Modeling and Simulation of Quenching and Tempering Process in steels

NASA Astrophysics Data System (ADS)

Deng, Xiaohu; Ju, Dongying

Quenching and tempering (Q&T) is a combined heat treatment process to achieve maximum toughness and ductility at a specified hardness and strength. It is important to develop a mathematical model for quenching and tempering process for satisfy requirement of mechanical properties with low cost. This paper presents a modified model to predict structural evolution and hardness distribution during quenching and tempering process of steels. The model takes into account tempering parameters, carbon content, isothermal and non-isothermal transformations. Moreover, precipitation of transition carbides, decomposition of retained austenite and precipitation of cementite can be simulated respectively. Hardness distributions of quenched and tempered workpiece are predicted by experimental regression equation. In order to validate the model, it is employed to predict the tempering of 80MnCr5 steel. The predicted precipitation dynamics of transition carbides and cementite is consistent with the previous experimental and simulated results from literature. Then the model is implemented within the framework of the developed simulation code COSMAP to simulate microstructure, stress and distortion in the heat treated component. It is applied to simulate Q&T process of J55 steel. The calculated results show a good agreement with the experimental ones. This agreement indicates that the model is effective for simulation of Q&T process of steels.

Disruption Neutral Point Experiment on Alcator C-Mod

NASA Astrophysics Data System (ADS)

Granetz, R. S.; Nakamura, Y.

2000-10-01

Disruptions of single-null elongated plasmas generally result in loss of vertical position control, leading to a current quench occurring at the top or bottom of the machine, with all the attendant problems of halo and eddy currents flowing in divertor structures. On JT-60U, it has been found that if the plasma is operated with its magnetic axis at a particular height, called the neutral point, the initial vertical drift after a thermal quench is significantly slower than usual, and sometimes can even be arrested, thereby avoiding a current quench in the divertor region entirely. In an ongoing collaboration between MIT and JAERI, the neutral point concept is being tested in Alcator C-Mod, which has a significantly higher plasma elongation than JT-60U (1.65 vs 1.3). Calculations using TSC predict a neutral point at z~=+1 cm above the midplane (a=22 cm). The existence of a neutral point has now been experimentally confirmed, albeit at a height of z=+2.7 cm. The plasma has remained vertically stable for up to 9 ms after the disruption thermal quench, which in principle, is long enough for the PF control system to respond, if programmed appropriately. In addition, the physics of the neutral point stability on C-Mod appears to be somewhat different than that on JT-60U.

Evolution of Resistance to Quorum Quenching in Digital Organisms

PubMed Central

Beckmann, Benjamin E.; Knoester, David B.; Connelly, Brian D.; Waters, Christopher M.

2014-01-01

Quorum sensing (QS) is a collective behavior whereby actions of individuals depend on the density of the surrounding population. Bacteria use QS to trigger secretion of digestive enzymes, formation and destruction of biofilms, and, in the case of pathogenic organisms, expression of virulence factors that cause disease. Investigations of mechanisms that prevent or disrupt QS, referred to as quorum quenching, are of interest because they provide a new alternative to antibiotics for treating bacterial infections. Traditional antibiotics either kill bacteria or inhibit their growth, producing selective pressures that promote resistant strains. In contrast, quorum quenching and other so-called anti-infective strategies focus on altering behavior. In this article we evolve QS in populations of digital organisms, a type of self-replicating computer program, and investigate the effects of quorum quenching on these populations. Specifically, we injected the populations with mutant organisms that were impaired in selected ways to disrupt the QS process. The experimental results indicate that the rate at which these mutants are introduced into a population influences both the evolvability of QS and the persistence of an existing QS behavior. Surprisingly, we also observed resistance to quorum quenching. Effectively, populations evolved resistance by reaching quorum at lower cell densities than did the parent strain. Moreover, the level of resistance was highest when the rate of mutant introduction increased over time. These results show that digital organisms can serve as a model to study the evolution and disruption of QS, potentially informing wet-lab studies aimed at identifying targets for anti-infective development. PMID:22662911

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).

Experimental and theoretical investigation of the temperature dependent electronic quenching of O(1D) atoms in collisions with Kr

NASA Astrophysics Data System (ADS)

Nuñez-Reyes, Dianailys; Kłos, Jacek; Alexander, Millard H.; Dagdigian, Paul J.; Hickson, Kevin M.

2018-03-01

The kinetics and dynamics of the collisional electronic quenching of O(1D) atoms by Kr have been investigated in a joint experimental and theoretical study. The kinetics of quenching were measured over the temperature range 50-296 K using the Laval nozzle method. O(1D) atoms were prepared by 266 nm photolysis of ozone, and the decay of the O(1D) concentration was monitored through vacuum ultraviolet fluorescence at 115.215 nm, from which the rate constant was determined. To interpret the experiments, a quantum close-coupling treatment of the quenching transition from the 1D state to the 3Pj fine-structure levels in collisions with Kr, and also Ar and Xe, was carried out. The relevant potential energy curves and spin-orbit coupling matrix elements were obtained in electronic structure calculations. We find reasonable agreement between computed temperature-dependent O(1D)-Rg (Rg = Ar, Kr, Xe) quenching rate constants and the present measurements for Kr and earlier measurements. In particular, the temperature dependence is well described.

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.

An experimental study of OH(A2Σ+) + H2: Electronic quenching, rotational energy transfer, and collisional depolarization

NASA Astrophysics Data System (ADS)

Brouard, M.; Lawlor, J.; McCrudden, G.; Perkins, T.; Seamons, S. A.; Stevenson, P.; Chadwick, H.; Aoiz, F. J.

2017-06-01

Zeeman quantum beat spectroscopy has been used to determine the thermal (300 K) rate constants for electronic quenching, rotational energy transfer, and collisional depolarization of OH(A2Σ+) by H2. Cross sections for both the collisional disorientation and collisional disalignment of the angular momentum in the OH(A2Σ+) radical are reported. The experimental results for OH(A2Σ+) + H2 are compared to previous work on the OH(A2Σ+) + He and Ar systems. Further comparisons are also made to the OH(A2Σ+) + Kr system, which has been shown to display significant non-adiabatic dynamics. The OH(A2Σ+) + H2 experimental data reveal that collisions that survive the electronic quenching process are highly depolarizing, reflecting the deep potential energy wells that exist on the excited electronic state surface.

DETERMINING MINIMUM IGNITION ENERGIES AND QUENCHING DISTANCES OF DIFFICULT-TO-IGNITE COMPOUNDS

EPA Science Inventory

Minimum spark energies and corresponding flat-plate electrode quenching distances required to initiate propagation of a combustion wave have been experimentally measured for four flammable hydrofluorocarbon (HFC) refrigerants and propane using ASTM (American Society for Testing a...

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.

Adiabatic and Non-adiabatic quenches in a Spin-1 Bose Einstein Condensate

NASA Astrophysics Data System (ADS)

Boguslawski, Matthew; Hebbe Madhusudhana, Bharath; Anquez, Martin; Robbins, Bryce; Barrios, Maryrose; Hoang, Thai; Chapman, Michael

2016-05-01

A quantum phase transition (QPT) is observed in a wide range of phenomena. We have studied the dynamics of a spin-1 ferromagnetic Bose-Einstein condensate for both adiabatic and non-adiabatic quenches through a QPT. At the quantum critical point (QCP), finite size effects lead to a non-zero gap, which makes an adiabatic quench possible through the QPT. We experimentally demonstrate such a quench, which is forbidden at the mean field level. For faster quenches through the QCP, the vanishing energy gap causes the reaction timescale of the system to diverge, preventing the system from adiabatically following the ground state. We measure the temporal evolution of the spin populations for different quench speeds and determine the exponents characterizing the scaling of the onset of excitations, which are in good agreement with the predictions of Kibble-Zurek mechanism.

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.

Fluorescence Quenching of Alpha-Fetoprotein by Gold Nanoparticles: Effect of Dielectric Shell on Non-Radiative Decay

NASA Astrophysics Data System (ADS)

Zhu, Jian; Li, Jian-Jun; Wang, A.-Qing; Chen, Yu; Zhao, Jun-Wu

2010-09-01

Fluorescence quenching spectrometry was applied to study the interactions between gold colloidal nanoparticles and alpha-fetoprotein (AFP). Experimental results show that the gold nanoparticles can quench the fluorescence emission of adsorbed AFP effectively. Furthermore, the intensity of fluorescence emission peak decreases monotonously with the increasing gold nanoparticles content. A mechanism based on surface plasmon resonance-induced non-radiative decay was investigated to illuminate the effect of a dielectric shell on the fluorescence quenching ability of gold nanoparticles. The calculation results show that the increasing dielectric shell thickness may improve the monochromaticity of fluorescence quenching. However, high energy transfer efficiency can be obtained within a wide wavelength band by coating a thinner dielectric shell.

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.

Does Cu(acac)2 Quench Benzene Fluorescence? A Physical Chemistry Experiment.

ERIC Educational Resources Information Center

Marciniak, Bronislaw

1986-01-01

Describes a laboratory experiment in which benzene fluorescence is quenched by bis(acetylacetonato) copper(II). Discusses how this experiment can demonstrate a special technique used in the field of photochemistry. Provides an outline of the experimental procedure and discusses its results. (TW)

RQL Fuel Shifting Sector Rig Test

NASA Technical Reports Server (NTRS)

Holdeman, James D. (Technical Monitor); Haid, Daniel A.; Koopman, Frederick S.; Peschke, William O. T.; Siskind, Kenneth S.

2004-01-01

The low emissions potential of a Rich-Quench-Lean (RQL) combustor for use in the HIgh Speed Civil transport (HSCT) application was evaluated as part of the NASA Critical Propulsion Components (CPC) Program. Fuel shifting as an approach to combustor control was evaluated in a multiple bank RQL combustor, utilizing reduced scale quench technology implemented in a convoluted linear with quench plate concept.

Behaviors of 40Cr steel treated by laser quenching on impact abrasive wear

NASA Astrophysics Data System (ADS)

Chen, Zhikai; Zhu, Qinghai; Wang, Jing; Yun, Xiao; He, Bing; Luo, Jingshuai

2018-07-01

In present work, laser quenching had been carried out to improve the impact abrasive wear resistance of 40Cr steel. The distinct microstructure between original and quenched region was demonstrated after laser quenching. Since the effect of temperature and cooling rate, the phase combinations were apparently different for quenched layer in depth. The impact abrasive wear resistance of sample was experimentally investigated and the improved level was assessed in light of the average mass loss of three repetitive tests. Worn surface was detected by means of SEM, OM and EDS, and results showed that three typical failure modes were performed during the processing of impact abrasive wear, including abrasive wear, impact effect and rolling contact fatigue. Basing on the different worn surface profile, the mainly failure mode was respectively pointed out for matrix and quenched sample, which was significantly in accordance with the result of impact abrasive wear.

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

Fluorescence quenching by TEMPO: a sub-30 A single-molecule ruler.

PubMed

Zhu, Peizhi; Clamme, Jean-Pierre; Deniz, Ashok A

2005-11-01

A series of DNA molecules labeled with 5-carboxytetramethylrhodamine (5-TAMRA) and the small nitroxide radical TEMPO were synthesized and tested to investigate whether the intramolecular quenching efficiency can be used to measure short intramolecular distances in small ensemble and single-molecule experiments. In combination with distance calculations using molecular mechanics modeling, the experimental results from steady-state ensemble fluorescence and fluorescence correlation spectroscopy measurements both show an exponential decrease in the quenching rate constant with the dye-quencher distance in the 10-30 A range. The results demonstrate that TEMPO-5-TAMRA fluorescence quenching is a promising method to measure short distance changes within single biomolecules.

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

The R&D PERFROI Project on Thermal Mechanical and Thermal Hydraulics Behaviors of a Fuel Rod Assembly during a Loss of Coolant Accident

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

Repetto, G.; Dominguez, C.; Durville, B.

The safety principle in case of a LOCA is to preserve the short and long term coolability of the core. The associated safety requirements are to ensure the resistance of the fuel rods upon quench and post-quench loads and to maintain a coolable geometry in the core. An R&D program has been launched by IRSN with the support of EDF, to perform both experimental and modeling activities in the frame of the LOCA transient, on technical issues such as: - flow blockage within a fuel rods bundle and its potential impact on coolability, - fuel fragment relocation in the balloonedmore » areas: its potential impact on cladding PCT (Peak Cladding Temperature) and on the maximum oxidation rate, - potential loss of cladding integrity upon quench and post-quench loads. The PERFROI project (2014-2019) focusing on the first above issue, is structured in two axes: 1. axis 1: thermal mechanical behavior of deformation and rupture of cladding taking into account the contact between fuel rods; specific research at LaMCoS laboratory focus on the hydrogen behavior in cladding alloys and its impact on the mechanical behavior of the rod; and, 2. axis 2: thermal hydraulics study of a partially blocked region of the core (ballooned area taking into account the fuel relocation with local over power), during cooling phase by water injection; More detailed activities foreseen in collaboration with LEMTA laboratory will focus on the characterization of two phase flows with heat transfer in deformed structures.« less

Quantum state-to-state dynamics for the quenching process of Br(2P1/2) + H2(v(i) = 0, 1, j(i) = 0).

PubMed

Xie, Changjian; Jiang, Bin; Xie, Daiqian; Sun, Zhigang

2012-03-21

Quantum state-to-state dynamics for the quenching process Br((2)P(1/2)) + H(2)(v(i) = 0, 1, j(i) = 0) → Br((2)P(3/2)) + H(2)(v(f), j(f)) has been studied based on two-state model on the recent coupled potential energy surfaces. It was found that the quenching probabilities have some oscillatory structures due to the interference of reflected flux in the Br((2)P(1/2)) + H(2) and Br((2)P(3/2)) + H(2) channels by repulsive potential in the near-resonant electronic-to-vibrational energy transfer process. The final vibrational state resolved integral cross sections were found to be dominated by the quenching process Br((2)P(1/2)) + H(2)(v) → Br((2)P(3/2)) + H(2)(v+1) and the nonadiabatic reaction probabilities for Br((2)P(1/2)) + H(2)(v = 0, 1, j(i) = 0) are quite small, which are consistent with previous theoretical and experimental results. Our calculated total quenching rate constant for Br((2)P(1/2)) + H(2)(v(i) = 0, j(i) = 0) at room temperature is in good agreement with the available experimental data. © 2012 American Institute of Physics

Fluorescence Quenching by TEMPO: A Sub-30 Å Single-Molecule Ruler

PubMed Central

Zhu, Peizhi; Clamme, Jean-Pierre; Deniz, Ashok A.

2005-01-01

A series of DNA molecules labeled with 5-carboxytetramethylrhodamine (5-TAMRA) and the small nitroxide radical TEMPO were synthesized and tested to investigate whether the intramolecular quenching efficiency can be used to measure short intramolecular distances in small ensemble and single-molecule experiments. In combination with distance calculations using molecular mechanics modeling, the experimental results from steady-state ensemble fluorescence and fluorescence correlation spectroscopy measurements both show an exponential decrease in the quenching rate constant with the dye-quencher distance in the 10–30 Å range. The results demonstrate that TEMPO-5-TAMRA fluorescence quenching is a promising method to measure short distance changes within single biomolecules. PMID:16199509

Dissipated energy as a design parameter of coated conductors for their use in resistive fault current limiters

NASA Astrophysics Data System (ADS)

Schacherer, C.; Kudymow, A.; Noe, M.

2008-02-01

Coated conductors are suitable for many power applications like motors, magnets and superconducting fault current limiters (SCFCLs). For their use in resistive SCFCLs main requirements are quench stability and resistance development above Tc. Several coated conductors are available with different kinds of stabilization like thickness or material of cap-layer and additional stabilization. The stabilization can vary and has a great influence on the quench stability and quench behaviour of a coated conductor. Thus, for the dimensioning of a superconducting current limiting element there is a need of reliable and universal design parameters. This paper presents experimental quench test results on several coated conductor types with different stabilization and geometry. The test results show that the dissipated energy during a quench is a very useful parameter for the SCFCL design.

Halide (Cl(super -)) Quenching of Quinine Sulfate Fluorescence: A Time-Resolved Fluorescence Experiment for Physical Chemistry

ERIC Educational Resources Information Center

Gutow, Jonathan H.

2005-01-01

The time-resolved fluorescence experiment investigating the halide quenching of fluorescence from quinine sulfate in water is described. The objectives of the experiment include reinforcing student understanding of the kinetics of competing pathways, making connections with microscopic theories of kinetics through comparison of experimental and…

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

Use of propane as a quench gas in argon-filled proportional counters and comparison with other quench gases

NASA Technical Reports Server (NTRS)

Agrawal, P. C.; Ramsey, B. D.

1988-01-01

An experimental investigation of propane and six other quench gases was carried out in argon-filled proportional counters. The objective of the study was to find the best gas mixture for optimizing the gas gain and the energy resolution as well as to understand the role of the ionization potential of quench gases in determining these parameters. It was found that the best gas gains and energy resolutions are obtained with propane, ethane, and isobutane in that order. The ionization potentials of these three lie below the argon metastable potentials and have the lowest value of resonance defect compared to the other quench gases. The better results obtained with these mixtures can be explained by an increased ionization yield resulting from the Penning effect. Propylene and trans-2-butene give inferior performance compared to the above three gases. Methane and carbon dioxide, the most commonly used quench gases in the argon-filled detectors, provide the worst results.

The generation of thermal stress and strain during quenching

NASA Astrophysics Data System (ADS)

Soomro, A. B.

A viscoelastic-plastic mathematical model was used to calculate the thermal stress and strain generated during the quenching of an infinite plate of high hardenability steel (835M30) in water, oil and Polymer. In the present work the mathematical model was modified to include the effect of initial stress on the rate of stress relaxation, which has been found to be significant. The data required to incorporate this effect into the calculations, were obtained experimentally during the-.present investigation. The effect of an applied stress during transformation (transformation plasticity) was also introduced in the mathematical model. The new model produced a marked improvement in the degree of agreement between the calculated and experimental residual stress, although the corresponding level of agreement in the case of residual strain was less good. In particular, strains after water quenching agreed less well with experiment as a consequence of the change in the model, although this drawback was not found after oil and polymer quenching. The new mathematical model was used to investigate the effect of martempering, section size and transformation temperature range on the generation of thermal stress and strain. A salt bath treatment above the Ms temperature followed by air cooling prevented residual stress development, but an oil quench after the salt bath treatment generated a level of residual stress at the end of cooling that was similar to that obtained after a direct oil quench from 850°C. Neither martempering process was successful in reducing residual strain.With.an increase in section size a reduction in the residual stress and an increase in the distortions was obtained after a water quench. However, after oil quenching the overall effect of section size on residual stress and strain was small. The effect of variation in the transformation temperature range was found to be small in the case of residual stress but an increase in Ms temperature produced a significant increase in the level of residual strain.

Large Engine Technology Program. Task 21: Rich Burn Liner for Near Term Experimental Evaluations

NASA Technical Reports Server (NTRS)

Hautman, D. J.; Padget, F. C.; Kwoka, D.; Siskind, K. S.; Lohmann, R. P.

2005-01-01

The objective of the task reported herein, which was conducted as part of the NASA sponsored Large Engine Technology program, was to define and evaluate a near-term rich-zone liner construction based on currently available materials and fabrication processes for a Rich-Quench-Lean combustor. This liner must be capable of operation at the temperatures and pressures of simulated HSCT flight conditions but only needs sufficient durability for limited duration testing in combustor rigs and demonstrator engines in the near future. This must be achieved at realistic cooling airflow rates since the approach must not compromise the emissions, performance, and operability of the test combustors, relative to the product engine goals. The effort was initiated with an analytical screening of three different liner construction concepts. These included a full cylinder metallic liner and one with multiple segments of monolithic ceramic, both of which incorporated convective cooling on the external surface using combustor airflow that bypassed the rich zone. The third approach was a metallic platelet construction with internal convective cooling. These three metal liner/jacket combinations were tested in a modified version of an existing Rich-Quench-Lean combustor rig to obtain data for heat transfer model refinement and durability verification.

Induction Hardening of External Gear

NASA Astrophysics Data System (ADS)

Bukanin, V. A.; Ivanov, A. N.; Zenkov, A. E.; Vologdin, V. V.; Vologdin, V. V., Jr.

2018-03-01

Problems and solution of gear induction hardening are described. Main attention is paid to the parameters of heating and cooling systems. ELTA 7.0 program has been used to obtain the required electrical parameters of inductor, power sources, resonant circuits, as well as to choose the quenching media. Comparison of experimental and calculated results of investigation is provided. In order to compare advantages and disadvantages of single- and dual-frequency heating processes, many variants of these technologies were simulated. The predicted structure and hardness of steel gears are obtained by use of the ELTA data base taken into account the Continuous Cooling Transformation diagrams.

Textural evolution of partially-molten planetary materials in microgravity

NASA Technical Reports Server (NTRS)

Watson, E. B.

1987-01-01

Recent Earth-based experiments examining the textural evolution of partially-molten rocks have revealed two important ways in which surface energy considerations affect magma. An initial experimental program addressing surface-energy effects on partially-molten materials in microgravity would involve simple, isothermal treatment of natural samples (meteorites, perioditic komatiite) at preselected temperatures in the melting range. Textural evolution would be assessed by time studies in which the only experiment variable would be run duration. Textural characterization of each sample would be done by quenching, recover, and sectioning for generally later, computer-aided interpretation of features.

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.

Simple replacement of violaxanthin by zeaxanthin in LHC-II does not cause chlorophyll fluorescence quenching.

PubMed

Dreuw, Andreas; Wormit, Michael

2008-03-01

Recently, a mechanism for the energy-dependent component (qE) of non-photochemical quenching (NPQ), the fundamental photo-protection mechanism in green plants, has been suggested. Replacement of violaxanthin by zeaxanthin in the binding pocket of the major light harvesting complex LHC-II may be sufficient to invoke efficient chlorophyll fluorescence quenching. Our quantum chemical calculations, however, show that the excited state energies of violaxanthin and zeaxanthin are practically identical when their geometry is constrained to the naturally observed structure of violaxanthin in LHC-II. Therefore, since violaxanthin does not quench LHC-II, zeaxanthin should not either. This theoretical finding is nicely in agreement with experimental results obtained by femtosecond spectroscopy on LHC-II complexes containing violaxanthin or zeaxanthin.

Quench Protection of SC Quadrupole Magnets

NASA Astrophysics Data System (ADS)

Feher, S.; Bossert, R.; Dimarco, J.; Mitchell, D.; Lamm, M. J.; Limon, P. J.; Mazur, P.; Nobrega, F.; Orris, D.; Ozelis, J. P.; Strait, J. B.; Tompkins, J. C.; Zlobin, A. V.; McInturff, A. D.

1997-05-01

The energy stored in a superconducting accelerator magnet is dissipated after a quench in the coil normal zones, heating the coil and generating a turn to turn and coil to ground voltage drop. Quench heaters are used to protect the superconducting magnet by greatly increasing the coil normal zone thus allowing the energy to be dissipated over a larger conductor volume. Such heaters will be required for the Fermilab/LBNL design of the high gradient quads (HGQ) designed for the LHC interaction regions. As a first step, heaters were installed and tested in several Tevatron low-β superconducting quadrupoles. Experimental studies in normal and superfluid helium are presented which show the heater-induced quench response as a function of magnet excitation current, magnet temperature and peak heater energy density.

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

Resonance energy transfer: Dye to metal nanoparticles

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

Wari, M. N.; Pujar, G. H.; Inamdar, S. R., E-mail: him-lax3@yahoo.com

2015-06-24

In the present study, surface energy transfer (SET) from Coumarin 540A (C540 A) to Gold nanoparticle (Au) is demonstrated. The observed results show pronounced effect on the photoluminescence intensity and shortening of the lifetime of Coumarin 540A upon interaction with the spherical gold nanoparticle, also there are measured effects on radiative rate of the dye. Experimental results are analyzed with fluorescence resonance energy transfer (FRET) and SET theories. The results obtained from distance-dependent quenching provide experimental evidence that the efficiency curve slope and distance of quenching is best modeled by surface energy transfer process.

Ultra-fast photon counting with a passive quenching silicon photomultiplier in the charge integration regime

NASA Astrophysics Data System (ADS)

Zhang, Guoqing; Lina, Liu

2018-02-01

An ultra-fast photon counting method is proposed based on the charge integration of output electrical pulses of passive quenching silicon photomultipliers (SiPMs). The results of the numerical analysis with actual parameters of SiPMs show that the maximum photon counting rate of a state-of-art passive quenching SiPM can reach ~THz levels which is much larger than that of the existing photon counting devices. The experimental procedure is proposed based on this method. This photon counting regime of SiPMs is promising in many fields such as large dynamic light power detection.

CONSTITUTIVE BEHAVIOR OF AS-QUENCHED Al-Cu-Mn ALLOY

NASA Astrophysics Data System (ADS)

Yang, Xia-Wei; Zhu, Jing-Chuan; Nong, Zhi-Sheng; Ye, Mao; Lai, Zhong-Hong; Liu, Yong

2013-07-01

The hot flow stress of as-quenched Al-Cu-Mn alloy was modeled using the constitutive equations. The as-quenched Al-Cu-Mn alloy were treated with isothermal hot compression tests in the temperature range of 350-500°C, the strain rate range of 0.001-1 s-1. The hyperbolic sine equation was found to be appropriate for flow stress modeling and prediction. Based on the hyperbolic sine equation, a constitutive equation is a relation between 0.2 pct yield stress and deformation conditions (strain rate and deformation temperature) was established. The corresponding hot deformation activation energy (Q) for as-quenched Al-Cu-Mn alloy was determined to be 251.314 kJ/mol. Parameters of constitutive equation of as-quenched Al-Cu-Mn alloy were calculated at different small strains (≤ 0.01). The calculated flow stresses from the constitutive equation are in good agreement with the experimental results. Therefore, this constitutive equation can be used as an accurate temperature-stress model to solve the problems of quench distortion of Al-Cu-Mn alloy parts.

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

Abbaszadeh, D.; Wetzelaer, G. A. H.; Dutch Polymer Institute, P.O. Box 902, 5600 AX, Eindhoven

The quenching of excitons at the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) anode in blue polyalkoxyspirobifluorene-arylamine polymer light-emitting diodes is investigated. Due to the combination of a higher electron mobility and the presence of electron traps, the recombination zone shifts from the cathode to the anode with increasing voltage. The exciton quenching at the anode at higher voltages leads to an efficiency roll-off. The voltage dependence of the luminous efficiency is reproduced by a drift-diffusion model under the condition that quenching of excitons at the PEDOT:PSS anode and metallic cathode is of equal strength. Experimentally, the efficiency roll-off at high voltages due tomore » anode quenching is eliminated by the use of an electron-blocking layer between the anode and the light-emitting polymer.« less

Designing an anion-functionalized fluorescent ionic liquid as an efficient and reversible turn-off sensor for detecting SO2.

PubMed

Che, Siying; Dao, Rina; Zhang, Weidong; Lv, Xiaoyu; Li, Haoran; Wang, Congmin

2017-03-30

A novel anion-functionalized fluorescent ionic liquid was designed and prepared, which was capable of capturing sulphur dioxide with high capacity and could also be used as a good colorimetric and fluorescent SO 2 sensor. Compared to conventional fluorescent sensors, this fluorescent ionic liquid did not undergo aggregation-caused quenching or aggregation-induced emission, and the fluorescence was quenched when exposed to SO 2 , and the fluorescence would quench when exposed to SO 2 . The experimental absorption, spectroscopic investigation, and quantum chemical calculations indicated that the quenching of the fluorescence originated from SO 2 physical absorption, not chemical absorption. Furthermore, this fluorescent ionic liquid exhibited high selectivity, good quantification, and excellent reversibility for SO 2 detection, and showed potential for an excellent liquid sensor.

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.

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

Oral Cooling and Carbonation Increase the Perception of Drinking and Thirst Quenching in Thirsty Adults

PubMed Central

Peyrot des Gachons, Catherine; Avrillier, Julie; Gleason, Michael; Algarra, Laure; Zhang, Siyu; Mura, Emi; Nagai, Hajime

2016-01-01

Fluid ingestion is necessary for life, and thirst sensations are a prime motivator to drink. There is evidence of the influence of oropharyngeal stimulation on thirst and water intake in both animals and humans, but how those oral sensory cues impact thirst and ultimately the amount of liquid ingested is not well understood. We investigated which sensory trait(s) of a beverage influence the thirst quenching efficacy of ingested liquids and the perceived amount ingested. We deprived healthy individuals of liquid and food overnight (> 12 hours) to make them thirsty. After asking them to drink a fixed volume (400 mL) of an experimental beverage presenting one or two specific sensory traits, we determined the volume ingested of additional plain, ‘still’, room temperature water to assess their residual thirst and, by extension, the thirst-quenching properties of the experimental beverage. In a second study, participants were asked to drink the experimental beverages from an opaque container through a straw and estimate the volume ingested. We found that among several oro-sensory traits, the perceptions of coldness, induced either by cold water (thermally) or by l-menthol (chemically), and the feeling of oral carbonation, strongly enhance the thirst quenching properties of a beverage in water-deprived humans (additional water intake after the 400 ml experimental beverage was reduced by up to 50%). When blinded to the volume of liquid consumed, individual’s estimation of ingested volume is increased (~22%) by perceived oral cold and carbonation, raising the idea that cold and perhaps CO2 induced-irritation sensations are included in how we normally encode water in the mouth and how we estimate the quantity of volume swallowed. These findings have implications for addressing inadequate hydration state in populations such as the elderly. PMID:27685093

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.

Quench in a conduction-cooled Nb3Sn SMES magnet

NASA Astrophysics Data System (ADS)

Korpela, Aki; Lehtonen, Jorma; Mikkonen, Risto; Perälä, Raine

2003-11-01

Due to the rapid development of cryocoolers, conduction-cooled Nb3Sn devices are nowadays enabled. A 0.2 MJ conduction-cooled Nb3Sn SMES system has been designed and constructed. The nominal current of the coil was 275 A at 10 K. The quench tests have been performed and in this paper the experimental data are compared to the computational one. Due to a slow normal zone propagation, Nb3Sn magnets are not necessarily self-protective. In conduction-cooled coils, a thermal interface provides a protection method known as a quench back. The temperature rise in the coil during a quench was measured with a sensor located on the inner radius of the coil. The current decay was also monitored. The measured temperature increased for approximately 15 s after the current had already decayed. This temperature rise is due to the heat conduction from the hot spot. Thus, the measured temperature does not represent the hot-spot temperature. A computational quench model which takes into account quench back and heat conduction after the current decay was developed in order to understand the measured temperatures. According to the results, a quench back due to the eddy current induced heating of the thermal interface of an LTS coil was an adequate protection method.

High-temperature synthesis of silica particles by the chloride method in the regime of counter flow jet quenching

NASA Astrophysics Data System (ADS)

Kartaev, E. V.; Emel'kin, V. A.; Aul'chenko, S. M.

2017-10-01

The experimental and numerical investigations of synthesis of silica (SiO2) nanoparticles from premixed gaseous silicon tetrachloride (SiCl4) and oxygen of dry air in the high-temperature nitrogen flow of plasma-chemical reactor have been carried out. The regime of counter flow jet quenching of high-temperature heterogeneous flow has been utilized. The latter provided a rapid cooling of silica particles under nonequilibrium conditions with substantial temperature gradients. Synthesized silica particles were amorphous, with surface-average size being about 28 nm. The results of numerical calculations are found to agree qualitatively with experimental data.

A new potential for radiation studies of borosilicate glass

NASA Astrophysics Data System (ADS)

Alharbi, Amal F.; Jolley, Kenny; Smith, Roger; Archer, Andrew J.; Christie, Jamieson K.

2017-02-01

Borosilicate glass containing 70 mol% SiO2 and 30 mol% B2O3 is investigated theoretically using fixed charge potentials. An existing potential parameterisation for borosilicate glass is found to give good agreement for the bond angle and bond length distributions compared to experimental values but the optimal density is 30% higher than experiment. Therefore the potential parameters are refitted to give an optimal density of 2.1 g/cm3, in line with experiment. To determine the optimal density, a series of random initial structures are quenched at a rate of 5 × 1012 K/s using constant volume molecular dynamics. An average of 10 such quenches is carried out for each fixed volume. For each quenched structure, the bond angles, bond lengths, mechanical properties and melting points are determined. The new parameterisation is found to give the density, bond angles, bond lengths and Young's modulus comparable with experimental data, however, the melting points and Poisson's ratio are higher than the reported experimental values. The displacement energy thresholds are computed to be similar to those determined with the earlier parameterisation, which is lower than those for ionic crystalline materials.

Electronic quenching of O({sup 1}D) by Xe: Oscillations in the product angular distribution and their dependence on collision energy

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

Garofalo, Lauren A.; Smith, Mica C.; Dagdigian, Paul J., E-mail: pjdagdigian@jhu.edu

2015-08-07

The dynamics of the O({sup 1}D) + Xe electronic quenching reaction was investigated in a crossed beam experiment at four collision energies. Marked large-scale oscillations in the differential cross sections were observed for the inelastic scattering products, O({sup 3}P) and Xe. The shape and relative phases of the oscillatory structure depend strongly on collision energy. Comparison of the experimental results with time-independent scattering calculations shows qualitatively that this behavior is caused by Stueckelberg interferences, for which the quantum phases of the multiple reaction pathways accessible during electronic quenching constructively and destructively interfere.

[A study on the concentration quenching of Tm3+ upconversion luminescence].

PubMed

Chen, B; Wang, H; Huang, S

2001-06-01

In this work, we have a designation and preparation of MFT glasses for upconversion, the glasses consisted of TeO2 and fluoride: PbF2, AlF3, BaF2, NaF and the impurity Tm2O3. In this glass system the oxide improve forming ability, the fluorides improve the microscopic environment around RE ions in glasses. In this glass host the content of Tm2O3 achieves to 4% mol and crystallization no occurred. A detail study on the concentration quenching of upconversion luminescence for 1G4-->3H6 and 1D2-->3H4 transitions was completed. The experimental results directed that the quenching concentration was 0.6 mol.% and higher 3 times than in other glasses materials. The cross relaxation and mechanism of concentration quenching were discussed.

Salt dependence of compression normal forces of quenched polyelectrolyte brushes

NASA Astrophysics Data System (ADS)

Hernandez-Zapata, Ernesto; Tamashiro, Mario N.; Pincus, Philip A.

2001-03-01

We obtained mean-field expressions for the compression normal forces between two identical opposing quenched polyelectrolyte brushes in the presence of monovalent salt. The brush elasticity is modeled using the entropy of ideal Gaussian chains, while the entropy of the microions and the electrostatic contribution to the grand potential is obtained by solving the non-linear Poisson-Boltzmann equation for the system in contact with a salt reservoir. For the polyelectrolyte brush we considered both a uniformly charged slab as well as an inhomogeneous charge profile obtained using a self-consistent field theory. Using the Derjaguin approximation, we related the planar-geometry results to the realistic two-crossed cylinders experimental set up. Theoretical predictions are compared to experimental measurements(Marc Balastre's abstract, APS March 2001 Meeting.) of the salt dependence of the compression normal forces between two quenched polyelectrolyte brushes formed by the adsorption of diblock copolymers poly(tert-butyl styrene)-sodium poly(styrene sulfonate) [PtBs/NaPSS] onto an octadecyltriethoxysilane (OTE) hydrophobically modified mica, as well as onto bare mica.

Mechanical Properties Analysis of 4340 Steel Specimen Heat Treated in Oven and Quenching in Three Different Fluids

NASA Astrophysics Data System (ADS)

Fakir, Rachid; Barka, Noureddine; Brousseau, Jean

2018-03-01

This paper proposes a statistical approach to analyze the mechanical properties of a standard test specimen, of cylindrical geometry and in steel 4340, with a diameter of 6 mm, heat-treated and quenched in three different fluids. Samples were evaluated in standard tensile test to access their characteristic quantities: hardness, modulus of elasticity, yield strength, tensile strength and ultimate deformation. The proposed approach is gradually being built (a) by a presentation of the experimental device, (b) a presentation of the experimental plan and the results of the mechanical tests, (c) anova analysis of variance and a representation of the output responses using the RSM response surface method, and (d) an analysis of the results and discussion. The feasibility and effectiveness of the proposed approach leads to a precise and reliable model capable of predicting the variation of mechanical properties, depending on the tempering temperature, the tempering time and the cooling capacity of the quenching medium.

Behavior of Al-Mg alloy subjected to thermal processing

NASA Astrophysics Data System (ADS)

Cristian, AchiÅ£ei Dragoş; Georgiana, Minciunǎ Mirabela; Victor, Sandu Andrei; Abdullah, Mohd Mustafa Al Bakri

2017-04-01

In the paper are shown the experimental results obtained for aluminum alloy, after application of the heat treatments by quenching solution and artificial ageing. The purpose of quenching solution treatment is to decrease the hardness and improve the machining for industrial parts made from this material. By artificial ageing treatment, the Al-Mg structure is modified, the hardness increase to the values necessary for a long exploitation of the parts.

Quench dynamics in SRF cavities: can we locate the quench origin with 2nd sound?

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

Maximenko, Yulia; /Moscow, MIPT; Segatskov, Dmitri A.

2011-03-01

A newly developed method of locating quenches in SRF cavities by detecting second-sound waves has been gaining popularity in SRF laboratories. The technique is based on measurements of time delays between the quench as determined by the RF system and arrival of the second-sound wave to the multiple detectors placed around the cavity in superfluid helium. Unlike multi-channel temperature mapping, this approach requires only a few sensors and simple readout electronics; it can be used with SRF cavities of almost arbitrary shape. One of its drawbacks is that being an indirect method it requires one to solve an inverse problemmore » to find the location of a quench. We tried to solve this inverse problem by using a parametric forward model. By analyzing the data we found that the approximation where the second-sound emitter is a near-singular source does not describe the physical system well enough. A time-dependent analysis of the quench process can help us to put forward a more adequate model. We present here our current algorithm to solve the inverse problem and discuss the experimental results.« less

Application of a Model for Quenching and Partitioning in Hot Stamping of High-Strength Steel

NASA Astrophysics Data System (ADS)

Zhu, Bin; Liu, Zhuang; Wang, Yanan; Rolfe, Bernard; Wang, Liang; Zhang, Yisheng

2018-04-01

Application of quenching and partitioning process in hot stamping has proven to be an effective method to improve the plasticity of advanced high-strength steels (AHSSs). In this study, the hot stamping and partitioning process of advanced high-strength steel 30CrMnSi2Nb is investigated with a hot stamping mold. Given the specific partitioning time and temperature, the influence of quenching temperature on the volume fraction of microstructure evolution and mechanical properties of the above steel are studied in detail. In addition, a model for quenching and partitioning process is applied to predict the carbon diffusion and interface migration during partitioning, which determines the retained austenite volume fraction and final properties of the part. The predicted trends of the retained austenite volume fraction agree with the experimental results. In both cases, the volume fraction of retained austenite increases first and then decreases with the increasing quenching temperature. The optimal quenching temperature is approximately 290 °C for 30CrMnSi2Nb with the partition conditions of 425 °C and 20 seconds. It is suggested that the model can be used to help determine the process parameters to obtain retained austenite as much as possible.

Quench dynamics of a dissipative Rydberg gas in the classical and quantum regimes

NASA Astrophysics Data System (ADS)

Gribben, Dominic; Lesanovsky, Igor; Gutiérrez, Ricardo

2018-01-01

Understanding the nonequilibrium behavior of quantum systems is a major goal of contemporary physics. Much research is currently focused on the dynamics of many-body systems in low-dimensional lattices following a quench, i.e., a sudden change of parameters. Already such a simple setting poses substantial theoretical challenges for the investigation of the real-time postquench quantum dynamics. In classical many-body systems, the Kolmogorov-Mehl-Johnson-Avrami model describes the phase transformation kinetics of a system that is quenched across a first-order phase transition. Here, we show that a similar approach can be applied for shedding light on the quench dynamics of an interacting gas of Rydberg atoms, which has become an important experimental platform for the investigation of quantum nonequilibrium effects. We are able to gain an analytical understanding of the time evolution following a sudden quench from an initial state devoid of Rydberg atoms and identify strikingly different behaviors of the excitation growth in the classical and quantum regimes. Our approach allows us to describe quenches near a nonequilibrium phase transition and provides an approximate analytical solution deep in the quantum domain.

Distinctive features of kinetics of plasma at high specific energy deposition

NASA Astrophysics Data System (ADS)

Lepikhin, Nikita; Popov, Nikolay; Starikovskaia, Svetlana

2016-09-01

A nanosecond capillary discharge in pure nitrogen at moderate pressures is used as an experimental tool for plasma kinetics studies at conditions of high specific deposited energy up to 1 eV/molecule. Experimental observations based on electrical (back current shunts, capacitive probe) and spectroscopic measurements (quenching rates; translational, rotational and vibrational temperature measurements) demonstrate that high specific deposited energy, at electric fields of 200-300 Td, can significantly change gas kinetics in the discharge and in the afterglow. The numerical calculations in 1D axially symmetric geometry using experimental data as input parameters show that changes in the plasma kinetics are caused by extremely high excitation degree: up to 10% of molecular nitrogen is electronically excited at present conditions. Distinctive features of kinetics of plasma at high specific energy deposition as well as details of the experimental technique and numerical calculations will be present. The work was partially supported by French National Agency, ANR (PLASMAFLAME Project, 2011 BS09 025 01), AOARD AFOSR, FA2386-13-1-4064 grant (Program Officer Prof. Chiping Li), LabEx Plas@Par and Linked International Laboratory LIA KaPPA (France-Russia).

Exploring Renner-Teller induced quenching in the reaction H(2S)+NH(a 1Delta): a combined experimental and theoretical study.

PubMed

Adam, L; Hack, W; McBane, G C; Zhu, H; Qu, Z-W; Schinke, R

2007-01-21

Experimental rate coefficients for the removal of NH(a (1)Delta) and ND(a (1)Delta) in collisions with H and D atoms are presented; all four isotope combinations are considered: NH+H, NH+D, ND+H, and ND+D. The experiments were performed in a quasistatic laser-flash photolysis/laser-induced fluorescence system at low pressures. NH(a (1)Delta) and ND(a (1)Delta) were generated by photolysis of HN(3) and DN(3), respectively. The total removal rate coefficients at room temperature are in the range of (3-5)x10(13) cm(3) mol(-1) s(-1). For two isotope combinations, NH+H and NH+D, quenching rate coefficients for the production of NH(X (3)Sigma(-)) or ND(X (3)Sigma(-)) were also determined; they are in the range of 1 x 10(13) cm(3) mol(-1) s(-1). The quenching rate coefficients directly reflect the strength of the Renner-Teller coupling between the (2)A(") and (2)A(') electronic states near linearity and so can be used to test theoretical models for describing this nonadiabatic process. The title reaction was modeled with a simple surface-hopping approach including a single parameter, which was adjusted to reproduce the quenching rate for NH+H; the same parameter value was used for all isotope combinations. The agreement with the measured total removal rate is good for all but one isotope combination. However, the quenching rates for the NH+D combination are only in fair (factor of 2) agreement with the corresponding measured data.

Kinetic studies of the yeast His-Asp phosphorelay signaling pathway

PubMed Central

Kaserer, Alla O.; Andi, Babak; Cook, Paul F.; West, Ann H.

2010-01-01

For both prokaryotic and eukaryotic His-Asp phosphorelay signaling pathways, the rates of protein phosphorylation and dephosphorylation determine the stimulus-to-response time frame. Thus, kinetic studies of phosphoryl group transfer between signaling partners are important for gaining a full understanding of how the system is regulated. In many cases, the phosphotransfer reactions are too fast for rates to be determined by manual experimentation. Rapid quench flow techniques thus provide a powerful method for studying rapid reactions that occur in the millisecond time frame. In this chapter, we describe experimental design and procedures for kinetic characterization of the yeast SLN1-YPD1-SSK1 osmoregulatory phosphorelay system using a rapid quench flow kinetic instrument. PMID:20946842

Low NO sub x heavy fuel combustor concept program

NASA Technical Reports Server (NTRS)

Russell, P.; Beal, G.; Hinton, B.

1981-01-01

A gas turbine technology program to improve and optimize the staged rich lean low NOx combustor concept is described. Subscale combustor tests to develop the design information for optimization of the fuel preparation, rich burn, quick air quench, and lean burn steps of the combustion process were run. The program provides information for the design of high pressure full scale gas turbine combustors capable of providing environmentally clean combustion of minimally of minimally processed and synthetic fuels. It is concluded that liquid fuel atomization and mixing, rich zone stoichiometry, rich zone liner cooling, rich zone residence time, and quench zone stoichiometry are important considerations in the design and scale up of the rich lean combustor.

The microdopant effects of surfactant elements on structure-phase transitions during the rapid quenched crystallization of Fe-C-based melts

NASA Astrophysics Data System (ADS)

Polukhin, V. A.; Belyakova, R. M.; Rigmant, L. K.

2008-02-01

The nature of microdopant effects of surfactant Te and H2 reagents on structure-phase transitions in rapidly quenched and crystallized eutectic Fe-C-based melts were studied by experimental and computer methods. On the base of results of statistic-geometrical analysis the new information about the structure changes in multi-scaling systems -from meso- to nano-ones were obtained.

The structural properties of PbF2 by molecular dynamics

NASA Astrophysics Data System (ADS)

Chergui, Y.; Nehaoua, N.; Telghemti, B.; Guemid, S.; Deraddji, N. E.; Belkhir, H.; Mekki, D. E.

2010-08-01

This work presents the use of molecular dynamics (MD) and the code of Dl_Poly, in order to study the structure of fluoride glass after melting and quenching. We are realized the processing phase liquid-phase, simulating rapid quenching at different speeds to see the effect of quenching rate on the operation of the devitrification. This technique of simulation has become a powerful tool for investigating the microscopic behaviour of matter as well as for calculating macroscopic observable quantities. As basic results, we calculated the interatomic distance, angles and statistics, which help us to know the geometric form and the structure of PbF2. These results are in experimental agreement to those reported in literature.

Correlation Functions and Glass Structure

NASA Astrophysics Data System (ADS)

Chergui, Y.; Nehaoua, N.; Telghemti, B.; Guemid, S.; Deraddji, N. E.; Belkhir, H.; Mekki, D. E.

2011-04-01

This work presents the use of molecular dynamics (MD) and the code of Dl Poly, in order to study the structure of fluoride glass after melting and quenching. We are realized the processing phase liquid-phase, simulating rapid quenching at different speeds to see the effect of quenching rate on the operation of the devitrification. This technique of simulation has become a powerful tool for investigating the microscopic behaviour of matter as well as for calculating macroscopic observable quantities. As basic results, we calculated the interatomic distance, angles and statistics, which help us to know the geometric form and the structure of PbF2. These results are in experimental agreement to those reported in literature.

Short sample training behavior of Nb-Ti fibers at 4. 2 K

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

Wright, L.S.; Judd, B.A.; Ocampo, G.

Experimental results are presented for the stress required to cause quenching during successive runs when bare fibers of Nb-Ti are carrying subcritical currents with no cross field. The data fall into two distinct regimes attributed to regions of magnetic flux stability and instability. Microplastic deformation is believed to supply the energy to initiate the flux jump process in the magnetic instability regime, and is the only source of heat available for triggering a quench when the fiber is magnetically stable. In both cases, quenching is observed at stresses well below the mechanically observed elastic limit. Simple techniques for one-step trainingmore » and detraining are also described.« less

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.

Spin precession in spin-orbit coupled weak links: Coulomb repulsion and Pauli quenching

NASA Astrophysics Data System (ADS)

Shekhter, R. I.; Entin-Wohlman, O.; Jonson, M.; Aharony, A.

2017-12-01

A simple model for the transmission of pairs of electrons through a weak electric link in the form of a nanowire made of a material with strong electron spin-orbit interaction (SOI) is presented, with emphasis on the effects of Coulomb interactions and the Pauli exclusion principle. The constraints due to the Pauli principle are shown to "quench" the coherent SOI-induced precession of the spins when the spatial wave packets of the two electrons overlap significantly. The quenching, which results from the projection of the pair's spin states onto spin-up and spin-down states on the link, breaks up the coherent propagation in the link into a sequence of coherent hops that add incoherently. Applying the model to the transmission of Cooper pairs between two superconductors, we find that in spite of Pauli quenching, the Josephson current oscillates with the strength of the SOI, but may even change its sign (compared to the limit of the Coulomb blockade, when the quenching is absent). Conditions for an experimental detection of these features are discussed.

TRAC-P1: an advanced best estimate computer program for PWR LOCA analysis. I. Methods, models, user information, and programming details

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

Not Available

1978-05-01

The Transient Reactor Analysis Code (TRAC) is being developed at the Los Alamos Scientific Laboratory (LASL) to provide an advanced ''best estimate'' predictive capability for the analysis of postulated accidents in light water reactors (LWRs). TRAC-Pl provides this analysis capability for pressurized water reactors (PWRs) and for a wide variety of thermal-hydraulic experimental facilities. It features a three-dimensional treatment of the pressure vessel and associated internals; two-phase nonequilibrium hydrodynamics models; flow-regime-dependent constitutive equation treatment; reflood tracking capability for both bottom flood and falling film quench fronts; and consistent treatment of entire accident sequences including the generation of consistent initial conditions.more » The TRAC-Pl User's Manual is composed of two separate volumes. Volume I gives a description of the thermal-hydraulic models and numerical solution methods used in the code. Detailed programming and user information is also provided. Volume II presents the results of the developmental verification calculations.« less

Study design and percent recoveries of anthropogenic organic compounds with and without the addition of ascorbic acid to preserve water samples containing free chlorine, 2004-06

USGS Publications Warehouse

Valder, Joshua F.; Delzer, Gregory C.; Price, Curtis V.; Sandstrom, Mark W.

2008-01-01

The National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey (USGS) began implementing Source Water-Quality Assessments (SWQAs) in 2002 that focus on characterizing the quality of source water and finished water of aquifers and major rivers used by some of the larger community water systems in the United States. As used for SWQA studies, source water is the raw (ambient) water collected at the supply well prior to water treatment (for ground water) or the raw (ambient) water collected from the river near the intake (for surface water). Finished water is the water that is treated, which typically involves, in part, the addition of chlorine or other disinfection chemicals to remove pathogens, and is ready to be delivered to consumers. Finished water is collected before the water enters the distribution system. This report describes the study design and percent recoveries of anthropogenic organic compounds (AOCs) with and without the addition of ascorbic acid to preserve water samples containing free chlorine. The percent recoveries were determined by using analytical results from a laboratory study conducted in 2004 by the USGS's National Water Quality Laboratory (NWQL) and from data collected during 2004-06 for a field study currently (2008) being conducted by the USGS's NAWQA Program. The laboratory study was designed to determine if preserving samples with ascorbic acid (quenching samples) adversely affects analytical performance under controlled conditions. During the laboratory study, eight samples of reagent water were spiked for each of five analytical schedules evaluated. Percent recoveries from these samples were then compared in two ways: (1) four quenched reagent spiked samples analyzed on day 0 were compared with four quenched reagent spiked samples analyzed on day 7 or 14, and (2) the combined eight quenched reagent spiked samples analyzed on day 0, 7, or 14 were compared with eight laboratory reagent spikes (LRSs). Percent recoveries from the quenched reagent spiked samples that were analyzed at two different times (day 0 and day 7 or 14) can be used to determine the stability of the quenched samples held for an amount of time representative of the normal amount of time between sample collection and analysis. The comparison between the quenched reagent spiked samples and the LRSs can be used to determine if quenching samples adversely affects the analytical performance under controlled conditions. The field study began in 2004 and is continuing today (February 2008) to characterize the effect of quenching on field-matrix spike recoveries and to better understand the potential oxidation and transformation of 277 AOCs. Three types of samples were collected from 11 NAWQA Study Units across the Nation: (1) quenched finished-water samples (not spiked), (2) quenched finished-water spiked samples, and (3) nonquenched finished-water spiked samples. Percent recoveries of AOCs in quenched and nonquenched finished-water spiked samples collected during 2004-06 are presented. Comparisons of percent recoveries between quenched and nonquenched spiked samples can be used to show how quenching affects finished-water samples. A maximum of 6 surface-water and 7 ground-water quenched finished-water spiked samples paired with nonquenched finished-water spiked samples were analyzed. Analytical results for the field study are presented in two ways: (1) by surface-water supplies or ground-water supplies, and (2) by use (or source) group category for surface-water and ground-water supplies. Graphical representations of percent recoveries for the quenched and nonquenched finished-water spiked samples also are presented.

Topological defects after a quench in a Bénard-Marangoni convection system.

PubMed

Casado, S; González-Viñas, W; Mancini, H; Boccaletti, S

2001-05-01

We report experimental evidence of the fact that, in a Bénard-Marangoni conduction-convection transition, the density of defects in the emerging structure scales as a power law in the quench time needed for the control parameter to ramp through the threshold. The obtained scaling exponents differ from the ones predicted and observed in the case in which the defects correspond to zeros in the amplitude of the global two-dimensional field.

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.

Cool Flame Quenching

NASA Technical Reports Server (NTRS)

Pearlman, Howard; Chapek, Richard

2001-01-01

Cool flame quenching distances are generally presumed to be larger than those associated with hot flames, because the quenching distance scales with the inverse of the flame propagation speed, and cool flame propagation speeds are often times slower than those associated with hot flames. To date, this presumption has never been put to a rigorous test, because unstirred, non-isothermal cool flame studies on Earth are complicated by natural convection. Moreover, the critical Peclet number (Pe) for quenching of cool flames has never been established and may not be the same as that associated with wall quenching due to conduction heat loss in hot flames, Pe approx. = 40-60. The objectives of this ground-based study are to: (1) better understand the role of conduction heat loss and species diffusion on cool flame quenching (i.e., Lewis number effects), (2) determine cool flame quenching distances (i.e, critical Peclet number, Pe) for different experimental parameters and vessel surface pretreatments, and (3) understand the mechanisms that govern the quenching distances in premixtures that support cool flames as well as hot flames induced by spark-ignition. Objective (3) poses a unique fire safety hazard if conditions exist where cool flame quenching distances are smaller than those associated with hot flames. For example, a significant, yet unexplored risk, can occur if a multi-stage ignition (a cool flame that transitions to a hot flame) occurs in a vessel size that is smaller than that associated with the hot quenching distance. To accomplish the above objectives, a variety of hydrocarbon-air mixtures will be tested in a static reactor at elevated temperature in the laboratory (1g). In addition, reactions with chemical induction times that are sufficiently short will be tested aboard NASA's KC-135 microgravity (mu-g) aircraft. The mu-g results will be compared to a numerical model that includes species diffusion, heat conduction, and a skeletal kinetic mechanism, following the work on diffusion-controlled cool flames by Fairlie et,al., 2000.

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

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.

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

Exploration of very high gradient cavities

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

Eremeev, Grigory

2011-07-01

Several of the 9-cell ILC cavities processed at Jlab within ongoing ILC R&D program have shown interesting behavior at high fields, such as mode mixing and sudden field emission turn-on during quench. Equipped with thermometry and oscillating superleak transducer (OST) system for quench detection, we couple our RF measurements with local dissipation measurements. In this contribution we report on our findings with high gradient SRF cavities.

Nonequilibrium Fractional Hall Response After a Topological Quench

NASA Astrophysics Data System (ADS)

Unal, Nur; Mueller, Erich; Oktel, M. O.

When a system is suddenly driven between two topologically different phases, aspects of the original topology survive the quench, but most physical observables (edge currents, Hall conductivity) appear to be non-universal. I will present the non-equilibrium Hall response of a Chern insulator following a quench where the mass term of a single Dirac cone changes sign. In the limit where the physics is dominated by a single Dirac cone, we theoretically find that the Hall conductivity universally changes by two-thirds of the quantum of conductivity. I will analyze this universal behavior by considering the Haldane model, and discuss experimental aspects for its observation in cold atoms. This work is supported by TUBITAK, NSFPHY-1508300, ARO-MURI W9111NF-14-1-0003.

Effect of quench on alpha/beta pulse shape discrimination of liquid scintillation cocktails.

PubMed

DeVol, Timothy A; Theisen, Christopher D; DiPrete, David P

2007-05-01

The objectives of this paper are (1) to illustrate that knowledge of the external quench parameter is insufficient to properly setup a pulse shape discriminating liquid scintillation counter (LSC) for quantitative measurement, (2) to illustrate dependence on pulse shape discrimination on the radionuclide (more than just radiation and energy), and (3) to compare the pulse shape discrimination (PSD) of two commercial instruments. The effects various quenching agents, liquid scintillation cocktails, radionuclides, and LSCs have on alpha/beta pulse shape discriminating liquid scintillation counting were quantified. Alpha emitting radionuclides (239)Pu and (241)Am and beta emitter (90)Sr/(90)Y were investigated to quantify the nuclide dependence on alpha/beta pulse shape discrimination. Also, chemical and color quenching agents, nitromethane, nitric acid, and yellow dye impact on alpha/beta pulse shape discrimination using PerkinElmer Optiphase "HiSafe" 2 and 3, and Ultima Gold AB liquid scintillation cocktails were determined. The prepared samples were counted on the PerkinElmer Wallac WinSpectral 1414 alpha/beta pulse shape discriminating LSC. It was found that for the same level of quench, as measured by the external quench parameter, different quench agents influenced the pulse shape discrimination and the pulse shape discrimination parameters differently. The radionuclide also affects alpha/beta pulse shape discrimination. By comparison with the PerkinElmer Tri-carb 3150 TR/AB, the Wallac 1414 exhibited better pulse shape discrimination capability under the same experimental conditions.

Study of the glass formation of high temperature superconductors

NASA Technical Reports Server (NTRS)

Ethridge, Edwin C.; Kaukler, William F.; Rolin, Terry

1992-01-01

A number of compositions of ceramic oxide high T(sub c) superconductors were elevated for their glass formation ability by means of rapid thermal analysis during quenching, optical, and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass; then, with subsequent devitrification, it was formed into a bulk crystalline superconductor by a series of processing methods.

LeRC in-house experimental research

NASA Technical Reports Server (NTRS)

Lyons, Valerie J.

1992-01-01

The topics covered include the following: LeRC in-house experimental research; combustion concepts; schedule for in-house experiments; lean premixed prevaporized combustion; comparisons of low NO(x) lean premixed/prevaporized data; rich burn/quick quench/lean burn (RQL); RQL combustion; fuel rich catalytic combustion; advanced diagnostics; and ceramic matrix liner test rig.

Transient slowing down relaxation dynamics of the supercooled dusty plasma liquid after quenching.

PubMed

Su, Yen-Shuo; Io, Chong-Wai; I, Lin

2012-07-01

The spatiotemporal evolutions of microstructure and motion in the transient relaxation toward the steady supercooled liquid state after quenching a dusty plasma Wigner liquid, formed by charged dust particles suspended in a low pressure discharge, are experimentally investigated through direct optical microscopy. It is found that the quenched liquid slowly evolves to a colder state with more heterogeneities in structure and motion. Hopping particles and defects appear in the form of clusters with multiscale cluster size distributions. Via the structure rearrangement induced by the reduced thermal agitation from the cold thermal bath after quenching, the temporarily stored strain energy can be cascaded through the network to different newly distorted regions and dissipated after transferring to nonlinearly coupled motions with different scales. It leads to the observed self-similar multiscale slowing down relaxation with power law increases of structural order and structural relaxation time, the similar power law decreases of particle motions at different time scales, and the stronger and slower fluctuations with increasing waiting time toward the new steady state.

Microstructural analysis of hot press formed 22MnB5 steel

NASA Astrophysics Data System (ADS)

Aziz, Nuraini; Aqida, Syarifah Nur; Ismail, Izwan

2017-10-01

This paper presents a microstructural study on hot press formed 22MnB5 steel for enhanced mechanical properties. Hot press forming process consists of simultaneous forming and quenching of heated blank. The 22MnB5 steel was processed at three different parameter settings: quenching time, water temperature and water flow rate. 22MnB5 was processed using 33 full factorial design of experiment (DOE). The full factorial DOE was designed using three factors of quenching time, water temperature and water flow rate at three levels. The factors level were quenching time range of 5 - 11 s, water temperature; 5 - 27°C and water flow rate; 20 - 40 L/min. The as-received and hot press forming processed steel was characterised for metallographic study and martensitic structure area percentage using JEOL Field Emission Scanning Electron Microscopic (FESEM). From the experimental finding, the hot press formed 22MnB5 steel consisted of 50 to 84% martensitic structure area. The minimum quenching time of 8 seconds was required to obtain formed sample with high percentage of martensite. These findings contribute to initial design of processing parameters in hot press forming of 22MnB5 steel blanks for automotive component.

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

Iu, Kaikong; Thomas, J.K.

Direct time-resolved studies of singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) phosphorescence ({sup 3}{Sigma}{sub g} {sup {minus}}O{sub 2} ({nu} = 0) {l arrow} {sup 1}{Delta}{sub g}O{sub 2} ({nu} = 0); 1,270 nm) in heterogeneous silica gel/cyclohexane systems are presented. Singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) is created through a photosensitization process on silica gel surfaces. The experimental results show that the lifetimes of singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) in both porous and compressed fumed silica/gel cyclohexane systems are significantly less than that in liquid cyclohexane. The shortened singlet molecular oxygen lifetime is due mainly to quenching bymore » adsorbed water and silanol groups on the silica gel surface. In addition, monoamines coadsorbed on the silica gel surface do not quench singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}); however, diamines such as DABCO or piperazine maintain their quenching activity, but the quenching kinetics are not of the Stern-Volmer type. The singlet molecular oxygen lifetime increases on loading the porous silica gel/cyclohexane system with monoamine. Coadsorption of piperazine increases quenching of {sup 1}{Delta}{sub g} O{sub 2} by DABCO.« less

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

Spectroscopic and theoretical investigation of oxali-palladium interactions with β-lactoglobulin.

PubMed

Ghalandari, Behafarid; Divsalar, Adeleh; Saboury, Ali Akbar; Haertlé, Thomas; Parivar, Kazem; Bazl, Roya; Eslami-Moghadam, Mahbube; Amanlou, Massoud

2014-01-24

The possibility of using a small cheap dairy protein, β-lactoglobulin (β-LG), as a carrier for oxali-palladium for drug delivery was studied. Their binding in an aqueous solution at two temperatures of 25 and 37°C was investigated using spectroscopic techniques in combination with a molecular docking study. Fluorescence intensity changes showed combined static and dynamic quenching during β-LG oxali-palladium binding, with the static mode being predominant in the quenching mechanism. The binding and thermodynamic parameters were determined by analyzing the results of quenching and those of the van't Hoff equation. According to obtained results the binding constants at two temperatures of 25 and 37°C are 3.3×10(9) M(-1) and 18.4×10(6) M(-1) respectively. Fluorescence resonance energy transfer (FRET) showed that the experimental results and the molecular docking results were coherent. An absence change of β-LG secondary structure was confirmed by the CD results. Molecular docking results agreed fully with the experimental results since the fluorescence studies also revealed the presence of two binding sites with a negative value for the Gibbs free energy of binding of oxali-palladium to β-LG. Furthermore, molecular docking and experimental results suggest that the hydrophobic effect plays a critical role in the formation of the oxali-palladium complex with β-LG. This agreement between molecular docking and experimental results implies that docking studies may be a suitable method for predicting and confirming experimental results, as shown in this study. Hence, the combination of molecular docking and spectroscopy methods is an effective innovative approach for binding studies, particularly for pharmacophores. Copyright © 2013 Elsevier B.V. All rights reserved.

Magnetic field dependent stability and quench behavior and degradation limits in conduction-cooled MgB2 wires and coils

PubMed Central

Ye, Liyang; Cruciani, Davide; Xu, Minfeng; Mine, Susumu; Amm, Kathleen; Schwartz, Justin

2015-01-01

Long lengths of metal/MgB2 composite conductors with high critical current density (Jc), fabricated by the power-in-tube (PIT) process, have recently become commercially available. Owing to its electromagnetic performance in the 20 K – 30 K range and relatively low cost, MgB2 may be attractive for a variety of applications. One of the key issues for magnet design is stability and quench protection, so the behavior of MgB2 wires and magnets must be understood before large systems can emerge. In this work, the stability and quench behavior of several conduction-cooled MgB2 wires are studied. Measurements of the minimum quench energy and normal zone propagation velocity are performed on short samples in a background magnetic field up to 3 T and on coils in self-field and the results are explained in terms of variations in the conductor architecture, electrical transport behavior, operating conditions (transport current and background magnetic field) and experimental setup (short sample vs small coil). Furthermore, one coil is quenched repeatedly with increasing hot-spot temperature until Jc is decreased. It is found that degradation during quenching correlates directly with temperature and not with peak voltage; a safe operating temperature limit of 260 K at the surface is identified. PMID:25883414

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.

Alleviating Luminescence Concentration Quenching in Upconversion Nanoparticles through Organic Dye Sensitization.

PubMed

Wei, Wei; Chen, Guanying; Baev, Alexander; He, Guang S; Shao, Wei; Damasco, Jossana; Prasad, Paras N

2016-11-23

The phenomenon of luminescence concentration quenching exists widely in lanthanide-based luminescent materials, setting a limit on the content of lanthanide emitter that can be used to hold the brightness. Here, we introduce a concept involving energy harvesting by a strong absorber and subsequent energy transfer to a lanthanide that largely alleviates concentration quenching. We apply this concept to Nd 3+ emitters, and we show both experimentally and theoretically that the optimal doping concentration of Nd 3+ in colloidal NaYF 4 :Nd upconverting nanoparticles is increased from 2 to 20 mol% when an energy harvestor organic dye (indocyanine green, ICG) is anchored onto the nanoparticle surface, resulting in ∼10 times upconversion brightness. Theoretical analysis indicated that a combination of efficient photon harvesting due to the large absorption cross section of ICG (∼30 000 times higher than that of Nd 3+ ), non-radiative energy transfer (efficiency ∼57%) from ICG to the surface bound Nd 3+ ions, and energy migration among the Nd 3+ ions was able to activate Nd 3+ ions inside the nanoparticle at a rate comparable with that of the pronounced short-range quenching interaction at elevated Nd 3+ concentrations. This resulted in the optimal concentration increase to produce significantly enhanced brightness. Theoretical modeling shows a good agreement with the experimental observation. This strategy can be utilized for a wide range of other lanthanide-doped nanomaterials being utilized for bioimaging and solar cell applications.

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.

Superradiance Transition and Nonphotochemical Quenching in Photosynthetic Complexes

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

Berman, Gennady Petrovich; Nesterov, Alexander; Lopez, Gustavo

2015-04-23

Photosynthetic organisms have evolved protective strategies to allow them to survive in cases of intense sunlight fluctuation with the development of nonphotochemical quenching (NPQ). This process allows light harvesting complexes to transfer the excess sunlight energy to non-damaging quenching channels. This report compares the NPQ process with the superradiance transition (ST). We demonstrated that the maximum of the NPQ efficiency is caused by the ST to the sink associated with the CTS. However, experimental verifications are required in order to determine whether or not the NPQ regime is associated with the ST transition for real photosynthetic complexes. Indeed, it canmore » happen that, in the photosynthetic apparatus, the NPQ regime occurs in the “non-optimal” region of parameters, and it could be independent of the ST.« less

Final Report on ITER Task Agreement 81-10

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

Brad J. Merrill

An International Thermonuclear Experimental Reactor (ITER) Implementing Task Agreement (ITA) on Magnet Safety was established between the ITER International Organization (IO) and the Idaho National Laboratory (INL) Fusion Safety Program (FSP) during calendar year 2004. The objectives of this ITA were to add new capabilities to the MAGARC code and to use this updated version of MAGARC to analyze unmitigated superconductor quench events for both poloidal field (PF) and toroidal field (TF) coils of the ITER design. This report documents the completion of the work scope for this ITA. Based on the results obtained for this ITA, an unmitigated quenchmore » event in an ITER larger PF coil does not appear to be as severe an accident as in an ITER TF coil.« less

Practical Approaches to Protein Folding and Assembly

PubMed Central

Walters, Jad; Milam, Sara L.; Clark, A. Clay

2009-01-01

We describe here the use of several spectroscopies, such as fluorescence emission, circular dichroism, and differential quenching by acrylamide, in examining the equilibrium and kinetic folding of proteins. The first section regarding equilibrium techniques provides practical information for determining the conformational stability of a protein. In addition, several equilibrium-folding models are discussed, from two-state monomer to four-state homodimer, providing a comprehensive protocol for interpretation of folding curves. The second section focuses on the experimental design and interpretation of kinetic data, such as burst-phase analysis and exponential fits, used in elucidating kinetic folding pathways. In addition, simulation programs are used routinely to support folding models generated by kinetic experiments, and the fundamentals of simulations are covered. PMID:19289201

Physics of Limiting Phenomena in Superconducting Microwave Resonators: Vortex Dissipation, Ultimate Quench and Quality Factor Degradation Mechanisms

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

Checchin, Mattia

Superconducting niobium accelerating cavities are devices operating in radio-frequency and able to accelerate charged particles up to energy of tera-electron-volts. Such accelerating structures are though limited in terms of quality factor and accelerating gradient, that translates--in some cases--in higher capital costs of construction and operation of superconducting rf accelerators. Looking forward for a new generation of more affordable accelerators, the physical description of limiting mechanisms in superconducting microwave resonators is discussed. In particular, the physics behind the dissipation introduced by vortices in the superconductor, the ultimate quench limitations and the quality factor degradation mechanism after a quench are described inmore » detail. One of the limiting factor of the quality factor is the dissipation introduced by trapped magnetic flux vortices. The radio-frequency complex response of trapped vortices in superconductors is derived by solving the motion equation for a magnetic flux line, assuming a bi-dimensional and mean free path-dependent Lorentzian-shaped pinning potential. The resulting surface resistance shows the bell-shaped trend as a function of the mean free path, in agreement with the experimental data observed. Such bell-shaped trend of the surface resistance is described in terms of the interplay of the two limiting regimes identified as pinning and flux flow regimes, for low and large mean free path values respectively. The model predicts that the dissipation regime--pinning- or flux-flow-dominated--can be tuned either by acting on the frequency or on the electron mean free path value. The effect of different configurations of pinning sites and strength on the vortex surface resistance are also discussed. Accelerating cavities are also limited by the quench of the superconductive state, which limits the maximum accelerating gradient achievable. The accelerating field limiting factor is usually associate d to the superheating field, which is intimately correlated to the penetration of magnetic flux vortices in the material. Experimental data for N-doped cavities suggest that uniform Ginzburg-Landau parameter cavities are statistically limited by the lower critical field, in terms of accelerating gradient. By introducing a Ginzburg-Landau parameter profile at the cavity rf surface--dirty layer--the accelerating gradient of superconducting resonators can be enhanced. The description of the physics behind the accelerating gradient enhancement as a consequence of the dirty layer is carried out by solving numerically the Ginzburg-Landau equations for the layered system. The enhancement is showed to be promoted by the higher energy barrier to vortex penetration, and by the enhanced lower critical field. Another serious threat to the quality factor during the cavity operation is the extra dissipation introduced by the quench. Such quality factor degradation mechanism due to the quench, is generated by the trapping of external magnetic flux at quench spot. The purely extrinsic origin of such extra dissipation is proven by the impossibility of decrease the quality factor by quenching in a magnetic field-free environment. Also, a clear relation of the dissipation introduced by quenching to the orientation of the applied magnetic field is observed. The full recover of the quality factor by re-quenching in compensated field is possible when the trapped flux at the quench spot is modest. On the contrary, when the trapped magnetic flux is too large, the quality factor degradation may become irreversible by this technique, likely due to the outward flux migration beyond the normal zone opening during the quench.« less

Physics of limiting phenomena in superconducting microwave resonators: Vortex dissipation, ultimate quench and quality factor degradation mechanisms

NASA Astrophysics Data System (ADS)

Checchin, Mattia

Superconducting niobium accelerating cavities are devices operating in radiofrequency and able to accelerate charged particles up to energy of tera-electron-volts. Such accelerating structures are though limited in terms of quality factor and accelerating gradient, that translates--in some cases--in higher capital costs of construction and operation of superconducting rf accelerators. Looking forward for a new generation of more affordable accelerators, the physical description of limiting mechanisms in superconducting microwave resonators is discussed. In particular, the physics behind the dissipation introduced by vortices in the superconductor, the ultimate quench limitations and the quality factor degradation mechanism after a quench are described in detail. One of the limiting factor of the quality factor is the dissipation introduced by trapped magnetic flux vortices. The radio-frequency complex response of trapped vortices in superconductors is derived by solving the motion equation for a magnetic flux line, assuming a bi-dimensional and mean free path-dependent Lorentzian-shaped pinning potential. The resulting surface resistance shows the bell-shaped trend as a function of the mean free path, in agreement with the experimental data observed. Such bell-shaped trend of the surface resistance is described in terms of the interplay of the two limiting regimes identified as pinning and flux flow regimes, for low and large mean free path values respectively. The model predicts that the dissipation regime--pinning- or flux-flow-dominated--can be tuned either by acting on the frequency or on the electron mean free path value. The effect of different configurations of pinning sites and strength on the vortex surface resistance are also discussed. Accelerating cavities are also limited by the quench of the superconductive state, which limits the maximum accelerating gradient achievable. The accelerating field limiting factor is usually associated to the superheating field, which is intimately correlated to the penetration of magnetic flux vortices in the material. Experimental data for N-doped cavities suggest that uniform Ginzburg-Landau parameter cavities are statistically limited by the lower critical field, in terms of accelerating gradient. By introducing a Ginzburg-Landau parameter profile at the cavity rf surface--dirty layer--the accelerating gradient of superconducting resonators can be enhanced. The description of the physics behind the accelerating gradient enhancement as a consequence of the dirty layer is carried out by solving numerically the Ginzburg-Landau equations for the layered system. The enhancement is showed to be promoted by the higher energy barrier to vortex penetration, and by the enhanced lower critical field. Another serious threat to the quality factor during the cavity operation is the extra dissipation introduced by the quench. Such quality factor degradation mechanism due to the quench, is generated by the trapping of external magnetic flux at the quench spot. The purely extrinsic origin of such extra dissipation is proven by the impossibility of decrease the quality factor by quenching in a magnetic field-free environment. Also, a clear relation of the dissipation introduced by quenching to the orientation of the applied magnetic field is observed. The full recover of the quality factor by re-quenching in compensated field is possible when the trapped flux at the quench spot is modest. On the contrary, when the trapped magnetic flux is too large, the quality factor degradation may become irreversible by this technique, likely due to the outward flux migration beyond the normal zone opening during the quench.

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.

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.

The Mechanical Property Data Base from an Air Force/Industry Cooperative Test Program on Advanced Aluminum Alloys (IN905XL and AL905XL Forgings)

DTIC Science & Technology

1991-12-01

850F FOR 2 HRS STEP 2 - 665F FOR 2 HRS STEP 3 - WARM WATER QUENCH STEP 4 - 230F FOR 24 HRS TABLE G5 TENSILE RESULTS FOR IN905XL FORGING COMPANY TEST...HRS STEP 2 - 665F FOR 2 HRS STEP 3 - WARM WATER QUENCH STEP 4 - 230F FOR 24 HRS 12 TABLE G6 COMPRESSION RESULTS FOR IN905XL FORGING COMPANY TEST...LONG 58.0 11.4 DYNAMICS (*) (*): HEAT TREATED TO THE FOLLOWING SCHEDULE: STEP 1 - 850F FOR 2 HRS STEP 2 - 665F FOR 2 HRS STEP 3 - WARM WATER QUENCH

Experimental Study of the Conditions for Quenching Forest Combustible Materials

NASA Astrophysics Data System (ADS)

Antonov, D. V.; Volkov, R. S.; Zhdanova, A. O.; Kuznetsov, G. V.; Strizhak, P. A.

2017-05-01

To confirm the possibility of quenching forest combustible materials by small volumes of water, experimental studies have been made of the processes of interaction of droplets, films, and aerosol flows of water with small sources of combustion of typical forest combustible materials — birch leaves, pine needles, birch and asp twigs. Model combustion sources in the form of cylinders of diameter 20-60 mm and height 40-100 mm were constructed. With the use of high-speed video recording, the characteristic times of thermal decomposition of forest combustibles and the times of suppressing combustion of these materials under various conditions of their interaction with water (pulsed supply of aerosol, injection of water ″mist″ with droplets of radius up to 100 μm, sequential supply of large drops of radius about 1.5 mm) have been determined. Volumes of water sufficient for suppressing combustion depending on the method of supplying it onto the surface of the reacting forest combustible have been determined. Estimates have been made of the nonreacted portion of the material by comparing the initial mass of the sample of the forest combustible with its final mass (upon quenching the material).

Magnetic moments and g-factors in odd-A Ho isotopes

NASA Astrophysics Data System (ADS)

Tabar, E.; Yakut, H.; Kuliev, A. A.; Quliyev, H.; Hocşgör, G.

2017-07-01

The ground-state magnetic moment, g K factor and quenching spin gyromagnetic ratio have been calculated using the microscopic method based on the Quasiparticle Phonon Nuclear Model (QPNM) for 155-169Ho nuclei for the first time. It is shown that the residual spin-spin interactions are responsible for the core polarization, and because of the core polarization the spin gyromagnetic factors are quenched. By considering the core polarization effects, a satisfactory agreement is obtained for the computed ground state g K factor, which gives an intrinsic contribution to the magnetic moments. In order to assess the collective contribution to the magnetic moments, the rotational gyromagnetic factors g R have been also calculated within the cranking approximation using the single particle wave function of the axially symmetric Woods-Saxon potential. For the ground-state magnetic moments of odd-proton 155-165Ho nuclei, a good description of the experimental data is obtained with an accuracy of 0.01-0.1 μ N. From systematic trends, the quenching spin gyromagnetic factor, g K factor and magnetic moment have also been theoretically predicted for 167,169Ho where there is no existing experimental data. Supported by Scientific and Technological Research Council of Turkey (TUBITAK) (115F564)

Fluorescence Manipulation by Gold Nanoparticles: From Complete Quenching to Extensive Enhancement

PubMed Central

2011-01-01

Background When a fluorophore is placed in the vicinity of a metal nanoparticle possessing a strong plasmon field, its fluorescence emission may change extensively. Our study is to better understand this phenomenon and predict the extent of quenching and/or enhancement of fluorescence, to beneficially utilize it in molecular sensing/imaging. Results Plasmon field intensities on/around gold nanoparticles (GNPs) with various diameters were theoretically computed with respect to the distance from the GNP surface. The field intensity decreased rapidly with the distance from the surface and the rate of decrease was greater for the particle with a smaller diameter. Using the plasmon field strength obtained, the level of fluorescence alternation by the field was theoretically estimated. For experimental studies, 10 nm GNPs were coated with polymer layer(s) of known thicknesses. Cypate, a near infrared fluorophore, was placed on the outermost layer of the polymer coated GNPs, artificially separated from the GNP at known distances, and its fluorescence levels were observed. The fluorescence of Cypate on the particle surface was quenched almost completely and, at approximately 5 nm from the surface, it was enhanced ~17 times. The level decreased thereafter. Theoretically computed fluorescence levels of the Cypate placed at various distances from a 10 nm GNP were compared with the experimental data. The trend of the resulting fluorescence was similar. The experimental results, however, showed greater enhancement than the theoretical estimates, in general. The distance from the GNP surface that showed the maximum enhancement in the experiment was greater than the one theoretically predicted, probably due to the difference in the two systems. Conclusions Factors affecting the fluorescence of a fluorophore placed near a GNP are the GNP size, coating material on GNP, wavelengths of the incident light and emitted light and intrinsic quantum yield of the fluorophore. Experimentally, we were able to quench and enhance the fluorescence of Cypate, by changing the distance between the fluorophore and GNP. This ability of artificially controlling fluorescence can be beneficially used in developing contrast agents for highly sensitive and specific optical sensing and imaging. PMID:21569249

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.

Glass formability of high T(sub c) Bi-Sr-Ca-Cu-O superconductors

NASA Technical Reports Server (NTRS)

Kaukler, William F.

1992-01-01

A number of compositions of ceramic oxide high T(sub c) superconductors were evaluated for their glass formation ability by means of rapid thermal analysis during quenching, optical and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass, then with subsequent devitrification it was formed into bulk crystalline superconductor by a series of processing methods.

Quench-induced Floquet topological p-wave superfluids.

PubMed

Foster, Matthew S; Gurarie, Victor; Dzero, Maxim; Yuzbashyan, Emil A

2014-08-15

Ultracold atomic gases in two dimensions tuned close to a p-wave Feshbach resonance were expected to exhibit topological superfluidity, but these were found to be experimentally unstable. We show that one can induce a topological Floquet superfluid if weakly interacting atoms are brought suddenly close ("quenched") to such a resonance, in the time before the instability kicks in. The resulting superfluid possesses Majorana edge modes, yet differs from a conventional Floquet system as it is not driven externally. Instead, the periodic modulation is self-generated by the dynamics.

Laser photochemical lead isotopes separation for harmless nuclear power engineering

NASA Astrophysics Data System (ADS)

Bokhan, P. A.; Fateev, N. V.; Kim, V. A.; Zakrevsky, D. E.

2016-09-01

The collisional quenching of the metastable 3 P 1,2 and 1 D 2 lead atoms is studied experimentally in the gas flow of the lead atoms, reagent-molecules and a carrier gas Ar. The experimental parameters were similar to the conditions that are required in the operation of the experimental setup for photochemical isotope separation. Excited atoms are generated under electron impact conditions created by a gas glow discharge through the mixture of gases and monitored photoelectrically by attenuation of atomic resonance radiation from hollow cathode 208Pb lamp. The decay of the excited atoms has been studied in the presence various molecules and total cross section data are reported. The flow tube measurements has allowed to separate the physical and chemical quenching channels and measure the rates of the chemical reaction excited lead with N2O, CH2Cl2, SF6 and CuBr molecules. These results are discussed in the prospects of the obtaining isotopically modified lead as a promising coolant in the reactors on the fast-neutron.

Integrated Experimental and Modelling Research for Non-Ferrous Smelting and Recycling Systems

NASA Astrophysics Data System (ADS)

Jak, Evgueni; Hidayat, Taufiq; Shishin, Denis; Mehrjardi, Ata Fallah; Chen, Jiang; Decterov, Sergei; Hayes, Peter

The chemistries of industrial pyrometallurgical non-ferrous smelting and recycling processes are becoming increasingly complex. Optimisation of process conditions, charge composition, temperature, oxygen partial pressure, and partitioning of minor elements between phases and different process streams require accurate description of phase equilibria and thermodynamics which are the focus of the present research. The experiments involve high temperature equilibration in controlled gas atmospheres, rapid quenching and direct measurement of equilibrium phase compositions with quantitative microanalytical techniques including electron probe X-ray microanalysis and Laser Ablation ICP-MS. The thermodynamic modelling is undertaken using computer package FactSage with the quasi-chemical model for the liquid slag phase and other advanced models. Experimental and modelling studies are combined into an integrated research program focused on the major elements Cu-Pb-Fe-O-Si-S system, slagging Al, Ca, Mg and other minor elements. The ongoing development of the research methodologies has resulted in significant advances in research capabilities. Examples of applications are given.

One-step synthesis of fluorescein modified nano-carbon for Pd(II) detection via fluorescence quenching.

PubMed

Panchompoo, Janjira; Aldous, Leigh; Baker, Matthew; Wallace, Mark I; Compton, Richard G

2012-05-07

Carbon black (CB) nanoparticles modified with fluorescein, a highly fluorescent molecule, were prepared using a facile and efficient methodology. Simply stirring CB in aqueous solution containing fluorescein resulted in the strong physisorption of fluorescein onto the CB surface. The resulting Fluorescein/CB was then characterised by means of X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), fluorescence microscopy and fluorescence spectroscopy. The optimum experimental conditions for fluorescence of Fluorescein/CB viz. fluorescence excitation and emission wavelengths, O(2) removal and the amount of Fluorescein/CB used, were investigated. The Fluorescein/CB was used as a fluorescent probe for the sensitive detection of Pd(II) in water, based on fluorescence quenching. The results demonstrated that the fluorescence intensity of Fluorescein/CB decreased with increasing Pd(II) concentration, and the fluorescence quenching process could be described by the Stern-Volmer equation. The limit of detection (LOD) for the fluorescence quenching of Fluorescein/CB by Pd(II) in aqueous solution was found to be 1.07 μM (based on 3σ). Last, approaches were studied for the removal of Fe(III) which interferes with the fluorescence quenching of Fluorescein/CB. Complexation of Fe(III) with salicylic acid was used to enhance and control the selectivity of Fluorescein/CB sensor towards Pd(II) in the presence of Fe(III).

Metastability versus collapse following a quench in attractive Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Golde, Jake; Ruhl, Joanna; Olshanii, Maxim; Dunjko, Vanja; Datta, Sumita; Malomed, Boris A.

2018-05-01

We consider a Bose-Einstein condensate (BEC) with attractive two-body interactions in a cigar-shaped trap, initially prepared in its ground state for a given negative scattering length, which is quenched to a larger absolute value of the scattering length. Using the mean-field approximation, we compute numerically, for an experimentally relevant range of aspect ratios and initial strengths of the coupling, two critical values of quench. One corresponds to the weakest attraction strength, the quench to which causes the system to collapse before completing even a single return from the narrow configuration (pericenter) in its breathing cycle. The other is a similar critical point for the occurrence of collapse before completing two returns. In the latter case, we also compute the limiting value, as we keep increasing the strength of the postquench attraction towards its critical value, of the time interval between the first two pericenters. We also use a Gaussian variational model to estimate the critical quenched attraction strength below which the system is stable against the collapse for long times. These time intervals and critical attraction strengths, apart from being fundamental properties of nonlinear dynamics of self-attractive BECs, may provide clues to the design of upcoming experiments that are trying to create robust BEC breathers.

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

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.

Fluorescence study on the interaction of human serum albumin with Butein in liposomes

NASA Astrophysics Data System (ADS)

Toprak, Mahmut

2016-02-01

The interaction of Butein with human serum albumin in L-egg lecithin phosphatidycholine (PC) liposome has been investigated by fluorescence and absorption spectroscopy. The results of the fluorescence measurement indicated that Butein effectively quenched the intrinsic fluorescence of HSA via static quenching. The Stern-Volmer plots in all the liposome solutions showed a positive deviation from the linearity. According to the thermodynamic parameters, the hydrophobic interactions appeared be the major interaction forces between Butein and HSA. The effect of Butein on the conformation of HSA was also investigated by the synchronous fluorescence under the same experimental conditions. In addition, the partition coefficient of the Butein in the PC liposomes was also determined by using the fluorescence quenching process. The obtained results can be of biological significance in pharmacology and clinical medicine.

Video luminescent barometry - The induction period

NASA Technical Reports Server (NTRS)

Uibel, Rory H.; Khalil, Gamal; Gouterman, Martin; Gallery, Jean; Callis, James B.

1993-01-01

Video monitoring of oxygen quenching of the photoluminescence of platinum octaethylporphyrin (PtOEP) in silicone polymer resin may be used to measure pressure distribution over an airfoil. A continuous increase of the luminescence intensity of PtOEP on exposure to the exciting light is known as the induction effect. The effect of several factors on PtOEP photoluminescence and the induction effect was investigated. The experimental apparatus is described and results are presented. It was observed that the relative induction amplitude and induction time increase at higher oxygen pressure and with thicker films. These observations may be explained if the singlet oxygen produced by oxygen quenching is consumed by the polymer and is therefore unavailable for further quenching. Researchers using this method for measuring pressure distribution on airfoil surfaces should be aware of the induction effect and its implications.

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.

An Intelligent Optical Dissolved Oxygen Measurement Method Based on a Fluorescent Quenching Mechanism.

PubMed

Li, Fengmei; Wei, Yaoguang; Chen, Yingyi; Li, Daoliang; Zhang, Xu

2015-12-09

Dissolved oxygen (DO) is a key factor that influences the healthy growth of fishes in aquaculture. The DO content changes with the aquatic environment and should therefore be monitored online. However, traditional measurement methods, such as iodometry and other chemical analysis methods, are not suitable for online monitoring. The Clark method is not stable enough for extended periods of monitoring. To solve these problems, this paper proposes an intelligent DO measurement method based on the fluorescence quenching mechanism. The measurement system is composed of fluorescent quenching detection, signal conditioning, intelligent processing, and power supply modules. The optical probe adopts the fluorescent quenching mechanism to detect the DO content and solves the problem, whereas traditional chemical methods are easily influenced by the environment. The optical probe contains a thermistor and dual excitation sources to isolate visible parasitic light and execute a compensation strategy. The intelligent processing module adopts the IEEE 1451.2 standard and realizes intelligent compensation. Experimental results show that the optical measurement method is stable, accurate, and suitable for online DO monitoring in aquaculture applications.

Mechanism of phosphorescence quenching in photomagnetic molecules determined by positron annihilation spectroscopy

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Eftekhari, A.; Naidu, S. V. N.

1994-01-01

Platinum Octaethyl Porphyrin (Pt.OEP) is an efficient phosphor under ultraviolet excitation. The phosphorescent triplet state (T(sub 1)) is readily quenched by the oxygen (O2) molecules. This phenomenon is being utilized as the basis for global air pressure measurements in aerodynamic facilities at various laboratories. The exact mechanism by which O2 molecules quench the (T(sub 1)-S(sub 0)) transitions is still unknown. The diamagnetic S(sub n) singlet states, which feed T(sub 1) states via intersystem crossings, would presumably not be affected by O2. It must be the magnetic T(sub 1) states, which can interact with the paramagnetic O2 molecules, that are affected. However, our positron lifetime and Doppler broadening studies suggest the formation of (S(sub n).02) complexes which can also eventually reduce the population of the T(sub 1) states (i.e. quench phosphorescence). This is possible since higher triplet states in (Pt-OEP) are admixed with the S(sub n) states via spin orbit interactions. The experimental procedures and the results of various measurements are discussed in this paper.

Mechanism of phosphorescence quenching in photomagnetic molecules determined by positron annihilation spectroscopy

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Eftekhari, A.; Naidu, S. V. N.

1994-01-01

Platinum Octaethyl Porphyrin (Pt.OEP) is an efficient phosphor under ultraviolet excitation. The phosphorescent triplet state (T(sub 1)) is readily quenched by the oxygen (O2) molecules. This phenomenon is being utilized as the basis for global air pressure measurements in aerodynamic facilities at various laboratories. The exact mechanism by which O2 molecules quench the (T(sub 1) - S(sub 0)) transitions is still unknown. The diamagnetic S(sub n) singlet states, which feed T(sub 1) states via intersystem crossings, would presumably not be affected by O2. It must be the magnetic T(sub 1) states, which can interact with the paramagnetic O2 molecules, that are affected. However, our positron lifetime and Doppler broadening studies suggest the formation of (S(sub n) central dot O2) complexes which can also eventually reduce the population of the T(sub 1) states (i.e. quench phosphorescence). This is possible since higher triplet states in (Pt.OEP) are admixed with the S(sub n) states via spin orbit interactions. The experimental procedures and the results of various measurements are discussed in this paper.

Automatic location of disruption times in JET

NASA Astrophysics Data System (ADS)

Moreno, R.; Vega, J.; Murari, A.

2014-11-01

The loss of stability and confinement in tokamak plasmas can induce critical events known as disruptions. Disruptions produce strong electromagnetic forces and thermal loads which can damage fundamental components of the devices. Determining the disruption time is extremely important for various disruption studies: theoretical models, physics-driven models, or disruption predictors. In JET, during the experimental campaigns with the JET-C (Carbon Fiber Composite) wall, a common criterion to determine the disruption time consisted of locating the time of the thermal quench. However, with the metallic ITER-like wall (JET-ILW), this criterion is usually not valid. Several thermal quenches may occur previous to the current quench but the temperature recovers. Therefore, a new criterion has to be defined. A possibility is to use the start of the current quench as disruption time. This work describes the implementation of an automatic data processing method to estimate the disruption time according to this new definition. This automatic determination allows both reducing human efforts to locate the disruption times and standardizing the estimates (with the benefit of being less vulnerable to human errors).

Interaction between Saikosaponin D, Paeoniflorin, and Human Serum Albumin.

PubMed

Liang, Guo-Wu; Chen, Yi-Cun; Wang, Yi; Wang, Hong-Mei; Pan, Xiang-Yu; Chen, Pei-Hong; Niu, Qing-Xia

2018-01-27

Saikosaponin D (SSD) and paeoniflorin (PF) are the major active constituents of Bupleuri Radix and Paeonia lactiflora Pall , respectively, and have been widely used in China to treat liver and other diseases for many centuries. We explored the binding of SSD/PF to human serum albumin (HSA) by using fluorospectrophotometry, circular dichroism (CD) and molecular docking. Both SSD and PF produced a conformational change in HSA. Fluorescence quenching was accompanied by a blue shift in the fluorescence spectra. Co-binding of PF and SSD also induced quenching and a conformational change in HSA. The Stern-Volmer equation showed that quenching was dominated by static quenching. The binding constant for ternary interaction was below that for binary interaction. Site-competitive experiments demonstrated that SSD/PF bound to site I (subdomain IIA) and site II (subdomain IIIA) in HSA. Analysis of thermodynamic parameters indicated that hydrogen bonding and van der Waals forces were mostly responsible for the binary association. Also, there was energy transfer upon binary interaction. Molecular docking supported the experimental findings in conformation, binding sites and binding forces.

Effect of gold nanoparticles on the fluorescence excitation spectrum of α-fetoprotein: Local environment dependent fluorescence quenching

NASA Astrophysics Data System (ADS)

Li, Jian-jun; Chen, Yu; Wang, A.-qing; Zhu, Jian; Zhao, Jun-wu

2011-01-01

The effect of colloid gold nanoparticles (AuNPs) on the fluorescence excitation spectrum of α-fetoprotein (AFP) has been investigated experimentally. The excitation spectral peaks of AFP with low concentration from 0.01 ng ml -1 to 12 ng ml -1 increase monotonically with increasing of AFP concentration. When some gold colloids were added to the AFP solution, the excitation peak at 285 nm decreases distinctly. By comparing the excitation peak intensity of AFP solution with gold colloids and without gold colloids at different AFP concentrations, the quenching effect from gold nanoparticle was more effective at lower AFP concentration. So the range of concentration from 0.01 ng ml -1 to 0.09 ng ml -1 will be the potential range of applications because of the higher sensitivity. The physical origin based on local field effect was investigated to illuminate this local environment dependent fluorescence quenching. The changing extent of quenching with different AFP concentrations can be attributed to the nonlinear decreasing of the local field factor of gold nanoparticles as a function of environmental dielectric constant.

An Intelligent Optical Dissolved Oxygen Measurement Method Based on a Fluorescent Quenching Mechanism

PubMed Central

Li, Fengmei; Wei, Yaoguang; Chen, Yingyi; Li, Daoliang; Zhang, Xu

2015-01-01

Dissolved oxygen (DO) is a key factor that influences the healthy growth of fishes in aquaculture. The DO content changes with the aquatic environment and should therefore be monitored online. However, traditional measurement methods, such as iodometry and other chemical analysis methods, are not suitable for online monitoring. The Clark method is not stable enough for extended periods of monitoring. To solve these problems, this paper proposes an intelligent DO measurement method based on the fluorescence quenching mechanism. The measurement system is composed of fluorescent quenching detection, signal conditioning, intelligent processing, and power supply modules. The optical probe adopts the fluorescent quenching mechanism to detect the DO content and solves the problem, whereas traditional chemical methods are easily influenced by the environment. The optical probe contains a thermistor and dual excitation sources to isolate visible parasitic light and execute a compensation strategy. The intelligent processing module adopts the IEEE 1451.2 standard and realizes intelligent compensation. Experimental results show that the optical measurement method is stable, accurate, and suitable for online DO monitoring in aquaculture applications. PMID:26690176

Percent recoveries of anthropogenic organic compounds with and without the addition of ascorbic acid to preserve finished-water samples containing free chlorine, 2004-10

USGS Publications Warehouse

Valder, Joshua F.; Delzer, Gregory C.; Bender, David A.; Price, Curtis V.

2011-01-01

This report presents finished-water matrix-spike recoveries of 270 anthropogenic organic compounds with and without the addition of ascorbic acid to preserve water samples containing free chlorine. Percent recoveries were calculated using analytical results from a study conducted during 2004-10 for the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey (USGS). The study was intended to characterize the effect of quenching on finished-water matrix-spike recoveries and to better understand the potential oxidation and transformation of 270 anthropogenic organic compounds. The anthropogenic organic compounds studied include those on analytical schedules 1433, 2003, 2033, 2060, 2020, and 4024 of the USGS National Water Quality Laboratory. Three types of samples were collected from 34 NAWQA locations across the Nation: (1) quenched finished-water samples (not spiked), (2) quenched finished-water matrix-spike samples, and (3) nonquenched finished-water matrix-spike samples. Percent recoveries of anthropogenic organic compounds in quenched and nonquenched finished-water matrix-spike samples are presented. Comparisons of percent recoveries between quenched and nonquenched spiked samples can be used to show how quenching affects finished-water samples. A maximum of 18 surface-water and 34 groundwater quenched finished-water matrix-spike samples paired with nonquenched finished-water matrix-spike samples were analyzed. Percent recoveries for the study are presented in two ways: (1) finished-water matrix-spike samples supplied by surface-water or groundwater, and (2) by use (or source) group category for surface-water and groundwater supplies. Graphical representations of percent recoveries for the quenched and nonquenched finished-water matrix-spike samples also are presented.

Reduction and Smelting of Vanadium Titanomagnetite Metallized Pellets

NASA Astrophysics Data System (ADS)

Wang, Shuai; Chen, Mao; Guo, Yufeng; Jiang, Tao; Zhao, Baojun

2018-04-01

Reduction and smelting of the vanadium titanomagnetite metallized pellets have been experimentally investigated in this study. By using the high-temperature smelting, rapid quenching, and electron probe x-ray microanalysis (EPMA) technique, the effects of basicity, reaction time, and graphite reductant amount were investigated. The vanadium contents in iron alloys increase with increasing basicity, reaction time, and graphite amount, whereas the FeO and V2O3 concentrations in the liquid phase decrease with the increase of graphite amount and reaction time. Increasing the reaction time and reductant content promotes the reduction of titanium oxide, whereas the reduction of titanium oxides can be suppressed with increasing the slag basicity. Titanium carbide (TiC) was not observed in all the quenched samples under the present conditions. The experimental results and the FactSage calculations are also compared in the present study.

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

Checchin, Mattia

Superconducting niobium accelerating cavities are devices operating in radio-frequency and able to accelerate charged particles up to energy of tera-electron-volts. Such accelerating structures are though limited in terms of quality factor and accelerating gradient, that translates--in some cases--in higher capital costs of construction and operation of superconducting rf accelerators. Looking forward for a new generation of more affordable accelerators, the physical description of limiting mechanisms in superconducting microwave resonators is discussed. In particular, the physics behind the dissipation introduced by vortices in the superconductor, the ultimate quench limitations and the quality factor degradation mechanism after a quench are described inmore » detail. One of the limiting factor of the quality factor is the dissipation introduced by trapped magnetic flux vortices. The radio-frequency complex response of trapped vortices in superconductors is derived by solving the motion equation for a magnetic flux line, assuming a bi-dimensional and mean free path-dependent Lorentzian-shaped pinning potential. The resulting surface resistance shows the bell-shaped trend as a function of the mean free path, in agreement with the experimental data observed. Such bell-shaped trend of the surface resistance is described in terms of the interplay of the two limiting regimes identified as pinning and flux flow regimes, for low and large mean free path values respectively. The model predicts that the dissipation regime--pinning- or flux-flow-dominated--can be tuned either by acting on the frequency or on the electron mean free path value. The effect of different configurations of pinning sites and strength on the vortex surface resistance are also discussed. Accelerating cavities are also limited by the quench of the superconductive state, which limits the maximum accelerating gradient achievable. The accelerating field limiting factor is usually associate d to the superheating field, which is intimately correlated to the penetration of magnetic flux vortices in the material. Experimental data for N-doped cavities suggest that uniform Ginzburg-Landau parameter cavities are statistically limited by the lower critical field, in terms of accelerating gradient. By introducing a Ginzburg-Landau parameter profile at the cavity rf surface--dirty layer--the accelerating gradient of superconducting resonators can be enhanced. The description of the physics behind the accelerating gradient enhancement as a consequence of the dirty layer is carried out by solving numerically the Ginzburg-Landau equations for the layered system. The enhancement is showed to be promoted by the higher energy barrier to vortex penetration, and by the enhanced lower critical field. Another serious threat to the quality factor during the cavity operation is the extra dissipation introduced by the quench. Such quality factor degradation mechanism due to the quench, is generated by the trapping of external magnetic flux at quench spot. The purely extrinsic origin of such extra dissipation is proven by the impossibility of decrease the quality factor by quenching in a magnetic field-free environment. Also, a clear relation of the dissipation introduced by quenching to the orientation of the applied magnetic field is observed. The full recover of the quality factor by re-quenching in compensated field is possible when the trapped flux at the quench spot is modest. On the contrary, when the trapped magnetic flux is too large, the quality factor degradation may become irreversible by this technique, likely due to the outward flux migration beyond the normal zone opening during the quench.« less

A comparative study of quantitative microsegregation analyses performed during the solidification of the Ni-base superalloy CMSX-10

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

Seo, Seong-Moon, E-mail: castme@kims.re.kr; Jeong, Hi-Won; Ahn, Young-Keun

Quantitative microsegregation analyses were systematically carried out during the solidification of the Ni-base superalloy CMSX-10 to clarify the methodological effect on the quantification of microsegregation and to fully understand the solidification microstructure. Three experimental techniques, namely, mushy zone quenching (MZQ), planar directional solidification followed by quenching (PDSQ), and random sampling (RS), were implemented for the analysis of microsegregation tendency and the magnitude of solute elements by electron probe microanalysis. The microprobe data and the calculation results of the diffusion field ahead of the solid/liquid (S/L) interface of PDSQ samples revealed that the liquid composition at the S/L interface is significantlymore » influenced by quenching. By applying the PDSQ technique, it was also found that the partition coefficients of all solute elements do not change appreciably during the solidification of primary γ. All three techniques could reasonably predict the segregation behavior of most solute elements. Nevertheless, the RS approach has a tendency to overestimate the magnitude of segregation for most solute elements when compared to the MZQ and PDSQ techniques. Moreover, the segregation direction of Cr and Mo predicted by the RS approach was found to be opposite from the results obtained by the MZQ and PDSQ techniques. This conflicting segregation behavior of Cr and Mo was discussed intensively. It was shown that the formation of Cr-rich areas near the γ/γ′ eutectic in various Ni-base superalloys, including the CMSX-10 alloy, could be successfully explained by the results of microprobe analysis performed on a sample quenched during the planar directional solidification of γ/γ′ eutectic. - Highlights: • Methodological effect on the quantification of microsegregation was clarified. • The liquid composition at the S/L interface was influenced by quenching. • The segregation direction of Cr varied depending on the experimental techniques. • Cr and Mo segregation in Ni-base superalloys was fully understood.« less

Interactions of cephalexin with bovine serum albumin: displacement reaction and molecular docking.

PubMed

Hamishehkar, Hamed; Hosseini, Soheila; Naseri, Abdolhossein; Safarnejad, Azam; Rasoulzadeh, Farzaneh

2016-01-01

Introduction: The drug-plasma protein interaction is a fundamental issue in guessing and checking the serious drug side effects related with other drugs. The purpose of this research was to study the interaction of cephalexin with bovine serum albumin (BSA) and displacement reaction using site probes. Methods: The interaction mechanism concerning cephalexin (CPL) with BSA was investigated using various spectroscopic methods and molecular modeling method. The binding sites number, n, apparent binding constant, K, and thermodynamic parameters, ΔG 0 , ΔH 0 , and ΔS 0 were considered at different temperatures. To evaluate the experimental results, molecular docking modeling was calculated. Results: The distance, r=1.156 nm between BSA and CPL were found in accordance with the Forster theory of non-radiation energy transfer (FRET) indicating energy transfer occurs between BSA and CPL. According to the binding parameters and ΔG 0 = negative values and ΔS 0 = 28.275 j mol -1 K -1 , a static quenching process is effective in the CPL-BSA interaction spontaneously. ΔG 0 for the CPL-BSA complex obtained from the docking simulation is -28.99 kj mol -1 , which is close to experimental ΔG of binding, -21.349 kj mol -1 that indicates a good agreement between the results of docking methods and experimental data. Conclusion: The outcomes of spectroscopic methods revealed that the conformation of BSA changed during drug-BSA interaction. The results of FRET propose that CPL quenches the fluorescence of BSA by static quenching and FRET. The displacement study showed that phenylbutazon and ketoprofen displaced CPL, indicating that its binding site on albumin is site I and Gentamicin cannot be displaced from the binding site of CPL. All results of molecular docking method agreed with the results of experimental data.

Parametric Study of HTS Coil Quench Protection Strategies

NASA Astrophysics Data System (ADS)

Seibert, Joseph; Zarnstorff, Michael; Zhai, Yuhu

2016-10-01

Next generation fusion devices require high magnetic fields to adequately contain burning plasmas. Use of high temperature superconducting (HTS) coils to generate these magnetic fields would lower energy cost of operation as well as increase stability of the superconducting state compared to low temperature superconducting coils. However, use of HTS coils requires developing quench protection strategies to prevent damage to the coils. One technique involves the utilization of copper discs and other conductors mutually coupled to the HTS coil to quickly extract the current from the coil. Another technique allows conduction between HTS turns to reduce the current in the coil during quench. This project describes a parametric study of the HTS coil and resistive-conductor setup in order to determine limiting cases of the geometry in an attempt to optimize current extraction and coil protection during quench scenarios. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.

The influence of visco-elastic processes on the generation of thermal stresses in quenched low alloy steel plates

NASA Astrophysics Data System (ADS)

Abbasi, F.

The visco-elastic effect in quenched specimens of 835M30 steel was described quantitatively by the use of the standard linear solid, which allowed the calculation of the thermal stress and strain during quenching in water, oil and in a martempering situation. The introduction of viscous flow into the calculation produced a marked improvement in the degree of agreement between the calculated and experimental residual stresses after an oil quench, although this was accompanied by a small reduction in the corresponding agreement in the case of water quench. The use of isothermal stress relaxation data in a continuous cooling situation was dealt with by the use of several models that cover a range of situations that varied from progressive hardening during the quench to one where recovery was predominant at all times. The use of martempering was of limited value, although an air cool following an intermediate salt bath treatment above the Ms temperature prevented the generation of thermal stresses during the formation of martensite. The use of an oil quench following the salt bath treatment was of no value, and none of the combinations of heat treatment possible during martempering significantly reduced the distortions to a lower level than was obtained by a conventional oil quench from 850°C. The mathematical model was also extended to include the effect of transformation plasticity, viz. the effect of an applied stress on the volume change that accompanied a phase transformation, as a consequence of heterogeneous plastic flow. This led to an excellent level of agreement between calculation and experiment in the case of residual stresses: it also produced adeterioration in the case of residual strains. Although some further work is required, the mathematical model has been developed sufficiently for it to be of practical value.

Comparison of Novel and Known Neuroprotectants for Treating Exposure to Different Types of Toxins

DTIC Science & Technology

2000-09-01

NMDA for 30 s followed by rapid quenching with the antagonist AP5. Immunoassays of the experimental samples indicated that concentrations of NCAM...for anti-NCAM immunoblotting; the migration pattern for the three isoforms is shown. (B) Paired samples of experimental and control slices were...used to determine the change in NCAM-180 immunoreactivity in experimental samples as compared to control samples ; the mean change (± SEM) among paired

Effect of Heat Treatment on the Hardness and Wear of Grinding Balls

NASA Astrophysics Data System (ADS)

Aissat, Sahraoui; Sadeddine, Abdelhamid; Bradai, Mohand Amokrane; Younes, Rassim; Bilek, Ali; Benabbas, Abderrahim

2017-09-01

The effect quenching and tempering by different regimes on Rockwell hardness and wear processes of grinding balls 50 and 70 mm in diameter made of two melts of chromium-molybdenum cast iron is studied. The heating temperature for quenching is 850, 950, and 1050°C; the tempering temperature is 250, 400, and 600°C. Iron is analyzed in an electron microscope. Diffraction patterns are obtained. A model of cast iron wear is suggested and compared to the Davis model and to experimental results. An optimum heat treatment regime is proposed.

Ultrasonic attenuation in pearlitic steel.

PubMed

Du, Hualong; Turner, Joseph A

2014-03-01

Expressions for the attenuation coefficients of longitudinal and transverse ultrasonic waves are developed for steel with pearlitic microstructure. This type of lamellar duplex microstructure influences attenuation because of the lamellar spacing. In addition, longitudinal attenuation measurements were conducted using an unfocused transducer with 10 MHz central frequency on the cross section of a quenched railroad wheel sample. The dependence of longitudinal attenuation on the pearlite microstructure is observed from the changes of longitudinal attenuation from the quenched tread surface to deeper locations. The results show that the attenuation value is lowest and relatively constant within the quench depth, then increases linearly. The experimental results demonstrate a reasonable agreement with results from the theoretical model. Ultrasonic attenuation provides an important non-destructive method to evaluate duplex microstructure within grains which can be implemented for quality control in conjunction with other manufacturing processes. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of Quenching Process on the Microstructure and Hardness of High-Carbon Martensitic Stainless Steel

NASA Astrophysics Data System (ADS)

Zhu, Qin-tian; Li, Jing; Shi, Cheng-bin; Yu, Wen-tao

2015-11-01

The microstructure and hardness of high-carbon martensitic stainless steel (HMSS) were investigated using thermal expansion analyzer, Thermo-calc, scanning electron microscope, x-ray diffraction, and Ultra-high temperature confocal microscope. The results indicate that the experimental steel should be austenitized in the temperature range of 1025-1075 °C, which can give a maximum hardness of 62 HRc with the microstructure consisting of martensite, retained austenite, and some undissolved carbides. With increasing austenitizing temperature, the amount of retained austenite increases, while the volume fraction of carbides increases first and then decreases. The starting temperature and finish temperature of martensite formation decrease with increasing cooling rates. Air-quenched samples can obtain less retained austenite, more compact microstructure, and higher hardness, compared with that of oil-quenched samples. For HMSS, the martensitic transformation takes place at some isolated areas with a slow nucleation rate.

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.

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.

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

Investigation of Oxygen-Induced Quenching of Phosphorescence in Photoexcited Aromatic Molecules by Positron Annihilation Spectroscopy

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Eftekhari, Abe

1996-01-01

Platinum OctaEthyl Porphyrin (Pt.OEP) is an efficient phosphor under ultraviolet excitation. The phosphorescent triplet state P(T(Sup 1)) is readily quenched by the oxygen O2 molecules. This phenomenon is being utilized as the basis for global air pressure measurements in aerodynamic facilities at various laboratories. The exact mechanism by which O2 molecules quench the P(T(Sup 1) approaches P(S(Sub O)) transitions is still unknown. The diamagnetic singlet states P(S(Sub n)), which feed P(T(Sub 1)) states via intersystem crossings, would presumably not be affected by O2. It must be only the magnetic P(T(Sub 1)) states, which can interact with the paramagnetic O2 molecules, that are affected. However, our positron lifetime and Doppler broadening studies suggest the formation of O2P(S(Sub n)), complexes which can also eventually reduce the population of the P(T(Sub 1)) states (i.e., quench phosphorescence). This reduction is possible because higher triplet states in (Pt.OEP) are admixed with the P(S(Sub 1)), states via spin orbit interactions. The experimental procedures and the results of various measurements are presented in this paper.

Quenching measurements and modeling of a boron-loaded organic liquid scintillator

DOE PAGES

Westerdale, S.; Xu, J.; Shields, E.; ...

2017-08-03

We present that organic liquid scintillators are used in a wide variety of applications in experimental nuclear and particle physics. Boron-loaded scintillators are particularly useful for detecting neutron captures, due to the high thermal neutron capture cross section of 10B. These scintillators are commonly used in neutron detectors, including the DarkSide-50 neutron veto, where the neutron may produce a signal when it scatters off protons in the scintillator or when it captures on 10B. Reconstructing the energy of these recoils is complicated by scintillation quenching. Understanding how nuclear recoils are quenched in these scintillators is an important and difficult problem.more » In this article, we present a set of measurements of neutron-induced proton recoils in a boron-loaded organic liquid scintillator at recoil energies ranging from 57–467 keV, and we compare these measurements to predictions from different quenching models. We find that a modified Birks' model whose denominator is quadratic in dE/dx best describes the measurements, with χ2/NDF=1.6. In conclusion, this result will help model nuclear recoil scintillation in similar detectors and can be used to improve their neutron tagging efficiency.« less

Quenching measurements and modeling of a boron-loaded organic liquid scintillator

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

Westerdale, S.; Xu, J.; Shields, E.

Organic liquid scintillators are used in a wide variety of applications in experimental nuclear and particle physics. Boron-loaded scintillators are particularly useful for detecting neutron captures, due to the high thermal neutron capture cross section of 10B. These scintillators are commonly used in neutron detectors, including the DarkSide-50 neutron veto, where the neutron may produce a signal when it scatters o protons in the scintillator or when it captures on 10B. Reconstructing the energy of these recoils is complicated by scintillation quenching. Understanding how nuclear recoils are quenched in these scintillators is an important and dicult problem. In this article,more » we present a set of measurements of neutron-induced proton recoils in a boron-loaded organic liquid scintillator at recoil energies ranging from 57-467 keV, and we compare these measurements to predictions from different quenching models. We and that a modified Birks' model whose denominator is quadratic in dE=dx best describes the measurements, with χ 2/NDF = 1:6. This result will help model nuclear recoil scintillation in similar detectors and can be used to improve their neutron tagging efficiency.« less

Quenching measurements and modeling of a boron-loaded organic liquid scintillator

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

Westerdale, S.; Xu, J.; Shields, E.

We present that organic liquid scintillators are used in a wide variety of applications in experimental nuclear and particle physics. Boron-loaded scintillators are particularly useful for detecting neutron captures, due to the high thermal neutron capture cross section of 10B. These scintillators are commonly used in neutron detectors, including the DarkSide-50 neutron veto, where the neutron may produce a signal when it scatters off protons in the scintillator or when it captures on 10B. Reconstructing the energy of these recoils is complicated by scintillation quenching. Understanding how nuclear recoils are quenched in these scintillators is an important and difficult problem.more » In this article, we present a set of measurements of neutron-induced proton recoils in a boron-loaded organic liquid scintillator at recoil energies ranging from 57–467 keV, and we compare these measurements to predictions from different quenching models. We find that a modified Birks' model whose denominator is quadratic in dE/dx best describes the measurements, with χ2/NDF=1.6. In conclusion, this result will help model nuclear recoil scintillation in similar detectors and can be used to improve their neutron tagging efficiency.« less

Quenching measurements and modeling of a boron-loaded organic liquid scintillator

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

Westerdale, S.; Xu, J.; Shields, E.

Organic liquid scintillators are used in a wide variety of applications in experimental nuclear and particle physics. Boron-loaded scintillators are particularly useful for detecting neutron captures, due to the high thermal neutron capture cross section ofmore » $$^{10}$$B. These scintillators are commonly used in neutron detectors, including the DarkSide-50 neutron veto, where the neutron may produce a signal when it scatters off protons in the scintillator or when it captures on $$^{10}$$B. Reconstructing the energy of these recoils is complicated by scintillation quenching. Understanding how nuclear recoils are quenched in these scintillators is an important and difficult problem. In this article, we present a set of measurements of neutron-induced proton recoils in a boron-loaded organic liquid scintillator at recoil energies ranging from 57--467 keV, and we compare these measurements to predictions from different quenching models. We find that a modified Birks' model whose denominator is quadratic in $dE/dx$ best describes the measurements, with $$\\chi^2$$/NDF$=1.6$. This result will help model nuclear recoil scintillation in similar detectors and can be used to improve their neutron tagging efficiency.« less

Heat-treating of materials

NASA Technical Reports Server (NTRS)

Widener, Edward L.

1992-01-01

The objective was to introduce those solid state transformations of material structures known as 'heat treatments' and to emphasize the commercial importance of common processes for metals as well as non-metals. Experimental procedures are explained for annealing, quenching, hardening, and temper.

Investigating the topological structure of quenched lattice QCD with overlap fermions using a multi-probing approximation

NASA Astrophysics Data System (ADS)

Zou, You-Hao; Zhang, Jian-Bo; Xiong, Guang-Yi; Chen, Ying; Liu, Chuan; Liu, Yu-Bin; Ma, Jian-Ping

2017-10-01

The topological charge density and topological susceptibility are determined by a multi-probing approximation using overlap fermions in quenched SU(3) gauge theory. Then we investigate the topological structure of the quenched QCD vacuum, and compare it with results from the all-scale topological density. The results are consistent. Random permuted topological charge density is used to check whether these structures represent underlying ordered properties. The pseudoscalar glueball mass is extracted from the two-point correlation function of the topological charge density. We study 3 ensembles of different lattice spacing a with the same lattice volume 163×32. The results are compatible with the results of all-scale topological charge density, and the topological structures revealed by multi-probing are much closer to all-scale topological charge density than those from eigenmode expansion. Supported by National Natural Science Foundation of China (NSFC) (11335001, 11275169, 11075167), It is also supported in part by the DFG and the NSFC (11261130311) through funds provided to the Sino-German CRC 110 "Symmetries and the Emergence of Structure in QCD". This work was also funded in part by National Basic Research Program of China (973 Program) (2015CB856700)

Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: II. High-strength, laminated Ag-sheathed Bi-2223 tapes

NASA Astrophysics Data System (ADS)

Shen, Tengming; Ye, Liyang; Higley, Hugh

2018-01-01

In article I of this series, we described a spiral coil quench technique for probing the influence of the superconductor stress and strain state during normal operation on its margin to degradation during a quench and applied to a Bi-2212 round wire. Here we extend this technique to study the failure mechanisms and limits of high-strength Bi-2223 tapes experiencing a quench while carrying a large current in a high magnetic field. In contrast to Bi-2212 magnets made via a wind-and-react technique for which bending strains can be ignored, Bi-2223 magnets are made with a react-and-wind technique for which bending strain is significant. The critical tensile stress of Bi-2223 tapes (type HT-NX) decreases from >440 MPa for straight samples to 185 MPa after being bent to a diameter D of 50 mm. For HT-NX tapes with D = 50 mm, the quench degradation limit, measured using maximum allowable temperature during a quench T allowable, is greater than 300 K for axial tensile stress {σ }a < 94 MPa; it decreases with increasing tensile axial stress {σ }a nonlinearly, dropping to 230 K for {σ }a = 125 MPa. T allow able ({σ }a) experimental data at D = 50 mm is consistently predicted by a general strain model that assumes that quench degradation in NX/Bi-2223 is driven by axial tensile strain in Bi-2223 filaments exceeding the irreversible strain limit. The T allowable ({σ }a) is then predicted for various D including D = 80 mm important for NMR magnets. The given T allowable (D,{σ }a) is easy to use and important for finding the balance between operation stress, and therefore magnetic field generation efficiency, and operation margin when designing a superconducting magnet using Bi-2223 tapes.

Frequency quenching of microwave-induced resistance oscillations in a high-mobility two-dimensional electron gas

NASA Astrophysics Data System (ADS)

Studenikin, S. A.; Sachrajda, A. S.; Gupta, J. A.; Wasilewski, Z. R.; Fedorych, O. M.; Byszewski, M.; Maude, D. K.; Potemski, M.; Hilke, M.; West, K. W.; Pfeiffer, L. N.

2007-10-01

The frequency dependence of microwave-induced resistance oscillations (MIROs) has been studied experimentally in high-mobility electron GaAs/AlGaAs structures to explore the limits at which these oscillations can be observed. It is found that in dc transport experiments at frequencies above 120GHz , MIROs start to quench, while above 230GHz , they completely disappear. The results will need to be understood theoretically but are qualitatively discussed within a model in which forced electronic charge oscillations (plasmons) play an intermediate role in the interaction process between the radiation and the single-particle electron excitations between Landau levels.

Multichannel quench-flow microreactor chip for parallel reaction monitoring.

PubMed

Bula, Wojciech P; Verboom, Willem; Reinhoudt, David N; Gardeniers, Han J G E

2007-12-01

This paper describes a multichannel silicon-glass microreactor which has been utilized to investigate the kinetics of a Knoevenagel condensation reaction under different reaction conditions. The reaction is performed on the chip in four parallel channels under identical conditions but with different residence times. A special topology of the reaction coils overcomes the common problem arising from the difference in pressure drop of parallel channels having different length. The parallelization of reaction coils combined with chemical quenching at specific locations results in a considerable reduction in experimental effort and cost. The system was tested and showed good reproducibility in flow properties and reaction kinetic data generation.

Single atom catalysts on amorphous supports: A quenched disorder perspective

NASA Astrophysics Data System (ADS)

Peters, Baron; Scott, Susannah L.

2015-03-01

Phenomenological models that invoke catalyst sites with different adsorption constants and rate constants are well-established, but computational and experimental methods are just beginning to provide atomically resolved details about amorphous surfaces and their active sites. This letter develops a statistical transformation from the quenched disorder distribution of site structures to the distribution of activation energies for sites on amorphous supports. We show that the overall kinetics are highly sensitive to the precise nature of the low energy tail in the activation energy distribution. Our analysis motivates further development of systematic methods to identify and understand the most reactive members of the active site distribution.

Investigation on interaction between Ligupurpuroside A and pepsin by spectroscopic and docking methods.

PubMed

Shen, Liangliang; Xu, Hong; Huang, Fengwen; Li, Yi; Xiao, Huafeng; Yang, Zhen; Hu, Zhangli; He, Zhendan; Zeng, Zheling; Li, Yinong

2015-01-25

Ligupurpuroside A is one of the major glycoside in Ku-Din-Cha, a type of Chinese functional tea. In order to better understand its digestion and metabolism in humans, the interaction between Ligupurpuroside A and pepsin has been investigated by fluorescence spectra, UV-vis absorption spectra and synchronous fluorescence spectra along with molecular docking method. The fluorescence experiments indicate that Ligupurpuroside A can effectively quench the intrinsic fluorescence of pepsin through a combined quenching way at the low concentration of Ligupurpuroside A, and a static quenching procedure at the high concentration. The binding constant, binding sites of Ligupurpuroside A with pepsin have been calculated. The thermodynamic analysis suggests that non-covalent reactions, including electrostatic force, hydrophobic interaction and hydrogen bond are the main forces stabilizing the complex. According to the Förster's non-radiation energy transfer theory, the binding distance between pepsin and Ligupurpuroside A was calculated to be 3.15 nm, which implies that energy transfer occurs between pepsin and Ligupurpuroside A. Conformation change of pepsin was observed from UV-vis absorption spectra and synchronous fluorescence spectra under experimental conditions. In addition, all these experimental results have been validated by the protein-ligand docking studies which show that Ligupurpuroside A is located in the cleft between the domains of pepsin. Copyright © 2014 Elsevier B.V. All rights reserved.

Anisotropic quantum quench in the presence of frustration or background gauge fields: A probe of bulk currents and topological chiral edge modes

NASA Astrophysics Data System (ADS)

Killi, Matthew; Trotzky, Stefan; Paramekanti, Arun

2012-12-01

Bosons and fermions, in the presence of frustration or background gauge fields, can form many-body ground states that support equilibrium charge or spin currents. Motivated by the experimental creation of frustration or synthetic gauge fields in ultracold atomic systems, we propose a general scheme by which making a sudden anisotropic quench of the atom tunneling across the lattice and tracking the ensuing density modulations provides a powerful and gauge-invariant route to probing diverse equilibrium current patterns. Using illustrative examples of trapped superfluid Bose and normal Fermi systems in the presence of artificial magnetic fluxes on square lattices, and frustrated bosons in a triangular lattice, we show that this scheme to probe equilibrium bulk current order works independent of particle statistics. We also show that such quenches can detect chiral edge modes in gapped topological states, such as quantum Hall or quantum spin Hall insulators.

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.

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.

Mathematical model of phase transformations and elastoplastic stress in the water spray quenching of steel bars

NASA Astrophysics Data System (ADS)

Nagasaka, Y.; Brimacombe, J. K.; Hawbolt, E. B.; Samarasekera, I. V.; Hernandez-Morales, B.; Chidiac, S. E.

1993-04-01

A mathematical model, based on the finite-element technique and incorporating thermo-elasto-plastic behavior during the water spray quenching of steel, has been developed. In the model, the kinetics of diffusion-dependent phase transformation and martensitic transformation have been coupled with the transient heat flow to predict the microstructural evolution of the steel. Furthermore, an elasto-plastic constitutive relation has been applied to calculate internal stresses resulting from phase changes as well as temperature variation. The computer code has been verified for internal consistency with previously published results for pure iron bars. The model has been applied to the water spray quenching of two grades of steel bars, 1035 carbon and nickel-chromium alloyed steel; the calculated temperature, hardness, distortion, and residual stresses in the bars agreed well with experimental measurements. The results show that the phase changes occurring during this process affect the internal stresses significantly and must be included in the thermomechanical model.

Quantifying exciton hopping in disordered media with quenching sites: Application to arrays of quantum dots

NASA Astrophysics Data System (ADS)

Miyazaki, Jun

2013-10-01

We present an analytical method for quantifying exciton hopping in an energetically disordered system with quenching sites. The method is subsequently used to provide a quantitative understanding of exciton hopping in a quantum dot (QD) array. Several statistical quantities that characterize the dynamics (survival probability, average number of distinct sites visited, average hopping distance, and average hopping rate in the initial stage) are obtained experimentally by measuring time-resolved fluorescence intensities at various temperatures. The time evolution of these quantities suggests in a quantitative way that at low temperature an exciton tends to be trapped at a local low-energy site, while at room temperature, exciton hopping occurs repeatedly, leading to a large hopping distance. This method will serve to facilitate highly efficient optoelectronic devices using QDs such as photovoltaic cells and light-emitting diodes, since exciton hopping is considered to strongly influence their operational parameters. The presence of a dark QD (quenching site) that exhibits fast decay is also quantified.

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

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.

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.

Rotational Quenching Study in Isovalent H+ + CO and H+ + CS Systems

NASA Astrophysics Data System (ADS)

Kaur, Rajwant; Dhilip Kumar, T. J.

2016-06-01

Cooling and trapping of polar molecules has attracted attention at cold and ultracold temperatures. Extended study of molecular inelastic collision processes of polar interstellar species with proton finds an important astrophysical application to model interstellar medium. Present study includes computation of rate coefficient for molecular rotational quenching process in proton collision with isovalent CO and CS molecules using quantum dynamical close-coupling calculations. Full dimensional ab initio potential energy surfaces have been computed for the ground state for both the systems using internally contracted multireference configuration interaction method and basis sets. Quantum scattering calculations for rotational quenching of isovalent species are studied in the rigid-rotor approximation with CX (X=O, S) bond length fixed at an experimental equilibrium value of 2.138 and 2.900 a.u., respectively. Asymptotic potentials are computed using the dipole and quadrupole moments, and the dipole polarizability components. The resulting long-range potentials with the short-range ab initio interaction potentials have been fitted to study the anisotropy of the rigid-rotor surface using the multipolar expansion coefficients. Rotational quenching cross-section and corresponding rates from j=4 level of CX to lower j' levels have been obtained and found to obey Wigner's threshold law at ultra cold temperatures.

Experimental Investigation of Gas/Slag/Matte/Spinel Equilibria in the Cu-Fe-O-S-Si System at 1473 K (1200 °C) and P(SO2) = 0.25 atm

NASA Astrophysics Data System (ADS)

Hidayat, Taufiq; Fallah-Mehrjardi, Ata; Hayes, Peter C.; Jak, Evgueni

2018-04-01

New experimental data were obtained on the gas/slag/matte/spinel equilibria in the Cu-Fe-O-S-Si system at 1473 K (1200 °C) and P(SO2) = 0.25 atm covering Cu concentrations in matte between 42 and 78 wt pct Cu. Accurate measurements were obtained using high-temperature equilibration and the rapid quenching technique, followed by electron-probe X-ray microanalysis of equilibrium phase compositions. The use of spinel substrates made to support the samples ensures equilibrium with this primary phase solid, eliminates crucible contamination, and facilitates direct gas-condensed phase equilibrium and high quenching rates. Particular attention was given to the confirmation of the achievement of equilibrium. The results quantify the relationship between Cu in matte and oxygen partial pressure, sulfur in matte, oxygen in matte, Fe/SiO2 at slag liquidus, sulfur in slag, and dissolved copper in slag.

Structure assignment, electronic properties, and magnetism quenching of endohedrally doped neutral silicon clusters, Si(n)Co (n = 10-12).

PubMed

Li, Yejun; Tam, Nguyen Minh; Claes, Pieterjan; Woodham, Alex P; Lyon, Jonathan T; Ngan, Vu Thi; Nguyen, Minh Tho; Lievens, Peter; Fielicke, André; Janssens, Ewald

2014-09-18

The structures of neutral cobalt-doped silicon clusters have been assigned by a combined experimental and theoretical study. Size-selective infrared spectra of neutral Si(n)Co (n = 10-12) clusters are measured using a tunable IR-UV two-color ionization scheme. The experimental infrared spectra are compared with calculated spectra of low-energy structures predicted at the B3P86 level of theory. It is shown that the Si(n)Co (n = 10-12) clusters have endohedral caged structures, where the silicon frameworks prefer double-layered structures encapsulating the Co atom. Electronic structure analysis indicates that the clusters are stabilized by an ionic interaction between the Co dopant atom and the silicon cage due to the charge transfer from the silicon valence sp orbitals to the cobalt 3d orbitals. Strong hybridization between the Co dopant atom and the silicon host quenches the local magnetic moment on the encapsulated Co atom.

Vibrational quenching of excitonic splittings in H-bonded molecular dimers: The electronic Davydov splittings cannot match experiment

NASA Astrophysics Data System (ADS)

Ottiger, Philipp; Leutwyler, Samuel; Köppel, Horst

2012-05-01

The S1/S2 state exciton splittings of symmetric doubly hydrogen-bonded gas-phase dimers provide spectroscopic benchmarks for the excited-state electronic couplings between UV chromophores. These have important implications for electronic energy transfer in multichromophoric systems ranging from photosynthetic light-harvesting antennae to photosynthetic reaction centers, conjugated polymers, molecular crystals, and nucleic acids. We provide laser spectroscopic data on the S1/S2 excitonic splitting Δexp of the doubly H-bonded o-cyanophenol (oCP) dimer and compare to the splittings of the dimers of (2-aminopyridine)2, [(2AP)2], (2-pyridone)2, [(2PY)2], (benzoic acid)2, [(BZA)2], and (benzonitrile)2, [(BN)2]. The experimental S1/S2 excitonic splittings are Δexp = 16.4 cm-1 for (oCP)2, 11.5 cm-1 for (2AP)2, 43.5 cm-1 for (2PY)2, and <1 cm-1 for (BZA)2. In contrast, the vertical S1/S2 energy gaps Δcalc calculated by the approximate second-order coupled cluster (CC2) method for the same dimers are 10-40 times larger than the Δexp values. The qualitative failure of this and other ab initio methods to reproduce the exciton splitting Δexp arises from the Born-Oppenheimer (BO) approximation, which implicitly assumes the strong-coupling case and cannot be employed to evaluate excitonic splittings of systems that are in the weak-coupling limit. Given typical H-bond distances and oscillator strengths, the majority of H-bonded dimers lie in the weak-coupling limit. In this case, the monomer electronic-vibrational coupling upon electronic excitation must be accounted for; the excitonic splittings arise between the vibronic (and not the electronic) transitions. The discrepancy between the BO-based splittings Δcalc and the much smaller experimental Δexp values is resolved by taking into account the quenching of the BO splitting by the intramolecular vibronic coupling in the monomer S1 ← S0 excitation. The vibrational quenching factors Γ for the five dimers (oCP)2, (2AP)2, (2AP)2, (BN)2, and (BZA)2 lie in the range Γ = 0.03-0.2. The quenched excitonic splittings Γ.Δcalc are found to be in very good agreement with the observed splittings Δexp. The vibrational quenching approach predicts reliable Δexp values for the investigated dimers, confirms the importance of vibrational quenching of the electronic Davydov splittings, and provides a sound basis for predicting realistic exciton splittings in multichromophoric systems.

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.

For Liability Purposes, Is a Student Worker an Employee?

ERIC Educational Resources Information Center

Franke, Ann H.

2008-01-01

Brian Lindsay, a chemistry major, participated in a summer research program at St. Olaf College. The 10-week program required him to work in a laboratory under the direction of a chemistry professor. Lindsay received a $3,500 stipend and free housing. On July 11, 2002, he was performing a procedure to clean, or "quench," a flask. The…

Charmonium excited state spectrum in lattice QCD

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

Jozef Dudek; Robert Edwards; Nilmani Mathur

2008-02-01

Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likelymore » a result of the quenched approximation.« less

Unitary n -designs via random quenches in atomic Hubbard and spin models: Application to the measurement of Rényi entropies

NASA Astrophysics Data System (ADS)

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

2018-02-01

We present a general framework for the generation of random unitaries based on random quenches in atomic Hubbard and spin models, forming approximate unitary n -designs, and their application to the measurement of Rényi entropies. We generalize our protocol presented in Elben et al. [Phys. Rev. Lett. 120, 050406 (2018), 10.1103/PhysRevLett.120.050406] to a broad class of atomic and spin-lattice models. We further present an in-depth numerical and analytical study of experimental imperfections, including the effect of decoherence and statistical errors, and discuss connections of our approach with many-body quantum chaos.

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.

Andreev Bound States Formation and Quasiparticle Trapping in Quench Dynamics Revealed by Time-Dependent Counting Statistics.

PubMed

Souto, R Seoane; Martín-Rodero, A; Yeyati, A Levy

2016-12-23

We analyze the quantum quench dynamics in the formation of a phase-biased superconducting nanojunction. We find that in the absence of an external relaxation mechanism and for very general conditions the system gets trapped in a metastable state, corresponding to a nonequilibrium population of the Andreev bound states. The use of the time-dependent full counting statistics analysis allows us to extract information on the asymptotic population of even and odd many-body states, demonstrating that a universal behavior, dependent only on the Andreev state energy, is reached in the quantum point contact limit. These results shed light on recent experimental observations on quasiparticle trapping in superconducting atomic contacts.

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.

Quantitative and discriminative analysis of nucleic acid samples using luminometric nonspecific nanoparticle methods

NASA Astrophysics Data System (ADS)

Pihlasalo, S.; Mariani, L.; Härmä, H.

2016-03-01

Homogeneous simple assays utilizing luminescence quenching and time-resolved luminescence resonance energy transfer (TR-LRET) were developed for the quantification of nucleic acids without sequence information. Nucleic acids prevent the adsorption of a protein to europium nanoparticles which is detected as a luminescence quenching of europium nanoparticles with a soluble quencher or as a decrease of TR-LRET from europium nanoparticles to the acceptor dye. Contrary to the existing methods based on fluorescent dye binding to nucleic acids, equal sensitivities for both single- (ssDNA) and double-stranded DNA (dsDNA) were measured and a detection limit of 60 pg was calculated for the quenching assay. The average coefficient of variation was 5% for the quenching assay and 8% for the TR-LRET assay. The TR-LRET assay was also combined with a nucleic acid dye selective to dsDNA in a single tube assay to measure the total concentration of DNA and the ratio of ssDNA and dsDNA in the mixture. To our knowledge, such a multiplexed assay is not accomplished with commercially available assays.Homogeneous simple assays utilizing luminescence quenching and time-resolved luminescence resonance energy transfer (TR-LRET) were developed for the quantification of nucleic acids without sequence information. Nucleic acids prevent the adsorption of a protein to europium nanoparticles which is detected as a luminescence quenching of europium nanoparticles with a soluble quencher or as a decrease of TR-LRET from europium nanoparticles to the acceptor dye. Contrary to the existing methods based on fluorescent dye binding to nucleic acids, equal sensitivities for both single- (ssDNA) and double-stranded DNA (dsDNA) were measured and a detection limit of 60 pg was calculated for the quenching assay. The average coefficient of variation was 5% for the quenching assay and 8% for the TR-LRET assay. The TR-LRET assay was also combined with a nucleic acid dye selective to dsDNA in a single tube assay to measure the total concentration of DNA and the ratio of ssDNA and dsDNA in the mixture. To our knowledge, such a multiplexed assay is not accomplished with commercially available assays. Electronic supplementary information (ESI) available: The labeling of amino modified polystyrene nanoparticles with Eu3+ chelate and the experimental details and results for the optimization of nucleic acid binding protein and for the ratiometric measurement of DNA and RNA with quenching assay. See DOI: 10.1039/c5nr09252c

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.

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.

Quench protection diode irradiation tests by the Texas Accelerator Center

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

Carcagno, R.; Weichold, M.; Welch, G.

1986-07-14

To date considerable progress has been made in the first stage of the TAC program to assess the use of Quench protection diodes (QPD) within the cold region of the SSC superconducting magnets. Our principle goal in this period was to experimentally obtain information that will assist us in designing apparatus for future tests. More specifically, we wished to address the following areas of uncertainty: operational difficulties associated with installing and operating an experiment at a nuclear reactor; diode behavior when subjected to neutron radiation while held close to the temperature of liquid nitrogen; and the extent to which diodesmore » can be annealed by heating them up to 593/degree/K. To gain information in these areas, we performed an irradiation of sixteen Westinghouse diodes at the Texas A and M Nuclear Science Center reactor. In the interest of avoiding the expense and long lead times associated with obtaining new equipment, we used apparatus that was on hand or which could be quickly obtained or constructed. Further tests of the irradiated diodes and analysis of the data already acquired will be continuing for some time, but the results already available will allow us to proceed with designing apparatus for accurate and reliable irradiation testing of diodes. The following is a summary of what we have learned in the three areas mentioned above, some cautions about interpreting the data, and the implications of this new information for our future activities. 14 figs., 1 tab.« less

Laser Light Scattering, from an Advanced Technology Development Program to Experiments in a Reduced Gravity Environment

NASA Technical Reports Server (NTRS)

Meyer, William V.; Tscharnuter, Walther W.; Macgregor, Andrew D.; Dautet, Henri; Deschamps, Pierre; Boucher, Francois; Zuh, Jixiang; Tin, Padetha; Rogers, Richard B.; Ansari, Rafat R.

1994-01-01

Recent advancements in laser light scattering hardware are described. These include intelligent single card correlators; active quench/active reset avalanche photodiodes; laser diodes; and fiber optics which were used by or developed for a NASA advanced technology development program. A space shuttle experiment which will employ aspects of these hardware developments is previewed.

Quantum quench in a p+ip superfluid: Winding numbers and topological states far from equilibrium

NASA Astrophysics Data System (ADS)

Foster, Matthew S.; Dzero, Maxim; Gurarie, Victor; Yuzbashyan, Emil A.

2013-09-01

We study the nonadiabatic dynamics of a two-dimensional p+ip superfluid following an instantaneous quantum quench of the BCS coupling constant. The model describes a topological superconductor with a nontrivial BCS (trivial BEC) phase appearing at weak- (strong-) coupling strengths. We extract the exact long-time asymptotics of the order parameter Δ(t) by exploiting the integrability of the classical p-wave Hamiltonian, which we establish via a Lax construction. Three different types of asymptotic behavior can occur depending upon the strength and direction of the interaction quench. We refer to these as the nonequilibrium phases {I, II, III}, characterized as follows. In phase I, the order parameter asymptotes to zero due to dephasing. In phase II, Δ→Δ∞, a nonzero constant. Phase III is characterized by persistent oscillations of Δ(t). For quenches within phases I and II, we determine the topological character of the asymptotic states. We show that two different formulations of the bulk topological winding number, although equivalent in the BCS or BEC ground states, must be regarded as independent out of equilibrium. The first winding number Q characterizes the Anderson pseudospin texture of the initial state; we show that Q is generically conserved. For Q≠0, this leads to the prediction of a “gapless topological” state when Δ asymptotes to zero. The presence or absence of Majorana edge modes in a sample with a boundary is encoded in the second winding number W, which is formulated in terms of the retarded Green's function. We establish that W can change following a quench across the quantum critical point. When the order parameter asymptotes to a nonzero constant, the final value of W is well defined and quantized. We discuss the implications for the (dis)appearance of Majorana edge modes. Finally, we show that the parity of zeros in the bulk out-of-equilibrium Cooper-pair distribution function constitutes a Z2-valued quantum number, which is nonzero whenever W≠Q. The pair distribution can in principle be measured using rf spectroscopy in an ultracold-atom realization, allowing direct experimental detection of the Z2 number. This has the following interesting implication: topological information that is experimentally inaccessible in the bulk ground state can be transferred to an observable distribution function when the system is driven far from equilibrium.

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.

[Photodissociation of Acetylene and Acetone using Step-Scan Time-Resolved FTIR Emission Spectroscopy

NASA Technical Reports Server (NTRS)

McLaren, Ian A.; Wrobel, Jacek D.

1997-01-01

The photodissociation of acetylene and acetone was investigated as a function of added quenching gas pressures using step-scan time-resolved FTIR emission spectroscopy. Its main components consist of Bruker IFS88, step-scan Fourier Transform Infrared (FTIR) spectrometer coupled to a flow cell equipped with Welsh collection optics. Vibrationally excited C2H radicals were produced from the photodissociation of acetylene in the unfocused experiments. The infrared (IR) emission from these excited C2H radicals was investigated as a function of added argon pressure. Argon quenching rate constants for all C2H emission bands are of the order of 10(exp -13)cc/molecule.sec. Quenching of these radicals by acetylene is efficient, with a rate constant in the range of 10(exp -11) cc/molecule.sec. The relative intensity of the different C2H emission bands did not change with the increasing argon or acetylene pressure. However, the overall IR emission intensity decreased, for example, by more than 50% when the argon partial pressure was raised from 0.2 to 2 Torr at fixed precursor pressure of 160mTorr. These observations provide evidence for the formation of a metastable C2H2 species, which are collisionally quenched by argon or acetylene. Problems encountered in the course of the experimental work are also described.

Rapid detection of trace amounts of surfactants using nanoparticles in fluorometric assays

NASA Astrophysics Data System (ADS)

Härmä, Harri; Laakso, Susana; Pihlasalo, Sari; Hänninen, Pekka; Faure, Bertrand; Rana, Subhasis; Bergström, Lennart

2010-01-01

Rapid microtiter assays that utilize the time-resolved fluorescence resonance energy transfer or quenching of dye-labeled proteins adsorbed onto the surfaces of polystyrene or maghemite nanoparticles have been developed for the detection and quantification of trace amounts of surfactants at concentrations down to 10 nM.Rapid microtiter assays that utilize the time-resolved fluorescence resonance energy transfer or quenching of dye-labeled proteins adsorbed onto the surfaces of polystyrene or maghemite nanoparticles have been developed for the detection and quantification of trace amounts of surfactants at concentrations down to 10 nM. Electronic supplementary information (ESI) available: Experimental details and Fig. S1 and S2. See DOI: 10.1039/b9nr00172g

Possible Many-Body Localization in a Long-Lived Finite-Temperature Ultracold Quasineutral Molecular Plasma

NASA Astrophysics Data System (ADS)

Sous, John; Grant, Edward

2018-03-01

We argue that the quenched ultracold plasma presents an experimental platform for studying the quantum many-body physics of disordered systems in the long-time and finite energy-density limits. We consider an experiment that quenches a plasma of nitric oxide to an ultracold system of Rydberg molecules, ions, and electrons that exhibits a long-lived state of arrested relaxation. The qualitative features of this state fail to conform with classical models. Here, we develop a microscopic quantum description for the arrested phase based on an effective many-body spin Hamiltonian that includes both dipole-dipole and van der Waals interactions. This effective model appears to offer a way to envision the essential quantum disordered nonequilibrium physics of this system.

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

Spectroscopy of Rb{sub 2} dimers in solid {sup 4}He

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

Moroshkin, P.; Hofer, A.; Ulzega, S.

We present experimental and theoretical studies of the absorption, emission, and photodissociation spectra of Rb{sub 2} molecules in solid helium. We have identified 11 absorption bands of Rb{sub 2}. All laser-excited molecular states are quenched by the interaction with the He matrix. The quenching results in efficient population of a metastable (1) {sup 3}{pi}{sub u} state, which emits fluorescence at 1042 nm. In order to explain the fluorescence at the forbidden transition and its time dependence we propose a new molecular exciplex Rb{sub 2}({sup 3}{pi}{sub u})He{sub 2}. We have also found evidence for the formation of diatomic bubble states followingmore » photodissociation of Rb{sub 2}.« less

Phase-change memory function of correlated electrons in organic conductors

NASA Astrophysics Data System (ADS)

Oike, H.; Kagawa, F.; Ogawa, N.; Ueda, A.; Mori, H.; Kawasaki, M.; Tokura, Y.

2015-01-01

Phase-change memory (PCM), a promising candidate for next-generation nonvolatile memories, exploits quenched glassy and thermodynamically stable crystalline states as reversibly switchable state variables. We demonstrate PCM functions emerging from a charge-configuration degree of freedom in strongly correlated electron systems. Nonvolatile reversible switching between a high-resistivity charge-crystalline (or charge-ordered) state and a low-resistivity quenched state, charge glass, is achieved experimentally via heat pulses supplied by optical or electrical means in organic conductors θ -(BEDT-TTF)2X . Switching that is one order of magnitude faster is observed in another isostructural material that requires faster cooling to kinetically avoid charge crystallization, indicating that the material's critical cooling rate can be useful guidelines for pursuing a faster correlated-electron PCM function.

Fluorescent component and complexation mechanism of extracellular polymeric substances during dye wastewater biotreatment by anaerobic granular sludge

NASA Astrophysics Data System (ADS)

Li, Na; Wei, Dong; Sun, Qunqun; Han, Xiao; Du, Bin; Wei, Qin

2018-02-01

In this study, methylene blue (MB) wastewater was biotreated by anaerobic granular sludge (AnGS), and the fluorescent components of extracellular polymeric substances (EPS) and complexation mechanism were evaluated. Based on the experimental data, the sorption of MB by both live and inactivated AnGS followed the pseudo-second-order model, and the adsorption isotherm conformed well to the Langmuir model. It was shown that the difference in the sorption of live and inactivated AnGS was not significant, indicating that the sorption is mainly a physical-chemical process and metabolically mediated diffusion is negligible. The interaction between EPS and MB was proved by three-dimensional excitation-emission matrix (3D-EEM) and synchronous fluorescence spectra. 3D-EEM indicated that protein (PN)-like substances were the main peaks of EPS, and gradually quenched with increase of MB concentrations. According to synchronous fluorescence spectra, the main fluorescence quenching was caused by PN-like and humic-like fractions, and belonged to the static type of quenching. FTIR spectra demonstrated that hydroxyl and amino groups played a major role in MB sorption.

Forced synchronization and asynchronous quenching in a thermo-acoustic system

NASA Astrophysics Data System (ADS)

Mondal, Sirshendu; Pawar, Samadhan A.; Sujith, Raman

2017-11-01

Forced synchronization, which has been extensively studied in theory and experiments, occurs through two different mechanisms known as phase locking and asynchronous quenching. The latter indicates the suppression of oscillation amplitude. In most practical combustion systems such as gas turbine engines, the main concern is high amplitude pressure oscillations, known as thermo-acoustic instability. Thermo-acoustic instability is undesirable and needs to be suppressed because of its damaging consequences to an engine. In the present study, a systematic experimental investigation of forced synchronization is performed in a prototypical thermo-acoustic system, a Rijke tube, in its limit cycle operation. Further, we show a qualitatively similar behavior using a reduced order model. In the phase locking region, the simultaneous occurrence of synchronization and resonant amplification leads to high amplitude pressure oscillations. However, a reduction in the amplitude of natural oscillations by about 78% of the unforced amplitude is observed when the forcing frequency is far lower than the natural frequency. This shows the possibility of suppression of the oscillation amplitude through asynchronous quenching in thermo-acoustic systems.

Binding of carbendazim to bovine serum albumin: Insights from experimental and molecular modeling studies

NASA Astrophysics Data System (ADS)

Li, Jinhua; Zhang, Yulei; Hu, Lin; Kong, Yaling; Jin, Changqing; Xi, Zengzhe

2017-07-01

Carbendazim (CBZ) is a widely used benzimidazole fungicide in agriculture to control a wide range of fruit and vegetable pathogens, which may lead to potential health hazards. To evaluate the potential toxicity of CBZ, the binding mechanism of bovine serum albumin (BSA) with CBZ was investigated by the fluorescence quenching technology, UV absorbance spectra, circular dichroism (CD), and molecular modeling. The fluorescence titration and UV absorbance spectra revealed that the fluorescence quenching mechanism of BSA by CBZ was a combined quenching process. In addition, the studies of CD spectra suggested that the binding of CBZ to BSA changed the secondary structure of protein. Furthermore, the thermodynamic functions of enthalpy change (ΔH0) and entropy change (ΔS0) for the reaction were calculated to be 24.87 kJ mol-1 and 162.95 J mol-1 K-1 according to Van't Hoff equation. These data suggested that hydrophobic interaction play a major role in the binding of CBZ to BSA, which was in good agreement with the result of molecular modeling study.

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

Experimental study on the warm forming and quenching behavior for hot stamping of high-strength aluminum alloys

NASA Astrophysics Data System (ADS)

Degner, J.; Horn, A.; Merklein, M.

2017-09-01

Within the last decades, stringent regulations on fuel consumption, CO2 emissions and product recyclability forced the automotive sector to implement new strategies within the field of car body manufacturing. Due to their low density and good corrosion resistance, aluminum became one of the most relevant lightweight materials. Recently, especially high- strength aluminum alloys for structural components gained importance. Since the low formability of these alloys limits their application, there is a need for novel process strategies in order to enhance the forming behavior. One promising approach is the hot stamping of aluminum alloys. The combination of quenching and forming in one step after solution heat treatment leads to a significant improvement of the formability. Furthermore, higher manufacturing accuracy can be achieved due to reduced spring back. Within this contribution, the influence of forming temperature on the subsequent material behavior and the heat transfer during quenching will be analyzed. Therefore, the mechanical and thermal material characteristics such as flow behavior and heat transfer coefficient during hot stamping are investigated.

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.

Quantum quench of Kondo correlations in optical absorption.

PubMed

Latta, C; Haupt, F; Hanl, M; Weichselbaum, A; Claassen, M; Wuester, W; Fallahi, P; Faelt, S; Glazman, L; von Delft, J; Türeci, H E; Imamoglu, A

2011-06-29

The interaction between a single confined spin and the spins of an electron reservoir leads to one of the most remarkable phenomena of many-body physics--the Kondo effect. Electronic transport measurements on single artificial atoms, or quantum dots, have made it possible to study the effect in great detail. Here we report optical measurements on a single semiconductor quantum dot tunnel-coupled to a degenerate electron gas which show that absorption of a single photon leads to an abrupt change in the system Hamiltonian and a quantum quench of Kondo correlations. By inferring the characteristic power-law exponents from the experimental absorption line shapes, we find a unique signature of the quench in the form of an Anderson orthogonality catastrophe, induced by a vanishing overlap between the initial and final many-body wavefunctions. We show that the power-law exponent that determines the degree of orthogonality can be tuned using an external magnetic field, which unequivocally demonstrates that the observed absorption line shape originates from Kondo correlations. Our experiments demonstrate that optical measurements on single artificial atoms offer new perspectives on many-body phenomena previously studied using transport spectroscopy only.

The effect of antiphase boundaries on the elastic properties of Ni-Mn-Ga austenite and premartensite

NASA Astrophysics Data System (ADS)

Seiner, Hanuš; Sedlák, Petr; Bodnárová, Lucie; Drahokoupil, Jan; Kopecký, Vít; Kopeček, Jaromír; Landa, Michal; Heczko, Oleg

2013-10-01

The evolution of elastic properties with temperature and magnetic field was studied in two differently heat-treated single crystals of the Ni-Mn-Ga magnetic shape memory alloy using resonant ultrasound spectroscopy. Quenching and slow furnace cooling were used to obtain different densities of antiphase boundaries. We found that the crystals exhibited pronounced differences in the c‧ elastic coefficient and related shear damping in high-temperature ferromagnetic phases (austenite and premartensite). The difference can be ascribed to the formation of fine magnetic domain patterns and pinning of the magnetic domain walls on antiphase boundaries in the material with a high density of antiphase boundaries due to quenching. The fine domain pattern arising from mutual interactions between antiphase boundaries and ferromagnetic domain walls effectively reduces the magnetocrystalline anisotropy and amplifies the contribution of magnetostriction to the elastic response of the material. As a result, the anomalous elastic softening prior to martensite transformation is significantly enhanced in the quenched sample. Thus, for any comparison of experimental data and theoretical calculations the microstructural changes induced by specific heat treatment must be taken into account.

The effect of antiphase boundaries on the elastic properties of Ni-Mn-Ga austenite and premartensite.

PubMed

Seiner, Hanuš; Sedlák, Petr; Bodnárová, Lucie; Drahokoupil, Jan; Kopecký, Vít; Kopeček, Jaromír; Landa, Michal; Heczko, Oleg

2013-10-23

The evolution of elastic properties with temperature and magnetic field was studied in two differently heat-treated single crystals of the Ni-Mn-Ga magnetic shape memory alloy using resonant ultrasound spectroscopy. Quenching and slow furnace cooling were used to obtain different densities of antiphase boundaries. We found that the crystals exhibited pronounced differences in the c' elastic coefficient and related shear damping in high-temperature ferromagnetic phases (austenite and premartensite). The difference can be ascribed to the formation of fine magnetic domain patterns and pinning of the magnetic domain walls on antiphase boundaries in the material with a high density of antiphase boundaries due to quenching. The fine domain pattern arising from mutual interactions between antiphase boundaries and ferromagnetic domain walls effectively reduces the magnetocrystalline anisotropy and amplifies the contribution of magnetostriction to the elastic response of the material. As a result, the anomalous elastic softening prior to martensite transformation is significantly enhanced in the quenched sample. Thus, for any comparison of experimental data and theoretical calculations the microstructural changes induced by specific heat treatment must be taken into account.

Bosons with Synthetic Rashba Spin-Orbit Coupling at Finite Power

NASA Astrophysics Data System (ADS)

Anderson, Brandon; Clark, Charles

2013-05-01

Isotropic spin-orbit couplings, such as Rashba in two dimensions, have a continuous symmetry that produces a large degeneracy in the momentum-space dispersion. This degeneracy leads to an enhanced density-of-states, producing novel phases in systems of bosonic atoms. This model is idealistic, however, in that the symmetry of the lasers will weakly break the continuous symmetry to a discrete one in experimental manifestations. This perturbation typically scales inversely with the optical power, and only at infinite power will ideal symmetry be restored. In this talk, we consider the effects of this weak symmetry breaking in a system of bosons at finite power with synthetic Rashba coupling. We solve the mean-field equations and find new phases, such as a stripe phase with a larger symmetry group. We then consider the experimentally relevant scheme where the spin-orbit fields are turned on adiabatically from an initial spin-polarized state. At intermediate power, stripe phases are found, while at sufficiently high power it appears that the system quenches to phases similar to that of the ideal limit. Techniques for optimizing the adiabatic ramping sequence are discussed. NSF PFC Grant PHY-0822671 and by the ARO under the DARPA OLE program.

Measurements of Enthalpy of Sublimation of Ne, N2, O2, Ar, CO2, Kr, Xe, and H2O using a Double Paddle Oscillator.

PubMed

Shakeel, Hamza; Wei, Haoyan; Pomeroy, Joshua M

2018-03-01

We report precise experimental values of the enthalpy of sublimation (Δ H s ) of quenched condensed films of neon (Ne), nitrogen (N 2 ), oxygen (O 2 ), argon (Ar), carbon dioxide (CO 2 ), krypton (Kr), xenon (Xe), and water (H 2 O) vapor using a single consistent measurement platform. The experiments are performed well below the triple point temperature of each gas and fall in the temperature range where existing experimental data is very limited. A 6 cm 2 and 400 µm thick double paddle oscillator (DPO) with high quality factor (Q ≈ 4 × 10 5 at 298K) and high frequency stability (33 parts per billion) is utilized for the measurements. The enthalpies of sublimation are derived by measuring the rate of mass loss during temperature programmed desorption. The mass change is detected due to change in the resonance frequency of the self-tracking oscillator. Our measurements typically remain within 10% of the available literature, theory, and National Institute of Standards and Technology (NIST) Web Thermo Tables ( WTT ) values, but are performed using an internally consistent method across different gases.

Plasma profile evolution during disruption mitigation via massive gas injection on MAST

NASA Astrophysics Data System (ADS)

Thornton, A. J.; Gibson, K. J.; Chapman, I. T.; Harrison, J. R.; Kirk, A.; Lisgo, S. W.; Lehnen, M.; Martin, R.; Scannell, R.; Cullen, A.; the MAST Team

2012-06-01

Massive gas injection (MGI) is one means of ameliorating disruptions in future devices such as ITER, where the stored energy in the plasma is an order of magnitude larger than in present-day devices. The penetration of the injected impurities during MGI in MAST is diagnosed using a combination of high-speed (20 kHz) visible imaging and high spatial (1 cm) and temporal (0.1 ms) resolution Thomson scattering (TS) measurements of the plasma temperature and density. It is seen that the rational surfaces, in particular q = 2, are the critical surfaces for disruption mitigation. The TS data shows the build-up of density on rational surfaces in the edge cooling period of the mitigation, leading to the collapse of the plasma in a thermal quench. The TS data are confirmed by the visible imaging, which shows filamentary structures present at the start of the thermal quench. The filamentary structures have a topology which matches that of a q = 2 field line in MAST, suggesting that they are located on the q = 2 surface. Linearized magnetohydrodynamic stability analysis using the TS profiles suggests that the large density build-up on the rational surfaces drives modes within the plasma which lead to the thermal quench. The presence of such modes is seen experimentally in the form of magnetic fluctuations on Mirnov coils and the growth of an n = 1 toroidal mode in the period prior to the thermal quench. These results support the observations of other machines that the 2/1 mode is the likely trigger for the thermal quench in a mitigated disruption and suggests that the mitigation process in spherical tokamaks is similar to that in conventional aspect ratio devices.

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.

Bacterial bioluminescence onset and quenching: a dynamical model for a quorum sensing-mediated property.

PubMed

Side, Domenico Delle; Nassisi, Vincenzo; Pennetta, Cecilia; Alifano, Pietro; Di Salvo, Marco; Talà, Adelfia; Chechkin, Aleksei; Seno, Flavio; Trovato, Antonio

2017-12-01

We present an effective dynamical model for the onset of bacterial bioluminescence, one of the most studied quorum sensing-mediated traits. Our model is built upon simple equations that describe the growth of the bacterial colony, the production and accumulation of autoinducer signal molecules, their sensing within bacterial cells, and the ensuing quorum activation mechanism that triggers bioluminescent emission. The model is directly tested to quantitatively reproduce the experimental distributions of photon emission times, previously measured for bacterial colonies of Vibrio jasicida , a luminescent bacterium belonging to the Harveyi clade, growing in a highly drying environment. A distinctive and novel feature of the proposed model is bioluminescence 'quenching' after a given time elapsed from activation. Using an advanced fitting procedure based on the simulated annealing algorithm, we are able to infer from the experimental observations the biochemical parameters used in the model. Such parameters are in good agreement with the literature data. As a further result, we find that, at least in our experimental conditions, light emission in bioluminescent bacteria appears to originate from a subtle balance between colony growth and quorum activation due to autoinducers diffusion, with the two phenomena occurring on the same time scale. This finding is consistent with a negative feedback mechanism previously reported for Vibrio harveyi .

Low NO(x) potential of gas turbine engines

NASA Technical Reports Server (NTRS)

Tacina, Robert R.

1990-01-01

The purpose is to correlate emission levels of gas turbine engines. The predictions of NO(x) emissions are based on a review of the literature of previous low NO(x) combustor programs and analytical chemical kinetic calculations. Concepts included in the literature review consisted of lean-premixed-prevaporized (LPP), rich burn/quick quench/lean burn (RQL), and direct injection. The NO(x) emissions were found to be an exponential function of adiabatic combustion temperature over a wide range of inlet temperatures, pressures and (lean) fuel-air ratios. A simple correlation of NO(x) formation with time was not found. The LPP and direct injection (using gaseous fuels) concepts have the lowest NO(x) emissions of the three concepts. The RQL data has higher values of NO(x) than the LPP concept, probably due to the stoichiometric temperatures and NO(x) production that occur during the quench step. Improvements in the quick quench step could reduce the NO(x) emissions to the LPP levels. The low NO(x) potential of LPP is offset by the operational disadvantages of its narrow stability limits and its susceptibility to autoignition/flashback. The Rich-Burn/Quick-Quench/Lean-Burn (RQL) and the direct injection concepts have the advantage of wider stability limits comparable to conventional combustors.

Interband coherence induced correction to Thouless pumping: possible observation in cold-atom systems

NASA Astrophysics Data System (ADS)

Raghava, Gudapati Naresh; Zhou, Longwen; Gong, Jiangbin

2017-08-01

In Thouless pump, the charge transport in a one-dimensional insulator over an adiabatic cycle is topologically quantized. For nonequilibrium initial states, however, interband coherence will induce a previously unknown contribution to Thouless pumping. Though not geometric in nature, this contribution is independent of the time scale of the pumping protocol. In this work, we perform a detailed analysis of our previous finding [H.L. Wang et al., Phys. Rev. B 91, 085420 (2015)] in an already available cold-atom setup. We show that initial states with interband coherence can be obtained via a quench of the system's Hamiltonian. Adiabatic pumping in the post-quench system are then examined both theoretically and numerically, in which the interband coherence is shown to play an important role and can hence be observed experimentally. By choosing adiabatic protocols with different switching-on rates, we also show that the contribution of interband coherence to adiabatic pumping can be tuned. It is further proposed that the interband coherence induced correction to Thouless pumping may be useful in capturing a topological phase transition point. All our results have direct experimental interests.

Fluorescence studies on native and bound to trifluraline soy bean Lb"a" in the enhanced N2 fixation.

PubMed

Kolev, K; Dolashka-Angelova, P

2001-10-01

The differences in the tryptophan (Trp) fluorescence of native (control) Lb"a" and experimental substance isolated from nodules of the Williams' soy beans variety treated with trifluraline at a concentration of 2.1 x 10(-10) M have been studied. A positively charged environment has been proved for the tryptophans of the native Lb"a" and a negative one for the tryptophans of the experimental Lb"a". The difference in the tryptophan emission spectra at lambdaex = 280 and 300 nm may be assigned to conformational alterations occurring in the experimental Lb"a". This is also confirmed by the greater energy transfer from tyrosine to tryptophan in the experimental Lb"a"--30% compared to the 10% in the native Lb"a". The value of the constant of acrylamide quenching (Ksv = 2.77 M(-1)) shows that the tryptophans are buried more deeply in the experimental Lb"a" than in the native Lb"a" (Ksv = 4 M(-1)). They are substantially lower than Ksv of the standard compound N-Ac-Trp-NH2 (16.30 M(-1)). The activation energy (Ea) of the thermal quenching of tryptophan fluorescence is higher for the experimental Lb"a" (37 kJ mol(-1)) as compared to the standard compound N-Ac-Trp-NH2 (24 kJ mol(-1)) and the native Lb "a" (32 kJ mol(-1)). The dissociation constant of the complex of trifluraline with Lb "a" (6.32 x 10(-11) M) has been determined as well as the stoichiometric ratio trifluraline/Lb"a" (1:1). The estimated nitrogenase activity (microM/gfrw h) and the total Lb (mg/gfrw) for trifluraline are higher as compared to those for the control.

Fluorescence studies on native and bound to trifluraline soy bean Lb "a" in the enhanced N 2 fixation

NASA Astrophysics Data System (ADS)

Kolev, Kolyo; Dolashka-Angelova, Pavlina

2001-10-01

The differences in the tryptophan (Trp) fluorescence of native (control) Lb "a" and experimental substance isolated from nodules of the 'Williams' soy beans variety treated with trifluraline at a concentration of 2.1×10 -10 M have been studied. A positively charged environment has been proved for the tryptophans of the native Lb "a" and a negative one for the tryptophans of the experimental Lb "a". The difference in the tryptophan emission spectra at λex=280 and 300 nm may be assigned to conformational alterations occurring in the experimental Lb "a". This is also confirmed by the greater energy transfer from tyrosine to tryptophan in the experimental Lb "a"—30% compared to the 10% in the native Lb "a". The value of the constant of acrylamide quenching ( Ksv=2.77 M -1) shows that the tryptophans are buried more deeply in the experimental Lb "a" than in the native Lb "a" ( Ksv=4 M -1). They are substantially lower than Ksv of the standard compound N-Ac-Trp-NH 2 (16.30 M -1). The activation energy ( Ea) of the thermal quenching of tryptophan fluorescence is higher for the experimental Lb "a" (37 kJ mol -1) as compared to the standard compound N-Ac-Trp-NH 2 (24 kJ mol -1) and the native Lb "a" (32 kJ mol -1). The dissociation constant of the complex of trifluraline with Lb "a" (6.32×10 -11 M) has been determined as well as the stoichiometric ratio trifluraline/Lb "a" (1:1). The estimated nitrogenase activity (μM/gfrw h) and the total Lb (mg/gfrw) for trifluraline are higher as compared to those for the control.

Mass and Environment as Drivers of Galaxy Evolution in SDSS and zCOSMOS and the Origin of the Schechter Function

NASA Astrophysics Data System (ADS)

Peng, Ying-jie; Lilly, Simon J.; Kovač, Katarina; Bolzonella, Micol; Pozzetti, Lucia; Renzini, Alvio; Zamorani, Gianni; Ilbert, Olivier; Knobel, Christian; Iovino, Angela; Maier, Christian; Cucciati, Olga; Tasca, Lidia; Carollo, C. Marcella; Silverman, John; Kampczyk, Pawel; de Ravel, Loic; Sanders, David; Scoville, Nicholas; Contini, Thierry; Mainieri, Vincenzo; Scodeggio, Marco; Kneib, Jean-Paul; Le Fèvre, Olivier; Bardelli, Sandro; Bongiorno, Angela; Caputi, Karina; Coppa, Graziano; de la Torre, Sylvain; Franzetti, Paolo; Garilli, Bianca; Lamareille, Fabrice; Le Borgne, Jean-Francois; Le Brun, Vincent; Mignoli, Marco; Perez Montero, Enrique; Pello, Roser; Ricciardelli, Elena; Tanaka, Masayuki; Tresse, Laurence; Vergani, Daniela; Welikala, Niraj; Zucca, Elena; Oesch, Pascal; Abbas, Ummi; Barnes, Luke; Bordoloi, Rongmon; Bottini, Dario; Cappi, Alberto; Cassata, Paolo; Cimatti, Andrea; Fumana, Marco; Hasinger, Gunther; Koekemoer, Anton; Leauthaud, Alexei; Maccagni, Dario; Marinoni, Christian; McCracken, Henry; Memeo, Pierdomenico; Meneux, Baptiste; Nair, Preethi; Porciani, Cristiano; Presotto, Valentina; Scaramella, Roberto

2010-09-01

We explore the simple inter-relationships between mass, star formation rate, and environment in the SDSS, zCOSMOS, and other deep surveys. We take a purely empirical approach in identifying those features of galaxy evolution that are demanded by the data and then explore the analytic consequences of these. We show that the differential effects of mass and environment are completely separable to z ~ 1, leading to the idea of two distinct processes of "mass quenching" and "environment quenching." The effect of environment quenching, at fixed over-density, evidently does not change with epoch to z ~ 1 in zCOSMOS, suggesting that the environment quenching occurs as large-scale structure develops in the universe, probably through the cessation of star formation in 30%-70% of satellite galaxies. In contrast, mass quenching appears to be a more dynamic process, governed by a quenching rate. We show that the observed constancy of the Schechter M* and αs for star-forming galaxies demands that the quenching of galaxies around and above M* must follow a rate that is statistically proportional to their star formation rates (or closely mimic such a dependence). We then postulate that this simple mass-quenching law in fact holds over a much broader range of stellar mass (2 dex) and cosmic time. We show that the combination of these two quenching processes, plus some additional quenching due to merging naturally produces (1) a quasi-static single Schechter mass function for star-forming galaxies with an exponential cutoff at a value M* that is set uniquely by the constant of proportionality between the star formation and mass quenching rates and (2) a double Schechter function for passive galaxies with two components. The dominant component (at high masses) is produced by mass quenching and has exactly the same M* as the star-forming galaxies but a faint end slope that differs by Δαs ~ 1. The other component is produced by environment effects and has the same M* and αs as the star-forming galaxies but an amplitude that is strongly dependent on environment. Subsequent merging of quenched galaxies will modify these predictions somewhat in the denser environments, mildly increasing M* and making αs slightly more negative. All of these detailed quantitative inter-relationships between the Schechter parameters of the star-forming and passive galaxies, across a broad range of environments, are indeed seen to high accuracy in the SDSS, lending strong support to our simple empirically based model. We find that the amount of post-quenching "dry merging" that could have occurred is quite constrained. Our model gives a prediction for the mass function of the population of transitory objects that are in the process of being quenched. Our simple empirical laws for the cessation of star formation in galaxies also naturally produce the "anti-hierarchical" run of mean age with mass for passive galaxies, as well as the qualitative variation of formation timescale indicated by the relative α-element abundances. Based on observations undertaken at the European Southern Observatory (ESO) Very Large Telescope (VLT) under Large Program 175.A-0839. Also based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, operated by AURA Inc., under NASA contract NAS 5-26555, with the Subaru Telescope, operated by the National Astronomical Observatory of Japan, with the telescopes of the National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation, and with the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique de France and the University of Hawaii.

Rotational quenching of H2CO by molecular hydrogen: cross-sections, rates and pressure broadening

NASA Astrophysics Data System (ADS)

Wiesenfeld, L.; Faure, A.

2013-07-01

We compute the rotational quenching rates of the first 81 rotational levels of ortho- and para-H2CO in collision with ortho- and para-H2, for a temperature range of 10-300 K. We make use of the quantum close-coupling and coupled-state scattering methods combined with the high accuracy potential energy surface of Troscompt et al. Rates are significantly different from the scaled rates of H2CO in collision with He; consequently, critical densities are notably lower. We compare a full close-coupling computation of pressure broadening cross-sections with experimental data and show that our results are compatible with the low-temperature measurements of Mengel & De Lucia, for a spin temperature of H2 around 50 K.

A rapid and sensitive assay for determination of doxycycline using thioglycolic acid-capped cadmium telluride quantum dots

NASA Astrophysics Data System (ADS)

Tashkhourian, Javad; Absalan, Ghodratollah; Jafari, Marzieh; Zare, Saber

2016-01-01

A rapid, simple and inexpensive spectrofluorimetric sensor for determination of doxycycline based on its interaction with thioglycolic acid-capped cadmium telluride quantum dots (TGA/CdTe QDs) has been developed. Under the optimum experimental conditions, the sensor exhibited a fast response time of <10 s. The results revealed that doxycycline could quench the fluorescence of TGA/CdTe QDs via electron transfer from the QDs to doxycycline through a dynamic quenching mechanism. The sensor permitted determination of doxycycline in a concentration range of 1.9 × 10-6-6.1 × 10-5 mol L-1 with a detection limit of 1.1 × 10-7 mol L-1. The sensor was applied for determination of doxycycline in honey and human serum samples.

Structural modeling of Ge6.25As32.5Se61.25 using a combination of reverse Monte Carlo and Ab initio molecular dynamics.

PubMed

Opletal, George; Drumm, Daniel W; Wang, Rong P; Russo, Salvy P

2014-07-03

Ternary glass structures are notoriously difficult to model accurately, and yet prevalent in several modern endeavors. Here, a novel combination of Reverse Monte Carlo (RMC) modeling and ab initio molecular dynamics (MD) is presented, rendering these complicated structures computationally tractable. A case study (Ge6.25As32.5Se61.25 glass) illustrates the effects of ab initio MD quench rates and equilibration temperatures, and the combined approach's efficacy over standard RMC or random insertion methods. Submelting point MD quenches achieve the most stable, realistic models, agreeing with both experimental and fully ab initio results. The simple approach of RMC followed by ab initio geometry optimization provides similar quality to the RMC-MD combination, for far fewer resources.

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.

Combined spectroscopies and molecular docking approach to characterizing the binding interaction of enalapril with bovine serum albumin.

PubMed

Pan, Dong-Qi; Jiang, Min; Liu, Ting-Ting; Wang, Qi; Shi, Jie-Hua

2017-06-01

The binding interaction between bovine serum albumin (BSA) and enalapril (ENPL) at the imitated physiological conditions (pH = 7.4) was investigated using UV-vis absorption spectroscopy (UV-vis), fluorescence emission spectroscopy (FES), synchronous fluorescence spectroscopy (SFS), Fourier transform infrared spectroscopy (FT-IR), circular dichroism (CD) and molecular docking methods. It can be deduced from the experimental results from the steady-state fluorescence spectroscopic titration that the intrinsic BSA fluorescence quenching mechanism induced by ENPL is static quenching, based on the decrease in the BSA quenching constants in the presence of ENPL with increase in temperature and BSA quenching rates >10 10  L mol -1  sec -1 . This result indicates that the ENPL-BSA complex is formed through an intermolecular interaction of ENPL with BSA. The main bonding forces for interaction of BSA and ENPL are van der Waal's forces and hydrogen bonding interaction based on negative values of Gibbs free energy change (ΔG 0 ), enthalpic change (ΔH 0 ) and entropic change (ΔS 0 ). The binding of ENPL with BSA is an enthalpy-driven process due to |ΔH°| > |TΔS°| in the binding process. The results of competitive binding experiments and molecular docking confirm that ENPL binds in BSA sub-domain IIA (site I) and results in a slight change in BSA conformation, but BSA still retains its α-helical secondary structure. Copyright © 2016 John Wiley & Sons, Ltd.

Results and analysis of the hot-spot temperature experiment for a cable-in-conduit conductor with thick conduit

NASA Astrophysics Data System (ADS)

Sedlak, Kamil; Bruzzone, Pierluigi

2015-12-01

In the design of future DEMO fusion reactor a long time constant (∼23 s) is required for an emergency current dump in the toroidal field (TF) coils, e.g. in case of a quench detection. This requirement is driven mainly by imposing a limit on forces on mechanical structures, namely on the vacuum vessel. As a consequence, the superconducting cable-in-conduit conductors (CICC) of the TF coil have to withstand heat dissipation lasting tens of seconds at the section where the quench started. During that time, the heat will be partially absorbed by the (massive) steel conduit and electrical insulation, thus reducing the hot-spot temperature estimated strictly from the enthalpy of the strand bundle. A dedicated experiment has been set up at CRPP to investigate the radial heat propagation and the hot-spot temperature in a CICC with a 10 mm thick steel conduit and a 2 mm thick glass epoxy outer electrical insulation. The medium size, ∅ = 18 mm, NbTi CICC was powered by the operating current of up to 10 kA. The temperature profile was monitored by 10 temperature sensors. The current dump conditions, namely the decay time constant and the quench detection delay, were varied. The experimental results show that the thick conduit significantly contributes to the overall enthalpy balance, and consequently reduces the amount of copper required for the quench protection in superconducting cables for fusion reactors.

Concurrent Flame Growth, Spread and Extinction over Composite Fabric Samples in Low Speed Purely Forced Flow in Microgravity

NASA Technical Reports Server (NTRS)

Zhao, Xiaoyang; T'ien, James S.; Ferkul, Paul V.; Olson, Sandra L.

2015-01-01

As a part of the NASA BASS and BASS-II experimental projects aboard the International Space Station, flame growth, spread and extinction over a composite cotton-fiberglass fabric blend (referred to as the SIBAL fabric) were studied in low-speed concurrent forced flows. The tests were conducted in a small flow duct within the Microgravity Science Glovebox. The fuel samples measured 1.2 and 2.2 cm wide and 10 cm long. Ambient oxygen was varied from 21% down to 16% and flow speed from 40 cm/s down to 1 cm/s. A small flame resulted at low flow, enabling us to observe the entire history of flame development including ignition, flame growth, steady spread (in some cases) and decay at the end of the sample. In addition, by decreasing flow velocity during some of the tests, low-speed flame quenching extinction limits were found as a function of oxygen percentage. The quenching speeds were found to be between 1 and 5 cm/s with higher speed in lower oxygen atmosphere. The shape of the quenching boundary supports the prediction by earlier theoretical models. These long duration microgravity experiments provide a rare opportunity for solid fuel combustion since microgravity time in ground-based facilities is generally not sufficient. This is the first time that a low-speed quenching boundary in concurrent spread is determined in a clean and unambiguous manner.

Study on the interactions between toxic nitroanilines and lysozyme by spectroscopic approaches and molecular modeling.

PubMed

Gu, Yunlan; Wang, Yanqing; Zhang, Hongmei

2018-05-05

Being exogenous environmental pollutants, nitroanilines (NAs) are highly toxic and have mutagenic and carcinogenic activity. Being lack of studies on interactions between NAs and lysozyme at molecular level, the binding interactions of lysozyme with o-nitroaniline (oNA), m-nitroaniline (mNA) and p-nitroaniline (pNA) were investigated by means of steady-state fluorescence, synchronous fluorescence, UV-vis absorption spectroscopy, as well as molecular modeling. The experimental results revealed that the fluorescence of lysozyme is quenched by oNA and mNA through a static quenching, while the fluorescence quenching triggered by pNA is a combined dynamic and static quenching. The number of binding sites (n) and the binding constant (K b ) corresponding thermodynamic parameters ΔH ⊖ , ΔS ⊖ , ΔG ⊖ at different temperatures were calculated. The reactions between NAs and lysozyme were spontaneous and entropy driven and the binding of NAs to lysozyme induced conformation changes of lysozyme. The difference of the position of -NO 2 group affected the binding and the binding constants K b decreased in the following pattern: K b (pNA) >K b (mNA) >K b (oNA). Molecular docking studies were performed to reveal the most favorable binding sites of NAs on lysozyme. Our recently results could offer mechanistic insights into the nature of the binding interactions between NAs and lysozyme and provide information about the toxicity risk of NAs to human health. Copyright © 2018 Elsevier B.V. All rights reserved.

Optimization of Feasibility Stage for Hydrogen/Deuterium Exchange Mass Spectrometry

NASA Astrophysics Data System (ADS)

Hamuro, Yoshitomo; Coales, Stephen J.

2018-03-01

The practice of HDX-MS remains somewhat difficult, not only for newcomers but also for veterans, despite its increasing popularity. While a typical HDX-MS project starts with a feasibility stage where the experimental conditions are optimized and the peptide map is generated prior to the HDX study stage, the literature usually reports only the HDX study stage. In this protocol, we describe a few considerations for the initial feasibility stage, more specifically, how to optimize quench conditions, how to tackle the carryover issue, and how to apply the pepsin specificity rule. Two sets of quench conditions are described depending on the presence of disulfide bonds to facilitate the quench condition optimization process. Four protocols are outlined to minimize carryover during the feasibility stage: (1) addition of a detergent to the quench buffer, (2) injection of a detergent or chaotrope to the protease column after each sample injection, (3) back-flushing of the trap column and the analytical column with a new plumbing configuration, and (4) use of PEEK (or PEEK coated) frits instead of stainless steel frits for the columns. The application of the pepsin specificity rule after peptide map generation and not before peptide map generation is suggested. The rule can be used not only to remove falsely identified peptides, but also to check the sample purity. A well-optimized HDX-MS feasibility stage makes subsequent HDX study stage smoother and the resulting HDX data more reliable. [Figure not available: see fulltext.

Nonlinear behavior of the tarka flute's distinctive sounds.

PubMed

Gérard, Arnaud; Yapu-Quispe, Luis; Sakuma, Sachiko; Ghezzi, Flavio; Ramírez-Ávila, Gonzalo Marcelo

2016-09-01

The Andean tarka flute generates multiphonic sounds. Using spectral techniques, we verify two distinctive musical behaviors and the nonlinear nature of the tarka. Through nonlinear time series analysis, we determine chaotic and hyperchaotic behavior. Experimentally, we observe that by increasing the blow pressure on different fingerings, peculiar changes from linear to nonlinear patterns are produced, leading ultimately to quenching.

Nonlinear behavior of the tarka flute's distinctive sounds

NASA Astrophysics Data System (ADS)

Gérard, Arnaud; Yapu-Quispe, Luis; Sakuma, Sachiko; Ghezzi, Flavio; Ramírez-Ávila, Gonzalo Marcelo

2016-09-01

The Andean tarka flute generates multiphonic sounds. Using spectral techniques, we verify two distinctive musical behaviors and the nonlinear nature of the tarka. Through nonlinear time series analysis, we determine chaotic and hyperchaotic behavior. Experimentally, we observe that by increasing the blow pressure on different fingerings, peculiar changes from linear to nonlinear patterns are produced, leading ultimately to quenching.

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.

[Study of scavenging activity of sorghum pigment to hydroxyl free radicals by fluorimetry].

PubMed

Zhang, Hai-rong; Wang, Wen-yan

2007-03-01

A natural product, sorghum pigment, consists of a number of important flavonoid derivatives, occurrs on the seed capsules or in the stems of many sorghums, and is widely applied in different fields of food, cosmetic and dyeing industries, It is important for scavenging hydroxyl free radicals and protection of human healthiness. Scavenging capacities of hydroxyl free radicals with sodium nitrite, quercetin and sorghum pigment were comparatively researched by fluorimetry, and the model of hydroxyl free radicals produced is based on the reaction of Cu2+ -catalyzed oxidation of ascorbic acid in the presence of hydrogen peroxide. The hydroxyl radicals react with benzoic acid, forming a fluorescent product, and the fluorescence intensity was determined by the concentration of hydroxybenzoic acid. The experimental results show that the sodium nitrite, quercetin and sorghum pigment have a quantity-effect relationship for scavenging hydroxyl free radicals, and sodium nitrite and quercetin in comparison with sorghum pigment have high antioxidant capacity. Finally, the quenching mechanisms were explored with sodium nitrite, sorghum pigment, and quercetin respectively. The sorghum pigment and sodium nitrite feature a dynamic quenching processes, while quercetin shows a static quenching processes. A reference method was provided for reasonable exploitation and utilization of sorghum pigment.

Microstructure Design of Tempered Martensite by Atomistically Informed Full-Field Simulation: From Quenching to Fracture

PubMed Central

Borukhovich, Efim; Du, Guanxing; Stratmann, Matthias; Boeff, Martin; Shchyglo, Oleg; Hartmaier, Alexander; Steinbach, Ingo

2016-01-01

Martensitic steels form a material class with a versatile range of properties that can be selected by varying the processing chain. In order to study and design the desired processing with the minimal experimental effort, modeling tools are required. In this work, a full processing cycle from quenching over tempering to mechanical testing is simulated with a single modeling framework that combines the features of the phase-field method and a coupled chemo-mechanical approach. In order to perform the mechanical testing, the mechanical part is extended to the large deformations case and coupled to crystal plasticity and a linear damage model. The quenching process is governed by the austenite-martensite transformation. In the tempering step, carbon segregation to the grain boundaries and the resulting cementite formation occur. During mechanical testing, the obtained material sample undergoes a large deformation that leads to local failure. The initial formation of the damage zones is observed to happen next to the carbides, while the final damage morphology follows the martensite microstructure. This multi-scale approach can be applied to design optimal microstructures dependent on processing and materials composition. PMID:28773791

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

Small-Molecule Photostabilizing Agents are Modifiers of Lipid Bilayer Properties

PubMed Central

Alejo, Jose L.; Blanchard, Scott C.; Andersen, Olaf S.

2013-01-01

Small-molecule photostabilizing or protective agents (PAs) provide essential support for the stability demands on fluorescent dyes in single-molecule spectroscopy and fluorescence microscopy. These agents are employed also in studies of cell membranes and model systems mimicking lipid bilayer environments, but there is little information about their possible effects on membrane structure and physical properties. Given the impact of amphipathic small molecules on bilayer properties such as elasticity and intrinsic curvature, we investigated the effects of six commonly used PAs—cyclooctatetraene (COT), para-nitrobenzyl alcohol (NBA), Trolox (TX), 1,4-diazabicyclo[2.2.2]octane (DABCO), para-nitrobenzoic acid (pNBA), and n-propyl gallate (nPG)—on bilayer properties using a gramicidin A (gA)-based fluorescence quench assay to probe for PA-induced changes in the gramicidin monomer↔dimer equilibrium. The experiments were done using fluorophore-loaded large unilamellar vesicles that had been doped with gA, and changes in the gA monomer↔dimer equilibrium were assayed using a gA channel-permeable fluorescence quencher (Tl+). Changes in bilayer properties caused by, e.g., PA adsorption at the bilayer/solution interface that alter the equilibrium constant for gA channel formation, and thus the number of conducting gA channels in the large unilamellar vesicle membrane, will be detectable as changes in the rate of Tl+ influx—the fluorescence quench rate. Over the experimentally relevant millimolar concentration range, TX, NBA, and pNBA, caused comparable increases in gA channel activity. COT, also in the millimolar range, caused a slight decrease in gA channel activity. nPG increased channel activity at submillimolar concentrations. DABCO did not alter gA activity. Five of the six tested PAs thus alter lipid bilayer properties at experimentally relevant concentrations, which becomes important for the design and analysis of fluorescence studies in cells and model membrane systems. We therefore tested combinations of COT, NBA, and TX; the combinations altered the fluorescence quench rate less than would be predicted assuming their effects on bilayer properties were additive. The combination of equimolar concentrations of COT and NBA caused minimal changes in the fluorescence quench rate. PMID:23746513

High Temperature Corrosion and Heat Transfer Studies of Zirconium-Silicide Coatings for Light Water Reactor Cladding Applications

NASA Astrophysics Data System (ADS)

Yeom, Hwasung

Experimental results investigating the feasibility of zirconium-silicide coating for accident tolerance of LWR fuel cladding coating was presented. The oxidation resistance of ZrSi2 appeared to be superior to bare Zircaloy-4 in high temperature air. It was shown that micro- and nanostructures consisting of alternating SiO2 and ZrO2 evolved during transient oxidation of ZrSi2, which was explained by spinodal phase decomposition of Zr-Si-O oxide. Coating optimization regarding oxidation resistance was performed mainly using magnetron sputter deposition method. ZrSi 2 coatings ( 3.9 microm) showed improvement of almost two orders of magnitude when compared to bare Zircaloy-4 after air-oxidation at 700 °C for 20-hours. Pre-oxidation of ZrSi2 coating at 700 °C for 5 h significantly mitigated oxygen diffusion in air-oxidation tests at 1000 °C for 1-hour and 1200 °C for 10-minutes. The ZrSi2 coating with the pre-oxidation was found to be the best condition to prevent oxide formation in Zircaloy-4 substrate in the steam condition even if the top surface of the coating was degraded by formation of zirconium-rich oxide layer. Only the ZrSiO4 phase, formed by exposing the ZrSi2 coating at 1400 °C in air, allowed for immobilization of silicon species in the oxide scale in the aqueous environments. A quench test facility was designed and built to study transient boiling heat transfer of modified Zircaloy-4 surfaces (e.g., roughened surfaces, oxidized surfaces, ZrSi2 coated surfaces) at various system conditions (e.g., elevated pressures and water subcooling). The minimum film boiling temperature increased with increasing system pressure and water subcooling, consistent with past literature. Quenching behavior was affected by the types of surface modification regardless of the environmental conditions. Quenching heat transfer was improved by the ZrSi 2 coating, a degree of surface oxidation (deltaox = 3 to 50 microm), and surface roughening (Ra 20 microm). A plausible hypothesis based on transient heat conduction models for liquid-solid contact in quenching process was proposed to explain the enhanced quenching performance. The theoretical model incorporated localized temperature behavior on superheated surface and elucidated bubble dynamics qualitatively, and predicts minimum film boiling temperature of oxidized Zirc-4 surfaces, which were in good agreement with experimental data.

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.

The Rate of Intramolecular Loop Formation in DNA and Polypeptides: The Absence of the Diffusion-Controlled Limit and Fractional Power-Law Viscosity Dependence

PubMed Central

Cheng, Ryan R.; Uzawa, Takanori; Plaxco, Kevin W.; Makarov, Dmitrii E.

2010-01-01

The problem of determining the rate of end-to-end collisions for polymer chains has attracted the attention of theorists and experimentalists for more than three decades. The typical theoretical approach to this problem has focused on the case where a collision is defined as any instantaneous fluctuation that brings the chain ends to within a specific capture distance. In this paper, we study the more experimentally relevant case, where the end-to-end collision dynamics are probed by measuring the excited state lifetime of a fluorophore (or other lumiphore) attached to one chain end and quenched by a quencher group attached to the other end. Under this regime, a “contact” is defined not by the chain ends approach to within some sharp cutoff but, instead, typically by an exponentially distance-dependent process. Previous theoretical models predict that, if quenching is sufficiently rapid, a diffusion-controlled limit is attained, where such measurements report on the probe-independent, intrinsic end-to-end collision rate. In contrast, our theoretical considerations, simulations, and an analysis of experimental measurements of loop closure rates in single-stranded DNA molecules all indicate that no such limit exists, and that the measured effective collision rate has a nontrivial, fractional power-law dependence on both the intrinsic quenching rate of the fluorophore and the solvent viscosity. We propose a simple scaling formula describing the effective loop closure rate and its dependence on the viscosity, chain length, and properties of the probes. Previous theoretical results are limiting cases of this more general formula. PMID:19780594

Nanosecond electric modification of order parameters

NASA Astrophysics Data System (ADS)

Borshch, Volodymyr

In this Dissertation, we study a nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field E modifies the tensor order parameter but does not change the orientation of the optic axis (director N̂). We use nematics with negative dielectric anisotropy with the electric field applied perpendicularly to N̂. The field changes the dielectric tensor at optical frequencies (optic tensor), due to the following mechanisms: (a) nanosecond creation of biaxial orientational order; (b) uniaxial modification of the orientational order that occurs over the timescales of tens of nanoseconds, and (c) quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field, E ˜ 108 V/m, on a timescale of nanoseconds. This work provides a useful guide in the current search of the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a timescale of nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of nanosecond electric modification of the order parameter (NEMOP) can be used in applications in which one needs to achieve ultrafast (nanosecond) changes of optical characteristics, such as birefringence.

Renner-Teller quantum dynamics of NH(a(1)Delta) + H reactions on the NH(2) A(2)A(1) and X(2)B(1) coupled surfaces.

PubMed

Defazio, P; Gamallo, P; González, M; Petrongolo, C

2010-09-16

Four reactions NH(a1Delta) + H′(2S) are investigated by the quantum mechanical real wavepacket method, taking into account nonadiabatic Renner-Teller (RT) and rovibronic Coriolis couplings between the involved states. We consider depletion (d) to N(2D) + H2(X1Sigmag+), exchange (e) to NH′(a1Delta) + H(2S), quenching (q) to NH(X3Sigma-) + H′(2S), and exchange-quenching (eq) to NH′(X3Sigma-) + H(2S). We extend our RT theory to a general AB + C collision using a geometry-dependent but very simple and empirical RT matrix element. Reaction probabilities, cross sections, and rate constants are presented, and RT results are compared with Born-Oppenheimer (BO), experimental, and semiclassical data. The nonadiabatic couplings open two new channels, (q) and (eq), and increase the (d) and (e) reactivity with respect to the BO one, when NH(a1Delta) is rotationally excited. In this case, the quantum cross sections are larger than the semiclassical ones at low collision energies. The calculated rate constants at 300 K are k(d) = 3.06, k(e) = 3.32, k(q) = 1.44, and k(eq) = 1.70 in 10(-11) cm3 s(-1) compared with the measured values k(d) = (3.2 =/- 1.7), k(q + eq) = (1.7 +/- 0.3), and k(total) = (4.8 +/- 1.7). The theoretical depletion rate is thus in good agreement with the experimental value, but the quenching and total rates are overestimated, because the present RT couplings are too large. This discrepancy is probably due to our simple and empirical RT matrix element.

Patterning of alloy precipitation through external pressure

NASA Astrophysics Data System (ADS)

Franklin, Jack A.

Due to the nature of their microstructure, alloyed components have the benefit of meeting specific design goals across a wide range of electrical, thermal, and mechanical properties. In general by selecting the correct alloy system and applying a proper heat treatment it is possible to create a metallic sample whose properties achieve a unique set of design requirements. This dissertation presents an innovative processing technique intended to control both the location of formation and the growth rates of precipitates within metallic alloys in order to create multiple patterned areas of unique microstructure within a single sample. Specific experimental results for the Al-Cu alloy system will be shown. The control over precipitation is achieved by altering the conventional heat treatment process with an external surface load applied to selected locations during the quench and anneal. It is shown that the applied pressures affect both the rate and directionality of the atomic diffusion in regions close to the loaded surfaces. The control over growth rates is achieved by altering the enthalpic energy required for successful diffusion between lattice sites. Changes in the local chemical free energy required to direct the diffusion of atoms are established by introducing a non-uniform elastic strain energy field within the samples created by the patterned surface pressures. Either diffusion rates or atomic mobility can be selected as the dominating control process by varying the quench rate; with slower quenches having greater control over the mobility of the alloying elements. Results have shown control of Al2Cu precipitation over 100 microns on mechanically polished surfaces. Further experimental considerations presented will address consistency across sample ensembles. This includes repeatable pressure loading conditions and the chemical interaction between any furnace environments and both the alloy sample and metallic pressure loading devices.

Analysis of ITER NbTi and Nb3Sn CICCs experimental minimum quench energy with JackPot, MCM and THEA models

NASA Astrophysics Data System (ADS)

Bagni, T.; Duchateau, J. L.; Breschi, M.; Devred, A.; Nijhuis, A.

2017-09-01

Cable-in-conduit conductors (CICCs) for ITER magnets are subjected to fast changing magnetic fields during the plasma-operating scenario. In order to anticipate the limitations of conductors under the foreseen operating conditions, it is essential to have a better understanding of the stability margin of magnets. In the last decade ITER has launched a campaign for characterization of several types of NbTi and Nb3Sn CICCs comprising quench tests with a singular sine wave fast magnetic field pulse and relatively small amplitude. The stability tests, performed in the SULTAN facility, were reproduced and analyzed using two codes: JackPot-AC/DC, an electromagnetic-thermal numerical model for CICCs, developed at the University of Twente (van Lanen and Nijhuis 2010 Cryogenics 50 139-148) and multi-constant-model (MCM) (Turck and Zani 2010 Cryogenics 50 443-9), an analytical model for CICCs coupling losses. The outputs of both codes were combined with thermal, hydraulic and electric analysis of superconducting cables to predict the minimum quench energy (MQE) (Bottura et al 2000 Cryogenics 40 617-26). The experimental AC loss results were used to calibrate the JackPot and MCM models and to reproduce the energy deposited in the cable during an MQE test. The agreement between experiments and models confirm a good comprehension of the various CICCs thermal and electromagnetic phenomena. The differences between the analytical MCM and numerical JackPot approaches are discussed. The results provide a good basis for further investigation of CICC stability under plasma scenario conditions using magnetic field pulses with lower ramp rate and higher amplitude.

Magnetism out of antisite disorder in the J =0 compound Ba2YIrO6

NASA Astrophysics Data System (ADS)

Chen, Q.; Svoboda, C.; Zheng, Q.; Sales, B. C.; Mandrus, D. G.; Zhou, H. D.; Zhou, J.-S.; McComb, D.; Randeria, M.; Trivedi, N.; Yan, J.-Q.

2017-10-01

We systematically investigate the magnetic properties and local structure of Ba2YIrO6 to demonstrate that Y and Ir lattice defects in the form of antiphase boundary or clusters of antisite disorder affect the magnetism observed in this 5 d4 compound. The experimental investigation involved comparison of the magnetic properties and atomic imaging of (1) a slow-cooled crystal, (2) a crystal quenched from 900°C after growth, and (3) a crystal grown using a faster cooling rate during growth than the slow-cooled one. Atomic-scale imaging by scanning transmission electron microscopy (STEM) shows that quenching from 900°C introduces Ir-rich antiphase boundaries in the crystals, and a faster cooling rate during crystal growth leads to clusters of Y and Ir antisite disorder. Compared to the slow-cooled crystals, Ba2YIrO6 crystals with clusters of antisite defects have a larger effective moment and a larger saturation moment, while quenched crystals with Ir-rich antiphase boundary show a slightly suppressed moment. Our DFT and model magnetic Hamiltonian calculations suggest magnetic condensation is unlikely, as the energy to be gained from superexchange is small compared to the spin-orbit gap. However, once Y is replaced by Ir in the antisite disordered region, the picture of local nonmagnetic singlets breaks down and magnetism can be induced. This is because of (a) enhanced interactions due to increased orbital overlap and (b) increased number of orbitals mediating the interactions. Our work highlights the importance of lattice defects in understanding the experimentally observed magnetism in Ba2YIrO6 and other J =0 systems.

Magnetism out of antisite disorder in the J = 0 compound Ba 2 YIrO 6

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

Chen, Qiang; Svoboda, Chris; Zheng, Qiang

Here, we systematically investigate the magnetic properties and local structure of Ba 2YIrO 6 to demonstrate that Y and Ir lattice defects in the form of antiphase boundary or clusters of antisite disorder affect the magnetism observed in this 5d 4 compound. The experimental investigation involved comparison of the magnetic properties and atomic imaging of (1) a slow-cooled crystal, (2) a crystal quenched from 900°C after growth, and (3) a crystal grown using a faster cooling rate during growth than the slow-cooled one. Atomic-scale imaging by scanning transmission electron microscopy (STEM) shows that quenching from 900°C introduces Ir-rich antiphase boundariesmore » in the crystals, and a faster cooling rate during crystal growth leads to clusters of Y and Ir antisite disorder. Compared to the slow-cooled crystals, Ba 2YIrO 6 crystals with clusters of antisite defects have a larger effective moment and a larger saturation moment, while quenched crystals with Ir-rich antiphase boundary show a slightly suppressed moment. Our DFT and model magnetic Hamiltonian calculations suggest magnetic condensation is unlikely, as the energy to be gained from superexchange is small compared to the spin-orbit gap. However, once Y is replaced by Ir in the antisite disordered region, the picture of local nonmagnetic singlets breaks down and magnetism can be induced. This is because of (a) enhanced interactions due to increased orbital overlap and (b) increased number of orbitals mediating the interactions. Our work highlights the importance of lattice defects in understanding the experimentally observed magnetism in Ba 2YIrO 6 and other J = 0 systems.« less

Magnetism out of antisite disorder in the J = 0 compound Ba 2 YIrO 6

DOE PAGES

Chen, Qiang; Svoboda, Chris; Zheng, Qiang; ...

2017-10-18

Here, we systematically investigate the magnetic properties and local structure of Ba 2YIrO 6 to demonstrate that Y and Ir lattice defects in the form of antiphase boundary or clusters of antisite disorder affect the magnetism observed in this 5d 4 compound. The experimental investigation involved comparison of the magnetic properties and atomic imaging of (1) a slow-cooled crystal, (2) a crystal quenched from 900°C after growth, and (3) a crystal grown using a faster cooling rate during growth than the slow-cooled one. Atomic-scale imaging by scanning transmission electron microscopy (STEM) shows that quenching from 900°C introduces Ir-rich antiphase boundariesmore » in the crystals, and a faster cooling rate during crystal growth leads to clusters of Y and Ir antisite disorder. Compared to the slow-cooled crystals, Ba 2YIrO 6 crystals with clusters of antisite defects have a larger effective moment and a larger saturation moment, while quenched crystals with Ir-rich antiphase boundary show a slightly suppressed moment. Our DFT and model magnetic Hamiltonian calculations suggest magnetic condensation is unlikely, as the energy to be gained from superexchange is small compared to the spin-orbit gap. However, once Y is replaced by Ir in the antisite disordered region, the picture of local nonmagnetic singlets breaks down and magnetism can be induced. This is because of (a) enhanced interactions due to increased orbital overlap and (b) increased number of orbitals mediating the interactions. Our work highlights the importance of lattice defects in understanding the experimentally observed magnetism in Ba 2YIrO 6 and other J = 0 systems.« less

Active quench and reset integrated circuit with novel hold-off time control logic for Geiger-mode avalanche photodiodes.

PubMed

Deng, Shijie; Morrison, Alan P

2012-09-15

This Letter presents an active quench-and-reset circuit for Geiger-mode avalanche photodiodes (GM-APDs). The integrated circuit was fabricated using a conventional 0.35 μm complementary metal oxide semiconductor process. Experimental results show that the circuit is capable of linearly setting the hold-off time from several nanoseconds to microseconds with a resolution of 6.5 ns. This allows the selection of the optimal afterpulse-free hold-off time for the GM-APD via external digital inputs or additional signal processing circuitry. Moreover, this circuit resets the APD automatically following the end of the hold-off period, thus simplifying the control for the end user. Results also show that a minimum dead time of 28.4 ns is achieved, demonstrating a saturated photon-counting rate of 35.2 Mcounts/s.

Effect of thermal processing practices on the properties of superplastic Al-Li alloys

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Lippard, Henry E.

1993-01-01

The effect of thermal processing on the mechanical properties of superplastically formed structural components fabricated from three aluminum-lithium alloys was evaluated. The starting materials consisted of 8090, 2090, and X2095 (Weldalite(TM) 049), in the form of commercial-grade superplastic sheet. The experimental test matrix was designed to assess the impact on mechanical properties of eliminating solution heat treatment and/or cold water quenching from post-forming thermal processing. The extensive hardness and tensile property data compiled are presented as a function of aging temperature, superplastic strain and temper/quench rate for each alloy. The tensile properties of the materials following superplastic forming in two T5-type tempers are compared with the baseline T6 temper. The implications for simplifying thermal processing without degradation in properties are discussed on the basis of the results.

Ultrasound-assisted interaction between chlorin-e6 and human serum albumin: pH dependence, singlet oxygen production, and formulation effect

NASA Astrophysics Data System (ADS)

Mocanu, Mihaela N.; Yan, Fei

2018-02-01

The interaction between chlorin e6 (Ce6) and human serum albumin (HSA) in the presence and absence of ultrasound have been investigated by ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy. Ce6 is found to bind strongly to HSA at or near physiological pH conditions, but the strength of the binding is significantly weakened at lower pHs. The intrinsic fluorescence of HSA is incrementally quenched with increasing concentration of Ce6, and the quenching is enhanced after exposure to high-frequency ultrasound. Our experimental results suggest that Ce6-induced sonodynamic oxidation of HSA is mainly mediated by singlet oxygen. The formulation of Ce6 by high molecular weight polyvinylpyrrolidone (PVP) increased its stability in aqueous solutions and its quantum yield of singlet oxygen under ultrasound irradiation.

A rapid and sensitive assay for determination of doxycycline using thioglycolic acid-capped cadmium telluride quantum dots.

PubMed

Tashkhourian, Javad; Absalan, Ghodratollah; Jafari, Marzieh; Zare, Saber

2016-01-05

A rapid, simple and inexpensive spectrofluorimetric sensor for determination of doxycycline based on its interaction with thioglycolic acid-capped cadmium telluride quantum dots (TGA/CdTe QDs) has been developed. Under the optimum experimental conditions, the sensor exhibited a fast response time of <10s. The results revealed that doxycycline could quench the fluorescence of TGA/CdTe QDs via electron transfer from the QDs to doxycycline through a dynamic quenching mechanism. The sensor permitted determination of doxycycline in a concentration range of 1.9×10(-6)-6.1×10(-5)molL(-1) with a detection limit of 1.1×10(-7)molL(-1). The sensor was applied for determination of doxycycline in honey and human serum samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Application of phosphorescence quenching by O2 to the investigation of O2 delivery to ocular tissues

NASA Astrophysics Data System (ADS)

Chamot, Stephane R.; Petrig, Benno L.; Pournaras, Constantin J.; Percicot, Christine L.; Lambrou, George N.; Riva, Charles E.

2001-10-01

The technique of phosphorescence quenching by O2 (PQ) allows the non-invasive measurement of the partial pressure of oxygen in blood (pO2blood). This technique and its application to the investigation of the pO2blood in the microvasculature of the retina and optic nerve head (ONH) of two animal species is described. Using the imaging mode of PQ, 2-dimensional pO2blood maps were obtained to investigate the response of the pO2blood to various physiological stimuli in miniature pigs and the effect of experimental glaucoma in monkeys. Applied in its focal mode, PQ allows measurements of the pO2blood with a time resolution of 1 second and is adequate to investigate the pO2blood time course during light stimulation.

Study of factors influencing the effective delivery of O2(1delta) into the resonator of the oxygen-iodine laser

NASA Astrophysics Data System (ADS)

Krukowski, I. M.; Halin, A. L.

1994-08-01

Experimental studies have been performed on the processes: chlorine utilization in the bubbler type singlet oxygen generator, the quenching of O2(1(Delta) ) in the OIL path, the propagation of the gas mixture O2 + O2 (1(Delta) ) + H2O throughout forward flow-type water vapor trap.

Experimental and theoretical photoluminescence studies in nucleic acid assembled gold-upconverting nanoparticle clusters.

PubMed

He, Liangcan; Mao, Chenchen; Cho, Suehyun; Ma, Ke; Xi, Weixian; Bowman, Christopher N; Park, Wounjhang; Cha, Jennifer N

2015-11-07

Combinations of rare earth doped upconverting nanoparticles (UCNPs) and gold nanostructures are sought as nanoscale theranostics due to their ability to convert near infrared (NIR) photons into visible light and heat, respectively. However, because the large NIR absorption cross-section of the gold coupled with their thermo-optical properties can significantly hamper the photoluminescence of UCNPs, methods to optimize the ratio of gold nanostructures to UCNPs must be developed and studied. We demonstrate here nucleic acid assembly methods to conjugate spherical gold nanoparticles (AuNPs) and gold nanostars (AuNSs) to silica-coated UCNPs and probe the effect on photoluminescence. These studies showed that while UCNP fluorescence enhancement was observed from the AuNPs conjugated UCNPs, AuNSs tended to quench fluorescence. However, conjugating lower ratios of AuNSs to UCNPs led to reduced quenching. Simulation studies both confirmed the experimental results and demonstrated that the orientation and distance of the UCNP with respect to the core and arms of the gold nanostructures played a significant role in PL. In addition, the AuNS-UCNP assemblies were able to cause rapid gains in temperature of the surrounding medium enabling their potential use as a photoimaging-photodynamic-photothermal agent.

EXPERIMENTAL EVALUATION OF DOSIMETRIC CHARACTERIZATION OF GAFCHROMIC EBT3 AND EBT-XD FILMS FOR CLINICAL CARBON ION BEAMS.

PubMed

Yonai, Shunsuke; Arai, Chinatsu; Shimoyama, Kaoru; Fournier-Bidoz, Nathalie

2018-02-03

Radiochromic film is a very useful tool for 2D dosimetric measurements in radiotherapy because it is self-developing and has very high-spatial resolution. However, considerable care has to be taken in ion beam radiotherapy owing to the quenching effect of high-linear energy transfer (LET) radiation. In this study, the dose responses of GAFchromic EBT3 and EBT-XD films were experimentally investigated using the clinical carbon ion beam at the Heavy Ion Medical Accelerator in Chiba. Results showed that the relations between absorbed dose and net optical density could be expressed well using an equation proposed by Reinhardt (2015). The quenching effect was evaluated by determining their relative efficiencies for photon irradiation as a function of LET. A correction equation derived in this study allowed the absorbed dose to be determined in the small irradiation field used for carbon ion radiotherapy eye treatments. This study contributes to establishing an absolute dosimetry procedure for heavy ion beams using radiochromic film. © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Far-from-Equilibrium Route to Superthermal Light in Bimodal Nanolasers

NASA Astrophysics Data System (ADS)

Marconi, Mathias; Javaloyes, Julien; Hamel, Philippe; Raineri, Fabrice; Levenson, Ariel; Yacomotti, Alejandro M.

2018-02-01

Microscale and nanoscale lasers inherently exhibit rich photon statistics due to complex light-matter interaction in a strong spontaneous emission noise background. It is well known that they may display superthermal fluctuations—photon superbunching—in specific situations due to either gain competition, leading to mode-switching instabilities, or carrier-carrier coupling in superradiant microcavities. Here we show a generic route to superbunching in bimodal nanolasers by preparing the system far from equilibrium through a parameter quench. We demonstrate, both theoretically and experimentally, that transient dynamics after a short-pump-pulse-induced quench leads to heavy-tailed superthermal statistics when projected onto the weak mode. We implement a simple experimental technique to access the probability density functions that further enables quantifying the distance from thermal equilibrium via the thermodynamic entropy. The universality of this mechanism relies on the far-from-equilibrium dynamical scenario, which can be mapped to a fast cooling process of a suspension of Brownian particles in a liquid. Our results open up new avenues to mold photon statistics in multimode optical systems and may constitute a test bed to investigate out-of-equilibrium thermodynamics using micro or nanocavity arrays.

Study on the interaction of antiviral drug 'Tenofovir' with human serum albumin by spectral and molecular modeling methods

NASA Astrophysics Data System (ADS)

Shahabadi, Nahid; Hadidi, Saba; Feizi, Foroozan

2015-03-01

This study was designed to examine the interaction of Tenofovir (Ten) with human serum albumin (HSA) under physiological conditions. The binding of drugs with human serum albumin is a crucial factor influencing the distribution and bioactivity of drugs in the body. To understand the action mechanisms between Ten and HSA, the binding of Ten with HSA was investigated by a combined experimental and computational approach. UV-vis results confirmed that Ten interacted with HSA to form a ground-state complex and values of the Stern-Volmer quenching constant indicate the presence of a static component in the quenching mechanism. As indicated by the thermodynamic parameters (positive ΔH and ΔS values), hydrophobic interaction plays a major role in the Ten-HSA complex. Through the site marker competitive experiment, Ten was confirmed to be located in site I of HSA. Furthermore, UV-vis absorption spectra, synchronous fluorescence spectrum and CD data were used to investigate the structural change of HSA molecules with addition of Ten, the results indicate that the secondary structure of HSA molecules was changed in the presence of Ten. The experimental results were in agreement with the results obtained via molecular docking study.

Full-dimensional quantum dynamics of rovibrationally inelastic scattering between CN and H2

NASA Astrophysics Data System (ADS)

Yang, Benhui; Wang, X. H.; Stancil, P. C.; Bowman, J. M.; Balakrishnan, N.; Forrey, R. C.

2016-12-01

We report six-dimensional (6D) potential energy surface (PES) and rovibrational scattering calculations for the CN-H2 collision system. The PES was computed using the high-level ab initio spin-restricted coupled-cluster with single, double, and perturbative triple excitations-F12B method and fitted to an analytic function using an invariant polynomial method in 6D. Quantum close-coupling calculations are reported for rotational transitions in CN by H2 and D2 collisions in 6D as well as four-dimensional (4D) within a rigid rotor model for collision energies of 1.0-1500 cm-1. Comparisons with experimental data and previous 4D calculations are presented for CN rotational levels j1 = 4 and 11. For the first time, rovibrational quenching cross sections and rate coefficients of CN (v1 = 1,j1 = 0) in collisions with para- and ortho-H2 are also reported in full-dimension. Agreement for pure rotational transitions is found to be good, but no experimental data on rovibrational collisional quenching for CN-H2 are available. Applications of the current rotational and rovibrational rate coefficients in astrophysical modeling are briefly discussed.

Catalyzed Combustion of Bipropellants for Micro-Spacecraft Propulsion

NASA Technical Reports Server (NTRS)

Schneider, Steven J.; Sung, Chih-Jen; Boyarko, George A.

2003-01-01

This paper addresses the need to understand the physics and chemistry involved in propellant combustion processes in micro-scale combustors for propulsion systems on micro-spacecraft. These spacecraft are planned to have a mass less than 50 kilograms with attitude control estimated to be in the 10 milli-Newton thrust class. These combustors are anticipated to be manufactured using Micro Electrical Mechanical Systems (MEMS) technology and are expected to have diameters approaching the quenching diameter of the propellants. Combustors of this size are expected to benefit significantly from surface catalysis processes. Miniature flame tube apparatus is chosen for this study because microtubes can be easily fabricated from known catalyst materials and their simplicity in geometry can be used in fundamental simulations for validation purposes. Experimentally, we investigated the role of catalytically active surfaces within 0.4 and 0.8 mm internal diameter microtubes, with special emphases on ignition processes in fuel rich gaseous hydrogen and gaseous oxygen. Flame thickness and reaction zone thickness calculations predict that the diameters of our test apparatus are below the quenching diameter of the propellants in sub-atmospheric tests. Temperature and pressure rise in resistively heated platinum and palladium microtubes was used as an indication of exothermic reactions. Specific data on mass flow versus preheat temperature required to achieve ignition are presented. With a plug flow model, the experimental conditions were simulated with detailed gas-phase chemistry, thermodynamic properties, and surface kinetics. Computational results generally support the experimental findings, but suggest an experimental mapping of the exit temperature and composition is needed.

Determination of the quenching correction factors for plastic scintillation detectors in therapeutic high-energy proton beams

PubMed Central

Wang, L L W; Perles, L A; Archambault, L; Sahoo, N; Mirkovic, D; Beddar, S

2013-01-01

The plastic scintillation detectors (PSD) have many advantages over other detectors in small field dosimetry due to its high spatial resolution, excellent water equivalence and instantaneous readout. However, in proton beams, the PSDs will undergo a quenching effect which makes the signal level reduced significantly when the detector is close to Bragg peak where the linear energy transfer (LET) for protons is very high. This study measures the quenching correction factor (QCF) for a PSD in clinical passive-scattering proton beams and investigates the feasibility of using PSDs in depth-dose measurements in proton beams. A polystyrene based PSD (BCF-12, ϕ0.5mm×4mm) was used to measure the depth-dose curves in a water phantom for monoenergetic unmodulated proton beams of nominal energies 100, 180 and 250 MeV. A Markus plane-parallel ion chamber was also used to get the dose distributions for the same proton beams. From these results, the QCF as a function of depth was derived for these proton beams. Next, the LET depth distributions for these proton beams were calculated by using the MCNPX Monte Carlo code, based on the experimentally validated nozzle models for these passive-scattering proton beams. Then the relationship between the QCF and the proton LET could be derived as an empirical formula. Finally, the obtained empirical formula was applied to the PSD measurements to get the corrected depth-dose curves and they were compared to the ion chamber measurements. A linear relationship between QCF and LET, i.e. Birks' formula, was obtained for the proton beams studied. The result is in agreement with the literature. The PSD measurements after the quenching corrections agree with ion chamber measurements within 5%. PSDs are good dosimeters for proton beam measurement if the quenching effect is corrected appropriately. PMID:23128412

Determination of the quenching correction factors for plastic scintillation detectors in therapeutic high-energy proton beams

NASA Astrophysics Data System (ADS)

Wang, L. L. W.; Perles, L. A.; Archambault, L.; Sahoo, N.; Mirkovic, D.; Beddar, S.

2012-12-01

Plastic scintillation detectors (PSDs) have many advantages over other detectors in small field dosimetry due to their high spatial resolution, excellent water equivalence and instantaneous readout. However, in proton beams, the PSDs undergo a quenching effect which makes the signal level reduced significantly when the detector is close to the Bragg peak where the linear energy transfer (LET) for protons is very high. This study measures the quenching correction factor (QCF) for a PSD in clinical passive-scattering proton beams and investigates the feasibility of using PSDs in depth-dose measurements in proton beams. A polystyrene-based PSD (BCF-12, ϕ0.5 mm × 4 mm) was used to measure the depth-dose curves in a water phantom for monoenergetic unmodulated proton beams of nominal energies 100, 180 and 250 MeV. A Markus plane-parallel ion chamber was also used to get the dose distributions for the same proton beams. From these results, the QCF as a function of depth was derived for these proton beams. Next, the LET depth distributions for these proton beams were calculated by using the MCNPX Monte Carlo code, based on the experimentally validated nozzle models for these passive-scattering proton beams. Then the relationship between the QCF and the proton LET could be derived as an empirical formula. Finally, the obtained empirical formula was applied to the PSD measurements to get the corrected depth-dose curves and they were compared to the ion chamber measurements. A linear relationship between the QCF and LET, i.e. Birks' formula, was obtained for the proton beams studied. The result is in agreement with the literature. The PSD measurements after the quenching corrections agree with ion chamber measurements within 5%. PSDs are good dosimeters for proton beam measurement if the quenching effect is corrected appropriately.

Partitioning of Mg, Ca, and Na between carbonatite melt and hydrous fluid at 0.1-0.2 GPa

NASA Astrophysics Data System (ADS)

Veksler, Ilya V.; Keppler, Hans

Experimental studies of the element distribution between carbonatite melts and hydrous fluids are hampered by the fact that neither the fluid nor the melt can be isochemically quenched in conventional high-pressure vessels. In order to overcome this problem, we used a double-capsule technique to separate immiscible fluid and melt phases during and after the runs. The inner platinum capsules were charged with carbonate mixtures (CaCO3, MgCO3 and Na2CO3) and placed inside the outer capsules charged with distilled water and diamond powder. The latter was used as an inert trap for solids precipitating from the fluid on quenching. Carbonate melt and hydrous fluid equilibrated through a small hole left in the upper end of the inner capsule. The runs were performed in rapid-quench cold-seal pressure vessels at 0.1-0.2 GPa and 700-900°C in the two-phase (fluid+melt) stability region. Both quenched melt and quenched fluid were dissolved in dilute HCl and analysed by inductively coupled plasma atomic emission spectroscopy. The results show that under all conditions investigated, fluid/melt partition coefficients for Ca and Mg are similar and several times smaller than those for Na. At 0.1 GPa and a water/carbonatite ratio of 1 (by weight), the partition coefficients are DNa= 0.35+/- 0.02, DCa=0.09+/-0.02, and DMg=0.13+/- 0.01. Between 700 and 900°C, the effect of temperature on partitioning is negligible. However, DNa increases significantly with decreasing water/carbonatite ratio in the system. Our data show that the release of a hydrous fluid enriched in sodium and simultaneous crystallisation of calcite can transform an alkaline, vapour-saturated carbonatite melt into a body of pure calcite surrounded by zones of sodium metasomatism. Thus, it is quite possible that carbonate magmas with substantial amounts of alkalies were common parental liquids of plutonic carbonatites.

Modification of Grange-Kiefer Approach for Determination of Hardenability in Eutectoid Steel

NASA Astrophysics Data System (ADS)

Sushanthi, Neethi; Maity, Joydeep

2014-12-01

In this research work, an independent mathematical modeling approach has been adopted for determination of the hardenability of steels. In this model, at first, cooling curves were generated by solving transient heat transfer equation through discretization with pure explicit finite difference scheme coupled with MATLAB-based programming considering variable thermo-physical properties of 1080 steel. Thereafter, a new fundamental approach is proposed for obtaining CCT noses as a function of volume fraction transformed through modification of Grange-Kiefer approach. The cooling curves were solved against 50 pct transformation nose of CCT diagram in order to predict hardening behavior of 1080 steel in terms of hardenability parameters (Grossmann critical diameter, D C; and ideal critical diameter, D I) and the variation of the unhardened core diameter ( D u) to diameter of steel bar ( D) ratio with diameter of the steel bar ( D). The experiments were also performed to ascertain actual D C value of 1080 steel for still water quenching. The D C value obtained by the developed model was found to match the experimental D C value with only 3 pct deviation. Therefore, the model developed in the present work can be used for direct determination of D I, D C and D u without resorting to any rigorous experimentation.

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.

Simultaneous one-dimensional fluorescence lifetime measurements of OH and CO in premixed flames

NASA Astrophysics Data System (ADS)

Jonsson, Malin; Ehn, Andreas; Christensen, Moah; Aldén, Marcus; Bood, Joakim

2014-04-01

A method for simultaneous measurements of fluorescence lifetimes of two species along a line is described. The experimental setup is based on picosecond laser pulses from two tunable optical parametric generator/optical parametric amplifier systems together with a streak camera. With an appropriate optical time delay between the two laser pulses, whose wavelengths are tuned to excite two different species, laser-induced fluorescence can be both detected temporally and spatially resolved by the streak camera. Hence, our method enables one-dimensional imaging of fluorescence lifetimes of two species in the same streak camera recording. The concept is demonstrated for fluorescence lifetime measurements of CO and OH in a laminar methane/air flame on a Bunsen-type burner. Measurements were taken in flames with four different equivalence ratios, namely ϕ = 0.9, 1.0, 1.15, and 1.25. The measured one-dimensional lifetime profiles generally agree well with lifetimes calculated from quenching cross sections found in the literature and quencher concentrations predicted by the GRI 3.0 mechanism. For OH, there is a systematic deviation of approximately 30 % between calculated and measured lifetimes. It is found that this is mainly due to the adiabatic assumption regarding the flame and uncertainty in H2O quenching cross section. This emphasizes the strength of measuring the quenching rates rather than relying on models. The measurement concept might be useful for single-shot measurements of fluorescence lifetimes of several species pairs of vital importance in combustion processes, hence allowing fluorescence signals to be corrected for quenching and ultimately yield quantitative concentration profiles.

Experimental investigation of 150-KG-scale corium melt jet quenching in water

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

Magallon, D.; Hohmann, H.

This paper compares and discusses the results of two large scale FARO quenching tests known as L-11 and L-14, which involved, respectively, 151 kg of W% 76.7 UO{sub 2} + 19.2 ZrO{sub 2} + 4.1 Zr and 125 kg of W% 80 UO{sub 2} + 20 ZrO{sub 2} melts poured into 600-kg, 2-m-depth water at saturation at 5.0 MPa. The results are further compared with those of two previous tests performed using a pure oxidic melt, respectively 18 and 44 kg of W% 80 UO{sub 2} + 20 ZrO{sub 2} melt quenched in 1-m-depth water at saturation at 5.0 MPa.more » In all the tests, significant breakup and quenching took place during the melt fall through the water. No steam explosion occurred. In the tests performed with a pure oxide UO{sub 2}-ZrO{sub 2} melt, part of the corium (from 1/6 to 1/3) did not breakup and reached the bottom plate still molten whatever the water depth was. Test L-11 data suggest that full oxidation and complete breakup of the melt occurred during the melt fall through the water. A proportion of 64% of the total energy content of the melt was released to the water during this phase ({approximately}1.5 s), against 44% for L-14. The maximum temperature increase of the bottom plate was 330 K (L-14). The mean particle size of the debris ranged between 2.5 and 4.8mm.« less

Temperature Programmed Desorption of Quench-condensed Krypton and Acetone in Air; Selective Concentration of Ultra-trace Gas Components.

PubMed

Suzuki, Taku T; Sakaguchi, Isao

2016-01-01

Selective concentration of ultra-trace components in air-like gases has an important application in analyzing volatile organic compounds in the gas. In the present study, we examined quench-condensation of the sample gas on a ZnO substrate below 50 K followed by temperature programmed desorption (TPD) (low temperature TPD) as a selective gas concentration technique. We studied two specific gases in the normal air; krypton as an inert gas and acetone as a reactive gas. We evaluated the relationship between the operating condition of low temperature TPD and the lowest detection limit. In the case of krypton, we observed the selective concentration by exposing at 6 K followed by thermal desorption at about 60 K. On the other hand, no selectivity appeared for acetone although trace acetone was successfully concentrated. This is likely due to the solvent effect by a major component in the air, which is suggested to be water. We suggest that pre-condensation to remove the water component may improve the selectivity in the trace acetone analysis by low temperature TPD.

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

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

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.

Titanium Dioxide Nanoparticles (TiO₂) Quenching Based Aptasensing Platform: Application to Ochratoxin A Detection.

PubMed

Sharma, Atul; Hayat, Akhtar; Mishra, Rupesh K; Catanante, Gaëlle; Bhand, Sunil; Marty, Jean Louis

2015-09-22

We demonstrate for the first time, the development of titanium dioxide nanoparticles (TiO₂) quenching based aptasensing platform for detection of target molecules. TiO₂ quench the fluorescence of FAM-labeled aptamer (fluorescein labeled aptamer) upon the non-covalent adsorption of fluorescent labeled aptamer on TiO₂ surface. When OTA interacts with the aptamer, it induced aptamer G-quadruplex complex formation, weakens the interaction between FAM-labeled aptamer and TiO₂, resulting in fluorescence recovery. As a proof of concept, an assay was employed for detection of Ochratoxin A (OTA). At optimized experimental condition, the obtained limit of detection (LOD) was 1.5 nM with a good linearity in the range 1.5 nM to 1.0 µM for OTA. The obtained results showed the high selectivity of assay towards OTA without interference to structurally similar analogue Ochratoxin B (OTB). The developed aptamer assay was evaluated for detection of OTA in beer sample and recoveries were recorded in the range from 94.30%-99.20%. Analytical figures of the merits of the developed aptasensing platform confirmed its applicability to real samples analysis. However, this is a generic aptasensing platform and can be extended for detection of other toxins or target analyte.

Porous materials produced from incineration ash using thermal plasma technology.

PubMed

Yang, Sheng-Fu; Chiu, Wen-Tung; Wang, To-Mai; Chen, Ching-Ting; Tzeng, Chin-Ching

2014-06-01

This study presents a novel thermal plasma melting technique for neutralizing and recycling municipal solid waste incinerator (MSWI) ash residues. MSWI ash residues were converted into water-quenched vitrified slag using plasma vitrification, which is environmentally benign. Slag is adopted as a raw material in producing porous materials for architectural and decorative applications, eliminating the problem of its disposal. Porous materials are produced using water-quenched vitrified slag with Portland cement and foaming agent. The true density, bulk density, porosity and water absorption ratio of the foamed specimens are studied here by varying the size of the slag particles, the water-to-solid ratio, and the ratio of the weights of the core materials, including the water-quenched vitrified slag and cement. The thermal conductivity and flexural strength of porous panels are also determined. The experimental results show the bulk density and the porosity of the porous materials are 0.9-1.2 g cm(-3) and 50-60%, respectively, and the pore structure has a closed form. The thermal conductivity of the porous material is 0.1946 W m(-1) K(-1). Therefore, the slag composite materials are lightweight and thermal insulators having considerable potential for building applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

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.

A novel fluorescence biosensor for sensitivity detection of tyrosinase and acid phosphatase based on nitrogen-doped graphene quantum dots.

PubMed

Qu, Zhengyi; Na, Weidan; Liu, Xiaotong; Liu, Hua; Su, Xingguang

2018-01-02

In this paper, we developed a sensitive fluorescence biosensor for tyrosinase (TYR) and acid phosphatase (ACP) activity detection based on nitrogen-doped graphene quantum dots (N-GQDs). Tyrosine could be catalyzed by TYR to generate dopaquinone, which could efficiently quench the fluorescence of N-GQDs, and the degree of fluorescence quenching of N-GQDs was proportional to the concentration of TYR. In the presence of ACP, l-Ascorbic acid-2-phosphate (AAP) was hydrolyzed to generate ascorbic acid (AA), and dopaquinone was reduced to l-dopa, resulting in the fluorescence recovery of the quenched fluorescence by dopaquinone. Thus, a novel fluorescence biosensor for the detection of TYR and ACP activity based on N-GQDs was constructed. Under the optimized experimental conditions, the fluorescence intensity was linearly correlated with the concentration of TYR and ACP in the range of 0.43-3.85 U mL -1 and 0.04-0.7 mU mL -1 with a detection limit of 0.15 U mL -1 and 0.014 mU mL -1 , respectively. The feasibility of the proposed biosensor in real samples assay was also studied and satisfactory results were obtained. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Supersensitive and selective detection of picric acid explosive by fluorescent Ag nanoclusters.

PubMed

Zhang, Jian Rong; Yue, Yuan Yuan; Luo, Hong Qun; Li, Nian Bing

2016-02-07

Picric acid (PA) explosive is a hazard to public safety and health, so the sensitive and selective detection of PA is very important. In the present work, polyethyleneimine stabilized Ag nanoclusters were successfully used for the sensitive and selective quantification of PA on the basis of fluorescence quenching. The quenching efficiency of Ag nanoclusters is proportional to the concentration of PA and the logarithm of PA concentration over two different concentration ranges (1.0 nM-1 μM for the former and 0.25-20 μM for the latter), thus the proposed quantitative strategy for PA provides a wide linear range of 1.0 nM-20 μM. The detection limit based on 3σ/K is 0.1 nM. The quenching mechanism of Ag nanoclusters by PA is discussed in detail. The results indicate that the selective detection of PA over other nitroaromatics including 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), p-nitrotoluene (p-NT), m-dinitrobenzene (m-DNB), and nitrobenzene (NB), is due to the electron transfer and energy transfer between PA and polyethyleneimine-capped Ag nanoclusters. In addition, the experimental data obtained for the analysis of artificial samples show that the proposed PA sensor is potentially applicable in the determination of trace PA explosive in real samples.

Dynamical vanishing of the order parameter in a confined Bardeen-Cooper-Schrieffer Fermi gas after an interaction quench

NASA Astrophysics Data System (ADS)

Hannibal, S.; Kettmann, P.; Croitoru, M. D.; Axt, V. M.; Kuhn, T.

2018-01-01

We present a numerical study of the Higgs mode in an ultracold confined Fermi gas after an interaction quench and find a dynamical vanishing of the superfluid order parameter. Our calculations are done within a microscopic density-matrix approach in the Bogoliubov-de Gennes framework which takes the three-dimensional cigar-shaped confinement explicitly into account. In this framework, we study the amplitude mode of the order parameter after interaction quenches starting on the BCS side of the BEC-BCS crossover close to the transition and ending in the BCS regime. We demonstrate the emergence of a dynamically vanishing superfluid order parameter in the spatiotemporal dynamics in a three-dimensional trap. Further, we show that the signal averaged over the whole trap mirrors the spatiotemporal behavior and allows us to systematically study the effects of the system size and aspect ratio on the observed dynamics. Our analysis enables us to connect the confinement-induced modifications of the dynamics to the pairing properties of the system. Finally, we demonstrate that the signature of the Higgs mode is contained in the dynamical signal of the condensate fraction, which, therefore, might provide a new experimental access to the nonadiabatic regime of the Higgs mode.

Bonded exciplex formation: electronic and stereoelectronic effects.

PubMed

Wang, Yingsheng; Haze, Olesya; Dinnocenzo, Joseph P; Farid, Samir; Farid, Ramy S; Gould, Ian R

2008-12-18

As recently proposed, the singlet-excited states of several cyanoaromatics react with pyridine via bonded-exciplex formation, a novel concept in photochemical charge transfer reactions. Presented here are electronic and steric effects on the quenching rate constants, which provide valuable support for the model. Additionally, excited-state quenching in poly(vinylpyridine) is strongly inhibited both relative to that in neat pyridine and also to conventional exciplex formation in polymers, consistent with a restrictive orientational requirement for the formation of bonded exciplexes. Examples of competing reactions to form both conventional and bonded exciplexes are presented, which illustrate the delicate balance between these two processes when their reaction energetics are similar. Experimental and computational evidence is provided for the formation of a bonded exciplex in the reaction of the singlet excited state of 2,6,9,10-tetracyanoanthracene (TCA) with an oxygen-substituted donor, dioxane, thus expanding the scope of bonded exciplexes.

Dynamical Detection of Topological Phase Transitions in Short-Lived Atomic Systems.

PubMed

Setiawan, F; Sengupta, K; Spielman, I B; Sau, Jay D

2015-11-06

We demonstrate that dynamical probes provide direct means of detecting the topological phase transition (TPT) between conventional and topological phases, which would otherwise be difficult to access because of loss or heating processes. We propose to avoid such heating by rapidly quenching in and out of the short-lived topological phase across the transition that supports gapless excitations. Following the quench, the distribution of excitations in the final conventional phase carries signatures of the TPT. We apply this strategy to study the TPT into a Majorana-carrying topological phase predicted in one-dimensional spin-orbit-coupled Fermi gases with attractive interactions. The resulting spin-resolved momentum distribution, computed by self-consistently solving the time-dependent Bogoliubov-de Gennes equations, exhibits Kibble-Zurek scaling and Stückelberg oscillations characteristic of the TPT. We discuss parameter regimes where the TPT is experimentally accessible.

Dynamical Detection of Topological Phase Transitions in Short-Lived Atomic Systems

NASA Astrophysics Data System (ADS)

Setiawan, F.; Sengupta, K.; Spielman, I. B.; Sau, Jay D.

2015-11-01

We demonstrate that dynamical probes provide direct means of detecting the topological phase transition (TPT) between conventional and topological phases, which would otherwise be difficult to access because of loss or heating processes. We propose to avoid such heating by rapidly quenching in and out of the short-lived topological phase across the transition that supports gapless excitations. Following the quench, the distribution of excitations in the final conventional phase carries signatures of the TPT. We apply this strategy to study the TPT into a Majorana-carrying topological phase predicted in one-dimensional spin-orbit-coupled Fermi gases with attractive interactions. The resulting spin-resolved momentum distribution, computed by self-consistently solving the time-dependent Bogoliubov-de Gennes equations, exhibits Kibble-Zurek scaling and Stückelberg oscillations characteristic of the TPT. We discuss parameter regimes where the TPT is experimentally accessible.

Are Einstein's transition probabilities for spontaneous emission constant in plasmas?

NASA Technical Reports Server (NTRS)

Griem, H. R.; Huang, Y. W.; Wang, J.-S.; Moreno, J. C.

1991-01-01

An investigation is conducted with a ruby laser to experimentally confirm the quenching of spontaneous emission coefficients and propose a mechanism for the phenomenon. Results of previous experiments are examined to determine the consistency and validity of interpretations of the spontaneous emissions. For the C IV 3s-3p and 2s-3p transitions, the line-intensity ratios are found to be dependent on the separation of the laser from the target. Density gradients and Stark broadening are proposed to interpret the results in a way that does not invalidate the Einstein A values. The interpretation is extended to C III and N V, both of which demonstrate similar changes in A values in previous experiments. The apparent quenching of Ar II by photon collisions is explained by Rabi oscillations and power broadening in the argon-ion laser cavity. It is concluded that the changes in A values cannot result from dense plasma effects.

Development of superconducting magnets for RAON 28 GHz ECR ion source.

PubMed

Heo, Jeongil; Choi, Sukjin; Kim, Yonghwan; Hong, In-Seok

2016-02-01

RAON, a 28 GHz electron cyclotron resonance ion source (ECR IS), was designed and tested as a Rare Isotope Science Project. It is expected that RAON would provide not only rare-isotope beams but also stable heavy ions ranging from protons to uranium. In order to obtain the steady heavy-ion beam required for ECR IS, we must use a 28 GHz microwave source as well as a high magnetic field. A superconducting magnet using a NbTi wire was designed and manufactured for producing the ECR IS and a test was conducted. In this paper, the design and fabrication of the superconducting magnet for the ECR IS are presented. Experimental results show that the quench current increases whenever quenching occurs, but it has not yet reached the designed current. The experiment is expected to reveal the ideal conditions required to reach the designed current.

Heavy and light flavor jet quenching at RHIC and LHC energies

NASA Astrophysics Data System (ADS)

Cao, Shanshan; Luo, Tan; Qin, Guang-You; Wang, Xin-Nian

2018-02-01

The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark-gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. The dependence of the jet quenching parameter q ˆ on medium temperature and jet flavor is quantitatively extracted.

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.

Heavy and light flavor jet quenching at RHIC and LHC energies

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

Cao, Shanshan; Luo, Tan; Qin, Guang-You

The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark–gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. Finally, the dependence of the jet quenching parametermore » $$\\hat{q}$$ on medium temperature and jet flavor is quantitatively extracted.« less

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.

Fluorescence quenching and the "ring-mode" to "red-mode" transition in alkali inductively coupled plasmas

NASA Astrophysics Data System (ADS)

Huang, M.; Bazurto, R.; Camparo, J.

2018-01-01

The ring-mode to red-mode transition in alkali metal inductively coupled plasmas (ICPs) (i.e., rf-discharge lamps) is perhaps the most important physical phenomenon affecting these devices as optical pumping light sources for atomic clocks and magnetometers. It sets the limit on useful ICP operating temperature, thereby setting a limit on ICP light output for atomic-clock/magnetometer signal generation, and it is a temperature region of ICP operation associated with discharge instability. Previous work has suggested that the mechanism driving the ring-mode to red-mode transition is associated with radiation trapping, but definitive experimental evidence validating that hypothesis has been lacking. Based on that hypothesis, one would predict that the introduction of an alkali-fluorescence quenching gas (i.e., N2) into the ICP would increase the ring-mode to red-mode transition temperature. Here, we test that prediction, finding direct evidence supporting the radiation-trapping hypothesis.

Singlet oxygen quenching and radical scavenging capacities of structurally-related flavonoids present in Zuccagnia punctata Cav.

PubMed

Vieyra, Faustino E Morán; Boggetti, Héctor J; Zampini, Iris C; Ordoñez, Roxana M; Isla, María I; Alvarez, Rosa M S; De Rosso, Veridiana; Mercadante, Adriana Z; Borsarelli, Claudio D

2009-06-01

The singlet oxygen (1O2) quenching and free radical (DPPH(*), ABTS(* +) and O2(* -)) scavenging ability of three structurally-related flavonoids (7-hydroxyflavanone HF, 2',4'-dihydroxychalcone DHC and 3,7-dihydroxyflavone DHF) present in the Argentinean native shrub Zuccagnia punctata Cav. were studied in solution by combining electrochemical and kinetic measurements, mass spectroscopy, end-point antioxidant assays and computational calculations. The results showed that the antioxidant properties of these flavonoids depend on several factors, such as their electron- and hydrogen atom donor capacity, the ionization degree of the more acidic group, solvatation effects and electrostatic interactions with the oxidant species. The theoretical calculations for both the gas and solution phases at the B3LYP level of theory for the Osanger reaction field model agreed with the experimental findings, thus supporting the characterization of the antioxidant mechanism of the Z. punctata flavonoids.

An experimental study of opposed flow diffusion flame extinction over a thin fuel in microgravity. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Ferkul, Paul V.

1989-01-01

The flame spread and flame extinction characteristics of a thin fuel burning in a low-speed forced convective environment in microgravity were examined. The flame spread rate was observed to decrease both with decreasing ambient oxygen concentration as well as decreasing free stream velocity. A new mode of flame extinction was observed, caused by either of two means: keeping the free stream velocity constant and decreasing the oxygen concentration, or keeping the oxygen concentration constant and decreasing the free stream velocity. This extinction is called quenching extinction. By combining this data together with a previous microgravity quiescent flame study and normal-gravity blowoff extinction data, a flammability map was constructed with molar percentage oxygen and characteristic relative velocity as coordinates. The Damkohler number is not sufficient to predict flame spread and extinction in the near quench limit region.

Spectroscopic studies on the interactions between 3,4-dihydropyrimidin-2(1H)-ones and bovine serum albumin.

PubMed

Yu, Xianyong; Liu, Ronghua; Ji, Danhong; Xie, Jian; Yang, Fengxian; Li, Xiaofang; Huang, Haowen; Yi, Pinggui

2010-09-15

The interactions between 3,4-dihydropyrimidin-2(1H)-ones (DHPM) and bovine serum albumin (BSA) were investigated by fluorescence and ultraviolet spectroscopy under imitated physiological conditions. The experimental results showed that all DHPM could form complexes with BSA. Static quenching and non-radiation energy transfer are the main reasons leading to the fluorescence quenching. The binding constants (K(A)) and the number of binding sites (n) were calculated. According to Förster theory of non-radiation energy transfer, the binding distances (r) between BSA and DHPM are less than 7 nm. The relationship between different aryl groups in pyrimidine ring and the binding ability of DHPM with BSA is preliminarily discussed. Moreover, the synchronous fluorescence spectra indicated that the conformation of BSA has not been changed. Copyright 2010 Elsevier B.V. All rights reserved.

Pre-Steady-State Kinetic Analysis of Single-Nucleotide Incorporation by DNA Polymerases

PubMed Central

Su, Yan; Guengerich, F. Peter

2016-01-01

Pre-steady-state kinetic analysis is a powerful and widely used method to obtain multiple kinetic parameters. This protocol provides a step-by-step procedure for pre-steady-state kinetic analysis of single-nucleotide incorporation by a DNA polymerase. It describes the experimental details of DNA substrate annealing, reaction mixture preparation, handling of the RQF-3 rapid quench-flow instrument, denaturing polyacrylamide DNA gel preparation, electrophoresis, quantitation, and data analysis. The core and unique part of this protocol is the rationale for preparation of the reaction mixture (the ratio of the polymerase to the DNA substrate) and methods for conducting pre-steady-state assays on an RQF-3 rapid quench-flow instrument, as well as data interpretation after analysis. In addition, the methods for the DNA substrate annealing and DNA polyacrylamide gel preparation, electrophoresis, quantitation and analysis are suitable for use in other studies. PMID:27248785

Heavy and light flavor jet quenching at RHIC and LHC energies

DOE PAGES

Cao, Shanshan; Luo, Tan; Qin, Guang-You; ...

2017-12-14

The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark–gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. Finally, the dependence of the jet quenching parametermore » $$\\hat{q}$$ on medium temperature and jet flavor is quantitatively extracted.« less

A computational perspective of vibrational and electronic analysis of potential photosensitizer 2-chlorothioxanthone

NASA Astrophysics Data System (ADS)

Ali, Narmeen; Mansha, Asim; Asim, Sadia; Zahoor, Ameer Fawad; Ghafoor, Sidra; Akbar, Muhammad Usman

2018-03-01

This paper deals with combined theoretical and experimental study of geometric, electronic and vibrational properties of 2-chlorothioxanthone (CTX) molecule which is potential photosensitizer. The FT-IR spectrum of CTX in solid phase was recorded in 4000-400 cm-1 region. The UV-Vis. absorption spectrum was also recorded in the laboratory as well as computed at DFT/B3LYP level in five different phases viz. gas, water, DMSO, acetone and ethanol. The quantum mechanics based theoretical IR and Raman spectra were also calculated for the title compound employing HF and DFT functional with 3-21G+, 6-31G+ and 6-311G+, 6-311G++ basis sets, respectively, and assignment of each vibrational frequency has been done on the basis of potential energy distribution (PED). A comparison has been made between theoretical and experimental vibrational spectra as well as for the UV-Vis. absorption spectra. The computed infra red & Raman spectra by DFT compared with experimental spectra along with reliable vibrational assignment based on PED. The calculated electronic properties, results of natural bonding orbital (NBO) analysis, charge distribution, dipole moment and energies have been reported in the paper. Bimolecular quenching of triplet state of CTX in the presence of triethylamine, 2-propanol triethylamine and diazobicyclooctane (DABCO) reflect the interactions between them. The bimolecular quenching rate constant is fastest for interaction of 3CTX in the presence of DABCO reflecting their stronger interactions.

Computer simulation of phase separation under a double temperature quench.

PubMed

Podariu, Iulia; Chakrabarti, Amitabha

2007-04-21

The authors numerically study a two-step quench process in an asymmetric binary mixture. The mixture is first quenched to an unstable state in the two-phase region. After a large phase-separated structure is formed, the authors again quench the system deeper. The second quench induces the formation of small secondary droplets inside the large domains created by the first quench. The authors characterize this secondary droplet growth in terms of the temperature of the first quench as well as the depth of the second one.

Small-molecule photostabilizing agents are modifiers of lipid bilayer properties.

PubMed

Alejo, Jose L; Blanchard, Scott C; Andersen, Olaf S

2013-06-04

Small-molecule photostabilizing or protective agents (PAs) provide essential support for the stability demands on fluorescent dyes in single-molecule spectroscopy and fluorescence microscopy. These agents are employed also in studies of cell membranes and model systems mimicking lipid bilayer environments, but there is little information about their possible effects on membrane structure and physical properties. Given the impact of amphipathic small molecules on bilayer properties such as elasticity and intrinsic curvature, we investigated the effects of six commonly used PAs--cyclooctatetraene (COT), para-nitrobenzyl alcohol (NBA), Trolox (TX), 1,4-diazabicyclo[2.2.2]octane (DABCO), para-nitrobenzoic acid (pNBA), and n-propyl gallate (nPG)--on bilayer properties using a gramicidin A (gA)-based fluorescence quench assay to probe for PA-induced changes in the gramicidin monomer↔dimer equilibrium. The experiments were done using fluorophore-loaded large unilamellar vesicles that had been doped with gA, and changes in the gA monomer↔dimer equilibrium were assayed using a gA channel-permeable fluorescence quencher (Tl⁺). Changes in bilayer properties caused by, e.g., PA adsorption at the bilayer/solution interface that alter the equilibrium constant for gA channel formation, and thus the number of conducting gA channels in the large unilamellar vesicle membrane, will be detectable as changes in the rate of Tl⁺ influx-the fluorescence quench rate. Over the experimentally relevant millimolar concentration range, TX, NBA, and pNBA, caused comparable increases in gA channel activity. COT, also in the millimolar range, caused a slight decrease in gA channel activity. nPG increased channel activity at submillimolar concentrations. DABCO did not alter gA activity. Five of the six tested PAs thus alter lipid bilayer properties at experimentally relevant concentrations, which becomes important for the design and analysis of fluorescence studies in cells and model membrane systems. We therefore tested combinations of COT, NBA, and TX; the combinations altered the fluorescence quench rate less than would be predicted assuming their effects on bilayer properties were additive. The combination of equimolar concentrations of COT and NBA caused minimal changes in the fluorescence quench rate. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

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.

Reducing Time and Increasing Sensitivity in Sample Preparation for Adherent Mammalian Cell Metabolomics

PubMed Central

Lorenz, Matthew A.; Burant, Charles F.; Kennedy, Robert T.

2011-01-01

A simple, fast, and reproducible sample preparation procedure was developed for relative quantification of metabolites in adherent mammalian cells using the clonal β-cell line INS-1 as a model sample. The method was developed by evaluating the effect of different sample preparation procedures on high performance liquid chromatography- mass spectrometry quantification of 27 metabolites involved in glycolysis and the tricarboxylic acid cycle on a directed basis as well as for all detectable chromatographic features on an undirected basis. We demonstrate that a rapid water rinse step prior to quenching of metabolism reduces components that suppress electrospray ionization thereby increasing signal for 26 of 27 targeted metabolites and increasing total number of detected features from 237 to 452 with no detectable change of metabolite content. A novel quenching technique is employed which involves addition of liquid nitrogen directly to the culture dish and allows for samples to be stored at −80 °C for at least 7 d before extraction. Separation of quenching and extraction steps provides the benefit of increased experimental convenience and sample stability while maintaining metabolite content similar to techniques that employ simultaneous quenching and extraction with cold organic solvent. The extraction solvent 9:1 methanol: chloroform was found to provide superior performance over acetonitrile, ethanol, and methanol with respect to metabolite recovery and extract stability. Maximal recovery was achieved using a single rapid (~1 min) extraction step. The utility of this rapid preparation method (~5 min) was demonstrated through precise metabolite measurements (11% average relative standard deviation without internal standards) associated with step changes in glucose concentration that evoke insulin secretion in the clonal β-cell line INS-1. PMID:21456517

In vitro study on binding interaction of quinapril with bovine serum albumin (BSA) using multi-spectroscopic and molecular docking methods.

PubMed

Shi, Jie-Hua; Pan, Dong-Qi; Jiang, Min; Liu, Ting-Ting; Wang, Qi

2017-08-01

The binding interaction between quinapril (QNPL) and bovine serum albumin (BSA) in vitro has been investigated using UV absorption spectroscopy, steady-state fluorescence spectroscopic, synchronous fluorescence spectroscopy, 3D fluorescence spectroscopy, Fourier transform infrared spectroscopy, circular dichroism, and molecular docking methods for obtaining the binding information of QNPL with BSA. The experimental results confirm that the quenching mechanism of the intrinsic fluorescence of BSA induced by QNPL is static quenching based on the decrease in the quenching constants of BSA in the presence of QNPL with the increase in temperature and the quenching rates of BSA larger than 10 10  L mol -1  s -1 , indicating forming QNPL-BSA complex through the intermolecular binding interaction. The binding constant for the QNPL-BSA complex is in the order of 10 5  M -1 , indicating there is stronger binding interaction of QNPL with BSA. The analysis of thermodynamic parameters together with molecular docking study reveal that the main binding forces in the binding process of QNPL with BSA are van der Waal's forces and hydrogen bonding interaction. And, the binding interaction of BSA with QNPL is an enthalpy-driven process. Based on Förster resonance energy transfer, the binding distance between QNPL and BSA is calculated to be 2.76 nm. The results of the competitive binding experiments and molecular docking confirm that QNPL binds to sub-domain IIA (site I) of BSA. It is confirmed there is a slight change in the conformation of BSA after binding QNPL, but BSA still retains its secondary structure α-helicity.

Characterization of spectral responses of dissolved organic matter (DOM) for atrazine binding during the sorption process onto black soil.

PubMed

Wang, Yifan; Zhang, Xinyuan; Zhang, Xing; Meng, Qingjuan; Gao, Fengjie; Zhang, Ying

2017-08-01

This study was aim to investigate the interaction between soil-derived dissolved organic matter (DOM) and atrazine as a kind of pesticides during the sorption process onto black soil. According to the experimental data, the adsorption capacity of Soil + DOM, Soil and DOM were 41.80, 31.45 and 9.35 mg kg -1 , separately, which indicated that DOM significantly enhanced the adsorption efficiency of atrazine by soil. Data implied that the pseudo-second-order kinetic equation could well explain the adsorption process. The adsorption isotherms (R 2  > 0.99) had a satisfactory fit in both Langmuir and Freundlich models. Three-dimensional excitation-emission matrix (3D-EEM), synchronous fluorescence, two-dimensional correlation spectroscopy (2D-COS) and Fourier transform infrared spectroscopy (FT-IR) were selected to analyze the interaction between DOM and atrazine. 3D-EEM showed that humic acid-like substances were the main component of DOM. The fluorescence of DOM samples were gradually quenched with the increased of atrazine concentrations. Synchronous fluorescence spectra showed that static fluorescence quenching was the main quenching process. 2D-COS indicated that the order of the spectral changes were as following: 336 nm > 282 nm. Furthermore, the fluorescence quenching of humic-like fraction occurred earlier than that of protein-like fraction under atrazine surroundings. FT-IR spectra indicated that main compositions of soil DOM include proteins, polysaccharides and humic substances. The findings of this study are significant to reveal DOM played an important role in the environmental fate of pesticides during sorption process onto black soil and also provide more useful information for understanding the interaction between DOM and pesticides by using spectral responses. Copyright © 2017. Published by Elsevier Ltd.

Aircraft landing dynamics facility carriage weld test program

NASA Technical Reports Server (NTRS)

Lawson, A. G.

1984-01-01

A welded tubular structure constructed of low alloy high strength quenched and tempered steel was tested. The consistency of the mechanical strengths and chemical composition and the degree of difficulty of obtaining full strength welds with these steels is characterized. The results of constructing and testing two typical connections which are used in the structure design are reported.

Partial Coordination Numbers in Binary Metallic Glasses (Postprint)

DTIC Science & Technology

2011-12-07

structural differences related to relative atom size and quench rate. The magnitude of chemical interactions between the atoms, eij, might also influence...vious calculations.[2] A statistical approach is used to develop the Zij equations from the product of four terms: (1) the number of reference sites...within experimental scatter. The development of equations for Zij from the ECP model uses a statistical view of topology, and the Zij values

Multiple Ignition, Normal and Catalytic Combustion and Quenching of Fuel/Air Mixtures.

DTIC Science & Technology

1980-05-10

spray ignition results. Spray systems will be produced using a TSI vibrating orifice aerosol generator. From a small liquid reservoir under high pressure...Liebman used laser ignition of electromagnetically -15- levitated particles. An interesting contradiction presents itself in Figures 7 and 8. Because...the substrate surface has been developed and tested. When the experimental wall temperature is used as boundary condition for the gas- phase equations

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

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

PubMed Central

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

2016-01-01

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. PMID:26896800

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...

Computational quench model applicable to the SMES/CICC

NASA Astrophysics Data System (ADS)

Luongo, Cesar A.; Chang, Chih-Lien; Partain, Kenneth D.

1994-07-01

A computational quench model accounting for the hydraulic peculiarities of the 200 kA SMES cable-in-conduit conductor has been developed. The model is presented and used to simulate the quench on the SMES-ETM. Conclusions are drawn concerning quench detection and protection. A plan for quench model validation is presented.

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.

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.

Multifuel evaluation of rich/quench/lean combustor

NASA Technical Reports Server (NTRS)

Novick, A. S.; Troth, D. L.; Notardonato, J.

1982-01-01

Test results on the RQL low NO(x) industrial gas turbine engine are reported. The air-staged combustor comprises an initial rich burning zone, followed by a quench zone, and a lean reaction and dilution zone. The combustor was tested as part of the DoE/NASA program to define the technology for developing a durable, low-emission gas turbine combustor capable of operation with minimally processed petroleum residual, synthetic, or low/mid-heating value gaseous fuels. The properties of three liquid and two gaseous fuels burned in the combustor trials are detailed. The combustor featured air staging, variable geometry, and generative/convective cooling. The lean/rich mixtures could be varied in zones simultaneously or separately while maintaining a specified pressure drop. Low NO(x) and smoke emissions were produced with each fuel burned, while high combustor efficiencies were obtained.

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.

Residual Stresses in 21-6-9 Stainless Steel Warm Forgings

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

Everhart, Wesley A.; Lee, Jordan D.; Broecker, Daniel J.

Forging residual stresses are detrimental to the production and performance of derived machined parts due to machining distortions, corrosion drivers and fatigue crack drivers. Residual strains in a 21-6-9 stainless steel warm High Energy Rate Forging (HERF) were measured via neutron diffraction. The finite element analysis (FEA) method was used to predict the residual stresses that occur during forging and water quenching. The experimentally measured residual strains were used to calibrate simulations of the three-dimensional residual stress state of the forging. ABAQUS simulation tools predicted residual strains that tend to match with experimental results when varying yield strength is considered.

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

Wallace, Bram; Atzberger, Paul J.; D’Auria, Sabato

Forster resonance energy transfer (FRET) is a widely used single-molecule technique for measuring nanoscale distances from changes in the non-radiative transfer of energy between donor and acceptor fluorophores. For macromolecules and complexes this observed transfer efficiency is used to infer changes in molecular conformation under differing experimental conditions. But, sometimes shifts are observed in the FRET efficiency even when there is strong experimental evidence that the molecular conformational state is unchanged. Here, we investigate ways in which such discrepancies can arise from kinetic effects. We show that significant shifts can arise from the interplay between excitation kinetics, orientation diffusion ofmore » fluorophores, separation diffusion of fluorophores, and non-emitting quenching.« less

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.

Collisions of excited Na atoms with H/sub 2/ molecules. I. Ab initio potential energy surfaces and qualitative discussion of the quenching process

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

Botschwina, P.; Meyer, W.; Hertel, I.V.

Potential energy surfaces have been calculated for the four lowest electronic states of Na (3 /sup 2/S, 3 /sup 2/P)+H/sub 2/(/sup 1/..sigma../sup +//sub g/) by means of the RHF--SCF and PNO--CEPA methods. For the so-called quenching process of Na (3 /sup 2/P) by H/sub 2/ at low initial translational energies (E--VRT energy transfer) the energetically most favorable path occurs in C/sub 2v/ symmetry, since: at intermediate Na--H/sub 2/ separation: the A /sup 2/B/sub 2/ potential energy surface is attractive. From the CEPA calculations, the crossing point of minimal energy between the X /sup 2/A/sub 1/ and A /sup 2/B/sub 2/more » surfaces is obtained at R/sub c/ = 3.57 a.u. and r/sub c/ = 2.17 a.u. with an energy difference to the asymptotic limit (R = infinity, r = r/sub e/) of -0.06 eV. It is thus classically accessible without any initial translational energy, but at low initial translational energies (approx.0.1 eV) quenching will be efficient only for arrangements of collision partners close to C/sub 2v/ symmetry. There is little indication of an avoiding crossing with an ionic intermediate correlating asymptotically with Na/sup +/ and H/sub 2//sup -/ as was assumed in previous discussions of the quenching process. The dependence of the total quenching cross sections on the initial translational energy is discussed by means of the ''absorbing sphere'' model, taking the initial zero-point vibrational energy of the hydrogen molecule into account. New experimental data of the product channel distribution in H/sub 2/ for center-of-mass forward scattering are presented. The final vibrational states v' = 3, 2, 1, and 0 of H/sub 2/ are populated to about 26%, 61%, 13%, and 0%, respectively. The observed distributions in H/sub 2/ (and D/sub 2/) may be rationalized by simple dynamic considerations on the basis of the calculated surfaces.« less

The test facility for the short prototypes of the LHC superconducting magnets

NASA Astrophysics Data System (ADS)

Delsolaro, W. Venturini; Arn, A.; Bottura, L.; Giloux, C.; Mompo, R.; Siemko, A.; Walckiers, L.

2002-05-01

The LHC development program relies on cryogenic tests of prototype and model magnets. This vigorous program is pursued in a dedicated test facility based on several vertical cryostats working at superfluid helium temperatures. The performance of the facility is detailed. Goals and test equipment for currently performed studies are reviewed: quench analysis and magnet protection studies, measurement of the field quality, test of ancillary electrical equipment like diodes and busbars. The paper covers the equipment available for tests of prototypes and some special series of LHC magnets to come.

Contribution to the aluminum-tin-zinc ternary system

NASA Astrophysics Data System (ADS)

Drápala, J.; Kostiuková, G.; Losertová, M.

2017-11-01

The Sn-Zn-Al alloys are one of significant candidates in the proposal of alternative lead-free solders for higher temperature soldering. This paper deals with the study of the aluminum-tin-zinc system. Twenty Sn-Zn-Al alloys together with six binary Sn-Zn alloys were prepared and studied experimentally. Alloys were prepared from pure Sn, Zn and Al (melting and cooling in a vacuum resistance furnace). The specimens were studied metallographically including the micro-hardness measurements, complete chemical analysis (ICP-AES, OES), X-ray micro-analysis of alloys by SEM and EDX in order to determine the composition and identification of individual phases. Significant temperatures and enthalpies of phase transformations were determined by DTA. After long-term annealing of selected alloys in vacuum followed by quenching the structural and chemical microanalyses of the present phases and their limit concentrations were carried out. The achieved results were compared with the thermodynamic modelling of the ternary Sn-Zn-Al system (computer programs THERMOCALC, MTDATA, PANDAT and databases CALPHAD, COST). Electrical resistivity, density, magnetic susceptibility and wettability of Sn-Zn-Al solders were measured as well.

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.

A systematic characterization of the low-energy photon response of plastic scintillation detectors.

PubMed

Boivin, Jonathan; Beddar, Sam; Bonde, Chris; Schmidt, Daniel; Culberson, Wesley; Guillemette, Maxime; Beaulieu, Luc

2016-08-07

To characterize the low energy behavior of scintillating materials used in plastic scintillation detectors (PSDs), 3 PSDs were developed using polystyrene-based scintillating materials emitting in different wavelengths. These detectors were exposed to National Institute of Standards and Technology (NIST)-matched low-energy beams ranging from 20 kVp to 250 kVp, and to (137)Cs and (60)Co beams. The dose in polystyrene was compared to the dose in air measured by NIST-calibrated ionization chambers at the same location. Analysis of every beam quality spectrum was used to extract the beam parameters and the effective mass energy-absorption coefficient. Monte Carlo simulations were also performed to calculate the energy absorbed in the scintillators' volume. The scintillators' expected response was then compared to the experimental measurements and an energy-dependent correction factor was identified to account for low-energy quenching in the scintillators. The empirical Birks model was then compared to these values to verify its validity for low-energy electrons. The clear optical fiber response was below 0.2% of the scintillator's light for x-ray beams, indicating that a negligible amount of fluorescence contamination was produced. However, for higher-energy beams ((137)Cs and (60)Co), the scintillators' response was corrected for the Cerenkov stem effect. The scintillators' response increased by a factor of approximately 4 from a 20 kVp to a (60)Co beam. The decrease in sensitivity from ionization quenching reached a local minimum of about [Formula: see text] between 40 keV and 60 keV x-ray beam mean energy, but dropped by 20% for very low-energy (13 keV) beams. The Birks model may be used to fit the experimental data, but it must take into account the energy dependence of the kB quenching parameter. A detailed comprehension of intrinsic scintillator response is essential for proper calibration of PSD dosimeters for radiology.

A systematic characterization of the low-energy photon response of plastic scintillation detectors

NASA Astrophysics Data System (ADS)

Boivin, Jonathan; Beddar, Sam; Bonde, Chris; Schmidt, Daniel; Culberson, Wesley; Guillemette, Maxime; Beaulieu, Luc

2016-08-01

To characterize the low energy behavior of scintillating materials used in plastic scintillation detectors (PSDs), 3 PSDs were developed using polystyrene-based scintillating materials emitting in different wavelengths. These detectors were exposed to National Institute of Standards and Technology (NIST)-matched low-energy beams ranging from 20 kVp to 250 kVp, and to 137Cs and 60Co beams. The dose in polystyrene was compared to the dose in air measured by NIST-calibrated ionization chambers at the same location. Analysis of every beam quality spectrum was used to extract the beam parameters and the effective mass energy-absorption coefficient. Monte Carlo simulations were also performed to calculate the energy absorbed in the scintillators’ volume. The scintillators’ expected response was then compared to the experimental measurements and an energy-dependent correction factor was identified to account for low-energy quenching in the scintillators. The empirical Birks model was then compared to these values to verify its validity for low-energy electrons. The clear optical fiber response was below 0.2% of the scintillator’s light for x-ray beams, indicating that a negligible amount of fluorescence contamination was produced. However, for higher-energy beams (137Cs and 60Co), the scintillators’ response was corrected for the Cerenkov stem effect. The scintillators’ response increased by a factor of approximately 4 from a 20 kVp to a 60Co beam. The decrease in sensitivity from ionization quenching reached a local minimum of about 11%+/- 1% between 40 keV and 60 keV x-ray beam mean energy, but dropped by 20% for very low-energy (13 keV) beams. The Birks model may be used to fit the experimental data, but it must take into account the energy dependence of the kB quenching parameter. A detailed comprehension of intrinsic scintillator response is essential for proper calibration of PSD dosimeters for radiology.

Empirically based device modeling of bulk heterojunction organic photovoltaics

NASA Astrophysics Data System (ADS)

Pierre, Adrien; Lu, Shaofeng; Howard, Ian A.; Facchetti, Antonio; Arias, Ana Claudia

2013-04-01

We develop an empirically based optoelectronic model to accurately simulate the photocurrent in organic photovoltaic (OPV) devices with novel materials including bulk heterojunction OPV devices based on a new low band gap dithienothiophene-DPP donor polymer, P(TBT-DPP), blended with PC70BM at various donor-acceptor weight ratios and solvent compositions. Our devices exhibit power conversion efficiencies ranging from 1.8% to 4.7% at AM 1.5G. Electron and hole mobilities are determined using space-charge limited current measurements. Bimolecular recombination coefficients are both analytically calculated using slowest-carrier limited Langevin recombination and measured using an electro-optical pump-probe technique. Exciton quenching efficiencies in the donor and acceptor domains are determined from photoluminescence spectroscopy. In addition, dielectric and optical constants are experimentally determined. The photocurrent and its bias-dependence that we simulate using the optoelectronic model we develop, which takes into account these physically measured parameters, shows less than 7% error with respect to the experimental photocurrent (when both experimentally and semi-analytically determined recombination coefficient is used). Free carrier generation and recombination rates of the photocurrent are modeled as a function of the position in the active layer at various applied biases. These results show that while free carrier generation is maximized in the center of the device, free carrier recombination is most dominant near the electrodes even in high performance devices. Such knowledge of carrier activity is essential for the optimization of the active layer by enhancing light trapping and minimizing recombination. Our simulation program is intended to be freely distributed for use in laboratories fabricating OPV devices.

Experimental Investigation of Gas/Slag/Matte/Tridymite Equilibria in the Cu-Fe-O-S-Si System in Controlled Atmospheres: Development of Technique

NASA Astrophysics Data System (ADS)

Fallah-Mehrjardi, Ata; Hidayat, Taufiq; Hayes, Peter C.; Jak, Evgueni

2017-12-01

The majority of primary pyrometallurgical copper making processes involve the formation of two immiscible liquid phases, i.e., matte product and the slag phase. There are significant gaps and discrepancies in the phase equilibria data of the slag and the matte systems due to issues and difficulties in performing the experiments and phase analysis. The present study aims to develop an improved experimental methodology for accurate characterisation of gas/slag/matte/tridymite equilibria in the Cu-Fe-O-S-Si system under controlled atmospheres. The experiments involve high-temperature equilibration of synthetic mixtures on silica substrates in CO/CO2/SO2/Ar atmospheres, rapid quenching of samples into water, and direct composition measurement of the equilibrium phases using Electron Probe X-ray Microanalysis (EPMA). A four-point-test procedure was applied to ensure the achievement of equilibrium, which included the following: (i) investigation of equilibration as a function of time, (ii) assessment of phase homogeneity, (iii) confirmation of equilibrium by approaching from different starting conditions, and (iv) systematic analysis of the reactions specific to the system. An iterative improved experimental methodology was developed using this four-point-test approach to characterize the complex multi-component, multi-phase equilibria with high accuracy and precision. The present study is a part of a broader overall research program on the characterisation of the multi-component (Cu-Fe-O-S-Si-Al-Ca-Mg), multi-phase (gas/slag/matte/metal/solids) systems with minor elements (Pb, Zn, As, Bi, Sn, Sb, Ag, and Au).

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.

Ultimate Gradient Limitation in Niobium Superconducting Accelerating Cavities

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

Checchin, Mattia; Grassellino, Anna; Martinello, Martina

2016-06-01

The present study is addressed to the theoretical description of the ultimate gradient limitation in SRF cavities. Our intent is to exploit experimental data to confirm models which provide feed-backs on how to improve the current state-of-art. New theoretical insight on the cavities limiting factor can be suitable to improve the quench field of N-doped cavities, and therefore to take advantage of high Q 0 at high gradients.

Photoluminescence of cerium fluoride and cerium-doped lanthanum fluoride nanoparticles and investigation of energy transfer to photosensitizer molecules.

PubMed

Cooper, Daniel R; Kudinov, Konstantin; Tyagi, Pooja; Hill, Colin K; Bradforth, Stephen E; Nadeau, Jay L

2014-06-28

CexLa1-xF3 nanoparticles have been proposed for use in nanoscintillator-photosensitizer systems, where excitation of nanoparticles by ionizing radiation would result in energy transfer to photosensitizer molecules, effectively combining the effects of radiotherapy and photodynamic therapy. Thus far, there have been few experimental investigations of such systems. This study reports novel synthesis methods for water-dispersible Ce0.1La0.9F3/LaF3 and CeF3/LaF3 core/shell nanoparticles and an investigation of energy transfer to photosensitizers. Unbound deuteroporphyrin IX 2,4-disulfonic acid was found to substantially quench the luminescence of large (>10 nm diameter) aminocaproic acid-stabilized nanoparticles at reasonable concentrations and loading amounts: up to 80% quenching at 6% w/w photosensitizer loading. Energy transfer was found to occur primarily through a cascade, with excitation of "regular" site Ce(3+) at 252 nm relayed to photosensitizer molecules at the nanoparticle surface through intermediate "perturbed" Ce(3+) sites. Smaller (<5 nm) citrate-stabilized nanoparticles were coated with the bisphosphonate alendronate, allowing covalent conjugation to chlorin e6 and resulting in static quenching of the nanoparticle luminescence: ∼50% at ∼0.44% w/w. These results provide insight into energy transfer mechanisms that may prove valuable for optimizing similar systems.

Relaxation of the non-photochemical chlorophyll fluorescence quenching in diatoms: kinetics, components and mechanisms

PubMed Central

Roháček, Karel; Bertrand, Martine; Moreau, Brigitte; Jacquette, Boris; Caplat, Christelle; Morant-Manceau, Annick; Schoefs, Benoît

2014-01-01

Diatoms are especially important microorganisms because they constitute the larger group of microalgae. To survive the constant variations of the light environment, diatoms have developed mechanisms aiming at the dissipation of excess energy, such as the xanthophyll cycle and the non-photochemical chlorophyll (Chl) fluorescence quenching. This contribution is dedicated to the relaxation of the latter process when the adverse conditions cease. An original nonlinear regression analysis of the relaxation of non-photochemical Chl fluorescence quenching, qN, in diatoms is presented. It was used to obtain experimental evidence for the existence of three time-resolved components in the diatom Phaeodactylum tricornutum: qNf, qNi and qNs. qNf (s time-scale) and qNs (h time-scale) are exponential in shape. By contrast, qNi (min time-scale) is of sigmoidal nature and is dominant among the three components. The application of metabolic inhibitors (dithiothreitol, ammonium chloride, cadmium and diphenyleneiodonium chloride) allowed the identification of the mechanisms on which each component mostly relies. qNi is linked to the relaxation of the ΔpH gradient and the reversal of the xanthophyll cycle. qNs quantifies the stage of photoinhibition caused by the high light exposure, qNf seems to reflect fast conformational changes within thylakoid membranes in the vicinity of the photosystem II complexes. PMID:24591721

Study on interaction between curcumin and pepsin by spectroscopic and docking methods.

PubMed

Ying, Ming; Huang, Fengwen; Ye, Haidong; Xu, Hong; Shen, Liangliang; Huan, Tianwen; Huang, Shitong; Xie, Jiangfeng; Tian, Shengli; Hu, Zhangli; He, Zhendan; Lu, Jun; Zhou, Kai

2015-08-01

The interaction between curcumin and pepsin was investigated by fluorescence, synchronous fluorescence, UV-vis absorption, circular dichroism (CD), and molecular docking. Under physiological pH value in stomach, the fluorescence of pepsin can be quenched effectively by curcumin via a combined quenching process. Binding constant (Ka) and binding site number (n) of curcumin to pepsin were obtained. According to the theory of Förster's non-radiation energy transfer, the distance r between pepsin and curcumin was found to be 2.45 nm within the curcumin-pepsin complex, which implies that the energy transfer occurs between curcumin and pepsin, leading to the quenching of pepsin fluorescence. Fluorescence experiments also suggest that curcumin is located more closely to tryptophan residues than tyrosine residues. CD spectra together with UV-vis absorbance studies show that binding of curcumin to pepsin results in the extension of peptide strands of pepsin with loss of some β-sheet structures. Thermodynamic parameters calculated from the binding constants at different temperatures reveal that hydrophobic force plays a major role in stabilizing the curcumin-pepsin complex. In addition, docking results support the above experimental findings and suggest the possible hydrogen bonds of curcumin with Thr-77, Thr-218, and Glu-287 of pepsin, which help further stabilize the curcumin-pepsin complex. Copyright © 2015 Elsevier B.V. All rights reserved.

Intermolecular interaction of fosinopril with bovine serum albumin (BSA): The multi-spectroscopic and computational investigation.

PubMed

Zhou, Kai-Li; Pan, Dong-Qi; Lou, Yan-Yue; Shi, Jie-Hua

2018-04-16

The intermolecular interaction of fosinopril, an angiotensin converting enzyme inhibitor with bovine serum albumin (BSA), has been investigated in physiological buffer (pH 7.4) by multi-spectroscopic methods and molecular docking technique. The results obtained from fluorescence and UV absorption spectroscopy revealed that the fluorescence quenching mechanism of BSA induced by fosinopril was mediated by the combined dynamic and static quenching, and the static quenching was dominant in this system. The binding constant, K b , value was found to lie between 2.69 × 10 3 and 9.55 × 10 3  M -1 at experimental temperatures (293, 298, 303, and 308 K), implying the low or intermediate binding affinity between fosinopril and BSA. Competitive binding experiments with site markers (phenylbutazone and diazepam) suggested that fosinopril preferentially bound to the site I in sub-domain IIA on BSA, as evidenced by molecular docking analysis. The negative sign for enthalpy change (ΔH 0 ) and entropy change (ΔS 0 ) indicated that van der Waals force and hydrogen bonds played important roles in the fosinopril-BSA interaction, and 8-anilino-1-naphthalenesulfonate binding assay experiments offered evidence of the involvements of hydrophobic interactions. Moreover, spectroscopic results (synchronous fluorescence, 3-dimensional fluorescence, and Fourier transform infrared spectroscopy) indicated a slight conformational change in BSA upon fosinopril interaction. Copyright © 2018 John Wiley & Sons, Ltd.

Insights into the binding behavior of bovine serum albumin to black carbon nanoparticles and induced cytotoxicity

NASA Astrophysics Data System (ADS)

Wu, Hai; Chen, Miaomiao; Shang, Mengting; Li, Xiang; Mu, Kui; Fan, Suhua; Jiang, Shuanglin; Li, Wenyong

2018-07-01

Black carbon (BC) is a main component of particulate matter (PM2.5). Due to their small size (<100 nm), inhaled ultrafine BC nanoparticles may penetrate the lung alveoli, where they interact with surfactant proteins and lipids, causing more serious damage to human health. Here, BC was analyzed to investigate the binding mechanism of its interaction with protein and induction of cytotoxicity changes. The binding process and protein conformation between BC and a serum protein (bovine serum albumin, BSA) were monitored by using a fluorescence quenching technique and UV-vis absorption, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopies. The experimental results revealed that the fluorescence quenching of BSA induced by BC was a static quenching process and the hydrophobic force played the critical role in the interaction. The native conformation of BSA on the BC surface was slightly disturbed but obvious structural unfolding of the secondary structure did not occur. In the cytotoxicity study, BC nanoparticles with low concentrations exhibited strong toxicity towards BEAS-2B cells. However, the toxicity of BC nanoparticles could be mitigated by the presence of BSA. Therefore, proteins in biological fluids likely reduce the toxic effect of BC on human health. These findings delineated the binding mechanism and the toxicity between BC and the BSA-BC system, contributing to the understanding of the biological effects of BC exposure on human health in polluted atmospheres.

Self-organization, interfacial interaction and photophysical properties of gold nanoparticle complexes derived from resilin-mimetic fluorescent protein rec1-resilin.

PubMed

Mayavan, Sundar; Dutta, Naba K; Choudhury, Namita R; Kim, Misook; Elvin, Christopher M; Hill, Anita J

2011-04-01

In this investigation we report the synthesis of optically coupled hybrid architectures based on a new biomimetic fluorescent protein rec1-resilin and nanometer-scale gold nanoparticles (AuNPs) in a one-step method using a non-covalent mode of binding protocol. The presence of uniformly distributed fluorophore sequences, -Ser(Thr)-Tyr-Gly- along the molecular structure of rec1-resilin provides significant opportunity to synthesize fluorophore-modified AuNPs bioconjugates with unique photophysical properties. The detailed analyses of the AuNP-bioconjugates, synthesized under different experimental conditions using spectroscopic, microscopic and scattering techniques demonstrate the organizational pathways and the electronic and photophysical properties of the developed AuNP-rec1-resilin bioconjugates. The calculation of the bimolecular quenching constant using the Stern-Volmer equation confirms that the dominant mechanism involved in quenching of fluorescence of rec1-resilin in the presence of AuNP is static. Photoacoustic infrared spectroscopy was employed to understand the nature of the interfacial interaction between the AuNP and rec1-resilin and its evolution with pH. In such bioconjugates the quenched emission of fluorescence by AuNP on the fluorophore moiety of rec1-resilin in the immediate vicinity of the AuNP has significant potential for fluorescence-based detection schemes, sensors and also can be incorporated into nanoparticle-based devices. Copyright © 2011 Elsevier Ltd. All rights reserved.

Ag nanoclusters could efficiently quench the photoresponse of CdS quantum dots for novel energy transfer-based photoelectrochemical bioanalysis.

PubMed

Zhang, Ling; Sun, Yue; Liang, Yan-Yu; He, Jian-Ping; Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

2016-11-15

Herein the influence of ultrasmall Ag nanoclusters (Ag NCs) against CdS quantum dots (QDs) in a photoelectrochemical (PEC) nanosystem was exploited for the first time, based on which a novel PEC bioanalysis was successfully developed via the efficient quenching effect of Ag NCs against the CdS QDs. In a model system, DNA assay was achieved by using molecular beacon (MB) probes anchored on a CdS QDs modified electrode, and the MB probes contain two segments that can hybridize with both target DNA sequence and the label of DNA encapsulated Ag NCs. After the MB probe was unfolded by the target DNA sequence, the labels of oligonucleotide encapsulated Ag NCs would be brought in close proximity to the CdS QDs electrode surface, and efficient photocurrent quenching of QDs could be resulted from an energy transfer process that originated from NCs. Thus, by monitoring the attenuation in the photocurrent signal, an elegant and sensitive PEC DNA bioanalysis could be accomplished. The developed biosensor displayed a linear range from 1.0pM to 10nM and the detection limit was experimentally found to be of 0.3pM. This work presents a feasible signaling principle that could act as a common basis for general PEC bioanalysis development. Copyright © 2016 Elsevier B.V. All rights reserved.

Optical detection of organophosphorus compounds based on Mn-doped ZnSe d-dot enzymatic catalytic sensor.

PubMed

Gao, Xue; Tang, Guangchao; Su, Xingguang

2012-01-01

In this paper, we report a sensitive and selective method for detection of organophosphorus compounds (OPs) based on Mn:ZnSe d-dots-enzyme-hydrogen peroxide (H(2)O(2)) fluorescence quenching system. Acetylcholine esterase (AChE) can hydrolyze acetylcholine (ACh) to choline. Subsequently, choline oxidase (ChOx) oxidizes choline to generate H(2)O(2). The enzyme-generated H(2)O(2) can quench the fluorescence of Mn:ZnSe d-dots. When paraoxon are introduced in solution, it can interact with the active centers of AChE and decrease the enzyme activity. This leads to the decrease of the H(2)O(2) production and then the fluorescence quenching rate of Mn:ZnSe d-dots. Experimental results showed that the enzyme inhibition percentage of Mn:ZnSe d-dots-ChOx-AChE-ACh system was proportional to the logarithm of paraoxon in the range 4.84×10(-11) to 4.84×10(-6) mol/L with the detection limit (S/N=3) of 1.31×10(-11) mol/L. The proposed biosensor has been employed for quick determination of paraoxon in tap water and milk samples with satisfactory reproducibility and accuracy. This nano-biosensor was proved to be sensitive, rapid, simple and tolerance of most interfering substances. Copyright © 2012 Elsevier B.V. All rights reserved.

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.

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.

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.

Analytical platform for metabolome analysis of microbial cells using methyl chloroformate derivatization followed by gas chromatography-mass spectrometry.

PubMed

Smart, Kathleen F; Aggio, Raphael B M; Van Houtte, Jeremy R; Villas-Bôas, Silas G

2010-09-01

This protocol describes an analytical platform for the analysis of intra- and extracellular metabolites of microbial cells (yeast, filamentous fungi and bacteria) using gas chromatography-mass spectrometry (GC-MS). The protocol is subdivided into sampling, sample preparation, chemical derivatization of metabolites, GC-MS analysis and data processing and analysis. This protocol uses two robust quenching methods for microbial cultures, the first of which, cold glycerol-saline quenching, causes reduced leakage of intracellular metabolites, thus allowing a more reliable separation of intra- and extracellular metabolites with simultaneous stopping of cell metabolism. The second, fast filtration, is specifically designed for quenching filamentous micro-organisms. These sampling techniques are combined with an easy sample-preparation procedure and a fast chemical derivatization reaction using methyl chloroformate. This reaction takes place at room temperature, in aqueous medium, and is less prone to matrix effect compared with other derivatizations. This protocol takes an average of 10 d to complete and enables the simultaneous analysis of hundreds of metabolites from the central carbon metabolism (amino and nonamino organic acids, phosphorylated organic acids and fatty acid intermediates) using an in-house MS library and a data analysis pipeline consisting of two free software programs (Automated Mass Deconvolution and Identification System (AMDIS) and R).

[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.

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.

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

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.

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

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.

Measurement of the initial phase of ozone decomposition in water and wastewater by means of a continuous quench-flow system: application to disinfection and pharmaceutical oxidation.

PubMed

Buffle, Marc-Olivier; Schumacher, Jochen; Salhi, Elisabeth; Jekel, Martin; von Gunten, Urs

2006-05-01

Due to a lack of adequate experimental techniques, the kinetics of the first 20s of ozone decomposition in natural water and wastewater is still poorly understood. Introducing a continuous quench-flow system (CQFS), measurements starting 350 ms after ozone addition are presented for the first time. Very high HO. to O3 exposures ratios (Rct=integralHO.dt/integralO3dt) reveal that the first 20s of ozonation present oxidation conditions that are similar to ozone-based advanced oxidation processes (AOP). The oxidation of carbamazepine could be accurately modeled using O3 and HO. exposures measured with CQFS during wastewater ozonation. These results demonstrate the applicability of bench scale determined second-order rate constants for wastewater ozonation. Important degrees of pharmaceutical oxidation and microbial inactivation are predicted, indicating that a significant oxidation potential is available during wastewater ozonation, even when ozone is entirely decomposed in the first 20s.

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

Optimization of fluorimetric lipid membrane biosensor sensitivity through manipulation of membrane structure and nitrobenzoxadiazole dipalmitoylphosphatidylethanolamine concentration

NASA Astrophysics Data System (ADS)

Shrive, Jason D. A.; Krull, Ulrich J.

1995-01-01

In the work reported here, surface concentrations of 0.027 and 0.073 molecules nm-2 of the fluorescent membrane probe molecule nitrobenzoxadiazole dipalmitoylphosphatidylethanolamine (NBD-PE) were shown to yield optimum sensitivity for fluorimetric transduction of membrane structural perturbations for lipid membrane-based biosensor development. These optima were obtained through correlation of experimental data with theoretical predictions of optimum surface concentrations based on a model for NBD-PE self quenching previously published by our group. It was also determined that membrane structural heterogeneity improves the sensitivity of NBD-PE labeled membrane transducers. Together with fluorescence microscopy, observations of surface potential change upon compression or expansion of phosphatidylcholine (PC)/phosphatidic acid (PA) monolayers were used to qualitatively indicate the degree of structural heterogeneity in these membranes. It was determined that sub-microscopic domains must exist in microscopically homogeneous egg PC/egg PA membranes in order to facilitate the observed NBD-PE self-quenching responses upon alteration of bulk pH and therefore, membrane surface electrostatics and structure.

Observation of dynamical vortices after quenches in a system with topology

NASA Astrophysics Data System (ADS)

Fläschner, N.; Vogel, D.; Tarnowski, M.; Rem, B. S.; Lühmann, D.-S.; Heyl, M.; Budich, J. C.; Mathey, L.; Sengstock, K.; Weitenberg, C.

2018-03-01

Topological phases constitute an exotic form of matter characterized by non-local properties rather than local order parameters1. The paradigmatic Haldane model on a hexagonal lattice features such topological phases distinguished by an integer topological invariant known as the first Chern number2. Recently, the identification of non-equilibrium signatures of topology in the dynamics of such systems has attracted particular attention3-6. Here, we experimentally study the dynamical evolution of the wavefunction using time- and momentum-resolved full state tomography for spin-polarized fermionic atoms in driven optical lattices7. We observe the appearance, movement and annihilation of dynamical vortices in momentum space after sudden quenches close to the topological phase transition. These dynamical vortices can be interpreted as dynamical Fisher zeros of the Loschmidt amplitude8, which signal a so-called dynamical phase transition9,10. Our results pave the way to a deeper understanding of the connection between topological phases and non-equilibrium dynamics.

A coumarin-derived Cu2 +-fluorescent chemosensor and its direct application in aqueous media

NASA Astrophysics Data System (ADS)

Mergu, Naveen; Kim, Myeongjin; Son, Young-A.

2018-01-01

A novel coumarin-based receptor bearing a benzohydrazide (FCBH) was developed as a fluorescent chemosensor with high selectivity toward Cu2 +. The sensor was successfully applied to the monitoring of Cu2 + in aqueous solution. After the addition of Cu2 + to FCBH, the color of the solution changed from greenish-yellow to red, and the absorption band at 457 nm red-shifted to 517 nm. The fluorescent green color of FCBH disappeared and the fluorescence emission was completely quenched in the presence of Cu2 +. Upon the addition of Cu2 +, deprotonation of FCBH occurred, and a 1:1 metal-ligand complex formed. DFT theoretical investigation was carried out to understand the behavior of the sensing probe toward Cu2 +. Additionally, the quenched fluorescence of the FCBH-Cu2 + complex was restored upon the addition of CN- ions. The possible sensing mechanism of FCBH toward Cu2 + was derived from experimental and theoretical examinations.

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.

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.

Glimmers of a Quantum KAM Theorem: Insights from Quantum Quenches in One-Dimensional Bose Gases

DOE PAGES

Brandino, G. P.; Caux, J. -S.; Konik, R. M.

2015-12-16

Real-time dynamics in a quantum many-body system are inherently complicated and hence difficult to predict. There are, however, a special set of systems where these dynamics are theoretically tractable: integrable models. Such models possess non-trivial conserved quantities beyond energy and momentum. These quantities are believed to control dynamics and thermalization in low dimensional atomic gases as well as in quantum spin chains. But what happens when the special symmetries leading to the existence of the extra conserved quantities are broken? Is there any memory of the quantities if the breaking is weak? Here, in the presence of weak integrability breaking,more » we show that it is possible to construct residual quasi-conserved quantities, so providing a quantum analog to the KAM theorem and its attendant Nekhoreshev estimates. We demonstrate this construction explicitly in the context of quantum quenches in one-dimensional Bose gases and argue that these quasi-conserved quantities can be probed experimentally.« less

Investigation of laser-induced iodine fluorescence for the measurement of density in compressible flows

NASA Technical Reports Server (NTRS)

Mcdaniel, J. C., Jr.

1982-01-01

Laser induced fluorescence is an attractive nonintrusive approach for measuring molecular number density in compressible flows although this technique does not produce a signal that is directly related to the number density. Saturation and frequency detuned excitation are explored as means for minimizing the quenching effect using iodine as the molecular system because of its convenient absorption spectrum. Saturation experiments indicate that with available continuous wave laser sources of Gaussian transverse intensity distribution only partial saturation could be achieved in iodine at the pressures of interest in gas dynamics. Using a fluorescence lineshape theory, it is shown that for sufficiently large detuning of a narrow bandwidth laser from a molecular transition, the quenching can be cancelled by collisional broadening over a large range of pressures and temperatures. Experimental data obtained in a Mach 4.3 underexpanded jet of nitrogen seeded with iodine for various single mode argon laser detunings from a strong iodine transition at 5145 A are discussed.

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.

The design and application of fluorophore–gold nanoparticle activatable probes

PubMed Central

Swierczewska, Magdalena; Lee, Seulki; Chen, Xiaoyuan

2013-01-01

Fluorescence-based assays and detection techniques are among the most highly sensitive and popular biological tests for researchers. To match the needs of research and the clinic, detection limits and specificities need to improve, however. One mechanism is to decrease non-specific background signals, which is most efficiently done by increasing fluorescence quenching abilities. Reports in the literature of theoretical and experimental work have shown that metallic gold surfaces and nanoparticles are ultra-efficient fluorescence quenchers. Based on these findings, subsequent reports have described gold nanoparticle fluorescence-based activatable probes that were designed to increase fluorescence intensity based on a range of stimuli. In this way, these probes can detect and signify assorted biomarkers and changes in environmental conditions. In this review, we explore the various factors and theoretical models that affect gold nanoparticle fluorescence quenching, explore current uses of activatable probes, and propose an engineering approach for future development of fluorescence based gold nanoparticle activatable probes. PMID:21380462

Roper resonance and S11(1535) from lattice QCD

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

N. Mathur; Y. Chen; S.J. Dong

2005-01-06

Using the constrained curve fitting method and overlap fermions with the lowest pion mass at 180 MeV, we observe that the masses of the first positive and negative parity excited states of the nucleon tend to cross over as the quark masses are taken to the chiral limit. Both results at the physical pion mass agree with the experimental values of the Roper resonance (N{sup 1/2+} (1440)) and S{sub 11} (N{sup 1/2-}(1535)). This is seen for the first time in a lattice QCD calculation. These results are obtained on a quenched Iwasaki 16{sup 3} x 28 lattice with a =more » 0.2 fm. We also extract the ghost {eta}{prime} N states (a quenched artifact) which are shown to decouple from the nucleon interpolation field above m{sub {pi}} {approx} 300 MeV. From the quark mass dependence of these states in the chiral region, we conclude that spontaneously broken chiral symmetry dictates the dynamics of light quarks in the nucleon.« less

New anthracene derivatives as triplet acceptors for efficient green-to-blue low-power upconversion.

PubMed

Liang, Zuo-Qin; Sun, Bin; Ye, Chang-Qing; Wang, Xiao-Mei; Tao, Xu-Tang; Wang, Qin-Hua; Ding, Ping; Wang, Bao; Wang, Jing-Jing

2013-10-21

Three new anthracene derivatives [2-chloro-9,10-dip-tolylanthracene (DTACl), 9,10-dip-tolylanthracene-2-carbonitrile (DTACN), and 9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile (DNACN)] were synthesized as triplet acceptors for low-power upconversion. Their linear absorption, single-photon-excited fluorescence, and upconversion fluorescence properties were studied. The acceptors exhibit high fluorescence yields in DMF. Selective excitation of the sensitizer Pd(II)octaethylporphyrin (PdOEP) in solution containing DTACl, DTACN, or DNA-CN at 532 nm with an ultralow excitation power density of 0.5 W cm(-2) results in anti-Stokes blue emission. The maximum upconversion quantum yield (Φ(UC) =17.4%) was obtained for the couple PdOEP/DTACl. In addition, the efficiency of the triplet-triplet energy transfer process was quantitatively studied by quenching experiments. Experimental results revealed that a highly effective acceptor for upconversion should combine high fluorescence quantum yields with efficient quenching of the sensitizer triplet. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantum confinement effect in 6H-SiC quantum dots observed via plasmon-exciton coupling-induced defect-luminescence quenching

NASA Astrophysics Data System (ADS)

Guo, Xiaoxiao; Zhang, Yumeng; Fan, Baolu; Fan, Jiyang

2017-03-01

The quantum confinement effect is one of the crucial physical effects that discriminate a quantum material from its bulk material. It remains a mystery why the 6H-SiC quantum dots (QDs) do not exhibit an obvious quantum confinement effect. We study the photoluminescence of the coupled colloidal system of SiC QDs and Ag nanoparticles. The experimental result in conjunction with the theoretical calculation reveals that there is strong coupling between the localized electron-hole pair in the SiC QD and the localized surface plasmon in the Ag nanoparticle. It results in resonance energy transfer between them and resultant quenching of the blue surface-defect luminescence of the SiC QDs, leading to uncovering of a hidden near-UV emission band. This study shows that this emission band originates from the interband transition of the 6H-SiC QDs and it exhibits a remarkable quantum confinement effect.

Observation of thermal quench induced by runaway electrons in magnetic perturbation

NASA Astrophysics Data System (ADS)

Cheon, MunSeong; Seo, Dongcheol; Kim, Junghee

2018-04-01

Experimental observations in Korea Superconducting Tokamak Advanced Research (KSTAR) plasmas show that a loss of pre-disruptive runaway electrons can induce a rapid radiative cooling of the plasma, by generating impurity clouds from the first wall. The synchrotron radiation image shows that the loss of runaway electrons occurs from the edge region when the resonant magnetic perturbation is applied on the plasma. When the impact of the runaway electrons on the wall is strong enough, a sudden drop of the electron cyclotron emission (ECE) signal occurs with the characteristic plasma behaviors such as the positive spike and following decay of the plasma current, Dα spike, big magnetic fluctuation, etc. The visible images at this runaway loss show an evidence of the generation of impurity cloud and the following radiative cooling. When the runaway beam is located on the plasma edge, thermal quenches are expected to occur without global destruction of the magnetic structure up to the core.

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.

Quench propagation in the superconducting 6 kA flexible busbars of the LHC

NASA Astrophysics Data System (ADS)

Herzog, R.; Calvi, M.; Sonnemann, F.; Pelegrin-Carcelen, J. M.

2002-05-01

Flexible superconducting cables with currents up to 6 kA will be used to power magnets individually in the insertion regions of the LHC. In case of a quench, the currents in these circuits will decay very fast (with time constants of about 200 ms) such that relatively small copper cross sections are sufficient for these busbars. Quench propagation experiments on a prototype cable and corresponding simulations led to a detailed understanding of the quench behavior of these busbars and to recommendations for the design and application of the cable. Simulations of the quench process in a multi-strand conductor led to a detailed understanding of the way current crosses from superconducting to pure copper strands and how this affects the quench propagation velocity. At nominal current (6 kA), the quench propagation velocities are high (10 m/s) and the hot spot temperature increases rapidly. In this situation, timely quench detection and energy extraction (current reduction) are vital to prevent damage of circuit components.

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

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.

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.

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.

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.

Collisional Dynamics of the B 3Pi(O+) State of Bromine Monochloride.

DTIC Science & Technology

1986-08-01

many useful discussions on energy transfer studies and continual friendship, to Lt. Brian McFeeters for execution of an RKR program, and to AFWL...2 C. The Halogens and Interhalogens.................... 6 D. The Study of Molecular Energy Transfer............ 9 E. Problem...Matrix.............. 137 8. The BrCl(B) Quenching Mechanism................ 144 9. Energy Transfer with Rare Gases................ 145 10. Summary of

40 CFR 63.7325 - What test methods and other procedures must I use to demonstrate initial compliance with the TDS...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 13 2011-07-01 2011-07-01 false What test methods and other procedures must I use to demonstrate initial compliance with the TDS or constituent limits for quench water? 63.7325 Section 63.7325 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR...

Spontaneous magnetic order in complex materials: Role of longitudinal spin-orbit interactions

NASA Astrophysics Data System (ADS)

Chakraborty, Subrata; Vijay, Amrendra

2017-06-01

We show that the longitudinal spin-orbit interactions (SOI) critically determine the fate of spontaneous magnetic order (SMO) in complex materials. To study the magnetic response of interacting electrons constituting the material, we implement an extension of the Hubbard model that faithfully accounts for the SOI. Next, we use the double-time Green functions of quantum statistical mechanics to obtain the spontaneous magnetization, Msp , and thence ascertain the possibility of SMO. For materials with quenched SOI, in an arbitrary dimension, Msp vanishes at finite temperatures, implying the presence of the disordered (paramagnetic) phase. This is consistent with and goes beyond the Bogolyubov's inequality based analysis in one and two dimensions. In the presence of longitudinal SOI, Msp , for materials in an arbitrary dimension, remains non-zero at finite temperatures, which indicates the existence of the ordered (ferromagnetic) phase. As a plausible experimental evidence of the present SOI-based phenomenology, we discuss, inter alia, a recent experimental study on Y4Mn1-xGa12-yGey, an intermetallic compound, which exhibits a magnetic phase transition (paramagnetic to ferromagnetic) upon tuning the fraction of Ge atoms and thence the vacancies of the magnetic centers in this system. The availability of Ge atoms to form a direct chemical bond with octahedral Mn in this material appears to quench the SOI and, as a consequence, favours the formation of the disordered (paramagnetic) phase.

Dynamics of a quantum phase transition in the Bose-Hubbard model: Kibble-Zurek mechanism and beyond

NASA Astrophysics Data System (ADS)

Shimizu, Keita; Kuno, Yoshihito; Hirano, Takahiro; Ichinose, Ikuo

2018-03-01

In this paper, we study the dynamics of the Bose-Hubbard model by using time-dependent Gutzwiller methods. In particular, we vary the parameters in the Hamiltonian as a function of time, and investigate the temporal behavior of the system from the Mott insulator to the superfluid (SF) crossing a second-order phase transition. We first solve a time-dependent Schrödinger equation for the experimental setup recently done by Braun et al. [Proc. Natl. Acad. Sci. USA 112, 3641 (2015)] and show that the numerical and experimental results are in fairly good agreement. However, these results disagree with the Kibble-Zurek scaling. From our numerical study, we reveal a possible source of the discrepancy. Next, we calculate the critical exponents of the correlation length and vortex density in addition to the SF order parameter for a Kibble-Zurek protocol. We show that beside the "freeze" time t ̂, there exists another important time, teq, at which an oscillating behavior of the SF amplitude starts. From calculations of the exponents of the correlation length and vortex density with respect to a quench time τQ, we obtain a physical picture of a coarsening process. Finally, we study how the system evolves after the quench. We give a global picture of dynamics of the Bose-Hubbard model.

Crack deflection: Implications for the growth of long and short fatigue cracks

NASA Astrophysics Data System (ADS)

Suresh, S.

1983-11-01

The influences of crack deflection on the growth rates of nominally Mode I fatigue cracks are examined. Previous theoretical analyses of stress intensity solutions for kinked elastic cracks are reviewed. Simple elastic deflection models are developed to estimate the growth rates of nonlinear fatigue cracks subjected to various degrees of deflection, by incorporating changes in the effective driving force and in the apparent propagation rates. Experimental data are presented for intermediate-quenched and step-quenched conditions of Fe/2Si/0.1C ferrite-martensite dual phase steel, where variations in crack morphology alone influence considerably the fatigue crack propagation rates and threshold stress intensity range values. Such results are found to be in good quantitative agreement with the deflection model predictions of propagation rates for nonlinear cracks. Experimental information on crack deflection, induced by variable amplitude loading, is also provided for 2020-T651 aluminum alloy. It is demonstrated with the aid of elastic analyses and experiments that crack deflection models offer a physically-appealing rationale for the apparently slower growth rates of long fatigue cracks subjected to constant and variable amplitude loading and for the apparent deceleration and/or arrest of short cracks. The changes in the propagation rates of deflected fatigue cracks are discussed in terms of the local mode of crack advance, microstructure, effective driving force, growth mechanisms, mean stress, slip characteristics, and crack closure.

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.

Overview of NASA's Microgravity Materials Research Program

NASA Technical Reports Server (NTRS)

Downey, James Patton; Grugel, Richard

2012-01-01

The NASA microgravity materials program is dedicated to conducting microgravity experiments and related modeling efforts that will help us understand the processes associated with the formation of materials. This knowledge will help improve ground based industrial production of such materials. The currently funded investigations include research on the distribution of dopants and formation of defects in semiconductors, transitions between columnar and dendritic grain morphology, coarsening of phase boundaries, competition between thermally and kinetically favored phases, and the formation of glassy vs. crystalline material. NASA microgravity materials science investigators are selected for funding either through a proposal in response to a NASA Research Announcement or by participation in a team proposing to a foreign agency research announcement. In the latter case, a US investigator participating in a successful proposal to a foreign agency can then apply to NASA for funding of an unsolicited proposal. The program relies on cooperation with other aerospace partners from around the world. The ISS facilities used for these investigations are provided primarily by partnering with foreign agencies and in most cases the US investigators are working as a part of a larger team studying a specific area of materials science. The following facilities are to be utilized for the initial investigations. The ESA provided Low Gradient Facility and the Solidification and Quench Inserts to the Materials Research Rack/Materials Science Laboratory are to be used primarily for creating bulk samples that are directionally solidified or quenched from a high temperature melt. The CNES provided DECLIC facility is used to observe morphological development in transparent materials. The ESA provided Electro-Magnetic Levitator (EML) is designed to levitate, melt and then cool samples in order to study nucleation behavior. The facility provides conditions in which nucleation of the solid is not triggered from the wall and in which fluid flows in the sample can be controlled and manipulated. These conditions allow scientists ideal conditions for understanding the relative amounts and distribution of different phases that form in the solid. Finally, the Coarsening of Solid Liquid Melts hardware allows quenching of low temperature samples in the Microgravity Science Glovebox.

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.

Mechanism of curcumin-induced trypsin inhibition: Computational and experimental studies

NASA Astrophysics Data System (ADS)

Wang, Yan-Qing; Zhang, Hong-Mei; Kang, Yi-Jun; Gu, Yun-Lan; Cao, Jian

2016-03-01

In the present study, the experimental and theoretical methods were used to analyze the binding interaction of food dye, curcumin with trypsin. The results of fluorescence spectroscopic measurements indicated that curcumin binding resulted in the obviously intrinsic fluorescence quenching with the increase concentration of curcumin. This binding interaction is a spontaneous process with the estimated enthalpy and entropy changes being -15.70 kJ mol-1 and 40.25 J mol-1 K-1, respectively. Hydrogen bonds and hydrophobic forces played an important role in the complex formation between curcumin and trypsin. Moreover, curcumin could enter into the primary substrate-binding pocket and makes the activity of trypsin decrease remarkably with the increasing concentration of curcumin.

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.

Formation of anisotropic hollow-fiber membranes via thermally induced phase separation

NASA Astrophysics Data System (ADS)

Batarseh, Melanie Turkett

The goal of this research project was to study the formation of anisotropic hollow fiber membranes via thermally induced phase separation (TIPS). This objective included developing a fundamental knowledge of the factors that contribute to anisotropy and studying how anisotropy can be controlled via operational parameters in hollow fiber spinning. The objective was met by creating a model to simulate the mass and heat transfer in the fiber wall during spinning and by experimentally varying spinning parameters and observing the affect on the membrane microstructure. The TIPS membrane formation process consists of forming a homogeneous solution of polymer and diluent and extruding the solution through a spinneret to form a hollow fiber. The fiber is cooled in an air gap followed by a quench bath, which results in phase separation of the solution into a diluent-rich phase dispersed in a continuous polymer-rich liquid phase. The diluent-rich domains grow in size until the polymer-rich phase crystallizes. Then the diluent is removed, and the spaces left behind become the pores of the microporous membrane. Therefore, the size of the diluent-rich domains when the polymer solidifies is related to the size of the pores in the finished membrane. Increasing the polymer concentration of the homogeneous solution or increasing the cooling rate of the phase separated solution decreases the domain size, and thus decreases pore size. An anisotropic membrane, which has a gradation of pore size from small pores at the feed-side to large pores at the permeate-side, can be formed by creating a concentration gradient or a cooling rate gradient across the membrane. In hollow fiber spinning, a concentration gradient can be created by allowing diluent to evaporate from the outside wall of the fiber in the air gap, and a cooling rate gradient can be created by quenching the fiber in a liquid bath. The spinning model calculates concentration and temperature profiles across the hollow fiber wall over time. The model results indicate that spinning temperature, air velocity, and air gap length have a significant effect on the concentration profile in the wall, and spinning temperature and quench temperature have a significant effect on the cooling rate profile. Experimental results indicate that increasing the air gap length from 5 to 50 cm. or increasing the quench temperature from 298 to 323 K has a significant effect on the anisotropic structure of the hollow fiber.

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...

Quenching and ram pressure stripping of simulated Milky Way satellite galaxies

NASA Astrophysics Data System (ADS)

Simpson, Christine; Grand, Robert; Gomez, Facundo; Marinacci, Federico; Pakmor, Rüdiger; Springel, Volker; Campbell, David; Frenk, Carlos; Auriga Project, Virgo Consortium

2018-01-01

We present predictions for the quenching of star formation in satellite galaxies of the Local Group from a suite of 30 cosmological zoom simulations of Milky Way-like host galaxies. The Auriga simulations resolve satellites down to the luminosity of the classical dwarf spheroidal galaxies of the Milky Way. We find strong mass-dependent and distance-dependent quenching signals, where dwarf systems beyond 600 kpc are only strongly quenched below a stellar mass of 107 M⊙. Ram pressure stripping appears to be the dominant quenching mechanism and 50% of quenched systems cease star formation within 1 Gyr of first infall. We demonstrate that systems within a host galaxy's R200 radius are comprised of two populations: (i) a first infall population that has entered the host halo within the past few Gyrs and (ii) a population of returning `backsplash' systems that have had a much more extended interaction with the host. Backsplash galaxies that do not return to the host galaxy by redshift zero exhibit quenching properties similar to galaxies within R200 and are distinct from other external systems. The simulated quenching trend with stellar mass has some tension with observations, but our simulations are able reproduce the range of quenching times measured from resolved stellar populations of Local Group dwarf galaxies.

Quenching and ram pressure stripping of simulated Milky Way satellite galaxies

NASA Astrophysics Data System (ADS)

Simpson, Christine M.; Grand, Robert J. J.; Gómez, Facundo A.; Marinacci, Federico; Pakmor, Rüdiger; Springel, Volker; Campbell, David J. R.; Frenk, Carlos S.

2018-07-01

We present predictions for the quenching of star formation in satellite galaxies of the Local Group from a suite of 30 cosmological zoom simulations of Milky Way-like host galaxies. The Auriga simulations resolve satellites down to the luminosity of the classical dwarf spheroidal galaxies of the Milky Way. We find strong mass-dependent and distance-dependent quenching signals, where dwarf systems beyond 600 kpc are only strongly quenched below a stellar mass of 107 M⊙. Ram pressure stripping appears to be the dominant quenching mechanism and 50 per cent of quenched systems cease star formation within 1 Gyr of first infall. We demonstrate that systems within a host galaxy's R200 radius are comprised of two populations: (i) a first infall population that has entered the host halo within the past few Gyrs and (ii) a population of returning `backsplash' systems that have had a much more extended interaction with the host. Backsplash galaxies that do not return to the host galaxy by redshift zero exhibit quenching properties similar to galaxies within R200 and are distinct from other external systems. The simulated quenching trend with stellar mass has some tension with observations, but our simulations are able reproduce the range of quenching times measured from resolved stellar populations of Local Group dwarf galaxies.

Quenching and ram pressure stripping of simulated Milky Way satellite galaxies

NASA Astrophysics Data System (ADS)

Simpson, Christine M.; Grand, Robert J. J.; Gómez, Facundo A.; Marinacci, Federico; Pakmor, Rüdiger; Springel, Volker; Campbell, David J. R.; Frenk, Carlos S.

2018-03-01

We present predictions for the quenching of star formation in satellite galaxies of the Local Group from a suite of 30 cosmological zoom simulations of Milky Way-like host galaxies. The Auriga simulations resolve satellites down to the luminosity of the classical dwarf spheroidal galaxies of the Milky Way. We find strong mass-dependent and distance-dependent quenching signals, where dwarf systems beyond 600 kpc are only strongly quenched below a stellar mass of 107 M⊙. Ram pressure stripping appears to be the dominant quenching mechanism and 50% of quenched systems cease star formation within 1 Gyr of first infall. We demonstrate that systems within a host galaxy's R200 radius are comprised of two populations: (i) a first infall population that has entered the host halo within the past few Gyrs and (ii) a population of returning `backsplash' systems that have had a much more extended interaction with the host. Backsplash galaxies that do not return to the host galaxy by redshift zero exhibit quenching properties similar to galaxies within R200 and are distinct from other external systems. The simulated quenching trend with stellar mass has some tension with observations, but our simulations are able reproduce the range of quenching times measured from resolved stellar populations of Local Group dwarf galaxies.

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

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.

Saturated fluorescence measurements of the hydroxyl radical in laminar high-pressure flames

NASA Technical Reports Server (NTRS)

Carter, Campbell D.; King, Galen B.; Laurendeau, Normand M.

1990-01-01

The efficacy of laser saturated fluorescence (LSF) for OH concentration measurements in high pressure flames was studied theoretically and experimentally. Using a numerical model describing the interaction of hydroxyl with nonuniform laser excitation, the effect of pressure on the validity of the balanced cross-rate model was studied along with the sensitivity of the depopulation of the laser-coupled levels to the ratio of rate coefficients describing: (1) electronic quenching to (sup 2) Sigma (+) (v double prime greater than 0), and (2) vibrational relaxation from v double prime greater than 0 to v double prime = 0. At sufficiently high pressures and near-saturated conditions, the total population of the laser-coupled levels reaches an asymptotic value, which is insensitive to the degree of saturation. When the ratio of electronic quenching to vibrational relaxation is small and the rate of coefficients for rotational transfer in the ground and excited electronic states are nearly the same, the balanced cross-rate model remains a good approximation for all pressures. When the above ratio is large, depopulation of the laser-coupled levels becomes significant at high pressures, and thus the balanced cross-rate model no longer holds. Under these conditions, however, knowledge of the depletion of the laser-coupled levels can be used to correct the model. A combustion facility for operation up to 20 atm was developed to allow LSF measurements of OH in high pressure flames. Using this facility, partial saturation in laminar high pressure (less than or equal to 12.3 atm) C2H6/O2/N2 flames was achieved. To evaluate the limits of the balanced cross-rate model, absorption and calibrated LSF measurements at 3.1 and 6.1 atm were compared. The fluorescence voltages were calibrated with absorption measurements in an atmospheric flame and corrected for their finite sensitivity to quenching with: (1) estimated quenching rate coefficients, and (2) an in situ measurement from a technique employing two fluorescence detection geometries.

Spectrophotometric and molecular modelling studies on in vitro interaction of tyrosine kinase inhibitor linifanib with bovine serum albumin.

PubMed

Wani, Tanveer A; Bakheit, Ahmed H; Zargar, Seema; Hamidaddin, Mohammed A; Darwish, Ibrahim A

2017-01-01

Linifanib (LNF) possess antitumor activity and acts by inhibiting receptor tyrosine kinase VEGF and PDGF. The interaction of BSA with the drug can provide valuable information regarding the pharmacokinetic and pharmacodynamics behavior of drug. In our study the spectrophotometric methods and molecular docking studies were executed to understand the interaction behavior of BSA and LNF. BSA has an intrinsic fluorescence and that fluorescence was quenched by LNF. This quenching process was studied at three different temperatures of 288, 300and 308 K. The interaction between LNF and BSA was due to static quenching because the Ksv (Stern-Volmer constant) at 288 K was higher than at 300 and 308 K. Kq (quenching rate constant) behaved in a similar fashion as the Ksv. Several other parameters like binding constants, number of binding sites and binding energy in addition to molecular docking studies were also used to evaluate the interaction process. A decrease in the binding constants was observed with increasing temperatures and the binding site number approximated unity. The decreasing binding constant indicates LNF-BSA complex stability. The site mark competition experiment confirmed the binding site for LNF was located on site II of BSA. UV-visible studies along with synchronous fluorescence confirm a small change in the conformation of BSA upon interaction with LNF. The thermodynamic analysis provided the values for free energy ΔG0, ΔH0 and ΔS0. The ΔG0 at the 288, 300 and 308 K ranged in between -21.5 to -23.3 kJ mol-1, whereas the calculated values of ΔH (-55.91 kJ mol-1) and ΔS0 (-111.74 J mol-1·K-1). The experimental and molecular docking results suggest that the interaction between LNF and BSA was spontaneous and they exhibited hydrogen bonding and van der Waals force between them.

Modeling of the Reaction Mechanism of Enzymatic Radical C–C Coupling by Benzylsuccinate Synthase

PubMed Central

Szaleniec, Maciej; Heider, Johann

2016-01-01

Molecular modeling techniques and density functional theory calculations were performed to study the mechanism of enzymatic radical C–C coupling catalyzed by benzylsuccinate synthase (BSS). BSS has been identified as a glycyl radical enzyme that catalyzes the enantiospecific fumarate addition to toluene initiating its anaerobic metabolism in the denitrifying bacterium Thauera aromatica, and this reaction represents the general mechanism of toluene degradation in all known anaerobic degraders. In this work docking calculations, classical molecular dynamics (MD) simulations, and DFT+D2 cluster modeling was employed to address the following questions: (i) What mechanistic details of the BSS reaction yield the most probable molecular model? (ii) What is the molecular basis of enantiospecificity of BSS? (iii) Is the proposed mechanism consistent with experimental observations, such as an inversion of the stereochemistry of the benzylic protons, syn addition of toluene to fumarate, exclusive production of (R)-benzylsuccinate as a product and a kinetic isotope effect (KIE) ranging between 2 and 4? The quantum mechanics (QM) modeling confirms that the previously proposed hypothetical mechanism is the most probable among several variants considered, although C–H activation and not C–C coupling turns out to be the rate limiting step. The enantiospecificity of the enzyme seems to be enforced by a thermodynamic preference for binding of fumarate in the pro(R) orientation and reverse preference of benzyl radical attack on fumarate in pro(S) pathway which results with prohibitively high energy barrier of the radical quenching. Finally, the proposed mechanism agrees with most of the experimental observations, although the calculated intrinsic KIE from the model (6.5) is still higher than the experimentally observed values (4.0) which suggests that both C–H activation and radical quenching may jointly be involved in the kinetic control of the reaction. PMID:27070573

Carbon Solubility in Metallic Iron and Melting Relations in the Fe-C System at High Pressure and Temperature

NASA Astrophysics Data System (ADS)

Wang, Y.; Fei, Y.

2006-05-01

Carbon has been proposed to be one of the light elements in the Earth's core. Knowledge of phase relations in the Fe-C system at high pressure and temperature is needed to understand the carbon content in the core and its effect on the physical properties and the temperature of the core. Experimental data in this system at high pressure and temperature are limited. In this study we report new experimental data on melting relations up to 25 GPa. The experiments were performed using piston-cylinder and multi-anvil devices at the Geophysical Laboratory. Mixtures of fine power of pure iron and graphite with different carbon content were prepared as starting materials. The starting materials were loaded into MgO capsules and then compressed to the desired pressures, using various high-pressure cell assemblies that have been calibrated at high pressure. High temperatures were achieved using either graphite heater (<6 GPa) or rhenium heater at higher pressures and measured with a tungsten-rhenium thermocouple. Melting relations were determined with a JEOL JXA-8900 electron microprobe, based on quench textures and chemical composition of the quenched phases. Powder X- ray diffraction technique was also used to identify phases and determine unit cell parameters. A positive slope between the solubility of carbon in metallic iron and pressure was found at elevated temperatures. The eutectic temperature increases with increasing pressure. The liquidus temperature determined in this study is significantly lower than the calculated value in previous study. Our study presents directly experimental measurements of the melting relations in the Fe-C system at high pressure and temperature, which provides better constraints on composition and temperature of the Earth's core.

Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality

NASA Astrophysics Data System (ADS)

Williams, R. T.; Grim, Joel Q.; Li, Qi; Ucer, K. B.; Bizarri, G. A.; Kerisit, S.; Gao, Fei; Bhattacharya, P.; Tupitsyn, E.; Rowe, E.; Buliga, V. M.; Burger, A.

2013-09-01

Models of nonproportional response in scintillators have highlighted the importance of parameters such as branching ratios, carrier thermalization times, diffusion, kinetic order of quenching, associated rate constants, and radius of the electron track. For example, the fraction ηeh of excitations that are free carriers versus excitons was shown by Payne and coworkers to have strong correlation with the shape of electron energy response curves from Compton-coincidence studies. Rate constants for nonlinear quenching are implicit in almost all models of nonproportionality, and some assumption about track radius must invariably be made if one is to relate linear energy deposition dE/dx to volume-based excitation density n (eh/cm3) in terms of which the rates are defined. Diffusion, affecting time-dependent track radius and thus density of excitations, has been implicated as an important factor in nonlinear light yield. Several groups have recently highlighted diffusion of hot electrons in addition to thermalized carriers and excitons in scintillators. However, experimental determination of many of these parameters in the insulating crystals used as scintillators has seemed difficult. Subpicosecond laser techniques including interband z scan light yield, fluence-dependent decay time, and transient optical absorption are now yielding experimental values for some of the missing rates and ratios needed for modeling scintillator response. First principles calculations and Monte Carlo simulations can fill in additional parameters still unavailable from experiment. As a result, quantitative modeling of scintillator electron energy response from independently determined material parameters is becoming possible on an increasingly firmer data base. This paper describes recent laser experiments, calculations, and numerical modeling of scintillator response.

Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality

DOE PAGES

Williams, R. T.; Grim, Joel Q.; Li, Qi; ...

2013-09-26

Models of nonproportional response in scintillators have highlighted the importance of parameters such as branching ratios, carrier thermalization times, diffusion, kinetic order of quenching, associated rate constants, and radius of the electron track. For example, the fraction ηeh of excitations that are free carriers versus excitons was shown by Payne and coworkers to have strong correlation with the shape of electron energy response curves from Compton-coincidence studies. Rate constants for nonlinear quenching are implicit in almost all models of nonproportionality, and some assumption about track radius must invariably be made if one is to relate linear energy deposition dE/dx tomore » volume-based excitation density n (eh/cm 3) in terms of which the rates are defined. Diffusion, affecting time-dependent track radius and thus density of excitations, has been implicated as an important factor in nonlinear light yield. Several groups have recently highlighted diffusion of hot electrons in addition to thermalized carriers and excitons in scintillators. However, experimental determination of many of these parameters in the insulating crystals used as scintillators has seemed difficult. Subpicosecond laser techniques including interband z scan light yield, fluence-dependent decay time, and transient optical absorption are now yielding experimental values for some of the missing rates and ratios needed for modeling scintillator response. First principles calculations and Monte Carlo simulations can fill in additional parameters still unavailable from experiment. As a result, quantitative modeling of scintillator electron energy response from independently determined material parameters is becoming possible on an increasingly firmer data base. This study describes recent laser experiments, calculations, and numerical modeling of scintillator response.« less

Time-Resolved Magnetic Field Effects Distinguish Loose Ion Pairs from Exciplexes

PubMed Central

2013-01-01

We describe the experimental investigation of time-resolved magnetic field effects in exciplex-forming organic donor–acceptor systems. In these systems, the photoexcited acceptor state is predominantly deactivated by bimolecular electron transfer reactions (yielding radical ion pairs) or by direct exciplex formation. The delayed fluorescence emitted by the exciplex is magnetosensitive if the reaction pathway involves loose radical ion pair states. This magnetic field effect results from the coherent interconversion between the electronic singlet and triplet radical ion pair states as described by the radical pair mechanism. By monitoring the changes in the exciplex luminescence intensity when applying external magnetic fields, details of the reaction mechanism can be elucidated. In this work we present results obtained with the fluorophore-quencher pair 9,10-dimethylanthracene/N,N-dimethylaniline (DMA) in solvents of systematically varied permittivity. A simple theoretical model is introduced that allows discriminating the initial state of quenching, viz., the loose ion pair and the exciplex, based on the time-resolved magnetic field effect. The approach is validated by applying it to the isotopologous fluorophore-quencher pairs pyrene/DMA and pyrene-d10/DMA. We detect that both the exciplex and the radical ion pair are formed during the initial quenching stage. Upon increasing the solvent polarity, the relative importance of the distant electron transfer quenching increases. However, even in comparably polar media, the exciplex pathway remains remarkably significant. We discuss our results in relation to recent findings on the involvement of exciplexes in photoinduced electron transfer reactions. PMID:24041160

Insights into the binding behavior of bovine serum albumin to black carbon nanoparticles and induced cytotoxicity.

PubMed

Wu, Hai; Chen, Miaomiao; Shang, Mengting; Li, Xiang; Mu, Kui; Fan, Suhua; Jiang, Shuanglin; Li, Wenyong

2018-07-05

Black carbon (BC) is a main component of particulate matter (PM 2.5 ). Due to their small size (<100nm), inhaled ultrafine BC nanoparticles may penetrate the lung alveoli, where they interact with surfactant proteins and lipids, causing more serious damage to human health. Here, BC was analyzed to investigate the binding mechanism of its interaction with protein and induction of cytotoxicity changes. The binding process and protein conformation between BC and a serum protein (bovine serum albumin, BSA) were monitored by using a fluorescence quenching technique and UV-vis absorption, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopies. The experimental results revealed that the fluorescence quenching of BSA induced by BC was a static quenching process and the hydrophobic force played the critical role in the interaction. The native conformation of BSA on the BC surface was slightly disturbed but obvious structural unfolding of the secondary structure did not occur. In the cytotoxicity study, BC nanoparticles with low concentrations exhibited strong toxicity towards BEAS-2B cells. However, the toxicity of BC nanoparticles could be mitigated by the presence of BSA. Therefore, proteins in biological fluids likely reduce the toxic effect of BC on human health. These findings delineated the binding mechanism and the toxicity between BC and the BSA-BC system, contributing to the understanding of the biological effects of BC exposure on human health in polluted atmospheres. Copyright © 2018 Elsevier B.V. All rights reserved.

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.

Analysis of X-Ray Microradiographs of Al-Au Interface Quench Profile using Modeling of Solidification Including Double-Diffusion and Convection in the Melt

NASA Technical Reports Server (NTRS)

Bune, Andris V.; Kaukler, William

1999-01-01

Experimental data on Al-0.8Au horizontal solidification of a 1 mm thick specimen in a BN crucible shows the effect of growth rate on the solidification interface shape. For translation rates below 0.5 micron/s the interface maintains a plain and flat shape. When the translation rate is 3 to 5 micron/s or more, the interface appearance changes to two planar zones, with the zone closer to the bottom having higher inclination. The interface shapes were measured by first quenching in place during growth. X-ray microscopy shows the interface shape within the quenched sample by viewing through the side of the specimen. In order to provide theoretical explanation of the phenomena, numerical modeling was undertaken using finite element code FIDAP. Double diffusion convection in Al-0.8Au melt and crystal-melt interface curvature during directional solidification was analyzed numerically. Actual thermophysical properties of Al-0.8Au including the binary Al-Au phase diagram were used. Although convection in the sample is weak, for the slower translation rate convection and diffusion is sufficient for the redistribution of initial compositional stratification caused by gravity. When translation rate is raised, neither convection nor diffusion can provide proper mixing so that solidification temperatures differ significantly near the bottom within the bulk of the sample. As a result, the solid-liquid interface appears to have two planar zones with different inclination.

Participation of intracellular and extracellular pH changes in photosynthetic response development induced by variation potential in pumpkin seedlings.

PubMed

Sherstneva, O N; Vodeneev, V A; Katicheva, L A; Surova, L M; Sukhov, V S

2015-06-01

Electrical signals presented in plants by action potential and by variation potential (VP) can induce a reversible inactivation of photosynthesis. Changes in the intracellular and extracellular pH during VP generation are a potential mechanism of photosynthetic response induction; however, this hypothesis requires additional experimental investigation. The purpose of the present work was to analyze the influence of pH changes on induction of the photosynthetic response in pumpkin. It was shown that a burning of the cotyledon induced VP propagation into true leaves of pumpkin seedlings inducing a decrease in the photosynthetic CO2 assimilation and an increase in non-photochemical quenching of fluorescence, whereas respiration was activated insignificantly. The photosynthetic response magnitude depended linearly on the VP amplitude. The intracellular and extracellular concentrations of protons were analyzed using pH-sensitive fluorescent probes, and the VP generation was shown to be accompanied by apoplast alkalization (0.4 pH unit) and cytoplasm acidification (0.3 pH unit). The influence of changes in the incubation medium pH on the non-photochemical quenching of fluorescence of isolated chloroplasts was also investigated. It was found that acidification of the medium stimulated the non-photochemical quenching, and the magnitude of this increase depended on the decrease in pH. Our results confirm the contribution of changes in intracellular and extracellular pH to induction of the photosynthetic response caused by VP. Possible mechanisms of the influence of pH changes on photosynthesis are discussed.

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.

Analysis of fuel using the Direct LSC method determination of bio-originated fuel in the presence of quenching

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

Doll, Charles G.; Wright, Cherylyn W.; Morley, Shannon M.

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%. Analysis of highly quenched samples was possible when diluted with the exception of one sample with a 100% quenching effect.

Analysis of fuel using the Direct LSC method determination of bio-originated fuel in the presence of quenching

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

Doll, Charles G.; Wright, Cherylyn W.; Morley, Shannon M.

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.

Selective fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene by nucleotides.

PubMed

Marquez, Cesar; Pischel, Uwe; Nau, Werner M

2003-10-16

[reaction: see text] The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by nucleotides has been studied. The quenching mechanism was analyzed on the basis of deuterium isotope effects, tendencies for exciplex formation, and the quenching efficiency in the presence of a molecular container (cucurbit[7]uril). Exciplex-induced quenching appears to prevail for adenosine, cytidine, and uridine, while hydrogen abstraction becomes competitive for thymidine and guanosine. Compared to other fluorescent probes, DBO responds very selectively to the type of nucleotide.

Asymmetries in the spectral density of an interaction-quenched Luttinger liquid

NASA Astrophysics Data System (ADS)

Calzona, A.; Gambetta, F. M.; Carrega, M.; Cavaliere, F.; Sassetti, M.

2018-03-01

The spectral density of an interaction-quenched one-dimensional system is investigated. Both direct and inverse quench protocols are considered and it is found that the former leads to stronger effects on the spectral density with respect to the latter. Such asymmetry is directly reflected on transport properties of the system, namely the charge and energy current flowing to the system from a tunnel coupled biased probe. In particular, the injection of particles from the probe to the right-moving channel of the system is considered. The resulting fractionalization phenomena are strongly affected by the quench protocol and display asymmetries in the case of direct and inverse quench. Transport properties therefore emerge as natural probes for the observation of this quench-induced behavior.

Reliability of the quench protection system for the LHC superconducting elements

NASA Astrophysics Data System (ADS)

Vergara Fernández, A.; Rodríguez-Mateos, F.

2004-06-01

The Quench Protection System (QPS) is the sole system in the Large Hadron Collider machine monitoring the signals from the superconducting elements (bus bars, current leads, magnets) which form the cold part of the electrical circuits. The basic functions to be accomplished by the QPS during the machine operation will be briefly presented. With more than 4000 internal trigger channels (quench detectors and others), the final QPS design is the result of an optimised balance between on-demand availability and false quench reliability. The built-in redundancy for the different equipment will be presented, focusing on the calculated, expected number of missed quenches and false quenches. Maintenance strategies in order to improve the performance over the years of operation will be addressed.

Studies of the quenching phenomenon in delayed contact hypersensitivity reactions.

PubMed

Basketter, D A; Allenby, C F

1991-09-01

Studies in guinea pig and man have shown that eugenol can quench non-specifically contact urticarial responses, whereas limonene seems largely ineffective. In a comprehensive series of studies, there was little evidence of quenching of delayed contact hypersensitivity reactions to cinnamic aldehyde or citral, including in 'pre-quenched' material supplied by a perfume/flavour company, and in a similar mixture prepared in this laboratory, in the guinea pig model. In addition, there was no evidence of the quenching by eugenol of allergic reactions to cinnamic aldehyde in a panel of human subjects with a proven history of cinnamic-aldehyde-induced allergic contact dermatitis. Overall, the results lend little credibility to earlier literature reports of quenching phenomena in delayed contact hypersensitivity responses.

Investigation of mechanical and microstructural properties of Zircaloy-4 under different experimental conditions

DOE PAGES

Silva, Chinthaka M.; Leonard, Keith J.; Van Abel, Eric; ...

2017-12-09

Here two types of Zircaloy-4 (alpha-annealed and beta-quenched) were investigated in their different forms. It was found that mechanical properties of Zircaloy-4 are affected significantly by welding and hydrogen-charging followed by neutron irradiation. Evaluation of microstructural properties of samples showed that these changes are mainly due to the formation of secondary phases such as hydrides—mostly along grain boundaries, dislocation channeling and their disruptions, and the increase in the type dislocation loops.

Fatigue failure of hydrogen embrittled high strength steels

NASA Technical Reports Server (NTRS)

Kim, Y. G.; Aleszka, J.

1975-01-01

Results of an experimental investigation are presented concerning the fracture behavior of cathodically charged, quenched and tempered martensitic steels under cyclic load conditions. Introduction of H2 by cathodic charging reduced fatigue life by as much as 60%. It is proposed that subsurface transverse fatigue cracks nucleate simultaneously at multiple sites, such as at microcracks, voids, or inclusions. Fatigue crack growth then occurs on planes perpendicular to the major applied stress axis in the presence of the critical combination of applied external stress and hydrogen.

Microstructure and physical properties of bismuth-lead-tin ternary eutectic alloy

NASA Astrophysics Data System (ADS)

Kamal, M.; Moharram, B. M.; Farag, H.; El-Bediwi, A.; Abosheiasha, H. F.

2006-07-01

Using different experimental techniques, microstructure, electrical resistivity, attenuation coefficient, and mechanical and thermal properties of the quenched Bi-Pb-Sn ternary eutectic alloy have been investigated. From the X-ray analysis, Bi3Pb7 and Bi-Sn meta-stable phases are detected, in addition to rhombohedral bismuth and Sn body-centered tetragonal phases. This study also compared the physical properties of the Bi-Sn-Pb ternary eutectic alloys with the base binary Bi-Sn and Bi-Pb eutectic alloys.

Predissociation and collisional depopulation of the Cs/sub 2/(E) state

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

Wu, Z.; Huennekens, J.

1984-11-15

We report here an experimental study of depopulation mechanisms of the Cs/sub 2/(E) state. By combining ratios of atomic to molecular fluorescence with E state lifetimes obtained by the phase shift technique, all studied as a function of Cs density, we were able to obtain absolute values for predissociation, radiative, and collisional depopulation rates as well as the total quenching rates for the Cs/sub 2/(E) state. The results are discussed in relation to those of other experiments.

Molecular quenching and relaxation in a plasmonic tunable system

NASA Astrophysics Data System (ADS)

Baffou, Guillaume; Girard, Christian; Dujardin, Erik; Colas Des Francs, Gérard; Martin, Olivier J. F.

2008-03-01

Molecular fluorescence decay is significantly modified when the emitting molecule is located near a plasmonic structure. When the lateral sizes of such structures are reduced to nanometer-scale cross sections, they can be used to accurately control and amplify the emission rate. In this Rapid Communication, we extend Green’s dyadic method to quantitatively investigate both radiative and nonradiative decay channels experienced by a single fluorescent molecule confined in an adjustable dielectric-metal nanogap. The technique produces data in excellent agreement with current experimental work.

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.

Thermal Management Research for Power Generation. Delivery Order 0002 - Volume 2: Closed-Loop Spray Cooling of High-Power Semiconductor Lasers

DTIC Science & Technology

2002-12-01

surface temperature for a given heat flux [2]. Mudawar and Valentine conducted an experimental study of spray cooling to determine local quenching... Mudawar presented a CHF correlation with suitable dimensionless parameters that accurately predicted data for FC-72, FC-87 and water [5]. The 2...correlation by Estes and Mudawar had a strong dependence of CHF on volumetric flux and Sauter mean diameter. Sehmbey et al. developed a semiempirical

Photothermal fabrication of microscale patterned DNA hydrogels

NASA Astrophysics Data System (ADS)

Shimomura, Suguru; Nishimura, Takahiro; Ogura, Yusuke; Tanida, Jun

2018-02-01

This paper introduces a method for fabricating microscale DNA hydrogels using irradiation with patterned light. Optical fabrication allows for the flexible and tunable formation of DNA hydrogels without changing the environmental conditions. Our scheme is based on local heat generation via the photothermal effect, which is induced by light irradiation on a quenching species. We demonstrate experimentally that, depending on the power and irradiation time, light irradiation enables the creation of local microscale DNA hydrogels, while the shapes of the DNA hydrogels are controlled by the irradiation patterns.

Microstructure of the combustion zone: Thin-binder AP-polymer sandwiches

NASA Technical Reports Server (NTRS)

Price, E. W.; Panyam, R. R.; Sigman, R. K.

1980-01-01

Experimental results are summarized for systematic quench-burning tests on ammonium perchlorate-HC binder sandwiches with binder thicknesses in the range 10 - 150 microns. Tests included three binders (polysulfide, polybutadiene-acrylonitrile, and hydroxy terminated polybutadiene), and pressures from 1.4 to 14 MPa. In addition, deflagration limits were determined in terms of binder thickness and pressure. Results are discussed in terms of a qualitative theory of sandwich burning consolidated from various sources. Some aspects of the observed results are explained only speculatively.

Decarboxylative Fluorination of Aliphatic Carboxylic Acids via Photoredox Catalysis.

PubMed

Ventre, Sandrine; Petronijevic, Filip R; MacMillan, David W C

2015-05-06

The direct conversion of aliphatic carboxylic acids to the corresponding alkyl fluorides has been achieved via visible light-promoted photoredox catalysis. This operationally simple, redox-neutral fluorination method is amenable to a wide variety of carboxylic acids. Photon-induced oxidation of carboxylates leads to the formation of carboxyl radicals, which upon rapid CO2-extrusion and F(•) transfer from a fluorinating reagent yield the desired fluoroalkanes with high efficiency. Experimental evidence indicates that an oxidative quenching pathway is operable in this broadly applicable fluorination protocol.

Investigation of mechanical and microstructural properties of Zircaloy-4 under different experimental conditions

NASA Astrophysics Data System (ADS)

Silva, Chinthaka M.; Leonard, Keith J.; Van Abel, Eric; Geringer, J. Wilna; Bryan, Chris D.

2018-02-01

Two types of Zircaloy-4 (alpha-annealed and beta-quenched) were investigated in their different forms. It was found that mechanical properties of Zircaloy-4 are affected significantly by welding and hydrogen-charging followed by neutron irradiation. Evaluation of microstructural properties of samples showed that these changes are mainly due to the formation of secondary phases such as hydrides-mostly along grain boundaries, dislocation channeling and their disruptions, and the increase in the type dislocation loops.

Multi-Wavelength Photometric Identification of Quenching Galaxies in ZFOURGE

NASA Astrophysics Data System (ADS)

Forrest, Ben; Tran, Kim-Vy; ZFOURGE Collaboration

2018-01-01

In the new millennium, multi-wavelength photometric surveys of thousands of galaxies, such as SDSS, CANDELS, NMBS, and ZFOURGE have become the standard for analyzing large populations.With ongoing surveys such as DES, and upcoming programs with LSST and JWST, finding ways to leverage large amounts of data will continue to be an area of important research.Many diagnostics have been used to classify these galaxies, most notably the rest-frame UVJ color-color diagram, which splits galaxies into star-forming and quiescent populations.With the plethora of data probing wavelengths outside of the optical however, we can do better.In this talk I present a scheme for classifying galaxies with using composite SEDs that clearly reveals rare populations such as extreme emission line galaxies and post-starburst galaxies.We use a sample of ~8000 galaxies from ZFOURGE which have SNR_Ks>20, observations from 0.3-8 microns, and are at 1

Galaxy Zoo: evidence for rapid, recent quenching within a population of AGN host galaxies

NASA Astrophysics Data System (ADS)

Smethurst, R. J.; Lintott, C. J.; Simmons, B. D.; Schawinski, K.; Bamford, S. P.; Cardamone, C. N.; Kruk, S. J.; Masters, K. L.; Urry, C. M.; Willett, K. W.; Wong, O. I.

2016-12-01

We present a population study of the star formation history of 1244 Type 2 active galactic nuclei (AGN) host galaxies, compared to 6107 inactive galaxies. A Bayesian method is used to determine individual galaxy star formation histories, which are then collated to visualize the distribution for quenching and quenched galaxies within each population. We find evidence for some of the Type 2 AGN host galaxies having undergone a rapid drop in their star formation rate within the last 2 Gyr. AGN feedback is therefore important at least for this population of galaxies. This result is not seen for the quenching and quenched inactive galaxies whose star formation histories are dominated by the effects of downsizing at earlier epochs, a secondary effect for the AGN host galaxies. We show that histories of rapid quenching cannot account fully for the quenching of all the star formation in a galaxy's lifetime across the population of quenched AGN host galaxies, and that histories of slower quenching, attributed to secular (non-violent) evolution, are also key in their evolution. This is in agreement with recent results showing that both merger-driven and non-merger processes are contributing to the co-evolution of galaxies and supermassive black holes. The availability of gas in the reservoirs of a galaxy, and its ability to be replenished, appear to be the key drivers behind this co-evolution.

(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.

Minimization of Residual Stress in an Al-Cu Alloy Forged Plate by Different Heat Treatments

NASA Astrophysics Data System (ADS)

Dong, Ya-Bo; Shao, Wen-Zhu; Jiang, Jian-Tang; Zhang, Bao-You; Zhen, Liang

2015-06-01

In order to improve the balance of mechanical properties and residual stress, various quenching and aging treatments were applied to Al-Cu alloy forged plate. Residual stresses determined by the x-ray diffraction method and slitting method were compared. The surface residual stress measured by x-ray diffraction method was consistent with that measured by slitting method. The residual stress distribution of samples quenched in water with different temperatures (20, 60, 80, and 100 °C) was measured, and the results showed that the boiling water quenching results in a 91.4% reduction in residual stress magnitudes compared with cold water quenching (20 °C), but the tensile properties of samples quenched in boiling water were unacceptably low. Quenching in 80 °C water results in 75% reduction of residual stress, and the reduction of yield strength is 12.7%. The residual stress and yield strength level are considerable for the dimensional stability of aluminum alloy. Quenching samples into 30% polyalkylene glycol quenchants produced 52.2% reduction in the maximum compressive residual stress, and the reduction in yield strength is 19.7%. Moreover, the effects of uphill quenching and thermal-cold cycling on the residual stress were also investigated. Uphill quenching and thermal-cold cycling produced approximately 25-40% reduction in residual stress, while the effect on tensile properties is quite slight.

Etching-dependent fluorescence quenching of Ag-dielectric-Au three-layered nanoshells: The effect of inner Ag nanosphere

NASA Astrophysics Data System (ADS)

Zhu, Jian; Xu, Zai-jie; Weng, Guo-jun; Zhao, Jing; Li, Jian-jun; Zhao, Jun-wu

2018-07-01

In this report, Ag-dielectric-Au three-layered nanoshells with controlled inner core size were synthesized. The fluorescence emission of the rhodamine 6G (R6G) could be quenched by the three-layered nanoshells distinctly. What's more, the fluorescence quenching efficiency could be further improved by tuning the etching of inner Ag nanosphere. The maximum fluorescence quenching efficiency is obtained when the separate layer just appears between the inner Ag core and the outer Au shell. Whereas the fluorescence quenching efficiency is weakened when no gaps take place around the inner Ag core or the separate layer is too thick and greater than 13 nm. The fluorescence quenching properties of the Ag-dielectric-Au three-layered nanoshells with different initial sizes of the Ag nanoparticles are also studied. The maximum fluorescence quenching efficiency is obtained when the three-layered nanoshells are synthesized based on the Ag nanoparticles with 60 nm, which is better than others two sizes (42 and 79 nm). Thus we believe that the size of initial Ag nanospheres also greatly affects the optimized fluorescence quenching efficiency. These results about fluorescence quenching properties of Ag-dielectric-Au three-layered nanoshells present a potential for design and fabrication of fluorescence nanosensors based on tuning the geometry of the inner core and the separate layer.

Quench studies of ILC cavities

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

Eremeev, Grigory; Geng, Rongli; Palczewski, Ari

2011-07-01

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

Binding of caffeine with caffeic acid and chlorogenic acid using fluorescence quenching, UV/vis and FTIR spectroscopic techniques.

PubMed

Belay, Abebe; Kim, Hyung Kook; Hwang, Yoon-Hwae

2016-03-01

The interactions of caffeine (CF) with chlorogenic acid (CGA) and caffeic acid (CFA) were investigated by fluorescence quenching, UV/vis and Fourier transform infrared (FTIR) spectroscopic techniques. The results of the study indicated that the fluorescence quenching between caffeine and hydroxycinnamic acids could be rationalized in terms of static quenching or the formation of non-fluorescent CF-CFA and CF-CGA complexes. From fluorescence quenching spectral analysis, the quenching constant (KSV), quenching rate constant (kq), number of binding sites (n), thermodynamic properties and conformational changes of the interaction were determined. The quenching constants (KSV) between CF and CGA, CFA are 1.84 × 10(4) and 1.04 × 10(4) L/mol at 298 K and their binding site n is ~ 1. Thermodynamic parameters determined using the Van't Hoff equation indicated that hydrogen bonds and van der Waal's forces have a major role in the reaction of caffeine with caffeic acid and chlorogenic acid. The 3D fluorescence, UV/vis and FTIR spectra also showed that the binding of CF with CFA and CGA induces conformational changes in CFA and CGA. Copyright © 2015 John Wiley & Sons, Ltd.

Fluorescence properties of 3-amino phenylboronic acid and its interaction with glucose and ZnS:Cu quantum dots.

PubMed

Kur-Kowalska, Karolina; Przybyt, Małgorzata; Ziółczyk, Paulina; Sowiński, Przemysław; Miller, Ewa

2014-08-14

Preliminary results of a study of the interaction between 3-amino phenylboronic acid and glucose or ZnS:Cu quantum dots are presented in this paper. ZnS:Cu quantum dots with mercaptopropionic acid as a capping agent were obtained and characterized. Quenching of 3-amino phenylboronic acid fluorescence was studied by steady-state and timeresolved measurements. For fluorescence quenching with glucose the results of steady-state measurements fulfill Stern-Volmer equation. The quenching constants are increasing with growing pH. The decay of fluorescence is monoexponential with lifetime about 8.4 ns, which does not depend on pH and glucose concentration indicating static quenching. The quenching constant can be interpreted as apparent equilibrium constant of estrification of boronic group with diol. Quantum dots are also quenching 3-amino phenylboronic acid fluorescence. Fluorescence lifetime, in this case, is slightly decreasing with increasing concentration of quantum dots. The quenching constants are increasing slightly with pH's growth. Quenching mechanism of 3-amino phenylboronic acid fluorescence by quantum dots needs further experiments to be fully explained. Copyright © 2014 Elsevier B.V. All rights reserved.

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

Classical vs. evolved quenching parameters and procedures in scintillation measurements: The importance of ionization quenching

NASA Astrophysics Data System (ADS)

Bagán, H.; Tarancón, A.; Rauret, G.; García, J. F.

2008-07-01

The quenching parameters used to model detection efficiency variations in scintillation measurements have not evolved since the decade of 1970s. Meanwhile, computer capabilities have increased enormously and ionization quenching has appeared in practical measurements using plastic scintillation. This study compares the results obtained in activity quantification by plastic scintillation of 14C samples that contain colour and ionization quenchers, using classical (SIS, SCR-limited, SCR-non-limited, SIS(ext), SQP(E)) and evolved (MWA-SCR and WDW) parameters and following three calibration approaches: single step, which does not take into account the quenching mechanism; two steps, which takes into account the quenching phenomena; and multivariate calibration. Two-step calibration (ionization followed by colour) yielded the lowest relative errors, which means that each quenching phenomenon must be specifically modelled. In addition, the sample activity was quantified more accurately when the evolved parameters were used. Multivariate calibration-PLS also yielded better results than those obtained using classical parameters, which confirms that the quenching phenomena must be taken into account. The detection limits for each calibration method and each parameter were close to those obtained theoretically using the Currie approach.

Optimization of the quenching method for metabolomics analysis of Lactobacillus bulgaricus.

PubMed

Chen, Ming-ming; Li, Ai-li; Sun, Mao-cheng; Feng, Zhen; Meng, Xiang-chen; Wang, Ying

2014-04-01

This study proposed a quenching protocol for metabolite analysis of Lactobacillus delbrueckii subsp. bulgaricus. Microbial cells were quenched with 60% methanol/water, 80% methanol/glycerol, or 80% methanol/water. The effect of the quenching process was assessed by the optical density (OD)-based method, flow cytometry, and gas chromatography-mass spectrometry (GC-MS). The principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were employed for metabolite identification. The results indicated that quenching with 80% methanol/water solution led to less damage to the L. bulgaricus cells, characterized by the lower relative fraction of prodium iodide (PI)-labeled cells and the higher OD recovery ratio. Through GC-MS analysis, higher levels of intracellular metabolites (including focal glutamic acid, aspartic acid, alanine, and AMP) and a lower leakage rate were detected in the sample quenched with 80% methanol/water compared with the others. In conclusion, we suggested a higher concentration of cold methanol quenching for L. bulgaricus metabolomics due to its decreasing metabolite leakage.

Optimization of the quenching method for metabolomics analysis of Lactobacillus bulgaricus *

PubMed Central

Chen, Ming-ming; Li, Ai-li; Sun, Mao-cheng; Feng, Zhen; Meng, Xiang-chen; Wang, Ying

2014-01-01

This study proposed a quenching protocol for metabolite analysis of Lactobacillus delbrueckii subsp. bulgaricus. Microbial cells were quenched with 60% methanol/water, 80% methanol/glycerol, or 80% methanol/water. The effect of the quenching process was assessed by the optical density (OD)-based method, flow cytometry, and gas chromatography-mass spectrometry (GC-MS). The principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were employed for metabolite identification. The results indicated that quenching with 80% methanol/water solution led to less damage to the L. bulgaricus cells, characterized by the lower relative fraction of prodium iodide (PI)-labeled cells and the higher OD recovery ratio. Through GC-MS analysis, higher levels of intracellular metabolites (including focal glutamic acid, aspartic acid, alanine, and AMP) and a lower leakage rate were detected in the sample quenched with 80% methanol/water compared with the others. In conclusion, we suggested a higher concentration of cold methanol quenching for L. bulgaricus metabolomics due to its decreasing metabolite leakage. PMID:24711354

Fluorescence quenching of human orosomucoid. Accessibility to drugs and small quenching agents.

PubMed Central

Friedman, M L; Schlueter, K T; Kirley, T L; Halsall, H B

1985-01-01

The fluorescence behaviour of human orosomucoid was investigated. The intrinsic fluorescence was more accessible to acrylamide than to the slightly larger succinimide, indicating limited accessibility to part of the tryptophan population. Although I- showed almost no quenching, that of Cs+ was enhanced, and suggested a region of negative charge proximal to an emitting tryptophan residue. Removal of more than 90% of sialic acid from the glycan chains led to no change in the Cs+, I-, succinimide or acrylamide quenching, indicating that the negatively charged region originates with the protein core. Quenching as a function of pH and temperature supported this view. The binding of chlorpromazine monitored by fluorescence quenching, in the presence and in the absence of the small quenching probes (above), led to a model of its binding domain on orosomucoid that includes two tryptophan residues relatively shielded from the bulk solvent, with the third tryptophan residue being on the periphery of the domain, or affected allotopically and near the negatively charged field. PMID:4091825

Distance-dependent Fluorescence Quenching and Binding of CdSe Quantum Dots by Functionalized Nitroxide Radicals

PubMed Central

Tansakul, Chittreeya; Lilie, Erin; Walter, Eric D.; Rivera, Frank; Wolcott, Abraham; Zhang, Jin Z.; Millhauser, Glenn L.

2010-01-01

Quantum dot (QD) fluorescence is effectively quenched at low concentration by nitroxides bearing amine or carboxylic acid ligands. The association constants and fluorescence quenching of CdSe QDs with these derivatized nitroxides have been examined using electron paramagnetic resonance (EPR) and fluorescence spectroscopy. The EPR spectra in the non-protic solvent toluene are extremely sensitive to intermolecular and intramolecular hydrogen bonding of the functionalized nitroxides. Fluorescence measurements show that quenching of QD luminescence is nonlinear, with a strong dependence on the distance between the radical and the QD. The quenched fluorescence is restored when the surface-bound nitroxides are converted to hydroxylamines by mild reducing agents, or trapped by carbon radicals to form alkoxyamines. EPR studies indicate that photoreduction of the nitroxide occurs in toluene solution upon photoexcitation at 365 nm. However, photolysis in benzene solution gives no photoreduction, suggesting that photoreduction in toluene is independent of the quenching mechanism. The fluorescence quenching of QDs by nitroxide binding is a reversible process. PMID:20473339

Entanglement growth after a global quench in free scalar field theory

DOE PAGES

Cotler, Jordan S.; Hertzberg, Mark P.; Mezei, Márk; ...

2016-11-28

We compute the entanglement and Rényi entropy growth after a global quench in various dimensions in free scalar field theory. We study two types of quenches: a boundary state quench and a global mass quench. Both of these quenches are investigated for a strip geometry in 1, 2, and 3 spatial dimensions, and for a spherical geometry in 2 and 3 spatial dimensions. We compare the numerical results for massless free scalars in these geometries with the predictions of the analytical quasiparticle model based on EPR pairs, and find excellent agreement in the limit of large region sizes. As amore » result, at subleading order in the region size, we observe an anomalous logarithmic growth of entanglement coming from the zero mode of the scalar.« less

Entanglement growth after a global quench in free scalar field theory

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

Cotler, Jordan S.; Hertzberg, Mark P.; Mezei, Márk

We compute the entanglement and Rényi entropy growth after a global quench in various dimensions in free scalar field theory. We study two types of quenches: a boundary state quench and a global mass quench. Both of these quenches are investigated for a strip geometry in 1, 2, and 3 spatial dimensions, and for a spherical geometry in 2 and 3 spatial dimensions. We compare the numerical results for massless free scalars in these geometries with the predictions of the analytical quasiparticle model based on EPR pairs, and find excellent agreement in the limit of large region sizes. As amore » result, at subleading order in the region size, we observe an anomalous logarithmic growth of entanglement coming from the zero mode of the scalar.« less

Hybridization-based biosensor containing hairpin probes and use thereof

DOEpatents

Miller, Benjamin L.; Strohsahl, Christopher M.

2010-10-12

A sensor chip that includes: a fluorescence quenching surface; a nucleic acid probe that contains first and second ends with the first end bound to the fluorescence quenching surface, and is characterized by being able to self-anneal into a hairpin conformation; and a first fluorophore bound to the second end of the first nucleic acid molecule. When the first nucleic acid molecule is in the hairpin conformation, the fluorescence quenching surface substantially quenches fluorescent emissions by the first fluorophore; and when the first nucleic acid molecule is in a non-hairpin conformation, fluorescent emissions by the fluorophore are substantially free of quenching by the fluorescence quenching surface. Various nucleic acid probes, methods of making the sensor chip, biological sensor devices that contain the sensor chip, and their methods of use are also disclosed.

Methods for the evaluation of quench temperature profiles and their application for LHC superconducting short dipole magnets

NASA Astrophysics Data System (ADS)

Sanfilippo, S.; Siemko, A.

2000-08-01

This paper presents a study of the thermal effects on quench performance for several large Hadron collider (LHC) single aperture short dipole models. The analysis is based on the temperature profile in a superconducting magnet evaluated after a quench. Peak temperatures and temperature gradients in the magnet coil are estimated for different thicknesses of insulation layer between the quench heaters and the coil and different powering and protection parameters. The results show clear correlation between the thermo-mechanical response of the magnet and quench performance. They also display that the optimisation of the position of quench heaters can reduce the decrease of training performance caused by the coexistence of a mechanical weak region and of a local temperature rise.

F4TCNQ-Induced Exciton Quenching Studied by Using in-situ Photoluminescence Measurements

NASA Astrophysics Data System (ADS)

Zhu, Jian; Lu, Min; Wu, Bo; Hou, Xiao-Yuan

2012-09-01

The role of F4TCNQ as an exciton quenching material in thin organic light-emitting films is investigated by means of in situ photoluminescence measurements. C60 was used as another quenching material in the experiment for comparison, with Alq3 as a common organic light-emitting material. The effect of the growth sequence of the materials on quenching was also examined. It is found that the radius of Förster energy transfer between F4TCNQ and Alq3 is close to 0 nm and Dexter energy transfer dominates in the quenching process.

Analysis of fuel using the Direct LSC method determination of bio-originated fuel in the presence of quenching.

PubMed

Doll, Charles G; Wright, Cherylyn W; Morley, Shannon M; Wright, Bob W

2017-04-01

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%. Analysis of highly quenched samples was possible when diluted with the exception of one sample with a 100% quenching effect. Copyright © 2017. Published by Elsevier Ltd.

Interaction of Human Hemoglobin with Methotrexate

NASA Astrophysics Data System (ADS)

Zaharia, M.; Gradinaru, R.

2015-05-01

This study focuses on the interaction between methotrexate and human hemoglobin using steady-state ultraviolet-visible and fluorescence quenching methods. Fluorescence quenching was found to be valuable in assessing drug binding to hemoglobin. The quenching of methotrexate is slightly smaller than the quenching observed with related analogs (dihydrofolate and tetrahydrofolate). The quenching studies were performed at four different temperatures and various pH values. The number of binding sites for tryptophan is ~1. Parameter-dependent assays revealed that electrostatic forces play an essential role in the methotrexate-hemoglobin interaction. Furthermore, the complex was easily eluted using gel filtration chromatography.

40 CFR 63.7325 - What test methods and other procedures must I use to demonstrate initial compliance with the TDS...

Code of Federal Regulations, 2014 CFR

2014-07-01

...) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and Battery... applied to the coke (e.g., from the header that feeds water to the quench tower reservoirs). Conduct... sample of the quench water as applied to the coke (e.g., from the header that feeds water to the quench...

40 CFR 63.7325 - What test methods and other procedures must I use to demonstrate initial compliance with the TDS...

Code of Federal Regulations, 2012 CFR

2012-07-01

...) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and Battery... applied to the coke (e.g., from the header that feeds water to the quench tower reservoirs). Conduct... sample of the quench water as applied to the coke (e.g., from the header that feeds water to the quench...

40 CFR 63.7325 - What test methods and other procedures must I use to demonstrate initial compliance with the TDS...

Code of Federal Regulations, 2013 CFR

2013-07-01

...) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and Battery... applied to the coke (e.g., from the header that feeds water to the quench tower reservoirs). Conduct... sample of the quench water as applied to the coke (e.g., from the header that feeds water to the quench...

40 CFR 63.7325 - What test methods and other procedures must I use to demonstrate initial compliance with the TDS...

Code of Federal Regulations, 2010 CFR

2010-07-01

...) National Emission Standards for Hazardous Air Pollutants for Coke Ovens: Pushing, Quenching, and Battery... applied to the coke (e.g., from the header that feeds water to the quench tower reservoirs). Conduct... sample of the quench water as applied to the coke (e.g., from the header that feeds water to the quench...

HST-WFC3 Near-Infrared Spectroscopy of Quenched Galaxies at zeta approx 1.5 from the WISP Survey: Stellar Populations Properties

NASA Technical Reports Server (NTRS)

Bedregal, A. G.; Scarlata, C.; Henry, A. L.; Atek, H.; Rafelski, M.; Teplitz, H. I.; Dominguez, A.; Siana, B.; Colbert, J. W.; Malkan, M.;

HST/WFC3 near-infrared spectroscopy of quenched galaxies at z ∼ 1.5 from the WISP survey: Stellar population properties

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

Bedregal, A. G.; Scarlata, C.; Rutkowski, M. J.

We combine Hubble Space Telescope (HST) G102 and G141 near-IR (NIR) grism spectroscopy with HST/WFC3-UVIS, HST/WFC3-IR, and Spitzer/IRAC [3.6 μm] photometry to assemble a sample of massive (log (M {sub star}/M {sub ☉}) ∼ 11.0) and quenched (specific star formation rate <0.01 Gyr{sup –1}) galaxies at z ∼ 1.5. Our sample of 41 galaxies is the largest with G102+G141 NIR spectroscopy for quenched sources at these redshifts. In contrast to the local universe, z ∼ 1.5 quenched galaxies in the high-mass range have a wide range of stellar population properties. We find that their spectral energy distributions (SEDs) are wellmore » fitted with exponentially decreasing star formation histories and short star formation timescales (τ ≤ 100 Myr). Quenched galaxies also show a wide distribution in ages, between 1 and 4 Gyr. In the (u – r){sub 0}-versus-mass space quenched galaxies have a large spread in rest-frame color at a given mass. Most quenched galaxies populate the z ∼ 1.5 red sequence (RS), but an important fraction of them (32%) have substantially bluer colors. Although with a large spread, we find that the quenched galaxies on the RS have older median ages (3.1 Gyr) than the quenched galaxies off the RS (1.5 Gyr). We also show that a rejuvenated SED cannot reproduce the observed stacked spectra of (the bluer) quenched galaxies off the RS. We derive the upper limit on the fraction of massive galaxies on the RS at z ∼ 1.5 to be <43%. We speculate that the young quenched galaxies off the RS are in a transition phase between vigorous star formation at z > 2 and the z ∼ 1.5 RS. According to their estimated ages, the time required for quenched galaxies off the RS to join their counterparts on the z ∼ 1.5 RS is of the order of ∼1 Gyr.« less

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.

ITER Side Correction Coil Quench model and analysis

NASA Astrophysics Data System (ADS)

Nicollet, S.; Bessette, D.; Ciazynski, D.; Duchateau, J. L.; Gauthier, F.; Lacroix, B.

2016-12-01

Previous thermohydraulic studies performed for the ITER TF, CS and PF magnet systems have brought some important information on the detection and consequences of a quench as a function of the initial conditions (deposited energy, heated length). Even if the temperature margin of the Correction Coils is high, their behavior during a quench should also be studied since a quench is likely to be triggered by potential anomalies in joints, ground fault on the instrumentation wires, etc. A model has been developed with the SuperMagnet Code (Bagnasco et al., 2010) for a Side Correction Coil (SCC2) with four pancakes cooled in parallel, each of them represented by a Thea module (with the proper Cable In Conduit Conductor characteristics). All the other coils of the PF cooling loop are hydraulically connected in parallel (top/bottom correction coils and six Poloidal Field Coils) are modeled by Flower modules with equivalent hydraulics properties. The model and the analysis results are presented for five quench initiation cases with/without fast discharge: two quenches initiated by a heat input to the innermost turn of one pancake (case 1 and case 2) and two other quenches initiated at the innermost turns of four pancakes (case 3 and case 4). In the 5th case, the quench is initiated at the middle turn of one pancake. The impact on the cooling circuit, e.g. the exceedance of the opening pressure of the quench relief valves, is detailed in case of an undetected quench (i.e. no discharge of the magnet). Particular attention is also paid to a possible secondary quench detection system based on measured thermohydraulic signals (pressure, temperature and/or helium mass flow rate). The maximum cable temperature achieved in case of a fast current discharge (primary detection by voltage) is compared to the design hot spot criterion of 150 K, which includes the contribution of helium and jacket.

Quartz and feldspar glasses produced by natural and experimental shock.

NASA Technical Reports Server (NTRS)

Stoeffler, D.; Hornemann, U.

1972-01-01

Refractive index, density, and infrared absorption studies of naturally and experimentally shocked-produced glasses formed from quartz, plagioclase, and alkali-feldspar confirm the existence of two main groups of amorphous forms of the framework silicates: solid-state and liquid-state glasses. These were apparently formed as metastable release products of high-pressure-phases above and below the glass transition temperatures. Solid-state glasses exhibit a series of structural states with increasing disorder caused by increasing shock pressures and temperatures. They gradually merge into the structural state of fused minerals similar to that of synthetic glasses quenched from a melt. Shock-fused alkali feldspars can, however, be distinguished from their laboratory-fused counterparts by infrared absorption and by higher density.

Förster resonance energy transfer: Role of diffusion of fluorophore orientation and separation in observed shifts of FRET efficiency

DOE PAGES

Wallace, Bram; Atzberger, Paul J.; D’Auria, Sabato

2017-05-19

Forster resonance energy transfer (FRET) is a widely used single-molecule technique for measuring nanoscale distances from changes in the non-radiative transfer of energy between donor and acceptor fluorophores. For macromolecules and complexes this observed transfer efficiency is used to infer changes in molecular conformation under differing experimental conditions. But, sometimes shifts are observed in the FRET efficiency even when there is strong experimental evidence that the molecular conformational state is unchanged. Here, we investigate ways in which such discrepancies can arise from kinetic effects. We show that significant shifts can arise from the interplay between excitation kinetics, orientation diffusion ofmore » fluorophores, separation diffusion of fluorophores, and non-emitting quenching.« less

Experimental investigation of cooling perimeter and disturbance length effect on stability of Nb3Sn cable-in-conduit conductors

NASA Astrophysics Data System (ADS)

Armstrong, J. R.

1992-02-01

The stability of three coils, with similar parameters besides having differing strand diameters, was investigated experimentally using inductive heaters to input disturbances. One of the coils stability was also tested by doubling the inductive heated disturbance length to 10 cm. By computationally deriving approximate inductive heater input energy at 12 T, stability curves show fair agreement with zero-dimensional and one-dimensional computer predictions. Quench velocity and limiting currents also show good agreement with earlier work. Also, the stability measured on one of the coils below its limiting current by disturbing a 10 cm length of conductor was much less than the same samples stability using a 5 cm disturbance length.

Effect of a High Magnetic Field on γ' Phase for Ni-Based Single Crystal Superalloy During Directional Solidification

NASA Astrophysics Data System (ADS)

Xuan, Weidong; Lan, Jian; Zhao, Dengke; Li, Chuanjun; Shang, Xingfu; Zhong, Yunbo; Li, Xi; Ren, Zhongming

2018-05-01

The effect of a high magnetic field on the γ' phase of Ni-based single crystal superalloy during directional solidification is investigated experimentally. The results clearly indicate that the magnetic field significantly reduces the γ' phase size. Further, the quenching experiment is carried out, and the results found that the length of mushy zone is obviously decreased under a high magnetic field. Based on both experimental results and nucleation mechanism, it is found that the decrease of γ' phase size should be attributed to the fact that a high magnetic field causes the increase of temperature gradient in front of solid/liquid interface and leads to the increase of undercooling of γ' phase.

Förster resonance energy transfer: Role of diffusion of fluorophore orientation and separation in observed shifts of FRET efficiency

PubMed Central

Wallace, Bram

2017-01-01

Förster resonance energy transfer (FRET) is a widely used single-molecule technique for measuring nanoscale distances from changes in the non-radiative transfer of energy between donor and acceptor fluorophores. For macromolecules and complexes this observed transfer efficiency is used to infer changes in molecular conformation under differing experimental conditions. However, sometimes shifts are observed in the FRET efficiency even when there is strong experimental evidence that the molecular conformational state is unchanged. We investigate ways in which such discrepancies can arise from kinetic effects. We show that significant shifts can arise from the interplay between excitation kinetics, orientation diffusion of fluorophores, separation diffusion of fluorophores, and non-emitting quenching. PMID:28542211

Experimental investigation of the combustion products in an aluminised solid propellant

NASA Astrophysics Data System (ADS)

Liu, Zhu; Li, Shipeng; Liu, Mengying; Guan, Dian; Sui, Xin; Wang, Ningfei

2017-04-01

Aluminium is widely used as an important additive to improve ballistic and energy performance in solid propellants, but the unburned aluminium does not contribute to the specific impulse and has both thermal and momentum two-phase flow losses. So understanding of aluminium combustion behaviour during solid propellant burning is significant when improving internal ballistic performance. Recent developments and experimental results reported on such combustion behaviour are presented in this paper. A variety of experimental techniques ranging from quenching and dynamic measurement, to high-speed CCD video recording, were used to study aluminium combustion behaviour and the size distribution of the initial agglomerates. This experimental investigation also provides the size distribution of the condensed phase products. Results suggest that the addition of an organic fluoride compound to solid propellant will generate smaller diameter condensed phase products due to sublimation of AlF3. Lastly, a physico-chemical picture of the agglomeration process was also developed based on the results of high-speed CCD video analysis.

A Stellar Mass Threshold for Quenching of Field Galaxies

NASA Astrophysics Data System (ADS)

Geha, M.; Blanton, M. R.; Yan, R.; Tinker, J. L.

2012-09-01

We demonstrate that dwarf galaxies (107 < M stellar < 109 M ⊙, -12 > Mr > -18) with no active star formation are extremely rare (<0.06%) in the field. Our sample is based on the NASA-Sloan Atlas which is a reanalysis of the Sloan Digital Sky Survey Data Release 8. We examine the relative number of quenched versus star-forming dwarf galaxies, defining quenched galaxies as having no Hα emission (EWHα < 2 Å) and a strong 4000 Å break. The fraction of quenched dwarf galaxies decreases rapidly with increasing distance from a massive host, leveling off for distances beyond 1.5 Mpc. We define galaxies beyond 1.5 Mpc of a massive host galaxy to be in the field. We demonstrate that there is a stellar mass threshold of M stellar < 1.0 × 109 M ⊙ below which quenched galaxies do not exist in the field. Below this threshold, we find that none of the 2951 field dwarf galaxies are quenched; all field dwarf galaxies show evidence for recent star formation. Correcting for volume effects, this corresponds to a 1σ upper limit on the quenched fraction of 0.06%. In more dense environments, quenched galaxies account for 23% of the dwarf population over the same stellar mass range. The majority of quenched dwarf galaxies (often classified as dwarf elliptical galaxies) are within 2 virial radii of a massive galaxy, and only a few percent of quenched dwarf galaxies exist beyond 4 virial radii. Thus, for galaxies with stellar mass less than 1.0 × 109 M ⊙, ending star formation requires the presence of a more massive neighbor, providing a stringent constraint on models of star formation feedback.

Galaxies in the act of quenching star formation

NASA Astrophysics Data System (ADS)

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

2018-04-01

Detecting galaxies when their star-formation is being quenched is crucial to understand the mechanisms driving their evolution. We identify for the first time a sample of quenching galaxies selected just after the interruption of their star formation by exploiting the [O III] λ5007/Hα ratio and searching for galaxies with undetected [O III]. Using a sample of ˜174000 star-forming galaxies extracted from the SDSS-DR8 at 0.04 ≤ z < 0.21,we identify the ˜300 quenching galaxy best candidates with low [O III]/Hα, out of ˜26 000 galaxies without [O III] emission. They have masses between 10^{9.7} and 10^{10.8} M_{⊙},consistently with the corresponding growth of the quiescent population at these redshifts. Their main properties (i.e. star-formation rate, colours and metallicities) are comparable to those of the star-forming population, coherently with the hypothesis of recent quenching, but preferably reside in higher-density environments.Most candidates have morphologies similar to star-forming galaxies, suggesting that no morphological transformation has occurred yet. From a survival analysis we find a low fraction of candidates (˜ 0.58% of the star-forming population), leading to a short quenching timescale of tQ ˜ 50 Myr and an e-folding time for the quenching history of τQ ˜ 90 Myr, and their upper limits of tQ < 0.76 Gyr and τQ <1.5 Gyr, assuming as quenching galaxies 50% of objects without [O III] (˜7.5%).Our results are compatible with a 'rapid' quenching scenario of satellites galaxies due to the final phase of strangulation or ram-pressure stripping. This approach represents a robust alternative to methods used so far to select quenched galaxies (e.g. colours, specific star-formation rate, or post-starburst spectra).

Topological phase transition in the quench dynamics of a one-dimensional Fermi gas with spin-orbit coupling

NASA Astrophysics Data System (ADS)

Wang, Pei; Yi, Wei; Xianlong, Gao

2015-01-01

We study the quench dynamics of a one-dimensional ultracold Fermi gas with synthetic spin-orbit coupling. At equilibrium, the ground state of the system can undergo a topological phase transition and become a topological superfluid with Majorana edge states. As the interaction is quenched near the topological phase boundary, we identify an interesting dynamical phase transition of the quenched state in the long-time limit, characterized by an abrupt change of the pairing gap at a critical quenched interaction strength. We further demonstrate the topological nature of this dynamical phase transition from edge-state analysis of the quenched states. Our findings provide interesting clues for the understanding of topological phase transitions in dynamical processes, and can be useful for the dynamical detection of Majorana edge states in corresponding systems.

Work distributions for random sudden quantum quenches

NASA Astrophysics Data System (ADS)

Łobejko, Marcin; Łuczka, Jerzy; Talkner, Peter

2017-05-01

The statistics of work performed on a system by a sudden random quench is investigated. Considering systems with finite dimensional Hilbert spaces we model a sudden random quench by randomly choosing elements from a Gaussian unitary ensemble (GUE) consisting of Hermitian matrices with identically, Gaussian distributed matrix elements. A probability density function (pdf) of work in terms of initial and final energy distributions is derived and evaluated for a two-level system. Explicit results are obtained for quenches with a sharply given initial Hamiltonian, while the work pdfs for quenches between Hamiltonians from two independent GUEs can only be determined in explicit form in the limits of zero and infinite temperature. The same work distribution as for a sudden random quench is obtained for an adiabatic, i.e., infinitely slow, protocol connecting the same initial and final Hamiltonians.

A fluorescence study of the molecular interactions of harmane with the nucleobases, their nucleosides and mononucleotides.

PubMed

Balón, M; Muñoz, M A; Carmona, C; Guardado, P; Galán, M

1999-07-19

Fluorescence binding studies of harmane to the elemental components of the nucleic acids were undertaken to investigate the origin of the interaction between the drug and DNA. Most of the tested substrates have been found to induce hypochromism in the absorption spectrum of harmane and to quench its fluorescence. The quenching process induced by the nucleobases and their nucleosides is mainly due to the formation of ground state 1:1 complexes. However, in the case of the mononucleotides a dynamic quenching component is also observed. This quenching component is likely due to the excited state interaction of harmane with the phosphate group of the nucleotides. UV-vis spectral changes and quenching measurements have been used to quantify the ground state association constants of the complexes and the quenching rate constants.

Slow quenches in two-dimensional time-reversal symmetric Z2 topological insulators

NASA Astrophysics Data System (ADS)

Ulčakar, Lara; Mravlje, Jernej; Ramšak, Anton; Rejec, Tomaž

2018-05-01

We study the topological properties and transport in the Bernevig-Hughes-Zhang model undergoing a slow quench between different topological regimes. Due to the closing of the band gap during the quench, the system ends up in an excited state. We prove that for quenches that preserve the time-reversal symmetry, the Z2 invariant remains equal to the one evaluated in the initial state. On the other hand, the bulk spin Hall conductivity does change, and its time average approaches that of the ground state of the final Hamiltonian. The deviations from the ground-state spin Hall conductivity as a function of the quench time follow the Kibble-Zurek scaling. We also consider the breaking of the time-reversal symmetry, which restores the correspondence between the bulk invariant and the transport properties after the quench.

The enhancement of rapidly quenched galaxies in distant clusters at 0.5 < z < 1.0

NASA Astrophysics Data System (ADS)

Socolovsky, Miguel; Almaini, Omar; Hatch, Nina A.; Wild, Vivienne; Maltby, David T.; Hartley, William G.; Simpson, Chris

2018-05-01

We investigate the relationship between environment and galaxy evolution in the redshift range 0.5 < z < 1.0. Galaxy overdensities are selected using a friends-of-friends algorithm, applied to deep photometric data in the Ultra-Deep Survey field. A study of the resulting stellar mass functions reveals clear differences between cluster and field environments, with a strong excess of low-mass rapidly quenched galaxies in cluster environments compared to the field. Cluster environments also show a corresponding deficit of young, low-mass star-forming galaxies, which show a sharp radial decline towards cluster centres. By comparing mass functions and radial distributions, we conclude that young star-forming galaxies are rapidly quenched as they enter overdense environments, becoming post-starburst galaxies before joining the red sequence. Our results also point to the existence of two environmental quenching pathways operating in galaxy clusters, operating on different time-scales. Fast quenching acts on galaxies with high specific star formation rates, operating on time-scales shorter than the cluster dynamical time (<1 Gyr). In contrast, slow quenching affects galaxies with moderate specific star formation rates, regardless of their stellar mass, and acts on longer time-scales (≳ 1 Gyr). Of the cluster galaxies in the stellar mass range 9.0 < log (M/M⊙) < 10.5 quenched during this epoch, we find that 73 per cent were transformed through fast quenching, while the remaining 27 per cent followed the slow quenching route.

Predictions for boson-jet observables and fragmentation function ratios from a hybrid strong/weak coupling model for jet quenching

DOE PAGES

Casalderrey-Solana, Jorge; Gulhan, Doga Can; Milhano, José Guilherme; ...

2016-03-09

We have previously introduced a hybrid strong/weak coupling model for jet quenching in heavy ion collisions in which we describe the production and fragmentation of jets at weak coupling, using Pythia, and describe the rate at which each parton in the jet shower loses energy as it propagates through the strongly coupled plasma, dE/dx, using an expression computed holographically at strong coupling. The model has a single free parameter that we fit to a single experimental measurement. We then confront our model with experimental data on many other jet observables, focusing in this paper on boson-jet observables, finding that itmore » provides a good description of present jet data. Next, we provide the predictions of our hybrid model for many measurements to come, including those for inclusive jet, dijet, photon-jet and Z-jet observables in heavy ion collisions with energy √s = 5 : 02 ATeV coming soon at the LHC. As the statistical uncertainties on near-future measurements of photon-jet observables are expected to be much smaller than those in present data, with about an order of magnitude more photon-jet events expected, predictions for these observables are particularly important. We find that most of our pre- and post-dictions do not depend sensitively on the form we choose for the rate of energy loss dE/dx of the partons in the shower. This gives our predictions considerable robustness. To better discriminate between possible forms for the rate of energy loss, though, we must turn to intrajet observables. Here, we focus on ratios of fragmentation functions. Finally, we close with a suggestion for a particular ratio, between the fragmentation functions of inclusive and associated jets with the same kinematics in the same collisions, which is particularly sensitive to the x- and E-dependence of dE/dx, and hence may be used to learn which mechanism of parton energy loss best describes the quenching of jets.« less

Effect of instantaneous and continuous quenches on the density of vibrational modes in model glasses.

PubMed

Lerner, Edan; Bouchbinder, Eran

2017-08-01

Computational studies of supercooled liquids often focus on various analyses of their "underlying inherent states"-the glassy configurations at zero temperature obtained by an infinitely fast (instantaneous) quench from equilibrium supercooled states. Similar protocols are also regularly employed in investigations of the unjamming transition at which the rigidity of decompressed soft-sphere packings is lost. Here we investigate the statistics and localization properties of low-frequency vibrational modes of glassy configurations obtained by such instantaneous quenches. We show that the density of vibrational modes grows as ω^{β} with β depending on the parent temperature T_{0} from which the glassy configurations were instantaneously quenched. For quenches from high temperature liquid states we find β≈3, whereas β appears to approach the previously observed value β=4 as T_{0} approaches the glass transition temperature. We discuss the consistency of our findings with the theoretical framework of the soft potential model, and contrast them with similar measurements performed on configurations obtained by continuous quenches at finite cooling rates. Our results suggest that any physical quench at rates sufficiently slower than the inverse vibrational time scale-including all physically realistic quenching rates of molecular or atomistic glasses-would result in a glass whose density of vibrational modes is universally characterized by β=4.

Statistics of the Work done in a Quantum Quench

NASA Astrophysics Data System (ADS)

Silva, Alessandro

2009-03-01

The quantum quench, i.e. a rapid change in time of a control parameter of a quantum system, is the simplest paradigm of non-equilibrium process, completely analogous to a standard thermodynamic transformation. The dynamics following a quantum quench is particularly interesting in strongly correlated quantum systems, most prominently when the quench in performed across a quantum critical point. In this talk I will present a way to characterize the physics of quantum quenches by looking at the statistics of a basic thermodynamic variable: the work done on the system by changing its parameters [1]. I will first elucidate the relation between the probability distribution of the work, quantum Jarzynski equalities, and the Loschmidt echo, a quantity that emerges usually in the context of dephasing. Using this connection, I will then characterize the statistics of the work done on a Quantum Ising chain by quenching locally or globally the transverse field. I will then show that for global quenches the presence of a quantum critical point results in singularities of the moments of the distribution, while, for local quenches starting at criticality, the probability distribution itself displays an interesting edge singularity. The results of a similar analysis for other systems will be discussed. [4pt] [1] A. Silva, Phys. Rev. Lett. 101, 120603 (2008).

Direct interaction of the major light-harvesting complex II and PsbS in nonphotochemical quenching

PubMed Central

Wilk, Laura; Grunwald, Matthias; Liao, Pen-Nan; Walla, Peter Jomo; Kühlbrandt, Werner

2013-01-01

The photosystem II (PSII) subunit S (PsbS) plays a key role in nonphotochemical quenching, a photoprotective mechanism for dissipation of excess excitation energy in plants. The precise function of PsbS in nonphotochemical quenching is unknown. By reconstituting PsbS together with the major light-harvesting complex of PSII (LHC-II) and the xanthophyll zeaxanthin (Zea) into proteoliposomes, we have tested the individual contributions of PSII complexes and Zea to chlorophyll (Chl) fluorescence quenching in a membrane environment. We demonstrate that PsbS is stable in the absence of pigments in vitro. Significant Chl fluorescence quenching of reconstituted LHC-II was observed in the presence of PsbS and Zea, although neither Zea nor PsbS alone was sufficient to induce the same quenching. Coreconstitution with PsbS resulted in the formation of LHC-II/PsbS heterodimers, indicating their direct interaction in the lipid bilayer. Two-photon excitation measurements on liposomes containing LHC-II, PsbS, and Zea showed an increase of electronic interactions between carotenoid S1 and Chl states, , that correlated directly with Chl fluorescence quenching. These findings are in agreement with a carotenoid-dependent Chl fluorescence quenching by direct interactions of LHCs of PSII with PsbS monomers. PMID:23509270

Effect of instantaneous and continuous quenches on the density of vibrational modes in model glasses

NASA Astrophysics Data System (ADS)

Lerner, Edan; Bouchbinder, Eran

2017-08-01

Computational studies of supercooled liquids often focus on various analyses of their "underlying inherent states"—the glassy configurations at zero temperature obtained by an infinitely fast (instantaneous) quench from equilibrium supercooled states. Similar protocols are also regularly employed in investigations of the unjamming transition at which the rigidity of decompressed soft-sphere packings is lost. Here we investigate the statistics and localization properties of low-frequency vibrational modes of glassy configurations obtained by such instantaneous quenches. We show that the density of vibrational modes grows as ωβ with β depending on the parent temperature T0 from which the glassy configurations were instantaneously quenched. For quenches from high temperature liquid states we find β ≈3 , whereas β appears to approach the previously observed value β =4 as T0 approaches the glass transition temperature. We discuss the consistency of our findings with the theoretical framework of the soft potential model, and contrast them with similar measurements performed on configurations obtained by continuous quenches at finite cooling rates. Our results suggest that any physical quench at rates sufficiently slower than the inverse vibrational time scale—including all physically realistic quenching rates of molecular or atomistic glasses—would result in a glass whose density of vibrational modes is universally characterized by β =4 .

Synergistic Combination of Unquenching and Plasmonic Fluorescence Enhancement in Fluorogenic Nucleic Acid Hybridization Probes.

PubMed

Vietz, Carolin; Lalkens, Birka; Acuna, Guillermo P; Tinnefeld, Philip

2017-10-11

Fluorogenic nucleic acid hybridization probes are widely used for detecting and quantifying nucleic acids. The achieved sensitivity strongly depends on the contrast between a quenched closed form and an unquenched opened form with liberated fluorescence. So far, this contrast was improved by improving the quenching efficiency of the closed form. In this study, we modularly combine these probes with optical antennas used for plasmonic fluorescence enhancement and study the effect of the nanophotonic structure on the fluorescence of the quenched and the opened form. As quenched fluorescent dyes are usually enhanced more by fluorescence enhancement, a detrimental reduction of the contrast between closed and opened form was anticipated. In contrast, we could achieve a surprising increase of the contrast with full additivity of quenching of the dark form and fluorescence enhancement of the bright form. Using single-molecule experiments, we demonstrate that the additivity of the two mechanisms depends on the perfect quenching in the quenched form, and we delineate the rules for new nucleic acid probes for enhanced contrast and absolute brightness. Fluorogenic hybridization probes optimized not only for quenching but also for the brightness of the open form might find application in nucleic acid assays with PCR avoiding detection schemes.

A new insight into the interaction of ZnO with calf thymus DNA through surface defects.

PubMed

Das, Sumita; Chatterjee, Sabyasachi; Pramanik, Srikrishna; Devi, Parukuttyamma Sujatha; Kumar, Gopinatha Suresh

2018-01-01

Experimental evidences on the binding interaction of ZnO and Calf Thymus (CT) DNA using several biophysical techniques are the centre of interest of the present study. The interaction of ZnO with CT DNA has been investigated in detail by absorption spectral study, fluorescence titration, Raman analysis, zeta potential measurement, viscometric experiment along with thermal melting study and microscopic analysis. Steady-state fluorescence study revealed the quenching (48%) of the surface defect related peak intensity of ZnO on interaction with DNA. The optimized concentration of ZnO and DNA to obtain this level of quenching has been found to be 0.049mM and 1.027μM, respectively. Additional fluorescence study with 8-hydroxy-5-quinoline (HQ) as a fluorescence probe for Zn 2+ ruled out the dissolution effect of ZnO under the experimental conditions. DNA conjugation on the surface of ZnO was also supported by Raman study. The quantitative variation in conductivity as well as electrophoretic mobility indicated significant interaction of ZnO with the DNA molecule. Circular dichroism (CD) and viscometry titrations provided clear evidence in support of the conformational retention of the DNA on interaction with ZnO. The binding interaction was found to be predominantly entropy driven in nature. The bio-physical studies presented in this paper exploring ZnO-CT DNA interaction could add a new horizon to understand the interaction between metal oxide and DNA. Copyright © 2017. Published by Elsevier B.V.

Impact melting of carbonates from the Chicxulub crater

NASA Astrophysics Data System (ADS)

Jones, A. P.; Claeys, P.; Heuschkel, S.

We have recently interpreted distinctive feathery-textured spinifex carbonate in the upper part of the Chicxulub suevite breccia as quenched carbonate melts (Jones et al. 1998); these distinctive fragments make up to 10 vol% of the breccia. Carbonate clasts and spherules occurring in the ejecta-rich basal part of the coarse clastic sequence, which marks the K/T boundary all around the Gulf of Mexico, may represent distal quenched droplets of carbonate liquids. In seeking to explain this widespread carbonate impact-melting phenomenon, we have re-examined the available experimental evidence. The important decarbonation reaction for calcite CaCO3=CaO+CO2 is inhibited by very small pressures up to temperatures >2000 K. We conclude that massive decarbonation by direct shock pressure is unlikely without attainment of temperatures >4000 K. Therefore, decarbonation generally can only occur during post-shock cooling for carbonates at low pressure (< 10 bars). We assume that post-shock cooling is quasi-thermodynamic, and provide a general P-T model for carbonate spanning 11 orders of magnitude in pressure (atmosphere to core). Subtle differences in sample preconditioning can probably explain the wildly divergent experimental shock data. A major planetary implication for the formation of the Earth's early atmosphere is that impacts on limestone would be less likely to have contributed substantial CO2 than has previously been assumed. Lastly, we note that carbonate melts at high pressures serve as excellent catalysts for diamond growth, and may have contributed to the widespread formation of some impact diamond.

Influence of repeated quenching-tempering on spheroidized carbide area in JIS SUJ2 bearing steel

NASA Astrophysics Data System (ADS)

Egawa, K.; Yoshida, I.; Yoshida, H.; Mizobe, K.; Kida, K.

2018-02-01

High-carbon high-strength JIS-SUJ2 bearing steel is mainly used for rolling contact applications which require high fatigue strength. We had applied repeated quenching which refine the prior austenite grains to this steel. In this work, we prepared JIS SUJ2 bearing steel bar specimens which were quenched three times (Q3T1) and quenched-tempered three times (QTQTQT) in order to investigate the influence of tempering before quenching on the microstructure. The specimens were etched by picral to observe the microstructure. We found that the spheroidized carbide area was important for the prior austenite grain formation.

Effect of antimony-oxide on the shielding properties of some sodium-boro-silicate glasses.

PubMed

Zoulfakar, A M; Abdel-Ghany, A M; Abou-Elnasr, T Z; Mostafa, A G; Salem, S M; El-Bahnaswy, H H

2017-09-01

Some sodium-silicate-boro-antimonate glasses having the molecular composition [(20) Na 2 O - (20) SiO 2 - (60-x) B 2 O 3 - (x) Sb 2 O 3 (where x takes the values 0, 5 … or 20)] have been prepared by the melt quenching method. The melting and annealing temperatures were 1500 and 650K respectively. The amorphous nature of the prepared samples was confirmed by using X-ray diffraction analysis. Both the experimental and empirical density and molar volume values showed gradual increase with increasing Sb 2 O 3 content. The empirical densities showed higher values than those obtained experimentally, while the empirical molar volume values appeared lower than those obtained experimentally, which confirm the amorphous nature and randomness character of the studied samples. The experimentally obtained shielding parameters were approximately coincident with those obtained theoretically by applying WinXCom program. At low gamma-ray energies (0.356 and 0.662MeV) Sb 2 O 3 has approximately no effect on the total Mass Attenuation Coefficient, while at high energies it acts to increase the total Mass Attenuation Coefficient gradually. The obtained Half Value Layer and Mean Free Path values showed gradual decrease as Sb 2 O 3 was gradually increased. Also, the Total Mass Attenuation Coefficient values obtained between about 0.8 and 3.0MeV gamma-ray energy showed a slight decrease, as gamma-ray photon energy increased. This may be due to the differences between the Attenuation Coefficients of both antimony and boron oxides at various gamma-ray photon energies. However, it can be stated that the addition of Sb 2 O 3 into sodium-boro-silicate glasses increases the gamma-ray Attenuation Coefficient and the best sample is that contains 20 mol% of Sb 2 O 3 , which is operating well at 0.356 and 0.662MeV gamma-ray. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

Measurements and Modeling of Stress in Precipitation-Hardened Aluminum Alloy AA2618 during Gleeble Interrupted Quenching and Constrained Cooling

NASA Astrophysics Data System (ADS)

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

2016-11-01

Solutionizing and quenching are the key steps in the fabrication of heat-treatable aluminum parts such as AA2618 compressor impellers for turbochargers as they highly impact the mechanical characteristics of the product. In particular, quenching induces residual stresses that can cause unacceptable distortions during machining and unfavorable stresses in service. Predicting and controlling stress generation during quenching of large AA2618 forgings are therefore of particular interest. Since possible precipitation during quenching may affect the local yield strength of the material and thus impact the level of macroscale residual stresses, consideration of this phenomenon is required. A material model accounting for precipitation in a simple but realistic way is presented. Instead of modeling 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. This material model is presented, calibrated, and validated against constrained coolings in a Gleeble blocked-jaws configuration. Applications of this model are FE computations of stress generation during quenching of large AA2618 forgings for compressor impellers.

Direct comparison of single- and multi-walled carbon nanotubes in fluorescence quenching phenomenon

NASA Astrophysics Data System (ADS)

Oura, Shusuke; Umemura, Kazuo

2018-03-01

Here, we report the fluorescence quenching ability of single-stranded DNA (ssDNA)-wrapped single- and multi-walled carbon nanotubes (ssDNA-SWNTs and ssDNA-MWNTs, respectively) using fluorescein dye-labeled ssDNA (Fluor-ssDNA). To compare the quenching abilities of SWNTs and MWNTs, we measured the quenching ratios of fluorescence emission from fluorescein when Fluor-ssDNA reacted with the hybrids of 30-mers of thymine (T30) and SWNTs or MWNTs (T30-SWNTs and T30-MWNTs, respectively). The fluorescence quenching ratios of Fluor-T30 in SWNT and MWNT samples were 28 ± 3.1 and 36 ± 2.0% relative to free fluorescein at the same concentration, respectively. On the other hand, those of Fluor-A30 with SWNT and MWNT hybrids were 11 ± 1.9 and 32 ± 1.9%, respectively. Our results suggest that although the fluorescence quenching ability of MWNT was greater than that of SWNT, SWNT quenching ratios were more sensitive to the base sequences of Fluor-ssDNA.

Determination of Wetting Behavior, Spread Activation Energy, and Quench Severity of Bioquenchants

NASA Astrophysics Data System (ADS)

Prabhu, K. Narayan; Fernandes, Peter

2007-08-01

An investigation was conducted to study the suitability of vegetable oils such as sunflower, coconut, groundnut, castor, cashewnut shell (CNS), and palm oils as quench media (bioquenchants) for industrial heat treatment by assessing their wetting behavior and severity of quenching. The relaxation of contact angle was sharp during the initial stages, and it became gradual as the system approached equilibrium. The equilibrium contact angle decreased with increase in the temperature of the substrate and decrease in the viscosity of the quench medium. A comparison of the relaxation of the contact angle at various temperatures indicated the significant difference in spreading of oils having varying viscosity. The spread activation energy was determined using the Arrhenius type of equation. Oils with higher viscosity resulted in lower cooling rates. The quench severity of various oil media was determined by estimating heat-transfer coefficients using the lumped capacitance method. Activation energy for spreading determined using the wetting behavior of oils at various temperatures was in good agreement with the severity of quenching assessed by cooling curve analysis. A high quench severity is associated with oils having low spread activation energy.

Freeze-quench (57)Fe-Mössbauer spectroscopy: trapping reactive intermediates.

PubMed

Krebs, Carsten; Bollinger, J Martin

2009-01-01

(57)Fe-Mössbauer spectroscopy is a method that probes transitions between the nuclear ground state (I=1/2) and the first nuclear excited state (I=3/2). This technique provides detailed information about the chemical environment and electronic structure of iron. Therefore, it has played an important role in studies of the numerous iron-containing proteins and enzymes. In conjunction with the freeze-quench method, (57)Fe-Mössbauer spectroscopy allows for monitoring changes of the iron site(s) during a biochemical reaction. This approach is particularly powerful for detection and characterization of reactive intermediates. Comparison of experimentally determined Mössbauer parameters to those predicted by density functional theory for hypothetical model structures can then provide detailed insight into the structures of reactive intermediates. We have recently used this methodology to study the reactions of various mononuclear non-heme-iron enzymes by trapping and characterizing several Fe(IV)-oxo reaction intermediates. In this article, we summarize these findings and demonstrate the potential of the method. © Springer Science+Business Media B.V. 2009

Photophysics and photochemistry of dyes bound to human serum albumin are determined by the dye localization.

PubMed

Alarcón, Emilio; Edwards, Ana Maria; Aspee, Alexis; Moran, Faustino E; Borsarelli, Claudio D; Lissi, Eduardo A; Gonzalez-Nilo, Danilo; Poblete, Horacio; Scaiano, J C

2010-01-01

The photophysics and photochemistry of rose bengal (RB) and methylene blue (MB) bound to human serum albumin (HSA) have been investigated under a variety of experimental conditions. Distribution of the dyes between the external solvent and the protein has been estimated by physical separation and fluorescence measurements. The main localization of protein-bound dye molecules was estimated by the intrinsic fluorescence quenching, displacement of fluorescent probes bound to specific protein sites, and by docking modelling. All the data indicate that, at low occupation numbers, RB binds strongly to the HSA site I, while MB localizes predominantly in the protein binding site II. This different localization explains the observed differences in the dyes' photochemical behaviour. In particular, the environment provided by site I is less polar and considerably less accessible to oxygen. The localization of RB in site I also leads to an efficient quenching of the intrinsic protein fluorescence (ascribed to the nearby Trp residue) and the generation of intra-protein singlet oxygen, whose behaviour is different to that observed in the external solvent or when it is generated by bound MB.

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.

Light quark masses with overlap fermions in quenched QCD

NASA Astrophysics Data System (ADS)

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

2001-12-01

We present the results of a computation of the sum of the strange and average up-down quark masses with overlap fermions in the quenched approximation. Since the overlap regularization preserves chiral symmetry at finite cutoff and volume, no additive quark mass renormalization is required and the results are O(a) improved. Our simulations are performed at β=6.0 and volume V=163×32, which correspond to a lattice cutoff of ~2 GeV and to an extension of ~1.4 fm. The logarithmically divergent renormalization constant has been computed nonperturbatively in the RI/MOM scheme. By using the K-meson mass as experimental input, we obtain (ms+m)RI(2 GeV)=120(7)(21) MeV, which corresponds to mMS¯s(2 GeV)=102(6)(18) MeV if continuum perturbation theory and χPT are used. By using the Gell-Mann-Oakes-Renner relation we also obtain <ψ¯ψ>MS¯(2 GeV)/Nf =-0.0190(11)(33) GeV3=-[267(5)(15) MeV]3, where the errors are statistical and systematic respectively.

One-pot synthesis via 1, 3-dipolar cycloaddition reaction to piperazinyl-quinolinyl dispiro heterocyclic derivatives and spectrofluorometric and molecular docking studies on their binding with human serum albumin

NASA Astrophysics Data System (ADS)

Murugesan, Arul; Gengan, Robert Moonsamy; Rajamanikandan, Ramar; Ilanchelian, Malaichamy

2017-12-01

A series of novel dispiro piperazinyl-quinolinyl-thioxothiazolidin-2, 4-dione derivatives were synthesised and characterised by FT-IR 1H, 13C, 2D NMR and HRMS spectroscopic techniques. A representative compound 1'-(2-(4-methylpiperazin-1-yl)quinolin-3-yl)-2″-thioxo-5‧,6‧,7‧,7a'-tetrahydro-1‧H,2H-dispiro[acenaphthylene-1,3‧-pyrrolizine-2‧,5″-thiazolidine]-2,4″-dione was studied for its binding ability with human serum albumin (HSA) using the fluorescence quench titration method. Addition of the compound to HSA produced slight fluorescence quenching and red shift. The free energy change for the complexation process was evaluated as -29.98 kJ mol-1 thereby indicating a spontaneous and highly favourable reaction. Molecular docking analyses revealed the binding as -20.79 kJ mol-1 which was analogous with the experimental value obtained from emission data. It was concluded that TYR-263 is the moiety responsible for the binding in the complex.

Recyclable fluorescent gold nanocluster membrane for visual sensing of copper(II) ion in aqueous solution.

PubMed

Lin, Zhijin; Luo, Fenqiang; Dong, Tongqing; Zheng, Liyan; Wang, Yaxian; Chi, Yuwu; Chen, Guonan

2012-05-21

Recently, metal-selective fluorescent chemosensors have attracted intense attention for their simple and real-time tracking of metal ions in environmental samples. However, most of the existing fluorescent sensors are one-off sensors and thus suffer from large amount of reagent consumption, significant experimental cost and raising the risk of environmental pollution. In this paper, we developed a green (low reagent consumption, low-toxicity reagent use), recyclable, and visual sensor for Cu(2+) in aqueous solution by using a fluorescent gold nanoclusters membrane (FGM) as the sensing unit, basing on our findings on gold nanoclusters (Au NCs) that the bovine serum albumin (BSA)-coated Au NCs exhibit excellent membrane-forming ability under the isoelectric point of BSA, and thus enable us to obtain a new type of sensing membrane (i.e. FGM) by denaturing Au NCs; the fluorescence of FGM can be significantly quenched by Cu(2+) ion, and the quenched fluorescence can be totally recovered by histidine; the as-prepared FGM is very stable and recyclable, which makes it an ideal sensing material.

Probing the binding of an endocrine disrupting compound-Bisphenol F to human serum albumin: insights into the interactions of harmful chemicals with functional biomacromolecules.

PubMed

Pan, Fang; Xu, Tianci; Yang, Lijun; Jiang, Xiaoqing; Zhang, Lei

2014-11-11

Bisphenol F (BPF) as an endocrine disrupting compounds (EDCs) pollutant in the environment poses a great threat to human health. To evaluate the toxicity of BPF at the protein level, the effects of BPF on human serum albumin (HSA) were investigated at three temperatures 283, 298, and 308 K by multiple spectroscopic techniques. The experimental results showed that BPF effectively quenched the intrinsic fluorescence of HSA via static quenching. The number of binding sites, the binding constant, the thermodynamic parameters and the binding subdomain were measured, and indicated that BPF could spontaneously bind with HSA on subdomain IIA through H-bond and van der Waals interactions. Furthermore, the conformation of HSA was demonstrably changed in the presence of BPF. The work provides accurate and full basic data for clarifying the binding mechanisms of BPF with HSA in vivo and is helpful for understanding its effect on protein function during its transportation and distribution in blood. Copyright © 2014 Elsevier B.V. All rights reserved.

Integrated modeling and heat treatment simulation of austempered ductile iron

NASA Astrophysics Data System (ADS)

Hepp, E.; Hurevich, V.; Schäfer, W.

2012-07-01

The integrated modeling and simulation of the casting and heat treatment processes for producing austempered ductile iron (ADI) castings is presented. The focus is on describing different models to simulate the austenitization, quenching and austempering steps during ADI heat treatment. The starting point for the heat treatment simulation is the simulated microstructure after solidification and cooling. The austenitization model considers the transformation of the initial ferrite-pearlite matrix into austenite as well as the dissolution of graphite in austenite to attain a uniform carbon distribution. The quenching model is based on measured CCT diagrams. Measurements have been carried out to obtain these diagrams for different alloys with varying Cu, Ni and Mo contents. The austempering model includes nucleation and growth kinetics of the ADI matrix. The model of ADI nucleation is based on experimental measurements made for varied Cu, Ni, Mo contents and austempering temperatures. The ADI kinetic model uses a diffusion controlled approach to model the growth. The models have been integrated in a tool for casting process simulation. Results are shown for the optimization of the heat treatment process of a planetary carrier casting.

Exciton Emission Intensity Modulation of Monolayer MoS2 via Au Plasmon Coupling

PubMed Central

Mukherjee, B.; Kaushik, N.; Tripathi, Ravi P. N.; Joseph, A. M.; Mohapatra, P. K.; Dhar, S.; Singh, B. P.; Kumar, G. V. Pavan; Simsek, E.; Lodha, S.

2017-01-01

Modulation of photoluminescence of atomically thin transition metal dichalcogenide two-dimensional materials is critical for their integration in optoelectronic and photonic device applications. By coupling with different plasmonic array geometries, we have shown that the photoluminescence intensity can be enhanced and quenched in comparison with pristine monolayer MoS2. The enhanced exciton emission intensity can be further tuned by varying the angle of polarized incident excitation. Through controlled variation of the structural parameters of the plasmonic array in our experiment, we demonstrate modulation of the photoluminescence intensity from nearly fourfold quenching to approximately threefold enhancement. Our data indicates that the plasmonic resonance couples to optical fields at both, excitation and emission bands, and increases the spontaneous emission rate in a double spacing plasmonic array structure as compared with an equal spacing array structure. Furthermore our experimental results are supported by numerical as well as full electromagnetic wave simulations. This study can facilitate the incorporation of plasmon-enhanced transition metal dichalcogenide structures in photodetector, sensor and light emitter applications. PMID:28134260

Quenched dynamics and spin-charge separation in an interacting topological lattice

NASA Astrophysics Data System (ADS)

Barbiero, L.; Santos, L.; Goldman, N.

2018-05-01

We analyze the static and dynamical properties of a one-dimensional topological lattice, the fermionic Su-Schrieffer-Heeger model, in the presence of on-site interactions. Based on a study of charge and spin correlation functions, we elucidate the nature of the topological edge modes, which, depending on the sign of the interactions, either display particles of opposite spin on opposite edges, or a pair and a holon. This study of correlation functions also highlights the strong entanglement that exists between the opposite edges of the system. This last feature has remarkable consequences upon subjecting the system to a quench, where an instantaneous edge-to-edge signal appears in the correlation functions characterizing the edge modes. Besides, other correlation functions are shown to propagate in the bulk according to the light cone imposed by the Lieb-Robinson bound. Our study reveals how one-dimensional lattices exhibiting entangled topological edge modes allow for a nontrivial correlation spreading, while providing an accessible platform to detect spin-charge separation using state-of-the-art experimental techniques.

FAGE measurements of tropospheric HO with measurements and model of interferences

NASA Technical Reports Server (NTRS)

Hard, T. M.; Mehrabzadeh, A. A.; Chan, C. Y.; O'Brien, R. J.

1992-01-01

Ambient HO measurements by low-pressure laser-excited fluorescence with chemical modulation, and supporting ozone and water-vapor data, are presented for periods in May and August 1987. The observed peak daytime ambient HO concentrations are in the range (2.5 to 8) x 10 exp 6 molecules/cu cm and show small negative offsets due to photochemical interference. Direct measurements of the interference at fixed (O3) give the dependence on ambient (H2O) and on the modulating reagent (isobutane). At ambient (O3) = 30 ppb and 10 torr H2O, with excitation and detection at a total pressure of 4 torr, the net interference is equal to (HO) = -1.3 x 10 exp 6 molecules/cu cm. Production of HO by the reaction of isobutane with O(1D) accounts for the negative interference. Quenching of HO fluorescence by the modulating reagent contributes a smaller positive term to the interference; kinetic measurements of the quenching rate coefficient are reported. The experimental interference results are compared with a detailed kinetic model of HO production, excitation, relaxation, and detection; reasonable agreement is found.

Detection of Thrombin Based on Fluorescence Energy Transfer between Semiconducting Polymer Dots and BHQ-Labelled Aptamers.

PubMed

Liu, Yizhang; Jiang, Xuekai; Cao, Wenfeng; Sun, Junyong; Gao, Feng

2018-02-14

Carboxyl-functionalized semiconducting polymer dots (Pdots) were synthesized as an energy donor by the nanoprecipitation method. A black hole quenching dye (BHQ-labelled thrombin aptamers) was used as the energy acceptor, and fluorescence resonance energy transfer between the aptamers and Pdots was used for fluorescence quenching of the Pdots. The addition of thrombin restored the fluorescence intensity. Under the optimized experimental conditions, the fluorescence of the system was restored to the maximum when the concentration of thrombin reached 130 nM, with a linear range of 0-50 nM (R² = 0.990) and a detection limit of 0.33 nM. This sensor was less disturbed by impurities, showing good specificity and signal response to thrombin, with good application in actual samples. The detection of human serum showed good linearity in the range of 0-30 nM (R² = 0.997), with a detection limit of 0.56 nM and a recovery rate of 96.2-104.1%, indicating that this fluorescence sensor can be used for the detection of thrombin content in human serum.

Binding interaction of atorvastatin with bovine serum albumin: Spectroscopic methods and molecular docking

NASA Astrophysics Data System (ADS)

Wang, Qi; Huang, Chuan-ren; Jiang, Min; Zhu, Ying-yao; Wang, Jing; Chen, Jun; Shi, Jie-hua

2016-03-01

The interaction of atorvastatin with bovine serum albumin (BSA) was investigated using multi-spectroscopic methods and molecular docking technique for providing important insight into further elucidating the store and transport process of atorvastatin in the body and the mechanism of action and pharmacokinetics. The experimental results revealed that the fluorescence quenching mechanism of BSA induced atorvastatin was a combined dynamic and static quenching. The binding constant and number of binding site of atorvastatin with BSA under simulated physiological conditions (pH = 7.4) were 1.41 × 105 M- 1 and about 1 at 310 K, respectively. The values of the enthalpic change (ΔH0), entropic change (ΔS0) and Gibbs free energy (ΔG0) in the binding process of atorvastatin with BSA at 310 K were negative, suggesting that the binding process of atorvastatin and BSA was spontaneous and the main interaction forces were van der Waals force and hydrogen bonding interaction. Moreover, atorvastatin was bound into the subdomain IIA (site I) of BSA, resulting in a slight change of the conformation of BSA.