropy changes clearly indicates hydrophobic force responsible for EV-BSA complex formation. The binding distance between EV and BSA was found to be 4.48 nm are involved in non-radiative energy transfer process. Furthermore, from the circular dichroism spectra it was observed that addition of EV is also found to change the secondary structure of BSA which leads to decrease in α-helix. Above mentioned results are found to be in consonance with molecular docking simulations and supports the EV-BSA binding.

Surprises from quenches in long-range-interacting systems: temperature inversion and cooling

NASA Astrophysics Data System (ADS)

Gupta, Shamik; Casetti, Lapo

2016-10-01

What happens when one of the parameters governing the dynamics of a long-range interacting system of particles in thermal equilibrium is abruptly changed (quenched) to a different value? While a short-range system, under the same conditions, will relax in time to a new thermal equilibrium with a uniform temperature across the system, a long-range system shows a fast relaxation to a non-equilibrium quasistationary state (QSS). The lifetime of such an off-equilibrium state diverges with the system size, and the temperature is non-uniform across the system. Quite surprisingly, the density profile in the QSS obtained after the quench is anticorrelated with the temperature profile in space, thus exhibiting the phenomenon of temperature inversion: denser regions are colder than sparser ones. We illustrate with extensive molecular dynamics simulations the ubiquity of this scenario in a prototypical long-range interacting system subject to a variety of quenching protocols, and in a model that mimics an experimental setup of atoms interacting with light in an optical cavity. We further demonstrate how a procedure of iterative quenching combined with filtering out the high-energy particles in the system may be employed to cool the system. Temperature inversion is observed in nature in some astrophysical settings; our results imply that such a phenomenon should be observable, and could even be exploitable to advantage, also in controlled laboratory experiments.

Experimental and Numerical Studies on the Formability of Materials in Hot Stamping and Cold Die Quenching Processes

NASA Astrophysics Data System (ADS)

Li, N.; Mohamed, M. S.; Cai, J.; Lin, J.; Balint, D.; Dean, T. A.

2011-05-01

Formability of steel and aluminium alloys in hot stamping and cold die quenching processes is studied in this research. Viscoplastic-damage constitutive equations are developed and determined from experimental data for the prediction of viscoplastic flow and ductility of the materials. The determined unified constitutive equations are then implemented into the commercial Finite Element code Abaqus/Explicit via a user defined subroutine, VUMAT. An FE process simulation model and numerical procedures are established for the modeling of hot stamping processes for a spherical part with a central hole. Different failure modes (failure takes place either near the central hole or in the mid span of the part) are obtained. To validate the simulation results, a test programme is developed, a test die set has been designed and manufactured, and tests have been carried out for the materials with different forming rates. It has been found that very close agreements between experimental and numerical process simulation results are obtained for the ranges of temperatures and forming rates carried out.

Estimation of residual stresses in railroad commuter car wheels following manufacture

DOT National Transportation Integrated Search

2003-06-01

A finite element simulation is presented for the prediction of : residual stresses resulting from the heat treatment of railroad : commuter car wheels during manufacture. The quenching and : annealing segments of the wheel manufacturing process are s...

Estimation of residual stresses in railroad commuter car wheels following manufacture

DOT National Transportation Integrated Search

1998-11-01

A finite element simulation is presented for the prediction of residual stresses resulting from the heat treatment of railroad commuter car wheels during manufacture. The quenching and annealing segments of the wheel manufacturing process are simulat...

Quality assurance in proton beam therapy using a plastic scintillator and a commercially available digital camera.

PubMed

Almurayshid, Mansour; Helo, Yusuf; Kacperek, Andrzej; Griffiths, Jennifer; Hebden, Jem; Gibson, Adam

2017-09-01

In this article, we evaluate a plastic scintillation detector system for quality assurance in proton therapy using a BC-408 plastic scintillator, a commercial camera, and a computer. The basic characteristics of the system were assessed in a series of proton irradiations. The reproducibility and response to changes of dose, dose-rate, and proton energy were determined. Photographs of the scintillation light distributions were acquired, and compared with Geant4 Monte Carlo simulations and with depth-dose curves measured with an ionization chamber. A quenching effect was observed at the Bragg peak of the 60 MeV proton beam where less light was produced than expected. We developed an approach using Birks equation to correct for this quenching. We simulated the linear energy transfer (LET) as a function of depth in Geant4 and found Birks constant by comparing the calculated LET and measured scintillation light distribution. We then used the derived value of Birks constant to correct the measured scintillation light distribution for quenching using Geant4. The corrected light output from the scintillator increased linearly with dose. The system is stable and offers short-term reproducibility to within 0.80%. No dose rate dependency was observed in this work. This approach offers an effective way to correct for quenching, and could provide a method for rapid, convenient, routine quality assurance for clinical proton beams. Furthermore, the system has the advantage of providing 2D visualization of individual radiation fields, with potential application for quality assurance of complex, time-varying fields. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

The Phase Space and Stellar Populations of Cluster Galaxies at z ~ 1: Simultaneous Constraints on the Location and Timescale of Satellite Quenching

NASA Astrophysics Data System (ADS)

Muzzin, Adam; van der Burg, R. F. J.; McGee, Sean L.; Balogh, Michael; Franx, Marijn; Hoekstra, Henk; Hudson, Michael J.; Noble, Allison; Taranu, Dan S.; Webb, Tracy; Wilson, Gillian; Yee, H. K. C.

2014-11-01

We investigate the velocity versus position phase space of z ~ 1 cluster galaxies using a set of 424 spectroscopic redshifts in nine clusters drawn from the GCLASS survey. Dividing the galaxy population into three categories, that is, quiescent, star-forming, and poststarburst, we find that these populations have distinct distributions in phase space. Most striking are the poststarburst galaxies, which are commonly found at small clustercentric radii with high clustercentric velocities, and appear to trace a coherent "ring" in phase space. Using several zoom simulations of clusters, we show that the coherent distribution of the poststarbursts can be reasonably well reproduced using a simple quenching scenario. Specifically, the phase space is best reproduced if these galaxies are quenched with a rapid timescale (0.1 <τ Q < 0.5 Gyr) after they make their first passage of R ~ 0.5 R 200, a process that takes a total time of ~1 Gyr after first infall. The poststarburst phase space is not well reproduced using long quenching timescales (τ Q > 0.5 Gyr) or by quenching galaxies at larger radii (R ~ R 200). We compare this quenching timescale to the timescale implied by the stellar populations of the poststarburst galaxies and find that the poststarburst spectra are well-fit by a rapid quenching (τ Q = 0.4+0.3-0.4 Gyr) of a typical star-forming galaxy. The similarity between the quenching timescales derived from these independent indicators is a strong consistency check of the quenching model. Given that the model implies satellite quenching is rapid and occurs well within R 200, this would suggest that ram-pressure stripping of either the hot or cold gas component of galaxies are the most plausible candidates for the physical mechanism. The high cold gas consumption rates at z ~ 1 make it difficult to determine whether hot or cold gas stripping is dominant; however, measurements of the redshift evolution of the satellite quenching timescale and location may be capable of distinguishing between the two. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

Evaluating fluorescence spectroscopy as a tool to characterize cyanobacteria intracellular organic matter upon simulated release and oxidation in natural water.

PubMed

Korak, Julie A; Wert, Eric C; Rosario-Ortiz, Fernando L

2015-01-01

Intracellular organic matter (IOM) from cyanobacteria may be released into natural waters following cell death in aquatic ecosystems and during oxidation processes in drinking water treatment plants. Fluorescence spectroscopy was evaluated to identify the presence of IOM from three cyanobacteria species during simulated release into natural water and following oxidation processes (i.e. ozone, free chlorine, chloramine, chlorine dioxide). Peak picking and the fluorescence index (FI) were explored to determine which IOM components (e.g., pigments) provide unique and persistent fluorescence signatures with minimal interferences from the background dissolved organic matter (DOM) found in Colorado River water (CRW). When IOM was added to ultrapure water, the fluorescence signature of the three cyanobacteria species showed similarities to each other. Each IOM exhibited a strong protein-like fluorescence and fluorescence at Ex 370 nm and Em 460 nm (FDOM), where commercial fluorescence sensors monitor. All species also had strong phycobiliprotein fluorescence (i.e. phycocyanin or phycoerythrin) in the higher excitation range (500-650 nm). All three IOM isolates had FI values greater than 2. When IOM was added to CRW, phycobiliprotein fluorescence was quenched through interactions between IOM and CRW-DOM. Mixing IOM and CRW demonstrated that protein-like and FDOM intensity responses were not a simple superposition of the starting material intensities, indicating that interactions between IOM and CRW-DOM fluorescing moieties were important. Fluorescence intensity in all regions decreased with exposure to ozone, free chlorine, and chlorine dioxide, but the FI still indicated compositional differences compared to CRW-DOM. The phycobiliproteins in IOM are not promising as a surrogate for IOM release, because their fluorescence intensity is quenched by interactions with DOM and decreased during oxidation processes. Increases in both FDOM intensity and FI are viable qualitative indicators of IOM release in natural waters and following oxidation and may provide a more robust real-time indication of the presence of IOM than conventional dissolved organic carbon or UV absorbance measurements.

Measurement of Low-Energy Nuclear-Recoil Quenching Factors in CsI[Na] and Statistical Analysis of the First Observation of Coherent, Elastic Neutrino-Nucleus Scattering

NASA Astrophysics Data System (ADS)

Rich, Grayson Currie

The COHERENT Collaboration has produced the first-ever observation, with a significance of 6.7sigma, of a process consistent with coherent, elastic neutrino-nucleus scattering (CEnuNS) as first predicted and described by D.Z. Freedman in 1974. Physics of the CEnuNS process are presented along with its relationship to future measurements in the arenas of nuclear physics, fundamental particle physics, and astroparticle physics, where the newly-observed interaction presents a viable tool for investigations into numerous outstanding questions about the nature of the universe. To enable the CEnuNS observation with a 14.6-kg CsI[Na] detector, new measurements of the response of CsI[Na] to low-energy nuclear recoils, which is the only mechanism by which CEnuNS is detectable, were carried out at Triangle Universities Nuclear Laboratory; these measurements are detailed and an effective nuclear-recoil quenching factor of 8.78 +/- 1.66% is established for CsI[Na] in the recoil-energy range of 5-30 keV, based on new and literature data. Following separate analyses of the CEnuNS-search data by groups at the University of Chicago and the Moscow Engineering and Physics Institute, information from simulations, calculations, and ancillary measurements were used to inform statistical analyses of the collected data. Based on input from the Chicago analysis, the number of CEnuNS events expected from the Standard Model is 173 +/- 48; interpretation as a simple counting experiment finds 136 +/- 31 CEnuNS counts in the data, while a two-dimensional, profile likelihood fit yields 134 +/- 22 CEnuNS counts. Details of the simulations, calculations, and supporting measurements are discussed, in addition to the statistical procedures. Finally, potential improvements to the CsI[Na]-based CEnuNS measurement are presented along with future possibilities for COHERENT Collaboration, including new CEnuNS detectors and measurement of the neutrino-induced neutron spallation process.

Multiphysics Code Demonstrated for Propulsion Applications

NASA Technical Reports Server (NTRS)

Lawrence, Charles; Melis, Matthew E.

1998-01-01

The utility of multidisciplinary analysis tools for aeropropulsion applications is being investigated at the NASA Lewis Research Center. The goal of this project is to apply Spectrum, a multiphysics code developed by Centric Engineering Systems, Inc., to simulate multidisciplinary effects in turbomachinery components. Many engineering problems today involve detailed computer analyses to predict the thermal, aerodynamic, and structural response of a mechanical system as it undergoes service loading. Analysis of aerospace structures generally requires attention in all three disciplinary areas to adequately predict component service behavior, and in many cases, the results from one discipline substantially affect the outcome of the other two. There are numerous computer codes currently available in the engineering community to perform such analyses in each of these disciplines. Many of these codes are developed and used in-house by a given organization, and many are commercially available. However, few, if any, of these codes are designed specifically for multidisciplinary analyses. The Spectrum code has been developed for performing fully coupled fluid, thermal, and structural analyses on a mechanical system with a single simulation that accounts for all simultaneous interactions, thus eliminating the requirement for running a large number of sequential, separate, disciplinary analyses. The Spectrum code has a true multiphysics analysis capability, which improves analysis efficiency as well as accuracy. Centric Engineering, Inc., working with a team of Lewis and AlliedSignal Engines engineers, has been evaluating Spectrum for a variety of propulsion applications including disk quenching, drum cavity flow, aeromechanical simulations, and a centrifugal compressor flow simulation.

An investigation into the effects of conventional heat treatments on mechanical characteristics of new hot working tool steel

NASA Astrophysics Data System (ADS)

Fares, M. L.; Athmani, M.; Khelfaoui, Y.; Khettache, A.

2012-02-01

The effects of conventional heat treatments, i.e. quenching and tempering, on the mechanical characteristics of non standard hot work tool steel, close to either AISI-H11/H13 are investigated. The major elemental composition differences are in carbon, silicon and vanadium. The objective of the carried heat treatments is to obtain an efficient tool performance in terms of hardness, wear resistance and mechanical strength. Experimental results allow an explanation of the surface properties depending mainly on both chemical composition and optimised preheating parameters. After austenitizing at 1050 °C for 15 min, the as-quenched steel in oil bath exhibited the fully martensitic structure (without bainite) connected to a small fraction of retained austenite and complex carbides mainly of M23C6 type. Twice tempering at 500 °C and 600 °C resulted in initiating the precipitation processes and the secondary hardness effect. As a result, carbide content amounted to 3% while the retained austenite content decreased to 0%. Accordingly, the required mechanical properties in terms of hardness and wear are fulfilled and are adequately favourable in handling both shocks and pressures for the expected tool life. Induced microstructures are revealed using optical and scanning electron microscopes. Phase compositions are assessed by means of X-ray diffraction technique while mechanical characteristics are investigated based on hardness and abrasive wear standard tests.

Fluorimetric study on the interaction between Norfloxacin and Proflavine hemisulphate.

PubMed

More, Vishalkumar R; Anbhule, Prashant V; Lee, Sang H; Patil, Shivajirao R; Kolekar, Govind B

2011-07-01

The interaction between Norfloxacin (NF) and Proflavine hemisulphate (PF) was investigated by spectroscopic tools like UV-VIS absorption and Fluorescence spectroscopy. It was proved that fluorescence quenching of NF by PF is due to the formation of NF-PF complex which was supported by UV-VIS absorption study. The study of thermodynamic parameters suggested that the key interacting forces are hydrogen bond and van der Waal's interactions and the binding interaction was spontaneous. The distance r between NF and PF was obtained according to the Förster's theory of non-radiative energy transfer. The fluorescence quenching mechanism was applied to estimate PF directly from pharmaceutical samples. © Springer Science+Business Media, LLC 2011

Online quench-flow electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry for elucidating kinetic and chemical enzymatic reaction mechanisms.

PubMed

Clarke, David J; Stokes, Adam A; Langridge-Smith, Pat; Mackay, C Logan

2010-03-01

We have developed an automated quench-flow microreactor which interfaces directly to an electrospray ionization (ESI) mass spectrometer. We have used this device in conjunction with ESI Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) to demonstrate the potential of this approach for studying the mechanistic details of enzyme reactions. For the model system chosen to test this device, namely, the pre-steady-state hydrolysis of p-nitrophenyl acetate by the enzyme chymotrypsin, the kinetic parameters obtained are in good agreement with those in the literature. To our knowledge, this is the first reported use of online quench-flow coupled with FTICR MS. Furthermore, we have exploited the power of FTICR MS to interrogate the quenched covalently bound enzyme intermediate using top-down fragmentation. The accurate mass capabilities of FTICR MS permitted the nature of the intermediate to be assigned with high confidence. Electron capture dissociation (ECD) fragmentation allowed us to locate the intermediate to a five amino acid section of the protein--which includes the known catalytic residue, Ser(195). This experimental approach, which uniquely can provide both kinetic and chemical details of enzyme mechanisms, is a potentially powerful tool for studies of enzyme catalysis.

Computational studies of thermal and quantum phase transitions approached through non-equilibrium quenching

NASA Astrophysics Data System (ADS)

Liu, Cheng-Wei

Phase transitions and their associated critical phenomena are of fundamental importance and play a crucial role in the development of statistical physics for both classical and quantum systems. Phase transitions embody diverse aspects of physics and also have numerous applications outside physics, e.g., in chemistry, biology, and combinatorial optimization problems in computer science. Many problems can be reduced to a system consisting of a large number of interacting agents, which under some circumstances (e.g., changes of external parameters) exhibit collective behavior; this type of scenario also underlies phase transitions. The theoretical understanding of equilibrium phase transitions was put on a solid footing with the establishment of the renormalization group. In contrast, non-equilibrium phase transition are relatively less understood and currently a very active research topic. One important milestone here is the Kibble-Zurek (KZ) mechanism, which provides a useful framework for describing a system with a transition point approached through a non-equilibrium quench process. I developed two efficient Monte Carlo techniques for studying phase transitions, one is for classical phase transition and the other is for quantum phase transitions, both are under the framework of KZ scaling. For classical phase transition, I develop a non-equilibrium quench (NEQ) simulation that can completely avoid the critical slowing down problem. For quantum phase transitions, I develop a new algorithm, named quasi-adiabatic quantum Monte Carlo (QAQMC) algorithm for studying quantum quenches. I demonstrate the utility of QAQMC quantum Ising model and obtain high-precision results at the transition point, in particular showing generalized dynamic scaling in the quantum system. To further extend the methods, I study more complex systems such as spin-glasses and random graphs. The techniques allow us to investigate the problems efficiently. From the classical perspective, using the NEQ approach I verify the universality class of the 3D Ising spin-glasses. I also investigate the random 3-regular graphs in terms of both classical and quantum phase transitions. I demonstrate that under this simulation scheme, one can extract information associated with the classical and quantum spin-glass transitions without any knowledge prior to the simulation.

Computer Simulation To Assess The Feasibility Of Coring Magma

NASA Astrophysics Data System (ADS)

Su, J.; Eichelberger, J. C.

2017-12-01

Lava lakes on Kilauea Volcano, Hawaii have been successfully cored many times, often with nearly complete recovery and at temperatures exceeding 1100oC. Water exiting nozzles on the diamond core bit face quenches melt to glass just ahead of the advancing bit. The bit readily cuts a clean annulus and the core, fully quenched lava, passes smoothly into the core barrel. The core remains intact after recovery, even when there are comparable amounts of glass and crystals with different coefficients of thermal expansion. The unique resulting data reveal the rate and sequence of crystal growth in cooling basaltic lava and the continuous liquid line of descent as a function of temperature from basalt to rhyolite. Now that magma bodies, rather than lava pooled at the surface, have been penetrated by geothermal drilling, the question arises as to whether similar coring could be conducted at depth, providing fundamentally new insights into behavior of magma. This situation is considerably more complex because the coring would be conducted at depths exceeding 2 km and drilling fluid pressures of 20 MPa or more. Criteria that must be satisfied include: 1) melt is quenched ahead of the bit and the core itself must be quenched before it enters the barrel; 2) circulating drilling fluid must keep the temperature of the coring assembling cooled to within operational limits; 3) the drilling fluid column must nowhere exceed the local boiling point. A fluid flow simulation was conducted to estimate the process parameters necessary to maintain workable temperatures during the coring operation. SolidWorks Flow Simulation was used to estimate the effect of process parameters on the temperature distribution of the magma immediately surrounding the borehole and of drilling fluid within the bottom-hole assembly (BHA). A solid model of the BHA was created in SolidWorks to capture the flow behavior around the BHA components. Process parameters used in the model include the fluid properties and temperature of magma, coolant flow rate, rotation speed, and rate of penetration (ROP). The modeling results indicate that there are combinations of process parameters that will provide sufficient cooling to enable the desired coring process in magma.

Flexible Charged Macromolecules on Mixed Fluid Lipid Membranes: Theory and Monte Carlo Simulations

PubMed Central

Tzlil, Shelly; Ben-Shaul, Avinoam

2005-01-01

Fluid membranes containing charged lipids enhance binding of oppositely charged proteins by mobilizing these lipids into the interaction zone, overcoming the concomitant entropic losses due to lipid segregation and lower conformational freedom upon macromolecule adsorption. We study this energetic-entropic interplay using Monte Carlo simulations and theory. Our model system consists of a flexible cationic polyelectrolyte, interacting, via Debye-Hückel and short-ranged repulsive potentials, with membranes containing neutral lipids, 1% tetravalent, and 10% (or 1%) monovalent anionic lipids. Adsorption onto a fluid membrane is invariably stronger than to an equally charged frozen or uniform membrane. Although monovalent lipids may suffice for binding rigid macromolecules, polyvalent counter-lipids (e.g., phosphatidylinositol 4,5 bisphosphate), whose entropy loss upon localization is negligible, are crucial for binding flexible macromolecules, which lose conformational entropy upon adsorption. Extending Rosenbluth's Monte Carlo scheme we directly simulate polymer adsorption on fluid membranes. Yet, we argue that similar information could be derived from a biased superposition of quenched membrane simulations. Using a simple cell model we account for surface concentration effects, and show that the average adsorption probabilities on annealed and quenched membranes coincide at vanishing surface concentrations. We discuss the relevance of our model to the electrostatic-switch mechanism of, e.g., the myristoylated alanine-rich C kinase substrate protein. PMID:16126828

Simulated stellar kinematics studies of high-redshift galaxies with the HARMONI Integral Field Spectrograph

NASA Astrophysics Data System (ADS)

Kendrew, S.; Zieleniewski, S.; Houghton, R. C. W.; Thatte, N.; Devriendt, J.; Tecza, M.; Clarke, F.; O'Brien, K.; Häußler, B.

2016-05-01

We present a study into the capabilities of integrated and spatially resolved integral field spectroscopy of galaxies at z = 2-4 with the future HARMONI spectrograph for the European Extremely Large Telescope (E-ELT) using the simulation pipeline, HSIM. We focus particularly on the instrument's capabilities in stellar absorption line integral field spectroscopy, which will allow us to study the stellar kinematics and stellar population characteristics. Such measurements for star-forming and passive galaxies around the peak star formation era will provide a critical insight into the star formation, quenching and mass assembly history of high-z, and thus present-day galaxies. First, we perform a signal-to-noise study for passive galaxies at a range of stellar masses for z = 2-4, assuming different light profiles; for this population, we estimate that integrated stellar absorption line spectroscopy with HARMONI will be limited to galaxies with M* ≳ 1010.7 M⊙. Secondly, we use HSIM to perform a mock observation of a typical star-forming 1010 M⊙ galaxy at z = 3 generated from the high-resolution cosmological simulation NUTFB. We demonstrate that the input stellar kinematics of the simulated galaxy can be accurately recovered from the integrated spectrum in a 15-h observation, using common analysis tools. Whilst spatially resolved spectroscopy is likely to remain out of reach for this particular galaxy, we estimate HARMONI's performance limits in this regime from our findings. This study demonstrates how instrument simulators such as HSIM can be used to quantify instrument performance and study observational biases on kinematics retrieval; and shows the potential of making observational predictions from cosmological simulation output data.

On-chip integrated functional near infra-red spectroscopy (fNIRS) photoreceiver for portable brain imaging

NASA Astrophysics Data System (ADS)

Kamrani, Ehsan

Optical brain imaging using functional near infra-red spectroscopy (fNIRS) offers a direct and noninvasive tool for monitoring of blood oxygenation. fNIRS is a noninvasive, safe, minimally intrusive, and high temporal-resolution technique for real-time and long-term brain imaging. It allows detecting both fast-neuronal and slow-hemodynamic signals. Besides the significant advantages of fNIRS systems, they still suffer from few drawbacks including low spatial-resolution, moderately high-level noise and high-sensitivity to movement. In order to overcome the limitations of currently available non-portable fNIRS systems, we have introduced a new low-power, miniaturized on-chip photodetector front-end intended for portable fNIRS systems. It includes silicon avalanche photodiode (SiAPD), Transimpedance amplifier (TIA), and Quench- Reset circuitry implemented using standard CMOS technologies to operate in both linear and Geiger modes. So it can be applied for both continuous-wave fNIRS (CW-fNIRS) and also single-photon counting applications. Several SiAPDs have been implemented in novel structures and shapes (Rectangular, Octagonal, Dual, Nested, Netted, Quadratic and Hexadecagonal) using different premature edge breakdown prevention techniques. The main characteristics of the SiAPDs are validated and the impact of each parameter and the device simulators (TCAD, COMSOL, etc.) have been studied based on the simulation and measurement results. Proposed techniques exhibit SiAPDs with high avalanche-gain (up to 119), low breakdown-voltage (around 12V) and high photon-detection efficiency (up to 72% in NIR region) in additional to a low dark-count rate (down to 30Hz at 1V excess bias voltage). Three new high gain-bandwidth product (GBW) and low-noise TIAs are introduced and implemented based on distributed-gain concept, logarithmic-amplification and automatic noise-rejection and have been applied in linear-mode of operation. The implemented TIAs offer a power-consumption around 0.4 mW, transimpedance gain of 169 dBO, and input-output current/voltage noises in fA/pV range accompanied with ability to tune the gain, bandwidth and power-consumption in a wide range. The implemented mixed quench-reset circuit (MQC) and controllable MQC (CMQC) front-ends offer a quench-time of 10ns, a maximum power-consumption of 0.4 mW, with a controllable hold-off and reset-times. The on-chip integration of SiAPDs with TIA and photon-counting circuitries has been demonstrated showing improvement of the photodetection-efficiency, specially regarding to the sensitivity, power-consumption and signal-to-noise ratio (SNR) characteristics.

Spray forming process for producing molds, dies and related tooling

DOEpatents

McHugh, Kevin M.; Key, James F.

1998-01-01

A method for spray forming manufacturing of near-net-shape molds, dies and related toolings, wherein liquid material such as molten metal, metallic alloys, or polymers are atomized into fine droplets by a high temperature, high velocity gas and deposited onto a pattern. Quenching of the atomized droplets provides a heat sink, thereby allowing undercooled and partially solidified droplets to be formed in-flight. Composites can be formed by combining the atomized droplets with solid particles such as whiskers or fibers.

Spray forming system for producing molds, dies and related tooling

DOEpatents

McHugh, Kevin M.

2000-01-01

A system for the spray forming manufacturing of near-net-shape molds, dies and related toolings, wherein liquid material such as molten metal, metallic alloys, or polymers are atomized into fine droplets by a high temperature, high velocity gas and deposited onto a pattern. Quenching of the atomized droplets provides a heat sink, thereby allowing undercooled and partially solidified droplets to be formed in-flight. Composites can be formed by combining the atomized droplets with solid particles such as powders, whiskers or fibers.

Spray forming process for producing molds, dies and related tooling

DOEpatents

McHugh, K.M.; Key, J.F.

1998-02-17

A method is disclosed for spray forming manufacturing of near-net-shape molds, dies and related toolings, wherein liquid material such as molten metal, metallic alloys, or polymers are atomized into fine droplets by a high temperature, high velocity gas and deposited onto a pattern. Quenching of the atomized droplets provides a heat sink, thereby allowing undercooled and partially solidified droplets to be formed in-flight. Composites can be formed by combining the atomized droplets with solid particles such as whiskers or fibers. 17 figs.

Modeling of photoluminescence in laser-based lighting systems

NASA Astrophysics Data System (ADS)

Chatzizyrli, Elisavet; Tinne, Nadine; Lachmayer, Roland; Neumann, Jörg; Kracht, Dietmar

2017-12-01

The development of laser-based lighting systems has been the latest step towards a revolution in illumination technology brought about by solid-state lighting. Laser-activated remote phosphor systems produce white light sources with significantly higher luminance than LEDs. The weak point of such systems is often considered to be the conversion element. The high-intensity exciting laser beam in combination with the limited thermal conductivity of ceramic phosphor materials leads to thermal quenching, the phenomenon in which the emission efficiency decreases as temperature rises. For this reason, the aim of the presented study is the modeling of remote phosphor systems in order to investigate their thermal limitations and to calculate the parameters for optimizing the efficiency of such systems. The common approach to simulate remote phosphor systems utilizes a combination of different tools such as ray tracing algorithms and wave optics tools for describing the incident and converted light, whereas the modeling of the conversion process itself, i.e. photoluminescence, in most cases is circumvented by using the absorption and emission spectra of the phosphor material. In this study, we describe the processes involved in luminescence quantum-mechanically using the single-configurational-coordinate diagram as well as the Franck-Condon principle and propose a simulation model that incorporates the temperature dependence of these processes. Following an increasing awareness of climate change and environmental issues, the development of ecologically friendly lighting systems featuring low power consumption and high luminous efficiency is imperative more than ever. The better understanding of laser-based lighting systems is an important step towards that aim as they may improve on LEDs in the near future.

Cosmic evolution of stellar quenching by AGN feedback: clues from the Horizon-AGN simulation

NASA Astrophysics Data System (ADS)

Beckmann, R. S.; Devriendt, J.; Slyz, A.; Peirani, S.; Richardson, M. L. A.; Dubois, Y.; Pichon, C.; Chisari, N. E.; Kaviraj, S.; Laigle, C.; Volonteri, M.

2017-11-01

The observed massive end of the galaxy stellar mass function is steeper than its predicted dark matter halo counterpart in the standard Λ cold dark matter paradigm. In this paper, we investigate the impact of active galactic nuclei (AGN) feedback on star formation in massive galaxies. We isolate the impact of AGN by comparing two simulations from the HORIZON suite, which are identical except that one also includes supermassive black holes (SMBHs) and related feedback models. This allows us to cross-identify individual galaxies between simulations and quantify the effect of AGN feedback on their properties, including stellar mass and gas outflows. We find that massive galaxies (M* ≥ 1011 M⊙) are quenched by AGN feedback to the extent that their stellar masses decrease by up to 80 per cent at z = 0. SMBHs affect their host halo through a combination of outflows that reduce their baryonic mass, particularly for galaxies in the mass range 109 M⊙ ≤ M* ≤ 1011 M⊙, and a disruption of central gas inflows, which limits in situ star formation. As a result, net gas inflows on to massive galaxies, M* ≥ 1011 M⊙, drop by up to 70 per cent. We measure a redshift evolution in the stellar mass ratio of twin galaxies with and without AGN feedback, with galaxies of a given stellar mass showing stronger signs of quenching earlier on. This evolution is driven by a progressive flattening of the MSMBH-M* relation with redshift, particularly for galaxies with M* ≤ 1010 M⊙. MSMBH/M* ratios decrease over time, as falling average gas densities in galaxies curb SMBH growth.

Comprehensive study of interaction between biocompatible PEG-InP/ZnS QDs and bovine serum albumin.

PubMed

Sannaikar, M S; Inamdar, Laxmi S; Pujar, G H; Wari, M N; Balasinor, Nafisa H; Inamdar, S R

2018-05-01

Polyethylene glycol (PEG) surface modified biocompatible InP/ZnS quantum dots (QDs) act as a potential alternative for conventional carcinogenic cadmium-based quantum dots for in vivo and in vitro studies. Comprehensively, we studied the interaction between a model protein bovine serum albumin (BSA) and PEGylated toxic free InP/ZnS QDs using various spectroscopic tools such as absorption, fluorescence quenching, time resolved and synchronous fluorescence spectroscopic measurements. These studies principally show that tryptophan (Trp) residues of BSA have preferable binding affinity towards PEG-InP/ZnS QDs surface and a blue shift in Trp fluorescence emission is a signature of conformational changes in its hydrophobic microenvironment. Photoluminescence (PL) intensity of Trp is quenched by ground state complex formation (static quenching) at room temperature. However, InP/ZnS@BSA conjugates become unstable with increasing temperature and PL intensity of Trp is quenched via dynamic quenching by PEG-InP/ZnS QDs. Experimentally determined thermodynamic parameters for these conjugates have shown spontaneity, entropy driven and exothermic nature of bio-conjugation. The calculated binding affinity (n ≅ 1, Hill coefficient) suggest that the affinity of InP/ZnS QDs for a BSA protein is not dependent on whether or not other BSA proteins are already bound to the QD surface. Energy transfer efficiency (E), Trp residue to InP/ZnS QDs distances and energy transfer rate (k T ) were all obtained from FÖrster resonance energy. Copyright © 2017 John Wiley & Sons, Ltd.

Correlation of cholinergic drug induced quenching of acetylcholinesterase bound thioflavin-T fluorescence with their inhibition activity

NASA Astrophysics Data System (ADS)

Islam, Mullah Muhaiminul; Rohman, Mostofa Ataur; Gurung, Arun Bahadur; Bhattacharjee, Atanu; Aguan, Kripamoy; Mitra, Sivaprasad

2018-01-01

The development of new acetylcholinesterase inhibitors (AChEIs) and subsequent assay of their inhibition efficiency is considered to be a key step for AD treatment. The fluorescence intensity of thioflavin-T (ThT) bound in the active site of acetylcholinesterase (AChE) quenches substantially in presence of standard AChEI drugs due to the dynamic replacement of the fluorophore from the AChE active site as confirmed from steady state emission as well as time-resolved fluorescence anisotropy measurement and molecular dynamics simulation in conjunction with docking calculation. The parametrized % quenching data for individual system shows excellent correlation with enzyme inhibition activity measured independently by standard Ellman AChE assay method in a high throughput plate reader system. The results are encouraging towards design of a fluorescence intensity based AChE inhibition assay method and may provide a better toolset to rapidly evaluate as well as develop newer AChE-inhibitors for AD treatment.

DNS and modeling of the interaction between turbulent premixed flames and walls

NASA Technical Reports Server (NTRS)

Poinsot, T. J.; Haworth, D. C.

1992-01-01

The interaction between turbulent premixed flames and walls is studied using a two-dimensional full Navier-Stokes solver with simple chemistry. The effects of wall distance on the local and global flame structure are investigated. Quenching distances and maximum wall heat fluxes during quenching are computed in laminar cases and are found to be comparable to experimental and analytical results. For turbulent cases, it is shown that quenching distances and maximum heat fluxes remain of the same order as for laminar flames. Based on simulation results, a 'law-of-the-wall' model is derived to describe the interaction between a turbulent premixed flame and a wall. This model is constructed to provide reasonable behavior of flame surface density near a wall under the assumption that flame-wall interaction takes place at scales smaller than the computational mesh. It can be implemented in conjunction with any of several recent flamelet models based on a modeled surface density equation, with no additional constraints on mesh size or time step.

Measurement of the low-energy quenching factor in germanium using an Y 88 / Be photoneutron source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scholz, B. J.; Chavarria, A. E.; Collar, J. I.

2016-12-01

We employ an 88Y/Be photoneutron source to derive the quenching factor for neutron-induced nuclear recoils in germanium, probing recoil energies from a few hundred eVnr to 8.5 keV nr. A comprehensive Monte Carlo simulation of our setup is compared to experimental data employing a Lindhard model with a free electronic energy loss k and an adiabatic correction for sub-keVnr nuclear recoils. The best fit k=0.179±0.001 obtained using a Monte Carlo Markov chain (MCMC) ensemble sampler is in good agreement with previous measurements, confirming the adequacy of the Lindhard model to describe the stopping of few-keV ions in germanium crystals at a temperaturemore » of ~77 K. This value of k corresponds to a quenching factor of 13.7% to 25.3% for nuclear recoil energies between 0.3 and 8.5 keV nr, respectively.« less

Copper-Doped Bioactive Glass as Filler for PMMA-Based Bone Cements: Morphological, Mechanical, Reactivity, and Preliminary Antibacterial Characterization.

PubMed

Miola, Marta; Cochis, Andrea; Kumar, Ajay; Arciola, Carla Renata; Rimondini, Lia; Verné, Enrica

2018-06-06

To promote osteointegration and simultaneously limit bacterial contamination without using antibiotics, we designed innovative composite cements containing copper (Cu)-doped bioactive glass powders. Cu-doped glass powders were produced by a melt and quenching process, followed by an ion-exchange process in a Cu salt aqueous solution. Cu-doped glass was incorporated into commercial polymethyl methacrylate (PMMA)-based cements with different viscosities. The realized composites were characterized in terms of morphology, composition, leaching ability, bioactivity, mechanical, and antibacterial properties. Glass powders appeared well distributed and exposed on the PMMA surface. Composite cements showed good bioactivity, evidencing hydroxyapatite precipitation on the sample surfaces after seven days of immersion in simulated body fluid. The leaching test demonstrated that composite cements released a significant amount of copper, with a noticeable antibacterial effect toward Staphylococcus epidermidis strain. Thus, the proposed materials represent an innovative and multifunctional tool for orthopedic prostheses fixation, temporary prostheses, and spinal surgery.

Molecular Dynamics Simulations of Hydrophobic Residues

NASA Astrophysics Data System (ADS)

Caballero, Diego; Zhou, Alice; Regan, Lynne; O'Hern, Corey

2013-03-01

Molecular recognition and protein-protein interactions are involved in important biological processes. However, despite recent improvements in computational methods for protein design, we still lack a predictive understanding of protein structure and interactions. To begin to address these shortcomings, we performed molecular dynamics simulations of hydrophobic residues modeled as hard spheres with stereo-chemical constraints initially at high temperature, and then quenched to low temperature to obtain local energy minima. We find that there is a range of quench rates over which the probabilities of side-chain dihedral angles for hydrophobic residues match the probabilities obtained for known protein structures. In addition, we predict the side-chain dihedral angle propensities in the core region of the proteins T4, ROP, and several mutants. These studies serve as a first step in developing the ability to quantitatively rank the energies of designed protein constructs. The success of these studies suggests that only hard-sphere dynamics with geometrical constraints are needed for accurate protein structure prediction in hydrophobic cavities and binding interfaces. NSF Grant PHY-1019147

STELLAR DYNAMOS AND CYCLES FROM NUMERICAL SIMULATIONS OF CONVECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubé, Caroline; Charbonneau, Paul, E-mail: dube@astro.umontreal.ca, E-mail: paulchar@astro.umontreal.ca

We present a series of kinematic axisymmetric mean-field αΩ dynamo models applicable to solar-type stars, for 20 distinct combinations of rotation rates and luminosities. The internal differential rotation and kinetic helicity profiles required to calculate source terms in these dynamo models are extracted from a corresponding series of global three-dimensional hydrodynamical simulations of solar/stellar convection, so that the resulting dynamo models end up involving only one free parameter, namely, the turbulent magnetic diffusivity in the convecting layers. Even though the αΩ dynamo solutions exhibit a broad range of morphologies, and sometimes even double cycles, these models manage to reproduce relativelymore » well the observationally inferred relationship between cycle period and rotation rate. On the other hand, they fail in capturing the observed increase of magnetic activity levels with rotation rate. This failure is due to our use of a simple algebraic α-quenching formula as the sole amplitude-limiting nonlinearity. This suggests that α-quenching is not the primary mechanism setting the amplitude of stellar magnetic cycles, with magnetic reaction on large-scale flows emerging as the more likely candidate. This inference is coherent with analyses of various recent global magnetohydrodynamical simulations of solar/stellar convection.« less

Lumped-Element Dynamic Electro-Thermal model of a superconducting magnet

NASA Astrophysics Data System (ADS)

Ravaioli, E.; Auchmann, B.; Maciejewski, M.; ten Kate, H. H. J.; Verweij, A. P.

2016-12-01

Modeling accurately electro-thermal transients occurring in a superconducting magnet is challenging. The behavior of the magnet is the result of complex phenomena occurring in distinct physical domains (electrical, magnetic and thermal) at very different spatial and time scales. Combined multi-domain effects significantly affect the dynamic behavior of the system and are to be taken into account in a coherent and consistent model. A new methodology for developing a Lumped-Element Dynamic Electro-Thermal (LEDET) model of a superconducting magnet is presented. This model includes non-linear dynamic effects such as the dependence of the magnet's differential self-inductance on the presence of inter-filament and inter-strand coupling currents in the conductor. These effects are usually not taken into account because superconducting magnets are primarily operated in stationary conditions. However, they often have significant impact on magnet performance, particularly when the magnet is subject to high ramp rates. Following the LEDET method, the complex interdependence between the electro-magnetic and thermal domains can be modeled with three sub-networks of lumped-elements, reproducing the electrical transient in the main magnet circuit, the thermal transient in the coil cross-section, and the electro-magnetic transient of the inter-filament and inter-strand coupling currents in the superconductor. The same simulation environment can simultaneously model macroscopic electrical transients and phenomena at the level of superconducting strands. The model developed is a very useful tool for reproducing and predicting the performance of conventional quench protection systems based on energy extraction and quench heaters, and of the innovative CLIQ protection system as well.

Study of the rotational-level and temperature dependence of the quenching rate of OH fluorescence due to collisions with water molecules

NASA Technical Reports Server (NTRS)

Koker, Edmond B.

1995-01-01

The importance of the OH radical as an intermediate in many combustion reactions and in atmospheric photochemistry has led many researchers to use it as a diagnostic tool in these processes. The amount of data that has been acquired over the years for this radical is quite considerable. However, the quenching rate of OH with water molecules as a function of temperature and the rotational level of the excited state is not very well understood. The motivation of the studies undertaken is to bridge the gap between the low temperature measurements and the high temperature ones reported in the literature. The technique generally employed in these diagnostics is laser-induced fluorescence (LIF), through which rotational state selective excitation of the radical is possible. Furthermore, in a combustion medium, water is produced in abundance so that knowledge of the quenching rate of OH due to water molecules plays a crucial role in interpreting the data. In general, the precursor to an understanding of the collisional quenching rates of OH involves a characterization of the mode in which the radical is produced; the resulting rotational and translational distribution, followed by a measurement of the OH temperature; and ultimately obtaining the rate constants from the pressure dependence of the fluorescence signal. The experimental implementation of these measurements therefore involved, as a first step, the production of the OH radicals in a microwave discharge cell using water vapor as the source, wherein a hydrogen atom is abstracted from H2O. The second step involved the absorption of photons from the frequency-doubled output of a pulsed amplified, single-frequency cw ring dye laser. By tuning the laser to the peak of the transition and observing the fluorescence decay after the laser pulse, the lifetime of the OH in a particular rotational electronic state was determined (tau = 1.4 microseconds for Q(sub 1)(3)). Knowledge of this parameter led to a determination of the quenching rate. By varying the water vapor pressure in the cell and measuring the lifetime as a function of pressure a linear plot of the quenching rate as a function of pressure was obtained. Using this plot, the quenching cross section was deduced. It has therefore been possible to measure the local translational temperature and the quenching cross section with one laser system.

Hot forming and quenching pilot process development for low cost and low environmental impact manufacturing.

NASA Astrophysics Data System (ADS)

Hall, Roger W.; Foster, Alistair; Herrmann Praturlon, Anja

2017-09-01

The Hot Forming and in-tool Quenching (HFQ®) process is a proven technique to enable complex shaped stampings to be manufactured from high strength aluminium. Its widespread uptake for high volume production will be maximised if it is able to wholly amortise the additional investment cost of this process compared to conventional deep drawing techniques. This paper discusses the use of three techniques to guide some of the development decisions taken during upscaling of the HFQ® process. Modelling of Process timing, Cost and Life-cycle impact were found to be effective tools to identify where development budget could be focused in order to be able to manufacture low cost panels of different sizes from many different alloys in a sustainable way. The results confirm that raw material cost, panel trimming, and artificial ageing were some of the highest contributing factors to final component cost. Additionally, heat treatment and lubricant removal stages played a significant role in the overall life-cycle assessment of the final products. These findings confirmed development priorities as novel furnace design, fast artificial ageing and low-cost alloy development.

Edge safety factor at the onset of plasma disruption during VDEs in JT-60U

NASA Astrophysics Data System (ADS)

Sugihara, Masayoshi; Lukash, Victor; Khayrutdinov, Rustam; Neyatani, Yuzuru

2004-10-01

Detailed examinations of the value of the edge safety factor (qa) at the onset of thermal quench (TQ) during intentional vertical displacement event (VDE) experiments in JT-60U are carried out using two different reconstruction methods, FBI/FBEQU and DINA. The results from the two methods are very similar and show that the TQ occurs when the qa value is in the range between 1.5 and 2. This result suggests that the predictive simulations for VDEs should be performed within this range of q to examine the subsequent differences in the halo currents, plasma movement and other plasma behaviour during the current quench.

On improving the performance of nonphotochemical quenching in CP29 light-harvesting antenna complex

NASA Astrophysics Data System (ADS)

Berman, Gennady P.; Nesterov, Alexander I.; Sayre, Richard T.; Still, Susanne

2016-03-01

We model and simulate the performance of charge-transfer in nonphotochemical quenching (NPQ) in the CP29 light-harvesting antenna-complex associated with photosystem II (PSII). The model consists of five discrete excitonic energy states and two sinks, responsible for the potentially damaging processes and charge-transfer channels, respectively. We demonstrate that by varying (i) the parameters of the chlorophyll-based dimer, (ii) the resonant properties of the protein-solvent environment interaction, and (iii) the energy transfer rates to the sinks, one can significantly improve the performance of the NPQ. Our analysis suggests strategies for improving the performance of the NPQ in response to environmental changes, and may stimulate experimental verification.

Assessment of the microstructure evolution of an austempered ductile iron during austempering process through strain hardening analysis

NASA Astrophysics Data System (ADS)

Donnini, Riccardo; Fabrizi, Alberto; Bonollo, Franco; Zanardi, Franco; Angella, Giuliano

2017-09-01

The aim of this investigation was to determine a procedure based on tensile testing to assess the critical range of austempering times for having the best ausferrite produced through austempering. The austempered ductile iron (ADI) 1050 was quenched at different times during austempering and the quenched samples were tested in tension. The dislocation-density-related constitutive equation proposed by Estrin for materials having high density of geometrical obstacles to dislocation motion, was used to model the flow curves of the tensile tested samples. On the basis of strain hardening theory, the equation parameters were related to the microstructure of the quenched samples and were used to assess the ADI microstructure evolution during austempering. The microstructure evolution was also analysed through conventional optical microscopy, electron back-scattered diffraction technique and transmission electron microscopy. The microstructure observations resulted to be consistent with the assessment based on tensile testing, so the dislocation-density-related constitutive equation was found to be a powerful tool to characterise the evolution of the solid state transformations of austempering.

Monitoring the Photosynthetic Apparatus During Space Flight: Interspecific Variation in Chlorophyll Fluorescence Signatures Induced by Different Root Zone Stresses

NASA Technical Reports Server (NTRS)

Bubenheim, David L.; Patterson, Mark T.; Kliss, Mark H. (Technical Monitor)

1996-01-01

Chlorophyll fluorescence has been used extensively as a tool to indicate stress to the photosynthetic apparatus in green plants. A rise in fluorescence has been attributed to the blockage of photosystem II photochemistry, and patterns of fluorescence decay (quenching) from dark adapted leaves can be related to specific photochemical and non-photochemical deexcitation pathways of light trapped by the photosynthetic apparatus and thus result in characteristically different fluorescence signatures. Four distantly related plant species, Hypocharis radicata (Asteraceae), Brassica rapa (Brassicaceae), Spinacea oleracea (Chenopodiaceae) and Triticum aestivum (Poaceae), were grown hydroponically for three weeks before the initiation of three different root zone stresses (10 mM Cu, 100 mM NaCl and nitrogen deficient nutrition). After 10 days, characteristic fluorescence signatures for each stress could be noted although the degree varied between species. Fast kinetics analysis showed a reduction in plastoquinone pool size for copper and nitrogen stress for all species but a more species specific result with NaCl stress. Photochemical quenching kinetics varied between species and stress treatments from no quenching in S. oleracea in copper treatments to increased photochemical quenching in NaCl treatments. Non-photochemical quenching kinetics demonstrated a distinct pattern between stresses for all species. Copper treatments characteristically exhibited a shallow, flat non-photochemical quenching profile suggesting a general blockage of electron transport whereas NaCl treatments exhibited a slow rising profile that suggested damage to thylakoid acidification kinetics and nitrogen deficiency exhibited a fast rising and declining profile that suggested an altered state 1-state 2 transition regulated by the phosphorylation of LHCII. These results demonstrate characteristic fluorescence signatures for specific plant stresses that may be applied to different, unrelated plant species. In addition, the potential use of chlorophyll fluorescence for both basic research and diagnostic physiology in space biology is presented.

The imprint of rapid star formation quenching on the spectral energy distributions of galaxies

NASA Astrophysics Data System (ADS)

Ciesla, L.; Boselli, A.; Elbaz, D.; Boissier, S.; Buat, V.; Charmandaris, V.; Schreiber, C.; Béthermin, M.; Baes, M.; Boquien, M.; De Looze, I.; Fernández-Ontiveros, J. A.; Pappalardo, C.; Spinoglio, L.; Viaene, S.

2016-01-01

In high density environments, the gas content of galaxies is stripped, leading to a rapid quenching of their star formation activity. This dramatic environmental effect, which is not related to typical passive evolution, is generally not taken into account in the star formation histories (SFHs) usually assumed to perform spectral energy distribution (SED) fitting of these galaxies, yielding a poor fit of their stellar emission and, consequently, biased estimate of the star formation rate (SFR). In this work, we aim at reproducing this rapid quenching using a truncated delayed SFH that we implemented in the SED fitting code CIGALE. We show that the ratio between the instantaneous SFR and the SFR just before the quenching (rSFR) is well constrained as long as rest-frame UV data are available. This SED modeling is applied to the Herschel Reference Survey (HRS) containing isolated galaxies and sources falling in the dense environment of the Virgo cluster. The latter are Hi-deficient because of ram pressure stripping. We show that the truncated delayed SFH successfully reproduces their SED, while typical SFH assumptions fail. A good correlation is found between rSFR and Hi-def, the parameter that quantifies the gas deficiency of cluster galaxies, meaning that SED fitting results can be used to provide a tentative estimate of the gas deficiency of galaxies for which Hi observations are not available. The HRS galaxies are placed on the SFR-M∗ diagram showing that the Hi-deficient sources lie in the quiescent region, thus confirming previous studies. Using the rSFR parameter, we derive the SFR of these sources before quenching and show that they were previously on the main sequence relation. We show that the rSFR parameter is also recovered well for deeply obscured high redshift sources, as well as in the absence of IR data. SED fitting is thus a powerful tool for identifying galaxies that underwent a rapid star formation quenching.

Combining short- and long-range fluorescence reporters with simulations to explore the intramolecular dynamics of an intrinsically disordered protein.

PubMed

Zosel, Franziska; Haenni, Dominik; Soranno, Andrea; Nettels, Daniel; Schuler, Benjamin

2017-10-21

Intrinsically disordered proteins (IDPs) are increasingly recognized as a class of molecules that can exert essential biological functions even in the absence of a well-defined three-dimensional structure. Understanding the conformational distributions and dynamics of these highly flexible proteins is thus essential for explaining the molecular mechanisms underlying their function. Single-molecule fluorescence spectroscopy in combination with Förster resonance energy transfer (FRET) is a powerful tool for probing intramolecular distances and the rapid long-range distance dynamics in IDPs. To complement the information from FRET, we combine it with photoinduced electron transfer (PET) quenching to monitor local loop-closure kinetics at the same time and in the same molecule. Here we employed this combination to investigate the intrinsically disordered N-terminal domain of HIV-1 integrase. The results show that both long-range dynamics and loop closure kinetics on the sub-microsecond time scale can be obtained reliably from a single set of measurements by the analysis with a comprehensive model of the underlying photon statistics including both FRET and PET. A more detailed molecular interpretation of the results is enabled by direct comparison with a recent extensive atomistic molecular dynamics simulation of integrase. The simulations are in good agreement with experiment and can explain the deviation from simple models of chain dynamics by the formation of persistent local secondary structure. The results illustrate the power of a close combination of single-molecule spectroscopy and simulations for advancing our understanding of the dynamics and detailed mechanisms in unfolded and intrinsically disordered proteins.

Combining short- and long-range fluorescence reporters with simulations to explore the intramolecular dynamics of an intrinsically disordered protein

NASA Astrophysics Data System (ADS)

Zosel, Franziska; Haenni, Dominik; Soranno, Andrea; Nettels, Daniel; Schuler, Benjamin

2017-10-01

Intrinsically disordered proteins (IDPs) are increasingly recognized as a class of molecules that can exert essential biological functions even in the absence of a well-defined three-dimensional structure. Understanding the conformational distributions and dynamics of these highly flexible proteins is thus essential for explaining the molecular mechanisms underlying their function. Single-molecule fluorescence spectroscopy in combination with Förster resonance energy transfer (FRET) is a powerful tool for probing intramolecular distances and the rapid long-range distance dynamics in IDPs. To complement the information from FRET, we combine it with photoinduced electron transfer (PET) quenching to monitor local loop-closure kinetics at the same time and in the same molecule. Here we employed this combination to investigate the intrinsically disordered N-terminal domain of HIV-1 integrase. The results show that both long-range dynamics and loop closure kinetics on the sub-microsecond time scale can be obtained reliably from a single set of measurements by the analysis with a comprehensive model of the underlying photon statistics including both FRET and PET. A more detailed molecular interpretation of the results is enabled by direct comparison with a recent extensive atomistic molecular dynamics simulation of integrase. The simulations are in good agreement with experiment and can explain the deviation from simple models of chain dynamics by the formation of persistent local secondary structure. The results illustrate the power of a close combination of single-molecule spectroscopy and simulations for advancing our understanding of the dynamics and detailed mechanisms in unfolded and intrinsically disordered proteins.

Covalent dye attachment influences the dynamics and conformational properties of flexible peptides

PubMed Central

Crevenna, Alvaro H.; Bomblies, Rainer; Lamb, Don C.

2017-01-01

Fluorescence spectroscopy techniques like Förster resonance energy transfer (FRET) and fluorescence correlation spectroscopy (FCS) have become important tools for the in vitro and in vivo investigation of conformational dynamics in biomolecules. These methods rely on the distance-dependent quenching of the fluorescence signal of a donor fluorophore either by a fluorescent acceptor fluorophore (FRET) or a non-fluorescent quencher, as used in FCS with photoinduced electron transfer (PET). The attachment of fluorophores to the molecule of interest can potentially alter the molecular properties and may affect the relevant conformational states and dynamics especially of flexible biomolecules like intrinsically disordered proteins (IDP). Using the intrinsically disordered S-peptide as a model system, we investigate the impact of terminal fluorescence labeling on the molecular properties. We perform extensive molecular dynamics simulations on the labeled and unlabeled peptide and compare the results with in vitro PET-FCS measurements. Experimental and simulated timescales of end-to-end fluctuations were found in excellent agreement. Comparison between simulations with and without labels reveal that the π-stacking interaction between the fluorophore labels traps the conformation of S-peptide in a single dominant state, while the unlabeled peptide undergoes continuous conformational rearrangements. Furthermore, we find that the open to closed transition rate of S-peptide is decreased by at least one order of magnitude by the fluorophore attachment. Our approach combining experimental and in silico methods provides a benchmark for the simulations and reveals the significant effect that fluorescence labeling can have on the conformational dynamics of small biomolecules, at least for inherently flexible short peptides. The presented protocol is not only useful for comparing PET-FCS experiments with simulation results but provides a strategy to minimize the influence on molecular properties when chosing labeling positions for fluorescence experiments. PMID:28542243

Dynamics of Electronically Excited Species in Gaseous and Condensed Phase

DTIC Science & Technology

1989-12-01

heatbath models of condensed phase helium, (3) development of models of condensed phase hydrogen and (4) development of simulation procedures for solution... Modelling and Computer Experiments 93 Introduction 93 Monte Carlo Simulations of Helium Bubble States 94 Heatbath Models f6r Helium Bubble States 114...ILLUSTRATIONS 1 He-He* potential energy curves and couplings for two-state model . 40 2 Cross section for He(1P) quenching to He( 3S) 42 3 Opacity

Deterministic Local Sensitivity Analysis of Augmented Systems - II: Applications to the QUENCH-04 Experiment Using the RELAP5/MOD3.2 Code System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ionescu-Bujor, Mihaela; Jin Xuezhou; Cacuci, Dan G.

2005-09-15

The adjoint sensitivity analysis procedure for augmented systems for application to the RELAP5/MOD3.2 code system is illustrated. Specifically, the adjoint sensitivity model corresponding to the heat structure models in RELAP5/MOD3.2 is derived and subsequently augmented to the two-fluid adjoint sensitivity model (ASM-REL/TF). The end product, called ASM-REL/TFH, comprises the complete adjoint sensitivity model for the coupled fluid dynamics/heat structure packages of the large-scale simulation code RELAP5/MOD3.2. The ASM-REL/TFH model is validated by computing sensitivities to the initial conditions for various time-dependent temperatures in the test bundle of the Quench-04 reactor safety experiment. This experiment simulates the reflooding with water ofmore » uncovered, degraded fuel rods, clad with material (Zircaloy-4) that has the same composition and size as that used in typical pressurized water reactors. The most important response for the Quench-04 experiment is the time evolution of the cladding temperature of heated fuel rods. The ASM-REL/TFH model is subsequently used to perform an illustrative sensitivity analysis of this and other time-dependent temperatures within the bundle. The results computed by using the augmented adjoint sensitivity system, ASM-REL/TFH, highlight the reliability, efficiency, and usefulness of the adjoint sensitivity analysis procedure for computing time-dependent sensitivities.« less

Type 2 pyoverdine from Pseudomonas aeruginosa strain BUP2 as turn-off biosensor for the rapid detection of iron and copper ions in contaminated water.

PubMed

Unni, Kizhakkepowathial Nair; Priji, Prakasan; Sajith, Sreedharan; Faisal, Panichikkal Abdul; Shainy, Karippayi Mattil; Joseph, Abraham; Babu, Moolath Girish; Benjamin, Sailas

2016-09-23

Employing fluorescent quenching mechanism, type 2 pyoverdine (PVD) purified from Pseudomonas aeruginosa strain BUP2 (new strain isolated from the rumen of Malabari goat) was used as a simple, convenient and inexpensive tool for the rapid detection of Fe and Cu ions in contaminated drinking water samples. The fluorescence emitted at λ 460 by PVD (in sterile water), mounted on a glass slide was efficiently quenched by the ions of heavy metals like Fe and Cu. The fluorescence quenching effect of PVD was monitored using UV trans-illuminator, and subsequently quantified and confirmed by spectrofluorimetry. Upon exposure for about 50 sec at 25 °C, this quenching efficiency could directly be assessed by naked eye with the aid of a UV trans-illuminator. The linear range of detection for Fe was 1 to 60 µM, while that of Cu was 1 to 20 µM. The limits of detection at µM concentration for Fe 3+ , Fe 2+ and Cu 2+ were 0.23, 0.24 and 0.38, respectively. The quenching of fluorescence was more pronounced in Fe-PVD system than Cu-PVD, and this observation was in corroboration with the Pearson acid base concept; being a hard acid, Fe 3+ effectively bound with the O-ligands and this ability was less in Cu 2+ , a border line acid. Briefly, this study proposed the use of type 2 PVD as a turn-off biosensor for the rapid screening of heavy metals like Fe and Cu in drinking water, at ppm levels only with the aid of UV trans-illuminator at 25 °C in 50 sec.

Microstructure and hardness of carbon and tool steel quenched with high-frequency currents

NASA Astrophysics Data System (ADS)

Fomin, Aleksandr A.; Fedoseev, Maksim E.; Palkanov, Pavel A.; Voyko, Aleksey V.; Fomina, Marina A.; Koshuro, Vladimir A.; Zakharevich, Andrey M.; Kalganova, Svetlana G.; Rodionov, Igor V.

2018-04-01

In the course of high-temperature treatment with high-frequency currents (HFC) in the range from 600 to 1300 °C, carbon and tool steels are strengthened. After the heat treatment the hardness reaches 64-70 HRC for carbon steel (carbon content 0.4-0.5%) and 68-71 HRC for tool steel 1.3343 (R6M5 steel analogue with 0.9-1.0% C content, W - 5-6 wt%, Mo - 3.5-5.3 wt%, V - 1.3-1.8 wt%, Cr - 3.8-4.3 wt%, Mn+Si - 0.5-1 wt%, Fe - balance). The resulting structure is a carbide network, and in the case of tool steel - complex carbides around a high-strength martensitic phase.

Why do Galaxies Stop Forming Stars? New Evidence for the Role of AGN-feedback in Driving Galaxy Bimodality

NASA Astrophysics Data System (ADS)

Bluck, Asa; Teimoorinia, Hossen; Ellison, Sara L.; Mendel, Trevor

2018-01-01

One of the most striking features of the population of local galaxies is that the distributions of several key galaxy properties are highly bimodal (e.g. color and star formation rate). In general, high mass galaxies in dense environments, with bulge-dominated morphologies and pressure supported kinematics are more frequently passive (non-star forming) than lower mass galaxies in low density environments, with disc-dominated morphologies and rotationally supported kinematics. Understanding which, if any, of these correlations is causally related to the ‘quenching’ of star formation in galaxies remains an active and hotly debated area of investigation in modern astrophysics.Theoretically, a wealth of physical processes have been evoked to account for central galaxy quenching, including halo mass quenching from virial shocks, feedback from active galactic nuclei (AGN; in either the quasar or radio mode), stabilizing torques from central mass concentrations, feedback from supernovae, or even magnetic fields interacting with the hot gas halo.I will present strong new statistical evidence which suggests that the quenched fraction of local central galaxies is primarily related to their central kinematics (Bluck et al. 2016; 2017 in prep.). I will show that this is broadly consistent with quenching from AGN feedback, through a detailed comparison with a semi-analytic model and a cosmological hydrodynamical simulation.Using a sample of over half a million local galaxies from the SDSS DR7, we go on to develop a number of sophisticated techniques, including machine learning with artificial neural networks, to rank the importance of galaxy properties to quenching (Teimoorinia, Bluck & Ellison 2016). We find that properties closely correlated with the central supermassive black hole are highly favoured statistically to predict whether a galaxy will be star forming or not. Perhaps surprisingly, stellar mass and halo mass have no impact on star formation activity in central galaxies selected at a fixed black hole mass; and environment is totally uncorrelated to quenching in centrals.I will conclude by assessing which physical mechanisms for quenching are viable in light of our new results.

Water Powered Tools

NASA Technical Reports Server (NTRS)

1976-01-01

Space Spin-Offs, Inc. under a contract with Lewis Research Center and Marshall Space Flight Center produced a new water-powered saw that cuts through concrete and steel plate reducing danger of explosion or electric shock in rescue and other operations. In prototype unit efficient water-powered turbine drives an 8 inch diameter grinding disk at 6,600 rpm. Exhaust water cools disk and workpiece quenching any sparks produced by cutting head. At maximum power, tool easily cuts through quarter inch steel plate. Adapter heads for chain saws, impact wrenches, heavy duty drills, and power hack saws can be fitted.

Rapid solidification processing system for producing molds, dies and related tooling

DOEpatents

McHugh, Kevin M.

2004-06-08

A system for the spray forming manufacturing of near-net-shape molds, dies and related toolings, wherein liquid material such as molten metal, metallic alloys, or polymers are atomized into fine droplets by a high temperature, high velocity gas and deposited onto a pattern. Quenching of the in-flight atomized droplets provides a heat sink, thereby allowing undercooled and partially solidified droplets to be formed in-flight. Composites can be formed by combining the atomized droplets with solid particles such as powders, whiskers or fibers.

Reducing the content of alloying elements in high-speed steel during heating in salt baths

NASA Astrophysics Data System (ADS)

Kandalovskii, I. P.; Kirillov, F. F.; Dobler, V. I.

1985-07-01

A decrease in molebdenum content occurs in the surface layers during the quench heating of a tool formed from high-speed tungsten-molybdenum steel in a barium chloride salt bath after the required heating time, while a decrease in the tungsten content takes place with more prolonged hold times.

Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Formed Domes

NASA Technical Reports Server (NTRS)

Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

2010-01-01

Simulated service testing (SST) development was required to help qualify a new 2195 aluminum lithium (Al-Li) alloy spin forming dome fabrication process for the National Aeronautics and Space Administration (NASA) Exploration Development Technology Program. The application for the technology is to produce high strength low weight tank components for NASA s next generation launch vehicles. Since plate material is not currently manufactured large enough to fabricate these domes, two plates are joined by means of friction stir welding. The plates are then pre-contour machined to near final thicknesses allowing for a thicker weld land and anticipating the level of stretch induced by the spin forming process. The welded plates are then placed in a spin forming tool and hot stretched using a trace method producing incremental contours. Finally the dome receives a room temperature contour stretch to final dimensions, heat treatment, quenching, and artificial aging to emulate a T-8 condition of temper. Stress corrosion cracking (SCC) tests were also performed by alternate immersion in a sodium chloride (NaCl) solution using the typical double beam assembly and with 4-point loaded specimens and use of bent-beam stress-corrosion test specimens under alternate immersion conditions. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K(sub ISCC)) which to our knowledge has not been determined previously for Al-Li 2195 alloy. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication

Characterizing millisecond intermediates in hemoproteins using rapid-freeze-quench resonance Raman spectroscopy.

PubMed

Matsumura, Hirotoshi; Moënne-Loccoz, Pierre

2014-01-01

The combination of rapid freeze quenching (RFQ) with resonance Raman (RR) spectroscopy represents a unique tool with which to investigate the nature of short-lived intermediates formed during the enzymatic reactions of metalloproteins. Commercially available equipment allows trapping of intermediates within a millisecond to second time scale for low-temperature RR analysis resulting in the direct detection of metal-ligand vibrations and porphyrin skeletal vibrations in hemoproteins. This chapter briefly discusses RFQ-RR studies carried out previously in our laboratory and presents, as a practical example, protocols for the preparation of RFQ samples of the reaction of metmyoglobin with nitric oxide (NO) under anaerobic conditions. Also described are important controls and practical procedures for the analysis of these samples by low-temperature RR spectroscopy.

Properties and mechanisms of immunoglobulins for congenital cytomegalovirus disease.

PubMed

Parruti, Giustino; Polilli, Ennio; Ursini, Tamara; Tontodonati, Monica

2013-12-01

Immunoglobulins are one major component of adaptive immunity to external and resident microorganisms, evolving very early in phylogenesis. They help eukaryotes in controlling infections, mainly through their neutralizing activity, which quenches both the cytopathic and inflammatory potential of invading microorganisms. Cytomegalovirus (CMV)-related disease is generally blunted in seropositive subjects with conserved specific humoral responses. CMV-seropositive pregnant women, in accordance with such evidence, suffer little or no fetal damage when reexposed to CMV. Several seminal experiences and early experimental models confirmed that repeated infusions of immunoglobulins, either with hyperimmune or standard preparations, may help to reduce maternal-fetal CMV transmission, as well as to quench fetal disease upon transmission. This review focused on experimental evidence supporting the potential role of immunoglobulins as a tool to control fetal CMV-related disease in pregnant women.

Two-dimensional Ising model on random lattices with constant coordination number

NASA Astrophysics Data System (ADS)

Schrauth, Manuel; Richter, Julian A. J.; Portela, Jefferson S. E.

2018-02-01

We study the two-dimensional Ising model on networks with quenched topological (connectivity) disorder. In particular, we construct random lattices of constant coordination number and perform large-scale Monte Carlo simulations in order to obtain critical exponents using finite-size scaling relations. We find disorder-dependent effective critical exponents, similar to diluted models, showing thus no clear universal behavior. Considering the very recent results for the two-dimensional Ising model on proximity graphs and the coordination number correlation analysis suggested by Barghathi and Vojta [Phys. Rev. Lett. 113, 120602 (2014), 10.1103/PhysRevLett.113.120602], our results indicate that the planarity and connectedness of the lattice play an important role on deciding whether the phase transition is stable against quenched topological disorder.

Collective Transport Properties of Driven Skyrmions with Random Disorder

NASA Astrophysics Data System (ADS)

Reichhardt, C.; Ray, D.; Reichhardt, C. J. Olson

2015-05-01

We use particle-based simulations to examine the static and driven collective phases of Skyrmions interacting with random quenched disorder. We show that nondissipative effects due to the Magnus term reduce the depinning threshold and strongly affect the Skyrmion motion and the nature of the dynamic phases. The quenched disorder causes the Hall angle to become drive dependent in the moving Skyrmion phase, while different flow regimes produce distinct signatures in the transport curves. For weak disorder, the Skyrmions form a pinned crystal and depin elastically, while for strong disorder the system forms a pinned amorphous state that depins plastically. At high drives the Skyrmions can dynamically reorder into a moving crystal, with the onset of reordering determined by the strength of the Magnus term.

Size-dependent penetrant diffusion in polymer glasses.

PubMed

Meng, Dong; Zhang, Kai; Kumar, Sanat K

2018-05-18

Molecular Dynamics simulations are used to understand the underpinning basis of the transport of gas-like solutes in deeply quenched polymeric glasses. As found in previous work, small solutes, with sizes smaller than 0.15 times the chain monomer size, move as might be expected in a medium with large pores. In contrast, the motion of larger solutes is activated and is strongly facilitated by matrix motion. In particular, solute motion is coupled to the local elastic fluctuations of the matrix as characterized by the Debye-Waller factor. While similar ideas have been previously proposed for the viscosity of supercooled liquids above their glass transition, to our knowledge, this is the first illustration of this concept in the context of solute mass transport in deeply quenched polymer glasses.

On improving the performance of nonphotochemical quenching in CP29 light-harvesting antenna complex

DOE PAGES

Berman, Gennady Petrovich; Nesterov, Alexander I.; Sayre, Richard Thomas; ...

2016-02-02

In this study, we model and simulate the performance of charge-transfer in nonphotochemical quenching (NPQ) in the CP29 light-harvesting antenna-complex associated with photosystem II (PSII). The model consists of five discrete excitonic energy states and two sinks, responsible for the potentially damaging processes and charge-transfer channels, respectively. We demonstrate that by varying (i) the parameters of the chlorophyll-based dimer, (ii) the resonant properties of the protein-solvent environment interaction, and (iii) the energy transfer rates to the sinks, one can significantly improve the performance of the NPQ. In conclusion, our analysis suggests strategies for improving the performance of the NPQ inmore » response to environmental changes, and may stimulate experimental verification.« less

Rényi Entropies from Random Quenches in Atomic Hubbard and Spin Models.

PubMed

Elben, A; Vermersch, B; Dalmonte, M; Cirac, J I; Zoller, P

2018-02-02

We present a scheme for measuring Rényi entropies in generic atomic Hubbard and spin models using single copies of a quantum state and for partitions in arbitrary spatial dimensions. Our approach is based on the generation of random unitaries from random quenches, implemented using engineered time-dependent disorder potentials, and standard projective measurements, as realized by quantum gas microscopes. By analyzing the properties of the generated unitaries and the role of statistical errors, with respect to the size of the partition, we show that the protocol can be realized in existing quantum simulators and used to measure, for instance, area law scaling of entanglement in two-dimensional spin models or the entanglement growth in many-body localized systems.

Rényi Entropies from Random Quenches in Atomic Hubbard and Spin Models

NASA Astrophysics Data System (ADS)

Elben, A.; Vermersch, B.; Dalmonte, M.; Cirac, J. I.; Zoller, P.

2018-02-01

We present a scheme for measuring Rényi entropies in generic atomic Hubbard and spin models using single copies of a quantum state and for partitions in arbitrary spatial dimensions. Our approach is based on the generation of random unitaries from random quenches, implemented using engineered time-dependent disorder potentials, and standard projective measurements, as realized by quantum gas microscopes. By analyzing the properties of the generated unitaries and the role of statistical errors, with respect to the size of the partition, we show that the protocol can be realized in existing quantum simulators and used to measure, for instance, area law scaling of entanglement in two-dimensional spin models or the entanglement growth in many-body localized systems.

Fast Preparation of Critical Ground States Using Superluminal Fronts

NASA Astrophysics Data System (ADS)

Agarwal, Kartiek; Bhatt, R. N.; Sondhi, S. L.

2018-05-01

We propose a spatiotemporal quench protocol that allows for the fast preparation of ground states of gapless models with Lorentz invariance. Assuming the system initially resides in the ground state of a corresponding massive model, we show that a superluminally moving "front" that locally quenches the mass, leaves behind it (in space) a state arbitrarily close to the ground state of the gapless model. Importantly, our protocol takes time O (L ) to produce the ground state of a system of size ˜Ld (d spatial dimensions), while a fully adiabatic protocol requires time ˜O (L2) to produce a state with exponential accuracy in L . The physics of the dynamical problem can be understood in terms of relativistic rarefaction of excitations generated by the mass front. We provide proof of concept by solving the proposed quench exactly for a system of free bosons in arbitrary dimensions, and for free fermions in d =1 . We discuss the role of interactions and UV effects on the free-theory idealization, before numerically illustrating the usefulness of the approach via simulations on the quantum Heisenberg spin chain.

Solvent as electron donor: Donor/acceptor electronic coupling is a dynamical variable

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castner, E.W. Jr.; Kennedy, D.; Cave, R.J.

2000-04-06

The authors combine analysis of measurements by femtosecond optical spectroscopy, computer simulations, and the generalized Mulliken-Hush (GMH) theory in the study of electron-transfer reactions and electron donor-acceptor interactions. The study focus is on ultrafast photoinduced electron-transfer reactions from aromatic amine solvent donors to excited-state acceptors. The experimental results from femtosecond dynamical measurements fall into three categories: six coumarin acceptors reductively quenched by N,N-dimethylaniline (DMA), eight electron-donating amine solvents reductively quenching coumarin 152 (7-(dimethylamino)-4-(trifluoromethyl)-coumarin), and reductive quenching dynamics of two coumarins by DMA as a function of dilution in the nonreactive solvents toluene and chlorobenzene. Applying a combination of molecular dynamicsmore » trajectories, semiempirical quantum mechanical calculations (of the relevant adiabatic electronic states), and GMH theory to the C152/DMA photoreaction, the authors calculate the electron donor/acceptor interaction parameter H{sub DA} at various time frames, H{sub DA} is strongly modulated by both inner-sphere and outer-sphere nuclear dynamics, leading us to conclude that H{sub DA} must be considered as a dynamical variable.« less

Chemically reacting fluid flow in exoplanet and brown dwarf atmospheres

NASA Astrophysics Data System (ADS)

Bordwell, Baylee; Brown, Benjamin P.; Oishi, Jeffrey S.

2016-11-01

In the past few decades, spectral observations of planets and brown dwarfs have demonstrated significant deviations from predictions in certain chemical abundances. Starting with Jupiter, these deviations were successfully explained to be the effect of fast dynamics on comparatively slow chemical reactions. These dynamical effects are treated using mixing length theory in what is known as the "quench" approximation. In these objects, however, both radiative and convective zones are present, and it is not clear that this approximation applies. To resolve this issue, we solve the fully compressible equations of fluid dynamics in a matched polytropic atmosphere using the state-of-the-art pseudospectral simulation framework Dedalus. Through the inclusion of passive tracers, we explore the transport properties of convective and radiative zones, and verify the classical eddy diffusion parameterization. With the addition of active tracers, we examine the interactions between dynamical and chemical processes using abstract chemical reactions. By locating the quench point (the point at which the dynamical and chemical timescales are the same) in different dynamical regimes, we test the quench approximation, and generate prescriptions for the exoplanet and brown dwarf communities.

Spectroscopic studies on the interaction of chromium (VI) and chromium (III) with keyhole limpet hemocyanin.

PubMed

Fan, Yulan; Zeng, Guidi; Liu, Jingyi; Chen, Huifang; Xue, Jun; Wu, Yongquan; Li, Xun

2017-03-01

The interactions of keyhole limpet hemocyanin (KLH) with chromium nitrate, potassium dichromate, and chromate were investigated using fluorescence, UV-vis absorption and circular dichroism (CD) spectroscopy under simulated physiological conditions. The experimental results showed that the different forms of chromium could quench the intrinsic fluorescence of KLH following a static quenching mechanism rather than by dynamic collision, which indicated that a Cr-KLH complex was formed. The Stern-Volmer quenching constants for the interaction indicated that the binding reaction of KLH with Cr(VI) was stronger the binding of KLH with Cr(III). The thermodynamic values for binding of Cr(VI) to KLH are ΔH > 0 and ΔS > 0. By contrast, the values for the interaction of Cr(III) with KLH are ΔH < 0 and ΔS < 0. The results of synchronous fluorescence, UV-vis absorption and CD spectroscopy showed that the α-helical secondary structure and conformation of KLH were altered by different forms of chromium. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

OPERATIONAL EXPERIENCE WITH BEAM ABORT SYSTEM FOR SUPERCONDUCTING UNDULATOR QUENCH MITIGATION*

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harkay, Katherine C.; Dooling, Jeffrey C.; Sajaev, Vadim

A beam abort system has been implemented in the Advanced Photon Source storage ring. The abort system works in tandem with the existing machine protection system (MPS), and its purpose is to control the beam loss location and, thereby, minimize beam loss-induced quenches at the two superconducting undulators (SCUs). The abort system consists of a dedicated horizontal kicker designed to kick out all the bunches in a few turns after being triggered by MPS. The abort system concept was developed on the basis of single- and multi-particle tracking simulations using elegant and bench measurements of the kicker pulse. Performance ofmore » the abort system—kick amplitudes and loss distributions of all bunches—was analyzed using beam position monitor (BPM) turn histories, and agrees reasonably well with the model. Beam loss locations indicated by the BPMs are consistent with the fast fiber-optic beam loss monitor (BLM) diagnostics described elsewhere [1,2]. Operational experience with the abort system, various issues that were encountered, limitations of the system, and quench statistics are described.« less

Atomistic insights into the nanosecond long amorphization and crystallization cycle of nanoscale G e2S b2T e5 : An ab initio molecular dynamics study

NASA Astrophysics Data System (ADS)

Branicio, Paulo S.; Bai, Kewu; Ramanarayan, H.; Wu, David T.; Sullivan, Michael B.; Srolovitz, David J.

2018-04-01

The complete process of amorphization and crystallization of the phase-change material G e2S b2T e5 is investigated using nanosecond ab initio molecular dynamics simulations. Varying the quench rate during the amorphization phase of the cycle results in the generation of a variety of structures from entirely crystallized (-0.45 K/ps) to entirely amorphized (-16 K/ps). The 1.5-ns annealing simulations indicate that the crystallization process depends strongly on both the annealing temperature and the initial amorphous structure. The presence of crystal precursors (square rings) in the amorphous matrix enhances nucleation/crystallization kinetics. The simulation data are used to construct a combined continuous-cooling-transformation (CCT) and temperature-time-transformation (TTT) diagram. The nose of the CCT-TTT diagram corresponds to the minimum time for the onset of homogenous crystallization and is located at 600 K and 70 ps. That corresponds to a critical cooling rate for amorphization of -4.5 K/ps. The results, in excellent agreement with experimental observations, suggest that a strategy that utilizes multiple quench rates and annealing temperatures may be used to effectively optimize the reversible switching speed and enable fast and energy-efficient phase-change memories.

Modeling and Simulation of Plasma-Assisted Ignition and Combustion

DTIC Science & Technology

2013-10-01

local plasma chemistry effects over heat transport in achieving “volumetric” ignition using pulse nanosecond discharges. •detailed parametric studies...electrical breakdown • cathode sheath formation • electron impact dynamics PLASMA DISCHARGE DYNAMICS Plasma Chemistry Ionization, Excitation...quenching of excited species nonequilibrium plasma chemistry low temperature radical chemistry high temperature combustion chemistry School of

Three-Dimensional Upward Flame Spreading in Partial-Gravity Buoyant Flows

NASA Technical Reports Server (NTRS)

Sacksteder, Kurt R.; Feier, Ioan I.; Shih, Hsin-Yi; T'ien, James S.

2001-01-01

Reduced-gravity environments have been used to establish low-speed, purely forced flows for both opposed- and concurrent-flow flame spread studies. Altenkirch's group obtained spacebased experimental results and developed unsteady, two-dimensional numerical simulations of opposed-flow flame spread including gas-phase radiation, primarily away from the flammability limit for thin fuels, but including observations of thick fuel quenching in quiescent environments. T'ien's group contributed some early flame spreading results for thin fuels both in opposed flow and concurrent flow regimes, with more focus on near-limit conditions. T'ien's group also developed two- and three-dimensional numerical simulations of concurrent-flow flame spread incorporating gas-phase radiative models, including predictions of a radiatively-induced quenching limit reached in very low-speed air flows. Radiative quenching has been subsequently observed in other studies of combustion in very low-speed flows including other flame spread investigations, droplet combustion and homogeneous diffusion flames, and is the subject of several contemporary studies reported in this workshop. Using NASA aircraft flying partial-gravity "parabolic" trajectories, flame spreading in purely buoyant, opposed-flow (downward burning) has been studied. These results indicated increases in flame spread rates and enhanced flammability (lower limiting atmospheric oxygen content) as gravity levels were reduced from normal Earth gravity, and were consistent with earlier data obtained by Altenkirch using a centrifuge. In this work, experimental results and a three-dimensional numerical simulation of upward flame spreading in variable partial-gravity environments were obtained including some effects of reduced pressure and variable sample width. The simulation provides physical insight for interpreting the experimental results and shows the intrinsic 3-D nature of buoyant, upward flame spreading. This study is intended to link the evolving understanding of flame spreading in purely-forced flows to the purely-buoyant flow environment, particularly in the concurrent flow regime; provide additional insight into the existence of steady flame spread in concurrent flows; and stimulate direct comparisons between opposed- and concurrent-flow flame spread. Additionally, this effort is intended to provide direct practical understanding applicable to fire protection planning for the habitable facilities in partial gravity environments of anticipated Lunar and Martian explorations.

Complete suppression of the fluorophore fluorescence by combined effect of multiple fluorescence quenching groups: A fluorescent sensor for Cu²⁺ with zero background signals.

PubMed

Long, Lingliang; Wu, Yanjun; Wang, Lin; Gong, Aihua; Hu, Rongfeng; Zhang, Chi

2016-02-18

The reaction-based fluorescent sensors have attracted increasing attention in the past decades. However, the application of these sensors for accurate sensing was significantly retarded by the background fluorescence from the sensors themselves. In this work, we demonstrated a novel strategy that the background fluorescence of the sensor could be completely eliminated by the combined effect of multiple fluorescence quenching groups. Based on this new strategy, as proof-of-principle study, a fluorescent sensor (CuFS) for Cu(2+) was judiciously developed. In CuFS, three types of fluorescence quenching groups were directly tethered to a commonly used coumarin fluorophore. The fluorescence of coumarin fluorophore in CuFS was completely suppressed by the combined effect of these fluorescence quenching groups. Upon treatment with 22 μM Cu(2+), sensor CuFS achieved a dramatic fluorescence enhancement (fluorescence intensity enhanced up to 811-fold) centered at 469 nm. The detection limits was determined to be 12.3 nM. The fluorescence intensity enhancement also showed a good linearity with the Cu(2+) concentration in the range of 12.3 nM to 2 μM. By fabricating test strips, sensor CuFS can be utilized as a simple tool to detect Cu(2+) in water samples. Furthermore, the fluorescent sensor was successfully applied in detecting different concentration of Cu(2+) in living cells. Copyright © 2015 Elsevier B.V. All rights reserved.

Estimation of ring tensile properties of steam oxidized Zircaloy-4 fuel cladding under simulated LOCA condition

NASA Astrophysics Data System (ADS)

Shriwastaw, R. S.; Sawarn, Tapan K.; Banerjee, Suparna; Rath, B. N.; Dubey, J. S.; Kumar, Sunil; Singh, J. L.; Bhasin, Vivek

2017-09-01

The present study involves the estimation of ring tensile properties of Indian Pressurised Heavy Water Reactor (IPHWR) fuel cladding made of Zircaloy-4, subjected to experiments under a simulated loss-of-coolant-accident (LOCA) condition. Isothermal steam oxidation experiments were conducted on clad tube specimens at temperatures ranging from 900 to 1200 °C at an interval of 50 °C for different soaking periods with subsequent quenching in water at ambient temperature. The specimens, which survived quenching, were then subjected to ambient temperature ring tension test (RTT). The microstructure was correlated with the mechanical properties. The yield strength (YS) and ultimate tensile strength (UTS) increased initially with rise in oxidation temperature and time duration but then decreased with further increase in oxidation. Ductility is adversely affected with rising oxidation temperature and longer holding time. A higher fraction of load bearing phase and lower oxygen content in it ensures higher residual ductility. Cladding shows almost zero ductility behavior in RIT when load bearing phase fraction is less than 0.72 and its average oxygen concentration is greater than 0.58 wt%.

Monte-Carlo simulations of the clean and disordered contact process in three space dimensions

NASA Astrophysics Data System (ADS)

Vojta, Thomas

2013-03-01

The absorbing-state transition in the three-dimensional contact process with and without quenched randomness is investigated by means of Monte-Carlo simulations. In the clean case, a reweighting technique is combined with a careful extrapolation of the data to infinite time to determine with high accuracy the critical behavior in the three-dimensional directed percolation universality class. In the presence of quenched spatial disorder, our data demonstrate that the absorbing-state transition is governed by an unconventional infinite-randomness critical point featuring activated dynamical scaling. The critical behavior of this transition does not depend on the disorder strength, i.e., it is universal. Close to the disordered critical point, the dynamics is characterized by the nonuniversal power laws typical of a Griffiths phase. We compare our findings to the results of other numerical methods, and we relate them to a general classification of phase transitions in disordered systems based on the rare region dimensionality. This work has been supported in part by the NSF under grants no. DMR-0906566 and DMR-1205803.

Experimental and Theoretical Insights into the Inhibition Mechanism of Prion Fibrillation by Resveratrol and its Derivatives.

PubMed

Li, Lanlan; Zhu, Yongchang; Zhou, Shuangyan; An, Xiaoli; Zhang, Yan; Bai, Qifeng; He, Yong-Xing; Liu, Huanxiang; Yao, Xiaojun

2017-12-20

Resveratrol and its derivatives have been shown to display beneficial effects to neurodegenerative diseases. However, the molecular mechanism of resveratrol and its derivatives on prion conformational conversion is poorly understood. In this work, the interaction mechanism between prion and resveratrol as well as its derivatives was investigated using steady-state fluorescence quenching, Thioflavin T binding assay, Western blotting, and molecular dynamics simulation. Protein fluorescence quenching method and Thioflavin T assay revealed that resveratrol and its derivatives could interact with prion and interrupt prion fibril formation. Molecular dynamics simulation results indicated that resveratrol can stabilize the PrP 127-147 peptide mainly through π-π stacking interactions between resveratrol and Tyr128. The hydrogen bonds interactions between resveratrol and the PrP 127-147 peptide could further reduce the flexibility and the propensity to aggregate. The results of this study not only can provide useful information about the interaction mechanism between resveratrol and prion, but also can provide useful clues for further design of new inhibitors inhibiting prion aggregation.

quenched-smFISH: Counting small RNA in Pathogenic Bacteria

NASA Astrophysics Data System (ADS)

Shepherd, Douglas; Li, Nan; Micheva-Viteva, Sofiya; Munsky, Brian; Hong-Geller, Elizabeth; Werner, James

2014-03-01

Here, we present a modification to single-molecule fluorescence in situ hybridization, quenched smFISH (q-smFISH), that enables quantitative detection and analysis of small RNA (sRNA) expressed in bacteria. We show that short nucleic acid targets can be detected when the background of unbound singly dye-labeled DNA oligomers is reduced through hybridization with a set of complementary DNA oligomers labeled with a fluorescence quencher. Exploiting an automated, multi-color wide-field microscope and GPU-accelerated data analysis package, we analyzed the statistics of sRNA expression in thousands of individual Yersinia pseudotuberculosis and Yersinia pestis bacteria before and during a simulated infection. Before infection, we find only a small fraction of either bacteria express the small RNAs YSR35 or YSP8. The copy numbers of these RNA are increased during simulated infection, suggesting a role in pathogenesis. The ability to directly quantify expression level changes of sRNA in single cells as a function of external stimuli provides key information on the role of sRNA in bacterial regulatory networks.

Conceptual designs of conduction cooled MgB2 magnets for 1.5 and 3.0 T full body MRI systems

NASA Astrophysics Data System (ADS)

Baig, Tanvir; Amin, Abdullah Al; Deissler, Robert J.; Sabri, Laith; Poole, Charles; Brown, Robert W.; Tomsic, Michael; Doll, David; Rindfleisch, Matthew; Peng, Xuan; Mendris, Robert; Akkus, Ozan; Sumption, Michael; Martens, Michael

2017-04-01

Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB2 superconductor are presented. The sizes, locations, and number of turns in the eight coil bundles are determined using optimization methods that minimize the amount of superconducting wire and produce magnetic fields with an inhomogeneity of less than 10 ppm over a 45 cm diameter spherical volume. MgB2 superconducting wire is assessed in terms of the transport, thermal, and mechanical properties for these magnet designs. Careful calculations of the normal zone propagation velocity and minimum quench energies provide support for the necessity of active quench protection instead of passive protection for medium temperature superconductors such as MgB2. A new ‘active’ protection scheme for medium T c based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB2 wire is presented. Finite difference calculations of the quench propagation and temperature rise during a quench conclude that active intervention is needed to reduce the temperature rise in the coil bundles and prevent damage to the superconductor. Comprehensive multiphysics and multiscale analytical and finite element analysis of the mechanical stress and strain in the MgB2 wire and epoxy for these designs are presented for the first time. From mechanical and thermal analysis of our designs we conclude there would be no damage to such a magnet during the manufacturing or operating stages, and that the magnet would survive various quench scenarios. This comprehensive set of magnet design considerations and analyses demonstrate the overall viability of 1.5 and 3.0 T MgB2 magnet designs.

Isotropic in-plane quenched disorder and dilution induce a robust nematic state in electron-doped pnictides

DOE PAGES

Liang, Shuhua; Bishop, Christopher B.; Moreo, Adriana; ...

2015-09-21

The phase diagram of electron-doped pnictides is studied varying the temperature, electronic density, and isotropic in-plane quenched disorder strength and dilution by means of computational techniques applied to a three-orbital (xz,yz,xy) spin-fermion model with lattice degrees of freedom. In experiments, chemical doping introduces disorder but in theoretical studies the relationship between electronic doping and the randomly located dopants, with their associated quenched disorder, is difficult to address. Moreover, in this publication, the use of computational techniques allows us to study independently the effects of electronic doping, regulated by a global chemical potential, and impurity disorder at randomly selected sites. Surprisingly,more » our Monte Carlo simulations reveal that the fast reduction with doping of the N eel T N and the structural T S transition temperatures, and the concomitant stabilization of a robust nematic state, is primarily controlled in our model by the magnetic dilution associated with the in-plane isotropic disorder introduced by Fe substitution. In the doping range studied, changes in the Fermi surface produced by electron doping affect only slightly both critical temperatures. Our results also suggest that the specific material-dependent phase diagrams experimentally observed could be explained as a consequence of the variation in disorder profiles introduced by the different dopants. Finally, our findings are also compatible with neutron scattering and scanning tunneling microscopy, unveiling a patchy network of locally magnetically ordered clusters with anisotropic shapes, even though the quenched disorder is locally isotropic. Our study reveals a remarkable and unexpected degree of complexity in pnictides: the fragile tendency to nematicity intrinsic of translational invariant electronic systems needs to be supplemented by quenched disorder and dilution to stabilize the robust nematic phase experimentally found in electron-doped 122 compounds.« less

MUFASA: the strength and evolution of galaxy conformity in various tracers

NASA Astrophysics Data System (ADS)

Rafieferantsoa, Mika; Davé, Romeel

2018-03-01

We investigate galaxy conformity using the MUFASA cosmological hydrodynamical simulation. We show a bimodal distribution in galaxy colour with radius, albeit with too many low-mass quenched satellite galaxies compared to observations. MUFASA produces conformity in observed properties such as colour, specific star formation rate (sSFR), and H I content, i.e. neighbouring galaxies have similar properties. We see analogous trends in other properties such as in environment, stellar age, H2 content, and metallicity. We introduce quantifying conformity using S(R), measuring the relative difference in upper and lower quartile properties of the neighbours. We show that low-mass and non-quenched haloes have weak conformity (S(R)≲ 0.5) extending to large projected radii R in all properties, while high-mass and quenched haloes have strong conformity (S(R)˜ 1) that diminishes rapidly with R and disappears at R ≳ 1 Mpc. S(R) is strongest for environment in low-mass haloes, and sSFR (or colour) in high-mass haloes, and is dominated by one-halo conformity with the exception of H I in small haloes. Metallicity shows a curious anticonformity in massive haloes. Tracking the evolution of conformity for z = 0 galaxies back in time shows that conformity broadly emerges as a late-time (z ≲ 1) phenomenon. However, for fixed halo mass bins, conformity is fairly constant with redshift out to z ≳ 2. These trends are consistent with the idea that strong conformity only emerges once haloes grow above MUFASA's quenching mass scale of ˜1012 M⊙. A quantitative measure of conformity in various properties, along with its evolution, thus represents a new and stringent test of the impact of quenching on environment within current galaxy formation models.

Isotropic in-plane quenched disorder and dilution induce a robust nematic state in electron-doped pnictides

NASA Astrophysics Data System (ADS)

Liang, Shuhua; Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio

2015-09-01

The phase diagram of electron-doped pnictides is studied varying the temperature, electronic density, and isotropic in-plane quenched disorder strength and dilution by means of computational techniques applied to a three-orbital (x z ,y z ,x y ) spin-fermion model with lattice degrees of freedom. In experiments, chemical doping introduces disorder but in theoretical studies the relationship between electronic doping and the randomly located dopants, with their associated quenched disorder, is difficult to address. In this publication, the use of computational techniques allows us to study independently the effects of electronic doping, regulated by a global chemical potential, and impurity disorder at randomly selected sites. Surprisingly, our Monte Carlo simulations reveal that the fast reduction with doping of the Néel TN and the structural TS transition temperatures, and the concomitant stabilization of a robust nematic state, is primarily controlled in our model by the magnetic dilution associated with the in-plane isotropic disorder introduced by Fe substitution. In the doping range studied, changes in the Fermi surface produced by electron doping affect only slightly both critical temperatures. Our results also suggest that the specific material-dependent phase diagrams experimentally observed could be explained as a consequence of the variation in disorder profiles introduced by the different dopants. Our findings are also compatible with neutron scattering and scanning tunneling microscopy, unveiling a patchy network of locally magnetically ordered clusters with anisotropic shapes, even though the quenched disorder is locally isotropic. This study reveals a remarkable and unexpected degree of complexity in pnictides: the fragile tendency to nematicity intrinsic of translational invariant electronic systems needs to be supplemented by quenched disorder and dilution to stabilize the robust nematic phase experimentally found in electron-doped 122 compounds.

Conceptual designs of conduction cooled MgB2 magnets for 1.5 and 3.0T full body MRI systems

PubMed Central

Baig, Tanvir; Al Amin, Abdullah; Deissler, Robert J; Sabri, Laith; Poole, Charles; Brown, Robert W; Tomsic, Michael; Doll, David; Rindfleisch, Matthew; Peng, Xuan; Mendris, Robert; Akkus, Ozan; Sumption, Michael; Martens, Michael

2017-01-01

Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB2 superconductor are presented. The sizes, locations, and number of turns in the eight coil bundles are determined using optimization methods that minimize the amount of superconducting wire and produce magnetic fields with an inhomogeneity of less than 10 ppm over a 45 cm diameter spherical volume. MgB2 superconducting wire is assessed in terms of the transport, thermal, and mechanical properties for these magnet designs. Careful calculations of the normal zone propagation velocity and minimum quench energies provide support for the necessity of active quench protection instead of passive protection for medium temperature superconductors such as MgB2. A new ‘active’ protection scheme for medium Tc based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB2 wire is presented. Finite difference calculations of the quench propagation and temperature rise during a quench conclude that active intervention is needed to reduce the temperature rise in the coil bundles and prevent damage to the superconductor. Comprehensive multiphysics and multiscale analytical and finite element analysis of the mechanical stress and strain in the MgB2 wire and epoxy for these designs are presented for the first time. From mechanical and thermal analysis of our designs we conclude there would be no damage to such a magnet during the manufacturing or operating stages, and that the magnet would survive various quench scenarios. This comprehensive set of magnet design considerations and analyses demonstrate the overall viability of 1.5 and 3.0 T MgB2 magnet designs. PMID:29170604

Conceptual designs of conduction cooled MgB2 magnets for 1.5 and 3.0T full body MRI systems.

PubMed

Baig, Tanvir; Al Amin, Abdullah; Deissler, Robert J; Sabri, Laith; Poole, Charles; Brown, Robert W; Tomsic, Michael; Doll, David; Rindfleisch, Matthew; Peng, Xuan; Mendris, Robert; Akkus, Ozan; Sumption, Michael; Martens, Michael

2017-04-01

Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB 2 superconductor are presented. The sizes, locations, and number of turns in the eight coil bundles are determined using optimization methods that minimize the amount of superconducting wire and produce magnetic fields with an inhomogeneity of less than 10 ppm over a 45 cm diameter spherical volume. MgB 2 superconducting wire is assessed in terms of the transport, thermal, and mechanical properties for these magnet designs. Careful calculations of the normal zone propagation velocity and minimum quench energies provide support for the necessity of active quench protection instead of passive protection for medium temperature superconductors such as MgB 2 . A new 'active' protection scheme for medium T c based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB 2 wire is presented. Finite difference calculations of the quench propagation and temperature rise during a quench conclude that active intervention is needed to reduce the temperature rise in the coil bundles and prevent damage to the superconductor. Comprehensive multiphysics and multiscale analytical and finite element analysis of the mechanical stress and strain in the MgB 2 wire and epoxy for these designs are presented for the first time. From mechanical and thermal analysis of our designs we conclude there would be no damage to such a magnet during the manufacturing or operating stages, and that the magnet would survive various quench scenarios. This comprehensive set of magnet design considerations and analyses demonstrate the overall viability of 1.5 and 3.0 T MgB 2 magnet designs.

Kinetic Monte Carlo simulation of the efficiency roll-off, emission color, and degradation of organic light-emitting diodes (Presentation Recording)

NASA Astrophysics Data System (ADS)

Coehoorn, Reinder; van Eersel, Harm; Bobbert, Peter A.; Janssen, Rene A. J.

2015-10-01

The performance of Organic Light Emitting Diodes (OLEDs) is determined by a complex interplay of the charge transport and excitonic processes in the active layer stack. We have developed a three-dimensional kinetic Monte Carlo (kMC) OLED simulation method which includes all these processes in an integral manner. The method employs a physically transparent mechanistic approach, and is based on measurable parameters. All processes can be followed with molecular-scale spatial resolution and with sub-nanosecond time resolution, for any layer structure and any mixture of materials. In the talk, applications to the efficiency roll-off, emission color and lifetime of white and monochrome phosphorescent OLEDs [1,2] are demonstrated, and a comparison with experimental results is given. The simulations show to which extent the triplet-polaron quenching (TPQ) and triplet-triplet-annihilation (TTA) contribute to the roll-off, and how the microscopic parameters describing these processes can be deduced properly from dedicated experiments. Degradation is treated as a result of the (accelerated) conversion of emitter molecules to non-emissive sites upon a triplet-polaron quenching (TPQ) process. The degradation rate, and hence the device lifetime, is shown to depend on the emitter concentration and on the precise type of TPQ process. Results for both single-doped and co-doped OLEDs are presented, revealing that the kMC simulations enable efficient simulation-assisted layer stack development. [1] H. van Eersel et al., Appl. Phys. Lett. 105, 143303 (2014). [2] R. Coehoorn et al., Adv. Funct. Mater. (2015), publ. online (DOI: 10.1002/adfm.201402532)

On the Importance of High Frequency Gravity Waves for Ice Nucleation in the Tropical Tropopause Layer

NASA Technical Reports Server (NTRS)

Jensen, Eric J.

2016-01-01

Recent investigations of the influence of atmospheric waves on ice nucleation in cirrus have identified a number of key processes and sensitivities: (1) ice concentrations produced by homogeneous freezing are strongly dependent on cooling rates, with gravity waves dominating upper tropospheric cooling rates; (2) rapid cooling driven by high-frequency waves are likely responsible for the rare occurrences of very high ice concentrations in cirrus; (3) sedimentation and entrainment tend to decrease ice concentrations as cirrus age; and (4) in some situations, changes in temperature tendency driven by high-frequency waves can quench ice nucleation events and limit ice concentrations. Here we use parcel-model simulations of ice nucleation driven by long-duration, constant-pressure balloon temperature time series, along with an extensive dataset of cold cirrus microphysical properties from the recent ATTREX high-altitude aircraft campaign, to statistically examine the importance of high-frequency waves as well as the consistency between our theoretical understanding of ice nucleation and observed ice concentrations. The parcel-model simulations indicate common occurrence of peak ice concentrations exceeding several hundred per liter. Sedimentation and entrainment would reduce ice concentrations as clouds age, but 1-D simulations using a wave parameterization (which underestimates rapid cooling events) still produce ice concentrations higher than indicated by observations. We find that quenching of nucleation events by high-frequency waves occurs infrequently and does not prevent occurrences of large ice concentrations in parcel simulations of homogeneous freezing. In fact, the high-frequency variability in the balloon temperature data is entirely responsible for production of these high ice concentrations in the simulations.

Folding of human telomerase RNA pseudoknot using ion-jump and temperature-quench simulations.

PubMed

Biyun, Shi; Cho, Samuel S; Thirumalai, D

2011-12-21

Globally RNA folding occurs in multiple stages involving chain compaction and subsequent rearrangement by a number of parallel routes to the folded state. However, the sequence-dependent details of the folding pathways and the link between collapse and folding are poorly understood. To obtain a comprehensive picture of the thermodynamics and folding kinetics we used molecular simulations of coarse-grained model of a pseudoknot found in the conserved core domain of the human telomerase (hTR) by varying both temperature (T) and ion concentration (C). The phase diagram in the [T,C] plane shows that the boundary separating the folded and unfolded state for the finite 47-nucleotide system is relatively sharp, implying that from a thermodynamic perspective hTR behaves as an apparent two-state system. However, the folding kinetics following single C-jump or T-quench is complicated, involving multiple channels to the native state. Although globally folding kinetics triggered by T-quench and C-jump are similar, the kinetics of chain compaction are vastly different, which reflects the role of initial conditions in directing folding and collapse. Remarkably, even after substantial reduction in the overall size of hTR, the ensemble of compact conformations are far from being nativelike, suggesting that the search for the folded state occurs among the ensemble of low-energy fluidlike globules. The rate of unfolding, which occurs in a single step, is faster upon C-decrease compared to a jump in temperature. To identify "hidden" states that are visited during the folding process we performed simulations by periodically interrupting the approach to the folded state by lowering C. These simulations show that hTR reaches the folded state through a small number of connected clusters that are repeatedly visited during the pulse sequence in which the folding or unfolding is interrupted. The results from interrupted folding simulations, which are in accord with non-equilibrium single-molecule folding of a large ribozyme, show that multiple probes are needed to reveal the invisible states that are sampled by RNA as it folds. Although we have illustrated the complexity of RNA folding using hTR as a case study, general arguments and qualitative comparisons to time-resolved scattering experiments on Azoarcus group I ribozyme and single-molecule non-equilibrium periodic ion-jump experiments establish the generality of our findings. © 2011 American Chemical Society

Green Synthesis of Red-Emitting Carbon Nanodots as a Novel "Turn-on" Nanothermometer in Living Cells.

PubMed

Wang, Chuanxi; Jiang, Kaili; Wu, Qian; Wu, Jiapeng; Zhang, Chi

2016-10-04

Temperature measurements in biology and medical diagnostics, along with sensitive temperature probing of living cells, is of great importance; however, it still faces significant challenges. Herein, a novel "turn-on" carbon-dot-based fluorescent nanothermometry device for spatially resolved temperature measurements in living cells is presented. The carbon nanodots (CNDs) are prepared by a green microwave-assisted method and exhibit red fluorescence (λem =615 nm) with high quantum yields (15 %). Then, an on-off fluorescent probe is prepared for detecting glutathione (GSH) based on aggregation-induced fluorescence quenching. Interestingly, the quenched fluorescence could be recovered by increasing temperature and the CNDs-GSH mixture could behave as an off-on fluorescent probe for temperature. Thus, red-emitting CNDs can be utilized for "turn-on" fluorescent nanothermometry through the fluorescence quenching and recovery processes, respectively. We employ MC3T3-E1 cells as an example model to demonstrate the red-emitting CNDs can function as "non-contact" tools for the accurate measurement of temperature and its gradient inside a living cell. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Twisting Anderson pseudospins with light: Quench dynamics in THz-pumped BCS superconductors

NASA Astrophysics Data System (ADS)

Chou, Yang-Zhi; Liao, Yunxiang; Foster, Matthew

We study the preparation and the detection of coherent far-from-equilibrium BCS superconductor dynamics in THz pump-probe experiments. In a recent experiment, an intense monocycle THz pulse with center frequency ω = Δ was injected into a superconductor with BCS gap Δ the post-pump evolution was detected via the optical conductivity. It was argued that nonlinear coupling of the pump to the Anderson pseudospins of the superconductor induces coherent dynamics of the Higgs mode Δ (t) . We validate this picture in a 2D BCS model with a combination of exact numerics and the Lax reduction, and we compute the dynamical phase diagram. The main effect of the pump is to scramble the orientations of Anderson pseudospins along the Fermi surface by twisting them in the xy-plane. We show that more intense pulses can induce a far-from-equilibrium gapless phase (phase I), originally predicted in the context of interaction quenches. We show that the THz pump can reach phase I at much lower energy densities than an interaction quench, and we demonstrate that Lax reduction provides a quantitative tool for computing coherent BCS dynamics. We also compute the optical conductivity for the states discussed here.

Anesthetic Binding in a Pentameric Ligand-Gated Ion Channel: GLIC

PubMed Central

Chen, Qiang; Cheng, Mary Hongying; Xu, Yan; Tang, Pei

2010-01-01

Cys-loop receptors are molecular targets of general anesthetics, but the knowledge of anesthetic binding to these proteins remains limited. Here we investigate anesthetic binding to the bacterial Gloeobacter violaceus pentameric ligand-gated ion channel (GLIC), a structural homolog of cys-loop receptors, using an experimental and computational hybrid approach. Tryptophan fluorescence quenching experiments showed halothane and thiopental binding at three tryptophan-associated sites in the extracellular (EC) domain, transmembrane (TM) domain, and EC-TM interface of GLIC. An additional binding site at the EC-TM interface was predicted by docking analysis and validated by quenching experiments on the N200W GLIC mutant. The binding affinities (KD) of 2.3 ± 0.1 mM and 0.10 ± 0.01 mM were derived from the fluorescence quenching data of halothane and thiopental, respectively. Docking these anesthetics to the original GLIC crystal structure and the structures relaxed by molecular dynamics simulations revealed intrasubunit sites for most halothane binding and intersubunit sites for thiopental binding. Tryptophans were within reach of both intra- and intersubunit binding sites. Multiple molecular dynamics simulations on GLIC in the presence of halothane at different sites suggested that anesthetic binding at the EC-TM interface disrupted the critical interactions for channel gating, altered motion of the TM23 linker, and destabilized the open-channel conformation that can lead to inhibition of GLIC channel current. The study has not only provided insights into anesthetic binding in GLIC, but also demonstrated a successful fusion of experiments and computations for understanding anesthetic actions in complex proteins. PMID:20858424

Caught in the Act: Gas and Stellar Velocity Dispersions in a Fast Quenching Compact Star-Forming Galaxy at z~1.7

NASA Astrophysics Data System (ADS)

Barro, Guillermo; Faber, Sandra M.; Dekel, Avishai; Pacifici, Camilla; Pérez-González, Pablo G.; Toloba, Elisa; Koo, David C.; Trump, Jonathan R.; Inoue, Shigeki; Guo, Yicheng; Liu, Fengshan; Primack, Joel R.; Koekemoer, Anton M.; Brammer, Gabriel; Cava, Antonio; Cardiel, Nicolas; Ceverino, Daniel; Eliche, Carmen; Fang, Jerome J.; Finkelstein, Steven L.; Kocevski, Dale D.; Livermore, Rachael C.; McGrath, Elizabeth

2016-04-01

We present Keck I MOSFIRE spectroscopy in the Y and H bands of GDN-8231, a massive, compact, star-forming galaxy at a redshift of z ˜ 1.7. Its spectrum reveals both Hα and [N II] emission lines and strong Balmer absorption lines. The Hα and Spitzer MIPS 24 μm fluxes are both weak, thus indicating a low star-formation rate of SFR ≲ 5{--}10 {M}⊙ yr-1. This, added to a relatively young age of ˜700 Myr measured from the absorption lines, provides the first direct evidence for a distant galaxy being caught in the act of rapidly shutting down its star formation. Such quenching allows GDN-8231 to become a compact, quiescent galaxy, similar to three other galaxies in our sample, by z ˜ 1.5. Moreover, the color profile of GDN-8231 shows a bluer center, consistent with the predictions of recent simulations for an early phase of inside-out quenching. Its line-of-sight velocity dispersion for the gas, {σ }{{{LOS}}}{{gas}} = 127 ± 32 km s-1, is nearly 40% smaller than that of its stars, {σ }{{{LOS}}}\\star = 215 ± 35 km s-1. High-resolution hydro-simulations of galaxies explain such apparently colder gas kinematics of up to a factor of ˜1.5 with rotating disks being viewed at different inclinations and/or centrally concentrated star-forming regions. A clear prediction is that their compact, quiescent descendants preserve some remnant rotation from their star-forming progenitors.

Survival and in-vessel redistribution of beryllium droplets after ITER disruptions

NASA Astrophysics Data System (ADS)

Vignitchouk, L.; Ratynskaia, S.; Tolias, P.; Pitts, R. A.; De Temmerman, G.; Lehnen, M.; Kiramov, D.

2018-07-01

The motion and temperature evolution of beryllium droplets produced by first wall surface melting after ITER major disruptions and vertical displacement events mitigated during the current quench are simulated by the MIGRAINe dust dynamics code. These simulations employ an updated physical model which addresses droplet-plasma interaction in ITER-relevant regimes characterized by magnetized electron collection and thin-sheath ion collection, as well as electron emission processes induced by electron and high-Z ion impacts. The disruption scenarios have been implemented from DINA simulations of the time-evolving plasma parameters, while the droplet injection points are set to the first-wall locations expected to receive the highest thermal quench heat flux according to field line tracing studies. The droplet size, speed and ejection angle are varied within the range of currently available experimental and theoretical constraints, and the final quantities of interest are obtained by weighting single-trajectory output with different size and speed distributions. Detailed estimates of droplet solidification into dust grains and their subsequent deposition in the vessel are obtained. For representative distributions of the droplet injection parameters, the results indicate that at most a few percents of the beryllium mass initially injected is converted into solid dust, while the remaining mass either vaporizes or forms liquid splashes on the wall. Simulated in-vessel spatial distributions are also provided for the surviving dust, with the aim of providing guidance for planned dust diagnostic, retrieval and clean-up systems on ITER.

PEGylated Liposomes as Carriers of Hydrophobic Porphyrins.

PubMed

Dzieciuch, Monika; Rissanen, Sami; Szydłowska, Natalia; Bunker, Alex; Kumorek, Marta; Jamróz, Dorota; Vattulainen, Ilpo; Nowakowska, Maria; Róg, Tomasz; Kepczynski, Mariusz

2015-06-04

Sterically stabilized liposomes (SSLs) (PEGylated liposomes) are applied as effective drug delivery vehicles. Understanding the interactions between hydrophobic compounds and PEGylated membranes is therefore important to determine the effectiveness of PEGylated liposomes for delivery of drugs or other bioactive substances. In this study, we have combined fluorescence quenching analysis (FQA) experiments and all-atom molecular dynamics (MD) simulations to study the effect of membrane PEGylation on the location and orientation of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (p-THPP) that has been used in our study as a model hydrophobic compound. First, we consider the properties of p-THPP in the presence of different fluid phosphatidylcholine bilayers that we use as model systems for protein-free cell membranes. Next, we studied the interaction between PEGylated membranes and p-THPP. Our MD simulation results indicated that the arrangement of p-THPP within zwitterionic membranes is dependent on their free volume, and p-THPP solubilized in PEGylated liposomes is localized in two preferred positions: deep within the membrane (close to the center of the bilayer) and in the outer PEG corona (p-THPP molecules being wrapped with the polymer chains). Fluorescence quenching methods confirmed the results of atomistic MD simulations and showed two populations of p-THPP molecules as in MD simulations. Our results provide both an explanation for the experimental observation that PEGylation improves the drug-loading efficiency of membranes and also a more detailed molecular-level description of the interactions between porphyrins and lipid membranes.

Search for the pentaquark resonance signature in lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

B. G. Lasscock; J. Hedditch; Derek Leinweber

2005-02-01

Claims concerning the possible discovery of the {Theta}{sup +} pentaquark, with minimal quark content uudd{bar s}, have motivated our comprehensive study into possible pentaquark states using lattice QCD. We review various pentaquark interpolating fields in the literature and create a new candidate ideal for lattice QCD simulations. Using these interpolating fields we attempt to isolate a signal for a five-quark resonance. Calculations are performed using improved actions on a large 20{sup 3} x 40 lattice in the quenched approximation. The standard lattice resonance signal of increasing attraction between baryon constituents for increasing quark mass is not observed for spin-1/2 pentaquarkmore » states. We conclude that evidence supporting the existence of a spin-1/2 pentaquark resonance does not exist in quenched QCD.« less

Cluster-Glass Phase in Pyrochlore X Y Antiferromagnets with Quenched Disorder

NASA Astrophysics Data System (ADS)

Andrade, Eric C.; Hoyos, José A.; Rachel, Stephan; Vojta, Matthias

2018-03-01

We study the impact of quenched disorder (random exchange couplings or site dilution) on easy-plane pyrochlore antiferromagnets. In the clean system, order by disorder selects a magnetically ordered state from a classically degenerate manifold. In the presence of randomness, however, different orders can be chosen locally depending on details of the disorder configuration. Using a combination of analytical considerations and classical Monte Carlo simulations, we argue that any long-range-ordered magnetic state is destroyed beyond a critical level of randomness where the system breaks into magnetic domains due to random exchange anisotropies, becoming, therefore, a glass of spin clusters, in accordance with the available experimental data. These random anisotropies originate from off-diagonal exchange couplings in the microscopic Hamiltonian, establishing their relevance to other magnets with strong spin-orbit coupling.

Particle connectedness and cluster formation in sequential depositions of particles: integral-equation theory.

PubMed

Danwanichakul, Panu; Glandt, Eduardo D

2004-11-15

We applied the integral-equation theory to the connectedness problem. The method originally applied to the study of continuum percolation in various equilibrium systems was modified for our sequential quenching model, a particular limit of an irreversible adsorption. The development of the theory based on the (quenched-annealed) binary-mixture approximation includes the Ornstein-Zernike equation, the Percus-Yevick closure, and an additional term involving the three-body connectedness function. This function is simplified by introducing a Kirkwood-like superposition approximation. We studied the three-dimensional (3D) system of randomly placed spheres and 2D systems of square-well particles, both with a narrow and with a wide well. The results from our integral-equation theory are in good accordance with simulation results within a certain range of densities.

Particle connectedness and cluster formation in sequential depositions of particles: Integral-equation theory

NASA Astrophysics Data System (ADS)

Danwanichakul, Panu; Glandt, Eduardo D.

2004-11-01

We applied the integral-equation theory to the connectedness problem. The method originally applied to the study of continuum percolation in various equilibrium systems was modified for our sequential quenching model, a particular limit of an irreversible adsorption. The development of the theory based on the (quenched-annealed) binary-mixture approximation includes the Ornstein-Zernike equation, the Percus-Yevick closure, and an additional term involving the three-body connectedness function. This function is simplified by introducing a Kirkwood-like superposition approximation. We studied the three-dimensional (3D) system of randomly placed spheres and 2D systems of square-well particles, both with a narrow and with a wide well. The results from our integral-equation theory are in good accordance with simulation results within a certain range of densities.

Investigation on the pH-dependent binding of benzocaine and lysozyme by fluorescence and absorbance

NASA Astrophysics Data System (ADS)

Li, Shihui; Li, Daojin

2011-11-01

The interaction mechanism between benzocaine (BZC) and lysozyme (Lys) has been investigated by fluorescence, synchronous fluorescence, ultraviolet-vis (UV) absorption spectra, and three-dimensional fluorescence (3-D) in various pH medium. The observations of fluorescence spectra were mainly rationalized in terms of a static quenching process at lower concentration of BZC ( CBZC/ CLys < 9) and a combined quenching process at higher concentration of BZC ( CBZC/ CLys > 9) at pH 7.4 and 8.4. However, the fluorescence quenching was mainly arisen from static quenching by complex formation in all studied drug concentrations at pH 3.5. The structural characteristics of BZC and Lys were probed, and their binding affinities were determined under different pH conditions (pH 3.5, 7.4, and 8.4). The results indicated that the binding abilities of BZC to Lys decreased at the pH below and above the simulative physiological condition (pH 7.4) due to the alterations of the protein secondary and tertiary structures or the structural change of BZC. The effect of BZC on the conformation of Lys was analyzed using UV, synchronous fluorescence and three-dimensional fluorescence under different pH conditions. These results indicate that the binding of BZC to Lys causes apparent change in the secondary and tertiary structures of Lys. The effect of Zn 2+ on the binding constant of BZC with Lys under various pH conditions (pH 3.5, 7.4, and 8.4) was also studied.

Co2(nu2)-o Quenching Rate Coefficient Derived from Coincidental SABER-TIMED and Fort Collins Lidar Observations of the Mesosphere and Lower Thermosphere

NASA Technical Reports Server (NTRS)

Feofilov, A. G.; Kutepov, A. A.; She, C.-Y.; Smith, A. K.; Pesnell, W. D.; Goldberg, R. A.

2012-01-01

Among the processes governing the energy balance in the mesosphere and lower thermosphere (MLT), the quenching of CO2(nu2) vibrational levels by collisions with O atoms plays an important role. However, there is a factor of 3-4 discrepancy between the laboratory measurements of the CO2-O quenching rate coefficient, k(sub VT),and its value estimated from the atmospheric observations. In this study, we retrieve k(sub VT) in the altitude region85-105 km from the coincident SABER/TIMED and Fort Collins sodium lidar observations by minimizing the difference between measured and simulated broadband limb 15 micron radiation. The averaged k(sub VT) value obtained in this work is 6.5 +/- 1.5 X 10(exp -12) cubic cm/s that is close to other estimates of this coefficient from the atmospheric observations.However, the retrieved k(sub VT) also shows altitude dependence and varies from 5.5 1 +/-1 10(exp -12) cubic cm/s at 90 km to 7.9 +/- 1.2 10(exp -12) cubic cm/s at 105 km. Obtained results demonstrate the deficiency in current non-LTE modeling of the atmospheric 15 micron radiation, based on the application of the CO2-O quenching and excitation rates, which are linked by the detailed balance relation. We discuss the possible model improvements, among them accounting for the interaction of the non-thermal oxygen atoms with CO2 molecules.

First principles simulation of amorphous InSb

NASA Astrophysics Data System (ADS)

Los, Jan H.; Kühne, Thomas D.; Gabardi, Silvia; Bernasconi, Marco

2013-05-01

Ab initio molecular dynamics simulations based on density functional theory have been performed to generate a model of amorphous InSb by quenching from the melt. The resulting network is mostly tetrahedral with a minor fraction (10%) of atoms in a fivefold coordination. The structural properties are in good agreement with available x-ray diffraction and extended x-ray-absorption fine structure data and confirm the proposed presence of a sizable fraction of homopolar In-In and Sb-Sb bonds whose concentration in our model amounts to about 20% of the total number of bonds.

28th Lanchester Memorial Lecture - Experimental real-gas hypersonics

NASA Astrophysics Data System (ADS)

Hornung, H. G.

1988-12-01

It is possible to simulate a number of dissociative real-gas effects in the laboratory by means quite different from those of the perfect-gas Mach-Reynolds simulation, as presently demonstrated for two sets of results obtained in a free-piston shock tunnel experimental facility designed and built for this purpose. The results concern blunt body flows, which involve the phenomenon of dissociation quenching, and shock detachment from a wedge, which revealed a novel effect of reacting flows in which a thin subsonic layer exists after the shock, followed by a supersonic flow.

Friction stir processing on carbon steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarasov, Sergei Yu., E-mail: tsy@ispms.ru; Melnikov, Alexander G., E-mail: melnikov-ag@tpu.ru; Rubtsov, Valery E., E-mail: rvy@ispms.ru

2014-11-14

Friction stir processing of medium carbon steel samples has been carried out using a milling machine and tools made of cemented tungsten carbide. Samples have been machined from 40 and 40X steels. The tools have been made in the shape of 5×5×1.5 mm and 3×3×1.5 mm tetrahedrons. The microstructure of stirred zone has been obtained using the smaller tool and consists of fine recrystallized 2-3 μm grains, whereas the larger tool has produced the 'onion-like' structures comprising hard quenched 'white' 500-600 MPa layers with 300-350 MPa interlayers of bainite needles. The mean values of wear intensity obtained after measuring themore » wear scar width were 0.02 mm/m and 0.001 mm/m for non-processed and processed samples, respectively.« less

Dynamical phase transitions in generalized Kuramoto model with distributed Sakaguchi phase

NASA Astrophysics Data System (ADS)

Banerjee, Amitava

2017-11-01

In this numerical work, we have systematically studied the dynamical phase transitions in the Kuramoto-Sakaguchi model of synchronizing phase oscillators controlled by disorder in the Sakaguchi phases. We derive the numerical steady state phase diagrams for quenched and annealed kinds of disorder in the Sakaguchi parameters, using the conventional order parameter and other such statistical quantities as strength of incoherence and discontinuity measures. We have also considered the correlation profile of the local order parameter fluctuations in the various phases identified. The phase diagrams for quenched disorder are qualitatively much different from those in the global coupling regime. The order of various transitions is confirmed by a study of the distribution of the order parameter and its fourth order Binder’s cumulant across the transition for an ensemble of initial distribution of phases. For the annealed type of disorder, in contrast to the case with quenched disorder, the system is almost insensitive to the amount of disorder. We also elucidate the role of chimeralike states in the synchronizing transition of the system, and study the effect of disorder on these states. Finally, we seek justification of our results from simulations guided by the Ott-Antonsen ansatz.

Study of Effect of Quenching Deformation Influenced by 17CrNiMo6 Gear Shaft of Carburization

NASA Astrophysics Data System (ADS)

Pang, Zirui; Yu, Shenjun; Xu, Jinwu

The 17CrNiMo6 steel is mainly used for the gear shaft of large modulus in many fields of heavy industry such as mining, transit, hoist, forging and so on[1]. The size of addendum circle and common normal line is changed a lot beyond the tolerance because of the long time of carburizing process and the out-of-step structural stress and thermal stress during the quenching process. And thus the posterior grinding efficiency and quality are influenced. In the paper comparison and analysis of the deformation affected by solid and hollow gear shafts were done and the methods of simulation and practice were both used. The results are as follows: the deformation of gear shaft was small before and after carburizing while that of gear shaft was large before and after quenching because of different cooling velocity, structure and hardness of each position. And the deformation of hollow was much smaller than that of solid. Therefore, if the hollow gear shaft is used, the waste of material will be decreased, and finishing cost will be reduced, and thus the technology of heat treatment will be optimized.

Feasibility of an advanced thrust termination assembly for a solid propellant rocket motor

NASA Technical Reports Server (NTRS)

1975-01-01

A total of 68 quench tests were conducted in a vented bomb assembly (VBA). Designed to simulate full-scale motor operating conditions, this laboratory apparatus uses a 2-inch-diameter, end-burning propellant charge and an insulated disc of consolidated hydrated aluminum sulfate along with the explosive charge necessary to disperse the salt and inject it onto the burning surface. The VBA was constructed to permit variation of motor design parameters of interest; i.e., weight of salt per unit burning surface area, weight of explosive per unit weight of salt, distance from salt surface to burning surface, incidence angle of salt injection, chamber pressure, and burn time. Completely satisfactory salt quenching, without re-ignition, occurred in only two VBA tests. These were accomplished with a quench charge ratio (QCR) of 0.023 lb salt per square inch of burning surface at dispersing charge ratios (DCR) of 13 and 28 lb of salt per lb of explosive. Candidate materials for insulating salt charges from the rocket combustion environment were evaluated in firings of 5-inch-diameter, uncured end-burner motors. A pressed, alumina ceramic fiber material was selected for further evaluation and use in the final demonstration motor.

Simulation of a turbulent flame in a channel

NASA Technical Reports Server (NTRS)

Bruneaux, G.; Akselvoll, K.; Poinsot, T.; Ferziger, J. H.

1994-01-01

The interaction between turbulent premixed flames and channel walls is studied. Combustion is represented by a simple irreversible reaction with a large activation temperature. Feedback to the flowfield is suppressed by invoking a constant density assumption. The effect of wall distance on local and global flame structure is investigated. Quenching distances and maximum wall heat fluxes computed in laminar cases are compared to DNS results. It is found that quenching distances decrease and maximum heat fluxes increase relative to laminar flame values. It is shown that these effects are due to large coherent structures which push flame elements towards to wall. The effect of wall strain is studied in flame-wall interaction in a stagnation line flow; this is used to explain the DNS results. It is also shown that 'remarkable' flame events are produced by interaction with a horseshoe vortex: burnt gases are pushed towards the wall at high speed and induce quenching and high wall heat fluxes while fresh gases are expelled from the wall region and form finger-like structures. Effects of the wall on flame surface density are investigated, and a simple model for flame-wall interaction is proposed; its predictions compare well with the DNS results.

Luminescence concentration quenching and site-occupancy of Eu2+ ions in Na2Ca2Si3O9 phosphors derived from 45S5 glass-ceramics

NASA Astrophysics Data System (ADS)

Zhu, Yangguang; Tong, Chao; Xu, Chuanyan; Li, Yadong; Seo, Hyo Jin

2016-04-01

The phosphors of Na2Ca2-2xEu2xSi3O9 (x = 0, 0.03, 0.05, 0.07, 0.09) were first synthesized by sol-gel method. The crystal phase formations of the phosphors were detected by X-ray powder diffraction (XRD) measurements and the structure refinement. The photoluminescence spectra, the concentration quenching, the luminescence decay curves and the luminescence color chromaticity were measured, respectively. The excitation spectra indicate that the phosphors can be effectively excited by near UV-LED chips. Two kinds of Eu2+ sites centered at 545 nm and 505 nm were discussed by analyzing the spectra, concentration-dependent luminescence intensity and lifetimes. This is a potential tool for monitoring the bioactivity of 45S5 glass-ceramics in situ.

False HDAC Inhibition by Aurone Compound.

PubMed

Itoh, Yukihiro; Suzuki, Miki; Matsui, Taiji; Ota, Yosuke; Hui, Zi; Tsubaki, Kazunori; Suzuki, Takayoshi

2016-01-01

Fluorescence assays are useful tools for estimating enzymatic activity. Their simplicity and manageability make them suitable for screening enzyme inhibitors in drug discovery studies. However, researchers need to pay attention to compounds that show auto-fluorescence and quench fluorescence, because such compounds lower the accuracy of the fluorescence assay systems by producing false-positive or negative results. In this study, we found that aurone compound 7, which has been reported as a histone deacetylase (HDAC) inhibitor, gave false-positive results. Although compound 7 was identified by an in vitro HDAC fluorescence assay, it did not show HDAC inhibitory activity in a cell-based assay, leading us to suspect its in vitro HDAC inhibitory activity. As a result of verification experiments, we found that compound 7 interferes with the HDAC fluorescence assay by quenching the HDAC fluorescence signal. Our findings underscore the faults of fluorescence assays and call attention to careless interpretation.

Low level chemiluminescence from liquid culture media.

PubMed

Vogel, R; Süssmuth, R

1999-06-01

Low level chemiluminescence (CL) can be observed from autoclaved liquid culture media, as used in microbiology. The light emission is oxygen-dependent and arises from reactions following auto-oxidation of reducing Maillard products which are formed during autoclaving. The inhibition of this CL by radical scavengers and antioxidants has been studied. As superoxide radicals and hydrogen peroxide are predominantly involved in the initiation of the CL, the investigation of CL from culture media offers a convenient tool for the detection of exogenous (medium-mediated) oxidative stress being imposed onto micro-organisms in culture. Transition metal ions showed, dependent on concentration, both inhibitory and stimulating effects on the CL, which was also affected by the presence of complexing agents. Iron porphyrins and related complexes displayed a very efficient quenching of the CL, which may be of particular importance, as aerobic micro-organisms have been previously shown to be very efficient in quenching the CL from culture media.

Chemical reactivation of resin-embedded pHuji adds red for simultaneous two-color imaging with EGFP

PubMed Central

Guo, Wenyan; Liu, Xiuli; Liu, Yurong; Gang, Yadong; He, Xiaobin; Jia, Yao; Yin, Fangfang; Li, Pei; Huang, Fei; Zhou, Hongfu; Wang, Xiaojun; Gong, Hui; Luo, Qingming; Xu, Fuqiang; Zeng, Shaoqun

2017-01-01

The pH-sensitive fluorescent proteins enabling chemical reactivation in resin are useful tools for fluorescence microimaging. EGFP or EYFP is good for such applications. For simultaneous two-color imaging, a suitable red fluorescent protein is an urgent need. Here a pH-sensitive red fluorescent protein, pHuji, is selected and verified to remain pH-sensitive in HM20 resin. We observe 183% fluorescence intensity of pHuji in resin-embeded mouse brain and 29.08-fold fluorescence intensity of reactivated pHuji compared to the quenched state. pHuji and EGFP can be quenched and chemically reactivated simultaneously in resin, thus enabling simultaneous two-color micro-optical sectioning tomography of resin-embedded mouse brain. This method may greatly facilitate the visualization of neuronal morphology and neural circuits to promote understanding of the structure and function of the brain. PMID:28717566

Chemical reactivation of resin-embedded pHuji adds red for simultaneous two-color imaging with EGFP.

PubMed

Guo, Wenyan; Liu, Xiuli; Liu, Yurong; Gang, Yadong; He, Xiaobin; Jia, Yao; Yin, Fangfang; Li, Pei; Huang, Fei; Zhou, Hongfu; Wang, Xiaojun; Gong, Hui; Luo, Qingming; Xu, Fuqiang; Zeng, Shaoqun

2017-07-01

The pH-sensitive fluorescent proteins enabling chemical reactivation in resin are useful tools for fluorescence microimaging. EGFP or EYFP is good for such applications. For simultaneous two-color imaging, a suitable red fluorescent protein is an urgent need. Here a pH-sensitive red fluorescent protein, pHuji, is selected and verified to remain pH-sensitive in HM20 resin. We observe 183% fluorescence intensity of pHuji in resin-embeded mouse brain and 29.08-fold fluorescence intensity of reactivated pHuji compared to the quenched state. pHuji and EGFP can be quenched and chemically reactivated simultaneously in resin, thus enabling simultaneous two-color micro-optical sectioning tomography of resin-embedded mouse brain. This method may greatly facilitate the visualization of neuronal morphology and neural circuits to promote understanding of the structure and function of the brain.

Synthesis, characterization, crystal structure and HSA binding of two new N,O,O-donor Schiff-base ligands derived from dihydroxybenzaldehyde and tert-butylamine

NASA Astrophysics Data System (ADS)

Khosravi, Iman; Hosseini, Farnaz; Khorshidifard, Mahsa; Sahihi, Mehdi; Rudbari, Hadi Amiri

2016-09-01

Two new o-hydroxy Schiff-bases compounds, L1 and L2, were derived from the 1:1 M condensation of 2,3-dihydroxybenzaldehyde and 2,4-dihydroxybenzaldehyde with tert-butylamine and were characterized by elemental analysis, FT-IR, 1H and 13C NMR spectroscopies. The crystal structure of L2 was also determined by single crystal X-ray analysis. The crystal structure of L2 showed that the compound exists as a zwitterionic form in the solid state, with the H atom of the phenol group being transferred to the imine N atom. It adopts an E configuration about the central Cdbnd N double bond. Furthermore, binding of these Schiff base ligands to Human Serum Albumin (HSA) was investigated by fluorescence quenching, absorption spectroscopy, molecular docking and molecular dynamics (MD) simulation methods. The fluorescence emission of HSA was quenched by ligands. Also, suitable models were used to analyze the UV-vis absorption spectroscopy data for titration of HSA solution by various amounts of Schiff bases. The spectroscopic studies revealed that these Schiff bases formed 1:1 complex with HSA. Energy transfer mechanism of quenching was discussed and the values of 3.35 and 1.57 nm as the mean distances between the bound ligands and the HSA were calculated for L1 and L2, respectively. Molecular docking results indicated that the main active binding site for these Schiff bases ligands is in subdomain IB. Moreover, MD simulation results suggested that this Schiff base complex can interact with HSA, with a slight modification of its tertiary structure.

Conformation-related exciton localization and charge-pair formation in polythiophenes: ensemble and single-molecule study.

PubMed

Sugimoto, Toshikazu; Habuchi, Satoshi; Ogino, Kenji; Vacha, Martin

2009-09-10

We study conformation-dependent photophysical properties of polythiophene (PT) by molecular dynamics simulations and by ensemble and single-molecule optical experiments. We use a graft copolymer consisting of a polythiophene backbone and long polystyrene branches and compare its properties with those obtained on the same polythiophene derivative without the side chains. Coarse-grain molecular dynamics simulations show that in a poor solvent, the PT without the side chains (PT-R) forms a globulelike conformation in which distances between any two conjugated segments on the chain are within the Forster radius for efficient energy transfer. In the PT with the polystyrene branches (PT-PS), the polymer main PT chain retains an extended coillike conformation, even in a poor solvent, and the calculated distances between conjugated segments favor energy transfer only between a few neighboring chromophores. The theoretical predictions are confirmed by measurements of fluorescence anisotropy and fluorescence blinking of the polymers' single chains. High anisotropy ratios and two-state blinking in PT-R are due to localization of the exciton on a single conjugated segment. These signatures of exciton localization are absent in single chains of PT-PS. Electric-field-induced quenching measured as a function of concentration of PT dispersed in an inert matrix showed that in well-isolated chains of PT-PS, the exciton dissociation is an intrachain process and that aggregation of the PT-R chains causes an increase in quenching due to the onset of interchain interactions. Measurements of the field-induced quenching on single chains indicate that in PT-R, the exciton dissociation is a slower process that takes place only after the exciton is localized on one conjugated segment.

Quenching behavior of molten pool with different strategies – A review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shrikant,, E-mail: 2014rmt9018@mnit.ac.in; Pandel, U.; Duchaniya, R. K.

After the major severe accident in nuclear reactor, there has been lot of concerns regarding long term core melt stabilization following a severe accident in nuclear reactors. Numerous strategies have been though for quenching and stabilization of core melt like top flooding, bottom flooding, indirect cooling, etc. However, the effectiveness of these schemes is yet to be determined properly, for which, lot of experiments are needed. Several experiments have been performed for coolability of melt pool under bottom flooding as well as for indirect cooling. Besides these tests are very scattered because they involve different simulants material initial temperatures andmore » masses of melt, which makes it very complex to judge the effectiveness of a particular technique and advantage over the other. In this review paper, a study has been carried on different cooling techniques of simulant materials with same mass. Three techniques have been compared here and the results are discussed. Under top flooding technique it took several hours to cool the melt under without decay heat condition. In bottom flooding technique was found to be the best technique among in indirect cooling technique, top flooded technique, and bottom flooded technique.« less

Finite-beta and equilibrium sheared flow effects on core plasma turbulence and transport

NASA Astrophysics Data System (ADS)

Chen, Yang; Parker, Scott E.

2004-11-01

Recent GEM (Y. Chen and S. E. Parker, J. Comp. Phys. 189 (2003)463) simulations have revealed the following features of ITG turbulence and transport: (1) For η_e ˜η_i, as β increases the turbulence level and transport increase, leading to fast streamer transport for β ˜ β_crit/2, β_ crit the ideal ballooning limit; (2) Sheared E_r× B flow with shearing rate γ_E=(r/q)partial(qv_ E× B/r)/partial r ˜ γ readily stabilizes the linear eigenmode. However, starting with a nonlinear state obtained without sheared flow, and continue the simulation with a shearing rate γE ≤ 3γ, the turbulence and transport are reduced but not completely quenched, indicating that turbulence is nonlinearly self-sustained.(J. F. Drake, A. Zeiler and D. Biskamp, Phys. Rev. Lett 75 (1995) 4222) At β=0.4β_crit, turbulence is completely quenched only when the shearing rate far exceeds the linear growth rate; (3) As β increases, the shearing rate threshold at which the turbulence can self-sustain increases. Electromagnetic turbulence is more robust in the presence of sheared flow than electrostatic turbulence.

Reduction of asymmetric wall force in ITER disruptions with fast current quench

NASA Astrophysics Data System (ADS)

Strauss, H.

2018-02-01

One of the problems caused by disruptions in tokamaks is the asymmetric electromechanical force produced in conducting structures surrounding the plasma. The asymmetric wall force in ITER asymmetric vertical displacement event (AVDE) disruptions is calculated in nonlinear 3D MHD simulations. It is found that the wall force can vary by almost an order of magnitude, depending on the ratio of the current quench time to the resistive wall magnetic penetration time. In ITER, this ratio is relatively low, resulting in a low asymmetric wall force. In JET, this ratio is relatively high, resulting in a high asymmetric wall force. Previous extrapolations based on JET measurements have greatly overestimated the ITER wall force. It is shown that there are two limiting regimes of AVDEs, and it is explained why the asymmetric wall force is different in the two limits.

Microstructure, soft magnetic properties and applications of amorphous Fe-Co-Si-B-Mo-P alloy

NASA Astrophysics Data System (ADS)

Hasiak, Mariusz; Miglierini, Marcel; Łukiewski, Mirosław; Łaszcz, Amadeusz; Bujdoš, Marek

2018-05-01

DC thermomagnetic properties of Fe51Co12Si16B8Mo5P8 amorphous alloy in the as-quenched and after annealing below crystallization temperature are investigated. They are related to deviations in the microstructure as revealed by Mössbauer spectrometry. Study of AC magnetic properties, i.e. hysteresis loops, relative permeability and core losses versus maximum induction was aimed at obtaining optimal initial parameters for simulation process of a resonant transformer for a rail power supply converter. The results obtained from numerical analyses including core losses, winding losses, core mass, and dimensions were compared with the same parameters calculated for Fe-Si alloy and ferrite. Moreover, Steinmetz coefficients were also calculated for the as-quenched Fe51Co12Si16B8Mo5P8 amorphous alloy.

Properties of tetrahedral clusters and medium range order in GaN during rapid solidification

NASA Astrophysics Data System (ADS)

Gao, Tinghong; Li, Yidan; Yao, Zhenzhen; Hu, Xuechen; Xie, Quan

2017-12-01

The solidification process of liquid gallium nitride has been studied by molecular dynamics simulation using the Stillinger-Weber potential at cooling rate of 10 K/ps. The structural properties of gallium nitride during the rapid cooling process were investigated in detail by the radial distribution functions, Voronoi polyhedron index and the visualization technology. The amorphous structures were formed with many medium range order structures at 200 K. The <4 0 0 0> polyhedron as the main polyhedron was more stable than other polyhedron in GaN during the quenching process. The cubic and hexahedral medium range order structures were formed by the close link between <4 0 0 0> polyhedron. The cubic crystal structures grew up through the crystalline surface by a layer-by-layer method to become more stable structures during the quenching process.

Autocorrelation exponent of conserved spin systems in the scaling regime following a critical quench.

PubMed

Sire, Clément

2004-09-24

We study the autocorrelation function of a conserved spin system following a quench at the critical temperature. Defining the correlation length L(t) approximately t(1/z), we find that for times t' and t satisfying L(t')infinity limit, we show that lambda(')(c)=d+2 and phi=z/2. We give a heuristic argument suggesting that this result is, in fact, valid for any dimension d and spin vector dimension n. We present numerical simulations for the conserved Ising model in d=1 and d=2, which are fully consistent with the present theory.

Progress on Complex Langevin simulations of a finite density matrix model for QCD

NASA Astrophysics Data System (ADS)

Bloch, Jacques; Glesaaen, Jonas; Verbaarschot, Jacobus; Zafeiropoulos, Savvas

2018-03-01

We study the Stephanov model, which is an RMT model for QCD at finite density, using the Complex Langevin algorithm. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory rather than to intended theory with dynamical quarks. A detailed analysis of this issue and a potential resolution of the failure of this algorithm are discussed. We study the effect of gauge cooling on the Dirac eigenvalue distribution and time evolution of the norm for various cooling norms, which were specifically designed to remove the pathologies of the complex Langevin evolution. The cooling is further supplemented with a shifted representation for the random matrices. Unfortunately, none of these modifications generate a substantial improvement on the complex Langevin evolution and the final results still do not agree with the analytical predictions.

Rapid-quench axially staged combustor

DOEpatents

Feitelberg, Alan S.; Schmidt, Mark Christopher; Goebel, Steven George

1999-01-01

A combustor cooperating with a compressor in driving a gas turbine includes a cylindrical outer combustor casing. A combustion liner, having an upstream rich section, a quench section and a downstream lean section, is disposed within the outer combustor casing defining a combustion chamber having at least a core quench region and an outer quench region. A first plurality of quench holes are disposed within the liner at the quench section having a first diameter to provide cooling jet penetration to the core region of the quench section of the combustion chamber. A second plurality of quench holes are disposed within the liner at the quench section having a second diameter to provide cooling jet penetration to the outer region of the quench section of the combustion chamber. In an alternative embodiment, the combustion chamber quench section further includes at least one middle region and at least a third plurality of quench holes disposed within the liner at the quench section having a third diameter to provide cooling jet penetration to at least one middle region of the quench section of the combustion chamber.

Interactions between natural organic ligands and trace metals studied by fluorescence lifetime and fluorescence quenching

NASA Astrophysics Data System (ADS)

Nouhi, Ayoub; Hajjoul, Houssam; Redon, Roland; Gagné, Jean-Pierre; Mounier, Stéphane

2017-04-01

Improved insight on the interactions between natural organic ligands and trace metals is of paramount importance for better understanding transport and toxicity pathways of metal ions in the environment. Fluorescence spectroscopy allows introspecting ligands-metals interactions. Time-resolved laser fluorescence spectroscopy (TRLFS) measures fluorophore lifetime probing the local molecular environment. Excitation Emission Fluorescence Matrices (EEFMs) and their statistical treatment : parallel factor analysis (PARAFAC) using PROGMEEF Matlab homemade program, can give insight on the number or nature of organic fluorophores involved in the interactions. Quenching of fluorescence by metals can occur following two processes: dynamic and static quenching (Lakowicz, 2013). In the first case, quenching is caused by physical collisions among molecules and in the second case fluorophores can form nonfluorescent complexes with quenchers. It is possible to identify the different mechanisms because each type of quenching corresponds to a different mathematical model (Lakowicz, 2013; Valeur and Berberan-Santos, 2012). In TRLFS, the study of fluorescence decay's laws induced by nanosecond pulsed laser will allow to exactly qualify the type of interaction. The crucial point of the temporal deconvolution will be the evaluation of the best fitting between the different physical models and the decays measured. From the most suitable time decay model, it will be possible to deduce the quenching which modifies the fluorescence. The aim of this study was to characterize interactions between natural organic ligands and trace metals using fluorescence tools to evaluate the fluorescence lifetime of the fluorophore, the occurrence of quenching in presence of metal, discuss its mechanism and estimate conditional stability constants if a complex organic ligand-metal is formed. This study has been done in two steps. First, we have examined the interactions between salicylic acid and copper in order to calibrate our assays and compare our results with literature. Several studies have shown that static quenching occurs in that case (Brun and Schröder, 1975; Lavrik and Mulloev, 2010; Ventry et al., 1991; Babko, 1968). Indeed, after processing the EEFMs and TRLFS data, we found a fluorescence intensity decay by about 50% and a constant lifetime for the fluorophore suggesting a static quenching, in agreement with the literature. In the second step, we have studied the interactions between metal and different types of natural organic matters. In this case, EEMFs and TRLFS experiments were done on samples prepared by dissolving copper in four different fractions of organic matter extracted from estuarine water (St. Lawrence Estuary, Canada). Organic matter was obtained using DAX-8 and XAD-4 resins in series. Humic and fulvic acids are obtained following the IHSS protocol. The results of interaction between humic substances and copper gathered after processing data on PROGMEEF have shown a fluorescence intensity decay by about 57% for the first component and 88% for the second component. The fluorescence lifetime for both components were close to 2 ns and 6 ns respectively and the pH range was stable and close to 6. This means that a static quenching takes place in this case in agreement with the literature. Our study also focused on the investigation of complexation of organic matter by other metals in particular Aluminum, Arsenic, Europium and Uranium.

Synthetic Unruh effect in cold atoms

NASA Astrophysics Data System (ADS)

Rodríguez-Laguna, Javier; Tarruell, Leticia; Lewenstein, Maciej; Celi, Alessio

2017-01-01

We propose to simulate a Dirac field near an event horizon using ultracold atoms in an optical lattice. Such a quantum simulator allows for the observation of the celebrated Unruh effect. Our proposal involves three stages: (1) preparation of the ground state of a massless two-dimensional Dirac field in Minkowski space-time; (2) quench of the optical lattice setup to simulate how an accelerated observer would view that state; (3) measurement of the local quantum fluctuation spectra by one-particle excitation spectroscopy in order to simulate a De Witt detector. According to Unruh's prediction, fluctuations measured in such a way must be thermal. Moreover, following Takagi's inversion theorem, they will obey the Bose-Einstein distribution, which will smoothly transform into the Fermi-Dirac as one of the dimensions of the lattice is reduced.

Survivability and Abiotic Reactions of Selected Amino Acids in Different Hydrothermal System Simulators

NASA Astrophysics Data System (ADS)

Chandru, Kuhan; Imai, Eiichi; Kaneko, Takeo; Obayashi, Yumiko; Kobayashi, Kensei

2013-04-01

We tested the stability and reaction of several amino acids using hydrothermal system simulators: an autoclave and two kinds of flow reactors at 200-250 °C. This study generally showed that there is a variation in the individual amino acids survivability in the simulators. This is mainly attributed to the following factors; heat time, cold quenching exposure, metal ions and also silica. We observed that, in a rapid heating flow reactor, high aggregation and/or condensation of amino acids could occur even during a heat exposure of 2 min. We also monitored their stability in a reflow-type of simulator for 120 min at 20 min intervals. The non-hydrolyzed and hydrolyzed samples for this system showed a similar degradation only in the absence of metal ions.

Coarse-grained modelling of triglyceride crystallisation: a molecular insight into tripalmitin tristearin binary mixtures by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Pizzirusso, Antonio; Brasiello, Antonio; De Nicola, Antonio; Marangoni, Alejandro G.; Milano, Giuseppe

2015-12-01

The first simulation study of the crystallisation of a binary mixture of triglycerides using molecular dynamics simulations is reported. Coarse-grained models of tristearin (SSS) and tripalmitin (PPP) molecules have been considered. The models have been preliminarily tested in the crystallisation of pure SSS and PPP systems. Two different quenching procedures have been tested and their performances have been analysed. The structures obtained from the crystallisation procedures show a high orientation order and a high content of molecules in the tuning fork conformation, comparable with the crystalline α phase. The behaviour of melting temperatures for the α phase of the mixture SSS/PPP obtained from the simulations is in qualitative agreement with the behaviour that was experimentally determined.

Quenching versus quiescence: forming realistic massive ellipticals with a simple starvation model

NASA Astrophysics Data System (ADS)

Gutcke, Thales A.; Macciò, Andrea V.; Dutton, Aaron A.; Stinson, Greg S.

2017-04-01

The decrease in star formation (SF) and the morphological change necessary to produce the z = 0 elliptical galaxy population are commonly ascribed to a sudden quenching event, which is able to rid the central galaxy of its cold gas reservoir in a short time. Following this event, the galaxy is able to prevent further SF and stay quiescent via a maintenance mode. We test whether such a quenching event is truly necessary using a simple model of quiescence. In this model, hot gas (all gas above a temperature threshold) in an ˜1012 M⊙ halo mass galaxy at redshift z ˜ 3 is prevented from cooling. The cool gas continues to form stars at a decreasing rate and the galaxy stellar mass, morphology, velocity dispersion and position on the colour-magnitude diagram (CMD) proceed to evolve. By z = 0, the halo mass has grown to 1013 M⊙ and the galaxy has attained characteristics typical of an observed z = 0 elliptical galaxy. Our model is run in the framework of a cosmological, smooth particle hydrodynamic code that includes SF, early stellar feedback, supernova feedback, metal cooling and metal diffusion. Additionally, we post-process our simulations with a radiative transfer code to create a mock CMD. In contrast to previous assumptions that a pure 'fade away' model evolves too slowly to account for the sparsity of galaxies in the 'green valley', we demonstrate crossing times of ≲1 Gyr. We conclude that no sudden quenching event is necessary to produce such rapid colour transitions.

Investigation on the pH-dependent binding of benzocaine and lysozyme by fluorescence and absorbance.

PubMed

Li, Shihui; Li, Daojin

2011-11-01

The interaction mechanism between benzocaine (BZC) and lysozyme (Lys) has been investigated by fluorescence, synchronous fluorescence, ultraviolet-vis (UV) absorption spectra, and three-dimensional fluorescence (3-D) in various pH medium. The observations of fluorescence spectra were mainly rationalized in terms of a static quenching process at lower concentration of BZC (C(BZC)/C(Lys)<9) and a combined quenching process at higher concentration of BZC (C(BZC)/C(Lys)>9) at pH 7.4 and 8.4. However, the fluorescence quenching was mainly arisen from static quenching by complex formation in all studied drug concentrations at pH 3.5. The structural characteristics of BZC and Lys were probed, and their binding affinities were determined under different pH conditions (pH 3.5, 7.4, and 8.4). The results indicated that the binding abilities of BZC to Lys decreased at the pH below and above the simulative physiological condition (pH 7.4) due to the alterations of the protein secondary and tertiary structures or the structural change of BZC. The effect of BZC on the conformation of Lys was analyzed using UV, synchronous fluorescence and three-dimensional fluorescence under different pH conditions. These results indicate that the binding of BZC to Lys causes apparent change in the secondary and tertiary structures of Lys. The effect of Zn(2+) on the binding constant of BZC with Lys under various pH conditions (pH 3.5, 7.4, and 8.4) was also studied. Copyright © 2011 Elsevier B.V. All rights reserved.

Guidelines for LTS magnet design based on transient stability

NASA Astrophysics Data System (ADS)

Seo, Kazutaka; Morita, Masao

2006-05-01

Stabilities of low critical temperature superconducting (LTS) magnets and their designs are studied and discussed. There are two contradictory necessities; those are low cost and high performance, in the other words, high magnetic field and large current density. Especially, the maximum magnetic fields of the latest high performance Nb 3Sn magnets are around 20 T. Mentioned necessities result in the small stability margins. Needless to say, the superconducting magnet must produce its nominal field reliably. Therefore, maintaining adequate stability margin, the magnet design to draw out the high potential of the superconductor is required. The transient stability of the superconducting magnet is determined by the relationship between mechanical disturbance energy and stability margin. The minimum quench energy (MQE) is one of the index of stability margin and it is defined as the minimum energy to trigger quenching of a superconductor. MQE should be beyond any possible disturbance energy during the operation. It is difficult to identify the mechanical disturbance energy quantitatively. On the contrary, MQE had been evaluated precisely by means of our developed resistive carbon paste heater (CPH). At the same time, we can predict MQE by numerical simulations. Because the magnet comes to quench if the mechanical disturbance exceeds the MQE, the disturbance energies are suspected to be equivalent to MQEs during the magnet-training. When we achieved somewhat larger MQE, we may exclude numbers of training quenches. In this paper, we discuss the guidelines of LTS magnet design from the standpoint of MQE. We represent some case studies for various superconducting magnets and/or some different winding methods.

Atomistic Simulation of Displacement Cascades in Zircon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devanathan, Ram; Weber, William J.; Corrales, Louis R.

2002-05-06

Low energy displacement cascades in zircon (ZrSiO4) initiated by a Zr primary knock-on atom have been investigated by molecular dynamics simulations using a Coulombic model for long-range interactions, Buckingham potential for short-range interactions and Ziegler-Biersack potentials for close pair interactions. Displacements were found to occur mainly in the O sublattice, and O replacements by a ring mechanism were predominant. Clusters containing Si interstitials bridged by O interstitials, vacancy clusters and anti-site defects were found to occur. This Si-O-Si bridging is considerable in quenched liquid ZrSiO4.

Glutathione modified CdTe quantum dots as a label for studying DNA interactions with platinum based cytostatics.

PubMed

Ryvolova, Marketa; Smerkova, Kristyna; Chomoucka, Jana; Hubalek, Jaromir; Adam, Vojtech; Kizek, Rene

2013-03-01

Cisplatin, carboplatin, and oxaliplatin represent three generations of platinum based drugs applied successfully for cancer treatment. As a consequence of the employment of platinum based cytostatics in the cancer treatment, it became necessary to study the mechanism of their action. Current accepted opinion is the formation of Pt-DNA adducts, but the mechanism of their formation is still unclear. Nanomaterials, as a progressively developing branch, can offer a tool for studying the interactions of these drugs with DNA. In this study, fluorescent CdTe quantum dots (QDs, λem = 525 nm) were employed to investigate the interactions of platinum cytostatics (cisplatin, carboplatin, and oxaliplatin) with DNA fragment (500 bp, c = 25 μg/mL). Primarily, the fluorescent behavior of QDs in the presence of platinum cytostatics was monitored and major differences in the interaction of QDs with tested drugs were observed. It was found that the presence of carboplatin (c = 0.25 mg/mL) had no significant influence on QDs fluorescence; however cisplatin and oxaliplatin quenched the fluorescence significantly (average decrease of 20%) at the same concentration. Subsequently, the amount of platinum incorporated in DNA was determined by QDs fluorescence quenching. Best results were reached using oxaliplatin (9.4% quenching). Linear trend (R(2) = 0.9811) was observed for DNA platinated by three different concentrations of oxaliplatin (0.250, 0.125, and 0.063 mg/mL). Correlation with differential pulse voltammetric measurements provided linear trend (R(2) = 0.9511). As a conclusion, especially in the case of oxaliplatin-DNA adducts, the quenching was the most significant compared to cisplatin and nonquenching carboplatin. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study on stabilization and quench protection of coils wound of HTS coated conductors considering quench origins - Proposal of criteria for stabilization and quench protection

NASA Astrophysics Data System (ADS)

Tsukamoto, Osami; Fujimoto, Yasutaka; Takao, Tomoaki

2014-09-01

It has been considered that HTS coils are hard to be quenched because of high quench energy due to high critical temperature and high specific heat of HTS wires. Therefore, attention to quench protection was not much paid. However, HTS coils still have possibility to be quenched during operation by mainly the following two origins, (a) presence of non-recoverable local defects in the conductors and (b) temperature rise of long part of the conductor. Actually, severe quench accidents, such as burning coils, are occurring in various places as scales of HTS increased. Purposes of this paper are to study on behaviors of normal zone and hot spot temperature of wires during quench detect/energy dump sequence and to find criteria for the stability and quench protection. In the paper, criteria are proposed for stability and quench protection of HTS coils. A criterion for the stability is that a coil can be operated stably without a quench against defects in coil windings and that for quench protection is that a coil can be safely protected from damages caused by a quench due to temperature rise of long part of coil wires. The criteria are used as design rules for HTS coils.

Quantum dynamics of thermalizing systems

NASA Astrophysics Data System (ADS)

White, Christopher David; Zaletel, Michael; Mong, Roger S. K.; Refael, Gil

2018-01-01

We introduce a method "DMT" for approximating density operators of 1D systems that, when combined with a standard framework for time evolution (TEBD), makes possible simulation of the dynamics of strongly thermalizing systems to arbitrary times. We demonstrate that the method performs well for both near-equilibrium initial states (Gibbs states with spatially varying temperatures) and far-from-equilibrium initial states, including quenches across phase transitions and pure states.

Visualization in simulation tools: requirements and a tool specification to support the teaching of dynamic biological processes.

PubMed

Jørgensen, Katarina M; Haddow, Pauline C

2011-08-01

Simulation tools are playing an increasingly important role behind advances in the field of systems biology. However, the current generation of biological science students has either little or no experience with such tools. As such, this educational glitch is limiting both the potential use of such tools as well as the potential for tighter cooperation between the designers and users. Although some simulation tool producers encourage their use in teaching, little attempt has hitherto been made to analyze and discuss their suitability as an educational tool for noncomputing science students. In general, today's simulation tools assume that the user has a stronger mathematical and computing background than that which is found in most biological science curricula, thus making the introduction of such tools a considerable pedagogical challenge. This paper provides an evaluation of the pedagogical attributes of existing simulation tools for cell signal transduction based on Cognitive Load theory. Further, design recommendations for an improved educational simulation tool are provided. The study is based on simulation tools for cell signal transduction. However, the discussions are relevant to a broader biological simulation tool set.

Reversible oxygen addition on a triplet sensitizer molecule: protection from excited state depopulation.

PubMed

Filatov, Mikhail A; Heinrich, Ernesta; Busko, Dmitry; Ilieva, Iliyana Z; Landfester, Katharina; Baluschev, Stanislav

2015-03-07

We demonstrate that photoactivated oxygen addition to diphenylanthracene moities can be used as a tool for protection of porphyrin's phosphorescence against oxygen quenching. Phosphorescent palladium(II) tetrabenzoporphyrin, covalently linked to four diphenylanthracene moieties, was synthesized and studied. Upon irradiation with ambient light or red laser in solution in air, addition of oxygen and formation of the corresponding endoperoxides were observed. Heating of the irradiated samples afforded the parent porphyrin material.

Heat Treatment and Properties of Iron and Steel

DTIC Science & Technology

1966-11-01

requirements for quenching media are met satisfactorily by water or aqueous solu- tions of inorganic salts such as table salt or caustic soda, or by...organic chemicals and dyestuffs, and a wide variety of inorganic chemicals. Typical applications are for out- door trim, kitchen equipment, dairy...Steel Co., Reading, Pa. (1948) 564 pages. G. A. Roberts, J. C. Hamaker Jr. and A. R. Johnson, Tool steels, 3rd edition, Am. Soc. Metals, Metals Park

Study on the binding characteristics of hydroxylated polybrominated diphenyl ethers and thyroid transporters using the multispectral technique and computational simulation.

PubMed

Wei, Yuchen; Yi, Zhongsheng; Xu, Jie; Yang, Wu; Yang, Lulu; Liu, Hongyan

2018-04-24

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are a class of toxic environmental pollutants that are persistent, bioaccumulative, and difficult to degrade. Their structure is very similar to the thyroid hormone (T4) and uses the body's thyroid transporter (TTR) binding to interfere with the endocrine balance, disrupting the body's normal physiological activity. According to Fourier transform infrared spectroscopy and dynamics simulation of do_dssp module analysis, there are three kinds of OH-PBDEs that can induce TTR secondary structural changes. Fluorescence spectra and UV-Vis spectra show that for the three kinds of OH-PBDEs for TTR, the main methods of quenching are static quenching and non-radiative energy transfer. According to thermodynamic analysis, ΔG < 0, ΔH > 0, and ΔS > 0 combine to show that the hydrophobic interaction is the main driving force of the combination. From the molecular docking analysis, it was found that 4'-hydroxy-2,2',4,5'- tetrabromodiphenyl ether (4'-OH-BDE49) and 4 hydroxy-2,2',3,4',5,6,6'- heptabromodiphenyl ether (4-OH-BDE188) had a cationic-π interaction with TTR, whereas 4 hydroxy-2,2',3,4,5,5',6- heptabromodiphenyl ether (4-OH-BDE187) was bonded to TTR by hydrogen bonds to form stable complexes. In this paper, we highlight the consistency of spectroscopic experiments and computer simulations so as to provide a reliable analytical method for the toxicological properties of small molecule contaminants.

The acidic pH-induced structural changes in apo-CP43 by spectral methodologies and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Wang, Wang; Li, Xue; Wang, Qiuying; Zhu, Xixi; Zhang, Qingyan; Du, Linfang

2018-01-01

CP43 is closely associated with the photosystem II and exists the plant thylakoid membranes. The acidic pH-induced structural changes had been investigated by fluorescence spectrum, ANS spectrum, RLS spectrum, energy transfer experiment, acrylamide fluorescence quenching assay and MD simulation. The fluorescence spectrum indicated that the structural changes in acidic pH-induced process were a four-state model, which was nature state (N), partial unfolding state (PU), refolding state (R), and molten-globule state (M), respectively. Analysis of ANS spectrum illustrated that inner hydrophobic core exposed partially to surface below pH 2.0 and inferred also that the molten-globule state existed. The RLS spectrum showed the aggregation of apo-CP43 around the pI (pH 4.5-4.0). The alterations of apo-CP43 secondary structure with different acidic treatments were confirmed by FTIR spectrum. The energy transfer experiment and quenching research demonstrated structural change at pH 4.0 was loosest. The RMSF suggested two terminals played an important function in acidic denaturation process. The distance of two terminals shown slight difference in acidic pH-induced process during the unfolding process, both N-terminal and C-terminal occupied the dominant role. However, the N-terminal accounted for the main part in the refolding process. All kinds of SASA values corresponded to spectral results. The tertiary and secondary structure by MD simulation indicated that the part transmembrane α-helix was destroyed at low pH.

Supermassive black holes and their feedback effects in the IllustrisTNG simulation

NASA Astrophysics Data System (ADS)

Weinberger, Rainer; Springel, Volker; Pakmor, Rüdiger; Nelson, Dylan; Genel, Shy; Pillepich, Annalisa; Vogelsberger, Mark; Marinacci, Federico; Naiman, Jill; Torrey, Paul; Hernquist, Lars

2018-06-01

We study the population of supermassive black holes (SMBHs) and their effects on massive central galaxies in the IllustrisTNG cosmological hydrodynamical simulations of galaxy formation. The employed model for SMBH growth and feedback assumes a two-mode scenario in which the feedback from active galactic nuclei occurs through a kinetic, comparatively efficient mode at low accretion rates relative to the Eddington limit, and in the form of a thermal, less efficient mode at high accretion rates. We show that the quenching of massive central galaxies happens coincidently with kinetic-mode feedback, consistent with the notion that active supermassive black cause the low specific star formation rates observed in massive galaxies. However, major galaxy mergers are not responsible for initiating most of the quenching events in our model. Up to black hole masses of about 108.5 M⊙, the dominant growth channel for SMBHs is in the thermal mode. Higher mass black holes stay mainly in the kinetic mode and gas accretion is self-regulated via their feedback, which causes their Eddington ratios to drop, with SMBH mergers becoming the main channel for residual mass growth. As a consequence, the quasar luminosity function is dominated by rapidly accreting, moderately massive black holes in the thermal mode. We show that the associated growth history of SMBHs produces a low-redshift quasar luminosity function and a redshift zero black hole mass - stellar bulge mass relation in good agreement with observations, whereas the simulation tends to over-predict the high-redshift quasar luminosity function.

Resolving ultrafast exciton migration in organic solids at the nanoscale

NASA Astrophysics Data System (ADS)

Penwell, Samuel B.; Ginsberg, Lucas D. S.; Noriega, Rodrigo; Ginsberg, Naomi S.

2017-11-01

Effectiveness of molecular-based light harvesting relies on transport of excitons to charge-transfer sites. Measuring exciton migration, however, has been challenging because of the mismatch between nanoscale migration lengths and the diffraction limit. Instead of using bulk substrate quenching methods, here we define quenching boundaries all-optically with sub-diffraction resolution, thus characterizing spatiotemporal exciton migration on its native nanometre and picosecond scales. By transforming stimulated emission depletion microscopy into a time-resolved ultrafast approach, we measure a 16-nm migration length in poly(2,5-di(hexyloxy)cyanoterephthalylidene) conjugated polymer films. Combined with Monte Carlo exciton hopping simulations, we show that migration in these films is essentially diffusive because intrinsic chromophore energetic disorder is comparable to chromophore inhomogeneous broadening. Our approach will enable previously unattainable correlation of local material structure to exciton migration character, applicable not only to photovoltaic or display-destined organic semiconductors but also to explaining the quintessential exciton migration exhibited in photosynthesis.

Indications for chlororespiration in relation to light regime in the marine diatom Thalassiosira weissflogii.

PubMed

Dijkman, Nicole A; Kroon, Bernd M A

2002-04-01

The marine diatom Thalassiosira weissflogii was cultured under a light regime simulating the daily rise and fall of the sun. The light regime caused a daily cycle in non-photochemical quenching. Remarkable were the changes in fluorescence directly after a light-to-dark transition that occurred in addition to the changes induced by non-photochemical quenching. A transient non-photochemical reduction of PQ and of Q(A) was indicated by a transient increase in apparent F(o) and by changes in the shape of the fluorescence induction curve. The observed changes developed approximately the first 100-120 s after a light-to-dark transition and could be reversed by the application of far-red illumination. Chlororespiration is thought to cause the reduction of PQ and, as the PQ-pool is in equilibrium with Q(A), also a reduction of Q(A). The function and ecological relevance of chlororespiration are discussed.

Quenched results for light quark physics with overlap fermions

NASA Astrophysics Data System (ADS)

Giusti, L.; Hoelbling, C.; Rebbi, C.

2002-03-01

We present results of a quenched QCD simulation with overlap fermions on a lattice of volume V = 16 3 × 32 at β = 6.0, which corresponds to a lattice cutoff of ⋍ 2 GeV and an extension of ⋍ 1.4 fm. From the two-point correlation functions of bilinear operators we extract the pseudoscalar meson masses and the corresponding decay constants. From the GMOR relation we determine the chiral condensate and, by using the K-meson mass as experimental input, we compute the sum of the strange and average up-down quark masses ( m s + overlinem). The needed logarithmic divergent renormalization constant Z S is computed with the RI/MOM non-perturbative renormalization technique. Since the overlap preserves chiral symmetry at finite cutoff and volume, no divergent quark mass and chiral condensate additive renormalizations are required and the results are O( a) improved.

Sodium aluminum-iron phosphate glass-ceramics for immobilization of lanthanide oxide wastes from pyrochemical reprocessing of spent nuclear fuel

NASA Astrophysics Data System (ADS)

Stefanovsky, S. V.; Stefanovsky, O. I.; Kadyko, M. I.; Nikonov, B. S.

2018-03-01

Sodium aluminum (iron) phosphate glass ceramics containing of up to 20 wt.% rare earth (RE) oxides simulating pyroprocessing waste were produced by melting at 1250 °C followed by either quenching or slow cooling to room temperature. The iron-free glass-ceramics were composed of major glass and minor phosphotridymite and monazite. The iron-bearing glass-ceramics were composed of major glass and minor monazite and Na-Al-Fe orthophosphate at low waste loadings (5-10 wt.%) and major orthophosphate and minor monazite as well as interstitial glass at high waste loadings (15-20 wt.%). Slowly cooled samples contained higher amount of crystalline phases than quenched ones. Monazite is major phase for REs. Leach rates from the materials of major elements (Na, Al, Fe, P) are 10-5-10-7 g cm-2 d-1, RE elements - lower than 10-5 g cm-2 d-1.

Investigations of current limiting properties of the MgB2 wires subjected to pulse overcurrents in the benchtop tester

NASA Astrophysics Data System (ADS)

Ye, Lin; Majoros, M.; Campbell, A. M.; Coombs, T.; Harrison, S.; Sargent, P.; Haslett, M.; Husband, M.

2007-04-01

A laboratory scale desktop test system including a cryogenic system, an AC pulse generation system and a real time data acquisition program in LabView/DAQmx, has been developed to evaluate the quench properties of MgB2 wires as an element in a superconducting fault current limiter under pulse overcurrents at 25 K in self-field conditions. The MgB2 samples started from a superconducting state and demonstrated good current limiting properties characterized by a fast transition to the normal state during the first half of the cycle and a continuously limiting effect in the subsequent cycles without burnouts. The experimental and numerical simulation results on the quench behaviour indicate the feasibility of using MgB2 for future superconducting fault current limiter (SFCL) applications. This work is supported by Rolls-Royce Plc and the UK Department of Trade & Industry (DTI).

The application of rational approximation in the calculation of a temperature field with a non-linear surface heat-transfer coefficient during quenching for 42CrMo steel cylinder

NASA Astrophysics Data System (ADS)

Cheng, Heming; Huang, Xieqing; Fan, Jiang; Wang, Honggang

1999-10-01

The calculation of a temperature field has a great influence upon the analysis of thermal stresses and stains during quenching. In this paper, a 42CrMo steel cylinder was used an example for investigation. From the TTT diagram of the 42CrMo steel, the CCT diagram was simulated by mathematical transformation, and the volume fraction of phase constituents was calculated. The thermal physical properties were treated as functions of temperature and the volume fraction of phase constituents. The rational approximation was applied to the finite element method. The temperature field with phase transformation and non-linear surface heat-transfer coefficients was calculated using this technique, which can effectively avoid oscillationin the numerical solution for a small time step. The experimental results of the temperature field calculation coincide with the numerical solutions.

Diverse Formation Mechanisms for Compact Galaxies

NASA Astrophysics Data System (ADS)

Kim, Jin-Ah; Paudel, Sanjaya; Yoon, Suk-Jin

2018-01-01

Compact, quenched galaxies such as M32 are unusual ones located off the mass - size scaling relation defined by normal galaxies. Still, their formation mechanisms remain unsolved. Here we investigate the evolution of ~100 compact, quenched galaxies at z = 0 identified in the Illustris cosmological simulation. We identify three ways for a galaxy to become a compact one and, often, multiple mechanisms operate in a combined manner. First, stripping is responsible for making about a third of compact galaxies. Stripping removes stars from galaxies, usually while keeping their sizes intact. About one third are galaxies that cease their growth early on after entering into more massive, gigantic halos. Finally, about half of compact galaxies, ~ 35 % of which turn out to undergo stripping, experience the compaction due to the highly centrally concentrated star formation. We discuss the evolutionary path of compact galaxies on the mass – size plane for each mechanism in a broader context of dwarf galaxy formation and evolution.

Hadron spectrum of quenched QCD on a 32{sup 3} {times} 64 lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Seyong; Sinclair, D.K.

1992-10-01

Preliminary results from a hadron spectrum calculation of quenched Quantumchromodynamics on a 32{sup 3} {times} 64 lattice at {beta} = 6.5 are reported. The hadron spectrum calculation is done with staggered quarks of masses, m{sub q}a = 0.001, 0.005 and 0.0025. We use two different sources in order to be able to extract the {Delta} mass in addition to the usual local light hadron masses. The numerical simulation is executed on the Intel Touchstone Delta computer. The peak speed of the Delta for a 16 {times} 32 mesh configuration is 41 Gflops for 32 bit precision. The sustained speed formore » our updating code is 9.5 Gflops. A multihit metropolis algorithm combined with an over-relaxation method is used in the updating and the conjugate gradient method is employed for Dirac matrix inversion. Configurations are stored every 1000 sweeps.« less

Hadron spectrum of quenched QCD on a 32[sup 3] [times] 64 lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Seyong; Sinclair, D.K.

1992-10-01

Preliminary results from a hadron spectrum calculation of quenched Quantumchromodynamics on a 32[sup 3] [times] 64 lattice at [beta] = 6.5 are reported. The hadron spectrum calculation is done with staggered quarks of masses, m[sub q]a = 0.001, 0.005 and 0.0025. We use two different sources in order to be able to extract the [Delta] mass in addition to the usual local light hadron masses. The numerical simulation is executed on the Intel Touchstone Delta computer. The peak speed of the Delta for a 16 [times] 32 mesh configuration is 41 Gflops for 32 bit precision. The sustained speed formore » our updating code is 9.5 Gflops. A multihit metropolis algorithm combined with an over-relaxation method is used in the updating and the conjugate gradient method is employed for Dirac matrix inversion. Configurations are stored every 1000 sweeps.« less

Noise focusing in neuronal tissues: Symmetry breaking and localization in excitable networks with quenched disorder

NASA Astrophysics Data System (ADS)

Orlandi, Javier G.; Casademunt, Jaume

2017-05-01

We introduce a coarse-grained stochastic model for the spontaneous activity of neuronal cultures to explain the phenomenon of noise focusing, which entails localization of the noise activity in excitable networks with metric correlations. The system is modeled as a continuum excitable medium with a state-dependent spatial coupling that accounts for the dynamics of synaptic connections. The most salient feature is the emergence at the mesoscale of a vector field V (r ) , which acts as an advective carrier of the noise. This entails an explicit symmetry breaking of isotropy and homogeneity that stems from the amplification of the quenched fluctuations of the network by the activity avalanches, concomitant with the excitable dynamics. We discuss the microscopic interpretation of V (r ) and propose an explicit construction of it. The coarse-grained model shows excellent agreement with simulations at the network level. The generic nature of the observed phenomena is discussed.

Progress on Complex Langevin simulations of a finite density matrix model for QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bloch, Jacques; Glesaan, Jonas; Verbaarschot, Jacobus

We study the Stephanov model, which is an RMT model for QCD at finite density, using the Complex Langevin algorithm. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory rather than to intended theory with dynamical quarks. A detailed analysis of this issue and a potential resolution of the failure of this algorithm are discussed. We study the effect of gauge cooling on the Dirac eigenvalue distribution and time evolution of the norm for various cooling norms, which were specifically designed to remove the pathologies of the complex Langevin evolution. The cooling is further supplementedmore » with a shifted representation for the random matrices. Unfortunately, none of these modifications generate a substantial improvement on the complex Langevin evolution and the final results still do not agree with the analytical predictions.« less

Pulse-shape discrimination and energy quenching of alpha particles in Cs 2LiLaBr 6:Ce 3+

DOE PAGES

Mesick, Katherine Elizabeth; Coupland, Daniel David S.; Stonehill, Laura Catherine

2016-10-19

Cs 2LiLaBr 6:Ce 3+ (CLLB) is an elpasolite scintillator that offers excellent linearity and gamma-ray energy resolution and sensitivity to thermal neutrons with the ability to perform pulse-shape discrimination (PSD) to distinguish gammas and neutrons. Our investigation of CLLB has indicated the presence of intrinsic radioactive alpha background that we have determined to be from actinium contamination of the lanthanum component. We measured the pulse shapes for gamma, thermal neutron, and alpha events and determined that PSD can be performed to separate the alpha background with a moderate figure of merit of 0.98. Here, we also measured the electron-equivalent-energy ofmore » the alpha particles in CLLB and simulated the intrinsic alpha background from 227Ac to determine the quenching factor of the alphas.« less

Characterization of domain-specific interaction of synthesized dye with serum proteins by spectroscopic and docking approaches along with determination of in vitro cytotoxicity and antiviral activity.

PubMed

Rudra, Suparna; Dasmandal, Somnath; Patra, Chiranjit; Patel, Biman Kumar; Paul, Suvendu; Mahapatra, Ambikesh

2017-11-20

The interaction between a synthesized dye with proteins, bovine, and human serum albumin (BSA, HSA, respectively) under physiological conditions has been characterized in detail, by means of steady-state and time-resolved fluorescence, UV-vis absorption, and circular dichroism (CD) techniques. An extensive time-resolved fluorescence spectroscopic characterization of the quenching process has been undertaken in conjugation with temperature-dependent fluorescence quenching studies to divulge the actual quenching mechanism. From the thermodynamic observations, it is clear that the binding process is a spontaneous molecular interaction, in which van der Waals and hydrogen bonding interactions play the major roles. The UV-vis absorption and CD results confirm that the dye can induce conformational and micro-environmental changes of both the proteins. In addition, the dye binding provokes the functionality of the native proteins in terms of esterase-like activity. The average binding distance (r) between proteins and dye has been calculated using FRET. Cytotoxicity and antiviral effects of the dye have been found using Vero cell and HSV-1F virus by performing MTT assay. The AutoDock-based docking simulation reveals the probable binding location of dye within the sub-domain IIA of HSA and IB of BSA.

Nanosecond to submillisecond dynamics in dye-labeled single-stranded DNA, as revealed by ensemble measurements and photon statistics at single-molecule level.

PubMed

Kaji, Takahiro; Ito, Syoji; Iwai, Shigenori; Miyasaka, Hiroshi

2009-10-22

Single-molecule and ensemble time-resolved fluorescence measurements were applied for the investigation of the conformational dynamics of single-stranded DNA, ssDNA, connected with a fluorescein dye by a C6 linker, where the motions both of DNA and the C6 linker affect the geometry of the system. From the ensemble measurement of the fluorescence quenching via photoinduced electron transfer with a guanine base in the DNA sequence, three main conformations were found in aqueous solution: a conformation unaffected by the guanine base in the excited state lifetime of fluorescein, a conformation in which the fluorescence is dynamically quenched in the excited-state lifetime, and a conformation leading to rapid quenching via nonfluorescent complex. The analysis by using the parameters acquired from the ensemble measurements for interphoton time distribution histograms and FCS autocorrelations by the single-molecule measurement revealed that interconversion in these three conformations took place with two characteristic time constants of several hundreds of nanoseconds and tens of microseconds. The advantage of the combination use of the ensemble measurements with the single-molecule detections for rather complex dynamic motions is discussed by integrating the experimental results with those obtained by molecular dynamics simulation.

Whole cell quenched flow analysis.

PubMed

Chiang, Ya-Yu; Haeri, Sina; Gizewski, Carsten; Stewart, Joanna D; Ehrhard, Peter; Shrimpton, John; Janasek, Dirk; West, Jonathan

2013-12-03

This paper describes a microfluidic quenched flow platform for the investigation of ligand-mediated cell surface processes with unprecedented temporal resolution. A roll-slip behavior caused by cell-wall-fluid coupling was documented and acts to minimize the compression and shear stresses experienced by the cell. This feature enables high-velocity (100-400 mm/s) operation without impacting the integrity of the cell membrane. In addition, rotation generates localized convection paths. This cell-driven micromixing effect causes the cell to become rapidly enveloped with ligands to saturate the surface receptors. High-speed imaging of the transport of a Janus particle and fictitious domain numerical simulations were used to predict millisecond-scale biochemical switching times. Dispersion in the incubation channel was characterized by microparticle image velocimetry and minimized by using a horizontal Hele-Shaw velocity profile in combination with vertical hydrodynamic focusing to achieve highly reproducible incubation times (CV = 3.6%). Microfluidic quenched flow was used to investigate the pY1131 autophosphorylation transition in the type I insulin-like growth factor receptor (IGF-1R). This predimerized receptor undergoes autophosphorylation within 100 ms of stimulation. Beyond this demonstration, the extreme temporal resolution can be used to gain new insights into the mechanisms underpinning a tremendous variety of important cell surface events.

Quench protection study of the updated MQXF for the LHC luminosity upgrade (HiLumi LHC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marinozzi, Vittorio; Ambrosio, Giorgio; Ferracin, Paolo

In 2023, the LHC luminosity will be increased, aiming at reaching 3000 fb-1 integrated over ten years. To obtain this target, new Nb 3Sn low-β quadrupoles (MQXF) have been designed for the interaction regions. These magnets present a very large aperture (150 mm, to be compared with the 70 mm of the present NbTi quadrupoles) and a very large stored energy density (120 MJ/m 3). For these reasons, quench protection is one of the most challenging aspects of the design of these magnets. In fact, protection studies of a previous design showed that the simulated hot spot temperature was verymore » close to the maximum allowed limit of 350 K; this challenge motivated improvements in the current discharge modeling, taking into account the so-called dynamic effects on the apparent magnet inductance. Moreover, quench heaters design has been studied to be going into more details. In this study, a protection study of the updated MQXF is presented, benefiting from the experience gained by studying the previous design. As a result, a study of the voltages between turns in the magnet is also presented during both normal operation and most important failure scenarios.« less

Calibration of Fast Fiber-Optic Beam Loss Monitors for the Advanced Photon Source Storage Ring Superconducting Undulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dooling, J.; Harkay, K.; Ivanyushenkov, Y.

2015-01-01

We report on the calibration and use of fast fiber-optic (FO) beam loss monitors (BLMs) in the Advanced Photon Source storage ring (SR). A superconducting undulator prototype (SCU0) has been operating in SR Sector 6 (“ID6”) since the beginning of CY2013, and another undulator SCU1 (a 1.1-m length undulator that is three times the length of SCU0) is scheduled for installation in Sector 1 (“ID1”) in 2015. The SCU0 main coil often quenches during beam dumps. MARS simulations have shown that relatively small beam loss (<1 nC) can lead to temperature excursions sufficient to cause quenchingwhen the SCU0windings are nearmore » critical current. To characterize local beam losses, high-purity fused-silica FO cables were installed in ID6 on the SCU0 chamber transitions and in ID1 where SCU1 will be installed. These BLMs aid in the search for operating modes that protect the SCU structures from beam-loss-induced quenching. In this paper, we describe the BLM calibration process that included deliberate beam dumps at locations of BLMs. We also compare beam dump events where SCU0 did and did not quench.« less

The investigation of the interaction between piracetam and bovine serum albumin by spectroscopic methods

NASA Astrophysics Data System (ADS)

Guo, Xingjia; Han, Xiaowei; Tong, Jian; Guo, Chuang; Yang, Wenfeng; Zhu, Jifen; Fu, Bing

2010-03-01

The interaction between piracetam (OPA) with bovine serum albumin (BSA) has been thoroughly studied by fluorescence quenching technique in combination with UV-vis absorption, Fourier transform infrared (FT-IR), and circular dichroism (CD) spectroscopies under the simulative physiological conditions. The quenching of BSA fluorescence by OPA was found to be a static quenching process. The binding constants ( K a) are 3.014, 2.926, and 2.503 × 10 3 M -1 at 292, 298, and 309 K, respectively. According to the van't Hoff equation, the thermodynamic functions standard enthalpy (Δ H) and standard entropy (Δ S) for the reaction were calculated to be -74.560 kJ mol -1 and -159.380 J mol -1 K -1, which indicated that OPA binds to BSA mainly by hydrogen bonds and van der Waals interactions. The binding distance between BSA and OPA was calculated to be 4.10 nm according to the theory of FÖrster's non-radiation energy transfer. The displacement experiments confirmed that OPA could bind to the site I of BSA. Furthermore, the effects of pH and some common ions on the binding constant were also examined. And the alterations of protein secondary structure in the presence of OPA were observed by the CD and FT-IR spectra.

Quench protection study of the updated MQXF for the LHC luminosity upgrade (HiLumi LHC)

DOE PAGES

Marinozzi, Vittorio; Ambrosio, Giorgio; Ferracin, Paolo; ...

2016-06-01

In 2023, the LHC luminosity will be increased, aiming at reaching 3000 fb-1 integrated over ten years. To obtain this target, new Nb 3Sn low-β quadrupoles (MQXF) have been designed for the interaction regions. These magnets present a very large aperture (150 mm, to be compared with the 70 mm of the present NbTi quadrupoles) and a very large stored energy density (120 MJ/m 3). For these reasons, quench protection is one of the most challenging aspects of the design of these magnets. In fact, protection studies of a previous design showed that the simulated hot spot temperature was verymore » close to the maximum allowed limit of 350 K; this challenge motivated improvements in the current discharge modeling, taking into account the so-called dynamic effects on the apparent magnet inductance. Moreover, quench heaters design has been studied to be going into more details. In this study, a protection study of the updated MQXF is presented, benefiting from the experience gained by studying the previous design. As a result, a study of the voltages between turns in the magnet is also presented during both normal operation and most important failure scenarios.« less

Photonic simulation of entanglement growth and engineering after a spin chain quench.

PubMed

Pitsios, Ioannis; Banchi, Leonardo; Rab, Adil S; Bentivegna, Marco; Caprara, Debora; Crespi, Andrea; Spagnolo, Nicolò; Bose, Sougato; Mataloni, Paolo; Osellame, Roberto; Sciarrino, Fabio

2017-11-17

The time evolution of quantum many-body systems is one of the most important processes for benchmarking quantum simulators. The most curious feature of such dynamics is the growth of quantum entanglement to an amount proportional to the system size (volume law) even when interactions are local. This phenomenon has great ramifications for fundamental aspects, while its optimisation clearly has an impact on technology (e.g., for on-chip quantum networking). Here we use an integrated photonic chip with a circuit-based approach to simulate the dynamics of a spin chain and maximise the entanglement generation. The resulting entanglement is certified by constructing a second chip, which measures the entanglement between multiple distant pairs of simulated spins, as well as the block entanglement entropy. This is the first photonic simulation and optimisation of the extensive growth of entanglement in a spin chain, and opens up the use of photonic circuits for optimising quantum devices.

Challenges of NDE simulation tool validation, optimization, and utilization for composites

NASA Astrophysics Data System (ADS)

Leckey, Cara A. C.; Seebo, Jeffrey P.; Juarez, Peter

2016-02-01

Rapid, realistic nondestructive evaluation (NDE) simulation tools can aid in inspection optimization and prediction of inspectability for advanced aerospace materials and designs. NDE simulation tools may someday aid in the design and certification of aerospace components; potentially shortening the time from material development to implementation by industry and government. Furthermore, ultrasound modeling and simulation are expected to play a significant future role in validating the capabilities and limitations of guided wave based structural health monitoring (SHM) systems. The current state-of-the-art in ultrasonic NDE/SHM simulation is still far from the goal of rapidly simulating damage detection techniques for large scale, complex geometry composite components/vehicles containing realistic damage types. Ongoing work at NASA Langley Research Center is focused on advanced ultrasonic simulation tool development. This paper discusses challenges of simulation tool validation, optimization, and utilization for composites. Ongoing simulation tool development work is described along with examples of simulation validation and optimization challenges that are more broadly applicable to all NDE simulation tools. The paper will also discuss examples of simulation tool utilization at NASA to develop new damage characterization methods for composites, and associated challenges in experimentally validating those methods.

Monte Carlo simulation of ferroelectric domain growth

NASA Astrophysics Data System (ADS)

Li, B. L.; Liu, X. P.; Fang, F.; Zhu, J. L.; Liu, J.-M.

2006-01-01

The kinetics of two-dimensional isothermal domain growth in a quenched ferroelectric system is investigated using Monte Carlo simulation based on a realistic Ginzburg-Landau ferroelectric model with cubic-tetragonal (square-rectangle) phase transitions. The evolution of the domain pattern and domain size with annealing time is simulated, and the stability of trijunctions and tetrajunctions of domain walls is analyzed. It is found that in this much realistic model with strong dipole alignment anisotropy and long-range Coulomb interaction, the powerlaw for normal domain growth still stands applicable. Towards the late stage of domain growth, both the average domain area and reciprocal density of domain wall junctions increase linearly with time, and the one-parameter dynamic scaling of the domain growth is demonstrated.

Induction hardening treatment and simulation for a grey cast iron used in engine cylinder liners

NASA Astrophysics Data System (ADS)

Castellanos-Leal, E. L.; Miranda, D. A.; Coy, A. E.; Barrero, J. G.; González, J. A.; Vesga Rueda, O. P.

2017-01-01

In this research, a technical study of induction hardening in a grey cast iron used in engine cylinder liners manufactured by LAVCO Ltda., a Colombian foundry company, was carried out. Metallurgical parameters such as austenitization temperature, cooling rate, and quenching severity were determined. These factors are exclusively dependent on chemical composition and initial microstructure of grey cast iron. Simulations of induction heating through finite elements method were performed and, the most appropriate experimental conditions to achieve the critical transformation temperature was evaluated to reach a proper surface hardening on the piece. Preliminary results revealed an excellent approximation between simulation and heating test performed with a full bridge inverter voltage adapted with local technology.

Influence of quenching agent on microstructure, properties and thermal stress of SiC{sub p}/2009 composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Tianbing, E-mail: tianbing_1988@sina.com

15% vol. SiC{sub p}/2009 composites prepared by powder metallurgy were quenched in room temperature water and 20% polyethylene glycol (PEG) solution respectively, then aged naturally. The influence of quenching agent on microstructure, properties and thermal stress of SiC{sub p}/2009 composites were investigated by means of scanning/transmission electron microscope, hardness and tensile test. The results showed that the number of precipitated phase in water quenched composites increased, with much finer in size and more homogeneous in distribution compared with 20% PEG quenched one. Meanwhile, the density of dislocation in composites by water quenching was also much higher. Intergranular corrosion did notmore » occur with the two quenching agents. The 20% PEG quenched composites exhibited slight lower hardness and higher electrical conductivity than that of water quenched one. The two quenched composites showed same level in tensile strength, but the yield strength of water-quenched composites was higher (8 MPa, 3%). The usage of 20% PEG reduced thermal stress and minimized warping deformation of the parts, it is a more suitable quenching agent for SiC{sub p}/2009 composites in engineering application fields. - Highlights: •SiC{sub p}/2009 composites quenched by water and 20% PEG solution were investigated. •Aging precipitation behavior of SiC{sub p}/2009 composites is sensitive to quenchant. •Influence of quenching agent on properties of SiC{sub p}/2009 composites are minimal. •Quenching with 20% PEG reduces thermal stress of SiC{sub p}/2009 composites remarkably. •20% PEG is a more suitable quenching agent for SiC{sub p}/2009 composites than water.« less

Using Transom Jack in the Human Engineering Analysis of the Materials Science Research Rack-1 and Quench Module Insert

NASA Technical Reports Server (NTRS)

Dunn, Mariea C.; Alves, Jeffrey R.; Hutchinson, Sonya L.

1999-01-01

This paper describes the human engineering analysis performed on the Materials Science Research Rack-1 and Quench Module Insert (MSRR-1/QMI) using Transom Jack (Jack) software. The Jack software was used to model a virtual environment consisting of the MSRR-1/QMI hardware configuration and human figures representing the 95th percentile male and 5th percentile female. The purpose of the simulation was to assess the human interfaces in the design for their ability to meet the requirements of the Pressurized Payloads Interface Requirements Document - International Space Program, Revision C (SSP 57000). Jack was used in the evaluation because of its ability to correctly model anthropometric body measurements and the physical behavior of astronauts working in microgravity, which is referred to as the neutral body posture. The Jack model allows evaluation of crewmember interaction with hardware through task simulation including but not limited to collision avoidance behaviors, hand/eye coordination, reach path planning, and automatic grasping to part contours. Specifically, this virtual simulation depicts the human figures performing the QMI installation and check-out, sample cartridge insertion and removal, and gas bottle drawer removal. These tasks were evaluated in terms of adequate clearance in reach envelopes, adequate accessibility in work envelopes, appropriate line of sight in visual envelopes, and accommodation of full size range for male and female stature maneuverability. The results of the human engineering analysis virtual simulation indicate that most of the associated requirements of SSP 57000 were met. However, some hardware design considerations and crew procedures modifications are recommended to improve accessibility, provide an adequate work envelope, reduce awkward body posture, and eliminate permanent protrusions.

Hybrid finite-volume/transported PDF method for the simulation of turbulent reactive flows

NASA Astrophysics Data System (ADS)

Raman, Venkatramanan

A novel computational scheme is formulated for simulating turbulent reactive flows in complex geometries with detailed chemical kinetics. A Probability Density Function (PDF) based method that handles the scalar transport equation is coupled with an existing Finite Volume (FV) Reynolds-Averaged Navier-Stokes (RANS) flow solver. The PDF formulation leads to closed chemical source terms and facilitates the use of detailed chemical mechanisms without approximations. The particle-based PDF scheme is modified to handle complex geometries and grid structures. Grid-independent particle evolution schemes that scale linearly with the problem size are implemented in the Monte-Carlo PDF solver. A novel algorithm, in situ adaptive tabulation (ISAT) is employed to ensure tractability of complex chemistry involving a multitude of species. Several non-reacting test cases are performed to ascertain the efficiency and accuracy of the method. Simulation results from a turbulent jet-diffusion flame case are compared against experimental data. The effect of micromixing model, turbulence model and reaction scheme on flame predictions are discussed extensively. Finally, the method is used to analyze the Dow Chlorination Reactor. Detailed kinetics involving 37 species and 158 reactions as well as a reduced form with 16 species and 21 reactions are used. The effect of inlet configuration on reactor behavior and product distribution is analyzed. Plant-scale reactors exhibit quenching phenomena that cannot be reproduced by conventional simulation methods. The FV-PDF method predicts quenching accurately and provides insight into the dynamics of the reactor near extinction. The accuracy of the fractional time-stepping technique in discussed in the context of apparent multiple-steady states observed in a non-premixed feed configuration of the chlorination reactor.

High-pressure gas quenching in cold chambers for increased cooling capacity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Segerberg, S.; Troell, E.

1996-12-31

Gas quenching for the hardening of steel parts is a lower-pollution alternative to quenching in quenchants such as oil or salt. As the surfaces of the cooled parts remain clean after gas quenching, there is no need to wash them after heat treatment, which reduces the consumption of oils and detergents. The fire risk and ventilation requirements of oil quenching are eliminated. In addition, some trials have shown that gas quenching has a positive effect on distortion, representing a saving in finishing work and thus a reduction in costs. Today, gas quenching is used almost solely in vacuum furnaces. Quenchingmore » is normally performed in the same chamber as heating, which means that besides quenching the batch, the quenching system must also remove heat from the heating elements and insulation of the furnace. Previous trials performed by IVF have shown that gas quenching with helium of ball bearing and carburizing steels (and other steels) in sizes up to 25 mm at pressures up to 20 bar in a vacuum furnace can achieve quenching rates and hardnesses similar to those achieved by hot quenching oils. This quenching performance is not, however, capable of dealing with larger sizes or lower-alloy steels. At IVF`s request, ALD Vacuum Technologies GmbH has developed a cold high-pressure gas quenching chamber that is independent of the furnace. As a result, there is no need to cool insulation or heating elements. Quenching can be carried out in the chamber at pressures of up to 40 bar for helium or up to 10 bar for nitrogen. The quenching chamber has been supplied to IVF, and has been used for experimental quenching of steel test pieces and components. Temperatures have been recorded by using some Inconel 600 test probes, {phi} 12,5 x 60 mm, with thermocouples in their centers.« less

Accurate Mapping of Multilevel Rydberg Atoms on Interacting Spin-1 /2 Particles for the Quantum Simulation of Ising Models

NASA Astrophysics Data System (ADS)

de Léséleuc, Sylvain; Weber, Sebastian; Lienhard, Vincent; Barredo, Daniel; Büchler, Hans Peter; Lahaye, Thierry; Browaeys, Antoine

2018-03-01

We study a system of atoms that are laser driven to n D3 /2 Rydberg states and assess how accurately they can be mapped onto spin-1 /2 particles for the quantum simulation of anisotropic Ising magnets. Using nonperturbative calculations of the pair potentials between two atoms in the presence of electric and magnetic fields, we emphasize the importance of a careful selection of experimental parameters in order to maintain the Rydberg blockade and avoid excitation of unwanted Rydberg states. We benchmark these theoretical observations against experiments using two atoms. Finally, we show that in these conditions, the experimental dynamics observed after a quench is in good agreement with numerical simulations of spin-1 /2 Ising models in systems with up to 49 spins, for which numerical simulations become intractable.

Quorum quenching is an antivirulence strategy employed by endophytic bacteria.

PubMed

Kusari, Parijat; Kusari, Souvik; Lamshöft, Marc; Sezgin, Selahaddin; Spiteller, Michael; Kayser, Oliver

2014-08-01

Bacteria predominantly use quorum sensing to regulate a plethora of physiological activities such as cell-cell crosstalk, mutualism, virulence, competence, biofilm formation, and antibiotic resistance. In this study, we investigated how certain potent endophytic bacteria harbored in Cannabis sativa L. plants use quorum quenching as an antivirulence strategy to disrupt the cell-to-cell quorum sensing signals in the biosensor strain, Chromobacterium violaceum. We used a combination of high-performance liquid chromatography high-resolution mass spectrometry (HPLC-ESI-HRMS(n)) and matrix-assisted laser desorption ionization imaging high-resolution mass spectrometry (MALDI-imaging-HRMS) to first quantify and visualize the spatial distribution of the quorum sensing molecules in the biosensor strain, C. violaceum. We then showed, both quantitatively and visually in high spatial resolution, how selected endophytic bacteria of C. sativa can selectively and differentially quench the quorum sensing molecules of C. violaceum. This study provides fundamental insights into the antivirulence strategies used by endophytes in order to survive in their ecological niches. Such defense mechanisms are evolved in order to thwart the plethora of pathogens invading associated host plants in a manner that prevents the pathogens from developing resistance against the plant/endophyte bioactive secondary metabolites. This work also provides evidence towards utilizing endophytes as tools for biological control of bacterial phytopathogens. In continuation, such insights would even afford new concepts and strategies in the future for combating drug resistant bacteria by quorum-inhibiting clinical therapies.

Structural and Biochemical Characterization of AidC, a Quorum-Quenching Lactonase With Atypical Selectivity

PubMed Central

Mascarenhas, Romila; Thomas, Pei W.; Wu, Chun-Xiang; Nocek, Boguslaw P.; Hoang, Quyen Q.; Liu, Dali; Fast, Walter

2015-01-01

Quorum-quenching catalysts are of interest for potential application as biochemical tools to interrogate interbacterial communication pathways, as anti-biofouling agents, and as anti-infective agents in plants and animals. Herein, the structure and function of AidC, an N-acyl-L-homoserine (AHL) lactonase from Chryseobacterium, is characterized. Steady-state kinetics show that zinc-supplemented AidC is one of the most efficient wild-type quorum-quenching enzymes characterized to date, with a kcat/KM value of approximately 2 × 106 M−1s−1 for N-heptanoyl-L-homoserine lactone. The enzyme has stricter substrate selectivity and significantly lower KM values (ca. 50 μM for preferred substrates) than typical AHL lactonases (ca. > 1 mM). X-ray crystal structures of AidC alone, and with the product N-hexanoyl-L-homoserine were determined at resolutions of 1.09 and 1.67 Å, respectively. Each structure displays as a dimer, and dimeric oligiomerization was also observed in solution by size-exclusion chromatography coupled with multi-angle light scattering. The structures reveal two atypical features as compared to previously characterized AHL lactonases: a ‘kinked’ α-helix that forms part of a closed binding pocket which provides affinity and enforces selectivity for AHL substrates, and an active-site His substitution that is usually found in a homologous family of phosphodiesterases. Implications for the catalytic mechanism of AHL lactonases are discussed. PMID:26115006

Preparation and preliminary characterization of crystallizing fluorescent derivatives of chicken egg white lysozyme

NASA Astrophysics Data System (ADS)

Sumida, John P.; Forsythe, Elizabeth L.; Pusey, Marc L.

2001-11-01

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow and 5-(2-aminoethyl)aminonapthalene-1-sulfonic acid (EDANS) have been attached to the side chain carboxyl of Asp 101 using a carbodiimide coupling procedure. Asp 101 lies within the active site cleft, and it is believed that the probes are "buried" within that cleft. Lucifer yellow and EDANS probes with iodoacetamide reactive groups have been bound to His 15, located on the "back side" of the molecule relative to the active site. All the derivatives fluoresce in the solution and the crystalline states. Fluorescence characterization has focused on determination of binding effects on the probe quantum yield, lifetime, absorption and emission spectra, and quenching by added solutes. Quenching studies show that, as postulated, the Asp 101-bound probes are partially sheltered from the bulk solution by their location within the active site cleft. Probes bound to His 15 have quenching constants about equal to those for the free probes, indicating that this site is highly exposed to the bulk solution.

Sensitive detection of alkaline phosphatase by switching on gold nanoclusters fluorescence quenched by pyridoxal phosphate.

PubMed

Halawa, Mohamed Ibrahim; Gao, Wenyue; Saqib, Muhammad; Kitte, Shimeles Addisu; Wu, Fengxia; Xu, Guobao

2017-09-15

In this work, we designed highly sensitive and selective luminescent detection method for alkaline phosphatase using bovine serum albumin functionalized gold nanoclusters (BSA-AuNCs) as the nanosensor probe and pyridoxal phosphate as the substrate of alkaline phosphatase. We found that pyridoxal phosphate can quench the fluorescence of BSA-AuNCs and pyridoxal has little effect on the fluorescence of BSA-AuNCs. The proposed mechanism of fluorescence quenching by PLP was explored on the basis of data obtained from high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), UV-vis spectrophotometry, fluorescence spectroscopy, fluorescence decay time measurements and circular dichroism (CD) spectroscopy. Alkaline phosphatase catalyzes the hydrolysis of pyridoxal phosphate to generate pyridoxal, restoring the fluorescence of BSA-AuNCs. Therefore, a recovery type approach has been developed for the sensitive detection of alkaline phosphatase in the range of 1.0-200.0U/L (R 2 =0.995) with a detection limit of 0.05U/L. The proposed sensor exhibit excellent selectivity among various enzymes, such as glucose oxidase, lysozyme, trypsin, papain, and pepsin. The present switch-on fluorescence sensing strategy for alkaline phosphatase was successfully applied in human serum plasma with good recoveries (100.60-104.46%), revealing that this nanosensor probe is a promising tool for ALP detection. Copyright © 2017 Elsevier B.V. All rights reserved.

A Fixed-Wing Aircraft Simulation Tool for Improving the efficiency of DoD Acquisition

DTIC Science & Technology

2015-10-05

simulation tool , CREATETM-AV Helios [12-14], a high fidelity rotary wing vehicle simulation tool , and CREATETM-AV DaVinci [15-16], a conceptual through...05/2015 Oct 2008-Sep 2015 A Fixed-Wing Aircraft Simulation Tool for Improving the Efficiency of DoD Acquisition Scott A. Morton and David R...multi-disciplinary fixed-wing virtual aircraft simulation tool incorporating aerodynamics, structural dynamics, kinematics, and kinetics. Kestrel allows

Quantum Spin Glasses, Annealing and Computation

NASA Astrophysics Data System (ADS)

Chakrabarti, Bikas K.; Inoue, Jun-ichi; Tamura, Ryo; Tanaka, Shu

2017-05-01

List of tables; List of figures, Preface; 1. Introduction; Part I. Quantum Spin Glass, Annealing and Computation: 2. Classical spin models from ferromagnetic spin systems to spin glasses; 3. Simulated annealing; 4. Quantum spin glass; 5. Quantum dynamics; 6. Quantum annealing; Part II. Additional Notes: 7. Notes on adiabatic quantum computers; 8. Quantum information and quenching dynamics; 9. A brief historical note on the studies of quantum glass, annealing and computation.

Multistage Monte Carlo simulation of jet modification in a static medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, S.; Park, C.; Barbieri, R. A.

In this work, the modification of hard jets in an extended static medium held at a fixed temperature is studied using three different Monte Carlo event generators: linear Boltzmann transport (LBT), modular all twist transverse-scattering elastic-drag and radiation (MATTER), and modular algorithm for relativistic treatment of heavy-ion interactions (MARTINI). Each event generator contains a different set of assumptions regarding the energy and virtuality of the partons within a jet versus the energy scale of the medium and, hence, applies to a different epoch in the space-time history of the jet evolution. Here modeling is developed where a jet may sequentiallymore » transition from one generator to the next, on a parton-by-parton level, providing a detailed simulation of the space-time evolution of medium modified jets over a much broader dynamic range than has been attempted previously in a single calculation. Comparisons are carried out for different observables sensitive to jet quenching, including the parton fragmentation function and the azimuthal distribution of jet energy around the jet axis. The effect of varying the boundary between different generators is studied and a theoretically motivated criterion for the location of this boundary is proposed. Lastly, the importance of such an approach with coupled generators to the modeling of jet quenching is discussed.« less

Multistage Monte Carlo simulation of jet modification in a static medium

DOE PAGES

Cao, S.; Park, C.; Barbieri, R. A.; ...

2017-08-22

In this work, the modification of hard jets in an extended static medium held at a fixed temperature is studied using three different Monte Carlo event generators: linear Boltzmann transport (LBT), modular all twist transverse-scattering elastic-drag and radiation (MATTER), and modular algorithm for relativistic treatment of heavy-ion interactions (MARTINI). Each event generator contains a different set of assumptions regarding the energy and virtuality of the partons within a jet versus the energy scale of the medium and, hence, applies to a different epoch in the space-time history of the jet evolution. Here modeling is developed where a jet may sequentiallymore » transition from one generator to the next, on a parton-by-parton level, providing a detailed simulation of the space-time evolution of medium modified jets over a much broader dynamic range than has been attempted previously in a single calculation. Comparisons are carried out for different observables sensitive to jet quenching, including the parton fragmentation function and the azimuthal distribution of jet energy around the jet axis. The effect of varying the boundary between different generators is studied and a theoretically motivated criterion for the location of this boundary is proposed. Lastly, the importance of such an approach with coupled generators to the modeling of jet quenching is discussed.« less

Photophysical Characterization of Enhanced 6-Methylisoxanthopterin Fluorescence in Duplex DNA.

PubMed

Moreno, Andrew; Knee, J L; Mukerji, Ishita

2016-12-08

The structure and dynamic motions of bases in DNA duplexes and other constructs are important for understanding mechanisms of selectivity and recognition of DNA-binding proteins. The fluorescent guanine analogue, 6-methylisoxanthopterin 6-MI, is well suited to this purpose as it exhibits an unexpected 3- to 4-fold increase in relative quantum yield upon duplex formation when incorporated into the following sequences: ATFAA, AAFTA, or ATFTA (where F represents 6-MI). To better understand some of the factors leading to the 6-MI fluorescence increase upon duplex formation, we characterized the effect of local sequence and structural perturbations on 6-MI photophysics through temperature melts, quantum yield measurements, fluorescence quenching assays, and fluorescence lifetime measurements. By examining 21 sequences we have determined that the duplex-enhanced fluorescence (DEF) depends on the composition of bases adjacent to 6-MI and the presence of adenines at locations n ± 2 from the probe. Investigation of duplex stability and local solvent accessibility measurements support a model in which the DEF arises from a constrained geometry of 6-MI in the duplex, which remains H-bonded to cytosine, stacked with adjacent bases and inaccessible to quenchers. Perturbation of DNA structure through the introduction of an unpaired base 3' to 6-MI or a mismatched basepair increases 6-MI dynamic motion leading to fluorescence quenching and a reduction in quantum yield. Molecular dynamics simulations suggest the enhanced fluorescence results from a greater degree of twist at the X-F step relative to the quenched duplexes examined. These results point to a model where adenine residues located at n ± 2 from 6-MI induce a structural geometry with greater twist in the duplex that hinders local motion reducing dynamic quenching and producing an increase in 6-MI fluorescence.

Influence of Transformation Plasticity on the Distribution of Internal Stress in Three Water-Quenched Cylinders

NASA Astrophysics Data System (ADS)

Liu, Yu; Qin, Shengwei; Zhang, Jiazhi; Wang, Ying; Rong, Yonghua; Zuo, Xunwei; Chen, Nailu

2017-10-01

Based on the hardenability of three medium carbon steels, cylinders with the same 60-mm diameter and 240-mm length were designed for quenching in water to obtain microstructures, including a pearlite matrix (Chinese steel mark: 45), a bainite matrix (42CrMo), and a martensite matrix (40CrNiMo). Through the combination of normalized functions describing transformation plasticity (TP), the thermo-elasto-plastic constitutive equation was deduced. The results indicate that the finite element simulation (FES) of the internal stress distribution in the three kinds of hardenable steel cylinders based on the proposed exponent-modified (Ex-Modified) normalized function is more consistent with the X-ray diffraction (XRD) measurements than those based on the normalized functions proposed by Abrassart, Desalos, and Leblond, which is attributed to the fact that the Ex-Modified normalized function better describes the TP kinetics. In addition, there was no significant difference between the calculated and measured stress distributions, even though TP was taken into account for the 45 carbon steel; that is, TP can be ignored in FES. In contrast, in the 42CrMo and 40CrNiMo alloyed steels, the significant effect of TP on the residual stress distributions was demonstrated, meaning that TP must be included in the FES. The rationality of the preceding conclusions was analyzed. The complex quenching stress is a consequence of interactions between the thermal and phase transformation stresses. The separated calculations indicate that the three steels exhibit similar thermal stress distributions for the same water-quenching condition, but different phase transformation stresses between 45 carbon steel and alloyed steels, leading to different distributions of their axial and tangential stresses.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Shuhua; Bishop, Christopher B.; Moreo, Adriana

The phase diagram of electron-doped pnictides is studied varying the temperature, electronic density, and isotropic in-plane quenched disorder strength and dilution by means of computational techniques applied to a three-orbital (xz,yz,xy) spin-fermion model with lattice degrees of freedom. In experiments, chemical doping introduces disorder but in theoretical studies the relationship between electronic doping and the randomly located dopants, with their associated quenched disorder, is difficult to address. Moreover, in this publication, the use of computational techniques allows us to study independently the effects of electronic doping, regulated by a global chemical potential, and impurity disorder at randomly selected sites. Surprisingly,more » our Monte Carlo simulations reveal that the fast reduction with doping of the N eel T N and the structural T S transition temperatures, and the concomitant stabilization of a robust nematic state, is primarily controlled in our model by the magnetic dilution associated with the in-plane isotropic disorder introduced by Fe substitution. In the doping range studied, changes in the Fermi surface produced by electron doping affect only slightly both critical temperatures. Our results also suggest that the specific material-dependent phase diagrams experimentally observed could be explained as a consequence of the variation in disorder profiles introduced by the different dopants. Finally, our findings are also compatible with neutron scattering and scanning tunneling microscopy, unveiling a patchy network of locally magnetically ordered clusters with anisotropic shapes, even though the quenched disorder is locally isotropic. Our study reveals a remarkable and unexpected degree of complexity in pnictides: the fragile tendency to nematicity intrinsic of translational invariant electronic systems needs to be supplemented by quenched disorder and dilution to stabilize the robust nematic phase experimentally found in electron-doped 122 compounds.« less

Return to [Log-]Normalcy: Rethinking Quenching, The Star Formation Main Sequence, and Perhaps Much More

NASA Astrophysics Data System (ADS)

Abramson, Louis E.; Gladders, Michael D.; Dressler, Alan; Oemler, Augustus, Jr.; Poggianti, Bianca; Vulcani, Benedetta

2016-11-01

Knowledge of galaxy evolution rests on cross-sectional observations of different objects at different times. Understanding of galaxy evolution rests on longitudinal interpretations of how these data relate to individual objects moving through time. The connection between the two is often assumed to be clear, but we use a simple “physics-free” model to show that it is not and that exploring its nuances can yield new insights. Comprising nothing more than 2094 loosely constrained lognormal star formation histories (SFHs), the model faithfully reproduces the following data it was not designed to match: stellar mass functions at z≤slant 8; the slope of the star formation rate/stellar mass relation (the SFR “Main Sequence”) at z≤slant 6; the mean {sSFR}(\\equiv {SFR}/{M}* ) of low-mass galaxies at z≤slant 7; “fast-” and “slow-track” quenching; downsizing; and a correlation between formation timescale and {sSFR}({M}* ,t) similar to results from simulations that provides a natural connection to bulge growth. We take these findings—which suggest that quenching is the natural downturn of all SFHs affecting galaxies at rates/times correlated with their densities—to mean that: (1) models in which galaxies are diversified on Hubble timescales by something like initial conditions rival the dominant grow-and-quench framework as good descriptions of the data; or (2) absent spatial information, many metrics of galaxy evolution are too undiscriminating—if not inherently misleading—to confirm a unique explanation. We outline future tests of our model but stress that, even if ultimately incorrect, it illustrates how exploring different paradigms can aid learning and, we hope, more detailed modeling efforts.

Fluorescent Sensors Based on Aggregation-Induced Emission: Recent Advances and Perspectives.

PubMed

Gao, Meng; Tang, Ben Zhong

2017-10-27

Fluorescent sensors with advantages of excellent sensitivity, rapid response, and easy operation are emerging as powerful tools in environmental monitoring, biological research, and disease diagnosis. However, conventional fluorophores featured with π-planar structures usually suffer from serious self-quenching in the aggregated state, poor photostability, and small Stokes' shift. In contrast to conventional aggregation-caused quenching (ACQ) fluorophores, the newly emerged aggregation-induced emission fluorogens (AIEgens) are featured with high emission efficiency in the aggregated state, which provide unique opportunities for various sensing applications with advantages of high signal-to-noise ratio, strong photostability, and large Stokes' shift. In this review, we will first briefly give an introduction of the AIE concept and the turn-on sensing principles. Then, we will discuss the recent examples of AIE sensors according to types of analytes. Finally, we will give a perspective on the future developments of AIE sensors. We hope this review will inspire more endeavors to devote to this emerging world.

Non-radiative decay paths in rhodamines: new theoretical insights.

PubMed

Savarese, Marika; Raucci, Umberto; Adamo, Carlo; Netti, Paolo A; Ciofini, Ilaria; Rega, Nadia

2014-10-14

We individuate a photoinduced electron transfer (PeT) as a quenching mechanism affecting rhodamine B photophysics in solvent. The PeT involves an electron transfer from the carboxylate group to the xanthene ring of rhodamine B. This is finely modulated by the subtle balance of coulombic and non-classical interactions between the carboxyphenyl and xanthene rings, also mediated by the solvent. We propose the use of an electronic density based index, the so called DCT index, as a new tool to assess and quantify the nature of the excited states involved in non-radiative decays near the region of their intersection. In the present case, this analysis allows us to gain insight on the interconversion process from the bright state to the dark state responsible for the quenching of rhodamine B fluorescence. Our findings encourage the use of density based indices to study the processes affecting excited state reactions that are characterized by a drastic change in the excitation nature, in order to rationalize the photophysical behavior of complex molecular systems.

Advancements in tailored hot stamping simulations: Cooling channel and distortion analyses

NASA Astrophysics Data System (ADS)

Billur, Eren; Wang, Chao; Bloor, Colin; Holecek, Martin; Porzner, Harald; Altan, Taylan

2013-12-01

Hot stamped components have been widely used in the automotive industry in the last decade where ultra high strength is required. These parts, however, may not provide sufficient toughness to absorb crash energy. Therefore, these components are "tailored" by controlling the microstructure at various locations. Simulation of tailored hot stamped components requires more detailed analysis of microstructural changes. Furthermore, since the part is not uniformly quenched, severe distortion can be observed. CPF, together with ESI have developed a number of techniques to predict the final properties of a tailored part. This paper discusses the recent improvements in modeling distortion and die design with cooling channels.

Molecular dynamics simulations of the structure evolutions of Cu-Zr metallic glasses under irradiation

NASA Astrophysics Data System (ADS)

Lang, Lin; Tian, Zean; Xiao, Shifang; Deng, Huiqiu; Ao, Bingyun; Chen, Piheng; Hu, Wangyu

2017-02-01

Molecular dynamics simulations have been performed to investigate the structural evolution of Cu64.5Zr35.5 metallic glasses under irradiation. The largest standard cluster analysis (LSCA) method was used to quantify the microstructure within the collision cascade regions. It is found that the majority of clusters within the collision cascade regions are full and defective icosahedrons. Not only the smaller structures (common neighbor subcluster) but also primary clusters greatly changed during the collision cascades; while most of these radiation damages self-recover quickly in the following quench states. These findings indicate the Cu-Zr metallic glasses have excellent irradiation-resistance properties.

10 CFR 434.606 - Simulation tool.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 3 2013-01-01 2013-01-01 false Simulation tool. 434.606 Section 434.606 Energy DEPARTMENT... RESIDENTIAL BUILDINGS Building Energy Compliance Alternative § 434.606 Simulation tool. 606.1 The criteria established in subsection 521 for the selection of a simulation tool shall be followed when using the...

10 CFR 434.606 - Simulation tool.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 3 2012-01-01 2012-01-01 false Simulation tool. 434.606 Section 434.606 Energy DEPARTMENT... RESIDENTIAL BUILDINGS Building Energy Compliance Alternative § 434.606 Simulation tool. 606.1 The criteria established in subsection 521 for the selection of a simulation tool shall be followed when using the...

10 CFR 434.606 - Simulation tool.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 3 2011-01-01 2011-01-01 false Simulation tool. 434.606 Section 434.606 Energy DEPARTMENT... RESIDENTIAL BUILDINGS Building Energy Compliance Alternative § 434.606 Simulation tool. 606.1 The criteria established in subsection 521 for the selection of a simulation tool shall be followed when using the...

10 CFR 434.606 - Simulation tool.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 3 2014-01-01 2014-01-01 false Simulation tool. 434.606 Section 434.606 Energy DEPARTMENT... RESIDENTIAL BUILDINGS Building Energy Compliance Alternative § 434.606 Simulation tool. 606.1 The criteria established in subsection 521 for the selection of a simulation tool shall be followed when using the...

Galaxy Zoo: the interplay of quenching mechanisms in the group environment★

NASA Astrophysics Data System (ADS)

Smethurst, R. J.; Lintott, C. J.; Bamford, S. P.; Hart, R. E.; Kruk, S. J.; Masters, K. L.; Nichol, R. C.; Simmons, B. D.

2017-08-01

Does the environment of a galaxy directly influence the quenching history of a galaxy? Here, we investigate the detailed morphological structures and star formation histories of a sample of SDSS group galaxies with both classifications from Galaxy Zoo 2 and near ultra-violet (NUV) detections in GALEX. We use the optical and NUV colours to infer the quenching time and rate describing a simple exponentially declining star formation history for each galaxy, along with a control sample of field galaxies. We find that the time since quenching and the rate of quenching do not correlate with the relative velocity of a satellite but are correlated with the group potential. This quenching occurs within an average quenching time-scale of ˜ 2.5 Gyr from star forming to complete quiescence, during an average infall time (from ˜10R200 to 0.01R200) of ˜ 2.6 Gyr. Our results suggest that the environment does play a direct role in galaxy quenching through quenching mechanisms that are correlated with the group potential, such as harassment, interactions or starvation. Environmental quenching mechanisms that are correlated with satellite velocity, such as ram-pressure stripping, are not the main cause of quenching in the group environment. We find that no single mechanism dominates over another, except in the most extreme environments or masses. Instead, an interplay of mergers, mass and morphological quenching and environment-driven quenching mechanisms dependent on the group potential drive galaxy evolution in groups.

Galaxy Zoo: Major Galaxy Mergers Are Not a Significant Quenching Pathway

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Schawinski, Kevin; Caplar, Neven; Carpineti, Alfredo; Hart, Ross E.; Kaviraj, Sugata; Keel, William C.; Kruk, Sandor J.; Lintott, Chris J.; Nichol, Robert C.; Simmons, Brooke D.; Smethurst, Rebecca J.

2017-08-01

We use stellar mass functions to study the properties and the significance of quenching through major galaxy mergers. In addition to SDSS DR7 and Galaxy Zoo 1 data, we use samples of visually selected major galaxy mergers and post-merger galaxies. We determine the stellar mass functions of the stages that we would expect major-merger-quenched galaxies to pass through on their way from the blue cloud to the red sequence: (1) major merger, (2) post-merger, (3) blue early type, (4) green early type, and (5) red early type. Based on their similar mass function shapes, we conclude that major mergers are likely to form an evolutionary sequence from star formation to quiescence via quenching. Relative to all blue galaxies, the major-merger fraction increases as a function of stellar mass. Major-merger quenching is inconsistent with the mass and environment quenching model. At z˜ 0, major-merger-quenched galaxies are unlikely to constitute the majority of galaxies that transition through the green valley. Furthermore, between z˜ 0-0.5, major-merger-quenched galaxies account for 1%-5% of all quenched galaxies at a given stellar mass. Major galaxy mergers are therefore not a significant quenching pathway, neither at z˜ 0 nor within the last 5 Gyr. The majority of red galaxies must have been quenched through an alternative quenching mechanism that causes a slow blue to red evolution. .

40 CFR 63.7295 - What requirements must I meet for quenching?

Code of Federal Regulations, 2010 CFR

2010-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and... each quench tower and backup quench station at a new or existing coke oven battery. (1) For the quenching of hot coke, you must meet the requirements in paragraph (a)(1)(i) or (ii) of this section. (i...

40 CFR 63.7295 - What requirements must I meet for quenching?

Code of Federal Regulations, 2011 CFR

2011-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and... each quench tower and backup quench station at a new or existing coke oven battery. (1) For the quenching of hot coke, you must meet the requirements in paragraph (a)(1)(i) or (ii) of this section. (i...

40 CFR 63.7295 - What requirements must I meet for quenching?

Code of Federal Regulations, 2013 CFR

2013-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and... each quench tower and backup quench station at a new or existing coke oven battery. (1) For the quenching of hot coke, you must meet the requirements in paragraph (a)(1)(i) or (ii) of this section. (i...

40 CFR 63.7295 - What requirements must I meet for quenching?

Code of Federal Regulations, 2014 CFR

2014-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and... each quench tower and backup quench station at a new or existing coke oven battery. (1) For the quenching of hot coke, you must meet the requirements in paragraph (a)(1)(i) or (ii) of this section. (i...

40 CFR 63.7295 - What requirements must I meet for quenching?

Code of Federal Regulations, 2012 CFR

2012-07-01

... (CONTINUED) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and... each quench tower and backup quench station at a new or existing coke oven battery. (1) For the quenching of hot coke, you must meet the requirements in paragraph (a)(1)(i) or (ii) of this section. (i...

Characterization of plasma current quench during disruptions at HL-2A

NASA Astrophysics Data System (ADS)

Zhu, Jinxia; Zhang, Yipo; Dong, Yunbo; HL-2A Team

2017-05-01

The most essential assumptions of physics for the evaluation of electromagnetic forces on the plasma-facing components due to a disruption-induced eddy current are characteristics of plasma current quenches including the current quench rate or its waveforms. The characteristics of plasma current quenches at HL-2A have been analyzed during spontaneous disruptions. Both linear decay and exponential decay are found in the disruptions with the fastest current quenches. However, there are two stages of current quench in the slow current quench case. The first stage with an exponential decay and the second stage followed by a rapid linear decay. The faster current quench rate corresponds to the faster movement of plasma displacement. The parameter regimes on the current quench time and the current quench rates have been obtained from disruption statistics at HL-2A. There exists no remarkable difference for distributions obtained between the limiter and the divertor configuration. This data from HL-2A provides basic data of the derivation of design criteria for a large-sized machine during the current decay phase of the disruptions.

Novel water-air circulation quenching process for AISI 4140 steel

NASA Astrophysics Data System (ADS)

Zheng, Liyun; Zheng, Dawei; Zhao, Lixin; Wang, Lihui; Zhang, Kai

2013-11-01

AISI 4140 steel is usually used after quenching and tempering. During the heat treatment process in industry production, there are some problems, such as quenching cracks, related to water-cooling and low hardness due to oil quenching. A water-air circulation quenching process can solve the problems of quenching cracks with water and the high cost quenching with oil, which is flammable, unsafe and not enough to obtain the required hardness. The control of the water-cooling and air-cooling time is a key factor in the process. This paper focuses on the quenching temperature, water-air cycle time and cycle index to prevent cracking for AISI 4140 steel. The optimum heat treatment parameters to achieve a good match of the strength and toughness of AISI 4140 steel were obtained by repeated adjustment of the water-air circulation quenching process parameters. The tensile strength, Charpy impact energy at -10 °C and hardness of the heat treated AISI 4140 steel after quenching and tempering were approximately 1098 MPa, 67.5 J and 316 HB, respectively.

Predictive Model and Methodology for Heat Treatment Distortion Final Report CRADA No. TC-298-92

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nikkel, D. J.; McCabe, J.

This project was a multi-lab, multi-partner CRADA involving LLNL, Los Alamos National Laboratory, Sandia National Laboratories, Oak Ridge National Laboratory, Martin Marietta Energy Systems and the industrial partner, The National Center of Manufacturing Sciences (NCMS). A number of member companies of NCMS participated including General Motors Corporation, Ford Motor Company, The Torrington Company, Gear Research, the Illinois Institute of Technology Research Institute, and Deformation Control Technology •. LLNL was the lead laboratory for metrology technology used for validation of the computational tool/methodology. LLNL was also the lead laboratory for the development of the software user interface , for the computationalmore » tool. This report focuses on the participation of LLNL and NCMS. The purpose of the project was to develop a computational tool/methodology that engineers would use to predict the effects of heat treatment on the _size and shape of industrial parts made of quench hardenable alloys. Initially, the target application of the tool was gears for automotive power trains.« less

Pre-recombination quenching of the radiation induced fluorescence as the approach to study kinetics of ion-molecular reactions

NASA Astrophysics Data System (ADS)

Borovkov, V. I.; Ivanishko, I. S.

2011-04-01

This study deals with the geminate ion recombination in the presence of bulk scavengers, that is the so-called scavenger problem, as well as with the effect of the scavenging reaction on the radiation-induced recombination fluorescence. Borovkov and Velizhanin (2004) have proposed a method to determine the rate constant of the bulk reaction between neutral scavengers and one of the geminate ions if the ion-molecular reaction prevented the formation of electronically excited states upon recombination involving a newly formed ion. If such pre-recombination quenching of the radiation-induced fluorescence took place, it manifested itself as a progressive decrease in the decay of the fluorescence intensity. The relative change in the fluorescence decay as caused by the scavengers was believed to be closely related to the kinetics of the scavenging reaction. The goal of the present study is to support this method, both computationally and experimentally because there are two factors, which cast doubt on the intuitively obvious approach to the scavenger problem: spatial correlations between the particles involved and the drift of the charged reagent in the electric field of its geminate partner. Computer simulation of geminate ions recombination with an explicit modeling of the motion trajectories of scavengers has been performed for media of low dielectric permittivity, i.e. for the maximal Coulomb interaction between the ions. The simulation has shown that upon continuous diffusion of the particles involved, the joint effect of the two above factors can be considered as insignificant with a high accuracy. Besides, it is concluded then that the method of pre-recombination quenching could be applied to study parallel and consecutive reactions where the yields of excited states in the reaction pathways are different with the use of very simple analytical relations of the formal chemical kinetics. The conclusion has been confirmed experimentally by the example of the reactions of electron transfer from the diphenylacetylene radical anion to dibromoethane and hexafluorobenzene in n-dodecane solutions.

Box simulations of rotating magnetoconvection. Effects of penetration and turbulent pumping

NASA Astrophysics Data System (ADS)

Ziegler, U.; Rüdiger, G.

2003-04-01

Various effects of penetration in rotating magnetoconvection are studied by means of three-dimensional numerical simulations employing the code NIRVANA. A local, 2-layer model is applied dividing the computational domain (which is a rectangular box placed tangentially on a sphere at latitude 45deg) in an unstable polytropic region on top of a stable polytropic region. Different realizations of convection are examined parameterized by Taylor numbers Ta=0,6 x 104, 6x 105 and magnetic field strengths β = 5,50,500,5000,infty . We find a rather distinctive behavior of the penetration depth Delta on the system parameters (Ta,β). In non-rotating convection Delta is a monotonically decreasing function of β-1 which is due to magnetic quenching effects. Also, penetration is subject to rotational quenching, i.e. Delta is reduced for increasing rotation rate. In the intermediate regime of (Ta,β), the effects of rotation and magnetic field on Delta do not simply add (see Fig. 3). We find, nevertheless, a very strong reduction of the penetration depth of overshooting turbulence by both rotation and magnetism. Penetrative convection is closely associated with the mixing of a passive scalar quantity advected with the flow. In the long term, the tracer material penetrates significantly deeper into the stable layer than suggested by Delta which is due to the cumulative effect of isolated, fast-moving plumes. In case of a weak magnetic field, penetrative convection also serves to ensure a downward transport of magnetic flux by turbulent pumping with an average rate gammaz ~ -7x 10-3 measured in units of the sound speed at the top z-boundary. For larger magnetic fields the pumping effect is quenched and even changes sign in the convection zone. This effect is suggested as being due to the effect of ``turbulent buoyancy'' which in density-stratified media transports a given magnetic field upwards if it is not too strong (Kichatinov & Rüdiger \\cite{Kichatinov92}).

Mechanism of Interaction between the General Anesthetic Halothane and a Model Ion Channel Protein, II: Fluorescence and Vibrational Spectroscopy Using a Cyanophenylalanine Probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, J.; Strzalka, J; Tronin, A

2009-01-01

We demonstrate that cyano-phenylalanine (PheCN) can be utilized to probe the binding of the inhalational anesthetic halothane to an anesthetic-binding, model ion channel protein hbAP-PheCN. The Trp to PheCN mutation alters neither the a-helical conformation nor the 4-helix bundle structure. The halothane binding properties of this PheCN mutant hbAP-PheCN, based on fluorescence quenching, are consistent with those of the prototype, hbAP1. The dependence of fluorescence lifetime as a function of halothane concentration implies that the diffusion of halothane in the nonpolar core of the protein bundle is one-dimensional. As a consequence, at low halothane concentrations, the quenching of the fluorescencemore » is dynamic, whereas at high concentrations the quenching becomes static. The 4-helix bundle structure present in aqueous detergent solution and at the air-water interface, is preserved in multilayer films of hbAP-PheCN, enabling vibrational spectroscopy of both the protein and its nitrile label (-CN). The nitrile groups' stretching vibration band shifts to higher frequency in the presence of halothane, and this blue-shift is largely reversible. Due to the complexity of this amphiphilic 4-helix bundle model membrane protein, where four PheCN probes are present adjacent to the designed cavity forming the binding site within each bundle, all contributing to the infrared absorption, molecular dynamics (MD) simulation is required to interpret the infrared results. The MD simulations indicate that the blue-shift of -CN stretching vibration induced by halothane arises from an indirect effect, namely an induced change in the electrostatic protein environment averaged over the four probe oscillators, rather than a direct interaction with the oscillators. hbAP-PheCN therefore provides a successful template for extending these investigations of the interactions of halothane with the model membrane protein via vibrational spectroscopy, using cyano-alanine residues to form the anesthetic binding cavity.« less

A diffusion-limited reaction model for self-propagating Al/Pt multilayers with quench limits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kittell, David E.; Yarrington, Cole D.; Hobbs, M. L.

A diffusion-limited reaction model was calibrated for Al/Pt multilayers ignited on oxidized silicon, sapphire, and tungsten substrates, as well as for some Al/Pt multilayers ignited as free-standing foils. The model was implemented in a finite element analysis code and used to match experimental burn front velocity data collected from several years of testing at Sandia National Laboratories. Moreover, both the simulations and experiments reveal well-defined quench limits in the total Al + Pt layer (i.e., bilayer) thickness. At these limits, the heat generated from atomic diffusion is insufficient to support a self-propagating wave front on top of the substrates. Quenchmore » limits for reactive multilayers are seldom reported and are found to depend on the thermal properties of the individual layers. Here, the diffusion-limited reaction model is generalized to allow for temperature- and composition-dependent material properties, phase change, and anisotropic thermal conductivity. Utilizing this increase in model fidelity, excellent overall agreement is shown between the simulations and experimental results with a single calibrated parameter set. However, the burn front velocities of Al/Pt multilayers ignited on tungsten substrates are over-predicted. Finally, possible sources of error are discussed and a higher activation energy (from 41.9 kJ/mol.at. to 47.5 kJ/mol.at.) is shown to bring the simulations into agreement with the velocity data observed on tungsten substrates. Finally, this higher activation energy suggests an inhibited diffusion mechanism present at lower heating rates.« less

A diffusion-limited reaction model for self-propagating Al/Pt multilayers with quench limits

DOE PAGES

Kittell, David E.; Yarrington, Cole D.; Hobbs, M. L.; ...

2018-04-14

A diffusion-limited reaction model was calibrated for Al/Pt multilayers ignited on oxidized silicon, sapphire, and tungsten substrates, as well as for some Al/Pt multilayers ignited as free-standing foils. The model was implemented in a finite element analysis code and used to match experimental burn front velocity data collected from several years of testing at Sandia National Laboratories. Moreover, both the simulations and experiments reveal well-defined quench limits in the total Al + Pt layer (i.e., bilayer) thickness. At these limits, the heat generated from atomic diffusion is insufficient to support a self-propagating wave front on top of the substrates. Quenchmore » limits for reactive multilayers are seldom reported and are found to depend on the thermal properties of the individual layers. Here, the diffusion-limited reaction model is generalized to allow for temperature- and composition-dependent material properties, phase change, and anisotropic thermal conductivity. Utilizing this increase in model fidelity, excellent overall agreement is shown between the simulations and experimental results with a single calibrated parameter set. However, the burn front velocities of Al/Pt multilayers ignited on tungsten substrates are over-predicted. Finally, possible sources of error are discussed and a higher activation energy (from 41.9 kJ/mol.at. to 47.5 kJ/mol.at.) is shown to bring the simulations into agreement with the velocity data observed on tungsten substrates. Finally, this higher activation energy suggests an inhibited diffusion mechanism present at lower heating rates.« less

Artificial magnetic-field quenches in synthetic dimensions

NASA Astrophysics Data System (ADS)

Yılmaz, F.; Oktel, M. Ö.

2018-02-01

Recent cold atom experiments have realized models where each hyperfine state at an optical lattice site can be regarded as a separate site in a synthetic dimension. In such synthetic ribbon configurations, manipulation of the transitions between the hyperfine levels provide direct control of the hopping in the synthetic dimension. This effect was used to simulate a magnetic field through the ribbon. Precise control over the hopping matrix elements in the synthetic dimension makes it possible to change this artificial magnetic field much faster than the time scales associated with atomic motion in the lattice. In this paper, we consider such a magnetic-flux quench scenario in synthetic dimensions. Sudden changes have not been considered for real magnetic fields as such changes in a conducting system would result in large induced currents. Hence we first study the difference between a time varying real magnetic field and an artificial magnetic field using a minimal six-site model. This minimal model clearly shows the connection between gauge dependence and the lack of on-site induced scalar potential terms. We then investigate the dynamics of a wave packet in an infinite two- or three-leg ladder following a flux quench and find that the gauge choice has a dramatic effect on the packet dynamics. Specifically, a wave packet splits into a number of smaller packets moving with different velocities. Both the weights and the number of packets depend on the implemented gauge. If an initial packet, prepared under zero flux in an n -leg ladder, is quenched to Hamiltonian with a vector potential parallel to the ladder, it splits into at most n smaller wave packets. The same initial wave packet splits into up to n2 packets if the vector potential is implemented to be along the rungs. Even a trivial difference in the gauge choice such as the addition of a constant to the vector potential produces observable effects. We also calculate the packet weights for arbitrary initial and final fluxes. Finally, we show that edge states in a thick ribbon are robust under the quench only when the same gap supports an edge state for the final Hamiltonian.

The mass dependence of satellite quenching in Milky Way-like haloes

NASA Astrophysics Data System (ADS)

Phillips, John I.; Wheeler, Coral; Cooper, Michael C.; Boylan-Kolchin, Michael; Bullock, James S.; Tollerud, Erik

2015-02-01

Using the Sloan Digital Sky Survey, we examine the quenching of satellite galaxies around isolated Milky Way-like hosts in the local Universe. We find that the efficiency of satellite quenching around isolated galaxies is low and roughly constant over two orders of magnitude in satellite stellar mass (M⋆ = 108.5-1010.5 M⊙), with only ˜20 per cent of systems quenched as a result of environmental processes. While largely independent of satellite stellar mass, satellite quenching does exhibit clear dependence on the properties of the host. We show that satellites of passive hosts are substantially more likely to be quenched than those of star-forming hosts, and we present evidence that more massive haloes quench their satellites more efficiently. These results extend trends seen previously in more massive host haloes and for higher satellite masses. Taken together, it appears that galaxies with stellar masses larger than about 108 M⊙ are uniformly resistant to environmental quenching, with the relative harshness of the host environment likely serving as the primary driver of satellite quenching. At lower stellar masses (<108 M⊙), however, observations of the Local Group suggest that the vast majority of satellite galaxies are quenched, potentially pointing towards a characteristic satellite mass scale below which quenching efficiency increases dramatically.

Secondary Heating Under Quenching Cooling of Aluminum Alloys

NASA Astrophysics Data System (ADS)

Tsukrov, S. L.; Ber, L. B.

2017-07-01

Variants of secondary heating of aluminum alloys are considered, i.e., under quenching of plates in a water tank or on a horizontal quenching unit with water jet cooling, under continuous quenching of strips, and under quenching of tubes in vertical furnaces. Recommendation are given for removal or substantial reduction of the intensity of secondary heating under industrial conditions.

NBS: Nondestructive evaluation of nonuniformities in 2219 aluminum alloy plate: Relationship to processing

NASA Technical Reports Server (NTRS)

Swartzendruber, L.; Boettinger, W.; Ives, L.; Coriell, S.; Ballard, D.; Laughlin, D.; Clough, R.; Biancanieilo, F.; Blau, P.; Cahn, J.

1980-01-01

The compositional homogeneity, microstructure, hardness, electrical conductivity and mechanical properties of 2219 aluminum alloy plates are influenced by the process variables during casting, rolling and thermomechanical treatment. The details of these relationships wre investigated for correctly processed 2219 plate as well as for deviations caused by improper quenching after solution heat treatment. Primary emphasis was been placed on the reliability of eddy current electrical conductivity and hardness as NDE tools to detect variations in mechanical properties.

Initial state nuclear effects for jet production measured in s=200GeV d+Au collisions by STAR

NASA Astrophysics Data System (ADS)

STAR Collaboration; Kapitán, Jan; STAR Collaboration

2009-11-01

Full jet reconstruction in heavy-ion collisions is a promising tool for quantitative study of properties of the dense medium produced at RHIC. Measurements of d+Au collisions are important to disentangle initial state nuclear effects from medium-induced k broadening and jet quenching. We report measurements of mid-rapidity (|η|<0.4|) di-jet correlations in d+Au using high-statistics run 8 RHIC data at s=200GeV.

PEGylated substrates of NSP4 protease: A tool to study protease specificity

NASA Astrophysics Data System (ADS)

Wysocka, Magdalena; Gruba, Natalia; Grzywa, Renata; Giełdoń, Artur; Bąchor, Remigiusz; Brzozowski, Krzysztof; Sieńczyk, Marcin; Dieter, Jenne; Szewczuk, Zbigniew; Rolka, Krzysztof; Lesner, Adam

2016-03-01

Herein we present the synthesis of a novel type of peptidomimetics composed of repeating diaminopropionic acid residues modified with structurally diverse heterobifunctional polyethylene glycol chains (abbreviated as DAPEG). Based on the developed compounds, a library of fluorogenic substrates was synthesized. Further library deconvolution towards human neutrophil serine protease 4 (NSP4) yielded highly sensitive and selective internally quenched peptidomimetic substrates. In silico analysis of the obtained peptidomimetics revealed the presence of an interaction network with distant subsites located on the enzyme surface.

MSFC Electrostatic Levitator (ESL) Rapid Quench System

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Craven, Paul D.; Rogers, Jan R.

2014-01-01

The NASA Marshall Space Flight Center (MSFC) Electrostatic Levitator (ESL) Laboratory is a unique facility for investigators studying high-temperature materials. The laboratory boasts two levitators in which samples can be levitated, heated, melted, undercooled, and resolidified, all without the interference of a container or data-gathering instrument. The ESL main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy. Thereby allowing rapid quenching of undercooled liquid metals. Up to 8 quench vessels can be loaded into the quench wheel, which is indexed with LabVIEW control software. This allows up to 8 samples to be rapidly quenched before having to open the chamber. The system has been tested successfully on several zirconium samples. Future work will be done with other materials using different quench mediums. Microstructural analysis will also be done on successfully quench samples.

Defect-Induced Luminescence Quenching vs. Charge Carrier Generation of Phosphorus Incorporated in Silicon Nanocrystals as Function of Size.

PubMed

Hiller, Daniel; López-Vidrier, Julian; Gutsch, Sebastian; Zacharias, Margit; Nomoto, Keita; König, Dirk

2017-04-13

Phosphorus doping of silicon nanostructures is a non-trivial task due to problems with confinement, self-purification and statistics of small numbers. Although P-atoms incorporated in Si nanostructures influence their optical and electrical properties, the existence of free majority carriers, as required to control electronic properties, is controversial. Here, we correlate structural, optical and electrical results of size-controlled, P-incorporating Si nanocrystals with simulation data to address the role of interstitial and substitutional P-atoms. Whereas atom probe tomography proves that P-incorporation scales with nanocrystal size, luminescence spectra indicate that even nanocrystals with several P-atoms still emit light. Current-voltage measurements demonstrate that majority carriers must be generated by field emission to overcome the P-ionization energies of 110-260 meV. In absence of electrical fields at room temperature, no significant free carrier densities are present, which disproves the concept of luminescence quenching via Auger recombination. Instead, we propose non-radiative recombination via interstitial-P induced states as quenching mechanism. Since only substitutional-P provides occupied states near the Si conduction band, we use the electrically measured carrier density to derive formation energies of ~400 meV for P-atoms on Si nanocrystal lattice sites. Based on these results we conclude that ultrasmall Si nanovolumes cannot be efficiently P-doped.

Up and Down Quark Masses and Corrections to Dashen's Theorem from Lattice QCD and Quenched QED.

PubMed

Fodor, Z; Hoelbling, C; Krieg, S; Lellouch, L; Lippert, Th; Portelli, A; Sastre, A; Szabo, K K; Varnhorst, L

2016-08-19

In a previous Letter [Borsanyi et al., Phys. Rev. Lett. 111, 252001 (2013)] we determined the isospin mass splittings of the baryon octet from a lattice calculation based on N_{f}=2+1 QCD simulations to which QED effects have been added in a partially quenched setup. Using the same data we determine here the corrections to Dashen's theorem and the individual up and down quark masses. Our ensembles include 5 lattice spacings down to 0.054 fm, lattice sizes up to 6 fm, and average up-down quark masses all the way down to their physical value. For the parameter which quantifies violations to Dashen's theorem, we obtain ϵ=0.73(2)(5)(17), where the first error is statistical, the second is systematic, and the third is an estimate of the QED quenching error. For the light quark masses we obtain, m_{u}=2.27(6)(5)(4) and m_{d}=4.67(6)(5)(4)  MeV in the modified minimal subtraction scheme at 2  GeV and the isospin breaking ratios m_{u}/m_{d}=0.485(11)(8)(14), R=38.2(1.1)(0.8)(1.4), and Q=23.4(0.4)(0.3)(0.4). Our results exclude the m_{u}=0 solution to the strong CP problem by more than 24 standard deviations.

Gas Loss by Ram Pressure Stripping and Internal Feedback from Low-mass Milky Way Satellites

NASA Astrophysics Data System (ADS)

Emerick, Andrew; Mac Low, Mordecai-Mark; Grcevich, Jana; Gatto, Andrea

2016-08-01

The evolution of dwarf satellites in the Milky Way (MW) is affected by a combination of ram pressure stripping (RPS), tidal stripping, and internal feedback from massive stars. We investigate gas loss processes in the smallest satellites of the MW using three-dimensional, high-resolution, idealized wind tunnel simulations, accounting for gas loss through both ram pressure stripping and expulsion by supernova feedback. Using initial conditions appropriate for a dwarf galaxy like Leo T, we investigate whether or not environmental gas stripping and internal feedback can quench these low-mass galaxies on the expected timescales, shorter than 2 Gyr. We find that supernova feedback contributes negligibly to the stripping rate for these low star formation rate galaxies. However, we also find that RPS is less efficient than expected in the stripping scenarios we consider. Our work suggests that although RPS can eventually completely strip these galaxies, other physics is likely at play to reconcile our computed stripping times with the rapid quenching timescales deduced from observations of low-mass MW dwarf galaxies. We discuss the roles additional physics may play in this scenario, including host-satellite tidal interactions, cored versus cuspy dark matter profiles, reionization, and satellite preprocessing. We conclude that a proper accounting of these physics together is necessary to understand the quenching of low-mass MW satellites.

GAS LOSS BY RAM PRESSURE STRIPPING AND INTERNAL FEEDBACK FROM LOW-MASS MILKY WAY SATELLITES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Emerick, Andrew; Low, Mordecai-Mark Mac; Grcevich, Jana

The evolution of dwarf satellites in the Milky Way (MW) is affected by a combination of ram pressure stripping (RPS), tidal stripping, and internal feedback from massive stars. We investigate gas loss processes in the smallest satellites of the MW using three-dimensional, high-resolution, idealized wind tunnel simulations, accounting for gas loss through both ram pressure stripping and expulsion by supernova feedback. Using initial conditions appropriate for a dwarf galaxy like Leo T, we investigate whether or not environmental gas stripping and internal feedback can quench these low-mass galaxies on the expected timescales, shorter than 2 Gyr. We find that supernovamore » feedback contributes negligibly to the stripping rate for these low star formation rate galaxies. However, we also find that RPS is less efficient than expected in the stripping scenarios we consider. Our work suggests that although RPS can eventually completely strip these galaxies, other physics is likely at play to reconcile our computed stripping times with the rapid quenching timescales deduced from observations of low-mass MW dwarf galaxies. We discuss the roles additional physics may play in this scenario, including host-satellite tidal interactions, cored versus cuspy dark matter profiles, reionization, and satellite preprocessing. We conclude that a proper accounting of these physics together is necessary to understand the quenching of low-mass MW satellites.« less

Spectroscopic studies on the interaction of fluorescein and safranine T in PC liposomes

NASA Astrophysics Data System (ADS)

Bozkurt, Ebru; Bayraktutan, Tuğba; Acar, Murat; Toprak, Mahmut

2013-01-01

In this study, the fluorescence quenching of fluorescein by safranine T in liposome media had been investigated systematically by fluorescence spectroscopy, UV-vis absorption spectroscopy and fluorescence decay lifetime measurements. The spectroscopic data were analyzed using a Stern-Volmer equation to determine the quenching process. The experimental results showed that the intrinsic fluorescence of fluorescein was strongly quenched by safranine T, and that the quenching mechanism was considered as static quenching by forming a ground-complex. The Stern-Volmer quenching constant Ksv, and the bimolecular quenching constant Kq were estimated. The distances between the donor (fluorescein) and the acceptor (safranine T) were calculated according to the Förster non-radiation energy transfer theory. In addition, the partition coefficient of the safranine T (Kp) in the L-egg lecithin phosphatidylcholine liposomes was also calculated by utilizing the fluorescence quenching.

An approach to value-based simulator selection: The creation and evaluation of the simulator value index tool.

PubMed

Rooney, Deborah M; Hananel, David M; Covington, Benjamin J; Dionise, Patrick L; Nykamp, Michael T; Pederson, Melvin; Sahloul, Jamal M; Vasquez, Rachael; Seagull, F Jacob; Pinsky, Harold M; Sweier, Domenica G; Cooke, James M

2018-04-01

Currently there is no reliable, standardized mechanism to support health care professionals during the evaluation of and procurement processes for simulators. A tool founded on best practices could facilitate simulator purchase processes. In a 3-phase process, we identified top factors considered during the simulator purchase process through expert consensus (n = 127), created the Simulator Value Index (SVI) tool, evaluated targeted validity evidence, and evaluated the practical value of this SVI. A web-based survey was sent to simulation professionals. Participants (n = 79) used the SVI and provided feedback. We evaluated the practical value of 4 tool variations by calculating their sensitivity to predict a preferred simulator. Seventeen top factors were identified and ranked. The top 2 were technical stability/reliability of the simulator and customer service, with no practical differences in rank across institution or stakeholder role. Full SVI variations predicted successfully the preferred simulator with good (87%) sensitivity, whereas the sensitivity of variations in cost and customer service and cost and technical stability decreased (≤54%). The majority (73%) of participants agreed that the SVI was helpful at guiding simulator purchase decisions, and 88% agreed the SVI tool would help facilitate discussion with peers and leadership. Our findings indicate the SVI supports the process of simulator purchase using a standardized framework. Sensitivity of the tool improved when factors extend beyond traditionally targeted factors. We propose the tool will facilitate discussion amongst simulation professionals dealing with simulation, provide essential information for finance and procurement professionals, and improve the long-term value of simulation solutions. Limitations and application of the tool are discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

Review of thermo-physical properties, wetting and heat transfer characteristics of nanofluids and their applicability in industrial quench heat treatment

PubMed Central

2011-01-01

The success of quenching process during industrial heat treatment mainly depends on the heat transfer characteristics of the quenching medium. In the case of quenching, the scope for redesigning the system or operational parameters for enhancing the heat transfer is very much limited and the emphasis should be on designing quench media with enhanced heat transfer characteristics. Recent studies on nanofluids have shown that these fluids offer improved wetting and heat transfer characteristics. Further water-based nanofluids are environment friendly as compared to mineral oil quench media. These potential advantages have led to the development of nanofluid-based quench media for heat treatment practices. In this article, thermo-physical properties, wetting and boiling heat transfer characteristics of nanofluids are reviewed and discussed. The unique thermal and heat transfer characteristics of nanofluids would be extremely useful for exploiting them as quench media for industrial heat treatment. PMID:21711877

Review of thermo-physical properties, wetting and heat transfer characteristics of nanofluids and their applicability in industrial quench heat treatment.

PubMed

Ramesh, Gopalan; Prabhu, Narayan Kotekar

2011-04-14

The success of quenching process during industrial heat treatment mainly depends on the heat transfer characteristics of the quenching medium. In the case of quenching, the scope for redesigning the system or operational parameters for enhancing the heat transfer is very much limited and the emphasis should be on designing quench media with enhanced heat transfer characteristics. Recent studies on nanofluids have shown that these fluids offer improved wetting and heat transfer characteristics. Further water-based nanofluids are environment friendly as compared to mineral oil quench media. These potential advantages have led to the development of nanofluid-based quench media for heat treatment practices. In this article, thermo-physical properties, wetting and boiling heat transfer characteristics of nanofluids are reviewed and discussed. The unique thermal and heat transfer characteristics of nanofluids would be extremely useful for exploiting them as quench media for industrial heat treatment.

Partitioning of 2,6-Bis(1H-Benzimidazol-2-yl)pyridine Fluorophore into a Phospholipid Bilayer: Complementary Use of Fluorescence Quenching Studies and Molecular Dynamics Simulations

PubMed Central

Kyrychenko, Alexander; Sevriukov, Igor Yu.; Syzova, Zoya A.; Ladokhin, Alexey S.; Doroshenko, Andrey O.

2014-01-01

Successful use of fluorescence sensing in elucidating the biophysical properties of lipid membranes requires knowledge of the distribution and location of an emitting molecule in the bilayer. We report here that 2,6-bis(1H-benzimidazol-2-yl)pyridine (BBP), which is almost non-fluorescent in aqueous solutions, reveals a strong emission enhancement in a hydrophobic environment of a phospholipid bilayer, making it interesting for fluorescence probing of water content in a lipid membrane. Comparing the fluorescence behavior of BBP in a wide variety of solvents with those in phospholipid vesicles, we suggest that the hydrogen bonding interactions between a BBP fluorophore and water molecules play a crucial role in the observed “light switch effect”. Therefore, the loss of water-induced fluorescence quenching inside a membrane are thought to be due to deep penetration of BBP into the hydrophobic, water-free region of a bilayer. Characterized by strong quenching by transition metal ions in solution, BBP also demonstrated significant shielding from the action of the quencher in the presence of phospholipid vesicles. We used the increase in fluorescence intensity, measured upon titration of probe molecules with lipid vesicles, to estimate the partition constant and the Gibbs free energy (ΔG) of transfer of BBP from aqueous buffer into a membrane. Partitioning BBP revealed strongly favorable ΔG, which depends only slightly on the lipid composition of a bilayer, varying in a range from -6.5 to -7.0 kcal/mol. To elucidate the binding interactions of the probe with a membrane on the molecular level, a distribution and favorable location of BBP in a POPC bilayer were modeled via atomistic molecular dynamics (MD) simulations using two different approaches: (i) free, diffusion-driven partitioning of the probe molecules into a bilayer and (ii) constrained umbrella sampling of a penetration profile of the dye molecule across a bilayer. Both of these MD approaches agreed with regard to the preferred location of a BBP fluorophore within the interfacial region of a bilayer, located between the hydrocarbon acyl tails and the initial portion of the lipid headgroups. MD simulations also revealed restricted permeability of water molecules into this region of a POPC bilayer, determining the strong fluorescence enhancement observed experimentally for the membrane-partitioned form of BBP. PMID:21211898

Preparation and Preliminary Characterization of Crystallizing Fluorescent Derivatives of Chicken Egg White Lysozyme

NASA Technical Reports Server (NTRS)

Sumida, John; Forsythe, Elizabeth L.; Pusey, Marc L.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow and 5-(2-aminoethyl)aminonapthalene-1-sulfonic acid (EDANS) have been attached to the side chain carboxyl of Asp(sup 101) using a carbodiimide coupling procedure. Asp(sup 101) lies within the active site cleft, and it is believed that the probes are "buried" within that cleft. Lucifer yellow and MANS probes with iodoacetamide reactive groups have been bound to His(sup 15), located on the "back side" of the molecule relative to the active site. All the derivatives fluoresce in the solution and the crystalline states. Fluorescence characterization has focused on determination of binding effects on the probe quantum yield, lifetime, absorption and emission spectra, and quenching by added solutes. Quenching studies show that, as postulated, the Asp(sup 101)-bound probes are partially sheltered from the bulk solution by their location within the active site cleft. Probes bound to His(sup 15) have quenching constants about equal to those for the free probes, indicating that this site is highly exposed to the bulk solution.

Preparation and Preliminary Characterization of Crystallizing Fluorescent Derivatives of Chicken Egg White Lysozyme

NASA Technical Reports Server (NTRS)

Sumida, John P.; Forsythe, Elizabeth L.; Pusey, Marc L.

2001-01-01

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. While most proteins are intrinsically fluorescent, working at crystallization concentrations require the use of covalently prepared derivatives added as tracers. This approach requires derivatives that do not markedly affect the crystal packing. We have prepared fluorescent derivatives of chicken egg white lysozyme with probes bound to one of two different sites on the protein molecule. Lucifer yellow and 5-(2-aminoethyl)aminonapthalene-i-sulfonic acid (EDANS) have been attached to the side chain carboxyl of Asp(sup 101) using a carbodiimide coupling procedure. Asp(sup 101) lies within the active site cleft, and it is believed that the probes are 'buried' within that cleft. Lucifer yellow and MANS probes with iodoacetamide reactive five groups have been bound to His(sup 15), located on the 'back side' of the molecule relative to the active site. All the derivatives fluoresce in the solution and the crystalline states. Fluorescence characterization has focused on determination of binding effects on the probe quantum yield, lifetime, absorption and emission spectra, and quenching by added solutes. Quenching studies show that, as postulated, the Asp(sup 101)-bound probes are partially sheltered from the bulk solution by their location within the active site cleft. Probes bound to His(sup 15) have quenching constants about equal to those for the free probes, indicating that this site is highly exposed to the bulk solution.

Structural and biochemical characterization of AidC, a quorum-quenching lactonase with atypical selectivity

DOE PAGES

Mascarenhas, Romila; Thomas, Pei W.; Wu, Chun -Xiang; ...

2015-06-26

Quorum-quenching catalysts are of interest for potential application as biochemical tools for interrogating interbacterial communication pathways, as antibiofouling agents, and as anti-infective agents in plants and animals. Herein, the structure and function of AidC, an N-acyl-l-homoserine lactone (AHL) lactonase from Chryseobacterium, is characterized. Steady-state kinetics show that zinc-supplemented AidC is the most efficient wild-type quorum-quenching enzymes characterized to date, with a k cat/K M value of approximately 2 × 10 6 M -1 s -1 for N-heptanoyl-l-homoserine lactone. The enzyme has stricter substrate selectivity and significantly lower KM values (ca. 50 μM for preferred substrates) compared to those of typicalmore » AHL lactonases (ca. >1 mM). X-ray crystal structures of AidC alone and with the product N-hexanoyl-l-homoserine were determined at resolutions of 1.09 and 1.67 Å, respectively. Each structure displays as a dimer, and dimeric oligiomerization was also observed in solution by size-exclusion chromatography coupled with multiangle light scattering. Lastly, the structures reveal two atypical features as compared to previously characterized AHL lactonases: a "kinked" α-helix that forms part of a closed binding pocket that provides affinity and enforces selectivity for AHL substrates and an active-site His substitution that is usually found in a homologous family of phosphodiesterases. We discuss implications for the catalytic mechanism of AHL lactonases.« less

Structural and biochemical characterization of AidC, a quorum-quenching lactonase with atypical selectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mascarenhas, Romila; Thomas, Pei W.; Wu, Chun -Xiang

Quorum-quenching catalysts are of interest for potential application as biochemical tools for interrogating interbacterial communication pathways, as antibiofouling agents, and as anti-infective agents in plants and animals. Herein, the structure and function of AidC, an N-acyl-l-homoserine lactone (AHL) lactonase from Chryseobacterium, is characterized. Steady-state kinetics show that zinc-supplemented AidC is the most efficient wild-type quorum-quenching enzymes characterized to date, with a k cat/K M value of approximately 2 × 10 6 M -1 s -1 for N-heptanoyl-l-homoserine lactone. The enzyme has stricter substrate selectivity and significantly lower KM values (ca. 50 μM for preferred substrates) compared to those of typicalmore » AHL lactonases (ca. >1 mM). X-ray crystal structures of AidC alone and with the product N-hexanoyl-l-homoserine were determined at resolutions of 1.09 and 1.67 Å, respectively. Each structure displays as a dimer, and dimeric oligiomerization was also observed in solution by size-exclusion chromatography coupled with multiangle light scattering. Lastly, the structures reveal two atypical features as compared to previously characterized AHL lactonases: a "kinked" α-helix that forms part of a closed binding pocket that provides affinity and enforces selectivity for AHL substrates and an active-site His substitution that is usually found in a homologous family of phosphodiesterases. We discuss implications for the catalytic mechanism of AHL lactonases.« less

A material based approach to creating wear resistant surfaces for hot forging

NASA Astrophysics Data System (ADS)

Babu, Sailesh

Tools and dies used in metal forming are characterized by extremely high temperatures at the interface, high local pressures and large metal to metal sliding. These harsh conditions result in accelerated wear of tooling. Lubrication of tools, done to improve metal flow drastically quenches the surface layers of the tools and compounds the tool failure problem. This phenomenon becomes a serious issue when parts forged at complex and are expected to meet tight tolerances. Unpredictable and hence uncontrolled wear and degradation of tooling result in poor part quality and premature tool failure that result in high scrap, shop downtime, poor efficiency and high cost. The objective of this dissertation is to develop a computer-based methodology for analyzing the requirements hot forging tooling to resist wear and plastic deformation and wear and predicting life cycle of forge tooling. Development of such is a system is complicated by the fact that wear and degradation of tooling is influenced by not only the die material used but also numerous process controls like lubricant, dilution ratio, forging temperature, equipment used, tool geometries among others. Phenomenological models available u1 the literature give us a good thumb rule to selecting materials but do not provide a way to evaluate pits performance in field. Once a material is chosen, there are no proven approaches to create surfaces out of these materials. Coating approaches like PVD and CVD cannot generate thick coatings necessary to withstand the conditions under hot forging. Welding cannot generate complex surfaces without several secondary operations like heat treating and machining. If careful procedures are not followed, welds crack and seldom survive forging loads. There is a strong need for an approach to selectively, reliably and precisely deposit material of choice reliably on an existing surface which exhibit not only good tribological properties but also good adhesion to the substrate. Dissertation outlines development of a new cyclic contact test design to recreate intermittent tempering seen in hot forging. This test has been used to validate the use of tempering parameters in modeling of in-service softening of tool steel surfaces. The dissertation also outlines an industrial case study, conducted at a forging company, to validate the wear model. This dissertation also outlines efforts at Ohio State University, to deposit Nickel Aluminide on AISI H13 substrate, using Laser Engineered Net Shaping (LENS). Dissertation reports results from an array of experiments conducted using LENS 750 machine, at various power levels, table speeds and hatch spacing. Results pertaining to bond quality, surface finish, compositional gradients and hardness are provided. Also, a thermal-based finite element numerical model that was used to simulate the LENS process is presented, along with some demonstrated results.

Survey of the occurrence of desiccation-induced quenching of basal fluorescence in 28 species of green microalgae.

PubMed

Wieners, Paul Christian; Mudimu, Opayi; Bilger, Wolfgang

2018-05-30

Desiccation-induced chlorophyll fluorescence quenching seems to be an indispensable part of desiccation resistance in the surveyed 28 green microalgal species. Lichens are desiccation tolerant meta-organisms. In the desiccated state photosynthesis is inhibited rendering the photobionts potentially sensitive to photoinhibition. As a photoprotective mechanism, strong non-radiative dissipation of absorbed light leading to quenching of chlorophyll fluorescence has been proposed. Desiccation-induced quenching affects not only variable fluorescence, but also the so-called basal fluorescence, F 0 . This phenomenon is well-known for intact lichens and some free living aero-terrestrial algae, but it was often absent in isolated lichen algae. Therefore, a thorough screening for the appearance of desiccation-induced quenching was undertaken with 13 different aero-terrestrial microalgal species and lichen photobionts. They were compared with 15 aquatic green microalgal species, among them also three marine species. We asked the following questions: Do isolated lichen algae show desiccation-induced quenching? Are aero-terrestrial algae different in this respect to aquatic algae and is the potential for desiccation-induced quenching coupled to desiccation tolerance? How variable is desiccation-induced quenching among species? Most of the aero-terrestrial algae, including all lichen photobionts, showed desiccation-induced quenching, although highly variable in extent, whereas most of the aquatic algae did not. All algae displaying quenching were also desiccation tolerant, whereas all algae unable to perform desiccation-induced quenching were desiccation intolerant. Desiccation-induced fluorescence quenching seems to be an indispensable part of desiccation resistance in the investigated species.

3D FEM Simulation of Flank Wear in Turning

NASA Astrophysics Data System (ADS)

Attanasio, Aldo; Ceretti, Elisabetta; Giardini, Claudio

2011-05-01

This work deals with tool wear simulation. Studying the influence of tool wear on tool life, tool substitution policy and influence on final part quality, surface integrity, cutting forces and power consumption it is important to reduce the global process costs. Adhesion, abrasion, erosion, diffusion, corrosion and fracture are some of the phenomena responsible of the tool wear depending on the selected cutting parameters: cutting velocity, feed rate, depth of cut, …. In some cases these wear mechanisms are described by analytical models as a function of process variables (temperature, pressure and sliding velocity along the cutting surface). These analytical models are suitable to be implemented in FEM codes and they can be utilized to simulate the tool wear. In the present paper a commercial 3D FEM software has been customized to simulate the tool wear during turning operations when cutting AISI 1045 carbon steel with uncoated tungsten carbide tip. The FEM software was improved by means of a suitable subroutine able to modify the tool geometry on the basis of the estimated tool wear as the simulation goes on. Since for the considered couple of tool-workpiece material the main phenomena generating wear are the abrasive and the diffusive ones, the tool wear model implemented into the subroutine was obtained as combination between the Usui's and the Takeyama and Murata's models. A comparison between experimental and simulated flank tool wear curves is reported demonstrating that it is possible to simulate the tool wear development.

System and method for quench protection of a superconductor

DOEpatents

Huang, Xianrui; Sivasubramaniam, Kiruba Haran; Bray, James William; Ryan, David Thomas

2008-03-11

A system and method for protecting a superconductor from a quench condition. A quench protection system is provided to protect the superconductor from damage due to a quench condition. The quench protection system comprises a voltage detector operable to detect voltage across the superconductor. The system also comprises a frequency filter coupled to the voltage detector. The frequency filter is operable to couple voltage signals to a control circuit that are representative of a rise in superconductor voltage caused by a quench condition and to block voltage signals that are not. The system is operable to detect whether a quench condition exists in the superconductor based on the voltage signal received via the frequency filter and to initiate a protective action in response.

Quench dynamics in MgB2 Rutherford cables

NASA Astrophysics Data System (ADS)

Cubero, A.; Navarro, R.; Kováč, P.; Kopera, L.; Rindfleisch, M.; Martínez, E.

2018-04-01

The generation and propagation of quench induced by a local heat disturbance or by overcurrents in MgB2 Rutherford cables have been studied experimentally. The analysed cable is composed of 12 strands of monocore MgB2/Nb/Cu10Ni wire and has a transposition length of about 27 mm. Measurements of intra- and inter-strand voltages have been performed to analyse the superconducting-to-normal transition behaviour of these cables during quench. In case of external hot-spots, two different time-dynamic regimes have been observed, a slow stage for the formation of the minimum propagation zone (MPZ), and a fast dynamics once the quench is triggered and propagates to the rest of the cable. Significant local variations of the quench propagation velocity across the strands around the MPZ have been observed, but with average quench propagation velocities closely correlated with the predictions given by one-dimensional-geometry models. For quench induced by overcurrents (i.e. with applied currents higher than the critical current) the nucleation of many normal zones distributed within the cable, which overlap during quench propagation, gives a distinctive and faster quench dynamics.

Investigation of common fluorophores for the detection of nitrated explosives by fluorescence quenching.

PubMed

Meaney, Melissa S; McGuffin, Victoria L

2008-03-03

Previous studies have indicated that nitrated explosives may be detected by fluorescence quenching of pyrene and related compounds. The use of pyrene, however, invokes numerous health and waste disposal hazards. In the present study, ten safer fluorophores are identified for quenching detection of target nitrated compounds. Initially, Stern-Volmer constants are measured for each fluorophore with nitrobenzene and 4-nitrotoluene to determine the sensitivity of the quenching interaction. For quenching constants greater than 50 M(-1), sensitivity and selectivity are investigated further using an extended set of target quenchers. Nitromethane, nitrobenzene, 4-nitrotoluene, and 2,6-dinitrotoluene are chosen to represent nitrated explosives and their degradation products; aniline, benzoic acid, and phenol are chosen to represent potential interfering compounds. Among the fluorophores investigated, purpurin, malachite green, and phenol red demonstrate the greatest sensitivity and selectivity for nitrated compounds. Correlation of the quenching rate constants for these fluorophores to Rehm-Weller theory suggests an electron-transfer quenching mechanism. As a result of the large quenching constants, purpurin, malachite green, and phenol red are the most promising for future detection of nitrated explosives via fluorescence quenching.

Finite size induces crossover temperature in growing spin chains

NASA Astrophysics Data System (ADS)

Sienkiewicz, Julian; Suchecki, Krzysztof; Hołyst, Janusz A.

2014-01-01

We introduce a growing one-dimensional quenched spin model that bases on asymmetrical one-side Ising interactions in the presence of external field. Numerical simulations and analytical calculations based on Markov chain theory show that when the external field is smaller than the exchange coupling constant J there is a nonmonotonous dependence of the mean magnetization on the temperature in a finite system. The crossover temperature Tc corresponding to the maximal magnetization decays with system size, approximately as the inverse of the Lambert W function. The observed phenomenon can be understood as an interplay between the thermal fluctuations and the presence of the first cluster determined by initial conditions. The effect exists also when spins are not quenched but fully thermalized after the attachment to the chain. By performing tests on real data we conceive the model is in part suitable for a qualitative description of online emotional discussions arranged in a chronological order, where a spin in every node conveys emotional valence of a subsequent post.

Golf-course and funnel energy landscapes: Protein folding concepts in martensites

NASA Astrophysics Data System (ADS)

Shankaraiah, N.

2017-06-01

We use protein folding energy landscape concepts such as golf course and funnel to study re-equilibration in athermal martensites under systematic temperature quench Monte Carlo simulations. On quenching below a transition temperature, the seeded high-symmetry parent-phase austenite that converts to the low-symmetry product-phase martensite, through autocatalytic twinning or elastic photocopying, has both rapid conversions and incubation delays in the temperature-time-transformation phase diagram. We find the rapid (incubation delays) conversions at low (high) temperatures arises from the presence of large (small) size of golf-course edge that has the funnel inside for negative energy states. In the incubating state, the strain structure factor enters into the Brillouin-zone golf course through searches for finite transitional pathways which close off at the transition temperature with Vogel-Fulcher divergences that are insensitive to Hamiltonian energy scales and log-normal distributions, as signatures of dominant entropy barriers. The crossing of the entropy barrier is identified through energy occupancy distributions, Monte Carlo acceptance fractions, heat emission, and internal work.

On the Stark effect in open shell complexes exhibiting partially quenched electronic angular momentum: Infrared laser Stark spectroscopy of OH–C 2H 2, OH–C 2H 4, and OH–H 2O

DOE PAGES

Moradi, Christopher P.; Douberly, Gary E.

2015-06-22

The Stark effect is considered for polyatomic open shell complexes that exhibit partially quenched electronic angular momentum. Matrix elements of the Stark Hamiltonian represented in a parity conserving Hund's case (a) basis are derived for the most general case, in which the permanent dipole moment has projections on all three inertial axes of the system. Transition intensities are derived, again for the most general case, in which the laser polarization has projections onto axes parallel and perpendicular to the Stark electric field, and the transition dipole moment vector is projected onto all three inertial axes in the molecular frame. Asmore » a result, simulations derived from this model are compared to experimental rovibrational Stark spectra of OH-C 2H 2, OH-C 2H 4, and OH-H 2O complexes formed in helium nanodroplets.« less

Finite size induces crossover temperature in growing spin chains.

PubMed

Sienkiewicz, Julian; Suchecki, Krzysztof; Hołyst, Janusz A

2014-01-01

We introduce a growing one-dimensional quenched spin model that bases on asymmetrical one-side Ising interactions in the presence of external field. Numerical simulations and analytical calculations based on Markov chain theory show that when the external field is smaller than the exchange coupling constant J there is a nonmonotonous dependence of the mean magnetization on the temperature in a finite system. The crossover temperature Tc corresponding to the maximal magnetization decays with system size, approximately as the inverse of the Lambert W function. The observed phenomenon can be understood as an interplay between the thermal fluctuations and the presence of the first cluster determined by initial conditions. The effect exists also when spins are not quenched but fully thermalized after the attachment to the chain. By performing tests on real data we conceive the model is in part suitable for a qualitative description of online emotional discussions arranged in a chronological order, where a spin in every node conveys emotional valence of a subsequent post.

Numerical analysis of quantitative measurement of hydroxyl radical concentration using laser-induced fluorescence in flame

NASA Astrophysics Data System (ADS)

Shuang, Chen; Tie, Su; Yao-Bang, Zheng; Li, Chen; Ting-Xu, Liu; Ren-Bing, Li; Fu-Rong, Yang

2016-06-01

The aim of the present work is to quantitatively measure the hydroxyl radical concentration by using LIF (laser-induced fluorescence) in flame. The detailed physical models of spectral absorption lineshape broadening, collisional transition and quenching at elevated pressure are built. The fine energy level structure of the OH molecule is illustrated to understand the process with laser-induced fluorescence emission and others in the case without radiation, which include collisional quenching, rotational energy transfer (RET), and vibrational energy transfer (VET). Based on these, some numerical results are achieved by simulations in order to evaluate the fluorescence yield at elevated pressure. These results are useful for understanding the real physical processes in OH-LIF technique and finding a way to calibrate the signal for quantitative measurement of OH concentration in a practical combustor. Project supported by the National Natural Science Foundation of China (Grant No. 11272338) and the Fund from the Science and Technology on Scramjet Key Laboratory, China (Grant No. STSKFKT2013004).

Spectroscopic studies on the interaction of sodium benzoate, a food preservative, with calf thymus DNA.

PubMed

Zhang, Guowen; Ma, Yadi

2013-11-01

The interaction between sodium benzoate (SB) and calf thymus DNA in simulated physiological buffer (pH 7.4) using acridine orange (AO) dye as a fluorescence probe, was investigated by UV-Vis absorption, fluorescence and circular dichroism (CD) spectroscopy along with DNA melting studies and viscosity measurements. An expanded UV-Vis spectral data matrix was resolved by multivariate curve resolution-alternating least squares (MCR-ALS) approach. The equilibrium concentration profiles and the pure spectra for SB, DNA and DNA-SB complex from the high overlapping composite response were simultaneously obtained. The results indicated that SB could bind to DNA, and hydrophobic interactions and hydrogen bonds played a vital role in the binding process. Moreover, SB was able to quench the fluorescence of DNA-AO complex through a static procedure. The quenching observed was indicative of an intercalative mode of interaction between SB and DNA, which was supported by melting studies, viscosity measurements and CD analysis. Copyright © 2013 Elsevier Ltd. All rights reserved.

Quantitative Analysis of the Efficiency of OLEDs.

PubMed

Sim, Bomi; Moon, Chang-Ki; Kim, Kwon-Hyeon; Kim, Jang-Joo

2016-12-07

We present a comprehensive model for the quantitative analysis of factors influencing the efficiency of organic light-emitting diodes (OLEDs) as a function of the current density. The model takes into account the contribution made by the charge carrier imbalance, quenching processes, and optical design loss of the device arising from various optical effects including the cavity structure, location and profile of the excitons, effective radiative quantum efficiency, and out-coupling efficiency. Quantitative analysis of the efficiency can be performed with an optical simulation using material parameters and experimental measurements of the exciton profile in the emission layer and the lifetime of the exciton as a function of the current density. This method was applied to three phosphorescent OLEDs based on a single host, mixed host, and exciplex-forming cohost. The three factors (charge carrier imbalance, quenching processes, and optical design loss) were influential in different ways, depending on the device. The proposed model can potentially be used to optimize OLED configurations on the basis of an analysis of the underlying physical processes.

Computer simulation of a cellular automata model for the immune response in a retrovirus system

NASA Astrophysics Data System (ADS)

Pandey, R. B.

1989-02-01

Immune response in a retrovirus system is modeled by a network of three binary cell elements to take into account some of the main functional features of T4 cells, T8 cells, and viruses. Two different intercell interactions are introduced, one of which leads to three fixed points while the other yields bistable fixed points oscillating between a healthy state and a sick state in a mean field treatment. Evolution of these cells is studied for quenched and annealed random interactions on a simple cubic lattice with a nearest neighbor interaction using inhomogenous cellular automata. Populations of T4 cells and viral cells oscillate together with damping (with constant amplitude) for annealed (quenched) interaction on increasing the value of mixing probability B from zero to a characteristic value B ca ( B cq). For higher B, the average number of T4 cells increases while that of the viral infected cells decreases monotonically on increasing B, suggesting a phase transition at B ca ( B cq).

Numerical Study of Microstructural Evolution During Homogenization of Al-Si-Mg-Fe-Mn Alloys

NASA Astrophysics Data System (ADS)

Priya, Pikee; Johnson, David R.; Krane, Matthew J. M.

2016-09-01

Microstructural evolution during homogenization of Al-Si-Mg-Fe-Mn alloys occurs in two stages at different length scales: while holding at the homogenization temperature (diffusion on the scale of the secondary dendrite arm spacing (SDAS) in micrometers) and during quenching to room temperature (dispersoid precipitation at the nanometer to submicron scale). Here a numerical study estimates microstructural changes during both stages. A diffusion-based model developed to simulate evolution at the SDAS length scale predicts homogenization times and microstructures matching experiments. That model is coupled with a Kampmann Wagner Neumann-based precipitate nucleation and growth model to study the effect of temperature, composition, as-cast microstructure, and cooling rates during posthomogenization quenching on microstructural evolution. A homogenization schedule of 853 K (580 °C) for 8 hours, followed by cooling at 250 K/h, is suggested to optimize microstructures for easier extrusion, consisting of minimal α-Al(FeMn)Si, no β-AlFeSi, and Mg2Si dispersoids <1 μm size.

Local and integral disruption forces on the tokamak wall

NASA Astrophysics Data System (ADS)

Pustovitov, V. D.; Kiramov, D. I.

2018-04-01

The disruption-induced forces on the tokamak wall are evaluated analytically within the standard large-aspect-ratio model that implies axisymmetry, circular plasma and wall, and absence of halo currents. Additionally, the ideal-wall reaction is assumed. The disruptions are modelled as rapid changes in the plasma pressure (thermal quench (TQ)) and net current (current quench (CQ)). The force distribution over the poloidal angle is found as a function of these inputs. The derived formulas allow comparison of the TQ- and CQ-produced forces calculated differently, with and without account of the poloidal current induced in the wall. The latter variant represents the inherent property of the codes treating the wall as a set of toroidal filaments. It is proved here that such a simplification leads to unacceptably large errors in the simulated forces for both TQs and CQs. It is also shown that the TQ part of the force must prevail over that due to CQ in the high-β scenarios developed for JT-60SA and ITER.

Belousov—Zhabotinskii reaction systems in the presence of Ag +

NASA Astrophysics Data System (ADS)

Rastogi, R. P.; Mani, Kiran; Misra, G. P.

1991-03-01

Threshold values of [Ag +] for quenching (i) Br - potential oscillation and (ii) redox potential oscillations + Br - oscillations have been determined under aerobic and anaerobic conditions for the (a) malonic acid + Ce 4+ + BrO -3 + H 2SO 4 system, and the (b) oxalic acid + acetone + Ce 4+ + BrO -3 + H 2SO 4 system. Similar experiments on the lower limit of BrO -3 under aerobic/anaerobic conditions are reported. The results show that the mechanism of quenching, so far as the key steps are concerned, is expected to be the same in the two cases. Numerical simulations have been made on the basis of the Field, Körös and Noyes (FKN) mechanisms with the additional step Ag + + Br - ⇌ AgBr. The analysis shows that the experimental results can be explained quite well if the corresponding forward rate constant, k6, is assumed to lie between 10 4-10 5 M -1 s -1, as has been suggested by Ruoff and others.

High Load Ratio Fatigue Strength and Mean Stress Evolution of Quenched and Tempered 42CrMo4 Steel

NASA Astrophysics Data System (ADS)

Bertini, Leonardo; Le Bone, Luca; Santus, Ciro; Chiesi, Francesco; Tognarelli, Leonardo

2017-08-01

The fatigue strength at a high number of cycles with initial elastic-plastic behavior was experimentally investigated on quenched and tempered 42CrMo4 steel. Fatigue tests on unnotched specimens were performed both under load and strain controls, by imposing various levels of amplitude and with several high load ratios. Different ratcheting and relaxation trends, with significant effects on fatigue, are observed and discussed, and then reported in the Haigh diagram, highlighting a clear correlation with the Smith-Watson-Topper model. High load ratio tests were also conducted on notched specimens with C (blunt) and V (sharp) geometries. A Chaboche model with three parameter couples was proposed by fitting plain specimen cyclic and relaxation tests, and then finite element analyses were performed to simulate the notched specimen test results. A significant stress relaxation at the notch root became clearly evident by reporting the numerical results in the Haigh diagram, thus explaining the low mean stress sensitivity of the notched specimens.

Detecting many-body-localization lengths with cold atoms

NASA Astrophysics Data System (ADS)

Guo, Xuefei; Li, Xiaopeng

2018-03-01

Considering ultracold atoms in optical lattices, we propose experimental protocols to study many-body-localization (MBL) length and criticality in quench dynamics. Through numerical simulations with exact diagonalization, we show that in the MBL phase the perturbed density profile following a local quench remains exponentially localized in postquench dynamics. The size of this density profile after long-time-dynamics defines a localization length, which tends to diverge at the MBL-to-ergodic transition as we increase the system size. The determined localization transition point agrees with previous exact diagonalization calculations using other diagnostics. Our numerical results provide evidence for violation of the Harris-Chayes bound for the MBL criticality. The critical exponent ν can be extracted from our proposed dynamical procedure, which can then be used directly in experiments to determine whether the Harris-Chayes-bound holds for the MBL transition. These proposed protocols to detect localization criticality are justified by benchmarking to the well-established results for the noninteracting three-dimensional Anderson localization.

Resolving ultrafast exciton migration in organic solids at the nanoscale.

PubMed

Penwell, Samuel B; Ginsberg, Lucas D S; Noriega, Rodrigo; Ginsberg, Naomi S

2017-11-01

Effectiveness of molecular-based light harvesting relies on transport of excitons to charge-transfer sites. Measuring exciton migration, however, has been challenging because of the mismatch between nanoscale migration lengths and the diffraction limit. Instead of using bulk substrate quenching methods, here we define quenching boundaries all-optically with sub-diffraction resolution, thus characterizing spatiotemporal exciton migration on its native nanometre and picosecond scales. By transforming stimulated emission depletion microscopy into a time-resolved ultrafast approach, we measure a 16-nm migration length in poly(2,5-di(hexyloxy)cyanoterephthalylidene) conjugated polymer films. Combined with Monte Carlo exciton hopping simulations, we show that migration in these films is essentially diffusive because intrinsic chromophore energetic disorder is comparable to chromophore inhomogeneous broadening. Our approach will enable previously unattainable correlation of local material structure to exciton migration character, applicable not only to photovoltaic or display-destined organic semiconductors but also to explaining the quintessential exciton migration exhibited in photosynthesis.

Model of vertical plasma motion during the current quench

NASA Astrophysics Data System (ADS)

Breizman, Boris; Kiramov, Dmitrii

2017-10-01

Tokamak disruptions impair plasma position control, which allows the plasma column to move and hit the wall. These detrimental events enhance thermal and mechanical loads due to halo currents and runaway electron losses. Their fundamental understanding and prevention is one of the high-priority items for ITER. As commonly observed in experiments, the disruptive plasma tends to move vertically, and the timescale of this motion is rather resistive than Alfvenic. These observations suggest that the plasma column is nearly force-free during its vertical motion. In fact, the force-free constraint is already used in disruption simulators. In this work, we consider a geometrically simple system that mimics the tokamak plasma surrounded by the conducting structures. Using this model, we highlight the underlying mechanism of the vertical displacement events during the current quench phase of plasma disruption. We also address a question of ideal MHD stability of the plasma during its resistive motion. Work supported by the U.S. Department of Energy Contracts DEFG02-04ER54742 and DE-SC0016283.

Pivotal issues on relativistic electrons in ITER

NASA Astrophysics Data System (ADS)

Boozer, Allen H.

2018-03-01

The transfer of the plasma current from thermal to relativistic electrons is a threat to ITER achieving its mission. This danger is significantly greater in the nuclear than in the non-nuclear phase of ITER operations. Two issues are pivotal. The first is the extent and duration of magnetic surface breaking in conjunction with the thermal quenches. The second is the exponential sensitivity of the current transfer to three quantities: (1) the poloidal flux change required to e-fold the number of relativistic electrons, (2) the time τa after the beginning of the thermal quench before the accelerating electric field exceeds the Connor-Hastie field for runaway, and (3) the duration of the period τ_op in which magnetic surfaces remain open. Adequate knowledge does not exist to devise a reliable strategy for the protection of ITER. Uncertainties are sufficiently large that a transfer of neither a negligible nor the full plasma current to relativistic electrons can be ruled out during the non-nuclear phase of ITER. Tritium decay can provide a sufficiently strong seed for a dangerous relativistic-electron current even if τa and τ_op are sufficiently long to avoid relativistic electrons during non-nuclear operations. The breakup of magnetic surfaces that is associated with thermal quenches occurs on a time scale associated with fast magnetic reconnection, which means reconnection at an Alfvénic rather than a resistive rate. Alfvénic reconnection is well beyond the capabilities of existing computational tools for tokamaks, but its effects can be studied using its property of conserving magnetic helicity. Although the dangers to ITER from relativistic electrons have been known for twenty years, the critical issues have not been defined with sufficient precision to formulate an effective research program. Studies are particularly needed on plasma behavior in existing tokamaks during thermal quenches, behavior which could be clarified using methods developed here.

Vehicle Technology Simulation and Analysis Tools | Transportation Research

Science.gov Websites

| NREL Vehicle Technology Simulation and Analysis Tools Vehicle Technology Simulation and vehicle technologies with the potential to achieve significant fuel savings and emission reductions. NREL : Automotive Deployment Options Projection Tool The ADOPT modeling tool estimates vehicle technology

Quench Protection Studies of 11T Nb$$_3$$Sn Dipole Models for LHC Upgrades

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zlobin, Alexander; Chlachidze, Guram; Nobrega, Alfred

CERN and FNAL are developing 11 T Nb3Sn dipole magnets for the LHC collimation system upgrade. Due to the large stored energy, protection of these magnets during a quench is a challenging problem. This paper reports the results of experimental studies of key quench protection parameters including longitudinal and radial quench propagation in the coil, coil heating due to a quench, and energy extraction and quench-back effect. The studies were performed using a 1 m long 11 T Nb3Sn dipole coil tested in a magnetic mirror configuration.

A simplified design of the staggered herringbone micromixer for practical applications

PubMed Central

Du, Yan; Zhang, Zhiyi; Yim, ChaeHo; Lin, Min; Cao, Xudong

2010-01-01

We demonstrated a simple method for the device design of a staggered herringbone micromixer (SHM) using numerical simulation. By correlating the simulated concentrations with channel length, we obtained a series of concentration versus channel length profiles, and used mixing completion length Lm as the only parameter to evaluate the performance of device structure on mixing. Fluorescence quenching experiments were subsequently conducted to verify the optimized SHM structure for a specific application. Good agreement was found between the optimization and the experimental data. Since Lm is straightforward, easily defined and calculated parameter for characterization of mixing performance, this method for designing micromixers is simple and effective for practical applications. PMID:20697584

A simplified design of the staggered herringbone micromixer for practical applications.

PubMed

Du, Yan; Zhang, Zhiyi; Yim, Chaeho; Lin, Min; Cao, Xudong

2010-05-07

We demonstrated a simple method for the device design of a staggered herringbone micromixer (SHM) using numerical simulation. By correlating the simulated concentrations with channel length, we obtained a series of concentration versus channel length profiles, and used mixing completion length L(m) as the only parameter to evaluate the performance of device structure on mixing. Fluorescence quenching experiments were subsequently conducted to verify the optimized SHM structure for a specific application. Good agreement was found between the optimization and the experimental data. Since L(m) is straightforward, easily defined and calculated parameter for characterization of mixing performance, this method for designing micromixers is simple and effective for practical applications.

Fast Low-to-High Confinement Mode Bifurcation Dynamics in a Tokamak Edge Plasma Gyrokinetic Simulation.

PubMed

Chang, C S; Ku, S; Tynan, G R; Hager, R; Churchill, R M; Cziegler, I; Greenwald, M; Hubbard, A E; Hughes, J W

2017-04-28

Transport barrier formation and its relation to sheared flows in fluids and plasmas are of fundamental interest in various natural and laboratory observations and of critical importance in achieving an economical energy production in a magnetic fusion device. Here we report the first observation of an edge transport barrier formation event in an electrostatic gyrokinetic simulation carried out in a realistic diverted tokamak edge geometry under strong forcing by a high rate of heat deposition. The results show that turbulent Reynolds-stress-driven sheared E×B flows act in concert with neoclassical orbit loss to quench turbulent transport and form a transport barrier just inside the last closed magnetic flux surface.

Single Particle Jumps in Sheared SiO2

NASA Astrophysics Data System (ADS)

McMahon, Sean; Vollmayr-Lee, Katharina; Cookmeyer, Jonathan; Horbach, Juergen

We study the dynamics of a sheared glass via molecular dynamics simulations. Using the BKS potential we simulate the strong glass former SiO2. The system is initially well equilibrated at a high temperature, then quenched to a temperature below the glass transition, and, after a waiting time at the desired low temperature, sheared with constant strain rate. We present preliminary results of an analysis of single particle trajectories of the sheared glass. We acknowledge the support via NSF REU Grant #PHY-1156964, DoD ASSURE program, and NSF-MRI CHE-1229354 as part of the MERCURY high-performance computer consortium. We thank G.P. Shrivastav, Ch. Scherer and B. Temelso.

Simulating Asymmetric Top Impurities in Superfluid Clusters: A para-Water Dopant in para-Hydrogen.

PubMed

Zeng, Tao; Li, Hui; Roy, Pierre-Nicholas

2013-01-03

We present the first simulation study of bosonic clusters doped with an asymmetric top molecule. The path-integral Monte Carlo method with the latest methodological advance in treating rigid-body rotation [Noya, E. G.; Vega, C.; McBride, C. J. Chem. Phys.2011, 134, 054117] is employed to study a para-water impurity in para-hydrogen clusters with up to 20 para-hydrogen molecules. The growth pattern of the doped clusters is similar in nature to that of pure clusters. The para-water molecule appears to rotate freely in the cluster. The presence of para-water substantially quenches the superfluid response of para-hydrogen with respect to the space-fixed frame.

Simulated annealing in networks for computing possible arrangements for red and green cones

NASA Technical Reports Server (NTRS)

Ahumada, Albert J., Jr.

1987-01-01

Attention is given to network models in which each of the cones of the retina is given a provisional color at random, and then the cones are allowed to determine the colors of their neighbors through an iterative process. A symmetric-structure spin-glass model has allowed arrays to be generated from completely random arrangements of red and green to arrays with approximately as much disorder as the parafoveal cones. Simulated annealing has also been added to the process in an attempt to generate color arrangements with greater regularity and hence more revealing moirepatterns than than the arrangements yielded by quenched spin-glass processes. Attention is given to the perceptual implications of these results.

An adaptive approach to the physical annealing strategy for simulated annealing

NASA Astrophysics Data System (ADS)

Hasegawa, M.

2013-02-01

A new and reasonable method for adaptive implementation of simulated annealing (SA) is studied on two types of random traveling salesman problems. The idea is based on the previous finding on the search characteristics of the threshold algorithms, that is, the primary role of the relaxation dynamics in their finite-time optimization process. It is shown that the effective temperature for optimization can be predicted from the system's behavior analogous to the stabilization phenomenon occurring in the heating process starting from a quenched solution. The subsequent slow cooling near the predicted point draws out the inherent optimizing ability of finite-time SA in more straightforward manner than the conventional adaptive approach.

Dynamic depinning phase transition in magnetic thin film with anisotropy

NASA Astrophysics Data System (ADS)

Xiong, L.; Zheng, B.; Jin, M. H.; Wang, L.; Zhou, N. J.

2018-02-01

The dynamic pinning effects induced by quenched disorder are significant in manipulating the domain-wall motion in nano-magnetic materials. Through numerical simulations of the nonstationary domain-wall dynamics with the Landau-Lifshitz-Gilbert equation, we confidently detect a dynamic depinning phase transition in a magnetic thin film with anisotropy, which is of second order. The transition field, static and dynamic exponents are accurately determined, based on the dynamic scaling behavior far from stationary.

Glass and ceramics. [lunar resources

NASA Technical Reports Server (NTRS)

Haskin, Larry A.

1992-01-01

A variety of glasses and ceramics can be produced from bulk lunar materials or from separated components. Glassy products include sintered regolith, quenched molten basalt, and transparent glass formed from fused plagioclase. No research has been carried out on lunar material or close simulants, so properties are not known in detail; however, common glass technologies such as molding and spinning seem feasible. Possible methods for producing glass and ceramic materials are discussed along with some potential uses of the resulting products.

Elucidation of Prion Protein Conformational Changes Associated with Infectivity by Fluorescence Spectroscopy

DTIC Science & Technology

2007-06-01

developed the β-spiral model for PrPSc structure by using molecular dynamics simulations with the sequence of human PrPC (residues 90-231) under...SUPPLEMENTARY NOTES exerpts from thesis of Jessica Gilbert 14. ABSTRACT Steady state and lifetime fluorescence measurements were made on 12...lieu of F. We tried both methods. See Ms. Jessica Gilbert’s MS thesis for details, which is included. 6 Figure 4. Acrylamide quenching of Trp

Spectral correlations in Anderson insulating wires

NASA Astrophysics Data System (ADS)

Marinho, M.; Micklitz, T.

2018-01-01

We calculate the spectral level-level correlation function of Anderson insulating wires for all three Wigner-Dyson classes. A measurement of its Fourier transform, the spectral form factor, is within reach of state-of-the-art cold atom quantum quench experiments, and we find good agreement with recent numerical simulations of the latter. Our derivation builds on a representation of the level-level correlation function in terms of a local generating function which may prove useful in other contexts.

Spectral analysis and slow spreading dynamics on complex networks.

PubMed

Odor, Géza

2013-09-01

The susceptible-infected-susceptible (SIS) model is one of the simplest memoryless systems for describing information or epidemic spreading phenomena with competing creation and spontaneous annihilation reactions. The effect of quenched disorder on the dynamical behavior has recently been compared to quenched mean-field (QMF) approximations in scale-free networks. QMF can take into account topological heterogeneity and clustering effects of the activity in the steady state by spectral decomposition analysis of the adjacency matrix. Therefore, it can provide predictions on possible rare-region effects, thus on the occurrence of slow dynamics. I compare QMF results of SIS with simulations on various large dimensional graphs. In particular, I show that for Erdős-Rényi graphs this method predicts correctly the occurrence of rare-region effects. It also provides a good estimate for the epidemic threshold in case of percolating graphs. Griffiths Phases emerge if the graph is fragmented or if we apply a strong, exponentially suppressing weighting scheme on the edges. The latter model describes the connection time distributions in the face-to-face experiments. In case of a generalized Barabási-Albert type of network with aging connections, strong rare-region effects and numerical evidence for Griffiths Phase dynamics are shown. The dynamical simulation results agree well with the predictions of the spectral analysis applied for the weighted adjacency matrices.

pH and heat-dependent behaviour of glucose oxidase down to single molecule level by combined fluorescence spectroscopy and molecular modelling.

PubMed

Dumitraşcu, Loredana; Stănciuc, Nicoleta; Bahrim, Gabriela Elena; Ciumac, Alexandrina; Aprodu, Iuliana

2016-04-01

In the food industry, glucose oxidase (GOX) is used to improve the shelf life of food materials. The pH- and heat-induced conformational changes of glucose oxidase from Aspergillus niger were quantified by means of fluorescence spectroscopy and molecular dynamics simulations. The phase diagram showed an all-or-none transition process, indicating that pH and temperature largely influence the conformational state of GOX. Shifts in maximum wavelength of Trp, Tyr were registered as the protein encounters a lower pH (pH 4.0), suggesting significant changes of the polarity around the chromophore molecule. Quenching experiments using KI showed higher quenching constants of Trp and flavin adenine dinucleotide upon heating or by changing pH value, and were mainly correlated with the conformational changes upon protein matrix. Finally, valuable insights into the thermal behaviour of GOX were obtained from molecular modelling results. The conformation and structure of GOX protein is dependent upon the pH and heat treatment applied. Molecular dynamics simulation indicated significant changes in the substrate binding region at temperatures over 60 °C that might affect enzyme activity. Moreover, an important alteration of the small pocket hosting the positively charged His(516) residue responsible for oxygen activation appears evident at high temperatures. © 2015 Society of Chemical Industry.

[Interference for Various Quench Agents of Chemical Disinfectants on Detection of Endotoxin Activities in Water].

PubMed

Zhang, Can; Liu, Wen-jun; Shi, Yun; An, Dai-zhi; Bai, Miao; Xu, Wen

2015-05-01

The quenching agents such as histidine, glycine, ascorbic acid, Tween-80, sodium sulfite and sodium hyposulfite are commonly used for quenching the residual disinfectant in water. In this paper, in order to select the optimal type and concentration range of quenching agents prior to the Limulus assays, the interference effects of each quenching agent at different concentrations on endotoxin detection were investigated by the Limulus assays of kinetic-turbidity. Our results identified that, as for 0-1.0% concentration of histidine, ascorbic acid, Tween-80, sodium sulfite (pH unadjusted and pH neutral), interference on the Limulus assays was existed. Hence, these quenching agents could not be applied as neutralizers prior to Limulus assays. Although, there was no interference on endotoxin detection for the glycine, a yellow color, developed by the quenching products of glycine and glutaric dialdehyde, contributed to false positive results. Hence, glycine should not be used as quenching agents in Limulus assays for samples containing glutaric dialdehyde. Compared with other quenching agents as histidine, glycine, ascorbic acid, Tween-80, sodium sulfite, 0-1.0% concentration of sodium hyposulfite elicited no obvious interference, while 1.0%-5.0% concentration of sodium hyposulfite illustrated exhibition effect for endotoxin detection. All in all, compared with other quenching agents as histidine, glycine, ascorbic acid, Tween-80 and sodium sulfite, sodium hyposulfite is suitable for quenching chemicals prior to endotoxin detection and less than 0.5% of concentration is allowable.

QUENCH: A software package for the determination of quenching curves in Liquid Scintillation counting.

PubMed

Cassette, Philippe

2016-03-01

In Liquid Scintillation Counting (LSC), the scintillating source is part of the measurement system and its detection efficiency varies with the scintillator used, the vial and the volume and the chemistry of the sample. The detection efficiency is generally determined using a quenching curve, describing, for a specific radionuclide, the relationship between a quenching index given by the counter and the detection efficiency. A quenched set of LS standard sources are prepared by adding a quenching agent and the quenching index and detection efficiency are determined for each source. Then a simple formula is fitted to the experimental points to define the quenching curve function. The paper describes a software package specifically devoted to the determination of quenching curves with uncertainties. The experimental measurements are described by their quenching index and detection efficiency with uncertainties on both quantities. Random Gaussian fluctuations of these experimental measurements are sampled and a polynomial or logarithmic function is fitted on each fluctuation by χ(2) minimization. This Monte Carlo procedure is repeated many times and eventually the arithmetic mean and the experimental standard deviation of each parameter are calculated, together with the covariances between these parameters. Using these parameters, the detection efficiency, corresponding to an arbitrary quenching index within the measured range, can be calculated. The associated uncertainty is calculated with the law of propagation of variances, including the covariance terms. Copyright © 2015 Elsevier Ltd. All rights reserved.

LHC magnet quench protection system

NASA Astrophysics Data System (ADS)

Coull, L.; Hagedorn, D.; Remondino, V.; Rodriguez-Mateos, F.

1994-07-01

The quench protection system for the superconducting magnets of the CERN Large Hadron Collider (LHC) is described. The system is based on the so called 'cold diode' concept. In a group of series connected magnets if one magnet quenches then the magnetic energy of all the magnets will be dissipated in the quenched magnet so destroying it. This is avoided by by-passing the quenched magnet and then rapidly de-exciting the unquenched magnets. For the LHC machine it is foreseen to use silicon diodes situated inside the cryostat as by-pass elements - so called 'cold diodes'. The diodes are exposed to some 50 kGray of radiation during a 10 year operation life-time. The high energy density of the LHC magnets (500 kJ/m) coupled with the relatively slow propagation speed of a 'natural' quench (10 to 20 m/s) can lead to excessive heating of the zone where the quench started and to high internal voltages. It is therefore necessary to detect quickly the incipient quench and fire strip heaters which spread the quench out more quickly over a large volume of the magnet. After a quench the magnet chain must be de-excited rapidly to avoid spreading the quench to other magnets and over-heating the by-pass diode. This is done by switching high-power energy-dump resistors in series with the magnets. The LHC main ring magnet will be divided into 16 electrically separated units which has important advantages.

3D Vectorial Time Domain Computational Integrated Photonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kallman, J S; Bond, T C; Koning, J M

2007-02-16

The design of integrated photonic structures poses considerable challenges. 3D-Time-Domain design tools are fundamental in enabling technologies such as all-optical logic, photonic bandgap sensors, THz imaging, and fast radiation diagnostics. Such technologies are essential to LLNL and WFO sponsors for a broad range of applications: encryption for communications and surveillance sensors (NSA, NAI and IDIV/PAT); high density optical interconnects for high-performance computing (ASCI); high-bandwidth instrumentation for NIF diagnostics; micro-sensor development for weapon miniaturization within the Stockpile Stewardship and DNT programs; and applications within HSO for CBNP detection devices. While there exist a number of photonics simulation tools on the market,more » they primarily model devices of interest to the communications industry. We saw the need to extend our previous software to match the Laboratory's unique emerging needs. These include modeling novel material effects (such as those of radiation induced carrier concentrations on refractive index) and device configurations (RadTracker bulk optics with radiation induced details, Optical Logic edge emitting lasers with lateral optical inputs). In addition we foresaw significant advantages to expanding our own internal simulation codes: parallel supercomputing could be incorporated from the start, and the simulation source code would be accessible for modification and extension. This work addressed Engineering's Simulation Technology Focus Area, specifically photonics. Problems addressed from the Engineering roadmap of the time included modeling the Auston switch (an important THz source/receiver), modeling Vertical Cavity Surface Emitting Lasers (VCSELs, which had been envisioned as part of fast radiation sensors), and multi-scale modeling of optical systems (for a variety of applications). We proposed to develop novel techniques to numerically solve the 3D multi-scale propagation problem for both the microchip laser logic devices as well as devices characterized by electromagnetic (EM) propagation in nonlinear materials with time-varying parameters. The deliverables for this project were extended versions of the laser logic device code Quench2D and the EM propagation code EMsolve with new modules containing the novel solutions incorporated by taking advantage of the existing software interface and structured computational modules. Our approach was multi-faceted since no single methodology can always satisfy the tradeoff between model runtime and accuracy requirements. We divided the problems to be solved into two main categories: those that required Full Wave Methods and those that could be modeled using Approximate Methods. Full Wave techniques are useful in situations where Maxwell's equations are not separable (or the problem is small in space and time), while approximate techniques can treat many of the remaining cases.« less

QUENCHING OF STAR FORMATION IN SLOAN DIGITAL SKY SURVEY GROUPS: CENTRALS, SATELLITES, AND GALACTIC CONFORMITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knobel, Christian; Lilly, Simon J.; Woo, Joanna

2015-02-10

We re-examine the fraction of low-redshift Sloan Digital Sky Survey satellites and centrals in which star formation has been quenched, using the environment quenching efficiency formalism that separates out the dependence of stellar mass. We show that the centrals of the groups containing the satellites are responding to the environment in the same way as their satellites (at least for stellar masses above 10{sup 10.3} M {sub ☉}), and that the well-known differences between satellites and the general set of centrals arise because the latter are overwhelmingly dominated by isolated galaxies. The widespread concept of ''satellite quenching'' as the causemore » of environmental effects in the galaxy population can therefore be generalized to ''group quenching''. We then explore the dependence of the quenching efficiency of satellites on overdensity, group-centric distance, halo mass, the stellar mass of the satellite, and the stellar mass and specific star formation rate (sSFR) of its central, trying to isolate the effect of these often interdependent variables. We emphasize the importance of the central sSFR in the quenching efficiency of the associated satellites, and develop the meaning of this ''galactic conformity'' effect in a probabilistic description of the quenching of galaxies. We show that conformity is strong, and that it varies strongly across parameter space. Several arguments then suggest that environmental quenching and mass quenching may be different manifestations of the same underlying process. The marked difference in the apparent mass dependencies of environment quenching and mass quenching which produces distinctive signatures in the mass functions of centrals and satellites will arise naturally, since, for satellites at least, the distributions of the environmental variables that we investigate in this work are essentially independent of the stellar mass of the satellite.« less

High-Field Quench Behavior and Protection of $$Bi_2 Sr_2 Ca Cu_2 O_x$$ Coils: Minimum and Maximum Quench Detection Voltages

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Tengming; Ye, Liyang; Turrioni, Daniele

Small insert coils have been built using a multifilamentary Bi2Sr2CaCu2Ox round wire, and characterized in background fields to explore the quench behaviors and limits of Bi2Sr2CaCu2Ox superconducting magnets, with an emphasis on assessing the impact of slow normal zone propagation on quench detection. Using heaters of various lengths to initiate a small normal zone, a coil was quenched safely more than 70 times without degradation, with the maximum coil temperature reaching 280 K. Coils withstood a resistive voltage of tens of mV for seconds without quenching, showing the high stability of these coils and suggesting that the quench detection voltagemore » shall be greater than 50 mV to not to falsely trigger protection. The hot spot temperature for the resistive voltage of the normal zone to reach 100 mV increases from ~40 K to ~80 K with increasing the operating wire current density Jo from 89 A/mm2 to 354 A/mm2 whereas for the voltage to reach 1 V, it increases from ~60 K to ~140 K, showing the increasing negative impact of slow normal zone propagation on quench detection with increasing Jo and the need to limit the quench detection voltage to < 1 V. These measurements, coupled with an analytical quench model, were used to access the impact of the maximum allowable voltage and temperature upon quench detection on the quench protection, assuming to limit the hot spot temperature to <300 K.« less

Microscopic simulation of xenon-based optical TPCs in the presence of molecular additives

NASA Astrophysics Data System (ADS)

Azevedo, C. D. R.; González-Díaz, D.; Biagi, S. F.; Oliveira, C. A. B.; Henriques, C. A. O.; Escada, J.; Monrabal, F.; Gómez-Cadenas, J. J.; Álvarez, V.; Benlloch-Rodríguez, J. M.; Borges, F. I. G. M.; Botas, A.; Cárcel, S.; Carrión, J. V.; Cebrián, S.; Conde, C. A. N.; Díaz, J.; Diesburg, M.; Esteve, R.; Felkai, R.; Fernandes, L. M. P.; Ferrario, P.; Ferreira, A. L.; Freitas, E. D. C.; Goldschmidt, A.; Gutiérrez, R. M.; Hauptman, J.; Hernandez, A. I.; Morata, J. A. Hernando; Herrero, V.; Jones, B. J. P.; Labarga, L.; Laing, A.; Lebrun, P.; Liubarsky, I.; Lopez-March, N.; Losada, M.; Martín-Albo, J.; Martínez-Lema, G.; Martínez, A.; McDonald, A. D.; Monteiro, C. M. B.; Mora, F. J.; Moutinho, L. M.; Vidal, J. Muñoz; Musti, M.; Nebot-Guinot, M.; Novella, P.; Nygren, D.; Palmeiro, B.; Para, A.; Pérez, J.; Querol, M.; Renner, J.; Ripoll, L.; Rodríguez, J.; Rogers, L.; Santos, F. P.; dos Santos, J. M. F.; Serra, L.; Shuman, D.; Simón, A.; Sofka, C.; Sorel, M.; Stiegler, T.; Toledo, J. F.; Torrent, J.; Tsamalaidze, Z.; Veloso, J. F. C. A.; Webb, R.; White, J. T.; Yahlali, N.

2018-01-01

We introduce a simulation framework for the transport of high and low energy electrons in xenon-based optical time projection chambers (OTPCs). The simulation relies on elementary cross sections (electron-atom and electron-molecule) and incorporates, in order to compute the gas scintillation, the reaction/quenching rates (atom-atom and atom-molecule) of the first 41 excited states of xenon and the relevant associated excimers, together with their radiative cascade. The results compare positively with observations made in pure xenon and its mixtures with CO2 and CF4 in a range of pressures from 0.1 to 10 bar. This work sheds some light on the elementary processes responsible for the primary and secondary xenon-scintillation mechanisms in the presence of additives, that are of interest to the OTPC technology.

Investigation of Mechanical Properties and Fracture Simulation of Solution-Treated AA 5754

NASA Astrophysics Data System (ADS)

Kumar, Pankaj; Singh, Akhilendra

2017-10-01

In this work, mechanical properties and fracture toughness of as-received and solution-treated aluminum alloy 5754 (AA 5754) are experimentally evaluated. Solution heat treatment of the alloy is performed at 530 °C for 2 h, and then, quenching is done in water. Yield strength, ultimate tensile strength, impact toughness, hardness, fatigue life, brittle fracture toughness (K_{Ic} ) and ductile fracture toughness (J_{Ic} ) are evaluated for as-received and solution-treated alloy. Extended finite element method has been used for the simulation of tensile and fracture behavior of material. Heaviside function and asymptotic crack tip enrichment functions are used for modelling of the crack in the geometry. Ramberg-Osgood material model coupled with fracture energy is used to simulate the crack propagation. Fracture surfaces obtained from various mechanical tests are characterized by scanning electron microscopy.

Proceedings of the 1987 conference on tools for the simulation profession

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hawkins, R.; Klukis, K.

1987-01-01

This book covers the proceedings of the 1987 conference on tools for the simulation profession. Some of the topics are: SIMULACT: a generic tool for simulating distributed systems; ESL language simulation of spacecraft batteries; and Trends in global cadmium levels from increased use of fossil fuels.

IgSimulator: a versatile immunosequencing simulator.

PubMed

Safonova, Yana; Lapidus, Alla; Lill, Jennie

2015-10-01

The recent introduction of next-generation sequencing technologies to antibody studies have resulted in a growing number of immunoinformatics tools for antibody repertoire analysis. However, benchmarking these newly emerging tools remains problematic since the gold standard datasets that are needed to validate these tools are typically not available. Since simulating antibody repertoires is often the only feasible way to benchmark new immunoinformatics tools, we developed the IgSimulator tool that addresses various complications in generating realistic antibody repertoires. IgSimulator's code has modular structure and can be easily adapted to new requirements to simulation. IgSimulator is open source and freely available as a C++ and Python program running on all Unix-compatible platforms. The source code is available from yana-safonova.github.io/ig_simulator. safonova.yana@gmail.com Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Influence of Fluidized Bed Quenching on the Mechanical Properties and Quality Index of T6 Tempered B319.2-Type Aluminum Alloys

NASA Astrophysics Data System (ADS)

Ragab, Kh. A.; Samuel, A. M.; Al-Ahmari, A. M. A.; Samuel, F. H.; Doty, H. W.

2013-11-01

The current study aimed to investigate the effect of fluidized sand bed (FB) quenching on the mechanical performance of B319.2 aluminum cast alloys. Traditional water and conventional hot air (CF) quenching media were used to establish a relevant comparison with FB quenching. Quality charts were generated using two models of quality indices to support the selection of material conditions on the basis of the proposed quality indices. The use of an FB for the direct quenching-aging treatment of B319.2 casting alloys yields greater UTS and YS values compared to conventional furnace quenched alloys. The strength values of T6 tempered B319 alloys are greater when quenched in water compared with those quenched in an FB or CF. For the same aging conditions (170°C/4h), the fluidized bed quenched-aged 319 alloys show nearly the same or better strength values than those quenched in water and then aged in a CF or an FB. Based on the quality charts developed for alloys subjected to different quenching media, higher quality index values are obtained by conventional furnace quenched-aged T6-tempered B319 alloys. The modification factor has the most significant effect on the quality results of the alloys investigated, for all heat treatment cycles, as compared to other metallurgical parameters. The results of alloys subjected to multi-temperature aging cycles reveal that the optimum strength properties of B319.2 alloys, however, is obtained by applying multi-temperature aging cycles such as, for example, 240 °C/2 h followed by 170 °C/8 h, rather than T6 aging treatments. The regression models indicate that the mean quality values of B319 alloys are highly quench sensitive due to the formation of a larger percent of clusters in Al-Si-Cu-Mg alloys. These clusters act as heterogeneous nucleation sites for precipitation and enhance the aging process.

Fluorescence of size-expanded DNA bases: reporting on DNA sequence and structure with an unnatural genetic set.

PubMed

Krueger, Andrew T; Kool, Eric T

2008-03-26

We recently described the synthesis and helix assembly properties of expanded DNA (xDNA), which contains base pairs 2.4 A larger than natural DNA pairs. This designed genetic set is under study with the goals of mimicking the functions of the natural DNA-based genetic system and of developing useful research tools. Here, we study the fluorescence properties of the four expanded bases of xDNA (xA, xC, xG, xT) and evaluate how their emission varies with changes in oligomer length, composition, and hybridization. Experiments were carried out with short oligomers of xDNA nucleosides conjugated to a DNA oligonucleotide, and we investigated the effects of hybridizing these fluorescent oligomers to short complementary DNAs with varied bases opposite the xDNA bases. As monomer nucleosides, the xDNA bases absorb light in two bands: one at approximately 260 nm (similar to DNA) and one at longer wavelength ( approximately 330 nm). All are efficient violet-blue fluorophores with emission maxima at approximately 380-410 nm and quantum yields (Phifl) of 0.30-0.52. Short homo-oligomers of the xDNA bases (length 1-4 monomers) showed moderate self-quenching except xC, which showed enhancement of Phifl with increasing length. Interestingly, multimers of xA emitted at longer wavelengths (520 nm) as an apparent excimer. Hybridization of an oligonucleotide to the DNA adjacent to the xDNA bases (with the xDNA portion overhanging) resulted in no change in fluorescence. However, addition of one, two, or more DNA bases in these duplexes opposite the xDNA portion resulted in a number of significant fluorescence responses, including wavelength shifts, enhancements, or quenching. The strongest responses were the enhancement of (xG)n emission by hybridization of one or more adenines opposite them, and the quenching of (xT)n and (xC)n emission by guanines opposite. The data suggest multiple ways in which the xDNA bases, both alone and in oligomers, may be useful as tools in biophysical analysis and biotechnological applications.

Risk Reduction and Training using Simulation Based Tools - 12180

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Irin P.

2012-07-01

Process Modeling and Simulation (M and S) has been used for many years in manufacturing and similar domains, as part of an industrial engineer's tool box. Traditionally, however, this technique has been employed in small, isolated projects where models were created from scratch, often making it time and cost prohibitive. Newport News Shipbuilding (NNS) has recognized the value of this predictive technique and what it offers in terms of risk reduction, cost avoidance and on-schedule performance of highly complex work. To facilitate implementation, NNS has been maturing a process and the software to rapidly deploy and reuse M and Smore » based decision support tools in a variety of environments. Some examples of successful applications by NNS of this technique in the nuclear domain are a reactor refueling simulation based tool, a fuel handling facility simulation based tool and a tool for dynamic radiation exposure tracking. The next generation of M and S applications include expanding simulation based tools into immersive and interactive training. The applications discussed here take a tool box approach to creating simulation based decision support tools for maximum utility and return on investment. This approach involves creating a collection of simulation tools that can be used individually or integrated together for a larger application. The refueling simulation integrates with the fuel handling facility simulation to understand every aspect and dependency of the fuel handling evolutions. This approach translates nicely to other complex domains where real system experimentation is not feasible, such as nuclear fuel lifecycle and waste management. Similar concepts can also be applied to different types of simulation techniques. For example, a process simulation of liquid waste operations may be useful to streamline and plan operations, while a chemical model of the liquid waste composition is an important tool for making decisions with respect to waste disposition. Integrating these tools into a larger virtual system provides a tool for making larger strategic decisions. The key to integrating and creating these virtual environments is the software and the process used to build them. Although important steps in the direction of using simulation based tools for nuclear domain, the applications described here represent only a small cross section of possible benefits. The next generation of applications will, likely, focus on situational awareness and adaptive planning. Situational awareness refers to the ability to visualize in real time the state of operations. Some useful tools in this area are Geographic Information Systems (GIS), which help monitor and analyze geographically referenced information. Combined with such situational awareness capability, simulation tools can serve as the platform for adaptive planning tools. These are the tools that allow the decision maker to react to the changing environment in real time by synthesizing massive amounts of data into easily understood information. For the nuclear domains, this may mean creation of Virtual Nuclear Systems, from Virtual Waste Processing Plants to Virtual Nuclear Reactors. (authors)« less

Experimental methods for quenching structures in lunar-analog silicate melts: Variations as a function of quench media and composition

NASA Technical Reports Server (NTRS)

Dyar, M. D.

1985-01-01

Compositions analogous to lunar green, organge, and brown glasses were synthesized under consistent conditions, then quenched into a variety of different media when the samples were removed from the furnace. Iron valence and coordination are a direct function of quench media used, spanning the range from brine/ice (most effective quench), water, butyl phthalate, silicone oil, liquid nitrogen, highly reducing CO-CO2 gas, to air (least efficient quench). In the green and brown glasses, Fe(3+) in four-fold and six-fold coordination is observed in the slowest-quenched samples; Fe(2+) coordination varies directly with quench efficiency. Less pronounced changes were observed in the Ti-rich orange glass. Therefore the remote-sensed spectrum of a glass-bearing regolith on the Moon may be influenced by the process by which the glass cooled, and extreme caution must be used when comparing spectra of synthetic glass analogs with real lunar glasses.

Experimental methods for quenching structures in lunar-analog silicate melts - Variations as a function of quench media and composition

NASA Technical Reports Server (NTRS)

Dyar, M. D.

1984-01-01

Compositions analogous to lunar green, orange, and brown glasses were synthesized under consistent conditions, then quenched into a variety of different media when the samples were removed from the furnace. Iron valence and coordination are a direct function of quench media used, spanning the range from brine/ice (most effective quench), water, butyl phthalate, silicone oil, liquid nitrogen, highly reducing CO-CO2 gas, to air (least efficient quench). In the green and brown glasses, Fe(3+) in four-fold and six-fold coordination is observed in the slowest-quenched samples; Fe(2+) coordination varies directly with quench efficiency. Less pronounced changes were observed in the Ti-rich orange glass. Therefore the remote-sensed spectrum of a glass-bearing regolith on the moon may be influenced by the process by which the glass cooled, and extreme caution must be used when comparing spectra of synthetic glass analogs with real lunar glasses.

SU-F-T-164: Investigation of PRESAGE Formulation On Signal Quenching in a Proton Beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carroll, M; Alqathami, M; Ibbott, G

2016-06-15

Purpose: The radiochromic polyurethane PRESAGE by Heuris Pharma has had limited applications with protons because of a dose response dependence on LET resulting in signal quenching in the Bragg peak. This is due to the radical initiator, a halocarbon, radically recombining in high-LET irradiations. This study investigated the use of alternative halocarbons at various chemical concentrations to determine their significance in signal quenching. Methods: PRESAGE was manufactured in-house and cast in small volume cuvettes (1×1×4cm^3). Several compositions were evaluated to determine the influence of the radical initiator component. Mixtures contained one of two halocarbons, chloroform or bromoform, at concentrations ofmore » 5%/10%/15%(w/w). A large volume, cylindrical PRESAGE dosimeter made following the mixture described by Heuris Pharma, 4cm(D)×8.5cm(H), was irradiated with 200-MeV protons to study regions of low- and high-LET along a 10cm spread out Bragg peak isodose profile. Depths corresponding to regions of low quenching (<3%) and high quenching (>20%) were determined. These depths were used for cuvette placement in a solid water phantom. Samples of each formulation were placed at each depth and irradiated to doses between 0 and 10Gy. Results: The cuvettes indicated different levels of quenching for different radical initiator types, concentrations, and total doses. Chloroform formulations showed reduced quenching from 29%(5%-w/w) to 21%(15%-w/w) while bromoform reduced quenching from 27%(5%-w/w) to 17%(15%-w/w). The reduction in quenching was found to be non-linear with concentration of radical initiator. A quenching dose-dependency was also found that changed with formulation. In all cases, quenching was relatively consistent from 0–5Gy but increased at 10Gy. The quenching decreased as concentrations of radical initiator increased. Conclusion: The radical initiator component in PRESAGE is correlated with the signal quenching observed in proton irradiations and formulation adjustments show promise as a method of reducing this quenching. Future work will further investigate concentration limits and optimize the formulation. Grant number 5RO1CA100835.« less

Degassing of H2O in a phonolitic melt: A closer look at decompression experiments

NASA Astrophysics Data System (ADS)

Marxer, Holger; Bellucci, Philipp; Nowak, Marcus

2015-05-01

Melt degassing during magma ascent is controlled by the decompression rate and can be simulated in decompression experiments. H2O-bearing phonolitic melts were decompressed at a super-liquidus T of 1323 K in an internally heated argon pressure vessel, applying continuous decompression (CD) as well as to date commonly used step-wise decompression (SD) techniques to investigate the effect of decompression method on melt degassing. The hydrous melts were decompressed from 200 MPa at nominal decompression rates of 0.0028-1.7 MPa·s- 1. At final pressure (Pfinal), the samples were quenched rapidly at isobaric conditions with ~ 150 K·s- 1. The bubbles in the quenched samples are often deformed and dented. Flow textures in the glass indicate melt transport at high viscosity. We suggest that this observation is due to bubble shrinkage during quench. This general problem was mostly overlooked in the interpretation of experimentally degassed samples to date. Bubble shrinkage due to decreasing molar volume (Vm) of the exsolved H2O in the bubbles occurs during isobaric rapid quench until the melt is too viscous too relax. The decrease of Vm(H2O) during cooling at Pfinal of the experiments results in a decrease of the bubble volume by a shrinking factor Bs: At nominal decompression rates > 0.17 MPa·s- 1 and a Pfinal of 75 MPa, the decompression method has only minor influence on melt degassing. SD and CD result in high bubble number densities of 104-105 mm- 3. Fast P drop leads to immediate supersaturation with H2O in the melt. At such high nominal decompression rates, the diffusional transport of H2O is limited and therefore bubble nucleation is the predominant degassing process. The residual H2O contents in the melts decompressed to 75 MPa increase with nominal decompression rate. After homogeneous nucleation is triggered, CD rates ≤ 0.024 MPa·s- 1 facilitate continuous reduction of the supersaturation by H2O diffusion into previously nucleated bubbles. Bubble number densities of CD samples with low nominal decompression rates are several orders of magnitude lower than for SD experiments and the bubble diameters are larger. The reproducibility of MSD experiments with low nominal decompression rates is worse than for CD runs. Commonly used SD techniques are therefore not suitable to simulate melt degassing during continuous magma ascent with low ascent rates.

Quenching of p-Cyanophenylalanine Fluorescence by Various Anions.

PubMed

Pazos, Ileana M; Roesch, Rachel M; Gai, Feng

2013-03-20

To expand the spectroscopic utility of the non-natural amino acid p -cyanophenylalanine (Phe CN ), we examine the quenching efficiencies of a series of commonly encountered anions toward its fluorescence. We find that iodide exhibits an unusually large Stern-Volmer quenching constant, making it a convenient choice in Phe CN fluorescence quenching studies. Indeed, using the villin headpiece subdomain as a testbed we demonstrate that iodide quenching of Phe CN fluorescence offers a convenient means to reveal protein conformational heterogeneity. Furthermore, we show that the amino group of Phe CN strongly quenches its fluorescence, suggesting that Phe CN could be used as a local pH sensor.

Nano Precipitation and Hardening of Die-Quenched 6061 Aluminum Alloy.

PubMed

Utsunomiya, Hiroshi; Tada, Koki; Matsumoto, Ryo; Watanabe, Katsumi; Matsuda, Kenji

2018-03-01

Die quenching is applied to an age-hardenable aluminium alloys to obtain super-saturated solid solution. The application is advantageous because it can reduce number of manufacturing processes, and may increase strength by strain aging. If die quenching is realized in forging as well as sheet forming, it may widen industrial applicability further. In this study, Al-Mg-Si alloy AA6061 8 mm-thick billets were reduced 50% in height without cracks by die-quench forging. Supersaturated solid solution was successfully obtained. The die-quenched specimen shows higher hardness with nano precipitates at shorter aging time than the conventional water-quenched specimen.

Fluctuation-dissipation theorem in an isolated system of quantum dipolar bosons after a quench.

PubMed

Khatami, Ehsan; Pupillo, Guido; Srednicki, Mark; Rigol, Marcos

2013-08-02

We examine the validity of fluctuation-dissipation relations in isolated quantum systems taken out of equilibrium by a sudden quench. We focus on the dynamics of trapped hard-core bosons in one-dimensional lattices with dipolar interactions whose strength is changed during the quench. We find indications that fluctuation-dissipation relations hold if the system is nonintegrable after the quench, as well as if it is integrable after the quench if the initial state is an equilibrium state of a nonintegrable Hamiltonian. On the other hand, we find indications that they fail if the system is integrable both before and after quenching.

Cooling Rate Study of Nickel-Rich Material During Thermal Treatment and Quench

NASA Technical Reports Server (NTRS)

Thomas, Fransua; Murguia, Silvia Briseno (Editor)

2016-01-01

To investigate quench cracking that results from water quenching after heat treatment of binary and Ni-rich material, cooling rates of specimens were measured during quenching and hardness post-thermal treatment. For specific applications binary Ni-Ti is customarily thermally treated and quenched to attain desired mechanical properties and hardness. However, one problem emerging from this method is thermal cracking, either during the heat treatment process or during the specimen's application. This can result in material and equipment failure as well as financial losses. The objective of the study is to investigate the internal cooling rate of 60-NiTi during quenching and determine possible factors causing thermal cracking. Cubic (1 in.3) samples of both material were heat treated in air at 1000 deg C for 2 hrs and quenched in room temperature water using two methods: (1) dropped in the water and (2) agitated in the water. Hardness of the two fore-mentioned methods was measured post heat treatment. Results indicate that the quenching method had an effect on cooling rate during quenching but hardness was observed to be essentially the same through the thickness of the samples.

Quench Crucibles Reinforced with Metal

NASA Technical Reports Server (NTRS)

Holmes, Richard R.; Carrasquillo, Edgar; O'Dell, J. Scott; McKehnie, N.

2008-01-01

Improved crucibles consisting mainly of metal-reinforced ceramic ampules have been developed for use in experiments in which material specimens are heated in the crucibles to various high temperatures, then quenched by, for example, plunging the crucibles into water at room temperature. In a traditional quench crucible, the gap between the ampule and the metal cartridge impedes the transfer of heat to such a degree that the quench rate (the rate of cooling of the specimen) can be too low to produce the desired effect in the specimen. One can increase the quench rate by eliminating the metal cartridge to enable direct quenching of the ampule, but then the thermal shock of direct quenching causes cracking of the ampule. In a quench crucible of the present improved type, there is no gap and no metal cartridge in the traditional sense. Instead, there is an overlay of metal in direct contact with the ampule, as shown on the right side of the figure. Because there is no gap between the metal overlay and the ampule, the heat-transfer rate can be much greater than it is in a traditional quench crucible. The metal overlay also reinforces the ampule against cracking.

Short initial length quench on CICC of ITER TF coils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nicollet, S.; Ciazynski, D.; Duchateau, J.-L.

Previous quench studies performed for the International Thermonuclear Experimental Reactor (ITER) Toroidal Field (TF) Coils have led to identify two extreme families of quench: first 'severe' quenches over long initial lengths in high magnetic field, and second smooth quenches over short initial lengths in low field region. Detailed analyses and results on smooth quench propagation and detectability on one TF Cable In Conduit Conductor (CICC) with a lower propagation velocity are presented here. The influence of the initial quench energy is shown and results of computations with either a Fast Discharge (FD) of the magnet or without (failure of themore » voltage quench detection system) are reported. The influence of the central spiral of the conductor on the propagation velocity is also detailed. In the cases of a regularly triggered FD, the hot spot temperature criterion of 150 K (with helium and jacket) is fulfilled for an initial quench length of 1 m, whereas this criterion is exceed (Tmax ≈ 200 K) for an extremely short length of 5 cm. These analyses were carried out using both the Supermagnet(trade mark, serif) and Venecia codes and the comparisons of the results are also discussed.« less

Tools and Equipment Modeling for Automobile Interactive Assembling Operating Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu Dianliang; Zhu Hongmin; Shanghai Key Laboratory of Advance Manufacturing Environment

Tools and equipment play an important role in the simulation of virtual assembly, especially in the assembly process simulation and plan. Because of variety in function and complexity in structure and manipulation, the simulation of tools and equipments remains to be a challenge for interactive assembly operation. Based on analysis of details and characteristics of interactive operations for automobile assembly, the functional requirement for tools and equipments of automobile assembly is given. Then, a unified modeling method for information expression and function realization of general tools and equipments is represented, and the handling methods of manual, semi-automatic, automatic tools andmore » equipments are discussed. Finally, the application in assembly simulation of rear suspension and front suspension of Roewe 750 automobile is given. The result shows that the modeling and handling methods are applicable in the interactive simulation of various tools and equipments, and can also be used for supporting assembly process planning in virtual environment.« less

Low NO.sub.x combustor

DOEpatents

Taylor, Jack R.

1987-01-01

A combustor having an annular first stage, a generally cylindrically-shaped second stage, and an annular conduit communicably connecting the first and second stages. The conduit has a relatively small annular height and a large number of quench holes in the walls thereof such that quench air injected into the conduit through the quench holes will mix rapidly with, or quench, the combustion gases flowing through the conduit. The rapid quenching reduces the amount of NO.sub.x produced in the combustor.

Single photon detection with self-quenching multiplication

NASA Technical Reports Server (NTRS)

Zheng, Xinyu (Inventor); Cunningham, Thomas J. (Inventor); Pain, Bedabrata (Inventor)

2011-01-01

A photoelectronic device and an avalanche self-quenching process for a photoelectronic device are described. The photoelectronic device comprises a nanoscale semiconductor multiplication region and a nanoscale doped semiconductor quenching structure including a depletion region and an undepletion region. The photoelectronic device can act as a single photon detector or a single carrier multiplier. The avalanche self-quenching process allows electrical field reduction in the multiplication region by movement of the multiplication carriers, thus quenching the avalanche.

Effect of Bath Temperature on Cooling Performance of Molten Eutectic NaNO3-KNO3 Quench Medium for Martempering of Steels

NASA Astrophysics Data System (ADS)

Pranesh Rao, K. M.; Narayan Prabhu, K.

2017-10-01

Martempering is an industrial heat treatment process that requires a quench bath that can operate without undergoing degradation in the temperature range of 423 K to 873 K (150 °C to 600 °C). The quench bath is expected to cool the steel part from the austenizing temperature to quench bath temperature rapidly and uniformly. Molten eutectic NaNO3-KNO3 mixture has been widely used in industry to martemper steel parts. In the present work, the effect of quench bath temperature on the cooling performance of a molten eutectic NaNO3-KNO3 mixture has been studied. An Inconel ASTM D-6200 probe was heated to 1133 K (860 °C) and subsequently quenched in the quench bath maintained at different temperatures. Spatially dependent transient heat flux at the metal-quenchant interface for each bath temperature was calculated using inverse heat conduction technique. Heat transfer occurred only in two stages, namely, nucleate boiling and convective cooling. The mean peak heat flux ( q max) decreased with increase in quench bath temperature, whereas the mean surface temperature corresponding to q max and mean surface temperature at the start of convective cooling stage increased with increase in quench bath temperature. The variation in normalized cooling parameter t 85 along the length of the probe increased with increase in quench bath temperature.

Quantum Quench Dynamics

NASA Astrophysics Data System (ADS)

Mitra, Aditi

2018-03-01

Quench dynamics is an active area of study encompassing condensed matter physics and quantum information, with applications to cold-atomic gases and pump-probe spectroscopy of materials. Recent theoretical progress in studying quantum quenches is reviewed. Quenches in interacting one-dimensional systems as well as systems in higher spatial dimensions are covered. The appearance of nontrivial steady states following a quench in exactly solvable models is discussed, and the stability of these states to perturbations is described. Proper conserving approximations needed to capture the onset of thermalization at long times are outlined. The appearance of universal scaling for quenches near critical points and the role of the renormalization group in capturing the transient regime are reviewed. Finally, the effect of quenches near critical points on the dynamics of entanglement entropy and entanglement statistics is discussed. The extraction of critical exponents from the entanglement statistics is outlined.

Challenges of NDE Simulation Tool Challenges of NDE Simulation Tool

NASA Technical Reports Server (NTRS)

Leckey, Cara A. C.; Juarez, Peter D.; Seebo, Jeffrey P.; Frank, Ashley L.

2015-01-01

Realistic nondestructive evaluation (NDE) simulation tools enable inspection optimization and predictions of inspectability for new aerospace materials and designs. NDE simulation tools may someday aid in the design and certification of advanced aerospace components; potentially shortening the time from material development to implementation by industry and government. Furthermore, modeling and simulation are expected to play a significant future role in validating the capabilities and limitations of guided wave based structural health monitoring (SHM) systems. The current state-of-the-art in ultrasonic NDE/SHM simulation cannot rapidly simulate damage detection techniques for large scale, complex geometry composite components/vehicles with realistic damage types. This paper discusses some of the challenges of model development and validation for composites, such as the level of realism and scale of simulation needed for NASA' applications. Ongoing model development work is described along with examples of model validation studies. The paper will also discuss examples of the use of simulation tools at NASA to develop new damage characterization methods, and associated challenges of validating those methods.

The Global and Radial Stellar Mass Assembly of Milky Way-sized Galaxies

NASA Astrophysics Data System (ADS)

Avila-Reese, Vladimir; González-Samaniego, Alejandro; Colín, Pedro; Ibarra-Medel, Héctor; Rodríguez-Puebla, Aldo

2018-02-01

We study the global and radial stellar mass assembly of eight zoomed-in Milky Way (MW)-sized galaxies produced in hydrodynamics cosmological simulations. The disk-dominated galaxies (four) show a fast initial stellar mass growth in the innermost parts, driven mostly by in situ star formation (SF), but since z ∼ 2‑1, the SF has entered a long-term quenching phase. The outer regions follow this trend but more gently, as they are more external. As a result, the radial stellar mass growth is highly inside-out due to both inside-out structural growth and inside-out SF quenching. The half-mass radius evolves fast; for instance, {R}0.5(z = 1) < 0.5 {R}0.5 (z = 0). Two other runs resemble lenticular galaxies. One also shows a pronounced inside-out growth, and the other one presents a nearly uniform radial mass assembly. The other two galaxies suffered late major mergers. Their normalized radial mass growth histories (MGHs) are very close, but with periods of outside-in assembly during or after the mergers. For all of the simulations, the archaeological radial MGHs calculated from the z = 0 stellar particle age distribution are similar to current MGHs, which shows that the mass assembly by ex situ stars and the radial mass transport do not significantly change their radial mass distributions. Our results agree qualitatively with observational inferences from the fossil record method applied to a survey of local galaxies and from look-back observations of progenitors of MW-sized galaxies. However, the inside-out growth mode is more pronounced, and the {R}0.5 growth is faster in simulations than in observational inferences.

Design of a highly selective quenched activity-based probe and its application in dual color imaging studies of cathepsin S activity localization.

PubMed

Oresic Bender, Kristina; Ofori, Leslie; van der Linden, Wouter A; Mock, Elliot D; Datta, Gopal K; Chowdhury, Somenath; Li, Hao; Segal, Ehud; Sanchez Lopez, Mateo; Ellman, Jonathan A; Figdor, Carl G; Bogyo, Matthew; Verdoes, Martijn

2015-04-15

The cysteine cathepsins are a group of 11 proteases whose function was originally believed to be the degradation of endocytosed material with a high degree of redundancy. However, it has become clear that these enzymes are also important regulators of both health and disease. Thus, selective tools that can discriminate between members of this highly related class of enzymes will be critical to further delineate the unique biological functions of individual cathepsins. Here we present the design and synthesis of a near-infrared quenched activity-based probe (qABP) that selectively targets cathepsin S which is highly expressed in immune cells. Importantly, this high degree of selectivity is retained both in vitro and in vivo. In combination with a new green-fluorescent pan-reactive cysteine cathepsin qABP we performed dual color labeling studies in bone marrow-derived immune cells and identified vesicles containing exclusively cathepsin S activity. This observation demonstrates the value of our complementary cathepsin probes and provides evidence for the existence of specific localization of cathepsin S activity in dendritic cells.

Characterization of the interfacial heat transfer coefficient for hot stamping processes

NASA Astrophysics Data System (ADS)

Luan, Xi; Liu, Xiaochuan; Fang, Haomiao; Ji, Kang; El Fakir, Omer; Wang, LiLiang

2016-08-01

In hot stamping processes, the interfacial heat transfer coefficient (IHTC) between the forming tools and hot blank is an essential parameter which determines the quenching rate of the process and hence the resulting material microstructure. The present work focuses on the characterization of the IHTC between an aluminium alloy 7075-T6 blank and two different die materials, cast iron (G3500) and H13 die steel, at various contact pressures. It was found that the IHTC between AA7075 and cast iron had values 78.6% higher than that obtained between AA7075 and H13 die steel. Die materials and contact pressures had pronounced effects on the IHTC, suggesting that the IHTC can be used to guide the selection of stamping tool materials and the precise control of processing parameters.

Commissioning Cornell OSTs for SRF cavity testing at Jlab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eremeev, Grigory

2011-07-01

Understanding the current quench limitations in SRF cavities is a topic essential for any SRF accelerator that requires high fields. This understanding crucially depends on correct and precise quench identification. Second sound quench detection in superfluid liquid helium with oscillating superleak transducers is a technique recently applied at Cornell University as a fast and versatile method for quench identification in SRF cavities. Having adopted Cornell design, we report in this contribution on our experience with OST for quench identification in different cavities at JLab.

Silicon material task. Part 3: Low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

Roques, R. A.; Coldwell, D. M.

1977-01-01

The feasibility of a process for carbon reduction of low impurity silica in a plasma heat source was investigated to produce low-cost solar-grade silicon. Theoretical aspects of the reaction chemistry were studied with the aid of a computer program using iterative free energy minimization. These calculations indicate a threshold temperature exists at 2400 K below which no silicon is formed. The computer simulation technique of molecular dynamics was used to study the quenching of product species.

A Fracture Mechanics Approach to Thermal Shock Investigation in Alumina-Based Refractory

NASA Astrophysics Data System (ADS)

Volkov-Husović, T.; Heinemann, R. Jančić; Mitraković, D.

2008-02-01

The thermal shock behavior of large grain size, alumina-based refractories was investigated experimentally using a standard water quench test. A mathematical model was employed to simulate the thermal stability behavior. Behavior of the samples under repeated thermal shock was monitored using ultrasonic measurements of dynamic Young's modulus. Image analysis was used to observe the extent of surface degradation. Analysis of the obtained results for the behavior of large grain size samples under conditions of rapid temperature changes is given.

Erratum: Evidence of b -jet quenching in PbPb collisions at s N N = 2.76 TeV [Phys. Rev. Lett. 113 , 132301 (2014)

DOE PAGES

Chatrchyan, S.

2015-07-10

In our Letter, there was a component of the statistical uncertainty from the simulated PbPb Monte Carlo samples. This uncertainty was not propagated to all of the results. Figures 3 and 4 have been updated to reflect this source of uncertainty. In this case, the statistical uncertainties remain smaller than the systematic uncertainties in all cases such that the conclusions of the Letter are unaltered.

Orientational dynamics and dye-DNA interactions in a dye-labeled DNA aptamer.

PubMed

Unruh, Jay R; Gokulrangan, Giridharan; Lushington, G H; Johnson, Carey K; Wilson, George S

2005-05-01

We report the picosecond and nanosecond timescale rotational dynamics of a dye-labeled DNA oligonucleotide or "aptamer" designed to bind specifically to immunoglobulin E. Rotational dynamics in combination with fluorescence lifetime measurements provide information about dye-DNA interactions. Comparison of Texas Red (TR), fluorescein, and tetramethylrhodamine (TAMRA)-labeled aptamers reveals surprising differences with significant implications for biophysical studies employing such conjugates. Time-resolved anisotropy studies demonstrate that the TR- and TAMRA-aptamer anisotropy decays are dominated by the overall rotation of the aptamer, whereas the fluorescein-aptamer anisotropy decay displays a subnanosecond rotational correlation time much shorter than that expected for the overall rotation of the aptamer. Docking and molecular dynamics simulations suggest that the low mobility of TR is a result of binding in the groove of the DNA helix. Additionally, associated anisotropy analysis of the TAMRA-aptamer reveals both quenched and unquenched states that experience significant coupling to the DNA motion. Therefore, quenching of TAMRA by guanosine must depend on the configuration of the dye bound to the DNA. The strong coupling of TR to the rotational dynamics of the DNA aptamer, together with the absence of quenching of its fluorescence by DNA, makes it a good probe of DNA orientational dynamics. The understanding of the nature of dye-DNA interactions provides the basis for the development of bioconjugates optimized for specific biophysical measurements and is important for the sensitivity of anisotropy-based DNA-protein interaction studies employing such conjugates.

Orientational Dynamics and Dye-DNA Interactions in a Dye-Labeled DNA Aptamer

PubMed Central

Unruh, Jay R.; Gokulrangan, Giridharan; Lushington, G. H.; Johnson, Carey K.; Wilson, George S.

2005-01-01

We report the picosecond and nanosecond timescale rotational dynamics of a dye-labeled DNA oligonucleotide or “aptamer” designed to bind specifically to immunoglobulin E. Rotational dynamics in combination with fluorescence lifetime measurements provide information about dye-DNA interactions. Comparison of Texas Red (TR), fluorescein, and tetramethylrhodamine (TAMRA)-labeled aptamers reveals surprising differences with significant implications for biophysical studies employing such conjugates. Time-resolved anisotropy studies demonstrate that the TR- and TAMRA-aptamer anisotropy decays are dominated by the overall rotation of the aptamer, whereas the fluorescein-aptamer anisotropy decay displays a subnanosecond rotational correlation time much shorter than that expected for the overall rotation of the aptamer. Docking and molecular dynamics simulations suggest that the low mobility of TR is a result of binding in the groove of the DNA helix. Additionally, associated anisotropy analysis of the TAMRA-aptamer reveals both quenched and unquenched states that experience significant coupling to the DNA motion. Therefore, quenching of TAMRA by guanosine must depend on the configuration of the dye bound to the DNA. The strong coupling of TR to the rotational dynamics of the DNA aptamer, together with the absence of quenching of its fluorescence by DNA, makes it a good probe of DNA orientational dynamics. The understanding of the nature of dye-DNA interactions provides the basis for the development of bioconjugates optimized for specific biophysical measurements and is important for the sensitivity of anisotropy-based DNA-protein interaction studies employing such conjugates. PMID:15731389

Quenching or Bursting: Star Formation Acceleration—A New Methodology for Tracing Galaxy Evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, D. Christopher; Darvish, Behnam; Seibert, Mark

We introduce a new methodology for the direct extraction of galaxy physical parameters from multiwavelength photometry and spectroscopy. We use semianalytic models that describe galaxy evolution in the context of large-scale cosmological simulation to provide a catalog of galaxies, star formation histories, and physical parameters. We then apply models of stellar population synthesis and a simple extinction model to calculate the observable broadband fluxes and spectral indices for these galaxies. We use a linear regression analysis to relate physical parameters to observed colors and spectral indices. The result is a set of coefficients that can be used to translate observedmore » colors and indices into stellar mass, star formation rate, and many other parameters, including the instantaneous time derivative of the star formation rate, which we denote the Star Formation Acceleration (SFA), We apply the method to a test sample of galaxies with GALEX photometry and SDSS spectroscopy, deriving relationships between stellar mass, specific star formation rate, and SFA. We find evidence for a mass-dependent SFA in the green valley, with low-mass galaxies showing greater quenching and higher-mass galaxies greater bursting. We also find evidence for an increase in average quenching in galaxies hosting an active galactic nucleus. A simple scenario in which lower-mass galaxies accrete and become satellite galaxies, having their star-forming gas tidally and/or ram-pressure stripped, while higher-mass galaxies receive this gas and react with new star formation, can qualitatively explain our results.« less

Radiance limits of ceramic phosphors under high excitation fluxes

NASA Astrophysics Data System (ADS)

Lenef, Alan; Kelso, John; Zheng, Yi; Tchoul, Maxim

2013-09-01

Ceramic phosphors, excited by high radiance pump sources, offer considerable potential for high radiance conversion. Interestingly, thermodynamic arguments suggest that the radiance of the luminescent spot can even exceed that of the incoming light source. In practice, however, thermal quenching and (non-thermal) optical saturation limit the maximum attainable radiance of the luminescent source. We present experimental data for Ce:YAG and Ce:GdYAG ceramics in which these limits have been investigated. High excitation fluxes are achieved using laser pumping. Optical pumping intensities exceeding 100W/mm2 have been shown to produce only modest efficiency depreciation at low overall pump powers because of the short Ce3+ lifetime, although additional limitations exist. When pump powers are higher, heat-transfer bottlenecks within the ceramic and heat-sink interfaces limit maximum pump intensities. We find that surface temperatures of these laser-pumped ceramics can reach well over 150°C, causing thermal-quenching losses. We also find that in some cases, the loss of quantum efficiency with increasing temperature can cause a thermal run-away effect, resulting in a rapid loss in converted light, possibly over-heating the sample or surrounding structures. While one can still obtain radiances on the order of many W/mm2/sr, temperature quenching effects ultimately limit converted light radiance. Finally, we use the diffusion-approximation radiation transport models and rate equation models to simulate some of these nonlinear optical pumping and heating effects in high-scattering ceramics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Shang-Min; Grosheintz, Luc; Kitzmann, Daniel

We present an open-source and validated chemical kinetics code for studying hot exoplanetary atmospheres, which we name VULCAN. It is constructed for gaseous chemistry from 500 to 2500 K, using a reduced C–H–O chemical network with about 300 reactions. It uses eddy diffusion to mimic atmospheric dynamics and excludes photochemistry. We have provided a full description of the rate coefficients and thermodynamic data used. We validate VULCAN by reproducing chemical equilibrium and by comparing its output versus the disequilibrium-chemistry calculations of Moses et al. and Rimmer and Helling. It reproduces the models of HD 189733b and HD 209458b by Mosesmore » et al., which employ a network with nearly 1600 reactions. We also use VULCAN to examine the theoretical trends produced when the temperature–pressure profile and carbon-to-oxygen ratio are varied. Assisted by a sensitivity test designed to identify the key reactions responsible for producing a specific molecule, we revisit the quenching approximation and find that it is accurate for methane but breaks down for acetylene, because the disequilibrium abundance of acetylene is not directly determined by transport-induced quenching, but is rather indirectly controlled by the disequilibrium abundance of methane. Therefore we suggest that the quenching approximation should be used with caution and must always be checked against a chemical kinetics calculation. A one-dimensional model atmosphere with 100 layers, computed using VULCAN, typically takes several minutes to complete. VULCAN is part of the Exoclimes Simulation Platform (ESP; exoclime.net) and publicly available at https://github.com/exoclime/VULCAN.« less

The Bayesian reconstruction of the in-medium heavy quark potential from lattice QCD and its stability

NASA Astrophysics Data System (ADS)

Burnier, Yannis; Kaczmarek, Olaf; Rothkopf, Alexander

2016-01-01

We report recent results of a non-perturbative determination of the static heavy-quark potential in quenched and dynamical lattice QCD at finite temperature. The real and imaginary part of this complex quantity are extracted from the spectral function of Wilson line correlators in Coulomb gauge. To obtain spectral information from Euclidean time numerical data, our study relies on a novel Bayesian prescription that differs from the Maximum Entropy Method. We perform simulations on quenched 323 × Nτ (β = 7.0, ξ = 3.5) lattices with Nτ = 24, …, 96, which cover 839MeV ≥ T ≥ 210MeV. To investigate the potential in a quark-gluon plasma with light u,d and s quarks we utilize Nf = 2 + 1 ASQTAD lattices with ml = ms/20 by the HotQCD collaboration, giving access to temperatures between 286MeV ≥ T ≥ 148MeV. The real part of the potential exhibits a clean transition from a linear, confining behavior in the hadronic phase to a Debye screened form above deconfinement. Interestingly its values lie close to the color singlet free energies in Coulomb gauge at all temperatures. We estimate the imaginary part on quenched lattices and find that it is of the same order of magnitude as in hard-thermal loop perturbation theory. From among all the systematic checks carried out in our study, we discuss explicitly the dependence of the result on the default model and the number of datapoints.

Nonlinear analysis for dual-frequency concurrent energy harvesting

NASA Astrophysics Data System (ADS)

Yan, Zhimiao; Lei, Hong; Tan, Ting; Sun, Weipeng; Huang, Wenhu

2018-05-01

The dual-frequency responses of the hybrid energy harvester undergoing the base excitation and galloping were analyzed numerically. In this work, an approximate dual-frequency analytical method is proposed for the nonlinear analysis of such a system. To obtain the approximate analytical solutions of the full coupled distributed-parameter model, the forcing interactions is first neglected. Then, the electromechanical decoupled governing equation is developed using the equivalent structure method. The hybrid mechanical response is finally separated to be the self-excited and forced responses for deriving the analytical solutions, which are confirmed by the numerical simulations of the full coupled model. The forced response has great impacts on the self-excited response. The boundary of Hopf bifurcation is analytically determined by the onset wind speed to galloping, which is linearly increased by the electrical damping. Quenching phenomenon appears when the increasing base excitation suppresses the galloping. The theoretical quenching boundary depends on the forced mode velocity. The quenching region increases with the base acceleration and electrical damping, but decreases with the wind speed. Superior to the base-excitation-alone case, the existence of the aerodynamic force protects the hybrid energy harvester at resonance from damages caused by the excessive large displacement. From the view of the harvested power, the hybrid system surpasses the base-excitation-alone system or the galloping-alone system. This study advances our knowledge on intrinsic nonlinear dynamics of the dual-frequency energy harvesting system by taking advantage of the analytical solutions.

Quenching or Bursting: Star Formation Acceleration—A New Methodology for Tracing Galaxy Evolution

NASA Astrophysics Data System (ADS)

Martin, D. Christopher; Gonçalves, Thiago S.; Darvish, Behnam; Seibert, Mark; Schiminovich, David

2017-06-01

We introduce a new methodology for the direct extraction of galaxy physical parameters from multiwavelength photometry and spectroscopy. We use semianalytic models that describe galaxy evolution in the context of large-scale cosmological simulation to provide a catalog of galaxies, star formation histories, and physical parameters. We then apply models of stellar population synthesis and a simple extinction model to calculate the observable broadband fluxes and spectral indices for these galaxies. We use a linear regression analysis to relate physical parameters to observed colors and spectral indices. The result is a set of coefficients that can be used to translate observed colors and indices into stellar mass, star formation rate, and many other parameters, including the instantaneous time derivative of the star formation rate, which we denote the Star Formation Acceleration (SFA), We apply the method to a test sample of galaxies with GALEX photometry and SDSS spectroscopy, deriving relationships between stellar mass, specific star formation rate, and SFA. We find evidence for a mass-dependent SFA in the green valley, with low-mass galaxies showing greater quenching and higher-mass galaxies greater bursting. We also find evidence for an increase in average quenching in galaxies hosting an active galactic nucleus. A simple scenario in which lower-mass galaxies accrete and become satellite galaxies, having their star-forming gas tidally and/or ram-pressure stripped, while higher-mass galaxies receive this gas and react with new star formation, can qualitatively explain our results.

Rapid Quench in an Electrostatic Levitator

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Rogers, Jan R.; Matson, Douglas M.

2016-01-01

The Electrostatic Levitation (ESL) Laboratory at the NASA Marshall Space Flight Center (MSFC) is a unique facility for investigators studying high-temperature materials. The ESL laboratory's main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy, as a quench medium. Thereby allowing rapid quenching of undercooled liquid metals. Up to eight quench vessels can be loaded into a wheel inside the chamber that is indexed with control software. The system has been tested successfully with samples of zirconium, iron-cobalt alloys, titanium-zirconium-nickel alloys, and a silicon-cobalt alloy. This new rapid quench system will allow materials science studies of undercooled materials and new materials development. In this presentation, the system is described and some initial results are presented.

Rapid Quench in an Electrostatic Levitator

NASA Technical Reports Server (NTRS)

SanSoucie, Michael P.; Rogers, Jan R.; Matson, Michael M.

2016-01-01

The Electrostatic Levitation (ESL) Laboratory at the NASA Marshall Space Flight Center (MSFC) is a unique facility for investigators studying high-temperature materials. The ESL laboratory’s main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy, as a quench medium. Thereby allowing rapid quenching of undercooled liquid metals. Up to eight quench vessels can be loaded into a wheel inside the chamber that is indexed with control software. The system has been tested successfully with samples of zirconium, iron-cobalt alloys, iron-chromium-nickel, titanium-zirconium-nickel alloys, and a silicon-cobalt alloy. This new rapid quench system will allow materials science studies of undercooled materials and new materials development. The system is described and some initial results are presented.

40 CFR 86.327-79 - Quench checks; NOX analyzer.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Quench checks; NOX analyzer. (a) Perform the reaction chamber quench check for each model of high vacuum reaction chamber analyzer prior to initial use. (b) Perform the reaction chamber quench check for each new analyzer that has an ambient pressure or “soft vacuum” reaction chamber prior to initial use. Additionally...

40 CFR 86.327-79 - Quench checks; NOX analyzer.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Quench checks; NOX analyzer. (a) Perform the reaction chamber quench check for each model of high vacuum reaction chamber analyzer prior to initial use. (b) Perform the reaction chamber quench check for each new analyzer that has an ambient pressure or “soft vacuum” reaction chamber prior to initial use. Additionally...

Implementation of depolarization due to beam-beam effects in the beam-beam interaction simulation tool GUINEA-PIG++

NASA Astrophysics Data System (ADS)

Rimbault, C.; Le Meur, G.; Blampuy, F.; Bambade, P.; Schulte, D.

2009-12-01

Depolarization is a new feature in the beam-beam simulation tool GUINEA-PIG++ (GP++). The results of this simulation are studied and compared with another beam-beam simulation tool, CAIN, considering different beam parameters for the International Linear Collider (ILC) with a centre-of-mass energy of 500 GeV.

The Role of Diffusivity Quenching in Flux-transport Dynamo Models

NASA Astrophysics Data System (ADS)

Guerrero, Gustavo; Dikpati, Mausumi; de Gouveia Dal Pino, Elisabete M.

2009-08-01

In the nonlinear phase of a dynamo process, the back-reaction of the magnetic field upon the turbulent motion results in a decrease of the turbulence level and therefore in a suppression of both the magnetic field amplification (the α-quenching effect) and the turbulent magnetic diffusivity (the η-quenching effect). While the former has been widely explored, the effects of η-quenching in the magnetic field evolution have rarely been considered. In this work, we investigate the role of the suppression of diffusivity in a flux-transport solar dynamo model that also includes a nonlinear α-quenching term. Our results indicate that, although for α-quenching the dependence of the magnetic field amplification with the quenching factor is nearly linear, the magnetic field response to η-quenching is nonlinear and spatially nonuniform. We have found that the magnetic field can be locally amplified in this case, forming long-lived structures whose maximum amplitude can be up to ~2.5 times larger at the tachocline and up to ~2 times larger at the center of the convection zone than in models without quenching. However, this amplification leads to unobservable effects and to a worse distribution of the magnetic field in the butterfly diagram. Since the dynamo cycle period increases when the efficiency of the quenching increases, we have also explored whether the η-quenching can cause a diffusion-dominated model to drift into an advection-dominated regime. We have found that models undergoing a large suppression in η produce a strong segregation of magnetic fields that may lead to unsteady dynamo-oscillations. On the other hand, an initially diffusion-dominated model undergoing a small suppression in η remains in the diffusion-dominated regime.

Quenching and anisotropy of hydromagnetic turbulent transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karak, Bidya Binay; Brandenburg, Axel; Rheinhardt, Matthias

2014-11-01

Hydromagnetic turbulence affects the evolution of large-scale magnetic fields through mean-field effects like turbulent diffusion and the α effect. For stronger fields, these effects are usually suppressed or quenched, and additional anisotropies are introduced. Using different variants of the test-field method, we determine the quenching of the turbulent transport coefficients for the forced Roberts flow, isotropically forced non-helical turbulence, and rotating thermal convection. We see significant quenching only when the mean magnetic field is larger than the equipartition value of the turbulence. Expressing the magnetic field in terms of the equipartition value of the quenched flows, we obtain for themore » quenching exponents of the turbulent magnetic diffusivity about 1.3, 1.1, and 1.3 for Roberts flow, forced turbulence, and convection, respectively. However, when the magnetic field is expressed in terms of the equipartition value of the unquenched flows, these quenching exponents become about 4, 1.5, and 2.3, respectively. For the α effect, the exponent is about 1.3 for the Roberts flow and 2 for convection in the first case, but 4 and 3, respectively, in the second. In convection, the quenching of turbulent pumping follows the same power law as turbulent diffusion, while for the coefficient describing the Ω×J effect nearly the same quenching exponent is obtained as for α. For forced turbulence, turbulent diffusion proportional to the second derivative along the mean magnetic field is quenched much less, especially for larger values of the magnetic Reynolds number. However, we find that in corresponding axisymmetric mean-field dynamos with dominant toroidal field the quenched diffusion coefficients are the same for the poloidal and toroidal field constituents.« less

THE QUENCHING TIMESCALE AND QUENCHING RATE OF GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lian, Jianhui; Kong, Xu; Yan, Renbin

2016-11-20

The average star formation rate (SFR) in galaxies has been declining since the redshift of 2. A fraction of galaxies quench and become quiescent. We constrain two key properties of the quenching process: the quenching timescale and the quenching rate among galaxies. We achieve this by analyzing the galaxy number density profile in NUV- u color space and the distribution in NUV- u versus u - i color–color diagram with a simple toy-model framework. We focus on galaxies in three mass bins between 10{sup 10} and 10{sup 10.6} M {sub ⊙}. In the NUV- u versus u - i color–colormore » diagram, the red u - i galaxies exhibit a different slope from the slope traced by the star-forming galaxies. This angled distribution and the number density profile of galaxies in NUV- u space strongly suggest that the decline of the SFR in galaxies has to accelerate before they turn quiescent. We model this color–color distribution with a two-phase exponential decline star formation history. The models with an e-folding time in the second phase (the quenching phase) of 0.5 Gyr best fit the data. We further use the NUV- u number density profile to constrain the quenching rate among star-forming galaxies as a function of mass. Adopting an e-folding time of 0.5 Gyr in the second phase (or the quenching phase), we found the quenching rate to be 19%/Gyr, 25%/Gyr and 33%/Gyr for the three mass bins. These are upper limits of the quenching rate as the transition zone could also be populated by rejuvenated red-sequence galaxies.« less

Spectrum simulation in DTSA-II.

PubMed

Ritchie, Nicholas W M

2009-10-01

Spectrum simulation is a useful practical and pedagogical tool. Particularly with complex samples or trace constituents, a simulation can help to understand the limits of the technique and the instrument parameters for the optimal measurement. DTSA-II, software for electron probe microanalysis, provides both easy to use and flexible tools for simulating common and less common sample geometries and materials. Analytical models based on (rhoz) curves provide quick simulations of simple samples. Monte Carlo models based on electron and X-ray transport provide more sophisticated models of arbitrarily complex samples. DTSA-II provides a broad range of simulation tools in a framework with many different interchangeable physical models. In addition, DTSA-II provides tools for visualizing, comparing, manipulating, and quantifying simulated and measured spectra.

Thermal Quenching of Photoluminescence in ZnO and GaN

NASA Astrophysics Data System (ADS)

Albarakati, Nahla Mubarak

Investigation of the thermal quenching of photoluminescence (PL) in semiconductors provides valuable information on identity and characteristics of point defects in these materials, which helps to better understand and improve the properties of semiconductor materials and devices. Abrupt and tunable thermal quenching (ATQ) of PL is a relatively new phenomenon with an unusual behavior of PL. This mechanism was able to explain what a traditional model failed to explain. Usually, in traditional model used to explain "normal" quenching, the slope of PL quenching in the Arrhenius plot determines the ionization energy of the defect causing the PL band. However, in abrupt quenching when the intensity of PL decreases by several orders of magnitude within a small range of temperature, the slope in the Arrhenius plot has no relation to the ionization energy of any defect. It is not known a priori if the thermal quenching of a particular PL band is normal or abrupt and tunable. Studying new cases of unusual thermal quenching, classifying and explaining them helps to predict new cases and understand deeper the ATQ mechanism of PL thermal quenching. Very few examples of abrupt and tunable quenching of PL in semiconductors can be found in literature. The abrupt and tunable thermal quenching, reported here for the first time for high-resistivity ZnO, provides an evidence to settle the dispute concerning the energy position of the Li Zn acceptor. In high-resistivity GaN samples, the common PL bands related to defects are the yellow luminescence (YL) band and a broad band in the blue spectral region (BL2). In this work, we report for the first time the observation of abrupt and tunable thermal quenching of the YL band in GaN. The activation energies for the YL and BL2 bands calculated through the new mechanism show agreement with the reported values. From this study we predict that the ATQ phenomenon is quite common for high-resistivity semiconductors.

On the fast quenching of young low-mass galaxies up to z ˜ 0.6. New spotlight on the lead role of environment

NASA Astrophysics Data System (ADS)

Moutard, Thibaud; Sawicki, Marcin; Arnouts, Stéphane; Golob, Anneya; Malavasi, Nicola; Adami, Christophe; Coupon, Jean; Ilbert, Olivier

2018-06-01

We investigate the connection between environment and the different quenching channels that galaxies are prone to follow in the rest-frame NUVrK colour diagram, as identified by Moutard et al. (2016b). Namely, the fast quenching channel followed by young low-mass galaxies and the slow quenching channel followed by old high-mass ones. We make use of the >22 deg2 covered the VIPERS Multi-Lambda Survey (VIPERS-MLS) to select a galaxy sample complete down to stellar masses of M* > 109.4M⊙ up to z ˜ 0.65 (M* > 108.8M⊙ up to z ˜ 0.5) and including 33,500 (43,000) quiescent galaxies properly selected at 0.2 < z < 0.65, while being characterized by reliable photometric redshifts (σδz/(1 + z) ≤ 0.04) that we use to measure galaxy local densities. We find that (1) the quiescence of low-mass [M* ≤ 109.7M⊙] galaxies requires a strong increase of the local density, which confirms the lead role played by environment in their fast quenching and, therefore, confirms that the low-mass upturn observed in the stellar mass function of quiescent galaxies is due to environmental quenching. We also observe that (2) the reservoir of low-mass star-forming galaxies located in very dense regions (prone to environmental quenching) has grown between z ˜ 0.6 and z ˜ 0.4 whilst the share of low-mass quiescent galaxies (expected to being environmentally quenched) may have simultaneously increased, which would plead for a rising importance of environmental quenching with cosmic time, compared to mass quenching. We finally discuss the composite picture of such environmental quenching of low-mass galaxies and, in particular, how this picture may be consistent with a delayed-then-rapid quenching scenario.

Check-Cases for Verification of 6-Degree-of-Freedom Flight Vehicle Simulations

NASA Technical Reports Server (NTRS)

Murri, Daniel G.; Jackson, E. Bruce; Shelton, Robert O.

2015-01-01

The rise of innovative unmanned aeronautical systems and the emergence of commercial space activities have resulted in a number of relatively new aerospace organizations that are designing innovative systems and solutions. These organizations use a variety of commercial off-the-shelf and in-house-developed simulation and analysis tools including 6-degree-of-freedom (6-DOF) flight simulation tools. The increased affordability of computing capability has made highfidelity flight simulation practical for all participants. Verification of the tools' equations-of-motion and environment models (e.g., atmosphere, gravitation, and geodesy) is desirable to assure accuracy of results. However, aside from simple textbook examples, minimal verification data exists in open literature for 6-DOF flight simulation problems. This assessment compared multiple solution trajectories to a set of verification check-cases that covered atmospheric and exo-atmospheric (i.e., orbital) flight. Each scenario consisted of predefined flight vehicles, initial conditions, and maneuvers. These scenarios were implemented and executed in a variety of analytical and real-time simulation tools. This tool-set included simulation tools in a variety of programming languages based on modified flat-Earth, round- Earth, and rotating oblate spheroidal Earth geodesy and gravitation models, and independently derived equations-of-motion and propagation techniques. The resulting simulated parameter trajectories were compared by over-plotting and difference-plotting to yield a family of solutions. In total, seven simulation tools were exercised.

Crack growth and fracture toughness of amorphous Li-Si anodes: Mechanisms and role of charging/discharging studied by atomistic simulations

NASA Astrophysics Data System (ADS)

Khosrownejad, S. M.; Curtin, W. A.

2017-10-01

Fracture is the main cause of degradation and capacity fading in lithiated silicon during cycling. Experiments on the fracture of lithiated silicon show conflicting results, and so mechanistic models can help interpret experiments and guide component design. Here, large-scale K-controlled atomistic simulations of crack propagation (R-curve KI vs. Δa) are performed at LixSi compositions x = 0.5 , 1.0 , 1.5 for as-quenched/relaxed samples and at x = 0.5 , 1.0 for samples created by discharging from higher Li compositions. In all cases, the fracture mechanism is void nucleation, growth, and coalescence. In as-quenched materials, with increasing Li content the plastic flow stress and elastic moduli decrease but void nucleation and growth happen at smaller stress, so that the initial fracture toughness KIc ≈ 1.0 MPa√{ m} decreases slightly but the initial fracture energy JIc ≈ 10.5J/m2 is similar. After 10 nm of crack growth, the fracture toughnesses increase and become similar at KIc ≈ 1.9 MPa√{ m} across all compositions. Plane-strain equi-biaxial expansion simulations of uncracked samples provide complementary information on void nucleation and growth. The simulations are interpreted within the framework of Gurson model for ductile fracture, which predicts JIc = ασy D where α ≃ 1 and D is the void spacing, and good agreement is found. In spite of flowing plastically, the fracture toughness of LixSi is low because voids nucleate within nano-sized distances ahead of the crack (D ≈ 1nm). Scaling simulation results to experimental conditions, reasonable agreement with experimentally-estimated fracture toughnesses is obtained. The discharging process facilitates void nucleation but decreases the flow stress (as shown previously), leading to enhanced fracture toughness at all levels of crack growth. Therefore, the fracture behavior of lithiated silicon at a given composition is not a material property but instead depends on the history of charging/discharging. These findings indicate that the mechanical behavior (flow and fracture) of lithiated Si must be interpreted within a fully rate- and history-dependent framework.

Comparative evaluation of methods for the determination of heat transfer coefficients of liquid and gaseous quenching media

NASA Astrophysics Data System (ADS)

Shevchenko, Svetlana Yu.; Melnik, Yury A.; Smirnov, Andrey E.; Htet, Wai Yan Min

2018-03-01

Temperature dependences of heat transfer coefficients of liquid and gaseous quenching media were determined using a gradient probe and prismatic probe of more simple design. The probes of two different designs were tested in the same conditions. Analysis of heat transfer coefficients showed good agreement between the data obtained. The tests were carried out with liquid and gaseous quenching media: water, polymer quenchant, quenching oil and high-pressure nitrogen. Methods of mathematical modeling of steel samples quenching show the adequacy of the results.

Analysis of fuel using the Direct LSC method determination of bio-originated fuel in the presence of quenching

DOE PAGES

Doll, Charles G.; Wright, Cherylyn W.; Morley, Shannon M.; ...

2017-02-01

In this paper, a modified version of the Direct LSC method to correct for quenching effect was investigated for the determination of bio-originated fuel content in fuel samples produced from multiple biological starting materials. The modified method was found to be accurate in determining the percent bio-originated fuel to within 5% of the actual value for samples with quenching effects ≤43%. Finally, analysis of highly quenched samples was possible when diluted with the exception of one sample with a 100% quenching effect.